Pose Control of Biomimetic Wheel-legged Robots in Complex Terrain

The terrain in hilly and mountainous areas is complex and diverse,and the operating environment of agricultural machinery equipment is mainly inclined slopes. Traditional agricultural machinery equipment has low efficiency and poor stability when operating in complex terrain in hilly and mountainous areas,and may even cause serious accidents such as tilting and overturning. A wheel-legged robot platform that can autonomously achieve pose leveling control in complex terrain of hills and mountains was proposed from the perspective of biomimetic mechanical design,improving the stability and safety of operations in complex terrain. Firstly,taking the insect hind foot as the biomimetic mechanical design object,and combining the principle of multi link mechanism,the overall architecture design of the new variable stroke wheel-legged mechanism and robot platform was completed. The kinematics characteristics of the wheel leg mechanism were analyzed by using the D-H parameter method. The results showed that the maximum adjustment of the ground clearance of the wheel-legged robot was 574 mm,and it had a strong ability to surmount obstacles. Then the spatial attitude parameters of the wheel-legged robot were defined in the spatial coordinate system,and the spatial attitude model between the fuselage attitude angle and the wheel leg extension was derived. An NSGA-Ⅱ based algorithm for inverse solution of the fuselage spatial attitude was designed. Based on the spatial attitude inverse solution algorithm,an omnidirectional attitude control system for wheel-legged robots was constructed, which included a vehicle body leveling controller,a “virtual leg” compensation controller, and a centroid height controller. It can control the spatial attitude parameters of wheel-legged robots such as pitch angle,roll angle,grounding force,and centroid height when driving in complex terrain. The algorithm simulation verification of the pose control system was completed through the ADAMS-Matlab joint simulation model of the wheel-legged robot. Finally,experiments on automatic adjustment of ground clearance and omnidirectional posture adjustment of the vehicle body were conducted on the robot prototype. The results showed that the maximum adjustment amount of the ground clearance of the test prototype was 574 mm,and the omnidirectional automatic leveling of the vehicle body posture could be achieved in complex terrain. The average leveling time was about 1.2 s,and the average leveling error was 0.8°. The response speed and leveling accuracy of the posture control could meet the actual work requirements. © 2024 Chinese Society of Agricultural Machinery. All rights reserved.