Showing papers by "Xinkai Chen published in 2016"

Design of Implementable Adaptive Control for Micro/Nano Positioning System Driven by Piezoelectric Actuator

Abstract: The micro/nano positioning system discussed in this paper includes a piezoelectric actuator (PEA) and flexure-hinge-based positioning mechanism. Due to the existence of the hysteretic nonlinearity in the PEA and the friction in the system, the accurate positioning of the piezo-actuated positioning system calls applicable control schemes for practical applications. To this end, an implementable adaptive controller is developed in the paper, where a minimized parameterization hysteresis model is employed to reduce the computational load. The formulated adaptive control law guarantees the global stability of the controlled positioning system, and the positioning error can approach to zero asymptotically. The advantages of the proposed method making on-line implementation feasible are that the traditional inversion of the hysteresis does not need to be constructed directly; the real values of the parameters of the positioning system neither need to be identified nor measured; only the parameters in the formulation of the controller are estimated online. Comparison with the feedforward plus proportional-integral feedback control scheme is conducted and experimental results show the effectiveness of the proposed method.

A Comprehensive Dynamic Model for Magnetostrictive Actuators Considering Different Input Frequencies With Mechanical Loads

Abstract: Magnetostrictive actuators featuring high energy densities, large strokes, and fast responses are playing an increasingly important role in micro/nano-positioning applications. However, such actuators with different input frequencies and mechanical loads exhibit complex dynamics and hysteretic behaviors, posing a great challenge on applications of the actuators. Therefore, it is important to develop a dynamic model that can characterize dynamic behaviors of the actuators, including current-magnetic flux nonlinear hysteresis, frequency responses, and loading effects, simultaneously. To this end, a comprehensive model, which thoroughly considers the electric, magnetic, and mechanical domain, as well as the interactions among them, is developed in this paper. To validate the developed model, the parameters of the model are identified where the hysteresis of the magnetostrictive actuator is described, as an illustration, by the asymmetric shifted Prandtl–Ishlinskii model. The experimental results demonstrate that the comprehensive model presents an excellent agreement with dynamic behaviors of the magnetostrictive actuator.

Adaptive Control for Ionic Polymer-Metal Composite Actuators

Abstract: This paper discusses the modeling and control of the ionic polymer-metal composite (IPMC) actuators which have many promising applications in biomechatronics. A novel mathematical model in continuous-time domain of the IPMC actuator, being a stable second-order dynamical system preceded by a nonlinear hysteresis representation, is proposed. An adaptive controller is formulated for the IPMC actuator based on the proposed model. The proposed adaptive control law ensures the global stability of the controlled IPMC system, and the position error of the IPMC actuator can be theoretically guaranteed to converge to zero. The effectiveness of the proposed model and the superiority of the proposed control to the traditional proportional-integral-derivative control are verified by experimental results.

Robust Adaptive Neural Control for a Class of Time-Varying Delay Systems with Backlash-like Hysteresis Input

Abstract: This paper proposes a robust adaptive dynamic surface control DSC scheme for a class of time-varying delay systems with backlash-like hysteresis input. The main features of the proposed DSC method are that 1 by using a transformation function, the prescribed transient performance of the tracking error can be guaranteed; 2 by estimating the norm of the unknown weighted vector of the neural network, the computational burden can be greatly reduced; 3 by using the DSC method, the explosion of complexity problem is eliminated. It is proved that the proposed scheme guarantees all the closed-loop signals being uniformly ultimately bounded. The simulation results show the validity of the proposed control scheme.

Tracking control of piezoelectric actuator using adaptive model

Abstract: Piezoelectric actuators (PEAs) have been widely used in micro- and nanopositioning applications due to their fine resolution, rapid responses, and large actuating forces. However, a major deficiency of PEAs is that their accuracy is seriously limited by hysteresis. This paper presents adaptive model predictive control technique for reducing hysteresis in PEAs based on autoregressive exogenous model. Experimental results show the effectiveness of the proposed method.

High precision motion control of piezo-actuated stages using discrete-time sliding mode control with prescribed performance function

Abstract: In this paper, high precision motion control of piezo-actuated stage is discussed. In order to cope with the nonlinear characteristic of the piezoelectric actuator (PEA) and get high tracking performance, this paper proposes a new approach to design the discrete time sliding mode control (DSMC) with an ability to maintain the tracking error in a known region described by a performance function. The effectiveness of the proposed method is verified by experiments. The results show that the system not only performs well with complicated desired trajectories but also robust against external disturbances.

Nonlinear discrete prescribed performance control for micro-positioning of smart actuators

Abstract: Most smart material based actuators (smart actuators) are known for their prominent characteristics of a high resolution of positioning, high bandwidth, and the ease of integration in miniaturized systems. However, their applications are restricted by the inherent hysteresis nonlinearity. This paper presents a new nonlinear discrete control design to improve hysteresis compensation in the smart actuators particularly in the piezoelectric based actuators. The control development takes the prescribed performance control framework as the basis and fuses it into a new modified Bouc-Wen (MBW) model. Through the theoretical analysis, it is shown that the designed control law guarantees the stability of the closed-loop system. Finally, the efficacy of the control framework is verified via a real case application where a linear piezoelectric actuated positioning system (PEA stage) is used as the testbed. The experimental results confirm that the formulated control scheme has the capacity for improving the output-tracking performance in the PEA stage.

An extended Bouc-Wen model based adaptive control for micro-positioning of smart actuators

Abstract: Most smart material based actuators (smart actuators) are known for their prominent characteristics of high resolution of positioning, high bandwidth, and the ease of integration in miniaturized systems. However, their applications are restricted by the inherent hysteresis nonlinearity. This paper presents a new modified Bouc-Wen (MBW) model which has a rate-dependent property. Then the proposed model is directly used in developing a robust adaptive control in order to eliminate the hysteresis effects. Finally, the efficacy of the designed control framework is verified via a real case where a giant magnetostrictive actuator (GMA) is used as the testbed.

Control fusion strategy via differential equations based hysteresis operator

Abstract: Hard nonlinearity or hysteresis effect is the main obstacle in most smart material based actuators which makes their optimal usage impossible. Thus, it is essential to develop a comprehensive strategy for modeling and control in order to mitigate this hysteresis nonlinearity. This paper investigates the viability of the differential equations based models towards hysteresis characterization and control fusion strategy in order to solve the tracking problem in the piezoelectric-based actuators. The analytical and simulation results suggest that this category of model is simple to use and has clear physical meanings. More importantly, it is established that only Bouc-Wen (BW) model has the ability to be synthesized directly into the control design. Finally, a control strategy is devised based on BW model and is experimentally verified in the discrete-time domain.

Robust Control for Magnetostrictive Actuators

Abstract: The hysteresis phenomenon exists in magnetostrictive actuators. When the hysteresis nonlinearity exists in a controlled system, the system usually exhibits inaccuracies or oscillations and even instability due to the undifferentiable and nonmemoryless character of the hysteresis. This paper proposes the robust control in broadband for magnetostrictive actuators, where the hysteresis is described by the Preisach model.