Research On Obstacle Avoidance For Industrial Robot Based On Danger Field

With the extensive application of robots,multi-manipulators and human-robot cooperation has become the main trend of the development and application of industrial robots.In view of the conflict between the end trajectory tracking and the obstacle avoidance movement of the redundant manipulator,the research of Huapu 6-axis industrial robot is studied and an obstacle avoidance algorithm to realize a transition between the primary and secondary tasks based on the danger field is proposed.It mainly includes: inverse kinematics solution,obstacle avoidance algorithm for kinematics,simulation analysis and experimental verification,dynamic obstacle avoidance algorithm and simulation analysis,and so on.The main contents are as follows:We simplify the structure of 6-axis industrial robots to planar 3-DOF redundant manipulator and build a kinematic model for it with the traditional D-H method.The Jacobian matrix and direct solution of kinematics are obtained.Various inverse kinematic algorithms such as: Geometric methods,algebraic method,Jacobian iterative method,closed-loop inverse kinematics algorithm,are comparatively analyzed.Due to the huge advantages of redundant manipulators in dealing with obstacle avoidance,joint limits,and singularities,the numerical inverse kinematics algorithm for redundant manipulators was studied.The various inverse solution algorithms was proved to be effective by means of Matlab simulations.For redundant manipulators,the use of the gradient projection method not only completes the trajectory tracking task,but also achieves the goal of avoiding the joint limit.In view of the conflict between the end trajectory tracking and the obstacle avoidance movement of the redundant manipulator,the evaluation function called danger field for risk assessment between manipulator and obstacles was improved.By feeding back the value of the danger field to a modified Closed Loop Inverse Kinematics(CLIK)algorithm,weighting the Jacobian matrix and gradient,the method can realize joint limit avoidance in combination with obstacle avoidance.In order to ensure the avoidance efficiency,the closed-loop control parameter was designed.In the process of obstacle avoidance,the manipulator has an ability to cope with task suspension and resumption according to relationship between the value of danger field and the threshold set in advance.The prosed method was proved to be effective in numerical simulations by means of Robotics Toolbox for Matlab in 2D and 3D space,respectively.Based on the static and dynamic analysis of redundant manipulators,a virtual plane 3-DOF redundant manipulator model is established in the Robotics Toolbox for Matlab;The inverse dynamics control algorithm of the operating space is studied.To realize the purpose of dynamic obstacle avoidance,the danger field is converted into a kind of virtual force acting on the manipulator and obstacles,and the analysis where the force should be is made.Finally,the components of Huapu 6-axis industrial robot control system are introduced and modified.The joints 1,4 and 6 of the 6-DOF manipulator are fixed,it is equivalent to a planar 3-DOF redundant manipulator,and the method of solving the obstacle position is designed.Then,the control algorithm is programmed to experiment by combining Labview-based graphical language and Matlab language,and the obstacle avoidance function of the robot is preliminarily realized.