Research On The Design And Control Strategy Of A Pneumatic Manipulator

It is a future trend for robots to achieve a human-robot coexistence.Safety is the most important issue to consider firstly.The pneumatic drivers has natural passive compliance because of the comprssibility of the air.The pneumatic robots driven by pneumatic drivers has higher power-to-mass ratio,good backdrivability and flexibility than the traditional robots driven by electic motors,so it is instinsically safe.Therefore pneumatic robots has the potential to be used in situation where the requirements of safety is high and requirements of speed,accuracy and rigidity is not so high.This paper proposed a pneumatic robots with safety characteristic.Firstly,based on the comprehensive comparison of the performance parameters of various types of pneumatic drivers,considering the design concept of light weight,miniaturization and modularization,a small rolling diaphragm cylinder is selected as the pneumatic driver,and a rotary joint module of pneumatic robot driven by a set of mutually antagonistic rolling diaphragm cylinders is designed.Then the performance parameters of the lightweight rotary joint module of pneumatic manipulator was calculated and a pneumatic manipulator with four degrees of freedom was designed.Secondly,the position servo control system of the joint of pneumatic robot is studied.For the various components of the pneumatic system of joint,the friction and viscous force models of the rolling film cylinder,the dynamic model,the thermodynamic model,and the mass flow model of the proportional directional valve are established respectively.The state space representation of the joint pneumatic system is obtained according to the models.Considering the complex and non-linear characteristics of the pneumatic system,a back-step method is used to design the position servo control system of the joint based on sliding mode control.Then,the kinematics analysis of the manipulator was carried out,and the compliant control system of the pneumatic manipulator was designed.The mechanical compliance control method is used to establish the relationship between the pressure in pneumatic drivers of joint and the flexibility of joint.Combined with the sliding mode controller of the joint position servo control system,the pneumatic manipulator compliance is controlled while the position of the pneumatic manipulator is controlled.In addition,in order to increase the overall safety of the manipulator,the joint experiment is carried out,and the pressure change in the drivers during the collision process is analyzed.A safety control strategy is adopted to detecting the collision using the pressure difference of the drivers,which act after the collision is detected,reduce the pressure of the drive,stop the arm and reduce the rigidity of the joint to avoid possible damage.Finally,the control system of pneumatic manipulator is designed,the software and hardware of the control system are divided into multiple modules according to functions.The modules are relatively independent but work together.The hardware platform of the pneumatic manipulator control system was built,and the control software based on Windows Forms application was written by Microsoft Visual Studio C#.Based on the prototype platform,the joint control performance experiment and the manipulator control performance experiment were carried out respectively.The motion control performance and safety performance of the joint position servo control system were tested by position conversion experiment,trajectory tracking experiment and collision detecting experiment.The repetitive positioning accuracy and overall safety performance of the pneumatic manipulator were tested.The effectiveness of the design and control system of the pneumatic manipulator was verified.