Last issue
2016 (vol. 26) - Number 4


Andrzej Ruszewski:

Practical and asymptotic stability of fractional discrete-time scalar systems described by a new model



D. Krokavec, A. Filasova, P. Liscinsky:

On fault tolerant control structures incorporating fault estimation



Sundarapandian Vaidyanathan:

Hyperchaos, adaptive control and synchronization of a novel 4-D  hyperchaotic system with two quadratic nonlinearities



H. Górecki, M. Zaczyk:

Analytic solutions of transcendental equations with application to automatics



F. Mnif:

Predictor-based stabilization for chained form systems with input time delay



S. Daniar, R. Aazami, M. Shiroei:

Multivariable predictive control considering time delay for load-frequency control in multi-area power systems



T. Kaczorek:

Analysis and comparison of the stability of discrete-time and continuous-time linear systems



M. Rachik, M. Lhous:

An observer-based control of linear systems with uncertain parameters



L. Malinski:

Identification of stable elementary bilinear time-series model



V.V. Huynh:

New observer-based control design for mismatched uncertain systems with time-delay




ACS Abstract:

2002 (Volume 12)
Number 1/2
1. Feedback control of nonholonomic wheeled vehicles. A survey.
2. A new control algorithm for a nonholonomic mobile robot
3. 3-D objects motion estimation based on Kalman Filter and BSP Tree Models for Robot Stereo Vision
4. A robotic stepper device concept for locomotion rehabilitation
5. Sensor system for Safari wall-climbing robot
6. Feed-forward torques and reference trajectory for an arm with flexible joints
7. From Continuous to Discrete Models of Linear Repetitive Processes


Feedback control of nonholonomic wheeled vehicles. A survey.Download full PDF article
Pascal Morin and Claude Samson
(INRIA, France)

The paper is an introduction and overview to the problem of feedback control of nonholonomic wheeled vehicles. Solutions proposed during the last decade and a new approach currently developed by the authors of this article are presented.

keywords: wheeled mobile robots, nonholonomic systems, driftless nonlinear systems, feedback control, stabilization.

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A new control algorithm for a nonholonomic mobile robotDownload full PDF article
Krzysztof Kozłowski and Jarosław Majchrzak
(Poznań University of Technology, Poland)

In this paper a trajectory tracking control problem for a nonholonomic mobile robot by making use of a kinematic oscillator has been solved. Firstly - time varying oscillator is examined to control nonholonomic mobile robot based only on its kinematics. Secondly - backstepping procedure is proposed to include robot dynamics and servo loop. It is shown that overall multilevel controller is asymptotically globally stable to a small error different from zero. A wide range of simulation results are presented which illustrate behaviour of the controller with respect to tuning its parameters. Some preliminary experiments are reported too.

keywords: mobile robot, nonholonomic constraints, backstepping procedure.

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3-D objects motion estimation based on Kalman Filter and BSP Tree Models for Robot Stereo VisionDownload full PDF article
Vincenzo Lippiello, Bruno Siciliano and Luigi Villani
(Universita degli Studi di Napoli Federico II, Italy)

The problem of the real time estimation of the position and orientation of moving objects for position-based visual servoing control of robotic systems is considered in this paper. A computationally efficient algorithm is proposed based on Kalman filtering of the visual measurements of the position of suitable feature points selected on the target objects. The efficiency of the algorithm is improved by adopting a pre-selection technique of the feature points, based on Binary Space Partitioning (BSP) tree geometric models of the target objects, which takes advantage of the Kalman filter prediction capability. Computer simulations are presented to test the performance of the estimation algorithm in the presence of noise, different types of lens geometric distortion, quantization and calibration errors.

keywords: vision, robot manipulators, visual servoing, visual tracking, Kalman filter, Binary Space Partitioning tree.

