1.
Eker, Johan
(författare)
Flexible Embedded Control Systems : Design and Implementation
1999
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Embedded control system design is a complex and error prone task, and there is a great need for better development tools. Today most real-time control systems are static systems, designed in an ad-hoc fashion. A more interactive way of working would give shorter development times, reduced costs for testing, and safer, more robust systems. This thesis presents an interactive prototyping tool called Pålsjö and a controller description language called PAL. Pålsjö allows the user to interactively configure a system. Control systems are defined using block diagrams and blocks may be added and replaced on-line. The static nature of most embedded control systems makes them very sensitive to changes in the hardware or software configuration. There is rarely any interaction between the control loops and the underlying real-time kernel or operating system. From a control engineering perspective, the system executes in open loop. In this thesis, the possibility of using feedback in the scheduling of real-time tasks is explored. This is called feedback scheduling. An algorithm for selecting sampling rates based on the linear quadratic cost is presented. The dependence of the cost function on the sampling interval is investigated. The influence on the control performance from the interaction between the control tasks running concurrently in the real-time kernel is studied. A simulation toolbox for this is presented in the thesis. Designing flexible control systems is much simplified given the proper language support. Therefore the PAL language concept is extended into a new proposed language Friend, which is designed to support the development of flexible embedded control systems through the use of contracts.
2.
Guimaraes, Tor, et al.
(författare)
Empirically testing the impact of manufacturing system complexity on performance
1999
Ingår i: International Journal of Operations and Production Management. - : Emerald. - 1758-6593 .- 0144-3577. ; 19:12, s. 1254-1269
Tidskriftsartikel (refereegranskat) abstract
As the increase in manufacturing competitiveness forces organizations to use more sophisticated and complex software, system performance depends on clever systems design, efficient planning and scheduling of the related processes. For these advanced manufacturing systems the dependence on human competence is greater. However, previous studies indicate that the human aspects for successfully implementing such systems have been neglected. The objective here is to test the hypotheses that system complexity is inversely related to performance, and that training of system operators, and the quality of the man/machine interface reduces the negative impact of system complexity. A sample of discreet manufacturing systems from 128 organizations was used to test these hypotheses empirically. Moderated multivariate regression indicates that man/machine interfaces are significant contributors to reducing the negative effect of systems complexity. With a lower level of significance, operator training has a similar impact. For complex manufacturing systems software, it behoves managers to insure that the man/machine interface provides the desirable features outlined in this study.
3.
Höst, Stefan
(författare)
On Woven Convolutional Codes
1999
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Concatenation of several conventional convolutional encoders is a both powerful and practical method to obtain encoding schemes that are attractive for use in communication systems where very low error probabilities are needed. This thesis is devoted to woven convolutional codes, a construction where the constituent codes are woven together in a manner that resembles the structure of a fabric. A family of active distance measures for convolutional codes is defined. It is shown that the error correcting capability of a convolutional code is determined by the active distances. Lower bounds on the active distances are derived for the ensemble of periodically time-varying convolutional codes. The simplest construction of serially concatenated convolutional codes is considered, viz., a direct cascade of two convolutional encoders. Important structural properties for the cascaded convolutional encoder is shown both for the case of matched and for unmatched rates. Several interesting examples of cascaded convolutional codes are considered and examined. Lower bounds on the active distances and the free distance are derived for the ensemble of periodically time-varying cascaded convolutional codes. Woven convolutional codes can be viewed as a generalization of cascaded convolutional codes. The general construction is called the twill and it is described together with two important special cases, viz., woven convolutional codes with outer and inner warp. The woven convolutional encoder inherits many of its structural properties, such as minimality, from the constituent encoders. Distance properties for the constructions are examined and upper and lower bounds on the free distance are derived. Decoding of woven convolutional codes should be performed iteratively and, for that reason, the BCJR algorithm is rederived. Simulation results show that woven convolutional codes are attractive alternatives to the celebrated Turbo codes. Finally, a review of bounds, such as error exponents and bounds on the active distances, is given for woven convolutional codes.
4.
Johansson, Mikael
(författare)
Piecewise Linear Control Systems
1999
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
This thesis treats analysis and design of piecewise linear control systems. Piecewise linear systems capture many of the most common nonlinearities in engineering systems, and they can also be used for approximation of other nonlinear systems. Several aspects of linear systems with quadratic constraints are generalized to piecewise linear systems with piecewise quadratic constraints. It is shown how uncertainty models for linear systems can be extended to piecewise linear systems, and how these extensions give insight into the classical trade-offs between fidelity and complexity of a model. Stability of piecewise linear systems is investigated using piecewise quadratic Lyapunov functions. Piecewise quadratic Lyapunov functions are much more powerful than the commonly used quadratic Lyapunov functions. It is shown how piecewise quadratic Lyapunov functions can be computed via convex optimization in terms of linear matrix inequalities. The computations are based on a compact parameterization of continuous piecewise quadratic functions and conditional analysis using the S-procedure. A unifying framework for computation of a variety of Lyapunov functions via convex optimization is established based on this parameterization. Systems with attractive sliding modes and systems with bounded regions of attraction are also treated. Dissipativity analysis and optimal control problems with piecewise quadratic cost functions are solved via convex optimization. The basic results are extended to fuzzy systems, hybrid systems and smooth nonlinear systems. It is shown how Lyapunov functions with a discontinuous dependence on the discrete state can be computed via convex optimization. An automated procedure for increasing the flexibility of the Lyapunov function candidate is suggested based on linear programming duality. A Matlab toolbox that implements several of the results derived in the thesis is presented.
5.
Johnsson, Charlotta
(författare)
A Graphical Language for Batch Control
1999
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
In this thesis a graphical language for sequential control is presented and its application to batch control is examined and discussed. The name of the language is Grafchart. Its main feature is that it makes it possible to express complicated control problems in a compact and intuitive manner.Grafchart exists in two versions; a basic version and a high-level version. The basic version was available when the work presented in this thesis started. The basic version of Grafchart is mainly based on Grafcet, i.e., it has a clear and intuitive syntax. In addition to this it has support for parameterization and methods and message passing as well as extended facilities for exception handling. The high-level version of Grafchart takes the concepts of the basic version one step further. The concepts of object tokens and multi-dimensional charts are introduced. These features are inspired by high-level Petri nets and constructs from object-oriented programming languages.The main application area of Grafchart is batch control. In the thesis it is shown how Grafchart can be used for recipe structuring and recipe analysis. By using the features of Grafchart in various ways, recipes can be given different structures with different advantages and disadvantages. All structures comply with the international batch standard IEC 61512 (also refered to as ISA S88.01). To test and evaluate the different recipe structures, a real-time batch plant simulation platform was used. The batch recipe structures can be combined with resource allocation and a visualization of the allocation is thereby achieved. By transforming the recipes into an equivalent Petri net structure, formal analysis methods that exist for Petri nets can be used to look for possible deadlock situations.Several commercial batch control systems exist today. They all have a similar approach to recipe structuring, resource allocation and user presentation. The advantages of using Grafchart compared to some of these systems, regarding these features are presented in the thesis. A toolbox implementation of Grafchart exists. It is implemented in G2, an object-oriented programming environment. G2 is also an industrial environment, this makes the toolbox and the results of this thesis directly usable in industry.
