Multi-speed capacitive displacement encoder
First Claim
1. A capacitive angle encoder for sensing rotation of a shaft, the encoder comprising:
- at least one stator, comprising an electrostatic field transmitter, which is adapted to generate an electrostatic field;
an electrostatic field receiver, which is adapted to receive the electrostatic field and generate a signal responsive thereto;
a rotor, adapted to rotate with the shaft, and having coarse and fine periodic electrically-active patterns thereon, the fine pattern comprising a sinusoidal pattern disposed circumferentially around the shaft, wherein the patterns modulate the electrostatic field responsive to rotation of the shaft by inducing a periodic variation in capacitance between the transmitter and the receiver; and
processing circuitry, coupled to the receiver so as to sense the periodic variation in the signal and to determine, responsively to the periodic variation, coarse and fine measures of a rotation angle of the shaft.
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Accused Products
Abstract
A capacitive motion encoder, for sensing the position of a moving object relative to a stationary object, includes at least one stationary element, coupled to the stationary object and a moving element, coupled to the moving object and in proximity to the stationary element. A field transmitter generates an electrostatic field, which is modulated by a change in capacitance between the stationary and moving elements responsive to relative motion of the elements. A conductive shield, is electrically decoupled from both the moving and the stationary objects, and encloses the moving and stationary elements so as to shield the elements from external electrical interference. Processing circuitry is coupled to sense the modulated electrostatic field and to determine responsive thereto a measure of the position of the moving object.
58 Citations
20 Claims
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1. A capacitive angle encoder for sensing rotation of a shaft, the encoder comprising:
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at least one stator, comprising an electrostatic field transmitter, which is adapted to generate an electrostatic field;
an electrostatic field receiver, which is adapted to receive the electrostatic field and generate a signal responsive thereto;
a rotor, adapted to rotate with the shaft, and having coarse and fine periodic electrically-active patterns thereon, the fine pattern comprising a sinusoidal pattern disposed circumferentially around the shaft, wherein the patterns modulate the electrostatic field responsive to rotation of the shaft by inducing a periodic variation in capacitance between the transmitter and the receiver; and
processing circuitry, coupled to the receiver so as to sense the periodic variation in the signal and to determine, responsively to the periodic variation, coarse and fine measures of a rotation angle of the shaft. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification