| 1. |
- Liu, Yang, et al.
(author)
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A Study Towards Reliability- and Delay-Critical Wireless Communication for RoboCup Robotic Soccer Application
- 2007
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In: 2007 International Conference on Wireless Communications, Networking and Mobile Computing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1424413117 - 9781424413119 - 1424413125 - 1424413125 - 1424413117 ; , s. 633-636
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Conference paper (peer-reviewed)abstract
- RoboCup is an international competition for a team of multiple fast-moving robots under a dynamic environment to autonomously play soccer game against another team. Due to the nature of the competition, the requirements and constraints for the wireless communication are extremely tight. The challenge is that wireless communication is involved in the control loop and therefore the reliability and propagation delay are vital factors which directly affect the team performance. Beside, various interferences with known and unknown frequency / transmission power usually exist at the competition site, which are hazardous environment to achieve reliable and low latency performance for wireless communication. This paper investigates the performance strengths and weaknesses of wireless communication means e.g. RF, IEEE 802.11a/b, IEEE 802.15.4, DECT, Linx, etc, which are commonly used nowadays in different RoboCup teams and propose improvements towards reliable and delay-critical wireless communication.
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| 2. |
- Freidovich, Leonid, et al.
(author)
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Modification via averaging of partial-energy-shaping control for orbital stabilization : cart-pendulum example
- 2006
-
In: Proceedings of the 45th IEEE conference on decision and control, vols 1-14. - New York : IEEE Press. - 9781424401703 ; , s. 6150-6155
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Conference paper (peer-reviewed)abstract
- We consider the problem of creating oscillations with respect to a part of state variables in underactuated mechanical systems. The main contribution is a modification of a recently proposed control strategy, exploiting passivity to shape the energy of the system with respect to a subset of the state variables and neglecting the dynamics of the other ones. We propose a way to design an additional control action, which guarantees boundedness of the motion of these other degrees of freedom, which otherwise almost always evolve without any bound. The idea is presented on the well-known two-degrees-of-freedom benchmark example of inverted pendulum on a cart.
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| 3. |
- Shiriaev, Anton, et al.
(author)
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Constructive tool for orbital stabilization of underactuated nonlinear systems : virtual constraints approach
- 2005
-
In: IEEE Transactions on Automatic Control. - Piscataway : IEEE Press. - 0018-9286 .- 1558-2523. ; 50:8, s. 1164-1176
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Journal article (peer-reviewed)abstract
- We present a constructive tool for generation and orbital stabilization of periodic solutions for underactuated nonlinear systems. Our method can be applied to any mechanical system with a number of independent actuators smaller than the number of degrees of freedom by one. The synthesized feedback control law is nonlinear and time-dependent. It is derived from a feedback structure that explicitly uses the general or full integral of the systems zero dynamics. The control law generates a periodic solution and makes it exponentially orbitally stable.
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| 4. |
- Jansson, Magnus, et al.
(author)
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Synchronization at startup and stable rotation reversal of sensorless nonsalient PMSM drives
- 2006
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In: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0046 .- 1557-9948. ; 53:2, s. 379-387
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Journal article (peer-reviewed)abstract
- In this paper, a variant of the well-known voltage model is applied to rotor position estimation for sensorless control of nonsalient permanent-magnet synchronous motors (PMSMs). Particular focus is on a low-speed operation. It is shown that a guaranteed synchronization from any initial rotor position and stable reversal of rotation can be accomplished, in both cases under load. Stable rotation reversal is accomplished by making the estimator insensitive to the stator resistance. It is also shown that the closed-loop speed dynamics are similar to those of a sensored drive for speeds above approximately 0.1 per unit, provided that the model stator inductance is underestimated. Experimental results support the theory.
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| 5. |
- Rönnbäck, Sven
(author)
-
Circle sectors for detection of oncoming cars in range data
- 2008
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In: 2008 4th International IEEE Conference Intelligent Systems. - Piscataway, NJ : IEEE Communications Society. - 9781424417391 - 9781424417407 ; , s. 17-40
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Conference paper (peer-reviewed)abstract
- This paper presents how expanding circle sectors are used for finding free-space in front of a vehicle equipped with a laser range finder. The circle sectors give support for detection of oncoming cars since they will cause changes in the circle sector parameters. The velocities and headings of detected oncoming cars are estimated from clustered range data that are time stamped.
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| 6. |
- Manchester, Ian R, et al.
(author)
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Vision-based interception of a moving target by a mobile robot
- 2007
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In: Proceedings of the 2007 IEEE conference on control applications, vols 1-3. - New York : IEEE conference proceedings. - 9781424404421 ; , s. 397-402
-
Conference paper (peer-reviewed)abstract
- We present a robot navigation technique, termed circular navigation guidance (CNG), which solves the challenging problem of intercepting a moving target from a specific angle, using only data from a video camera. The guidance law is not split into path-planning and path-following stages, but is continuously updated based on immediately available information, making it practical even against a manoeuvring target, or where only incomplete information is available to the robot. This is achieved by converting a finite-time navigation problem into one of maintaining a certain geometric condition at all tunes. Theoretical and experimental results are presented, which support CNG as a practically useful tool for robot navigation.
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| 7. |
- Jonasson, Mats, et al.
