A study of biped balance control using proportional feedback of ground reaction forces

The ground reaction force is informative for maintaining a biped balance with respect to unknown external forces. From this point of view, we proposed a new control method for static balancing that containing the integral feedback of the ground reaction forces in our previous papers. As the result, the adaptive posture changes are achieved for constant external forces. However, the convergence to the equilibrium posture is not so good because of the integral property of this control method. To improve this problem, the direct, i.e., proportional feedback of ground reaction forces is introduced in this paper. Using the linearization and the transformation to the discrete system, the stability as well as the speed of the convergence is evaluated. The analysis using the root locus method is effectively used to obtain the range of proportional feedback gain of the ground reaction forces for the given parameters of a model. Finally, numerical analyses reveal that the proportional feedback of ground reaction forces slightly improve the speed of the convergence. In conclusion, it is difficult to say that the drastic improvement of the convergence is expected by the proportional feedback of ground reaction forces