Posture Control of a Four-Wheel-Legged Robot With a Suspension System

Liwei Ni,Liang Wu,Fangwu Ma

doi:10.1109/access.2020.3017662

Liwei Ni, Liang Wu + Show 1 more

Open Access

https://doi.org/10.1109/access.2020.3017662

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Abstract

To achieve posture control and ride comfort (vibration isolation performance) of a robot in unstructured terrain, a novel four-wheel-legged robot (FWLR) with an actively-passively suspension system is first designed. In the suspension system, the active parts are responsible for posture control and the passive parts are responsible for vibration isolation. Then, a closed-loop and decoupled posture control model with 11 DOF are proposed, with which we designed the posture controller with a second-order low-pass filter (SLPF). To test the posture control performance of FWLR in unstructured terrain, both simulation and experiment are carried out, the simulation and experimental results show that the posture angles in unstructured terrain are reduced by 54.65% and 59% on average, respectively. In addition, the frequency response shows that the posture angles are reduced by more than 50% in low-frequency unstructured terrain. Finally, to validate the ride comfort of FWLR, dynamic models with different degrees of freedom (DOF) are established and simulated, and the results present that the ride comfort can be improved with the posture angular acceleration is reduced by 15.83% and 46.7% on average. Generally, with the actively-passively suspension system proposed in this article, FWLR can be equipped with excellent ride comfort and posture control in unstructured terrain. The research in this article has potential reference value and practical value for enriching the posture control of robots and vehicles.

Highlights

Wheel-legged all-terrain mobile robots (WLATMR) have the advantages of wheeled robots and legged robots [1] and have a wide range of applications in the fields of post-disaster rescue [2], [3], resource exploration [4], [5], precision agriculture [6] and other fields [7], [8]
The results showed that the model and algorithm proposed in this article can improve the posture control ability of four-wheel-legged robot (FWLR) in unstructured terrain, in which the improvement proportion of the pitch angle is 58.2%, the roll angle is 51.1%, and the average improvement is 54.65%
The results show that the model and algorithm proposed in this article can obviously improve the performance of posture control in unstructured terrain, in which the improvement proportion of the pitch angle is 54%, the roll angle is 64%, and the average improvement is 59%

Summary

INTRODUCTION

Wheel-legged all-terrain mobile robots (WLATMR) have the advantages of wheeled robots and legged robots [1] and have a wide range of applications in the fields of post-disaster rescue [2], [3], resource exploration [4], [5], precision agriculture [6] and other fields [7], [8]. The traditional WLATMR seldom involves vibration isolation system, and the research on ride comfort is seldom considered, In addition, the modeling method of posture control usually regards the robot as a rigid body. These problems limit the development of WLATMR. To solve the problem of posture control and vibration isolation of WLATMR, a four-wheel-legged all terrain mobile robot with actively-passively suspension system called FWLR is proposed. 2) The combination of passive system and active system can achieve the advantages of both approaches, the ride comfort and posture control performance of the robot in unstructured terrain can be enhanced at the same time.

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Findings

CONCLUSION