Stefan Brock

Speed control in direct drive with non-stiff load

In this paper several digital filters are considered to handle resonance modes in direct drive servo-mechanical systems. Comparisons are made between the Chebyshev low pass filter, notch filter and bi-quad filter. The effectiveness of the presented methods is verified by simulation and in the laboratory.

New approaches to selected problems of precise speed and position control of drives

The paper reviews the literature in the field of electric drives control, published in the years 2010 - 2012. Attention is focused on three selected themes: torque and force ripple elimination for converter controlled drives, friction identification and compensation, damping of torsional vibrations. These problems are critically important, especially for servo drives used in robots and machine tools.

Robust speed and position control of PMSM

In the paper, the problem of robust speed and position control of a permanent magnet synchronous motor is analysed. The idea of the proposed speed controller is based on the combination of sliding mode control with fuzzy logic rules. The introduction of an integral module to the sliding mode controller leads to fast system dynamics of slight sensitivity to the load parameters variation, effective chattering reduction and elimination of steady state control error. Fuzzy adaptive mechanism tuning a switching gain of sliding-mode controller reduces the speed dynamic error caused by change of load torque. Experimental results obtained during investigation of constructed laboratory stand verify theoretical results and prove good quality of speed and position control.

Modified sliding-mode speed controller for servo drives

In the paper a problem of robustness of sliding-mode speed control for AC drives is analysed. Some high sensitivity of sliding mode speed controllers to high frequency periodic disturbances is shown. The proposed modified structure of sliding mode controller bases on introduction of filtering module, what leads to good system dynamics of slight sensitivity to the load parameters variation, effective chattering reduction and elimination of steady state control. Proposed general structure is universal and can be applied not only in speed control systems. Results of computer simulation study proved low sensitivity of classical sliding mode controller to high frequency disturbances and showed clearly the advantages of elaborated control method. Experimental investigation of constructed laboratory stand verify theoretical investigations and prove main simulation results.

Sliding mode control of a permanent magnet direct drive under non‐linear friction

Purpose – The purpose of this paper is to find a simple structure of motion controller for permanent magnet direct drive. Application of sliding mode controller theory and equivalent disturbance estimator creates proper non‐linear characteristics, which ensures controller robustness against friction.Design/methodology/approach – The position and speed controller is based on robust design methodology introduced by a sliding mode technique. The paper proposes a combination of sliding mode controller and proportional integral (PI) equivalent disturbance estimator. The friction model is Coulomb friction with a large static friction effect. The double boundary layer is used to compensate the effect of stiction. The synthesis is performed using simulation techniques and subsequently the behaviour of a laboratory speed control system is validated in the experimental setup. The control algorithms of the system are performed by a microprocessor floating point DSP control system.Findings – The proposed sliding mode...

The problem of measurement and control of speed in a drive with an inaccurate measuring position transducer

The theoretical limitations of the speed control for drives equipped with an inaccurate, low-resolution position sensor (encoder) are analysed in this paper. Encoder errors as well as time delay introduced by the speed calculation method are considered. The conclusions arising from the theoretical analysis have been confirmed by simulation results.

Fuzzy adaptive PID control for two-mass servo-drive system with elasticity and friction

This paper presents an algorithm of fuzzy adaptive PID controller and addresses its application in vibration suppression of a two mass rotating system. In a performance comparison between the proposed controller strategy and a classical PID control scheme extensive simulations confirmed the superiority of the proposed fuzzy adaptive controller. The results show that accurate tracking performance of the servo-drive system with two-mass load has been achieved.

Application of neuro‐fuzzy techniques to robust speed control of PMSM

Purpose – The purpose of the paper is to find a simple structure of speed controller robust against drive parameter variations. Application of neuro‐fuzzy technique in the controller of PI type creates proper nonlinear characteristics, which ensures controller robustness.Design/methodology/approach – The robustness of the controller is based on its nonlinear characteristic introduced by neuro‐fuzzy technique. The paper proposes a novel approach to neural controller synthesis to be performed in two stages. The first stage consists in training the neuro‐fuzzy system to form the proper shape of the control surface, which represents the nonlinear characteristic of the controller. At the second stage, the PI controller settings are adjusted by means of the random weight change procedure, which optimises the control quality index formulated in the paper. The synthesis is performed using simulation techniques and subsequently the behavior of a laboratory speed control system is validated in the experimental setu...

Two Approaches to Speed Control for Multi-Mass System With Variable Mechanical Parameters

This paper is dedicated to the motion control system of a multimass mechanism with occurring resonances and variable moment of inertia. The proposed concept of control structure for such mechanism consists of a filter damping higher resonance frequencies and an adaptive speed controller. The filter has properly selected fixed characteristics giving a compromised filtering effect in a range of resonance frequency variation, caused by the variable moment of inertia. The used neural adaptive controller realizes active damping of lower resonance frequencies, which are not eliminated by the resonance filter. This original concept is compared with a more complex solution, treated as a reference, which contains an offline-tuned resonance filter together with an offline-adjusted PI-two degrees of freedom controller. Good speed control dynamic properties of the proposed concept in comparison with the reference complex solution are proven by laboratory results.

Analysis of input shaping and PID-controller interaction structures for two-mass systems

Many mechanical systems are characterized by flexible joints. These kinds of systems are often exposed for mechanical oscillations. These objects are represented by cranes, long manipulators arms or conveyors drives. All these objects can be approximated by multi-mass systems. To avoid the oscillations the input shaper method can be used. The main control strategies are usually based on PID controllers. The paper shows possible structures of interaction between PID controllers and input shaping.