Tactile Perception And Control Research Of Electrothermal Driven LCE Soft Hand

Soft hand can not only complete flexible grasping tasks,but also reduce damage to the object.However,due to the difference between the driving mode and the characteristics of the base material,it is very difficult to achieve the integrated design of the driving and sensing,which limits the soft hand’s ability to perceive external information.At the same time,the grasping work of soft hand has higher and higher requirements on the performance of the actuator,which not only requires the stable output force from the actuator,but also requires the precise control to the actuator.In view of the above problems,this paper designs the electrothermal drive soft hand with sensing function from the following directions: actuator selection,driver research,sensor integration,structure of the soft hand and research of the control system.The main contents of this paper include:First,the strain characteristics of liquid crystal elastomer(LCE)with temperature were investigated,and a polyimide electrothermal film with good uniformity and stability was prepared for the problem of requiring stable output force for gripping work.A silicon mold was prepared by using nanoimprinting technology,and a lattice-like PDMS mold was prepared by using a silicon mold.The lattice-like polyimide electrothermal film,which can drive the liquid crystal elastomer film,was prepared by embossing photoresist and dropping multi-walled carbon nanotube solution with PDMS mold.Second,for the sensing needs of soft hands,this paper prepared resistive strain sensors and capacitive pressure sensors on the surface of liquid crystal elastomer films based on the microchannel resistive strain and capacitive pressure principles.The resistive strain sensor adopted an array microcracked channel structure,and the deformation of the microcracked channel caused the change of the overall resistance value when the finger is bent,while it was easier to integrated compared with other structures.The electrode structure of the capacitive pressure sensor is grid-like,and the material of the dielectric layer is polyurethane sponge,which is more flexible than PDMS and other silicone,which can improve the pressure sensing ability of soft hands.Considering the temperature drift effect of the sensor,the effect of temperature on the resistance value of the strain sensor was corrected by temperature compensation experiments,and the software was used to simulate the specific capacitance value by finite element simulation of the capacitive pressure sensor.Bending experiments and pressure experiments were also conducted to test the sensitivity,hysteresis,response time,and stability of the sensor.Thirdly,the soft finger unit with haptic perception ability of double-layer liquid crystal elastomer film structure was prepared,which was improved in weight-bearing performance compared with single-layer soft finger unit,the soft hand palm mold was prepared by using 3D printing technology,the soft hand palm was prepared by using PDMS,and the soft hand with gripper structure was designed by modular means,and the flexibility of the soft hand and the soft hand’s ability to grasp objects in longitudinal and lateral directions were verified.The flexibility of the soft hand and its ability to grasp objects in both longitudinal and lateral directions were verified.Finally,to address the problem that the bending angle of the soft hand cannot be precisely controlled,this paper adopted PID control and iterative method for the closed-loop control of the soft hand.The hardware control platform and software control platform of the soft hand were built,and the strain sensor was used to sense the bending status of the soft hand,and the signal was processed and output to the relay circuit through the microcontroller control program,and the solenoid valve was used to complete the control of the soft hand.The system experiments on the soft hand demonstrated the correctivity and accuracy of the control algorithm and the superior tactile perception of the soft hand.This research has outstanding applications in the fields of grasping easily deformable objects and space grasping.