Péter Korondi

Fuzzy Control System Performance Enhancement by Iterative Learning Control

This paper suggests low-cost fuzzy control solutions that ensure the improvement of control system (CS) performance indices by merging the benefits of fuzzy control and iterative learning control (ILC). The solutions are expressed in terms of three fuzzy CS (FCS) structures that employ ILC algorithms and a unified design method focused on Takagi-Sugeno proportional-integral fuzzy controllers (PI-FCs). The PI-FCs are dedicated to a class of servo systems with linear/linearized controlled plants characterized by second-order dynamics and integral type. The invariant set theorem by Krasovskii and LaSalle with quadratic Lyapunov function candidates is applied to guarantee the convergence of the ILC algorithms and enable proper setting of the PI-FC parameters. The linear PI controller parameters tuned by the extended symmetrical optimum method are mapped onto the PI-FC ones by the modal equivalence principle. Real-time experimental results for a dc-based servo speed CS are included.

Trajectory Tracking by TP Model Transformation: Case Study of a Benchmark Problem

The main objective of this paper is to study the recently proposed tensor-product-distributed-compensation (TPDC)-based control design framework in the case of tracking control design of a benchmark problem. The TPDC is a combination of the tensor product model transformation and the parallel distributed compensation framework. In this paper, we investigate the effectiveness of the TPDC design. We study how it can be uniformly and readily executed without analytical derivations. We show that the TPDC is straightforward and numerically tractable, and is capable of guaranteeing various different control performances via linear matrix inequality (LMI) conditions. All these features are studied via the state feedback trajectory control design of the translational oscillations with an eccentric rotational proof mass actuator system. The trajectory tracking capability for various tracking commands is optimized here by decay rate LMI conditions. Constraints on the output and control of the closed-loop system are also considered by LMI conditions. We present numerical simulations of the resulting closed-loop system to validate the control design

Development of micromanipulator and haptic interface for networked micromanipulation

Telemicromanipulation systems with haptic feedback, which are connected through a network, are proposed. It is based on scaled bilateral teleoperation systems between different structures. These systems are composed of an original 6 degree of freedom (DOF) parallel link manipulator to carry out micromanipulation and a 6-DOF haptic interface with force feedback. A parallel mechanism is adopted as a slave micromanipulator because of its good features of accuracy and stiffness. The system modeling and control of the parallel manipulator system are conducted. Parallel manipulator feasibility as a micromanipulator, positioning accuracy and device control characteristics are investigated. A haptic master interface is developed for micromanipulation systems. System modeling and a model reference adaptive controller are applied to compensate friction force, which spoils free motion performance and force response isotropy of the haptic interface. These systems aim to make the micromanipulation more productive constructing a better human interface through the microenvironment force and scale expansion.

Fuzzy Controllers With Maximum Sensitivity for Servosystems

In this paper, new Takagi-Sugeno proportional-integral-fuzzy controllers (PI-FCs) to control a class of servosystems are proposed. The controlled plants in these control systems (CSs) are of integral type. In the first phase, there are designed linear PI controllers tuned in terms of the extended symmetrical optimum method to ensure the imposed overshoot and settling time with respect to the set point and to three possible types of load disturbance inputs. The connections between the two design parameters of the linear controllers and the desired maximum sensitivity and complementary sensitivity considering one of the disturbance inputs are derived. Then, accepting the approximate equivalence between the fuzzy controllers and the linear ones in certain conditions and using the modal equivalence principle, an attractive design method for the PI-FCs is proposed. With this respect, the design method guarantees maximum imposed sensitivity and complementary sensitivity for the CSs and, therefore, good responses with respect to modifications of the set point and of the disturbance inputs, and robustness with respect to model uncertainties. An application in speed control of a nonlinear servosystem with variable load, accompanied by experimental results, is provided to validate the new results, the fuzzy controllers, and a design method

Fuzzy inversion and rule base reduction

This paper proposes a new design method based on linguistic model inversion and fuzzy rule reduction using singular value decomposition. Firstly, a piecewise linear fuzzy approximation of the controlled plant is identified by measurement. Secondly, the linear cells of the fuzzy model is inverted to achieve a controller. The inversion increases the fuzzy rule base. Thirdly, the redundant or small weighted information are removed from the fuzzy rule base. Experimental results of a transputer controlled single-degree-of-freedom motion control system are presented. The experimental system consists of a conventional DC servo gear motor with encoder feedback and variable inertia load coupled by a relatively rigid shaft.

