Structural Design and Obstacle-surmounting Dynamics Research of Six-wheeled Rocker-type Mobile Robot

doi:10.12382/bgxb.2022.0825

Abstract

Abstract:

A passive obstacle-surmounting six-wheeled rocker-type mobile robot is roposed to improve the obstacle-surmounting performance of mobile robots in complex terrain environment. The obstacle-surmounting performance of the robot is studied for climbing steps. The relationship between the structural parameters and the obstacle-surmounting height when the robot does not have the bottom support phenomenon is obtained from the analysis of geometric conditions, and the key obstacle-surmounting process of the robot is analyzed. The obstacle-surmounting dynamics models of front wheels, middle wheels and rear wheels are established. The influences of the robot’s speed, acceleration, adhesion coefficient and the position of the center of gravity on the output torque of hub motor are analyzed based on the dynamics models. The passing capability of robot is verified by using the prototype experiment and ADAMS simulation software, and the output torque curve of robot’s hub motor is obtained to guide the selection of motor. The research results show that the robot has good passing capability for climbing steps, which provides a design reference for improving the obstacle-surmounting performance of robot in complex terrain.

Key words: mobile robot, rocker, obstacle-surmounting performance, dynamics

CLC Number:

TP24

SHANG Zhe, WANG Ting, XU Yao, WU Yingbiao, SHAO Peiyao, SHAO Shiliang. Structural Design and Obstacle-surmounting Dynamics Research of Six-wheeled Rocker-type Mobile Robot[J]. Acta Armamentarii, 2023, 44(11): 3478-3488.

Figures/Tables 26

Table 1 Design indexes of robot

参数	取值
规格/mm	1300×700×1200
爬坡角度/(°)	30
越过障碍物高度/mm	300
爬过一定尺寸的楼梯	国家标准室内人行台阶

Fig.1 Schematic diagram of six-wheeled rocker-type robot

Fig.2 Mechanism sketch of six-wheeled rocker-type robot

Table 2 Main parameters of robot

参数	数值
最大速度v/(m·s^-1)	4
整体质量m/kg	120
车轮半径R/mm	190
前轮与后摇臂回转中心距L₁/mm	690
中轮与后轮中心距L₂/mm	460

Fig.3 Structure diagram of front rocker arm

Fig.4 Structure diagram of left rear rocker arm

Fig.5 Principle diagram of shock absorption of tension spring

Fig.6 Relation curve of resistance moment

Fig.7 Obstacle surmounting process of robot

Fig.8 Geometric conditions for middle wheels to climb the steps

Fig.9 Geometric conditions for rear wheels to climb the steps

Fig.10 Relationship between wheel spacing and obstacle-surmounting height

Fig.11 Force analysis of front wheels for obstacle surmounting

Fig.12 Force analysis of middle wheels for obstacle surmounting

Fig.13 Force analysis of rear wheels for obstacle surmounting

Fig.14 Effect of speed on output torques of rear wheel

Fig.15 Effect of acceleration on output torques of rear wheel

Fig.16 Effect of adhesion coefficient on output torques of rear wheel

Fig.17 Effect of height of the center of gravity on output torques of rear wheel

Fig.18 Effect of horizontal position of the center of gravity on output torques of rear wheel

Fig.19 Simulation of roboto bstacle-surmounting

Fig.20 Driving moment curve of obstacle-surmounting

Fig.21 Curves of wheel center position

Fig.22 Experiment of robot passing 300mm height obstacle

Table 3 Experimental results of obstacle-surmounting

垂直高度/mm	现象	时间/s	俯仰角/(゜)
120	快速通过	4.72	10.86
180	顺利通过	6.35	16.42
240	颠簸通过	8.74	22.14
300	明显颠簸缓慢通过	9.87	29.05
340	不能通过

Table 4 Experimental results of bearing capacity

负载/kg	垂直高度/mm	现象	平均行驶时间/s
20	300	顺利通过	9.35
40	300	顺利通过	9.60
60	300	顺利通过	10.18

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