Source: https://patents.justia.com/patent/4198539
Timestamp: 2019-07-17 15:33:03
Document Index: 670278925

Matched Legal Cases: ['arts 56', 'arts 56', 'art 56', 'arts 56', 'art 86', 'arts 92', 'art 92']

US Patent for System for producing electric field with predetermined characteristics and edge terminations for resistance planes therefor Patent (Patent # 4,198,539 issued April 15, 1980) - Justia Patents Search
Justia Patents US Patent for System for producing electric field with predetermined characteristics and edge terminations for resistance planes therefor Patent (Patent # 4,198,539)
Jan 5, 1978 - Peptek, Inc.
Latest Peptek, Inc. Patents:
I have discovered that this is erroneous. Let X and Y axes intersect at the center of a square plane with sides of 2 units length parallel to the axes. If the current density in the plane is assumed to have a uniform value .iota. parallel to the Y axis (perpendicular to the Y electrodes), a current must flow in each Y electrode with the following distribution: ##EQU1## If the resistance of each electrode is R, this current I(x) will produce the following voltage distribution, relative to the center of the electrode, in each Y electrode: ##EQU2## Therefore, it is erroneous to say that the Y electrodes are maintained at uniform potentials throughout their entire lengths. For a ratio of ten to one for the resistivity of the plane and resistance of the electrode, respectively, as suggested by Becker, Eqn. 2 gives a potential difference between the centers of the Y electrodes that is 2.5% lower than the potential difference between the ends. The variation in voltage along the Y electrodes causes the actual current density in the plane to be nonuniform in the Y axis and to also have a small X-axis component. The nonuniformity in current density produces a nonlinear potential distribution. This nonlinearity can be reduced by increasing the ratio of the resistivity of the plane to the resistance of the electrodes, but only at a penalty of increased power dissipation in the electrodes or undesirably high resistivity of the plane surface, or both.
"Referring to FIG. 10, there is shown a preferred tablet arrangement that is especially useful when using practical resistive materials having less than ideal resistance characteristics. The tablet 12' is of generally pin cushion configuration bounded by parabolic low resistivity strips 15', 16', 17' and 18' of width w and peak deflection from a chord joining their ends of d. If the resistance of each strip 15', 16', 17' and 18' is R and the length of a chord spanning each strip D, the relationship of the quantities is given by d/D=R/.rho.. A typical value of the resistivity .rho. is 2,000 ohms per square while that for R of the parabolic strips is 10 ohms per square."
FIG. 2 shows the preferred form of this invention, in which an electric field is created whose uniformity is limited only by the state of the art of fabricating resistive materials. Plane surface 51 includes a rectangular square having corners a, b, c, and d and is composed of resistance material of uniform resistivity. Electrodes 52-55 are of low resistivity relative to the resistivity of plane surface 51. These electrodes can be fabricated from the same material as plane surface 51 by appropriate control of the cross-sectional thickness of the plane surface and electrodes, or they can be created by adding a layer of lower-resistivity material along the edges of the plane surface by various printing techniques, such as silk screen printing. Connecting parts 56-59 consist of extensions of the square plane surface 51 connecting it to the four electrodes. If the resistivity per square of both the plane surface 51 and the connecting parts 56-59 is R.sub.1, the resistance of each of the electrodes 52-55 is R.sub.2, and the length of each side of the square is 2, then the boundary between connecting part 56 and electrode 52 is described by: ##EQU3## where the origins of the X and Y axes are at the center of the square. The other boundaries are similar. One terminal 60ab of voltage source 60 is connected to the ends of electrode 52 through equal-valued resistors 62 and 63, and the other terminal 60cd of voltage source 60 is connected to the ends of electrode 53 through equal-valued resistors 64 and 65. The other voltage source 61 is similarly connected to the ends of electrodes 54 and 55 through resistors 66-69.
