Research On Motion Planning Of Tractor-trailer Mobile Robot

Motion planning for tractor-trailer mobile robot,as an important component of mobile robot,is one of the more active areas of mobile robots technologies and attracts the attention of many scholars at home and abroad. Following the appearance of various new methods and new technologies, Scholars from different countries have more in-depth research in motion planning. This paper has done some research work about path planning and path tracking for tractor-trailer of mobile robot. Through research in intelligent of mobile robot, some results have been achieved at present. This paper summarizes the current situation and trends at home and abroad, focus on widely method of path planning and path tracking. Because of the late start in our country, research and applications is still far behind some western countries. The research has theoretical and practical significance.Tractor-trailer mobile robot is a service robot. An important application of tractor-trailer mobile robot applied to logistics and transport, automated production, etc. As a type of service robot, the system has the flexibility to change the number of trailers and many other unique advantages. So it may increases efficiency and reduces cost. The tractor-trailer mobile robot mainly is used in automated factories, ports, railway stations, airports, nuclear power plants and other labor-intensive or risk situations of harmful to human health. Therefore it has broad prospects of application.Pioneerâ…¢robot which is produced by The United States ActivMedia Robotics company is used in our laboratory. In this dissertation, tractor-trailer mobile robot (TTMR) is a special type of mobile robot is studied which consists of a sequence of hinged rigid vehicles running on the horizontal plane. The system is driven by the tractor which is the power source of the whole system, located in the front. Driving wheels of tractor are driven by electric motor and can rotate around. The guide wheels located in the rear of the body can turn around. Trailers passively follow the tractor.A typical mobile robot motion planning process can be described as, first, the system needs to understand the task and then make global path planning. Secondly, generate control commands to bottom of the implementing agencies, then make mobile robot follow the planned path. In motion Process, mobile robot continuously detects ambient information and their own state information though sensors and integrates information. Last, update road map and control motion of robot in order to make the robot along the optimum path of collision-free driving.The academic research on tractor-trailers mobile robots involves kinematics and dynamics modeling, controllability, motion planning, stabilization and tracking control and so on. From the view point of system design and development, the design of sensors, control system computing hardware and software are included. The tractor-trailer mobile robot is a highly complicated and comprehensive system which is a typical nonholonomic, underactuated and nonlinear system in control theory. The theoretical analysis and system design are much different from the free single body mobile robot. So it is focus and difficulty point of Robotic research.Focusing on motion planning and control, the principal works are described as follows:Firstly, kinematics of the tractor-trailer mobile robot is analysed and kinematics model is established. Then verify the accuracy of kinematics model.Secondly, use twenty-eight sonar sensors of pioneer3 mobile robot to detect environmental information. Search for feasible path with the RRT algorithm, optimize feasible path and eventually convert feasible path to a line path. In addition, the broken line path must satisfy the physical constraints of tractor-trailer mobile robot.Thirdly, for the broken line path tracking control problem of tractor-trailer mobile robot, a controller based on fuzzy-LOS(Line-of-Sight)is designed. The controller can make tractor-trailer mobile robot tracking backward broken line path and have a good dynamic performance and tracking accuracy.Finally, Original machine experiments of path planning and path tracking control are achieved effectively to verify the effectiveness and feasibility of the proposed methods.