Piezoresistive foot pressure measurement method and apparatus
First Claim
1. A device for measuring forces exerted on a discrete location of a surface, said device comprising at least a first normal force sensing element (30), said element containing a piezoresistive material defined as having a hulk electrical resistance that varies in a predetermined way with normal forces exerted thereon, said piezoresistive material being in the form of a resilient pad (33) sandwiched between a pair of first and second conductor strip laminations comprising thin, flexible insulating sheets having formed on the inner facing surfaces thereof at least one row (32) and at least one column (31) conductor strip, respectively, said row and column conductor strips being in electrically conductive contact with opposite sides of said piezoresistive pad, at least one of said resilient pads, said row and said column conductor strips comprising a woven mesh fabric (34) impregnated with electrically conductive material, whereby the electrical resistance between a selected row and column conductor intersection defining a particular region normally aligned with said pads in a predetermined function of the normal force exerted on said region.
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Accused Products
Abstract
A method and apparatus (68, 40) for measuring pressures exerted on 6 human feet or horses'"'"' hooves comprises a rectangular array of piezoresistive force sensors encapsulated in a thin polymer package (40) that is inserted into a shoe, or incorporated into a sock that may be pulled over a foot or hoof. The preferred embodiment employs novel piezoresistive normal force or pressure sensing elements (36) which include a polymer fabric mesh impregnated with conductive particles suspended in an elastomeric vehicle, preferably silicone rubber. The piezoresistive mesh layer (33) is sandwiched between an array of row (34) and column (31) conductor strip laminations, preferably made of a nylon mesh impregnated with printed metallic paths. In a variation (100) of the basic embodiment, each normal force sensor element (30) is bordered by laterally and longitudinally disposed pairs (80) of shear force sensor elements, each of the latter comprising a pair of adjacent resilient piezoresistive pads (83) that have longitudinally contacting lateral surfaces. The pads are slidably movable, and when urged into more or less intimate contact in response to shear forces directed normal to their tangent contact plane, the electrical resistance between the pads varies in a predetermined way as a function of the shear forces.
169 Citations
31 Claims
- 1. A device for measuring forces exerted on a discrete location of a surface, said device comprising at least a first normal force sensing element (30), said element containing a piezoresistive material defined as having a hulk electrical resistance that varies in a predetermined way with normal forces exerted thereon, said piezoresistive material being in the form of a resilient pad (33) sandwiched between a pair of first and second conductor strip laminations comprising thin, flexible insulating sheets having formed on the inner facing surfaces thereof at least one row (32) and at least one column (31) conductor strip, respectively, said row and column conductor strips being in electrically conductive contact with opposite sides of said piezoresistive pad, at least one of said resilient pads, said row and said column conductor strips comprising a woven mesh fabric (34) impregnated with electrically conductive material, whereby the electrical resistance between a selected row and column conductor intersection defining a particular region normally aligned with said pads in a predetermined function of the normal force exerted on said region.
- 14. A device for measuring shear forces exerted on discrete locations of a surface which the apparatus is placed in contact with, said device comprising a planar two dimensional array of individual shear force sensing elements (80), each of said shear force sensing elements comprising a pair of laterally adjacent piezoresistive pads (83A, 83B) having tangentially contacting peripheral surfaces (84A, 84B), the electrical resistance between said pad pair members varying in a predetermined way with shear forces directed perpendicularly to the tangent plane and urging said contacting surfaces of said pad pair into greater or lesser conductive contact, said pairs of pads being sandwiched between a pair of first and second conductor strip laminations comprising thin, flexible electrically insulating sheets having formed on the inner facing surfaces thereof adjacent rows of spaced apart row (82) and column (81) conductor strips, respectively, said row and column conductor strips being in electrically conductive contact with a separate one of each pair of pads, whereby measurement of the electrical resistance between the pads of a selected pair of said pads is measured by applying a voltage between said selected row and column conductor strips, thereby determining shear forces exerted on said pad pair.
Specification