The voltage sources are preferably floating relative to each other. In this embodiment, the ends of the electrodes are resistively connected together by balancing resistors 70-73. Electrodes 52-55 are identical and preferably have a resistance one-tenth the resistivity per square of the plane. In theory their cross-sectional area should change slightly along their length to give equal increments in resistance for equal increments in distance along the adjacent edge of the square; for most purposes the error caused by a uniform cross-sectional area is negligible. Resistors 62-69 are identical and may conveniently have the same resistance as the electrodes 52-55. Resistors 70-73 have the value: ##EQU4## where R.sub.1 is the resistivity per square of the plane 51, R.sub.2 is the resistance of the electrodes 52-55, and R.sub.3 is the resistance of resistors 62-69.
FIG. 3 shows a simpler version of the arrangement of FIG. 2 in which summing amplifiers 74-77 isolate the voltage sources from each other so they do not have to be floating. The connections to the plane are simplified by removing resistors 70-73 of FIG. 2 and extending the electrodes a short distance beyond the boundary with the connecting parts 56', 57', 58' and 59' as indicated at 52a, 52b, 53c, 53d, 54a, 54d, 55b and 55c, respectively. This distance, as a fraction of the length of one side of the square, is given by: ##EQU5## For a ratio of R.sub.2 /R.sub.1 of 0.1, this simplification causes an error at the corners of about 0.25%.
FIG. 4 shows a further embodiment for fabricating the rectangular square plane surface 51", electrodes 52", 53", 54" and 55", and connecting parts from the same material. This has the practical advantage that the absolute value of resistivity of the material becomes unimportant. Whereas the resistivities of both the plane and the electrodes must be controlled in the embodiments of FIG. 2 and FIG. 3 in order to control the ratio R.sub.2 /R.sub.1, in the embodiment of FIG. 4 this ratio is controlled by geometry and is independent of absolute resistivity.
FIG. 8 shows a different form of the invention. Plane surface 81 is surrounded by four center-fed electrodes 82, 83, 84, and 85. These electrodes are joined at their ends. The boundary between connecting part 86 and electrode 82 is described by: ##EQU6## where the origins of the X and Y axes are at the center of the square, R.sub.1 is the resistivity of the plane surface, and R.sub.2 is the resistance of the electrode. The other boundaries are similar. The geometry of the figure is for a ratio R.sub.2 /R.sub.1 equal to 0.1. If the voltage sources 89 and 90 are floating with respect to each other, the current density will be the same in amplitude and direction everywhere in plane surface 81, and the orthogonal vector components parallel to the X and Y axes will be proportional everywhere to the X and Y applied voltages. The techniques illustrated by FIGS. 5, 6 and 7 can also be used to fabricate the structure of FIG. 8.
For example, in said Human-Machine Interface Apparatus the phase of the field generated by the arrangement shown in that patent application's FIG. 5 is given (along one axis) by: ##EQU7## where .phi..sub.x is the phase angle relative to a first edge at a distance x from said first edge; .phi..sub.1 is the phase difference between said first edge and the opposite edge; and L is the length from said first edge to said opposite edge. This phase angle .phi..sub.x has a maximum deviation of 4.52% from the desired function:
.phi..sub.n =(x/L).phi..sub.1 (8)
FIG. 9 shows a trapezoidal plane surface 91 of uniform resistivity, bounded on two sides by connecting parts 92 and 93 of the same resistivity and electrodes 94 and 95 with resistivity typically 1/10 that of the plane surface. If the length of the shorter base of the tapezoid is taken to be 2 units, the height is taken to be 2 units, and the center of the shorter base is taken to be zero in both X and Y axes, the boundary between connecting part 92 and electrode 94 is described by: ##EQU8## where R.sub.1 is the resistivity of the plane surface and R.sub.2 is the resistance of the electrode. A resistor 96 with value 2R.sub.2 is connected between the ends of the electrodes adjacent to the shorter base, and a voltage source 97 is connected to the other two ends. A uniform electric field is created in the trapezoidal plane surface with magnitude proportional to the voltage applied by the voltage source to the electrodes. A three-dimensional combination of these trapezoidal surfaces is shown in FIG. 11 and discussed under the heading "Three-Dimensional Fields."
