Chapter 6 - Feedback Control with Force and Visual Sensor Fusion

Abstract

Force and vision sensors provide complementary information, yet they are fundamentally different sensing modalities. This implies that traditional sensor integration techniques that require common data representations are not appropriate for combining the feedback from these two disparate sensors. This chapter demonstrates the use of force and vision resolvability for assimilating high-bandwidth visual feedback and high-bandwidth force feedback within the same manipulator feedback loop. By monitoring the resolvability of the two sensing modes with respect to the task, the information provided by the disparate sensors can be seamlessly assimilated during task execution. A nonlinear force-vision servoing algorithm that uses force and vision resolvability to switch between sensing modes, demonstrates the advantages of the assimilation technique. Contact transitions between a stiff manipulator and rigid environment, a system configuration that easily becomes unstable when force control alone is used, are robustly achieved. Experimental results show that the nonlinear controller is able to satisfy simultaneously the conflicting task requirements of fast approach velocities, maintaining stability, minimizing impact forces, and suppressing bounce between the contact surfaces. The proper assimilation of force and vision feedback is the key to the success of this strategy.