Design And Experimental Research Of A Miniature Finger-shaped Two-dimensional Precision Piezoelectric Joint

With the rapid development of robotics technology,life science engineering,precision optical engineering,etc.,the research of precision manipulation technology has become a key factor restricting the further development of the above fields.As the core components that directly affect the overall quality of the precision manipulation system,the robotic joints play a decisive role in the precision manipulation system.Therefore,how to implement the miniaturization,multi-DOF motion,high resolution and large motion range output for the robotic joints has become the focus of the robotic joint research in academic and industrial communities.As the core components of robotic joints,the actuators are critical to the output characteristics of the robotic joints.Compared with the traditional electromagnetic actuators and the emerging flexible actuators,the piezoelectric actuators hold outstanding advantages of high resolution,simple structure,self-locking when power-off,non-electromagnetic radiation and rapid response.Thus,it is of great significance to carry out the design and experimental research of a miniature multi-DOF precision joint based on piezoelectric actuator.Firstly,this thesis analyzes the “stick-slip” working principle of piezoelectric joint based on inertial drive.The basic configuration of a bonded-type piezoelectric actuator is proposed,and the excitation method for the piezoelectric actuator to realize two-dimensional rotary driving is determined.The relationship among the structural parameters of the piezoelectric actuator,exciting voltage and bending displacement on the driving foot is derived to a static model.The relationship between the main structural parameters of the piezoelectric actuator and the bending displacement on the driving foot is studied.The structural dimensions and material parameters of the bonded-type piezoelectric actuator are determined by the static simulation analysis with ANSYS software,and the availability of the established theoretical model is verified.A prototype of the bonded-type piezoelectric actuator is fabricated and its output displacement response tests are carried out to further verify the reasonability of theoretical modeling and simulation analysis results.A bearing element for supporting spherical rotor and a pre-loading mechanism are developed.The whole package of the piezoelectric joint is accomplished.The experimental prototype of the miniature finger-shaped two-dimensional precision piezoelectric joint is developed.Secondly,according to the actual driving requirements of the piezoelectric joint based on inertial drive proposed in this thesis,a specialized linear power amplifier for piezoelectric joint is developed.The specialized linear power amplifier is composed of linear voltage amplifier module and DC stabilized voltage supply module.Multisim software is used to simulate the circuit structure of each module.Altium Designer software is utilized to complete the wiring design of each circuit.The specialized linear power amplifier is manufactured and tested for its input and output characteristics.The test results show that the magnification of the specialized linear power amplifier is 19.9209;the relative error between the actual magnification and the designed magnification is 0.3955%;the ripple of the specialized linear power amplifier is less than 55.4m V;the specialized linear power amplifier can effectively amplify the sawtooth excitation signal with symmetry of 100% and 0% respectively.Therefore,the specialized linear power amplifier for piezoelectric joint developed in this thesis has obtained the characteristics of good linearity,great ripple characteristics and undistorted amplification responses to the sawtooth wave input signal.Finally,an experimental test system for miniature finger-shaped two-dimensional piezoelectric joint is built.The indirect measurement schemes for the angular displacement and output torque of piezoelectric joint are proposed.The mechanical output characteristics of the piezoelectric joint such as the speed versus voltage characteristic,the speed versus frequency characteristic,the kinematic coupling characteristic,the load characteristic and the angular displacement resolution are studied by using the established experimental test system.The test results show that: the maximum rotary velocities of the spherical rotor around X and Y axes are 1.03rad/s and 1.14rad/s,respectively,under exciting voltage of 400Vp-p and frequency of 750Hz;the coupling rates of the spherical rotor around the X-axis and Y-axis are 7.8% and 6.89%,respectively,a low motion coupling characteristic is achieved;the angular displacement resolutions of the spherical rotor around the X axis and the Y axis are 4.64?rad and 4.76?rad,respectively,high motion resolution has been achieved;the maximum load torque is 0.54N·mm.The proposed piezoelectric joint holds the advantages of miniaturization,high resolution,large motion range and two-dimensional output capability,and it has strong application potential in the fields of micro-assembly,precision pointing posture adjustment,and cell manipulation.In addition,the comparisons between the developed miniature finger-shaped two-dimensional precision piezoelectric joint and the multi-DOF piezoelectric actuators at home and abroad show that the proposed piezoelectric joint has more prominent advantages in terms of motion speed,displacement resolution,structural size and etc.