1. In combination with means having a resistive surface, a system of producing an electric field having predetermined electrical energy distribution characteristics along a first direction and predetermined electrical energy distribution characteristics along a second direction, said second direction being transversely oriented with respect to said first direction comprising,
said resistive surface being provided with a first pair of opposed lateral edges and a second pair of opposed lateral edges, each of said laterally opposed edges having resistive electrode means therealong for distributively passing an electrical current into said resistive surface at incremental points of said opposed edges, respectively, and including resistance means for adjusting the distribution of current into said incremental points of said opposed edges of said resistive surface to thereby control the current supplied to said incremental points of said surface at the lateral edges thereof so as to establish a current flow between opposed lateral edges, and each said resistive electrode having a substantially uniform resistance per unit length, and said resistive surface including resistive edge extensions at a plurality of sequential points therealong, respectively, for limiting the current removed from said electrode at sequential points therealong, respectively,
each said resistive electrode including a plurality of distributed conductor members along said laterally opposed edges, said distributed conductor members being carried by and in conductive contact with the surface of said resistive surface along the length of each distributed conductor member.
2. A current distributor for supplying electrical current to the edges of a rectangular resistive plane whereby a sequential series of points beginning at one edge of said rectangular resistive plane have currents therealong, comprising a resistive electrode member,
and a plurality of resistive members sequentially connected between said electrode and said edge of said resistive plane, said resistance members having electrical resistance values which vary in a predetermined manner as a function of the distance from a first selected point at the edge of the plane to a second selected point thereof.
3. The invention defined in claim 2 wherein said resistive plane is rectangular and said variation in the value of said connecting resistances is parabolic.
6. An apparatus for producing a two-dimensional electric field as defined in claim 5 including a plurality of electrode means having low resistance per unit length relative to the resistance of said rectangular resistive surface,
resistive connecting means, each providing a resistive connection between one side of said rectangular resistive surface and one of said electrodes, respectively, such that the resistance of said connection is a function of distance from the center of said side of said rectangular resistive surface,
and means for applying excitation signals to the ends of said electrodes such that when a potential difference exists between the ends of a first electrode the same potential difference exists between the ends of the electrode connected to the opposite side of said rectangular resistive surface and the same potential relationship exists between corresponding points on the two sides of said rectangular resistive surface adjacent to said first electrode.
7. An apparatus for producing a two-dimensional electric field as defined in claim 6, wherein said rectangular resistive surface has uniform resistance per unit area, each of said electrodes has uniform resistance per unit distance parallel to the adjacent side of said rectangular resistive surface, the resistance of each of said connecting parts is a parabolic function of distance from the center of the adjacent side of said rectangular resistive surface, and said two-dimensional electric field has the same magnitude and direction everywhere in said rectangular resistive surface.
14. The invention defined in claim 5 wherein said means for coupling orthogonally related currents to the edges of said rectangular surface include four center fed electrodes having low resistance per unit length relative to the resistance of said resistive surface, means joining the ends of said electrodes, respectively, bounding resistive surfaces connecting said electrodes to said rectangular resistive surface, said bounding resistive surface being defined by ##EQU9## where the origins of the X and Y axes are at the center of said rectangle, R.sub.1 is the resistivity of the said rectangle, and R.sub.2 is the resistivity of the electrode.
19. A human-machine interface apparatus comprising,
a first transducer comprising a resistive surface and means for supporting said resistive surface such that pressure exerted by a human finger thereon transmits a force in a direction normal to said surface, means for coupling orthogonally related currents to the edges of said resistive surface such that a field component parallel to a first side is everywhere proportioned to a first excitation signal as a function of distance from a selected point on said surface and the field component orthogonal to said first side is everywhere proportioned to a second excitation signal as a function of distance from said selected point, and
a second data transducer comprising means mechanically coupled to said resilient surface for translating said force in a direction normal to said surface to a first electrical signal,
means for detecting the position of said human finger in said orthogonal fields and producing second electrical signals, respectively, and
a utilization device coupled to receive said first and said second electrical signals.
20. In a resistive surface, improvements in electrical edge termination to said resistive surface comprising a plurality of rows of conductive segments overlying the edge of said resistive surface, the conductive segments in each row of conductive segments having a length in the direction of said edge which is longer than the length of segments in the row preceding it.
Patent number: 4198539
Assignee: Peptek, Inc. (Bethesda, MD)
Inventor: William Pepper, Jr. (Bethesda, MD)
Application Number: 5/867,256