6.
Moore, Philip, et al.
(författare)
Intelligent semi-autonomous vehicles in materials handling
1999
Ingår i: Mechatronics (Oxford). - : Elsevier. - 0957-4158 .- 1873-4006. ; 9:7, s. 881-892
Tidskriftsartikel (refereegranskat) abstract
An increase in functionality of semi-autonomous vehicles (SAV) through the implementation of intelligent distributed control and smart sensing techniques is presented. In combination with a modular design approach, this facilitates system modification and improvement, combined with faster customisation of the platform. A distributed and reactive behavioural control architecture is used to realise local autonomous navigation capabilities; improved operator interaction; self protection and safer operation. A virtual engineering environment based on a computer-aided-graphics platform is used (1) for modelling the vehicle and the environment in which it can operate; (2) developing pre-emptive learning and training of responses/behaviours, and (3) for evaluation of vehicle functionality as part of an integrated materials handling system.
7.
Nasri, Hamid
(författare)
Modeling and Requirements of the Automated Deburring Process
1999
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
An increasing number of robots have been used for the finishing of castings during recent years. This is mainly due to developments to overcome problems that restricted their use during the past decade. The major difficulties have been the need to control reaction forces during metal removing by grinding operations and the lack of tools designed specially for robots. The elimination of these two problems, makes robot cells with high efficiency and good quality products possible. This thesis focuses on requirements of automated deburring process and models necessary to control the process. There may still exist problems that should be solved before these robot cells become feasible. These problems can be divided into two groups. The first group consists of the problems related to the shape of the workpiece. Grinding and deburring is used in a vast domain of products with different types of materials that can take practically any shape. This requires a rather long programming time. Therefore developing methods for simplifying and decreasing the required time for programming jobs are desirable. Improved programming methods increase the flexibility and make the automation economically viable even for small batch production. Improvement of off-line programming software and availability of efficient vision systems has been a great step to achieve this. The second group of problems is related to choice of the grinding methods and equipment. The possibility of choosing among the different available tools such as grinding discs or wheels and rotary files with different sizes and hardness necessitates enough knowledge about the process to find the best solution. This directly affects the production's economics and products' quality. Investigations show that developing a process model for robotic grinding is both possible and desirable. The process model is the basis for selection of the suitable grinding machine (power and speed) and disc (grit size, thickness and hardness). The process model also can be used for selecting an optimized operating point, i.e. establishing the relationships between material removal rate, wheel wear and the process operating data, i.e. feed rate and cut depth.
8.
Nilsson, Klas, et al.
(författare)
Integrated Architecture for Industrial Robot Programming and Control
1999
Ingår i: Robotics and Autonomous Systems. - 0921-8890. ; 29:4, s. 205-226
Tidskriftsartikel (refereegranskat) abstract
As robot control systems are traditionally closed, it is difficult to add supplementary intelligence. Accordingly, as based on a new notion of user views, a layered system architecture is proposed. Bearing in mind such industrial demands as computing efficiency and simple factory-floor operation, the control layers are parameterized by means of functional operators consisting of pieces of compiled code that can be passed as parameters between the layers. The required interplay between application-specific programs and built-in motion control is thereby efficiently accomplished. The results from experimental evaluation and several case studies suggest the architecture to be very useful also in an industrial context.
9.
Pedersen, Lars Malcolm
(författare)
Modeling and Control of Plate Mill Processes
1999
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
In this thesis two processes have been modeled and controlled, namely the plate thickness control and the slab temperature control. The classical solution for the thickness control problem can't handle asymmetric hardness variations and the estimation of the controlled output introduces stability problems. A nonlinear multivariable model for the thickness control system is derived. The parameters of the model for the rolling mill are identified using data from The Danish Steel Works Ltd. and the model is used for designing a nonlinear multivariable thickness control algorithm. The algorithm is evaluated using computer simulations and the new controller is able to handle the asymmetric case and gives a more accurate thickness control compared to the existing control system. The new control strategy is also found to be stable. The task of the slab temperature controller is to ensure a high furnace throughput, and a proper heating quality while minimizing the energy consumption. Models for the slab and furnace temperatures are identified using data collected during normal production at The Danish Steel Works Ltd. A new way of obtaining parameters for the existing slab temperature control system is described. Furthermore, a nonlinear controller is designed which it is shown to be is globally asymptotically stable. The performance of the linear and nonlinear controller are compared using computer simulations which show that the performance of the nonlinear controller is superior to the performance of the linear controller. The linear slab temperature controller design has been implemented in the slab temperature control system at The Danish Steel Works Ltd. The experimental results indicate that the new controller parameters have lead to a 10% increase in furnace capacity, with unchanged heating quality. Data from the reheat furnace no. 2 indicate that the energy consumption has not been increased by the adjustments.
10.
Robertsson, Anders
(författare)
On Observer-Based Control of Nonlinear Systems
1999
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Filtering and reconstruction of signals play a fundamental role in modern signal processing, telecommunications, and control theory and are used in numerous applications. The feedback principle is an important concept in control theory. Many different control strategies are based on the assumption that all internal states of the control object are available for feedback. In most cases, however, only a few of the states or some functions of the states can be measured. This circumstance raises the need for techniques, which makes it possible not only to estimate states, but also to derive control laws that guarantee stability when using the estimated states instead of the true ones. For linear systems, the separation principle assures stability for the use of converging state estimates in a stabilizing state feedback control law. In general, however, the combination of separately designed state observers and state feedback controllers does not preserve performance, robustness, or even stability of each of the separate designs. In this thesis, the problems of observer design and observer-based control for nonlinear systems are addressed. The deterministic continuous-time systems have been in focus. Stability analysis related to the Positive Real Lemma with relevance for output feedback control is presented. Separation results for a class of nonholonomic nonlinear systems, where the combination of independently designed observers and state-feedback controllers assures stability in the output tracking problem are shown. In addition, a generalization to the observer-backstepping method where the controller is designed with respect to estimated states, taking into account the effects of the estimation errors, is presented. Velocity observers with application to ship dynamics and mechanical manipulators are also presented.
