Kinematics and Dynamics

6.6 Conclusions

Many authors recommend not taking leg dynamics into account in the control of walking robots. The high gearing employed is often the reason for neglecting the effect of leg dynamics on trajectory control. However, the use of a gear reduction high enough to ignore leg dynamics implies a significant increase in backlash, friction and elasticity in the transmission system. These undesired additional effects are much more difficult to model than the dynamics of the mechanical part. One main conclusion of this chapter is that considering robot legs as massless systems is not always the best option. The effect of leg dynamics can be appreciable, and moreover it can be used to improve the control system. To ilustrate this, we have derived a precise, accurate model of a robotic leg. Experiments have been done using a real leg prototype to analyze the torque contributions of different dynamic components during real leg trajectories. Detailed analysis of leg dynamics has led us to a simplified, accurate model of the dynamic effect of the leg on motion control.