Force sensing apparatus

• US 4,635,479 A
• Filed: 01/15/1986
• Issued: 01/13/1987
• Est. Priority Date: 08/29/1984
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Brock, David L., Salisbury, John K. Jr.
• Primary Examiner(s): WOODIEL, DONALD
• Application Number:
  US06/819,462
• Time in Patent Office: 363 Days
• Field of Search: 73/862.04, 73/862.05, 73/862.06, 73/170 A, 73/188, 73/189
• US Class Current: 73/862.045
• CPC Class Codes: B25J 13/02 Hand grip control means handles or pedals for crane control B66C13/56; for measuring the force applied to control members G01L5/22; hand-held casings for switching devices, e.g. joy-sticks H01H9/0214
• CPC Class Codes: B25J 13/082 Grasping-force detectors in general G01L5/16, G01L5/22
• CPC Class Codes: B25J 17/0208 Compliance devices
• CPC Class Codes: G01L 1/2206 Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
• CPC Class Codes: G01L 5/1627 of strain gauges using piezoresistors G01L5/162
• CPC Class Codes: G01L 5/226 to manipulators, e.g. the force due to gripping
• CPC Class Codes: H01H 2239/052 Strain gauge

Abstract

Force sensing apparatus for determining the location, magnitude and direction of a force on a three dimensional surface in which there is a convex surface (10-12) of known configuration mounted on a pedestal 22. A cruciform load cell (16) equipped with strain gauges (60-62) measures forces applied to the convex surface through the medium of a flexible force transmitter member (64).

Claims

1. Force sensing apparatus for determining the location, magnitude and direction of a force exerted through a point contact on a three dimensional surface comprising:

a movable member having a convex surface of known configuration,

a pedestal,

a cross having flexible arms fixed to the pedestal,

a flexible force transmitting member surrounding and attached to each arm, limited portions of the force transmitting member being attached to the movable member, the remainder of the force transmitting member being spaced from the movable member,

at least one strain gauges secured to each arm of the cross whereby a force applied to the convex surface through a point contact and the resultant moments of that force are transmitted through the flexible force transmitting member to the flexible arms resulting in strain measurable by the gauges.

2. Force sensing apparatus according to claim 1 wherein there are means to limit the amount of strain transmitted to the arms.

3. Force sensing apparatus according to claim 1 wherein each arm is constructed to flex in two planes normal to each other and wherein strain gauge mechanism is associated with each plane to measure the strain transmitted to it.

4. Force sensing apparatus according to claim 1 wherein the strain gauges are connected to a computer which computes the location, magnitude and direction of the force.

5. Force sensing apparatus for determining the location, magnitude and direction of a force exerted through a point contact on a three dimensional surface comprising:

a movable member having a convex surface of known configuration,

a pedestal,

equal length flexible arms with their center fixed to the pedestal,

a flexible force transmitting member substantially surrounding the equal length arms and having the same number of sides as there are arms, the arms being attached symmetrically to the sides of the force transmitting member and the corners of the force transmitting member being symmetrically attached to the movable member,

at least two strain gauges secured to each arm whereby a force applied to the convex surface through a point contact and the resultant moments of that force are transmitted to the flexible arms resulting in strain measurable by the gauges.

6. Force sensing apparatus according to claim 5 wherein there are means to limit the amount of strain transmitted to the arms.

7. Force sensing apparatus according to claim 5 wherein each arm is constructed to flex in two planes normal to each other and wherein strain gauge mechanism is associated with each plane to measure the strain transmitted to it.

8. Force sensing apparatus according to claim 5 wherein the strain gauges are connected to a computer which computes the location, magnitude and direction of the force.

9. Force sensing apparatus for determining the location, magnitude and direction of a force exerted through a point contact on a three dimensional surface comprising:

a movable member having a convex surface of known configuration,

a pedestal,

a cross having equal length flexible arms with its center fixed to the pedestal,

a flexible force transmitting frame surrounding the cross and having sides of equal length,

the arms of the cross being attached to the mid points of four of the sides of the frame and four corners of the frame being attached to the movable member,

at least one strain gauge secured to each arm of the cross,

whereby a force applied to the sphere through a point contact and the resultant moments of that force are transmitted to the flexible arms resulting in strain measurable by the strain gauges.

10. Force sensing apparatus according to claim 9 wherein there are means to limit the amount of strain transmitted to the arms.

11. Force sensing apparatus according to claim 9 wherein each arm is constructed to flex in two planes normal to each other and wherein strain gauge mechanism is associated with each plane to measure the strain transmitted to it.

12. Force sensing apparatus according to claim 9 wherein the strain gauges are connected to a computer which computes the location, magnitude and direction of the force.

13. Force sensing apparatus for determining the location, magnitude and direction of a force exerted through a point contact on a three dimensional surface comprising:

a hollow sphere;

a pedestal passing freely into the sphere and terminating substantially at its center;

a cross having equal length flexible arms within the sphere with its center fixed to the pedestal,

a flexible force transmitting frame surrounding the cross and having sides of equal length,

the arms of the cross being attached to the mid points of four of the sides of the frame and four corners of the frame being attached to the sphere,

at least two strain gauges secured to each arm of the cross,

whereby a force applied to the sphere through a point contact and the resultant moments of that force are transmitted to the flexible arms resulting in strain measurable by the strain gauges.

14. Force sensing apparatus according to claim 13 wherein there are means to limit the amount of strain transmitted to the arms.

15. Force sensing apparatus according to claim 13 wherein each arm is constructed to flex in two planes normal to each other and wherein strain gauge mechanism is associated with each plane to measure the strain transmitted to it.

16. Force sensing apparatus according to claim 13 wherein the strain gauges are connected to a computer which computes the location, magnitude and direction of the force.