11.
Shanahan, Murray
(författare)
A Logical Account of the Common Sense Informatic Situation for a Mobile Robot
1999
Rapport (övrigt vetenskapligt/konstnärligt) abstract
Any model of the world a robot constructs on the basis of its sensor data is necessarily both incomplete, due to the robot's limited window on the world, and uncertain, due to sensor and motor noise. This paper proposes a logic-based framework in which such models are constructed through an abductive process whereby sensor data is explained by hypothesising the existence, locations, and shapes of objects. Symbols appearing in the resulting explanations acquire meaning through the theory, and yet are grounded by the robot's interaction with the world. The proposed framework draws on existing logic-based formalisms for representing action, continuous change, space, and shape, but a novel solution to the frame problem is employed. Noise is treated as a kind of non-determinism, and is dealt with by a consistency-based form of abduction.
12.
Suc, Dorian, et al.
(författare)
Symbolic and qualitative reconstruction of control skill
1999
Rapport (övrigt vetenskapligt/konstnärligt) abstract
Controlling a complex dynamic system, such as a plane or a crane, usually requires a skilled operator. Such a control skill is typically hard to reconstruct through introspection. Therefore an attractive approach to the reconstruction of control skill involves machine learning from operators' control traces, also known as behavioural cloning. In the most common approach to behavioural cloning, a controller is induced as a direct mapping from system states to actions. Unfortunately, such controllers usually lack typical elements of human control strategies, such as subgoals or desired trajectory and do not replicate the robustness of the human control skill. In this paper we investigate a novel approach. We apply the GoldHorn program to induce from the control traces a set of symbolic constraints. Those constraints describe the operator's generalized trajectory and are then used together with locally weighted regression model to determine the next action. Using the crane problem in a case study, this approach showed significant improvements both in terms of control performance and transparency of induced clones. Moreover, generalizing the trajectory into qualitative strategy shows the potentials of such an approach.
13.
Åberg, Jan
(författare)
A Universal Source Coding Perspective on PPM
1999
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
The PPM (Prediction by Partial Matching) family of text compression algorithms has several members that have shown to be very efficient in practice. This thesis treats PPM algorithms from an information-theoretical point of view, based on results and methods from universal source coding theory. A number of source classes for modeling text-like data are developed, that are distinguished both by structural properties and by restrictions imposed on the possible combinations of parameter values. Two subproblems of PPM are studied in detail; the problem of sequential multi-alphabet coding, i.e., coding for memoryless sources with unknown alphabet, and the problem of coding for memoryless sources with side information in the form of observations from a source with similar parameters. For the multi-alphabet coding problem, several codes are presented, together with a sufficient condition for asymptotic optimality, which is satified by some of the introduced codes. Furthermore, the natural law of succession, a known solution of the underlying estimation problem, is analysed from the aspect of coding, and a method is given for calculation of the coding probabilities for a known multi-alphabet code. A code using side information from a similar source is presented and analysed, and is proved to asymptotically outperform codes not using side information if the divergence between the two sources is small. Based on the above results, modified PPM algorithms are proposed, and methods are developed for estimation of code parameters during encoding. It is experimentally verified that the introduced modifications improve the compression rate of PPM on two standard sets of test data. Several known PPM versions are shown to be characterizable in terms of the introduced source classes. The combination of PPM and MDL (minimum description length) model class estimation is investigated. Codes using this combination of estimation techniques are given for the different source structures introduced for text-like data, and the modified PPM is shown experimentally to yield an improvement when combined with MDL estimation as well.
14.
Åkesson, Mats
(författare)
Probing Control of Glucose Feeding in Escherichia coli Cultivations
1999
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Production of many proteins can today be made using genetically modified organisms. One of the most frequently used host organisms is the bacterium Escherichia coli. A difficulty encountered in cultivations of E. coli is the accumulation of the metabolic by-product acetate which inhibits cell growth and production of a desired protein. Formation of acetate occurs under anaerobic conditions but also in situations with excess of the carbon/energy source that usually is glucose. In fed-batch processes the glucose feed rate can be manipulated to avoid acetate formation, but most feeding strategies require considerable process knowledge to handle process variations. On-line measurements for the relevant process variables are far from being standard which complicates the realization of strategies based on feedback control. This thesis presents a glucose feeding strategy for E. coli cultivations that avoids acetate formation in spite of process variations and without prior knowledge of the particular strain and product. The key idea is to exploit a characteristic saturation in the cellular respiration at the onset of acetate formation. By superimposing short pulses in the glucose feed rate, on-line detection of acetate formation can be made using a standard dissolved oxygen sensor. This information is used in a feedback algorithm that adjusts the feed rate to avoid acetate formation while maintaining a high glucose supply. The feed rate is also restricted to ensure aerobic conditions when the maximum oxygen transfer capacity to the culture is reached. The feasibility is demonstrated by simulations as well as laboratory-scale experiments with several E. coli strains under various operating conditions. Tuning rules that assume a minimum of process specific information are derived and a stability analysis is given. The feeding strategy relies on good control of the dissolved oxygen concentration. Variations in the oxygen dynamics during a fed-batch cultivation often cause tuning problems when using a controller with fixed parameters. A control approach based on gain scheduling from the stirrer speed is suggested.
15.
Baerveldt, Albert-Jan, et al.
(författare)
A low-cost colour vision-system for robot design competitions
1998
Ingår i: Mechatronics '98. - Oxford : Pergamon Press. - 0080433391 ; , s. 595-600
Konferensbidrag (refereegranskat) abstract
In this paper we present a low-cost colour vision system mainly intended for robot design competitions, which nowadays is a popular, project-oriented, way of teaching mechatronics in engineering curriculums. The estimated cost is about 450 dollar inclusive colour camera and the system is small enough to be carried on-board relative small mobile robots. The system is build around a signal processor TMS C31. We also present and discuss the experiences made with the system in our robot design competition.
16.
Baerveldt, Albert-Jan, et al.
(författare)
Visual guidance of mobile robots using a neural network
1998
Ingår i: Mechatronics '98. - Oxford : Pergamon Press. - 0080433391 ; , s. 427-431
Konferensbidrag (refereegranskat) abstract
In this paper we present a self-learning method for low-level navigation for autonomous mobile robots, based on a neural network. Both corridor following and obstacle avoidance in indoor environments are successfully managed by the same network. Raw gray scale images of size 32 by 23 pixels are processed one by one by a feed forward neural network. The output signals of the network represent the appropriate steering actions of the robot.