Determination of Different Polytopic Models of the Prototypical Aeroelastic Wing Section by TP Model Transformation

The Tensor Product (TP) model transformation is a recently proposed technique for transforming given Linear Parameter Varying (LPV) models into polytopic model form, namely, to parameter varying convex combination of Linear Time Invariant (LTI) models. The main advantage of the TP model transformation is that the Linear Matrix Inequality (LMI) based control design frameworks can immediately be applied to the resulting polytopic models to yield controllers with tractable and guaranteed performance. The effectiveness of the LMI design depends on the type of the convex combination in the polytopic model. Therefore, the main objective of this paper is to study how the TP model transformation is capable of determining different types of convex hulls of the LTI models. The study is conducted trough the example of the prototypical aeroelastic wing section.

Sliding mode based disturbance observer for motion control

The main contribution of the paper is a sliding mode based design of a discontinuous disturbance observer used in feedback compensation of parameter uncertainties and exogenous disturbances. The experimental system is a DSP controlled single-degree-of-freedom motion control system, it consists of a conventional DC servo motor with harmonic gear and encoder feedback. The inertia load is coupled by a relatively rigid shaft. With the help of the proposed disturbance compensation, the servo system is forced to track a reference model. The relatively big parameter perturbation, external disturbance and friction are estimated and compensated. Experimental results are presented.

Parallel Distributed Compensation Based Stabilization of A 3-DOF RC Helicopter: A Tensor Product Transformation Based Approach

This paper presents a control solution for the stabilization of the 3-DOF RC helicopter via the combination of the TP (Tensor Product) model transformation and the PDC (Parallel Distributed Compensation) control design framework. First we recall the nonlinear model of the RC helicopter and its simplified version, in order, to facilitate control design. Then we execute the TP model transformation on the simplified model to yield its TP model representation, that is a kind of polytopic model with specific characteristics, whereupon the PDC framework can immediately be applied. The control design considers practical control specifications such as: good speed of response and physical constrain on the control effort to avoid actuator saturations. We guarantee these specifications by LMI (Linear Matrix Inequality) conditions developed under the PDC frameworks. Further, we avoid the discrepancies, introduced via the simplification of the model, by applying LMI conditions specialized for robust control. By simultaneously solving these LMI conditions, we render a stabilizing nonlinear controller that achieves good speed of response with small control effort without actuator saturations. Simulation results are included to validate the control design. It will be pointed out that the resulting controlleris equivalent with the controllersuccessfully applied in the real control experiment of the helicopter presented in a recent paper. The main conclusion of this paper is, that the proposed design process is systematic, non-heuristic and straightforward, the stability proof of the resulting controller is tractable via the feasibility test of LMIs and, hence, exact. The whole design procedure is automatically computed via commercialized mathematical tools (MATLAB LMI Toolbox) without analytical interaction. The computational time is about minutes on a regular PC.

Control of an Embedded System via Internet

This paper presents our experience with a complete multimedia educational program of dc servo drives for distant learning. The program contains three parts: animation, simulation, and Internet-based measurement. The animation program helps to understand the operation of dc motors as well as its time- and frequency-domain equations, transfer functions, and the theoretical background necessary to design a controller for dc servo motors. The simulation model of the dc servo motor and the controller can be designed by the students based on the animation program. The students can also test their controllers through the Internet-based measurement, which is the most important part from an engineering point of view. Students can then perform various exercises such as programming the D/A and A/D cards in the embedded system and designing different types of controllers. First, a simple PI controller can be designed, but advanced students can also design more sophisticated controllers such as the sliding mode controller. After the measurements are executed, the students can download the measured data and compare them to the simulation results.

Vibro-tactile feedback for VR systems

Today, in production engineering we have already taken into usage complex virtual representations of the manufacturing environment were we can program, simulate, analyse and optimise key performances. Such systems are mainly working through keyboard/ mouse input while user feedback normally are direct visual through computer screen and text files. Such communication only relays on a limited spectre of our senses and the keyboard/mouse/screen systems cannot be said to be very human friendly, especially when the operator is expected to operate “out of office” in a unstructured, maybe dangerous or dirty, environment. In the near future we expect to see more advanced input/output devices like motion capturing and speech input systems while feedback will not be visual alone but include several other human senses. Combinatorial sensory information, interpreted by the human brain, becomes very handy when a stand alone sense is not enough to interpret the actual situation. Imitation of senses and feedback from virtual reality environments always meant a great problem. Realization of two (sight and hearing) out of the five human senses is indispensable. Simulation of these two senses is not complex issue; on the contrary the other three are quite challenging. This paper describes the development of a vibro-tactile glove which can provide sensory feedback from a virtual environment, either as a stand alone system but most important in combination with sight and audio feedback systems. Instead of implementing real force feedback, the focus is on tactile sensing, as an alternative way of achieving the same feedback. The glove contains six vibration motors on different locations on the hand. These locations include all five fingers, and the palm. Communication with the glove is wireless, enabling free movement for the user. The system is low cost and very small sized which allows for combining it with advanced input devices like a motion capturing suit.