Background: In recent years, patents suggest that four-wheeled robots have been widely used in outdoor reconnaissance fields. However, the emergency obstacle avoidance of the fourwheeled robot on the slope is affected by the slope angle and the friction coefficient of the slope, and its motor torque and yaw torque are prone to abrupt changes, causing the four-wheeled robot to slip greatly. According to relevant literature, PID control methods (dual-loop PID control and linear PID control) make the robot control motor current fluctuate greatly during the emergency obstacle avoidance process. Hence, the PID controller of the four-wheeled robot needs to be optimized.
Objective: This study aims to establish a novel dual-loop fuzzy PID controller to improve the stability of the four-wheeled robot during emergency obstacle avoidance on the slope.
Methods: Establishing the kinematics and dynamics equations of the four-wheeled robot, and determining the speed of the center of mass and the yaw rate are important control parameters for controlling the steering motion of the robot. Aiming at the PID controller of the past four-wheeled robot, its response speed is slow, and the overshoot of the speed of the center of mass and the yaw rate is large. For this reason, the dual-loop fuzzy PID controller is designed. Comparison simulation is carried out by the MATLAB programming.
Results: It is concluded that the control effect of the four-wheel robot with the dual-loop fuzzy PID controller is the best. The steering angle and displacement response speed of the four-wheel robot are faster, and there is basically no overshoot. The response of the yaw rate is increased by 30%, the average deviation of the linear motion trajectory is reduced by 41.27%, and the average deviation of the circular steering motion trajectory is reduced by 29.51%.
Conclusion: The dual-loop fuzzy PID controller can provide reference for the PID control research of other four-wheeled robots.