Search

This article presents the design, control, and test of a piezo-based passive compliant micro-gripper capable of combining position and force control. The gripper's structure is compact due to a super-large amplification ratio of 52 that is achieved by a two-stage displacement amplifier. The position/force switching control strategy is utilized for the position and force regulation. Particularly, a dual feedforward controller combining Gaussian process regression based hysteresis compensator and input shape technique based vibration suppressor is employed to the position regulation, while a hybrid controller composed of dual feedforward and PID feedback is used for the precision force control. Compared to the conventional design, the system is simplified because displacement sensor is removed. In order to protect the micro-object from contact, the passive compliance design method is introduced to the gripper tip. An experimental study, executing grasp-hold-release operations of a gold wire, is carried out to validate the feasibility of the gripper system. The result confirms that the proposed scheme is feasible and the stable clamping operations can be achieved. [ABSTRACT FROM AUTHOR]

This paper proposed a feedforward-feedback (FF-FB) control strategy for a linear piezoelectric walking stage (LPWS) based on the parameter-dependent Bouc-Wen (PD-BW) model under condition variations. The mathematical model of LPWS is established by linearization, which consists of a linear system and a hysteresis nonlinearity system. The linear dynamics model of LPWS is identified by the swept-sine method, whereas the hysteresis nonlinearity model of LPWS is identified based on the PD-BW model. The feedforward controller based on the inverse PD-BW model can compensate for the inherent hysteresis nonlinearity of LPWS at varying excitation frequency, surrounding temperature, and external load. A proportional plus lead-lag feedback controller is built to reduce feedforward modelling error and improve the output accuracy of LPWS. The sensitivity analysis of the LPWS feedback control system is performed to reduce the effect of disturbance and noise. Experimental results present the feasibility and effectiveness of the proposed FF-FB control strategy to achieve an efficient and accurate positioning performance. • A feedforward-feedback control method based on the parameter-dependent Bouc-Wen model is applied to a piezoelectric stage. • The proposed parameter-dependent Bouc-Wen model compensates for the hysteresis of piezoelectric actuators under varying conditions. • The sensitivity analysis is performed to achieve accurate output performance and suppress disturbance and noise. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid control strategy of a novel linear piezoelectric walking stage based on two sorts of piezoelectric actuators, which takes the load variation into account. The proposed stage consists of two parallel 4-bar lever amplification mechanisms with flexure hinges actuated by piezoelectric stacks to heighten the vertical distance (that is more tolerable to the assembly discrepancy), two compression springs (that is able to maintain a fixed linear position without powering), and two shear piezoelectric actuators (that can achieve longer and equivalent to walking motion) in a small form factor. The proposed stage has two operating modes, namely a coarse positioning mode with a more extensive travel range and a fine positioning mode with a nanometer-level resolution, to possess excellent performance for the linear piezoelectric walking stage of load variations. One multimodal switching controller and one feedforward-feedback controller conduct the coarse mode and fine mode, respectively. The optimal frequency for a specific load is obtained through a backpropagation neural network in the multimodal switching control. In the feedforward-feedback control, the inverse mathematical model based on the Bouc-Wen hysteresis model is used to mitigate the hysteresis effect in the feedforward part while the proportional–integral–derivative controller in the feedback part handles the external system disturbances. Experimental results show the proposed hybrid coarse/fine mode control strategy's effectiveness to satisfy an efficient and accurate positioning task. • A hybrid control approach is applied to the linear piezoelectric walking stage actuated by two-type actuators. • The load variation of piezoelectric stages and the hysteresis of piezoelectric actuators are taken into study. • A multimodal switching controller with a backpropagation algorithm is proposed to implement efficient positioning. • A feedforward-feedback control strategy is designed to perform accurate positioning. [ABSTRACT FROM AUTHOR]