Dynamic Locomotion Control for Wheeled-legged Hybrid Platform in Complex Terrain

doi:10.12382/bgxb.2023.0636

Abstract

Abstract:

The dynamic and accurate tracking of the center-of-mass reference trajectory in complex terrain is crucial to ensure the stable execution of tasks for wheeled-legged hybrid platform. A dynamic locomotion control strategy is proposed to enhance the terrain adaptability and pose tracking capability of the platform. Taking into account terrain factors, a single rigid body dynamics model including wheel dynamics is established. The system dynamics model is then transformed into the standard form of state-space equations through an approximate simplification. Considering the coupled motion of the wheels and legs, a hybrid locomotion control method based on feedforward and feedback torques is introduced. The quadratic programming algorithm is used to solve the optimal ground reaction forces, and the Jacobian matrix is used to map these forces into the joints for feedforward torque generation. To address the external disturbances caused by the environment that may hinder the system’s ability to perform optimization calculations in a short time frame, the joint torque feedback control is introduced to promptly correct the pose tracking errors. This enables the system to respond rapidly and accurately to the external disturbances, thus effectively improving its robustness and stability. Simulated results demonstrate that the proposed method significantly enhances the dynamic pose tracking accuracy of the platform in complex terrains, ensuring smooth platform operation. This method provides strong support for the engineering application of wheeled-legged hybrid platforms in complex terrains.

Key words: wheeled-legged hybrid platform, complex terrain, single-rigid-body dynamic model, hybrid locomotion control

CLC Number:

TJ301

REN Xiaolei, LIU Hui, HAN Lijin, CHEN Qian, NIE Shida, XIE Jingshuo, CUI Shan. Dynamic Locomotion Control for Wheeled-legged Hybrid Platform in Complex Terrain[J]. Acta Armamentarii, 2024, 45(9): 2993-3003.

Figures/Tables 17

Fig.1 Schematic diagram of the wheeled-legged hybrid platform

Table 1 Main parameters of the system

参数	数值
整车质量m_b/kg	60
大腿质量m_h/kg	3.5
小腿质量m_k/kg	1.5
车轮质量m_w/kg	2.4
大腿长度L₁/mm	300
小腿长度L₂/mm	290
车轮半径r/mm	100
外廓尺寸长:长L_b×宽L_w×高L_h/mm	850×350×260
关节峰值力矩 $τ h, k m a x$ (N·m)	144
车轮峰值力矩 $τ w m a x$ /(N·m)	24.8

Table 1 Main parameters of the system

参数	数值
整车质量m_b/kg	60
大腿质量m_h/kg	3.5
小腿质量m_k/kg	1.5
车轮质量m_w/kg	2.4
大腿长度L₁/mm	300
小腿长度L₂/mm	290
车轮半径r/mm	100
外廓尺寸长:长L_b×宽L_w×高L_h/mm	850×350×260
关节峰值力矩 $τ h, k m a x$ (N·m)	144
车轮峰值力矩 $τ w m a x$ /(N·m)	24.8

Fig.2 Definition of coordinate system

Fig.3 Single rigid body dynamicsmodel in the X-Z plane

Fig.4 Hybrid locomotion control structure

Fig.5 The platform passing through continuous obstacles at a speed of 0.7m/s whent t=9.36s

Table 2 Controller settings

名称	数值
控制量权重	10^-4
姿态角权重	1
垂向位移权重	20
纵向位移权重	0.1
线速度权重	1
K_P,q	0.7
K_D,q	0.025
K_P,w	0.12
K_l,w	0.008

Fig.6 Desired vertical position planning

Fig.7 Longitudinal position and longitudinal speed for the platform CoM

Fig.8 Vertical position and vertical speed for the platform CoM

Fig.9 Roll angle and roll rate for the platform CoM

Fig.10 Pitch angle and pitch rate for the platform CoM

Fig.11 Comparison of RMSEs in two control methods

Fig.12 Wheel-ground vertical force estimation

Fig.13 Joint torque

Fig.14 Joint angle

Fig.15 Computing time of QP algorithm

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