Purpose Aiming at the problem that quadruped crawling robot is easy to collide and overturn when facing obstacles and bulges in the process of complex slope movement, this paper aims to propose an obstacle avoidance gait planning of quadruped crawling robot based on slope terrain recognition. Design/methodology/approach First, considering the problem of low uniformity of feature points in terrain recognition images under complex slopes, which leads to too long feature point extraction time, an improved ORB (Oriented FAST and Rotated BRIEF) feature point extraction method is proposed; second, when the robot avoids obstacles or climbs over bumps, aiming at the problem that the robustness of a single step cannot satisfy the above two motions at the same time, the crawling gait is planned according to the complex slope terrain, and a robot obstacle avoidance gait planning based on the artificial potential field method is proposed. Finally, the slope walking experiment is carried out in the Robot Operating System. Findings The proposed method provides a solution for the efficient walking of robot under slope. The experimental results show that the extraction time of the improved ORB extraction algorithm is 12.61% less than the original ORB extraction algorithm. The vibration amplitude of the robot’s centroid motion curve is significantly reduced, and the contact force is reduced by 7.76%. The time it takes for the foot contact force to stabilize has been shortened by 0.25 s. This fact is verified by simulation and test. Originality/value The method proposed in this paper uses the improved feature point recognition algorithm and obstacle avoidance gait planning to realize the efficient walking of quadruped crawling robot on the slope. The walking stability of quadruped crawling robot is tested by prototype.

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 four-wheeled 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.

Background: It is a challenge that quadruped crawling robots face when working in the raised terrain of slope. The robot is affected by gravity and gait under this terrain, the ground reaction force on its hind legs is relatively large. This has strict requirements for the structure and gait planning of the quadruped crawling robot. Objective: Aiming at that the ground reaction force on the hind legs of quadruped crawling robot is relatively large when the robot climbing over the raised terrain of slope, a slope-triangular gait walking strategy for quadruped robots based on a layered CGP gait generation method is proposed. Methods: Three-dimensional model of the quadruped crawling robot is created in SOLIDWORKS. The kinematic model is established, and the foot position vector is obtained. Consider the characteristics of the raised terrain of slope, slope tripod gait and hierarchical CPG slope tripod gait generator are proposed. Comparative simulation of sloped tripod gait and flat tripod gait, the slope tripod gait with and without the gait generator is carried out by Adams programming. Results: Compared the centroid displacement curve, foot speed curve, and foot contact force curve of slope tripod gait and flat tripod gait. Compare the posture angle curves of the fuselage with and without the slope tripod gait generator. The result proves that the tripod gait walking strategy is feasible. Conclusion: The slope tripod gait walking strategy can improve the impact resistance of the quadruped crawling robot on sloped high ground. The gait design and motion analysis process of the robot can provide a reference for other quadruped crawling robot device.v

Background: In recent years, literature has suggested that quadruped crawling robots have been widely used in the field of reconnaissance on rugged mountain trails. Under the influence of gait and slope, the joint angle of the robot changes drastically when landing, resulting in the robot drop down from the slope. This has strict requirements for gait planning and gait control of quadruped crawling robots. Objective: The aim of this study is to set up a novel impedance controller based on gearshift integral PID to improve the stability of a quadruped crawling robot during climbing on a continuous slope. Methods: The three-dimensional model of quadruped crawling robot was established. Considering the characteristics of slope terrain, a slope diagonal gait design is proposed, and a gearshift integral PID impedance controller is designed for this gait. The impedance controller based on position PID, integral separation PID and gearshift integral PID is simulated by MATLAB, and the peak value of foot force is compared under ADAMS. Results: Overshoot and transient time of positional PID impedance controller was compared, integral separated PID impedance controller and gearshift integral PID impedance controller, the overshoot was reduced by 8.9% and the transient time was reduced by 20%. Finally, the position impedance controller that meets the requirements and import it into ADAMS to compare the peak foot force was selected, it reduced the foot-end contact force by 8.15%.The results show that the gearshift integral PID impedance control strategy is feasible. Conclusion: The Impedance controller based on gearshift integral PID can provide a reference for other impedance control strategies of quadruped crawling robots.