H∞ control for robotic systems using the passivity concept

Nonlinear H_∞ optimal control theory has been well researched in previous years. However, proposed control schemes are quite complicated and hardly feasible in construction of a controller actually for robotic systems. As for robot control, it has been shown that the passivity concept plays a key role in constructing good controllers for dexterous motion with or without tool endpoint constraint. In this paper, the authors propose an H_∞-optimal tuning method for these controllers established on the passivity-based concept. By using the passivity concept, the conditions for H_∞-optimal tuning can be obtained in a simple and clear form. As an application of this H_∞ control scheme, it is shown that, even for a trajectory tracking problem for a robot under geometrical endpoint constraint, model-based hybrid adaptive control methods previously proposed can be extended to cope with H_∞ tuning in the sense of disturbance attenuation