Novel linear piezoelectric motor for precision position stage

Conventional servomotor and stepping motor face challenges in nanometer positioning stages due to the complex structure, motion transformation mechanism, and slow dynamic response, especially directly driven by linear motor. A new butterfly-shaped linear piezoelectric motor for linear motion is presented. A two-degree precision position stage driven by the proposed linear ultrasonic motor possesses a simple and compact configuration, which makes the system obtain shorter driving chain. Firstly, the working principle of the linear ultrasonic motor is analyzed. The oscillation orbits of two driving feet on the stator are produced successively by using the anti-symmetric and symmetric vibration modes of the piezoelectric composite structure, and the slider pressed on the driving feet can be propelled twice in only one vibration cycle. Then with the derivation of the dynamic equation of the piezoelectric actuator and transient response model, start-upstart-up and settling state characteristics of the proposed linear actuator is investigated theoretically and experimentally, and is applicable to evaluate step resolution of the precision platform driven by the actuator. Moreover the structure of the two-degree position stage system is described and a special precision displacement measurement system is built. Finally, the characteristics of the two-degree position stage are studied. In the closed-loop condition the positioning accuracy of plus or minus 0.5 μm is experimentally obtained for the stage propelled by the piezoelectric motor. A precision position stage based the proposed butterfly-shaped linear piezoelectric is theoretically and experimentally investigated.     

多轴亚微米级平面定位台的滑模观测器无传感控制

针对Sawyer电机驱动的平面定位台的多轴精密定位问题(X、Y和θz轴),提出了一种新的部分无传感控制方法。用激光干涉仪检测定位台一个方向上的平移运动和摆动,并构建相应的闭环控制;同时,应用滑模观测器估计另一个方向上的平移运动并构建对应轴的闭环控制。在此基础上,通过实验从开环控制、多轴全闭环控制及部分无传感控制三方面对比了定位性能。实验结果表明:采用部分无传感控制,多轴平面定位台的重复定位精度达到亚微米(0.25μm)级;部分无传感控制下的动子行程与开环控制相同(X轴300mm、Y轴300mm),远大于基于多轴位置传感的全闭环控制下的动子行程(X轴100mm、Y轴100mm);获得的结果可满足应用设计要求。