Abstract
The control technique for generating whole body motions on wheel-leg robot for dynamic locomotion and balance is a challenging topic. In this paper, a whole body dynamic model is built. It consisted by the torso dynamic model, the wheel-leg dynamic model and the contact force constraint between the wheels and the ground. A whole body control frame is proposed which composed by a torso motion controller, two torque solvers, a slippage predictor and an online trajectory generator. The torso controller plans the coupling wrenches between wheel-legs and torso. The torque solvers for every wheel-leg compute joint torques based on the coupling wrenches computed from the torso controller synchronously. The contact forces can be calculated by the slippage predictor based on the joint torques, then a boolean signal will be transmitted to the online trajectories generator to indicate whether the friction cone constraint will be broken. The online trajectory generator can plan reasonable acceleration trajectory with different boolean signals. The efficiency of this control frame is illustrated by several simulations in virtual simulation environment.
Highlights
Mobile robots have many modes of locomotion, the leg based [1]–[5] and the wheel based modes [6]–[8] have attracted a great deal of attention in recent years
WORK In order to achieve the high performance locomotion and balance control of wheel-leg robot (WLR), this paper has proposed a distribute whole-body dynamic modelling method and a whole-body control frame
The whole-body dynamic model is separated for the torso dynamic model, the wheel-leg floating base dynamic model and the wheel-ground contact dynamic model
Summary
Mobile robots have many modes of locomotion, the leg based [1]–[5] and the wheel based modes [6]–[8] have attracted a great deal of attention in recent years. For WLR, in order to achieve high performance locomotion and dynamic balance control, the dynamic characteristics caused by wheel-legs can not be neglected. The main contributions of this paper are highlighted as follows: 1) Based on the distributed modeling method, the multimodule form model retains all the dynamic characteristics of whole body include the force interaction with torso and wheel-legs, wheels and ground, so it can be called wholebody model. This form is easy to expand when other limbs are added and easy to rewritten a integrated dynamic model of whole body.
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