Position and force measuring system

• US 4,121,049 A
• Filed: 04/01/1977
• Issued: 10/17/1978
• Est. Priority Date: 04/01/1977
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Roeber, Frederick W.
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/783,538
• Time in Patent Office: 564 Days
• Field of Search: 177/211, 177/210 R, 177/210 C, 177/210 EM, 177/210 FP, 73/141 R, 73/141 A, 73/172, 178/18, 178/19, 178/20
• US Class Current: 178/18.01
• CPC Class Codes: G01G 3/1406 combined with special measuring circuits
• CPC Class Codes: G01L 1/14 by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators
• CPC Class Codes: G06F 3/04142 the force sensing means being located peripherally, e.g. disposed at the corners or at the side of a touch sensing plate
• CPC Class Codes: H01H 2239/052 Strain gauge

Abstract

A position and force measuring system for determining the coordinates and force applied to a point on a rigid plate or surface fixed to a rigid foundation by means of a flexible support mechanism and at least three spaced apart sensors. The sensors each deliver an output signal which is proportional to the applied force and the coordinates of the force. The output signals are fed into a processor which computes the force and the coordinates at which the force is applied.

Claims

1. In combination:

first and second substantially rigid bodies;

spring means interconnecting said rigid bodies, said spring means extending along substantially the entire periphery of said substantially rigid bodies, said spring means restraining lateral movement between said first and second substantially rigid bodies; and

means for producing electrical signals representing a change in distance between portions of said substantially rigid bodies in response to a force applied to one of said bodies.

2. The combination of claim 1 wherein at least one of said substantially rigid bodies comprises:

a plate.

3. The combination of claim 2 wherein said electrical signal producing means comprises:

a plurality of distance transducers positioned at spaced-apart locations near the periphery of said plate.

4. The combination of claim 3 wherein:

said plate is of substantially rectangular shape.

5. The combination of claim 4 wherein:

said plate is of substantially round shape.

6. The combination of claim 3 wherein said spring means comprises:

four springs each having substantially the shape of a hollow half cylinder with extended flange portions, one of said springs being coupled along each edge of said plate.

7. The combination of claim 6 wherein said transducers comprise:

three or more such transducers coupled to said spring means.

8. The combination of claim 7 wherein said transducers comprise:

strain gauges.

9. The combination of claim 3 wherein said spring means comprises:

a layer of elastic material positioned between said rigid bodies.

10. The combination of claim 9 wherein:

said layer of elastic material is substantially continous between said rigid bodies.

11. The combination of claim 9 wherein:

said layer of elastic material has hollow inner portions.

12. The combination of claim 9 wherein said elastic material comprises a material selected from the group comprising:

rubber and plastic.

13. The combination of claim 9 wherein said elastic material comprises:

metal aluminum.

14. The combination of claim 3 further comprising:

means for producing one or more output signals representing the position of application of said force in response to signals produced by said electrical signal producing means.

15. The combination of claim 3 further comprising:

means for producing an output signal representing the magnitude of said force in response to signals produced by said electrical signal producing means.

16. A system for measuring the point of application of static or dynamic force on an input surface and simultaneously determining the magnitude of said static or dynamic force, comprising in combination:

(a) an input plate with an exposed surface subject to the application of localized force applied so as to have a component which is normal to the point where the force is applied;

(b) a base plate;

(c) one or more springs coupling said input surface to said base plate, said one or more springs extending along the major portion of the peripheries of said input plate and said base plate, said one or more springs preventing lateral motion between said input surface and said rigid body;

(d) four sensors operatively mounted at spaced-apart points, each of said sensors producing a signal varying with a component of the applied force acting upon said exposed surface; and

(e) calculating means with inputs coupled to said sensors for deriving from signals therefrom two output signals proportional to the coordinates of the point of application of said force with reference to a pre-established set of axes and an output signal proportional to the magnitude of said input force, said calculating means comprising;

(i) a first through fourth sensor amplifier means coupled to each of said sensors;

(ii) first summing means for summing the outputs of said amplifiers;

(iii) an inverter coupled to the output of said summing means, the output of said inverter producing a first output signal proportional to the magnitude of the vertical component of the input force;

(iv) a first divider and a second divider, said first output signal being coupled to form the denominator signal for said dividers;

(v) a second summing means, outputs of said first and second sensor amplifiers being coupled to an input of said second summing means;

(vi) third summing means, an input of said third summing means being coupled to outputs of said second summing means and said third and fourth sensor amplifiers, the output of said third summing means forming the numerator signal of the first divider;

(vii) fourth summing means, inputs of said fourth summing means being coupled to outputs of said first and fourth sensor amplifier;

(viii) fifth summing means, inputs of said fifth summing means being coupled to outputs of said fourth summing means and said second and third sensor amplifiers, the output of said fifth summing means forming the numerator signal of the second divider, the outputs of said dividers representing the coordinates of the position of application of said force.

20. A system as defined in claim 16 wherein said sensors comprise:

strain gauges.

21. A system as defined in claim 16 wherein said sensors comprise:

piezoelectric transducers.

22. A system as defined in claim 16 wherein said sensors comprise:

linear displacement transducers.

23. A system as defined in claim 16 wherein said sensors comprise:

proximity measurement transducers.

24. A system as defined in claim 16 further comprising:

a minimum of three damper elements interconnecting the input plate and the base plate for diminishing the effect of vibrations on the sensor outputs.

17. A system for measuring the point of application of static or dynamic force on an input surface and simultaneously determining the magnitude of said static or dynamic force, comprising in combination:

(a) an input plate with an exposed surface subject to the application of localized force applied so as to have a component which is normal to the point where the force is applied;

(b) a base plate;

(c) one or more springs coupling said input surface to said base plate, said one or more springs extending along the major portion of the peripheries of said input plate and said base plate, said one or more springs preventing lateral motion between said input surface and said rigid body;

(d) four sensors operatively mounted at spaced-apart points, each of said sensors producing a signal varying with a component of the applied force acting upon said exposed surface; and

(e) calculating means with inputs coupled to said sensors for deriving from signals therefrom two output signals proportional to the coordinates of the point of application of said force with reference to a pre-established set of axes and an output signal proportional to the magnitude of said input force, said calculating means comprising;

(i) first through said fourth sensor amplifiers coupled to each of said sensors;

(ii) means for summing outputs of all of said sensor amplifiers;

(iii) an inverter coupled to the output of said summing means;

(iv) first through fourth sample-and-hold circuits, inputs of each of said sample-and-hold circuits being coupled to outputs of said first through fourth sensor amplifiers respectively; and

(v) means for sequentially coupling outputs of said sample-and-hold circuits to output utilization means in response to output signals from said inverter means.

18. The combination of claim 17 wherein said sequential coupling means comprises:

a multiplexer.

19. The system as defined in claim 18 further comprising:

means for producing a binary count in response to said output signals from said inverter means, said multiplexer operating in response to said binary count.

25. A system as defined in claim 17 wherein said sensors comprise:

strain gauges.

26. A system as defined in claim 17 wherein said sensors comprise:

piezoelectric transducers.

27. A system as defined in claim 17 wherein said sensors comprise:

linear displacement transducers.

28. A system as defined in claim 17 wherein said sensors comprise:

proximity measurement transducers.