Importance

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Abstract

An apparatus and a method for controlling a feedback force applied by a joystick to a user gripping the control handle of the joystick. In the preferred embodiment, a light path between an infrared light source and a light sensor is interrupted by a user gripping the handle of a joystick. The output signal from the light sensor is employed by a processor to control the feedback force. When based upon the output signal, the processor determines that the user has just gripped the control handle, the processor enables the feedback force to increase slowly, over a sufficiently long time to enable the user to firmly grip the control handle before the feedback force becomes very strong. The processor immediately disables generation of the feedback force as soon as the user releases the control handle. The processor periodically energizes and then de-energizes the light source, determines an average value of the output signal when the light source is both energized and de-energized, and based upon a comparison of these average values, determines if the user's hand gripping the control handle has interrupted the light path between the source and light sensor. Additionally, the processor checks for a failure of the light source, and if detected, halts the generation of the feedback force.

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First Claim