17.
Baral, Chitta, et al.
(författare)
Relating Theories of Actions and Reactive Control
1998
Rapport (övrigt vetenskapligt/konstnärligt) abstract
In this paper we give a formal characterization of reactive control using action theories. In the process we formalize the notion of a reactive control program being correct with respect to a given goal, a set of initial states, and action theories about the agent/robot and about the exogenous actions. We give sufficiency conditions that guarantee correctness and use it to give an automatic method for constructing provenly correct control modules. We then extend our approach to action theories and control modules that have specialized sensing actions and that encode conditional plans. Finally we briefly relate our theory with the implementation of our mobile robot Diablo, which successfully competed in AAAI 96 and 97 mobile robot contests.
18.
Beetz, Michael, et al.
(författare)
Causal Models of Mobile Service Robot Behavior
1998
Rapport (övrigt vetenskapligt/konstnärligt) abstract
Temporal projection, the process of predicting what will happen when a robot executes its plan, is essential for autonomous service robots to successfully plan their missions. This paper describes a causal model of the behavior exhibited by the mobile robot RHINO when running concurrent reactive plans for performing office delivery jobs. The model represents aspects of robot behavior that cannot be represented by most action models used in AI planning: it represents the temporal structure of continuous control processes, several modes of their interferences, and various kinds of uncertainty. This enhanced expressiveness enables XFRM, a robot planning system, to predict, and therefore forestall, various kinds of behavior flaws including missed deadlines whilst exploiting incidental opportunities. The proposed causal model is experimentally validated using the robot and its simulator.
19.
Karlsson, Nils
(författare)
A Measurement Approach to some Robot Related Issues : Robot Safety, Robot Control Tool and Robot Object Recognition
1998
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
The research of the measurement group at Linköping university has for some time been focused on the role of measurements in robotics. The main objective of the group's research work has been to provide the robot with sensor information in order to increase its autonomy.In this work I have studied problematic aspects of robot use that are related to robot safety as seen from the measurement technology point of view. The work can be divided into three subparts:• a sensor for person presence detection• a tool for robot control with built in emergency stop• object recognition, a requirement for increased autonomy that can decrease human presence close to the robot.In robot safety the aim was to develop a man-detecting sensor that could be used for safety purposes. The efforts were concentrated upon a capacitive sensor for the following reasons:• man's electrical characteristics differ strongly from those of the air forced out of its place by the human body• man can not change its electrical characteristics.Both model calculations and practical tests have been made. Persons are detected as intended.Industrial robots are equipped with a teach pendant, a hand held control device. It is connected to the control system of the robot and is used for work in close interaction with the robot. Work close to the robot might for instance be necessary during program verification or adjustments. It is important for a person, physically close to the robot, to be able to change command or initiate an emergency stop rapidly and easily. To that aim a user-friendly control tool with a built-in emergency stop is proposed. The tool is based on a glove that measures the finger flexions. The finger flexions form patterns that correspond to different commands. The commands are recognised by methods based on fuzzy principles. The glove is tested on gestures inspired by the manual alphabet used by deaf people. All gestures/commands were correctly recognised.In the sensor system used by the measurement group a 2-D vision system is used for the localisation and recognition of different work pieces. This system does not in all cases provide the 3-D information needed, e. g. whether an object is a cylinder or a cube. A two-camera system or special illumination techniques can provide the information. A very simple laser scanner provides however enough information for the detection, i. e. gives unique signatures for differently shaped objects. We have investigated this simple and relatively cheap solution. Fourier transformation is used to recognise the differences in the detected laser scanner signal. The result shows that it is possible to recognise objects by this method.
20.
Kruusmaa, Maarja, et al.
(författare)
A low-risk approach to mobile robot path planning
1998
Ingår i: Lecture Notes in Computer Science. - Heidelberg : Springer Berlin/Heidelberg. - 0302-9743 .- 1611-3349. ; 1416, s. 132-141
Tidskriftsartikel (refereegranskat) abstract
This paper presents a self-organizing approach for mobile robot path planning problems in dynamic environments by using case-based reasoning together with a more conventional method of grid-map based path planning. The map-based path planner is used to suggest new innovative solutions for a particular path planning problem. The case-base is used to store the paths and evaluate their traversability. While planning the route those paths are preferred which, according to former experience, are least risky. As the environment changes, the exploration as well as the evaluation of the paths will allow the system to self-organize by forming a set of low-risk paths that are safest to follow. The experiments in a simulated environment show that the robot is able to adapt in a dynamic environment and learns to use the least risky paths. © Springer-Verlag Berlin Heidelberg 1998.
21.
Liu, Guangjun, et al.
(författare)
A Base Force/Torque Sensor Approach to Robot Manipulator Inertial Parameter Estimation
1998
Ingår i: 1998 IEEE International Conference on Robotics and Automation, 1998. Proceedings.. - Piscataway, NJ : IEEE Press. - 078034300X - 0780343018 ; , s. 3316-3321
Konferensbidrag (refereegranskat) abstract
A practical method is proposed for estimating the inertial parameters of robot manipulators with substantial unmodeled joint friction and actuator dynamics. The manipulator is mounted on a six-axis force/torque sensor. Sensor measurements and joint velocities recorded during manipulator motion are used to identify the inertial parameters. The unmodeled joint friction and actuator dynamics do not degrade the estimation results, as in conventional methods. The estimation algorithm does not require difficult-to-measure acceleration measurements. Experimental results presented show that an accurate estimation of inertia parameters is attainable. Since the sensor is external to the manipulator, the same sensor can be used for parameter estimation for a number of different systems. @ IEEE 1998
22.
Malmborg, Jörgen
(författare)
Analysis and Design of Hybrid Control Systems
1998
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Different aspects of hybrid control systems are treated: analysis, simulation, design and implementation. A systematic methodology using extended Lyapunov theory for design of hybrid systems is developed. The methodology is based on conventional control designs in separate regions together with a switching strategy. Dynamics are not well defined if the control design methods lead to fast mode switching. The dynamics depend on the salient features of the implementation of the mode switches. A theorem for the stability of second order switching together with the resulting dynamics is derived. The dynamics on an intersection of two sliding sets are defined for two relays working on different time scales. The current simulation packages have problems modeling and simulating hybrid systems. It is shown how fast mode switches can be found before or during simulation. The necessary analysis work is a very small overhead for a modern simulation tool. To get some experience from practical problems with hybrid control the switching strategy is implemented in two different software environments. In one of them a time-optimal controller is added to an existing PID controller on a commercial control system. Successful experiments with this hybrid controller shows the practical use of the method.
