Research On Trajectory Optimization Of Pickup Manipulator In Obstacle Environment Based On Improved Artificial Potential Field Method

With the continuous development of robot technology,the ball pickup service robot has flexible operation and strong environmental adaptability.It can pick up scattered balls in training ground,solve the time-consuming and laborious problems of traditional manual operation,and has broad application prospects.As the core component of the pickup service robot,the manipulator is the key to successfully realize the picking up of small spherical objects.However,at present,there are still some problems such as low efficiency and collision in obstacle space during the pickup operation of the manipulator.In order to improve the efficiency of picking up and avoid collision with obstacles,this paper takes a five-degree-of-freedom articulated pickup manipulator as the research object,focusing on the optimal trajectory planning of the manipulator and obstacle avoidance planning under obstacle environment,and applies it to the trajectory optimization under obstacle environment,so as to obtain the obstacle avoidance path under the optimal trajectory.Firstly,according to the functional requirements of the pickup manipulator,determine its structural configuration,driving method and the number of degrees of freedom to complete the overall structural design.Based on the structure of the pickup manipulator,the D-H method is used to establish the linkage coordinate system of the manipulator,the forward and inverse kinematics models of the manipulator are derived,and the Monte Carlo numerical analysis method is used to simulate the pickup space.The results show that the moving range of the manipulator in the direction of x,y and z axes reaches[-500 mm,600 mm],[-450 mm,450 mm]and[-300 mm,850 mm],respectively.Secondly,in order to shorten the working time of the picking-up manipulator and improve its operation efficiency,the cosine adaptive genetic algorithm is proposed to optimize the trajectory.The polynomial interpolation method is used for joint space trajectory planning to form the theoretical basis of time optimal trajectory planning.According to the process of genetic algorithm,genetic parameters are set,objective function is established,fitness function is designed,motion parameters are constrained,three major genetic operators are set and adaptive functions are dynamically adjusted,so a cosine adaptive genetic algorithm model is established.The optimal trajectory planning simulation is carried out by using this algorithm,the results show that the optimized trajectory curve is smooth and the running times of joint 1to joint 5 are shortened by 78.8%,80%,26%,41.2%and 81.2%respectively,compared with the original prescribed time,which significantly improves the running efficiency.Then,aiming at the collision problem of manipulator in obstacle environment,the obstacle avoidance planning based on improved artificial potential field method is carried out.According to the working principle of artificial potential field method,the gravitational potential field function,repulsive potential field function and resultant potential field function are established,and the problems of target inaccessibility and local minimum value defect under traditional artificial potential field method are analyzed.For the problem of target unreachable defect,the distance term d~n(X,X_g)between the manipulator and the target point is added to the original repulsive potential field function.Considering the influence of the obstacle boundary on the obstacle avoidance planning of the pickup manipulator,the radius r of the obstacle is introduced into the repulsive potential field function,so as to achieve the purpose of adjusting the repulsion potential field.For the problem of local minimum value defects,the method of establishing virtual sub-target points is proposed.The obstacle avoidance planning simulation is carried out under the improved artificial potential field method.The result proves that a collision-free path can be successfully planned for the manipulator in the obstacle space.Finally,the virtual prototype of trajectory optimization in obstacle environment is simulated and analyzed by combining the improved artificial potential field method and cosine adaptive genetic algorithm.The simulation results of virtual prototype trajectory optimization in barrier-free environment show that the theoretical deduction is correct.In order to optimize the trajectory in obstacle environment,the improved artificial potential field method is used to process obstacle avoidance planning,and then the cosine adaptive genetic algorithm is used to optimize the trajectory.The simulation results show that the running time of the manipulator is reduced by 51.6%,and the collision-free path under the trajectory optimization of the manipulator is obtained successfully.