Research On A Soft Manipulator With Variable Stiffness

Soft robots are made of soft materials,theoretically have unlimited degrees of freedom,have good adaptability and human-computer interaction,and have broad application prospects in the fields of medical rehabilitation,rescue exploration,and fruit and vegetable picking.As a branch of software robot research,the soft manipulator is still in its infancy.Although it can achieve non-destructive grasping of objects,it solves the problems of poor interaction and low safety of traditional rigid manipulators,but the overall structural rigidity is low and the anti-interference ability is low.And the load capacity is poor.Therefore,this article has studied in depth a soft manipulator with variable stiffness based on laminar interference.The main research contents are as follows:Firstly,the working principle of the soft actuator and the variable stiffness structure was analyzed,and combined with the characteristics of the pneumatic drive,a variable stiffness soft manipulator based on layered interference was designed.It is composed of the soft actuator and the variable stiffness structure,in which the soft actuator provides bending action and the variable stiffness structure realizes stiffness adjustment.This paper analyzed and compared several common soft robot preparation techniques,and selected the appropriate preparation techniques to prepare the prototype.Secondly,the soft manipulator with variable stiffness was simulated and modeled.Since the soft manipulator with variable stiffness is made of hyperelastic material,the appropriate strain energy density function was selected to describe its mechanical properties,and the material parameters were obtained through tensile experiments.According to the working principle of the soft manipulator with variable stiffness,the bending characteristics of the soft actuator and the stiffness characteristics of the structure with variable stiffness were simulated by using the finite element software ABAQUS to verify the rationality of the structure design.Based on the Yeoh model,a mathematical model of the bending characteristics and the output force of the soft-actuated actuator was established,and the influence of the variable stiffness structure on the bending characteristics and the output force of the soft-actuated actuator was analyzed.Thirdly,the experimental platform of the flexible manipulator with variable stiffness is built,including the design of the gas circuit system and the design of the circuit system.The gas circuit system adjusts the size and direction of the air pressure by controlling the various pneumatic components.The circuit system mainly communicates with the upper computer Lab VIEW through the STM32 microcontroller,which is responsible for controlling the working state of each pneumatic component.The PID control principle is described,the bending Angle of the flexible manipulator with variable stiffness is controlled by PID,and the PID parameters are adjusted by trial and error method.When KP=0.12?TI=0.1?TD=0.12,the response curve of the system is the best.Finally,the bending characteristics and the output force of the flexible actuator with no variable stiffness structure and the flexible manipulator with variable stiffness were compared and analyzed respectively.The experimental results show that,when the inflating pressure range is 0?60kPa,the bending Angle of the soft actuator is 0°?108°,and the output force of the end is up to 1.36N.The bending Angle of the flexible manipulator with variable stiffness is 0°?86°,and the maximum output force at the end is 2.13N.A grasping experiment platform was built,and grasping experiments were carried out on fingertip grasping and envelope grasping,respectively.The maximum grasping force of the manipulator was compared with and without vacuum pumping,and the maximum grasping force of the manipulator bent to the outside was experimented.The experiment results show that the maximum grasping force of the flexible manipulator with variable stiffness is 11.89N,which can realize the nondestructive grasping of fragile and fragile objects.