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A robotic stepper device concept for locomotion rehabilitationDownload full PDF article
Antal K. Bejczy
(California Institue of Technology, USA)

A novel strategy for rehabilitation of locomotion impaired subjects uses a Body Weight Support Technique (BWST) on a treadmill which involves three to four therapists to carry out the required patient training exercises on the treadmill. This paper briefly describes (i) the essence of the novel rehabilitation strategy, including its medical background, (ii) the technical approach to the design and development of a robotic device aimed to reduce the manual involvement of at least two therapists in the locomotion training exercises on a treadmill, and (iii) the main conceptual design features of a possible robotic device.

keywords: biped locomotion, rehabilitation, treadmill, force-torque sensing, human-machine interaction and interface.

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Sensor system for Safari wall-climbing robotDownload full PDF article
Piotr Dutkiewicz and Marek Ławniczak
(Poznań University of Technology, Poland)

This paper describes the structure of sensor system for a~mobile robot. The information flow in this sensor system is also presented, including a~short description of used buses and protocols. Components used for construction of the system are briefly characterized. In one of the sections of the paper, an obstacles detection algorithm, useful for path planning for mobile robots, is presented. The application of this algorithm has been enclosed in that section, summarized by experimental results. Good speed of image processing, obtained by proposed method, gives possibility to detect obstacles in real time.

keywords: sensor system, data flow, mobile robotics, walking robot, climbing robot, image processing, vision system.

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Feed-forward torques and reference trajectory for an arm with flexible jointsDownload full PDF article
Yannick Aoustin
(Institut de Recherche en Communications et Cybern?tique de Nantes, France)
Alexander Formal'sky
(Moscow State Lomonosov University, Russia)

We propose a design method of the feed-forward torques and the reference trajectory for an arm with flexible joints and unknown stiffness coefficients. The bounds on the control torque are included explicitly. The designed commanded feed-forward torques and the corresponding reference trajectory are close to be time-optimal. The control law for each drive torque is composed with the commanded feed-forward torque and linear angular position and velocity feedback. The torques and the trajectory are used as input signals of PD-controllers.
In a case of one-link flexible arm it is proved that so-called 'fluent' control torque enables to reach the desired motion with a small error and without large vibrations in the flexible joint. Designed fluent commanded feed-forward torque is successfully implemented in numerical experiments. The stiffness coefficient is assumed to be unknown so the mathematical model of the flexible arm is not known exactly.
In two-link flexible arm the stiffness coefficients are also assumed unknown. Due to discontinuities of the optimal control functions and not acceptable jumps in the optimal control torques a `trapezoidal' fluent control technique is proposed. Numerical experiments show that the designed control is close to time-optimal.
The approach presented in the paper can be extended to systems with more links and can take the gravity into consideration. However, in this case a time-optimal or a quasi-time-optimal control for the associated rigid system have to be designed.

keywords: one-two-link arm, flexible joint, control torque, torque bound, reference trajectory, feed-forward and feedback control.

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From Continuous to Discrete Models of Linear Repetitive ProcessesDownload full PDF article
Artur Gramacki, Jarosław Gramacki
(University of Zielona Góra, Poland)
Eric Rogers
(University of Southampton, UK)
David H. Owens
(University of Sheffield, UK)

Differential linear repetitive processes are a distinct class of 2D linear systems which pose problems which cannot (except in a few very restrictive special cases) be solved by application of existing linear systems theory, and hence by the use of many of the currently available tools for computer aided analysis and simulation. One such problem area is the construction of accurate numerically well conditioned discrete approximations of the dynamics of differential processes which could, as one example of a number of immediate applications areas, form the basis for the digital implementation of control laws. In this paper, we undertake a detailed investigation of the critical problems which arise when attempting to construct useful (for onward asnalysis/design studies) discrete approximations of the dynamics of differential linear repetitive processes and develop solutions to them. Numerical examples to support the results obtained are also given using a specially developed MATLAB based toolbox.

keywords: linear repetitive processes, discretization, MATLAB Toolbox, examples.

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