Study On Inverse Compensation Of Hysteretic Nonlinearity Of Actuators In Vibration Control

Actuators are the link between the controller and the controlled object, they can change instructions produced by the controller into controlling force or torque which could be applied to the controlled system to achieve control. Piezoelectric actuator which could be used in active vibration control has a prominent advantages, however, due to the characteristics of the piezoelectric material itself, the response of piezoelectric actuator to the outside applied electric field usually presents multi-valued mapping hysteresis. The hysteresis will produce harmonic distortion associated with the input signal. On the one hand it will cause system oscillation or even instability, on the other hand it will produce harmonics which will limit the system performance. From the control point of view, the characteristics of the hysteresis nonlinearity systems that are multi-valued mapping, memory and non-classical smoothness make it difficult for the commonly used control theory and modern control theory to effectively implement. To the hysteresis nonlinearity problems of piezoelectric actuators, based on previous studies, the paper dedicated to the research on the active vibration control of the system which has been introduced the hysteresis inverse compensation. The main contents include:First of all, with the background and significance of the research, the paper summarizes the overview of the hysteresis nonlinear model and active vibration control technology from home and abroad, and introduces the contents of this thesis.Chapter 2: This chapter analyze the influence of the system stability according to Preisach models, and on this basis, this chapter analyzes hysteresis nonlinear effects on the stability margin considering the delay in speed, acceleration and force feedback, which provides basic understanding when consideing the vibration control of hysteresis nonlinearity.Chapter 3: With deeply researching the theory of the classical Preisach model, and then analyzing the rule of motion point of hysteresis nonlinear curve, the affine transformation method (geometrical transformation or continuous transformation) is utilized to construct a hysteresis nonlinear model, and theory is given to prove that the proposed model forms a one-to-one relation between the input and the output, and it can be called as elementary hysteresis model (EHM). Based on the EHM, using the approximation ability of neural networks, this section constructs a neural network hysteresis nonlinear model which can adapt any classes of hysteresis nonlinearity and any signals satisfying an assumption, so it can be taken as hybrid model of neural network (HNNM). In order to validate the effectiveness of the proposed HNNM, in term of the theory of the classical Preisach model, several types of backlash-based simulation hysteresis model (BHSM) are constructed. Moreover, the proposed EHM can fully match with a type of BHSM. At last the results of simulation indicate that the proposed approach is simple and effective.Chapter 4: According to process of hysteresis nonlinear modeling in Chapter 3, this chapter will introduce the inverse model of hysteresis nonlinearity into the control system to implement adaptive control of the vibration system. And the algorithm is embedded with online frequency estimators and tracking filters. Frequency estimation is realized on the subspace identification principal and the recursive computation of correlation series of reference signals. Center frequencies of the tracking filters are adjusted according to the estimated frequencies so that the filters can track signal components. At last simulation results are given to demonstrate the superiority of hysteresis nonlinearity model and the adaptive method.Chapter 5: This chapter will present the experimental system with hysteresis nonlinear compensation on the actuator to verify the influence on the control. The experimental system includes an elastic rod with internal piezoelectric actuator, vibration sensor, amplifiers, data-acquisition card and so on. Control algorithm is achieved by Labview program, and the output signal drives the piezoelectric actuator after passing data-acquisition card and power amplifier to produce quits vibration wave. Experimental results show that the result of the vibration response after introduction of hysteresis nonlinear compensation to the vibration system is better than not taking into account hysteresis nonlinear characteristics, in which the high-order harmonic wave is inhibited obviously.Chapter 6: Finally the conclusions and contributions of this thesis are summarized and highlighted. Moreover, some problems for further study are suggested as well.