Adaptive Attitude Control of Wheel-legged Mobile Platform Based on Feedforward Compensation

doi:10.12382/bgxb.2022.1103

Abstract

Abstract:

When passing through complex obstacles, a wheel-legged mobile platform bears a relatively large load on the wheel end, and the external force acting on the tire from the ground undergoes sudden changes. This significantly reduces the precision of the platform's attitude control and can lead to tire instability and loss of contact with the ground. To improve the terrain adaptation and stability, an adaptive attitude control strategy for the platform based on feedforward compensation is proposed. Considering the vertical support force and longitudinal driving force at the wheel-ground contact point, the inverse kinematic model and dynamic model of the platform are constructed. And the real-time estimation of the wheel-ground contact state is achieved, and the leg height observer and wheel-ground contact state are combined to perform feedforward compensation to adjust the leg's vertical height, balancing the platform's wheel motion stability and adaptive attitude control accuracy. Furthermore, considering the momentum and angular momentum of the platform, the virtual driving force at the wheel end is optimized by the quadratic programming algorithm to solve the feedforward compensation torque and thus enable the precise control of platform motion. The simulation results show that the proposed method can improve the adaptive attitude control accuracy and tire driving stability of the wheeled-legged mobile platform, laying the foundation for its performing reconnaissance and other tasks in complex working conditions.

Key words: wheel-legged mobile platform, feedforward compensation, wheel-ground contact, real-time estimation, attitude control

CLC Number:

TJ301

LIU Hui, LIU Baoshuai, LIAO Dengting, HAN Lijin, CUI Shan. Adaptive Attitude Control of Wheel-legged Mobile Platform Based on Feedforward Compensation[J]. Acta Armamentarii, 2023, 44(9): 2756-2767.

Figures/Tables 17

Fig.1 Overall architecture of wheel-legged mobile platform

Table 1 Key parameters of wheel-legged mobile platform

类别	参数	数值
	平台质量m/kg	50
	负载质量m_l/kg	10
	自由度n	18
结构参数	外廓长L_b/mm	850
	外廓宽L_w/mm	350
	大腿长度L₁/mm	300
	小腿长度L₂/mm	290
	轮胎半径R_w/mm
关节电机	额定扭矩τ_jm,rate/(N·m)	48
	峰值扭矩τ_jm,max/(N·m)	144
轮边电机	额定扭矩τ_wm,rate/(N·m)	8.3
	峰值扭矩τ_wm,max/(N·m)	24.8

Fig.2 Definitions of the coordinates and motion space of wheel-legged mobile platform

Fig.3 Adaptive attitude control strategy based on feedforward compensation

Fig.4 Definition of the front-left leg coordinates

Fig.5 Real-time compensation algorithm for vehicle attitude

Fig.6 Virtual model of the center of mass of wheel-legged mobile platform

Fig.7 Schematic diagram of the operation and working conditions of wheel-legged mobile platform

Fig.8 Wheel-legged mobile platform in motion

Fig.9 Simulation results of attitude angle of the platform CoM

Fig.10 Simulation results of longitudinal velocity and position of the platform CoM

Fig.11 Simulation results of vertical velocity and position of the platform CoM

Fig.12 Joint angles and torques of the front-left and front-right legs of the wheel-legged mobile platform

Fig.13 Comparison of wheel-ground contact command results of different legs

Fig.14 The simulation results of the wheel-ground contact force of wheel-legged mobile platform

Table 2 Comparison of simulation results

姿态角	误差	带前馈补偿策略	无前馈补偿策略
俯仰角	最大误差	-0.862°	-0.954°
	平均误差	-0.276°	-0.316°
侧倾角	最大误差	0.369°	0.369°
	平均误差	0.102°	0.102°

Fig.15 Computing time with QP algorithm

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