FORCE MOMENT SENSOR

• US 20150204742A1
• Filed: 01/20/2015
• Published: 07/23/2015
• Est. Priority Date: 01/20/2014
• Status: Active Grant

• Current Assignee: Good Vibrations Engineering Ltd.
• Original Assignee: Good Vibrations Engineering Ltd.
• Inventors: DRAISEY, Sherry Lynn
• Granted Patent: US 9,513,179 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B25J 13/085 Force or torque sensors B25J13/082, B25J13/084 take precedence
• CPC Class Codes: G01L 1/005 by electrical means and not provided for in G01L1/06 - G01L1/22
• CPC Class Codes: G01L 3/1478 involving hinged levers
• CPC Class Codes: G01L 5/16 for measuring several components of force

Abstract

A force moment sensor for sensing forces and moments in a system through which forces and moments are transferred from an input member to an output member is disclosed. It includes a housing, an inner tube, a load plate, a plurality of elongate connectors and a plurality of dynamic deflection measuring devices. The housing has a base portion and an outer tube portion generally orthogonal to the base portion. The inner tube, a poled piezoceramic element, is operably connected to the base portion and spaced inwardly of the outer tube. The load plate is attached to the inner tube, spaced from the base portion and spaced from the outer tube. The plurality of elongate connectors are connected between the load plate and the outer tube portion. The plurality of dynamic deflection measuring devices are attached to the load plate for measuring dynamic flexible deflections of the load plate.

Claims

1. A force moment sensor for sensing forces and moments that are transferred from an input member to an output member, the force moment sensor comprising:

a housing having a base portion and outer tube portion extending from the base portion and one of the input member and the output member is attachable to the base portion;

an inner tube operably connected to the base portion of the housing, spaced inwardly of the outer tube, the inner tube being a poled piezoceramic element;

a load plate attached to the inner tube, spaced from the base portion of the housing and spaced from the outer tube and having a circumference and a centre axis, the other of the input member and the output member is attachable to the load plate;

a plurality of elongate connectors connected between the load plate and the outer tube portion around the circumference of the load plate, each elongate connector defining a longitudinal axis and the longitudinal axes of the plurality of the elongate connectors intersect the centre axis of the load plate when an undeflected configuration; and

a plurality of dynamic deflection measuring devices attached to the load plate for measuring dynamic flexible deflections of the load plate.

2. The force moment sensor of claim 1 wherein outer tube portion extends generally orthogonally from the base portion.

3. The force moment sensor of claim 1 wherein the inner tube includes a plurality of segments and each segment is independently responsive to current.

4. The force moment sensor of claim 3 wherein there is at least four segments.

5. The force moment sensor of claim 3 wherein each segment is poled in an axis parallel to the centre axis.

6. The force moment sensor of claim 3 wherein each segment is poled in an axis angled to the centre axis.

7. The force moment sensor of claim 3 wherein at least one segment is poled in an axis parallel to the center axis and at least another segment is poled in an axis angled to the centre axis.

8. The force moment sensor of claim 1 wherein each elongate connector is a pin ended strut.

9. The force moment sensor of claim 1 wherein each elongate connector is a cable.

10. The force moment sensor of claim 1 further including a plurality of thermal straps extending between the load plate and the outer tube portion of the housing.

11. The force moment sensor of claim 10 wherein each of the plurality of thermal straps are positioned proximate to each of the plurality of elongate connectors.

12. The force moment sensor of claim 1 wherein each dynamic measuring device is an accelerometer.

13. A computer implemented method of determining a force and moment of an external load applied to a force moment sensor having an inner tube and a load plate, the method comprising the steps of:

applying a current to the inner tube through a definable range of frequencies;

extracting a resonant frequency and associated dynamic shape of the load plate over the range of frequencies;

comparing the extracted resonant frequency and associated dynamic shape to a plurality of calibration shapes; and

determining the external load.

14. The computer implemented method of claim 13 wherein the extracting step includes measuring acceleration of a plurality of locations on the loading plate and calculating the frequency and the dynamic shape of the load plate.

15. The computer implemented method of claim 14 wherein the calculating step is done using fast fourier transform.

16. A system for sensing forces and moments comprising:

an input member;

an output member;

a force moment sensor having a housing, an inner tube including a poled piezoceramic element, a load plate attached to the inner tube and spaced from the housing and a plurality of elongate connectors connected between the load plate and the housing and a plurality of dynamic deflection measuring devices and the housing being connected to one of the input member and the output member and the load plate being connected to the other of the input member and the output member;

a processing means for determining the external load applied to the force moment sensor.