Improved force control through visual servoing

Force controlled manipulation is a common technique for compliantly contacting and manipulating uncertain environments. Visual servoing is effective for reducing alignment uncertainties between objects using imprecisely calibrated camera-lens-manipulator systems. These two types of manipulator feedback, force and vision, represent complementary sensing modalities; visual feedback provides information over a relatively large area of the workspace without requiring contact with the environment, and force feedback provides highly localized and precise information upon contact. This paper presents three different strategies which combine force and vision within the feedback loop of a manipulator, traded control, hybrid control, and shared control. A discussion of the types of tasks that benefit from the strategies is included, as well as experimental results which show that the use of visual servoing to stably guide a manipulator simplifies the force control problem by allowing the effective use of low gain force control with relatively large stability margins.