2003 (Volume 13)
Robot controller with a self-measurement capability enabling the identification of friction
|Adam Wozniak, Wojciech Szynkiewicz and Cezary Zielinski|
(Warsaw University of Technology, Poland)
This paper proposes an open controller structure which beside realising the diverse control tasks enables gathering of the identification data which in turn can be utilised for improving servo control algorithms. The authors are convinced that in the case of research-oriented controller architectures self-identification and self-measurement components should be included. Moreover the paper shows how the gathered data has been utilised in the modelling of friction. This problem has been investigated to increase the precision of motions of a robot equipped with a machinning head.
keywords: robot controller, servomechanism, friction model, identification.
The interval parabolic system
(University of Mining and Metallurgy, Poland)
In the paper a new interval model for the uncertain, parabolic time invariant system is presented. System under consideration is described by model with two dimensional uncertain parameters space. In this case the simple geometric interpretation of the system spectrum and it's decomposition can be presented. The proposed spectrum decomposition conditions are based on the geometric interpretation of the system spectrum. The results are by the examples depicted.
keywords: interval systems, parabolic systems,the exponential stability.
On controllability and minimum energy control of linear positive systems with delays
(Silesian University of Technology, Poland)
The positive stationary dynamical systems with multiple delays in control are considered in the paper. The definition of the relative controllability for positive systems with delays and the criterions of their relative controllability are given. The minimum energy control problem for these systems is formulated and solved. Numerical examples illustrate the theoretical analysis. The example of real, technological positive dynamical system as a practical application of the theoretical results is presented.
keywords: positive dynamical systems, delay systems, relative controllability, admissible control, minimum energy control.
Active control of circular plate vibration by using piezoceramic actuators
|Lucyna Leniowska and Ryszard Leniowski|
(University of Rzesz?w, Poland)
An active vibration control system is proposed for suppressing small amplitude harmonic vibrations of a thin circular plate. This system integrates control algorithms, intelligent materials, hardware and software technologies. The mathematical model of the physical system is based upon the geometry and properties of an experimental set-up consisting of a hard-walled cylinder with a thin aluminium plate at one end. Primary excitation is provided by a low frequency loudspeaker installed centrally at the bottom of the cylinder. The vibrations of the plate are measured by the application of strain sensors. Intelligent materials such as 2-layer piezo disk elements (PZT) are used as the actuator. For the considered system, the OE ( Output Error ) method of discrete-time model identification for real-time active vibration control has been applied. On the basis of this model, the control algorithm based on pole-placement method has been developed. The obtained results show that the designed structure of a closed-loop system provides substantial vibration suppression.
keywords: active vibration control, feedback control, piezoceramic transducers, identification methods.
Multivariable robust control applied to steering of three ship's velocities
(Gdynia Maritime University, Poland)
The main goal of this task was the synthesis of the regulator for precise steering of the real, training ship. One of possible ways to build a proper ship's controller can be the robust control theory approach. First part of the paper describes successively: the shiphandling training boat "Blue Lady", nonlinear simulation model of the vessel and the MIMO state ship model, identified for robust regulator synthesis after experiments on the presented simulation model. Second part of the paper presents: the way to calculate the multivariable controller via D-K iteration, final regulator and exemplary results of the real-time steering for verification of obtained closed-loop system.
keywords: training ship, simulation model, multivariable system, robust control, real-time steering.
Hierarchical control in a large scale stochastic system with nonclassical information structure
|Zdzislaw Duda and Witold Brandys|
(Silesian University of Technology, Poland)
In the paper a synthesis of a control law for a large scale stochastic system is presented. The system composed of coupled linear subsystems and quadratic performance index which should be minimized, is considered. The problem is solved in a two-level hierarchical control structure with a coordinator on an upper level and local controllers on a lower level. An algorithm, in which it is possible to partially decompose calculations and to realize decentralized control, is proposed. A simple example is presented.
keywords: large scale system, stochastic system, decentralized control, optimal control.
Errors of elementary floating-point operations in control algorithms
(Technical University of Rzeszow, Poland)
The paper presents analytical development of error variances for elementary floating-point operations, i.e. quantization, multiplication, and addition, based on expressions for probability density distributions. Gaussian inputs are assumed and steps executed by the processor taken into account, particularly normalization of the mantissa to the interval [ 0.5 , 1 ). Uniform estimate
of the variance for the three elementary operations is obtained, where b
denotes the number of mantissa bits. Error of Euler rectangular integrator
, commonly used in digital controllers, is evaluated as well. For small sampling step the error depends primarily on precision of the addition executed by the integrator. Increase of the precision used in some small controllers is also considered. The results are verified for first-order transfer function subject to white noise, sinusoidal and constant-plus-noise inputs.
keywords: floating-point arithmetic, roundoff errors, delta-operator, stochastic systems.