Force/torque sensor with hardstops to limit overloading a flexure

Patent metadata

Field	Value
Publication number	US-10732060-B2
Application number	US-201816103931-A
Country	US
Kind code	B2
Filing date	Aug 15, 2018
Priority date	Aug 15, 2018
Publication date	Aug 4, 2020
Grant date	Aug 4, 2020

Abstract

An example device includes a rigid plate, an inner element, a plurality of connecting flexural elements coupled between the inner element and rigid plate, and a hardstop that extends through the inner element and couples to the rigid plate. The inner element has a plurality of reflective surface areas that are configured to reflect light to a sensor. The plurality of connecting flexural elements allow the inner element to move relative to rigid plate. The hardstop contacts the inner element when a load applied on the device exceeds a threshold load.

First claim

I claim:

1. A device, comprising:
a rigid plate comprising an extended portion extending from an inner surface of the rigid plate;
a flexure coupled to the rigid plate, wherein the flexure comprises:
an inner element coupled to a plurality of reflective surface areas, wherein the plurality of reflective surface areas are configured to reflect light to a sensor, wherein the inner element comprises an extended portion extending from an inner surface of the inner element and surrounding an opening of the inner element; wherein the inner surface of the rigid plate faces the inner surface of the inner element; and
a plurality of connecting flexural elements coupled between the inner element and the rigid plate, wherein the plurality of connecting flexural elements are configured to allow the inner element to move relative to the rigid plate; and

a hardstop that extends through the opening of the inner element of the flexure and is coupled to the extended portion of the rigid plate, wherein the inner element contacts the hardstop when a tensile component of an applied load exceeds a tensile threshold load, and wherein the extended portion of the inner element contacts the extended portion of the rigid plate when a compressive component of the applied load exceeds a compressive threshold load.

2. The device of claim 1 , further comprising an additional hardstop, wherein the additional hardstop extends through an additional opening of the inner element, wherein the additional hardstop is coupled to the rigid plate, and wherein each of the hardstops are symmetrically spaced out about a periphery of the inner element.

3. The device of claim 1 , wherein the hardstop comprises:
a cylindrical body portion that extends in a direction parallel to an axis of the rigid plate; and
a head portion comprising a lateral surface perpendicular and adjacent to the body portion and a vertical surface concentric with the body portion and extending in the direction parallel to the axis.

4. The device of claim 3 , wherein at least a portion of an internal surface of the opening of the inner element contacts at least one of the body portion or the vertical surface of the head portion of the hardstop when a lateral component of the load applied that is perpendicular to the axis exceeds a threshold lateral load.

5. The device of claim 3 , wherein at least a portion of an internal surface of the opening of the inner element contacts at least one of the body portion or the vertical surface of the head portion of the hardstop when a torque applied about the axis exceeds a threshold torque about the axis.

6. The device of claim 3 , wherein at least a portion of an internal surface of the opening of the inner element contacts at least one of the body portion, the lateral surface of the head portion, or the vertical surface of the head portion of the hardstop when a torque applied about a lateral axis perpendicular to the axis of the inner element exceeds a threshold torque about the lateral axis.

7. The device of claim 3 , wherein the extended portion of the rigid plate comprises a lateral surface perpendicular to the axis of the rigid plate, and wherein the inner element contacts either the lateral surface of the extended portion of the rigid plate or the lateral surface of the head portion of the hardstop when a vertical load applied in a direction parallel to the axis exceeds a threshold vertical load.

8. The device of claim 3 , wherein the body portion and the head portion of the hardstop are each at least partially encompassed by the inner element.

9. The device of claim 1 , further comprising:
a second rigid plate coaxial with the inner element; and
wherein the flexure further comprises a plurality of connecting elements coupled between the second rigid plate and the inner element, wherein the plurality of connecting elements are configured such that the second rigid plate and the inner element move together when a load is applied.

10. The device of claim 1 , further comprising a printed circuit board (PCB) coupled to the rigid plate, wherein the hardstop also extends through an opening of the PCB, and wherein the PCB comprises the sensor.

11. The device of claim 10 , wherein the extended portion of the rigid plate also extends through the opening of the PCB.

12. The device of claim 1 , wherein the hardstop is a clearance distance from the opening of the inner element when no load is applied to the device.

13. The device of claim 1 , wherein each of the plurality of connecting flexural elements is configured to deform in at least one of six degrees-of-freedom when a load is applied to the device.

14. A method, comprising:
receiving a load on a rigid plate coupled to a flexure, wherein the rigid plate comprises an extended portion extending towards the flexure, and wherein the flexure comprises an extended portion that extends towards the rigid plate and surrounds an opening of the flexure;
deforming at least one of a plurality of connecting flexural elements of the flexure when the load is received, wherein the plurality of connecting flexural elements is coupled to the rigid plate;
contacting, by a portion of the flexure, a hardstop when the load received exceeds a threshold load, wherein the hardstop extends through the opening of the flexure and is coupled to the extended portion of the rigid plate;
preventing, by the hardstop, further deformation of the at least one of the plurality of connecting flexural elements when the portion of the flexure contacts the hardstop;
contacting, by the extended portion of the flexure, the extended portion of the rigid plate when a compressive component of the load exceeds a compressive threshold load; and
preventing further deformation of the at least one of the plurality of connecting flexural elements when the extended portion of the flexure contacts the extended portion of the rigid plate.

15. The method of claim 14 , wherein contacting the hardstop comprises:
contacting, by an internal surface of an opening of the flexure, at least one of a cylindrical body portion of the hardstop, a cylindrical head portion of the hardstop, or a lateral surface of the hardstop, wherein the lateral surface is perpendicular to the cylindrical body portion, and further wherein the hardstop extends through the opening of the flexure.

16. The method of claim 14 , further comprising:
contacting, by a lateral surface of the flexure, a corresponding lateral surface of the rigid plate, wherein the lateral surface of the flexure is perpendicular to a cylindrical body portion of the hardstop.

17. The method of claim 14 , wherein the hardstop further extends through a printed circuit board (PCB) coupled to the rigid plate, the method further comprising:
emitting light, by a sensor coupled to the PCB, towards a plurality of reflective surface areas coupled to the flexure; and
detecting, by the sensor, the light reflected.

18. The method of claim 14 , further comprising:
contacting, by a second portion of the flexure, a head portion of the hardstop when a tensile component of the load exceeds a tensile threshold load;
preventing further deformation of the at least one of the plurality of connecting flexural elements when the second portion of the flexure contacts the head portion of the hardstop.

19. A robotic system comprising:
a rigid plate comprising an extended portion;
a flexure, comprising:
an inner element coupled to a plurality of reflective surface areas, wherein the plurality of reflective surface areas are configured t

Assignees

• X Dev Llc

Inventors

• Strauss Marc

Classifications

• G01L1/26 Primary

  Auxiliary measures taken, or devices used, in connection with the measurement of force, e.g. for preventing influence of transverse components of force, for preventing overload · CPC title

• G01L5/009

  Force sensors associated with material gripping devices · CPC title

• B25J9/1694

  characterised by use of sensors other than normal servo-feedback from position, speed or acceleration sensors, perception control, multi-sensor controlled systems, sensor fusion · CPC title

• G01L1/24

  by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis {using infrared, visible light, ultraviolet} · CPC title

• G01L5/166 Primary

  using photoelectric means · CPC title