US 4,745,812 AGranted

Triaxial tactile sensor

AssigneeThe United States of America as represented by the Secretary of the Army

InventorsCharles A. Amazeen, Steven S. Bishop

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Abstract

The sensitive high resolution microminiature tactile sensor comprises an array of unique micromachined bossed silicon transducer cells in conjunction with requisite electrical circuitry and components, which collectively provide an ability to sense torque by detecting both normal and lateral applied loads, thereby opening a new frontier in tactile sensing. One preferred embodiment comprises a four column by four row array arrangement providing sixteen unique bossed closely spaced silicon diaphragm tactile transducer elements or sensors fabricated from a silicon body member. Collectively the close spacing between the microminiature tactile sensing elements approaches the resolution of the human hand. Electrical signal information from sensor-incorporated internal and external related circuitry components can be analyzed via computer devices to yield specific loading characteristics on the sensor surface. The upper surface of the transducer cell array is protectively covered with a thin polymer layer. The related circuitry may be fabricated by various known processes including diffused piezoresistive areas and deposited thin film conducting strips and tap-off points. These areas and related conductive circuitry for each of the microsmall sensor elements are configurable as two Wheatstone bridges which thereby help provide for the measurement of both normal and lateral load component magnitudes.

A very sensitive, high resolution, transducer array-type tactile sensor adaptable for use with various electro-mechanical and fluidic or pneumatic mechanisms and manipulators including robot end-effectors, for determining lateral or shear forces in conjunction with normal force measurement to aid in the determining of sensor-applied mechanical to electrical transduction forces which in turn help determine any object slip and/or object rotation in the grasp of a robot end-effector;

said sensor comprising in combination:
(a) a micro-thinned silicon wafer main body member 12 having top and bottom surfaces and a predetermined plurality of closely spaced microminature, tactile sensor boss elements 16 forming an array, each boss element 16 disposed centrally of and projecting upwardly above the top surface from a reduced body thickness portion constituting an annular more flexible diaphragm portion 14, said bossed tactile sensor elements 16 and their respective diaphragm portions 14 being susceptible to mechanical perturbative movement from various applied forces including triaxial forces as applied to the various tactile boss elements surfaces;
(b) lower support layer means 18 upon which said main body member 12 via its bottom surface is engagingly supported, said layer means 18 being constituted by a layer of material which is thermally compatible to reduce any thermal stress gradient between said body member and support layer, said support layer having a corresponding plurality of recessed areas 19 corresponding generally in size and alignment location to that of the said diaphragms and tactile sensor boss elements 16;
and
(c) circuit means C1, C2 in association with said tactile sensor elements 16 to help constitute the transducer array including circuit portions C1 fabricated directly in conjunction with said main body 12 and support layer means 18, to generate electrical signals responsive to mechanical perturbation across said tactile sensor elements 16, with said electrical signals being adaptable for interpretive processing to effectively determine any object slip and/or object rotation of an object in the grasp of a robot end-effector.

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Abstract

Claims14