Abstract:

Legged robots have better performance on discontinuous terrain than that of wheeled robots. However, the dynamic trotting and balance control of a quadruped robot is still a challenging problem, especially when the robot has multi-joint legs. This paper presents a three-dimensional model of a quadruped robot which has 6 Degrees of Freedom (DOF) on torso and 5 DOF on each leg. On the basis of the Spring-Loaded Inverted Pendulum (SLIP) model, body control algorithm is discussed in the first place to figure out how legs work in 3D trotting. Then, motivated by the principle of joint function separation and introducing certain biological characteristics, two joint coordination approaches are developed to produce the trot and provide balance. The robot reaches the highest speed of 2.0 m•s−1, and keeps balance under 250 Kg•m•s−1 lateral disturbance in the simulations. The effectiveness of these approaches is also verified on a prototype robot which runs to 0.83 m•s−1 on the treadmill. The simulations and experiments show that legged robots have good biological properties, such as the ground reaction force, and spring-like leg behavior.

Key words: legged robots, locomotion control, quadruped robot, trotting gait