Tracking Control Of 3-RRR Parallel Piezo-stage Using Position Domain Control Strategy

Piezoelectric materials are commonly used as an actuator (PEA for short) for stage systems which are expected to perform micro-memter motions for both positioning and tracking applications (piezo-stage for short). There are two challenges in controlling piezo-stages. The first challenge is that piezoelectric materials as actuators have a constitutive property which has a non-linear and load-dependent hysteresis. The second challenge is coupling among multi-PEAs. The second challenge is aggravated by the first challenge while the first challenge stands out with respect to the second challenge, which highly limit positioning accuracy and trajectory tracking performance of micro platform.The object of the research is to (1) establish the PEA hysteresis dynamic model based on Bouc-Wen hysteresis model that describe the hysteresis nonlinearity of piezoelectric material. (2) consider the coupling of multi-PEAs, put forward the control model based on the inverse Bouc-Wen feedforward compensation and PI feedback hybrid control method in the position domain.(3) validate the effectiveness of the proposed method by system simulation and experiment.Firstly, determine the mathematical model of PEA by the hysteresis dynamic model using parameter identification method. Secondly, Kinematics analysis, kinematic simulation and work space solution by the pseudo-rigid-body model. Thirdly, design the trajectory tracking control method of micro platform based on position domain control, the result will be compared with traditional time domain control method. Finally, system simulation and experimental validation about the proposed method.The conclusion of the research is that (1) the hysteresis nonlinearity of PEA is inevitable, Bouc-Wen hysteresis model can effectively describe the piezoelectric hysteresis phenomenon. (2) the theoretical work space and the actual working space is put in bigger difference, which cause in many reasons such as micro platform design, manufacturing, assembly errors and so on.(3) the proposed method for feed-forward control is more effective in improving tracking performance when compared with traditional time domain control.