(author)
-
Autonomous corner modules as an enabler for new vehicle chassis solutions
- 2006
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In: FISTA Transaction. ; 2006:F2006V054T
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Journal article (peer-reviewed)abstract
- Demands for new functions and refined attributes in vehicle dynamics are leading to more complex and more expensive chassis design. To overcome this, there has been increasing interest in a novel chassis design that could be reused in the development process for new vehicle platforms and mainly allow functions to be regulated by software. The Autonomous Corner Module (ACM) was invented at Volvo Car Corporation (VCC) in 1998. The invention is based upon actively controlled functions and distributed actuation. The main idea is that the ACM should enable individual control of the functions of each wheel; propulsion/braking, alignment/steering and vertical wheel load. This is done by using hubmotors and by replacing the lower control arm of a suspension with two linear actuators, allowing them to control steering and camber simultaneously. Along with active spring/damper and wheel motors, these modules are able to individually control each wheel's steering, camber, suspension and spin velocity. This provides the opportunity to replace mechanical drive, braking, steering and suspension with distributed wheel functions which, in turn, enable new vehicle architecture and design. The aim of this paper is to present the vehicle dynamic potential of the ACM solution, by describing its possible uses and relating them to previous research findings. Associated work suggests chassis solutions where different fractions of the functions of the ACM capability have been used to achieve benefits in vehicle dynamics. For instance, ideas on how to use active camber control have been presented. Other studies have reported well-known advantages, such as, good transient yaw control from in-wheel motor propulsion and stable chassis behaviour from four-wheel steering, when affected by side wind. However, this technology also presents challenges. One example is how to control the relatively large unsprung mass that occurs due to the extra weight from the in-wheel motor. The negative influence from this source can be reduced by using active control of vertical forces. The implementation of ACM, or similar technologies, requires a well-structured hierarchy and control strategy. Associated work suggests methods for chassis control, where tyre forces can be individually distributed from a vehicle path description. The associated work predominately indicates that the ACM introduces new opportunities and shows itself to be a promising enabler for vehicle dynamic functions.
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| 8. |
- Jonasson, Mats, et al.
(author)
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Design and evaluation of an active electromechanical wheel suspension system
- 2008
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In: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 18:4, s. 218-230
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Journal article (peer-reviewed)abstract
- This paper presents an electromechanical wheel suspension, where the upper arm of the suspension has been provided with an electric levelling and a damper actuator, both are allowed to work in a fully active mode. A control structure for the proposed suspension is described. The complex design task involving the control of the electric damper and its machine parameters is tackled by genetic optimisation. During this process, these parameters are optimised to keep the power dissipation of the electric damper as low as possible, while maintaining acceptable comfort and road-holding capabilities. The results of the evaluations carried out demonstrate that the proposed suspension can easily adopt its control parameters to obtain a better compromise of performance than that offered by passive suspensions. If the vehicle is to maintain acceptable performance during severe driving conditions, the damper has to be unrealistically large. However, if the electric damper is combined with a hydraulic damper, the size of the electric damper is significantly reduced. In addition, the design of the electric damper with the suggested control structure, including how it regenerates energy, is discussed.
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| 9. |
- Jonasson, Mats, 1969-
(author)
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Exploiting individual wheel actuators to enhance vehicle dynamics and safety in electric vehicles
- 2009
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Doctoral thesis (other academic/artistic)abstract
- This thesis is focused on individual wheel actuators in road vehicles intended for vehicle motion control. Particular attention is paid to electro-mechanical actuators and how they can contribute to improving vehicle dynamics and safety. The employment of individual wheel actuators at the vehicle's four corner results in a large degree of over-actuation. Over-actuation has a potential of exploiting the vehicle's force constraints at a high level and of controlling the vehicle more freely. One important reason for using over-actuated vehicles is their capability to assist the driver to experience the vehicle as desired. This thesis demonstrates that critical situations close to the limits can be handled more efficiently by over-actuation. To maximise the vehicle performance, all the available actuators are systematically exploited within their force constraints. Therefore, force constraints for the individually controlled wheel are formulated, along with important restrictions that follow as soon as a reduction in the degrees of freedom of the wheel occurs. Particular focus is directed at non-convex force constraints arising from combined tyre slip characteristics. To evaluate the differently actuated vehicles, constrained control allocation is employed to control the vehicle. The allocation problem is formulated as an optimisation problem, which is solved by non-linear programming. To emulate realistic safety critical scenarios, highly over-actuated vehicles are controlled and evaluated by the use of a driver model and a validated complex strongly non-linear vehicle model. it is shown that, owing to the actuator redundancy, over-actuated vehicles possess an inherent capacity to handle actuator faults, with less need for extra hardware or case-specific fault-handling strategies.
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| 10. |
- Kootstra, Gert, 1978-, et al.
(author)
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Tackling the Premature Convergence Problem in Monte-Carlo Localization
- 2009
-
In: Robotics and Autonomous Systems. - Amsterdam, The Netherlands : Elsevier. - 0921-8890 .- 1872-793X. ; 57:11, s. 1107-1118
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Journal article (peer-reviewed)abstract
- Monte-Carlo localization uses particle filtering to estimate the position of the robot. The method is known to suffer from the loss of potential positions when there is ambiguity present in the environment. Since many indoor environments are highly symmetric, this problem of premature convergence is problematic for indoor robot navigation. It is, however, rarely studied in particle filters. We introduce a number of so-called niching methods used in genetic algorithms, and implement them on a particle filter for Monte-Carlo localization. The experiments show a significant improvement in the diversity maintaining performance of the particle filter.
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