| Piezo-stack actuator is widely used for micro/nano positioning and manipulating due to its high resolution,high stiffness,and short response time.However,the stroke of the piezoelectric stack is at most 0.1% of the length of the piezoelectric stack which limits its application range.To address this issue,the displacement amplifier is commonly used to amplify the stroke of the piezo-stack actuator.Based on the analysis of the characteristics of bridge-type amplifier and lever-type amplifier,this paper designs a bridge-lever-type amplifier,which can produce a larger amplification with a compact structure.At the same time,the performance of the mechanism is modeled and analyzed.While the bi-stable phenomenon exists in the amplifiers will influence the load of the amplifier during the actual use.The phenomenon of the mechanism is modeled to solve the jump threshold and the above analysis are combined to optimize the mechanism.Finally,Iterative Learning Control(ILC)is used to control the bridge-lever-type amplifier.Firstly,the relationship between the force and displacement of the flexible hinge is analyzed.The static model of the mechanism is established by the compliance matrix method,and the natural frequency of the mechanism is calculated by the Lagrange equations,which the model calculate the amplification and natural frequency can be obtained.The accuracy of the mathematical model is verified by FEA and experiment.The bi-stable phenomenon exists in the amplifiers is found during the experiment of measuring the amplification of the bridge-lever-type amplifier.The existence principle of the e bi-stable phenomenon is analyzed,the common methods for solving the nonlinear problems of large deflection beams are analyzed and the elliptic integral model is selected to model the leaf flexure hinge.the bi-stable model of the bridge-lever-type amplifier is obtained by combining the kinematics and force analysis of the mechanism.The accuracy of the mathematical model is verified by FEA and experiment.After the FEA of the whole mechanism,it is found that the performance of the mechanism cannot satisfy the actual application requirements,so through the analysis of a variety of multi-objective optimization strategies,the multi-objective optimization analysis of the mechanism is carried out by using the method of Matlab and FEA simulation,and the structural parameters that satisfy the actual application requirements are selected from the Pareto solution set.Finally,aiming at the hysteresis of the bridge-lever-type amplifier in the experiment,a high-order iterative learning control strategy is proposed which avoids the complex problem of solving model when traditional inverse compensation of hysteresis model is adopted,and the influence of hysteresis nonlinearity on the output displacement of bridge lever amplification mechanism is eliminated. |
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