Chyun-Chau Fuh

Application of voice coil motors in active dynamic vibration absorbers

A dynamic vibration absorber reduces the influence of a force whose excitation frequency nearly coincides with the natural frequency of a rotating machine. However, the performance of this type of passive absorber can be affected by changes in the environment. In this paper, we describe a voice coil motor (VCM) that can serve as the actuator in an active dynamic vibration absorber which can be regulated for different conditions. With a VCM, suitable controllers can be designed for periodic excitation force rejection by using the characteristics of the notch filter in combination with the root-locus theorem. We have evaluated the performance of the active vibration absorber by both simulations and experiments.

A robust controller for chaotic systems under external excitation

Abstract We show that one can control a chaotic system under external force excitation to arbitrary trajectories, even when the desired trajectories are not located on the embedded orbits of a chaotic system. The method utilizes a newly developed sliding mode controller with a time-varying manifold dynamic to offer a feedback control in compensation with the external excitation, and drive the system orbits to desired states. The proposed controller does not need high gain to suppress the external force, and meanwhile, keeps robustness against parameter uncertainty and noise disturbance as does the traditional sliding mode control. Simulations are provided to illustrate the performance of the controller.

Control of discrete-time chaotic systems via feedback linearization

Abstract An approach for controlling discrete-time chaotic systems by feedback linearization is proposed. This method can not only stabilize unstable periodic orbits embedded in a strange attractor, but also can be applied even if the real trajectory is far from the target one. A Henon map with different operation conditions is implemented to demonstrate the feasibility of the proposed method.

EXPERIMENTAL AND ANALYTICAL STUDY OF DITHER SIGNALS IN A CLASS OF CHAOTIC SYSTEMS

Abstract A method for controlling a class of chaotic systems by injecting another external input, called a dither signal, into the systems, just ahead of the nonlinearities is given. The method is robust to measurement noise due to no state being fed back and applicable to experimental situations in which the system parameters are unknown and unalterable. Two numerical examples and one experimental test are performed to demonstrate the feasibility of the method.

Robust control for a class of nonlinear oscillators with chaotic attractors

Abstract An approach using the sliding mode control theory to control a class of nonlinear oscillators with a chaotic attractor is presented. It can control chaotic motion not only to a steady state but also to a desired periodic orbit. Especially, the method is easy to implement and does not require the exact dynamics model in advance.

Suppression of Hunting in an ILPMSM Driver System Using Hunting Compensator

This paper presents the suppression of hunting in an ironless linear permanent-magnet synchronous motor (ILPMSM) driver system using a hunting compensator. In high-precision motion control servo systems, hunting induced by nonlinear elements such as friction and saturation will reduce the system performance. Hunting means that limit cycle occurs in the system, causing a series of sustained oscillations. The hunting compensator is designed based on the circle criterion to ensure system stability. The effectiveness of the proposed control scheme is verified by simulation and experimental results. The proposed algorithm is experimentally tested on an ILPMSM drive system, and the experimental results confirm the ability of the hunting compensation scheme to suppress the effects of hunting.

A Robust Uncertainty Controller With System Delay Compensation for an ILPMSM System With Unknown System Parameters

A robust uncertainty controller with a system delay compensation for an ironless linear permanent-magnet synchronous motor (ILPMSM) system with unknown system parameters has been investigated. The proposed controller consists of an inverse of the first-order reference model with an input deduction and integral term. The system delay compensation adopts an inverse system delay model to compensate the system transport delay effect. The proposed control scheme can reduce modeling uncertainty due to the difference between the reference model and the unknown real system model and disturbance due to d-q-axis coupling effect. The advantages of the proposed control algorithm are as follows: First, the system response which can be achieved is similar to that of the designed nominal reference model. In other words, the dc gain of the controlled system is denoted as one, so the proposed algorithm does not need to be combined with other control algorithms. Second, it does not require the system parameters to be known precisely. Our experimental results confirm the feasibility of the proposed scheme to compensate for the effects of uncertainty disturbances and system transport delay in the practical application of an ILPMSM system with unknown parameters.

Absolute stability analysis for a class of Takagi-Sugeno fuzzy control systems

This article presents absolute stability conditions for a particular class of Takagi–Sugeno fuzzy control systems. Initially, a Takagi–Sugeno fuzzy control system is transformed into a multivariable Lur’e type system. A simple algorithm for checking the absolute stability of this system is then proposed. Since the key of the proposed algorithm is to solve algebraic Riccati equations, software packages such as MATLAB provides a simple means to check the conditions. The proposed approach does not limit the methods of fuzzification and defuzzification. This article presents several analytical examples to verify the simplicity and efficiency of the proposed approach.

A Combined Input-state Feedback Linearization Scheme and Independent Component Analysis Filter for the Control of Chaotic Systems with Significant Measurement Noise

Chaotic motion is an undesirable phenomenon in many engineering applications since it leads to a significant degradation of the system performance and restricts the feasible operational range. Therefore, the problem of controlling or suppressing chaos has attracted considerable attention in the literature. However, most chaos control schemes utilize a state feedback signal, and are therefore sensitive to measurement noise. Therefore, a requirement exists for filtering systems capable of separating the measurement noise from the chaotic signal in order to improve the performance of the controlled system. However, the chaotic signal and the measurement noise are both broadband signals, and thus the measurement noise can not be filtered using a low-pass filter since this causes a distortion of the chaotic signal. Accordingly, this paper presents a control scheme for chaotic dynamic systems with significant measurement noise featuring an input-state linearization scheme and a filter based upon an independent component analysis algorithm. The feasibility and effectiveness of the proposed approach are demonstrated by way of numerical simulations using a general Lorenz system for illustration purposes.

Development of an automatic arc welding system using an adaptive sliding mode control

This paper develops an automatic welding control scheme for alternating current shielded metal arc welding (SMAW) system. A mathematical model of the welding control system is derived and the system parameters identified. An adaptive sliding mode controller is designed to estimate the bound of the system uncertainties and to modulate the electrode feed rate in such a way that the desired arc length and arc current are maintained as the electrode melts during the welding process. The proposed control method is suitable for any consumed electrode welding technique. The simulation and experimental results show that the automatic welding control system successfully maintains the magnitude of the arc current at the desired value and preserves the arc stability, thereby obtaining an enhanced SMAW control system performance.