23.
Moore, Philip, et al.
(författare)
Intelligent semi-autonomous vehicles in materials handling
1998
Ingår i: Mechatronics '98. - Oxford : Pergamon Press. - 0080433391 ; , s. 311-316
Konferensbidrag (refereegranskat) abstract
An increase in functionality of Semi-Autonomous Vehicles (SAV) through the implementation of intelligent distributed control and smart sensing techniques is presented. In combination with a modular design approach, this facilitates system modification and improvement, combined with faster customisation of the platform. A distributed and reactive behavioural control architecture will be used to realise local autonomous navigation capabilities; improved operator interaction; self protection and safer operation. A virtual engineering environment based on a suitable computer-aided-graphics platform will be used for modelling the vehicle; the environment in which it can operate; and pre-emptive learning and training of responses / behaviours.
24.
Ujvari, Sandor, 1972-, et al.
(författare)
Simulation and emulation of sensor systems for intelligent vehicles
1998
Ingår i: Mechatronics '98. - : Pergamon Press. - 0080433391 ; , s. 385-390
Konferensbidrag (refereegranskat) abstract
Simulation of sensor systems for mobile robots are described in this paper. By simulation of smart sensor systems, the performance of semi-autonomous vehicles / mobile robots can be enhanced. Smart sensor systems used in the field of mobile robotics can utilise adaptive algorithms. e. g. artificial neural nets, fuzzy logic or hybrid variants of these systems. The development, training and evaluation of adaptive algorithms for sensor systems can be done within a virtual environment in which graphical models are built to simulate an intelligent vehicle, its sensors, and its environment. The virtual sensors are validated by comparing the characteristics of the virtual sensors with those of the real devices.
25.
Adolfsson, Stefan, et al.
(författare)
A Sequential Probability Ratio Test Method for Quality Monitoring in Robotised GMA Welding
1997
Konferensbidrag (refereegranskat) abstract
This paper deals with the problem of automatic monitoring the weld quality when welding with Gas Metal Arc (GMA) in short circuiting mode. Experiments with two different types of T-joints are performed in order to provoke optimal and non-optimal welding conditions. During the experiments, voltage and current are measured from the welding process. A simple statistical change detection algorithm for the weld quality, the repeated Sequential Probability Ratio Test (SPRT), is used. The algorithm can equivalently be viewed as a cumulative sum (CUSUM) - type test. The test statistics is based upon the fluctuations of amplitude in the weld voltage. It is shown that the fluctuations of the weld voltage amplitude decreases when the welding process is not operating under optimal condition. The results obtained from the experiments indicate that it is possible to detect changes in the weld quality automatically and on-line.
26.
Akke, Magnus
(författare)
Some Control Applications in Electric Power Systems
1997
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
This thesis presents some control applications in electric power systems. The work consists of the four parts: interaction between DC cables and ship steering autopilots; frequency estimation; computer relaying; field tests using load switching to damp power oscillations. The first three parts are based on four papers that are given in Appendix A-D. The thesis presents supplementary text to these papers. The last chapter is more self contained and presents field tests from a small hydro power station. These tests show that load switching is an excellent method to damp power oscillations. A proof used in stochastic analysis of fault locators is presented in Appendix E. The first paper presents novel results on interaction of DC cables and ship steering autopilots. Simulations with a non-linear model show that a ship using steering autopilot with a magnetic compass can be captured by a DC cable, i.e, the ship tracks the cable. A full scale experimental study has been performed at the Kontiskan HVDC link. Good agreement was obtained between measurements and computer sinulations. The second paper presents a method for frequency estimation in power systems by demodulation of two complex signals. The third and fourth paper presents some improvements of the differential equation algorithm (DEA) that can be used for transmission line protection. The third paper uses the determinant to explain why isolated estimates from the DEA can be very poor. A median filter is proposed to reject these poor estimates. The fourth paper suggests the followinmg improvements to the DEA: fault classification; intermediate filtering and a new algorithm for three phase faults. Simulation results indicate a nominal operation time of 5-7 ms for three phase faults and slightly longer for other fault types
27.
Berbyuk, Viktor, 1953
(författare)
Dynamics and optimal control of biotechnical systems "Man-Prosthesis"
1997
Ingår i: IUTAM Symposium on Interaction Between Dynamics and Control in Advanced Mechanical Systems, Ed. D. van Campen, Kluwer Academic Publishers, 1997. - Dordrecht : Springer Netherlands. ; , s. 35-42
Konferensbidrag (refereegranskat) abstract
In the paper, a mathematical model is proposed for investigating the controlled motion of human locomotion system (HLS) with an above-knee prosthesis. To provide insight into the interaction between dynamics and control in biotechnical system Man-Prosthesis the energy optimal control problem of the HLS wearing a lower limb prosthesis has been considered. The algorithm is based on special conversion of the optimal control problem for a nonlinear dynamical system which models HLS into a standard nonlinear programming problem. A number of energy-optimal control problems of human locomotion with an artificial leg, and optimization problems for the constructive parameters of the prostheses under different boundary conditions and constraints have been solved. The numerical results obtained were compared with experimental data for normal human locomotion. The energy-optimal elastic and viscoelastic characteristics of the ankle and knee joints of the prostheses have been determined.
28.
Berbyuk, Viktor, 1953, et al.
(författare)
Internal torques of human upper extremity during its optimal motion in vertical plane
1997
Ingår i: The Tenth Biomechanics Seminar. - 1100-2247. ; 10, s. 66-83
Konferensbidrag (refereegranskat) abstract
In the paper a number of optimal control problems for the motion of the human upper extremity (HUE), for different types of working tasks, are considered. The performance index used in these problems is the integral over the duration of the working task of the sum of the square of the controlling stimuli acting at the joints of the human arm. Under some conditions this performance index can be used for evaluation of the muscles' energy expenditure during human movements. The HUE is simulated by a plane multibody system of rigid masses. The system comprises the three elements with mass and rotatory inertia modelled the upper arm, the forearm and the hand. The controlled motions of the mechanical system are described in terms of joint angles and Cartesian coordinates of the shoulder joint, through the application of Lagrange's equations. The main aim of the study is an investigation of the interaction between the gravity forces and the internal torques acting at the joints during goal-directed extremal motions of the HUE. The analysis of the internal torques, energetic and viscoelastic characteristics of the shoulder, the elbow and the wrist joints for the exstremal controlled motions of the human arm under the external load acting on the hand has been done.
29.
Gunnarsson, Svante, 1959-, et al.
