Research On Piezoelectric Self-sensing Micro-gripper Based On The Integral

In order to design a small, convenient disassembly, safe and reliable piezoelectric micro-gripper, which had displacement and clamping force self-sensing, based on structural design,carried out the corresponding finite element analysis, researched self-sensing characteristics basedon integrator circuit, conducted experimental study of piezoelectric micro-gripper designed byauthorFirst, taking cantilever bending theory, deduced the output characteristics of micro-gripper,that is：function of the clamp between the displacement and voltage. The difficulty ofpiezoelectric self-sensing micro-gripper realizing self perception is decoupling of implementationsignal and the sensing signal, this paper used integral method for piezoelectric actuator to extractedof free charge on piezoelectric ceramic wafer surface, and established a bimorph piezoelectricceramic actuator input output model, determines the function between input variable and the outputvariables. Finite element static analysis indicate that: the micro-gripper in200V maximum drivevoltage action, the fingertip produced89.1μm displacement, produced±0.02441MPa stress in theroots,and the micro-gripper resulting shows：relationship between displacement and drivingvoltage are the linear,, relationship between stresses and driving voltage are same linear. Dynamiccharacteristics analysis of micro gripper shows that： the inherent frequency is47Hz, responsetime is1.6ms.Then, conducted a great deal of experiments, obtained the static and dynamic characteristicsof micro-gripper designed by this paper, and verified the feasibility of the self sensing method.First, the static displacement test of micro-gripper was conducted by using eddy currentdisplacement sensor, experimental results show that: the maximum output displacement of thepiezoelectric micro-gripper clamp is73μm, the maximum nonlinear error is6.7%, the hysteresiserror is15.87%, the repeatability error is4.67%. The nonlinearity and hysteresis error ofpiezoelectric micro-gripper is mainly caused by the piezoelectric ceramic wafer. In the dynamiccharacteristics: the piezoelectric micro-gripper output spectrum analysis was conducted by usingthe spectrum analyzer, the results show that the natural frequency of piezoelectric micro-gripper is67Hz. Second, self-sensing experiment of micro-gripper displacement at non-clamping state wasconducted. The results show that, under driving of quasi static or lower frequency driving voltage,the measured charge curve of integral circuit can well describe the micro-gripper outputdisplacement. Visible, using integral circuit for piezoelectric ceramic wafer on the free chargeintegral method, the circuit and the regulation of self sensing signal is easy to get. Third, self- sensing experiment to a clamping force when the micro-gripper at clamping state was conducted.Using the derivation of the piezoelectric ceramic bimorph actuator model between input and output,decoupled the implementation signal and the sensing signal, the clamping state sensing micro-gripper output displacement and output force at the same time. Finally, the clamping force micro-gripper was calibrated by using precision electronic balance, experimental results show that: themaximum output force, driven by the maximum driving voltage, one micro-gripper clamp canoutput5.2g (about0.052N) clamping force, and the sensitivity of clamping output force is2.6mN/V.In summary, the design of the micro-gripper not only has good gripping effect, but also has agood self-sensing effect without any external sensor.