Research On Impedance Control Of Electrothermal Actuators For Micromanipulation

Micromanipulation refers to the method of manipulating micro-scaled objects,and is the key technology to drive the development of the technologies in MEMS,semiconductor,biology,and medicine.The actual effect of micromanipulation is directly determined by the performance of the manipulation tools.A manipulation tool is usually constituted by actuators and manipulators,and the dynamic performance of a micromanipulation tool is determined by the actuators,its core components.The response speed and the dynamic characteristics of actuators usually cannot meet the requirements of complicated manipulation tasks.Therefore,the appropriate control system needs to be designed to improve the dynamic performance of the actuators to promote the efficiency and effect of micromanipulation.However,most of the current research efforts on the control of actuators focus on the positon control,few research efforts have been put toward the interaction between the actuators and their environment.As a result,the applications of micromanipulation are limited.In this thesis,the impedance control is employed to regulate the dynamics of electrothermal actuator as desired to improve the interaction behavior of manipulation tools,and hence to facilitate the development and application of micromanipulation techniques.The main work of this thesis is presented as follows.(1)The transfer function model of the electrothermal actuator is established,and the detailed analyses are conducted toward the response characteristics,steady-state error,stability,and frequency response of the feedback control system.Based on the results of these theoretical analyses,the proportional feedback controller,proportional-derivative controller,and feedforward controller are designed to improve the position response of actuator,which is the foundation for the implementation of impedance control.(2)The proper implementation strategy of impedance control is determined in consideration of the characteristics of electrothermal actuators.The design and implementation methods of impedance controller are presented in details.Simulations and experiments are performed to verify the capability of impedance control to achieve the desired interaction during micromanipulation.The influences of different impedance parameters on the interaction performance are discussed and compared,to provide a guidance on the selection of impedance parameters for a specific task.(3)The corresponding operating software is developed for the cell manipulation platform.With this operating software,the camera,movable stage,manipulators,driving power and other relevant devices in this platform can be controlled coordinately to realize the functions such as image real-time display,motion control,discrete sampling,digital impedance controller,and data output for experiments.(4)The transfer function model of electrothermally-actuated microgripper is established and the parameters in this model are identified.The response characteristics of this gripper and the effects of impedance parameters on the cell grasping are analyzed and demonstrated by experiments.Finally,the impedance controller of gripper is implemented to achieve the compliant cell grasping.