Research On Deformable Mechanism Driven By Flexible Artificial Muscle And Its Motion Control

Tensegrity mechanism is a flexible system consisting of flexible rope and rigid bar.It belongs to a flexible multi-degree-of-freedom and under-actuated flexible mechanism.There are many kinds of tensegrity mechanism,such as standard triangular prism tensegrity mechanism,four-bar tensegrity mechanism and so on.The movement of the tensegrity mechanism can be in two ways: wriggling and rolling.All types of tensegrity mechanisms can be realized by creeping movement,that is,the nodes touching the ground can be processed specially so that they can creep forward in the process of alternating deformation of the mechanism.The rolling motion mode is a more natural movement mode of tensegrity mechanism,and has more advantages in environmental adaptability and motion performance.The six-bar tensegrity mechanism has a spherical shape,which is more suitable for rolling motion.In addition,the six-bar stretching mechanism can fold to reduce its occupied space,which is also a comparatively large advantage of the tensegrity mechanism compared with the traditional mechanism.After folding the tensegrity mechanism,it is more convenient to store and transport.This technology is also used in the exploration of space.In this study,the six-bar tensegrity mechanism is taken as the research object.First,the shape-finding research is carried out,its configuration is described mathematically,and the topological diagram of the six-bar tensegrity mechanism is established.According to the characteristics of the six-bar tensegrity mechanism,he twisted and coiled actuator(TCA)is used as its actuator.According to the nodal balance equation,the mathematics between the driving parameters of flexible artificial muscle and the change of the center of gravity of the six-bar tensioning mechanism is established.The rolling principle of six-bar tensegrity mechanism is expounded from a mathematical point of view,the definition of gravity moment is given,and the critical condition for rollover of six-bar tensegrity mechanism is put forward according to gravity moment.The rolling gait of the mechanism is studied according to the mechanism topology diagram,and the rope and rod structure design of six-bar tensegrity mechanism is completed.The open source software NTRTsim developed by NASA and other university collaborators was used to simulate the six-bar tensegrity mechanism.This paper introduces the simulation framework of NTRTsim and the model of rod and rope,realizes the modeling of six-bar tensegrity mechanism by using C++ programming in NTRTsim simulation environment,and compares and verifies the results of the above-mentioned shape finding problem.expounds the folding principle of tensegrity mechanism,determines the combination mode of flat folding and bundle folding actuators through theoretical analysis.the physical performance parameters of artificial muscle are added to the simulation of driving rope model to achieve the effect of flat deformation and bundle deformation.The bending deformation of the mechanism can reach 18.5 ° in the simulation environment as a two-stage tensegrity mechanism.The control sequence of the actuator is determined,and the single gait simulation and the continuous roll simulation are completed in NTRTsim software.The folding deformation and rollover of the six-bar tensegrity mechanism are verified by design and experiment.Firstly,the prototype of passive temperature control folding experiment and the experimental platform are built.The mechanism achieved the expected effect of flat folding and bundle folding.The driving load performance of the mechanism is tested and branched.The bracing performance test shows that the six-bar tensegrity mechanism can be folded from 156 mm to plane at 150 ?,and the height can be increased to 201.38 mm at 900 g load,which is 11.38 times its own weight.The driving circuit and prototype of the six-bar tensegrity mechanism with active temperature control have been designed and fabricated.The open-loop control of roll of six-bar tensegrity mechanism is realized,which makes it roll according to straight track and turning track.It takes 150 s to roll in a straight line with a single turning angle of 89°.Relevant results lay a theoretical and practical foundation for the complicated path planning of the six-bar tensegrity mechanism.