Motion Planning And Coordinated Con-Trol For Redundant Mobile Robot

The mobile robot is a rapidly developing research field in recent years,which mainly includes mobile platform and mobile manipulator.Motion planning and coordinated control are the main contents of current mobile robot research,which have attracted wide attention from academia and industry.The redundant degrees of freedom is a major challenge and difficult problem in the research of motion planning and control of mobile robot.In this paper,for over-actuated mo-bile platform,a multi-layer control allocation method is proposed,which considers both trajectory tracking performance and wheel motion coordination;for the mobile manipulator with high redun-dant kinematic freedom,an optimization-based integrated motion planning method is proposed.In this paper,the structural characteristics of over-actuated mobile robots is analysed,and clarifies the important difference between the control of over-actuated mobile robots and the tradi-tional two-wheel-driven mobile robots,where the driving wheels are independently driven without physical connection,which may lead to the problem of uncoordinated movement of each wheel.In order to improve the control performance of this kind of mobile robot,trajectory tracking and wheel motion coordination are two key control issues.At present,the dynamic model of over-actuated mobile robot is not perfect,and the kinematic-based motion allocation control method can not meet the requirements of high performance control.To address the above problems,we propose a simple and effective adaptive motion allocation method,and then a three-level control allocation method is also proposed to achieve better trajectory tracking performance while coor-dinating the wheel motion.In addition,in this paper,the kinematics of the mobile manipulator is studied.It is clear that high redundancy kinematics freedom is the main challenge in the mo-tion planning of the mobile manipulator,that is,there are numerous solutions to make the end effector achieve target position.Thus,a motion planning method based on optimization method is proposed to realize the integrated motion planning of mobile manipulator under target constraints(configuration space,Cartesian space),joint motion constraints and obstacle constraints.Firstly,a multi-system coupled modeling method of over-actuated mobile robot is proposed,which presents a complete kinematics and dynamics transformation relationship for each part of over-actuated mobile robot,and presents a detailed description of wheel/ground interaction-s.Then,a motion allocation control method based on kinematics model is studied in this paper.The controller is simple and easy to implement in engineering.Compared the direct motion alloca-tion,an adaptive motion allocation algorithm are designed,which can achieve better performance.Furthermore,a three-level structure control method is proposed,which considers both trajectory tracking and wheel motion coordination:In the high level,by mainly focusing on the chassis dy-namics,an adaptive robust control law is proposed to track the desired robot motion trajectory and generates virtual friction driving force for the later middle level control design.In the middle level,a control allocation technique is applied to deal with the over-actuated feature such that the wheel slip reference is calculated for each wheel in the low level design.And in the low level,the wheel slip control is designed to track the desired slip reference by considering the wheel dynamics.Theoretical and comparative experimental results verify that the proposed adaptive motion allo-cation control method and the coordinated control method can further improve the performance,which is an effective way to address the over-actuated mobile robots.Lastly,a optimization based motion planning method is proposed for the mobile manipulator with high degree of redundant kinematics.With the target constraints,joint constraints and obstacle constraints and the shortest path cost function the coordinated motion planning for mobile manipulator to generate a collision free trajectories from the initial state to target state is developed,where the trajectories of mobile platform and manipulator are planned simultaneously by optimization-based method.