Adaptive-gain fast nonsingular terminal sliding mode for position control of a piezo positioning stage

Author(s):  
To Xuan Dinh ◽  
Kyoung Kwan Ahn

This article proposed a variable gain fast terminal sliding mode controller with an estimator of the uncertainty model for a piezo positioning stage system. The designed terminal sliding mode control has some advantages over the linear sliding mode control such as fast convergence and chattering reduction while maintains its robustness to the uncertainties. Next, an indirect technique is developed to enable the elimination of the singularity problem corresponding to initial terminal sliding mode control. In addition, a cerebellar model articulation controller is carried out to estimate the nonlinear dynamics of the piezo positioning stage. To deal with unknown bounds of uncertainties and disturbances, the proposed scheme consists of using online tuning control gains that ensure the establishment of a real terminal sliding mode in a finite time. Moreover, a fuzzy logic scheme is presented to smooth out the discontinuity part of the control signal, hence improve the control performance. Stability analysis of closed loop system is provided using the Lyapunov function method. Experiment results are presented to evaluate the effectiveness of the designed control approach.

2019 ◽  
Vol 52 (5-6) ◽  
pp. 720-728
Author(s):  
Huawei Niu ◽  
Qixun Lan ◽  
Yamei Liu ◽  
Huafeng Xu

In this article, the continuous integral terminal sliding mode control problem for a class of uncertain nonlinear systems is investigated. First of all, based on homogeneous system theory, a global finite-time control law with simple structure is proposed for a chain of integrators. Then, inspired by the proposed finite-time control law, a novel integral terminal sliding mode surface is designed, based on which an integral terminal sliding mode control law is constructed for a class of higher order nonlinear systems subject disturbances. Furthermore, a finite-time disturbance observer-based integral terminal sliding mode control law is proposed, and strict theoretical analysis shows that the composite integral terminal sliding mode control approach can eliminate chattering completely without losing disturbance attenuation ability and performance robustness of integral terminal sliding mode control. Simulation examples are given to illustrate the simplicity of the new design approach and effectiveness.


Author(s):  
Zeeshan Anjum ◽  
Yu Guo ◽  
Wei Yao

In this paper, the problems of tracking control and finite-time stabilization of a high nonlinear system such as a robotic manipulator in the presence of actuator faults, uncertainties, and external disturbances are explored. In order to improve the performance of the system in the presence of actuator faults, uncertainties and external disturbances a novel fault tolerant control system based on fractional-order backstepping fast terminal sliding mode control is developed in this paper. The control system is developed by employing the results obtained from studies in the fields of fractional-order calculus, backstepping, sliding mode control, Mittag–Leffler stability, and finite-time Lyapunov stability. The performance of the suggested controller is then tested for a PUMA560 robot in which the first three joints are used. The simulation results validate the usefulness of the developed control approach in terms of accuracy of tracking, and convergence speed in the presence of disturbances, uncertainties and actuator faults. The trajectory tracking performance of the developed method is compared with other state of the art approaches such as conventional computed torque control, proportional integral derivative control and nonsingular fast terminal sliding mode control. The simulation results show that the proposed control approach performed better as compared to other control approaches in the presence of actuator faults, uncertainties, and disturbances.


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