(författare)
On the Use of Learning Control for Improved Performance in Robot Control Systems
1997
Ingår i: Proceedings of the 1997 European Control Conference. - Linköping : Linköping University Electronic Press.
Rapport (övrigt vetenskapligt/konstnärligt) abstract
Iterative learning control applied to a simplified model of a robot arm is studied. The iterative learning control input signal is used in combination with conventional feed-back and feed-forward control, and the aim is to let the learning control signal handle the effects of unmodeled dynamics and friction. Convergence and robustness aspects of the choice of filters in the updating scheme of the iterative learning control signal are studied.
30.
Gunnarsson, Svante, 1959-, et al.
(författare)
Some Experiences of the use of Iterative Learning Control for Performance Improvement in Robot Control Systems
1997
Ingår i: Proceedings of the 5th IFAC Symposium on Robot Control. - Linköping : Linköping University Electronic Press. - 0080430260 ; , s. 379-
Rapport (övrigt vetenskapligt/konstnärligt) abstract
Some aspects of the use of learning control for improved performance in robot control systems are studied. The learning control signal is used in combination with conventional feed-back and feed-forward control. The effects of disturbances, unmodeled dynamics and friction are studied theoretically and in simulations of a simplified model of a robot arm. Convergence and robustness aspects of the choice of filters in the updating scheme of the learning control signal are studied.
31.
Johansson, Karl Henrik
(författare)
Relay Feedback and Multivariable Control
1997
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
This doctoral thesis treats three issues in control engineering related to relay feedback and multivariable control systems. Linear systems with relay feedback is the first topic. Such systems are shown to exhibit several interesting behaviors. It is proved that there exist multiple fast relay switches if and only if the sign of the first non-vanishing Markov parameter of the linear system is positive. It is also shown that these fast switches can appear as part of a stable limit cycle. A linear system with pole excess one or two is demonstrated to be particularly interesting. Stability conditions for these cases are derived. It is also discussed how fast relay switches can be approximated by sliding modes. Performance limitations in linear multivariable control systems is the second topic. It is proved that if the top left submatrices of a stable transfer matrix have no right half-plane zeros and a certain high-frequency condition holds, then there exists a diagonal stabilizing feedback that makes a weighted sensitivity function arbitrarily small. Implications on control structure design and sequential loop-closure are given. A novel multivariable laboratory process is also presented. Its linearized dynamics have a transmission zero that can be located anywhere on the real axis by simply adjusting two valves. This process is well suited to illustrate many issues in multivariable control, for example, control design limitations due to right half-plane zeros. The third topic is a combination of relay feedback and multivariable control. Tuning of individual loops in an existing multivariable control system is discussed. It is shown that a specific relay feedback experiment can be used to obtain process information suitable for performance improvement in a loop, without any prior knowledge of the system dynamics. The influence of the loop retuning on the overall closed-loop performance is derived and interpreted in several ways.
32.
Norrlöf, Mikael, 1971-, et al.
(författare)
Using Iterative Learning Control to get Better Performance of Robot Control Systems
1997
Ingår i: Proceedings of Robotikdagarna 1997. - Linköping : Linköping University Electronic Press.
Rapport (övrigt vetenskapligt/konstnärligt) abstract
Many manipulators at work in factories today repeat their motions over and over in cycles and if there are errors in following the trajectory these errors will also be repeated cycle after cycle. The basic idea behind iterative learning control (ILC) is that the controller should learn from previous cycles and perform better every cycle. Iterative learning control is used in combination with conventional feed-back and feed-forward control, and it is shown that learning control signal can handle the effects of unmodeled dynamics and friction. Convergence and disturbance effects as well as the choice of filters in the updating scheme are also addressed.
33.
34.
Samuelsson, Olof
(författare)
Power System Damping - Structural Aspects of Controlling Active Power
1997
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Environmental and economical aspects make it difficult to build new power lines and to reinforce existing ones. The continued growth in demand for electric power must therefore to a great extent be met by increased loading of available lines. A consequence is that power system damping is reduced, leading to a risk of poorly damped power oscillations between the generators. This thesis proposes the use of controlled active loads to increase damping of such electro-mechanical oscillations. The focus is on structural aspects of controller interaction and of sensor and actuator placement. On-off control based on machine frequency in a single machine infinite bus system is analysed using energy function analysis and phase plane plots. An on-off controller with estimated machine frequency as input has been implemented. At a field test it damped oscillations of a 0.9 MW hydro power generator by controlling a 20 kW load. The linear analysis uses two power system models with three and twenty-three machines respectively. Each damper has active power as output and local bus frequency or machine frequency as input. The power system simulator EUROSTAG is used both for generation of the linearized models and for time simulations. Measures of active power mode controllability and phase angle mode observability are obtained from the eigenvectors of the differential-algebraic models. The geographical variation in the network of these quantities is illustrated using the resemblance to bending modes of flexible mechanical structures. Eigenvalue sensitivities are used to determine suitable damper locations. A spring-mass equivalent to an inter-area mode provides analytical expressions, that together with the concept of impedance matching explain the structural behaviour of the power systems. For large gains this is investigated using root locus plots. The effect of using two dampers is studied. For the three machine system this is done for all combinations of the two gains in a certain range. In the twenty-three machine case one gain takes only two values as the other is varied.
35.
Sandewall, Erik, 1945-
(författare)
Logic-Based Modelling of Goal-Directed Behavior
1997
Rapport (övrigt vetenskapligt/konstnärligt) abstract
We address the problem of characterizing goal-directed robotic behavior using a logic of actions and change. Our approach is based on distinguishing two kinds of actions: procedural actions which are defined in a mechanistic way, and goal-directed actions which are performed through a process involving tries, possibly failures, and corrective action and new tries until the goal has been reached. (The definition of procedural actions may be done external to the logic, for example through differential equations, or through a conventional programming language). For both kinds of actions, the logic expresses explicitly whether the action succeeds or fails. Each execution of a goal-directed action is also characterized by a number of breakpoints where some sub-action has been completed and a new sub-action for getting to the desired goal is selected. The logic is used for characterizing the selection of sub-actions at breakpoints, and the success or failure of the goal-directed action in terms of the success or failure of the sub-actions. The article describes how goal-directed actions can be modelled by an extension of existing results on logics of actions and change.
36.
