Design of a Discrete Series Elastic Actuated Spine for Quadruped Robots

doi:10.12382/bgxb.2024.0350

Abstract

Abstract:

In order to improve the stride length and impact resistance of quadruped robots during movement,a cheetah is used as a bionic object to analyze the motion mechanism,and a discrete bionic spine joint with series elastic actuator (SEA) is designed.The SEA is used as the driving unit,which is arranged between the spinal box and leg joints to simulate the characteristics of biological muscles and provide passive compliance.The overall design of the spine adopts 2-DoFs discrete configuration to achieve two running postures of extension and curling,thus improving the stride length.Based on the D-H parameter method,a kinematic model of quadruped robot with 2-DoF discrete spine is established,and the stride length of quadruped robot is analyzed.An experimental platform of quadruped robots with SEA spine is constructed for performance testing experiment.The experimental results under the bound gait show that the stride length of quadruped robot with SEA spine is increased by 73.72%.Compared with the rigid trunk,the SEA spine joint can reduce the peak torques of front leg thigh motor,front leg calf motor,hind leg thigh motor and hind leg calf motor by 35.2%,12.0%,45.7% and 10.3%,respectively,during jumping.And the mean and standard deviation of the output torque of each joint motor are significantly reduced.

Key words: discrete spine, series elastic actuator, stride length increase, torque buffering

CLC Number:

TP242

SU Jiahao, LIU Siyu, LU Chunlei, GUO Zhao, WANG Zhirui, YAN Tong, DANG Ruina, SU Bo. Design of a Discrete Series Elastic Actuated Spine for Quadruped Robots[J]. Acta Armamentarii, 2025, 46(4): 240350-.

Figures/Tables 25

Fig.1 Two gaits of a cheetah during running

Fig.2 Overall structural design of spine

Fig.3 SEA structure

Fig.4 Installation diagram of SEA

Fig.5 Experimental overall prototype

Fig.6 Compression process of SEA

Fig.7 Schematic diagram of SEA

Fig.8 Establishment of single-leg kinematic coordinate system

Table 1 Single leg D-H parameters

i	θ_i/(°)	d_i/mm	α_i/(°)	∂_i/mm
1		d₀		∂₁
1'	θ₁+90		90
2		d₁
3	θ₂	d₂	-90
4	θ₃	d₃		∂₃
5	θ₄-90			∂₄

Fig.9 Comparison of foot-end workspaces with and without spine

Fig.10 Cycloid trajectory

Fig.11 Motion trajectories of leg joints under bound gait

Fig.12 Motion trajectories of leg joints under running gait

Fig.13 Comparison of stride lengths with and without spine

Fig.14 Equivalent stiffness test platform

Fig.15 Equivalent stiffness curve

Fig.16 Frequency response experiment

Fig.17 Impact test experimental platform

Fig.18 Motor torques under different impacts

Table 2 Experiments of torque buffering with SEA and without SEA in terms of peak torque

下落高度mm	有SEA峰值力矩/ (N·m)	无SEA峰值力矩/(N·m)	减少百分比/%
200	6.97	13.30	47.6%
400	8.78	17.93	51.0%
600	9.10	21.76	58.2%

Fig.19 Prototype stride test platform

Fig.20 Stride length comparison of bound gait

Fig.21 Jump buffer experiment

Fig.22 Comparison of position and torque of each motor

Table 3 Comparison of motor torque data with and without SEA spine N·m

电机	有SEA脊柱			无SEA脊柱			有SEA脊柱峰值力矩减少百分比/%
电机	峰值		标准差	峰值		标准差	有SEA脊柱峰值力矩减少百分比/%
前腿大腿	3.70	-3.42	1.09	5.71	-2.80	1.60	35.2
前腿小腿	0.52	-16.94	2.41	2.23	-19.23	3.31	12.0
后腿大腿	0.37	-6.64	1.18	1.32	-12.23	1.81	45.7
后腿小腿	0.54	-15.80	2.88	1.11	-17.61	3.15	10.3
脊柱	1.36	-3.51	1.02

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