Research On Trajectory Planning And Motion Control Of Wheeled Mobile Robot Under Slope Terrain Conditions

In recent years,with the development of aerospace technology and military technology,people have more and more frequent detection tasks in unknown areas.Special robots for special working environments,such as the field,have attracted many scholars to conduct technical research.Wheeled mobile robots(WMR)stand out among many special robots due to their excellent maneuverability and are widely used in various special environments.In the wild with harsh conditions,especially in desert environments or extraterrestrial planets,its soft surface and rugged terrain can easily cause wheeled mobile robots to slip during operation,which adds difficulties to the control of the robot.In this paper,the movement control problem of wheeled mobile robot on soft slope terrain is analyzed and studied.The main research results are as follows:The kinematics and dynamics model of the WMR on soft slope terrain are established.The motion of the skid-steered mobile robot is analyzed,and the relationship between the speed of each wheel and the speed of the robot is obtained.Since the wheel is prone to slipping when the robot is on the soft slope terrain,the wheel-ground interaction when the soft soil is in contact with the wheels is analyzed.Based on the wheel-ground mechanics,the relationship among the hook traction force,the support force and the lateral force of the wheels is obtained,and the 3DOF dynamics model of the WMR on the inclined plane is established.The autonomous trajectory planning of the robot is carried out by using jump point search and polynomial in an obstacle environment.In the environment with obstacles,the grid method is used to establish the grid map of the working environment of the robot and determine the grid information.By using the jumping point search algorithm,a safe and collision-free movement path can be quickly searched in the grid graph.However,the path searched by the jumping point is tortuous,which is not suitable for direct use in motion control of the WMR,Therefore,in the later stage,quintic polynomial and motion stability index are introduced to smooth the trajectory of the safe path of the mobile robot,and a smooth and traceable trajectory is obtained.Completed the trajectory tracking control research of WMR on slope terrain.When the wheeled mobile robot is moving on the soft slope,the wheels and the ground are easy to slip.At this time,when the traditional tracking controller that the wheels does not slip is adopted,the robot cannot follow the reference trajectory.This paper considers this situation.Using predictive control theory,a position tracking controller considering the lateral skid of the robot is designed at the kinematics level;at the dynamics level,slip and other disturbances are regarded as the total disturbance of the system,a nonlinear disturbance observer is designed to estimate the amount of disturbance.Combined with sliding mode control theory,a speed controller of the robot is designed to complete the motion control of the wheeled mobile robot and improve the robustness and stability of the robot system.Based on the Webots simulation software,a virtual working environment of the robot is established,and the proposed trajectory planning and motion control methods are simulated and verified.Firstly,the control effect of two kinds of controllers on the slope with or without skidding is compared.The results show that the motion controller that considers the slip can control the robot to track the desired trajectory when the slip occurs.Secondly,the verification of the robot’s curve tracking control on different slopes is carried out.which results shows that the controller in this paper can also make the robot track the desired reference trajectory under different slopes.Finally,a comprehensive simulation of the autonomous trajectory planning and motion control of the mobile robot is carried out in the environment with obstacles.From the results,it can be seen that the planning and control method in this paper can enable the robot to find a safe and feasible trajectory in the working environment and complete the desired motion.In summary,the following conclusions can be drawn:The method proposed in this paper can improve the autonomy and robustness of the robot,and has certain theoretical and practical significance in the motion control of the robot.