Berbyuk, Viktor, 1953
(författare)
Multibody dynamics and optimization problems of an above-knee prostheses
1996
Konferensbidrag (övrigt vetenskapligt/konstnärligt) abstract
New prosthetic materials and designs have resulted in many prostheses of lower limbs which are presently available for the amputee to use. As a result, it is becoming more difficult for the prosthetists and the physicians to choose which prosthesis is the best for the individual amputee. Presently, there is limited information about how the prosthesis performs dynamically in achieving optimal symmetrical gait for amputee. To provide insight into the interaction between dynamics and control in biotechnical systems and for optimizing the prosthesis's structure the energy-optimal control problem of the human locomotor system (HLS) wearing an above-knee prosthesis has been considered. The algorithm based on multibody dynamics approach and special conversion of the optimal control problem for nonlinear dynamic system model of the HLS into a standard nonlinear programming problem has been proposed. A number of the energy-optimal control problems of human locomotion with an artificial leg and the optimization problems of the constructive parameters of an above-knee prostheses under different boundary conditions and constraints have been solved.
37.
Berbyuk, Viktor, 1953
(författare)
Multibody systems modeling and optimization problems of lower limb prostheses
1996
Ingår i: 1996 IUTAM Symposium on Optimization of Mechanical Systems. - Dordrecht : Springer Netherlands. ; , s. 25-32
Konferensbidrag (refereegranskat) abstract
To study the effect of prosthesis design on the kinematic, dynamic, energetic and other characteristics of an amputee's locomotion and to improve and create new efficient lower limb prostheses it is expendient to use mathematical modeling of a human walk process and dynamic optimization techniques. In this paper a mathematical model is proposed for investigating the dynamics of a man's skeletal system (MSS) with a below-knee prosthesis. A MSS is simulated by a plane controlled dynamic system of rigid masses. The controlled motions of the system are described by Lagrange's equations of the second kind, and for the expressions for kineto-static balance of the prosthesis under the action of ankle and metatarsal moments and the forces of reactions are derived. An algorithm is construced for solving the problem of human gait dynamics with a below-knee prosthesis. The series of dynamics problems for multibody biothechnical system "Man-Prosthesis" and optimization of structural parameters of the artificial lower extremity of a man has been solved.
38.
Eriksson, Patric Tony
(författare)
Enhancements in virtual robotics : Through simulation of sensors, events and 6pre-emptive' learning
1996
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Virtual robotics can be used to dramatically improve the capabilities and performance of industrial robotic systems. Virtual robotics encapsulates graphical off-line programming systems and Computer Aided Robotics (CAR). However current virtual robotic tools suffer from a number of major limitations which severely restrict the ways in which they can be deployed and the performance advantages they offer to the industrial user. The research study focuses on simulation of sensors, programming of event based robotic systerns and demonstrates how intelligent robots can be trained adaptive behaviours in virtual environments. Contemporary graphical programming systems for robots can only be used to program limited sections of a robot program, since i) they do not support methods for the simulation of sensors and event detection; ii) they normally use a post-processor to translate programs from a general language to a controller specific language; iii) conternporary robots can not easily adapt to changes in their environments; and iv) robot programs created off-line must be calibrated to adjust to differences between the virtual and real robotic workcells.The thesis introduces a generic sensor model which can be used to model a variety of sensor types. This model allows virtual sensors to work as independent devices. It is demonstrated that using simulated sensors, event-based robot programs can be created and debugged entirely off-line. Off-line programming of event-based robotic systems demands methods for realistic handling of the communication between independent devices and process. The system must also possess the ability to manage and store information describing status and events in the environment. A blackboard architecture has been used in this research study to store environmental conditions and manage inter-process communication.Self-learning robots is a possible strategy to allow robots to adapt to environmental changes and to learn from their experience. If suitable learning regimes are developed robots can learn to detect changes between virtual and real environments thus minimising the need for calibration. Most learning is based on experience and this requires experimental data to be fed to the learning system. This thesis demonstrates that robot controllers using artificial neural networks for knowledge acquisition and storage can be 'pre-emptively learnt' in virtual robotic environments using virtual robots and simulated sensors. The controllers are able to generalise from the information acquired by the virtual sensors operating in the virtual environment. Arguably the biggest obstacle to the use of self learning robotic systems in real applications has been the need to train the 'real robots' extensively in the 'real environment'. 'Pre-emptive learning' removes this problem. Furthermore, it is therefore possible to develop and evaluate new learning regimes using virtual robotic systems. This approach provides an opportunity to create a variety of environments and conditions which would be impractical to create in a real environment (due to constraints of time, cost and availability).
39.
40.
Jeppsson, Ulf
(författare)
Modelling Aspects of Wastewater Treatment Processes
1996
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Wastewater treatment processes are inherently dynamic because of the large variations in the influent wastewater flow rate, concentration and composition. Moreover, these variations are to a large extent not possible to control. The adaptive behaviour of the involved microorganisms imposes further difficulties in terms of time-varying process parameters. Mathematical models and computer simulations are essential to describe, predict and control the complicated interactions of the processes. The number of reactions and organism species that are involved in the system may be very large. An accurate description of such systems can therefore result in highly complex models, which may not be very useful from a practical, operational point of view. A reduced order dynamic model, describing an activated sludge process performing carbonaceous removal, nitrification and denitrification with reasonable accuracy, is presented. The main objective is to combine knowledge of the process dynamics with mathematical methods for estimation and identification. The identifiability of the model is investigated using both off-line and on-line methods, and its dynamic behaviour is validated by simulations of a recognized model. The information required by the identification algorithms is based on directly measurable real-time data. The simplified model may serve as a tool for predicting the dynamic behaviour of an activated sludge process, since the parameters can be tracked on-line during varying operating conditions. The model is aimed for operation and control purposes as an integral part of a hierarchical control structure. The main objective of the work on settler modelling is to enlighten recent theoretical results. A new one-dimensional settler model is compared to a traditional layer model by means of numerical simulations. Emphasis is put on the numerical solution¹s ability to approximate the analytical solution of the conservation law written as a non-linear partial differential equation. The new settler model is consistent in this respect. Several problems that occur when integrating a model of the biological reactor with a model of the settler are also discussed. In particular, the concentrations of the biological components of the particulate material are of importance for an accurate description of the sludge that is recycled to the biological reactor. Two one-dimensional algorithms have been evaluated. The first algorithm is commonly used and some of its inherent problems are discussed. The second algorithm is a new analytically derived method. Few attempts have been made to take into account the influence of higher order organisms in biofilm systems when developing or applying mathematical models. This work describes a simplified modelling approach to include some possible effects of higher order organisms on nitrification, based on a proposed hypothesis of their oxygen consumption in the biofilm. Three different models are developed and investigated. Model simulations are validated using data from a laboratory experiment using continuous-flow suspended-carrier biofilm reactors, where the predators were selectively inhibited. The proposed models are capable of reproducing several of the observed effects. They are primarily aimed at capturing the steady-state behaviour of the biofilm but may also prove to be a useful basis for describing the dynamics.
