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

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 lowpass 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 paper, FWLR can be equipped with excellent ride comfort and posture control in unstructured terrain. The research in this paper has potential reference value and practical value for enriching the posture control of robots and vehicles.

Attitude Control of Vehicle Based on Series Active Suspensions

“…An attitude closed-loop control strategy was verified by both the simulated model and the real vehicle. In order to reduce the impact of rough terrain on stability and ride comfort, the attitude control algorithm was further verified [18,19].…”

Motion control framework for unmanned wheel-legged hybrid vehicle considering uncertain disturbances based robust model predictive control

“…As a new configuration scheme, the unmanned wheellegged vehicle (UWLHV) can perform the tasks of reconnaissance patrols, rescue after disasters, and other dangerous missions in complicated terrains (Bjelonic et al, 2019(Bjelonic et al, , 2020. Compared with the wheeled vehicle and legged vehicle, the UWLHVs possess the obvious advantages on terrains adaptability and obstacle-passing ability, which can cross steps, vertical walls, slope roads, and another rough road (Bjelonic et al, 2019;He and Gao, 2020;Ni et al, 2020). During the UWLHV running on the road, the control systems are generally affected by the internal disturbances and the external disturbances, such as the rough road, the model uncertainty, inner sensor noise, etc.…”

Attitude control strategy for unmanned wheel-legged hybrid vehicles considering the contact of the wheels and ground

“…As a typical mechanism structure of multi-modality and strong coupling, an unmanned wheel-legged hybrid vehicle (UWLHV), combining with the high maneuverability and energy-saving of the wheeled mode and the legged mode, can walk over some obstacles. 4,12,13 During patrol and surveillance tasks, attitude control is the crucial to improving the terrain adaptability of the UWLHV body and is researched. The attitude control research, such as that on UWLHVs and conventional vehicles equipped with active suspensions, has been conducted by many scientific institutions and industries around the world to improve the flexibility and road smoothness.…”