Planning And Optimization For Under-constrained Multi-robots Coordinated Towing System

The increase of social demand has promoted the continuous expansion of the robot's suitable work place and the usage method.However,it is not the best practice to use a single robot for more complex tasks.Multi-robot collaboration is usually able to complete a large lifting task that is difficult for a single robot to complete.Cable-typing multi-robots is an important branch of the parallel robots,which inherits and develops many virtues of the traditional parallel robots and the multi-robots.The towing system that cooperates with multiple cable-typing robots is called the under-constrained multi-robots coordinated towing system.To realize the trajectory planning of the robot in the system is the basis for robots to successfully complete their work tasks,which has important theoretical and practical significance.By analyzing the spatial configuration of the cable-typing multi-robots coordinated towing system,the general kinematic model of the towing system based on the principle of vector closure was established,and the dynamic model of the towing system were established by using Newton Euler equation and Lagrange equation respectively in this thesis.Then the existence of the solution of the inverse kinematics that may be involved in the trajectory planning is discussed.Considering the great influence of the dynamic space in the actual working conditions,the dynamics workspace of under-constrained multi-robots coordinated towing system is analyzed.The dynamic working space scope of system is determined by Monte Carlo method.On the basis of the dynamic and kinematic models,which are established,the dynamic characteristics of the system are analyzed.According to the calibrated dynamic working space and dynamic force equilibrium condition,the concept of variable tension mean is introduced to optimize the tension of the cable.A new optimization algorithm is developed,which can limit the tension of the system to the safety range,and the correctness of the algorithm is verified by simulation.The ultimate goal is to make the cable tension not excessively concentrated near the limit tension position.It can ensure that the flexible cable is always in the tension state,but also can further guarantee the safe operation of the mechanism.Because the under-constrained system cannot meet the conditions of vector closure,so there is a difficult point in trajectory planning.By combining the system with three-dimensional geometry and under the premise of satisfying the geometric and mechanical constraints,the optimized trajectory of the search strategy will be used to stratify the trajectories of the towing objects.Finally,all the end positions of robots satisfying the conditions are solved to achieve three-dimensional search problems into two-dimensional.Discard many problems caused by previous single algorithm optimization.Combine the forward value iterative method with the A* algorithm to optimize multiple sets of inverse solutions.To achieve the goal of achieving smoothness and accuracy of the entire system during coordinated towing by planning the optimal end motion trajectory of a single robot.Simultaneously simulate and verify the optimized results.Finally,from the energy point of view,the existence of the system's swing problem is planned,and a simple anti-swing strategy based on energy cancellation is formulated.On the basis of the above theory analysis,the experimental platform that meets the experimental requirements was established,and the model verification experiment and the trajectory planning experiments were carried out to verify the correctness of model and trajectory planning strategy.