41.
42.
Lindeberg, Tony, 1964-, et al.
(författare)
Scale-space with causal time direction
1996
Konferensbidrag (refereegranskat) abstract
This article presents a theory for multi-scale representation of temporal data. Assuming that a real-time vision system should represent the incoming data at different time scales, an additional causality constraint arises compared to traditional scale-space theory—we can only use what has occurred in the past for computing representations at coarser time scales. Based on a previously developed scale-space theory in terms of noncreation of local maxima with increasing scale, a complete classification is given of the scale-space kernels that satisfy this property of non-creation of structure and respect the time direction as causal. It is shown that the cases of continuous and discrete time are inherently different.
43.
Lindstedt, Gunnar
(författare)
Borrowing the Bat's Ear for Automation - Ultrasonic Measurements in an Industrial Environment
1996
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
This work focuses on measurement principles based on ultrasound for applications in industrial automation. The measurements made are of geometric nature. The methods used are when possible based on experience and/or inspiration from the study of bats. A platform for ultrasonic measurements, that allows a VME-based host computer to transmit and receive signals, with a considerable flexibility has been built. Sensor units utilizing both piezoelectric and electrostatic transducers are used. The dimensions of the units are about 10x10x7 centimeters. Frequencies in the range 40-200 kHz are used. The presented measurements include distance, flat surface spatial angle, object localization, object orientation, and object recognition. To make the methods robust matched filters are used in several of the measurements. Frequency sweeps are used to make the ultrasonic measurements more robust to various environmental parameters. Methods that utilize the new information provided by the frequency sweeps are also suggested.
44.
Nilsson, Klas
(författare)
Industrial Robot Programming
1996
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Industrial robots play a key role in manufacturing systems. Robots are distinguished from other types of machinery mainly on the basis of their programmability and ability to be adaptable to different tasks. The use of computer control to achieve desired flexibility implies that software issues for embedded control systems are central for the applicability and utilization of the equipment. The structure of control systems today, however, limits the applicability of robots, thus leaving many human unfriendly operations to be performed manually. This thesis takes a problem oriented approach, without enforcing use of formal methods. Considering industrial demands, such as computing efficiency and simple factory-floor operation, a layered system architecture and technical solutions to accomplish it are proposed. A notion of user views is introduced as the basis for definition of the layers; the layers support programming on levels ranging from implementation of motor control and up to end-user programming. An experimental platform, built around industrially available robots, has been developed. Specially developed hardware interfaces and reconfigurations of the original (ABB) system permits control and programming even of the low level motion control. Run-time efficiency within the proposed open and layered system was achieved by a new concept called actions. Actions are pieces of compiled code that, by use of certain compiling and linking techniques, can be passed as parameters between the layers. The required interplay between application specific programs and built-in motion control could therefore be accomplished. A number of case studies and results from ongoing experimental evaluation indicate that the proposed control system principles are very useful also in an industrial context.
45.
Peterson, Bo
(författare)
Induction Machine Speed Estimation - Observations on Observers
1996
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
This work focuses on observers estimating flux linkage and speed for induction machines, mainly in the low speed region. With speed estimation, sensorless control is possible, meaning that the speed of induction machines without mechanical speed sensors can be controlled. The observer based sensorless drive system has superior dynamic performance compared to a system with an open loop frequency inverter, yet it is neither more complex nor expensive. Using mechanical equivalent models of the induction machine and observers, an accurate flux observer working in the entire speed region of the induction machine is presented. The flux observer is expanded into a combined flux and speed observer, measuring only stator current and voltage. A method for sensorless control is proposed, analyzed and experimentally verified. Observer and controller calculations are performed by a digital signal processor.
46.
Sobral, L., et al.
(författare)
Ultrasonic Detection in Robotic Environments
1996
Ingår i: Proceedings., 1996 IEEE International Conference on Robotics and Automation. - 0780329880 ; 1, s. 347-352
Konferensbidrag (refereegranskat) abstract
Based on information produced by a 200 kHz ultrasonic echo device developed for robotics and other industrial purposes, a method for object identification was developed and is presented in this paper. Interpretation of the echos from the reflecting objects, complexity analysis and information extraction were made by system identification methods such as impulse response analysis and state-space realization. A clustering-type discrimination of different objects based on the echo identification result was made in a subsequent step using the least-squares method. Experimental evaluation showed that the method is effective for object recognition
47.
Bolmsjö, Gunnar, et al.
(författare)
Task Programming of Welding Robots
1995
Ingår i: Proceedings of the International Conference on the Joining of Materials, JOM-7. ; , s. 573-585
Konferensbidrag (refereegranskat)
48.
Eriksson, Patric, et al.
(författare)
A role for 'sensor simulation' and 'pre-emptive learning' in computer aided robotics
1995
Ingår i: 26th International Symposium on Industrial Robots, Symposium Proceedings. - : Mechanical Engineering Publ.. - 1860580009 ; , s. 135-140
Konferensbidrag (refereegranskat) abstract
Sensor simulation in Computer Aided Robotics (CAR) can enhance the capabilities of such systems to enable off-line generation of programmes for sensor driven robots. However, such sensor simulation is not commonly supported in current computer aided robotic environments. A generic sensor object model for the simulation of sensors in graphical environments is described in this paper. Such a model can be used to simulate a variety of sensors, for example photoelectric, proximity and ultrasonic sensors. Tests results presented here show that this generic sensor model can be customised to emulate the characteristics of the real sensors. The preliminary findings from the first off-line trained mobile robot are presented. The results indicate that sensor simulation within CARs can be used to train robots to adapt to changing environments.
49.
50.
Stahre, Johan, 1961
(författare)
Evaluating human/machine interaction problems in advanced manufacturing
1995
Ingår i: Computer Integrated Manufacturing Systems. - 0951-5240. ; 8:2, s. 143-150
Tidskriftsartikel (refereegranskat) abstract
This paper describes a cross-disciplinary research project called ‘Humanufacturing’. In the project, theoretical models for operator roles and human behaviour levels have been combined to evaluate human/machine interaction in modern manufacturing systems. A data collection method, used for case studies in Swedish industry, is described. Also, a prototype decision-support tool based on expert system technology is presented. The conclusion is that theoretical models, previously used in continuous process industry, appear also to be useful in discrete parts manufacturing. Methods used seem to be industrially applicable, and have resulted in specifications for operator training, decision support and education.
