Position-posture Control And Gait Planning Of Six-legged Walking Robot

Multi-legged walking robots are more adaptive to the unstructured environment compared with other robots, because the ground passed by multi-legged walking robots distributes discontinuously. Therefore, multi-legged walking robots have wide application prospects. While some key technologies are needed to guarantee that multi-legged walking robots can walk through the rough terrains adaptively, and the position-posture control technology and gait planning technology are two of them. Many researchers have been devoted to the study of multi-legged walking robots. While the research on position-posture control of multi-legged walking robots is almost about open-loop control. Although there have been some gaits for gait planning of multi-legged walking robots, a gait that not only has well flexibility to complicated terrains but also is rapid and simple has not appeared. This thesis focuses on the position-posture control and gait planning of the six-legged walking robot in order to realize the closed-loop control on the position-posture of the six-legged walking robot and do further study on the turning gait of the six-legged walking robot. Therefore, it can lay the foundation for the further research on a gait suitable for a six-legged walking robot walking in the complicated environment.In the first chapter, firstly, the background and significance of the project is discussed and the development of multi-legged walking robots is summarized based on lots of domestic and foreign literatures and references. Then, an overview on the development of position-posture control and gait planning of multi-legged walking robots in the world is presented focused on the two main researches:position-posture control and gait planning of multi-legged walking robots. Finally, three research contents are illustrated.In the second chapter, kinematics of the six-legged walking robot is studied. Firstly, the mechanical structure and hardware of the six-legged walking robot platform is introduced. The hardware of the six-legged walking robot platform includes the upper computer and the lower computer. The calculation of the position-posture control and gait planning of the six-legged walking robot is conducted in the upper computer, and the collection and processing of the posture data as well as control on joints is done in the lower computer. Secondly, the D-H parametric model of the six-legged walking robot is constructed based on the six-legged walking robot platform, and the kinematics and inverse kinematics of the six-legged walking robot is analyzed, meanwhile a method with geometry structure is presented to solve the no solution problem or multi solutions problem in inverse kinematics of the robots.The third chapter mainly illustrates the position-posture calculation method. The position-posture adjustment is divided into position adjustment and posture adjustment based on motion decomposition principle, and the joint angles of the six-legged walking robot are computed respectively with the inverse kinematics method of the six-legged walking robot. Then the joint angles are solved for the position-posture adjustment of the six-legged walking robot using motion synthesis method. The kinematic model of the six-legged walking robot is built in ADAMS, and the position-posture calculation algorithm of the six-legged walking robot is implemented in MATLAB. Finally, a co-simulation using MATLAB and ADAMS is performed to validate the effectiveness of the position-posture calculation algorithm.In the fourth chapter, the position-posture closed-loop control of the six-legged walking robot is studied. Firstly, the inverse velocity kinematics model of the six-legged walking robot is constructed based on inverse velocity kinematics of a single leg of the six-legged walking robot. Secondly, the proportional control strategy is employed to implement the closed-loop control on position-posture of the six-legged walking robot. The control on position-posture of the six-legged walking robot is implemented by decoupling the position-posture closed-loop control into two closed-loops control, the position closed-loop control and the posture closed-loop control, based on the inverse velocity kinematics. Thirdly, the control strategy of the six-legged walking robot is designed in MATLAB, and the motion model of the six-legged walking robot is constructed in ADAMS, then a co-simulation for closed-loop control on position-posture of the six-legged walking robot is carried out using MATLAB and ADAMS, and the results of the co-simulation verify that the presented method of the closed-loop control on position-posture of the six-legged walking robot is correct. Fourthly, the theory of the closed-loop control on position-posture of the six-legged walking robot is applied in the six-legged walking robot platform with open-loop control on position and closed-loop control on posture. The step response experiments and sine tracking experiments of the posture closed-loop control on the six-legged walking robot are conducted to verify the validity of the theory of the closed-loop control on position-posture of the six-legged walking robot. Meanwhile, orthogonal experimental method is used to work out more optimal proportionality coefficient matrixes for position closed-loop and posture closed-loop. Finally, the theory of the closed-loop control on position-posture of the six-legged walking robot is proposed to solve the position-posture deviation problem of the six-legged walking robot caused by the round rigid feet. A co-simulation verifies that the position-posture closed-loop control performs well in solving the position-posture deviation problem caused by round rigid feet. The same environment is constructed in the laboratory as in the co-simulation and the closed-loop control on position-posture is applied in the six-legged walking robot platform. The results verify the validity of the closed-loop control method of the six-legged walking robot.In the fifth chapter, the gait planning of the six-legged walking robot is investigated. The tripod gait is applied in the turning gait with constant radius, and a simple planning method for turning gait with constant radius is presented based on tripod gait. Meanwhile an approach to calculate the maximum turning angle of the six-legged walking robot based on stability constraint and motion constraint is proposed. Different turning angles are applied in the turning gait with constant radius of the six-legged walking robot to improve the turning ability in every step when the two groups of legs support the robot respectively. A simulation is conducted with MATLAB and ADAMS to verify the validity of the turning gait with constant radius of the six-legged walking robot and the results show that the turning gait with constant radius is correct. Furthermore, the turning gait with constant radius of the six-legged walking robot is used in the six-legged walking robot platform, and the experiments results demonstrate that the turning gait with constant radius is correct.