Research On Pneumatic Spiral Driven Pure Torsional Soft Robotic Module

Due to inherent flexibility,low-morphology structure,high-energy weight ratio,able to adapt to the complex environment through the active or passive deformation and friendly operation,soft robots have broad application prospects in the medical,rehabilitation,industrial robots,detection,bionic and other fields,making up for the shortcomings of rigid robot.At present,soft robots have become a hot topic in robotic research,but they are still in the initial stage for the reason that there are many problems to be solve in flexible materials,structural design,manufacturing process,kinematics and dynamics modeling and control.So that,it has important scientific significance to carry out related research.The bending actuators have been concerned and widely studied,while there are few studies on the torsional actuators.The torsional robots have the ability to realize the specific pose quickly and increase the flexibility in limited space.Therefore,it is necessary to study the soft twist actuator.This paper has proposed a new pneumatic driven pure torsional soft module and studied them from five aspects: design,preparation,kinematics modeling,control system design and experimental design.Firstly,based on the principle of spiral twisting,a spiral actuator module is designed,which can provide large angle pure torsional motion and easy to control.The strain energy density function is used to describe the stress-strain relationship of the hyper-elastic material.Based on the Abaqus finite element analysis technique,the influence of the geometrical parameters of the soft module on the torsional performance is analyzed.Then,the design of soft geometric parameters is optimized.On this basis,the preparation of the torsional actuator module is completed.Secondly,the kinematic analysis of the soft torsional module is carried out.According to the incompressible nonlinear flexible material and the Rivlin method,the kinematic mapping relationship between the driving pressure and the torsion angle is established by combining the virtual work principle and the elastic strain energy.The kinematic model with high precision is obtained by numerical simulation and experimental correction.which can be used for the control of the module.Then,based on the modular design,stepper drive mechanism is designed and a control system is set up.Based on the air pressure feedback,the PID control method is used to realize the continuous adjustment of the air pressure,the inflation rate and the flow rate.Based on Vox CAD software and QT + VS,a human-computer interaction and drive control system have been developed,which can be used for motion control and trajectory planning.Through the Ethernet interface and CAN bus cascade way,the scalability of multi-drive control is achieved.Finally,a multi-channel soft robotic driving control platform is built,and the prototype experiments of the soft torsional module is carried out.A test platform is designed to measure the static characteristics such as torsion angle,torque,hysteresis,bending stiffness and so on.The trajectory planning control of the soft module is realized by the trajectory planning experiment of the torsion module and the humanoid hand.In addition,the torsional module,bending module and the elongation module are combined into soft robotic systems with different deformation function.Though experiment of the special-shaped holes assembly,the transfer in complicated stenosis of the stomach and the transfer objects by humanoid hands,the large angle and pure twisting functions of the module are verified.And the effectiveness of the control system and the trajectory planning control method are also verified.