| 1. |
- Birk, Wolfgang, et al.
(författare)
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Foam level control in a water model of the LD converter process
- 2003
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Ingår i: Control Engineering Practice. - 0967-0661 .- 1873-6939. ; 11:1, s. 49-56
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with estimation and control of foam level in dynamic foaming. An improved foam level estimation methodology from a microphone signal and its automatic calibration is presented. The dynamical reaction of the foam level on air lance movements is modelled using system identification. Based on the resulting mathematical model, a controller for foam level stabilisation is designed and applied to a water model, representing the LD converter process. It is shown that the foam level can be controlled using a microphone as the measurement device and air lance movement as the actuator.
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| 2. |
- Birk, Wolfgang, et al.
(författare)
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Implementation and industrial experiences of advanced control and monitoring in coal injection
- 2000
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Ingår i: Control Engineering Practice. - 0967-0661 .- 1873-6939. ; 8:3, s. 327-335
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes the implementation and industrial experiences of a model-based control and gas-leakage detection system in a coal injection plant. It describes how advanced control and monitoring can be implemented in an industrial environment while taking human–machine interface aspects into consideration. The operation of the advanced and the conventional concept are compared regarding evaluation data, experiences and observations of operators and maintenance personnel. It is shown that the advanced control and monitoring system improves plant performance without disturbing routines in plant operation and, moreover, is positively accepted by the plant operators.
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| 3. |
- Eriksson, Lars, 1970-, et al.
(författare)
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Ionization Current Interpretation for Ignition Control in Internal Combustion Engines
- 1997
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Ingår i: Control Engineering Practice. - : Pergamon Press. - 0967-0661 .- 1873-6939. ; 5:8, s. 1107-1113
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Tidskriftsartikel (refereegranskat)abstract
- Spark advance setting in spark-ignited engines is used to place the in-cylinder pressure curve relative to the top dead center. A feedback scheme, not a calibration scheme, based on ionization current is proposed here. It is thus related to pressure sensor feedback schemes, that have reported good results, but have not yet been proved cost effective, due to the cost of the pressure sensor. The method proposed here is very cost-effective, since it uses exactly the same hardware and instrumentation (already used in production cars) that is used to utilize the spark plug as a sensor to detect misfire and as a sensor for knock control. A key idea in the method is to use parameterized functions to describe the ionization current. These parameterized functions are used to separate out the different phases of the ionization current. Special emphasis is laid on getting a correct description of the pressure development. The results are validated on a SAAB 2.3 l production engine by direct comparison with an in-cylinder pressure sensor (used only for validation, not for control), but also by using a physical model relating the ionization current to the pressure.
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| 4. |
- Gunnarsson, Fredrik, et al.
(författare)
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Control Theory Aspects of Power Control in UMTS
- 2003
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Ingår i: Control Engineering Practice. - : Elsevier. - 0967-0661 .- 1873-6939. ; 11:10, s. 1113-1125
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Tidskriftsartikel (refereegranskat)abstract
- The global communication systems critically rely on control algorithms of various kinds. In universal mobile telephony system (UMTS)-the third generation mobile telephony system just being launched-power control algorithms play an important role for efficient resource utilization. This survey article describes and discusses relevant aspects of UMTS power control with emphasis on practical issues, using an automatic control framework. Generally, power control of each connection is distributedly implemented as cascade control, with an inner loop to compensate for fast variations and an outer loop focusing on longer term statistics. These control loops are interrelated via complex connections, which affect important issues such as capacity, load and stability. Therefore, both local and global properties are important. The concepts and algorithms are illustrated by simple examples and simulations.
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| 5. |
- Gunnarsson, Svante, et al.
(författare)
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Tuning of a Decoupling Controller for a 2×2 System using Iterative Feedback Tuning
- 2003
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Ingår i: Control Engineering Practice. - : Elsevier. - 0967-0661 .- 1873-6939. ; 11:9, s. 1035-1041
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Tidskriftsartikel (refereegranskat)abstract
- Iterative feedback tuning is used to tune a decoupling controller for a 2 × 2 multivariable system. The tuning is carried out in two steps. In the first step the coefficients of two proportional decoupling controllers are tuned, and in the second step two PD-controllers are tuned. The approach is evaluated on a nonlinear simulation model of a two-link manipulator. The evaluation is carried out using two different reference trajectories and also in the presence of friction. The resulting closed loop systems show satisfactory behavior in all three cases.
