Research On Kinematic And Motion Plan Of 7-DOF Manipulator

In recent years,the research of 7-DOF redundant manipulators has received extensive attention from scholars at home and abroad.In the redundant manipulator,the 7-DOF manipulator not only has the common characteristics of redundant manipulators,such as good flexibility,fault tolerance,singularity avoidance,etc.,but also has excellent stiffness performance due to fewer joints.Commonly used in industrial production,spraying,welding and human-machine collaboration.In this paper,a typical 7-DOF redundant manipulator is analyzed and the collision detection and motion planning for the manipulator are studied.The kinematics is analyzed for a typical 7-DOF manipulator.The self-motion of the manipulator is affected by the length of the link and the position of the manipulator is analyzed.By determining the self-motion configuration,the closed solution of the redundant manipulator is calculated by separating position and orientation.The optimized index about redundant angle is raised to avoid the limit of the joint angle.The inverse kinematics and the avoidance of the joint limit are verified.The singular configuration and avoidance of the redundant manipulator are studied.It is proven that the selection of coordinate system and elementary transformation do not affect the condition of the Jacobian matrix row dissatisfaction rank.The appropriate coordinate system is chosen to establish a simplified Jacobian matrix and the matrix's elementary transformation and matrix partitioning idea are used to derive the singular configuration condition;The singular configuration is analyzed and mapped to Cartesian space.The method of singular configuration avoidance is proposed by using redundant angle optimization.The singular configuration and avoidance method are verified.Collision detection of this type manipulator has been studied.The complex manipulator model is simplified by the capsule body.According to the motion characteristics of the mechanism,the method based on the auxiliary plane is proposed to quickly detect the collision;the collision detection between the manipulate arm and the obstacle is transformed into the collision detection between the capsule body and the sphere or the box.The manipulator's collision detection converts the collision detection between the capsules body.The solution about the shortest distance between simple geometry such as plane,segment,sphere and box is derived.The way of collision detection proposed is simulated and verified.The motion planning about obstacle avoidance of the 7-DOF manipulator was studied.For motion planning about the obstacle avoidance under path constraints,an obstacle avoidance motion planning method based on A-Star algorithm is proposed.Using the redundant characteristics of the manipulator,the obstacles,singular configurations and joint limits in the task are mapped to a two-dimensional plane with the end trajectory as the horizontal axis and the redundant angle as the vertical axis.The curve of avoiding obstacles,avoiding singularities and avoiding joint limits is got.For the motion planning with obstacle avoidance of point-to-point task,an obstacle avoidance planning algorithm for workspace partition is proposed.The workspace is divided into free space and obstacle space according to the obstacle,and the two spaces are separately planned,and finally a curve with obstacle avoidance is obtained.The motion planning algorithms under these two different tasks are simulated and verified.