The Robot Research Based On Four Bars Tensegrity Structure

With the rapid development of high technology, now robot has been indispensable part of daily life. Tensegrity structure robot is a new whole section in robot industry. Now lots of scholars come to focusing on tensegrity structure robot because the characters that the structure possess is light quality, deformable shape and anti shock when applied to the field of aerospace,detection and disaster relief. This paper take a deep study to 4-bars tensegrity structure robot mainly including the analysis of geometry configuration, the analysis of deformable structure and kinematics, the analysis of the stability and load bearing capacity and motion simulation and test of concrete product. All kinds of contents is the followings.Firstly, first-order tensegrity structure mathematical model is builded. The relationship of connection matrix from nodal vector matrix to member vector matrix can be acquired by building the structure of nodal vector matrix and member vector matrix, so theoretical configuration can be builded. The twist angle a is acquired by the balance of nodal force of first-order p-bars tensegrity structure, also, it can be gained that the structure has p-1 kinds of configurations. According to the method above, 4-bars tensegrity structure possess 3 kinds of configurations. By comparing their theoretical configurations and concrete modals, the first kind of theoretical configuration and concrete modal is chosen as study object in the paper.Secondly, the kinematics analysis of 4-bars tensegrity structure robot. By analyzing structure deformation, the functional relation between structure nodal coordinate and the change of diagonal cable length can be expressed, then arbitrary nodal coordinate can be gained in the process of structure deformation. For the sake of analyzing the location relation between structure centroid and triangle consisted of 3 nodals that contacting with ground, the method of homogeneous coordinate transformation is applied to build theoretical model to get the pose of the side of triangle in the XOY surface . By analyzing respectively odd and even numbers steps to get the possibilities that achieve eversion in the process of deformation process, the corresponding relationship can be guaranteed between the change range of diagonal cable length and other members' length change. So ,the change of driving cable length can be expressed by the change of nodal coordinate. At last, functional relationship between the speed and acceleration of nodal coordinate and the change of diagonal cable length can be gained.And the method of controlling speed can be gained in the process of deformation process.Thirdly, building the nodal force balance equation and deformation compatibility equation.Making use of SM method and multiplying force method determine initial configuration of structure, stability and controllability in the process of deformation. So it is correct that 4-bars tensegrity structure is stable in the process. Making use of finite element method build structure stiffness matrix, also, pre-force is applied to correct structure stiffness to gain the appropriate stiffness matrix. When external force is applied to the structure, by analyzing deformation amount to judge the loading capacity to guarantee the structure is stable.Lastly, motion simulation and test of concrete product .Using ADAMS software simulate the 4-bars odd and even steps motion, whole consistent steps motion and structure motion that deformation caused by driving single cable. So, all the nodal coordinates in 4-bars tensegrity structure and tensegrity centroid motion locus paintings can be gained to guarantee that theoretical analysis is right. By using the method, the way of driving can be gained. By using Solidworks software to build 3-dimensintional model, concrete product can be made. Having experiment for concrete product about the 4-bars odd / even steps straight motion and structure turn motion that deformation caused to verify the correctness again. And the motion above can be the basis of 4-bars tensegrity structure robot moving consistently.