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| 6. |
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| 7. |
- Holmberg, Ulf, et al.
(författare)
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An identification-for-control procedure with robust performance
- 2000
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Ingår i: Control Engineering Practice. - Exeter : Elsevier. - 0967-0661 .- 1873-6939. ; 8:10, s. 1107-1117
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Tidskriftsartikel (refereegranskat)abstract
- A data-driven controller design procedure is proposed in this paper. The controller is based on both an estimated plant model and its estimated uncertainty described by an ellipsoid in parameter space. Desired performance is specified by the speed and the damping of the modeled response. The unmodeled response is rejected by requiring robust performance with respect to a generalized stability region. Moreover, estimation of a disturbance model enables further rejection of the unmodeled response. The methodology is applied to a nonlinear and unstable magnetic suspension system. High performance is achieved for various specifications over a large operational range.
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| 8. |
- McKelvey, Tomas, et al.
(författare)
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On Adaptive Smoothing of Empirical Transfer Function Estimates
- 2000
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Ingår i: Control Engineering Practice. - 0967-0661 .- 1873-6939. ; 8:11, s. 1309-1315
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Tidskriftsartikel (refereegranskat)abstract
- The determination of the right resolution parameter when estimating frequency functions of linear systems is a trade-off between bias and variance. Traditional non-parametric approaches, like `window-closing' employ a global resolution parameter - the window width - that is tuned by ad hoc methods, usually visual inspection of the results. This paper suggests a method that tunes such parameters by an automatic procedure. A further benefit is that the tuning can be performed locally, i.e., that different resolutions can be used in different frequency bands. The ideas are based on local polynomial regression and a data-driven bandwidth selector. The advantages of the proposed method are illustrated in numerical examples.
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| 9. |
- Nilsson, Bernt, et al.
(författare)
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Control of flexible mobile manipulators: positioning and vibration reduction using an eye-in-hand range camera
- 1999
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Ingår i: Control Engineering Practice. - 0967-0661 .- 1873-6939. ; 7:6, s. 741-751
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the positioning of a long flexible manipulator on a moving platform is investigated. The problem is to position the gripper at a requested relative distance in front of an object with unknown location. For this purpose, the gripper is equipped with a range camera giving the distance to surrounding objects within, ∼ 1% and with a sampling rate above 1 kHz. The range measurements are used in combination with internal angle measurements from joint encoders to estimate both the flexibility in the mechanical construction and the relative distance from gripper to object. This is solved satisfactorily by an extended Kalman filter (EKF). For the motion control of the manipulator, a time-scaled feedback controller is suggested. A fast inner loop is used to damp out oscillations and reject disturbances, both from the platform and the manipulator. An outer control loop, with a lower closed-loop bandwidth, then steers the gripper, based on the range measurements, to the requested final position in front of the object. This loop assumes a stationary and rigid platform and a rigid manipulator. At this moment, only simulations of a flexible manipulator on a rigid platform have been studied. However, the results show that the flexibility can be estimated from indirect measurements of the range to the object and the joint angles. Also, good damping and disturbance rejection are achieved, as long as the bandwidth of the actuators is sufficiently high compared to the oscillation. The use of range measurements of the surrounding objects makes the positioning task very robust against an uncertain platform position.
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| 10. |
- Nilsson, Kenneth, 1951-, et al.
(författare)
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A modular, massively parallel computer architecture for trainable real-time control systems
- 1993
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Ingår i: Control Engineering Practice. - Kidlington, Oxford : Pergamon Press. - 0967-0661 .- 1873-6939. ; 1:4, s. 655-661
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Tidskriftsartikel (refereegranskat)abstract
- A new system-architectural concept for trainable real-time control systems is based on resource adequacy both in processing and communication. Cyclically executing programs in distributed nodes communicate via a shared high-speed medium. Static scheduling of programs and communication implies that the maximum possible work-load can always be handled in a time-deterministic manner. The use of Artificial Neural Networks (ANN) algorithms and trainability implies a new system development strategy based on a Continuous Development paradigm. An implementation of the Architectural concept is presented. The communication speed is measured in Gbps and the access method is TDMA. An implementation of the system-development strategy is also presented. © 1993.
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