Providing the user with high-fidelity force feedback has persistently challenged the field of telerobotics. This paper presents a new approach for achieving stable, high-gain force reflection via cancellation of the master mechanism's induced motion. In a classic position-force controller, high force-feedback levels drive the system's internal master-slave loop unstable during contact with the remote environment. Lowering the force-feedback gain ensures stability but diminishes the haptic cues available to the user, masking contacts and preventing hard objects from feeling appropriately stiff. The proposed cancellation approach permits high levels of force feedback by attenuating only the controller's internal loop. Using a model of the master mechanism's response to applied force feedback, an estimate of induced high-frequency movement is subtracted from the master's measured position to approximate the user's intended path for the slave. The cancellation technique is described, modeled, and validated herein, including testing on a one-degree-of-freedom telerobotic system. It is shown to improve the feel of the system, tripling the testbed's achievable force-feedback gain without compromising stability.
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