Research On Tensegrity Robot Driven By Flexible Artificial Muscle And Its Motion Control

Tensegrity mechanism is a flexible mechanism composed of rigid bars and flexible ropes,whose rigid and flexible structure gives it extremely high flexibility of movement.If a driver is added into the tensegrity mechanism to realize the reliable movement of the specified trajectory,it can be called as the tensegrity robot.At present,the driving forms of tensegrity robot can be divided into motor drive,pneumatic drive and shape memory alloy(SMA)drive,which have their own limitations.The polymeric artificial muscle,twisted and coiled actuator(TCA),is a new kind of flexible driver,which has the advantages of small hysteresis,long cycle life,low cost and high power density ratio.However,as a new driver,the application of polymeric artificial muscle(TCA)is still limited.The application of the polymeric artificial muscle to the driving of tensegrity robot can not only simplify the structure of tensegrity robot and give better play to the overall flexibility,but also broaden the application field of flexible artificial muscle.In this study,the motion form of tensegrity robot is analyzed firstly.Two motion forms of creeping and rolling are proposed by combining the artificial muscle with the tensegrity robot.Taking the four-bar tensegrity robot and the six-bar tensegrity robot as examples,the two motion forms are analyzed in principle.For the wriggly four-bar tensegrity robot,a needle-like foot is added at the bottom of the robot bar using the principle of bionics.The needle-like foot is used to clamp and move,so as to realize the wriggle of the four-bar tensegrity robot.For six-bar tensegrity robot,the principle of robot rolling and rolling gait of robot are analyzed,the greedy algorithm is used to design of rolling robot trajectory planning problems.The algorithm is implemented to complete the robot trajectory planning,including straight line,triangle and square.The open source software NTRTsim is used to make form-finding analysis of four-bar tensegrity mechanism.We identify the parameters of bars and ropes,which provide basis for the production of four-bar tensegrity robot prototype.In order to make better analysis of rolling process,ADAMS is used to make six-bar tensegrity robot model and determine the related parameters of the robot.The single step rolling and continuous rolling of robot is accomplished and the different artificial muscle drive scheme is designed.The simulation find that the artificial muscle actuator shrinkage to make single step rolling of the robot is 24% to 28%,which can be achieved by the current polymeric artificial muscle.Cosimulation are used to verify the motion trajectory planning of the robot,and the co-simulation of triangle and square trajectory of the robot are completed.The experiments are carried out on both wriggly and rolling tensegrity robot.Firstly,a polymeric artificial muscle coiler is designed to improve the efficiency of the production of artificial muscles.Then the four-bar tensegrity robot prototype and control system is manufactured,and the creep experiments are carried out and the results show that the robot can realize the wriggle along X and Y directions by the artificial muscle actuator.The working temperature of artificial muscles is 60? to 120?.The robot's wriggle cycle is 30 s and wriggle distance is 8 mm.At last,the prototype of the six-bar tensegrity robot was made and tested.It was found that the single-step rolling of the robot could be completed under the work of two groups of artificial muscle drivers.The working temperature of the artificial muscle is 70? to 120?.The driving stroke of the artificial muscle driver is 24%,which is consistent with the simulation results.