Method of and apparatus for the elimination of the effects of internal interference in force measurement systems, including touch - input computer and related displays employing touch force location measurement techniques

• US 5,563,632 A
• Filed: 04/30/1993
• Issued: 10/08/1996
• Est. Priority Date: 04/30/1993
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company), Visage Incorporated
• Original Assignee: MicroTouch Systems, Inc. (3M Company)
• Inventors: Roberts, Jerry B.
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): LAO, LUNYI
• Application Number:
  US08/055,731
• Time in Patent Office: 1,257 Days
• Field of Search: 345/173, 345/174, 345/175, 345/177, 345/178, 345/156, 345/184, 345/104, 345/157, 345/160, 345/163, 345/168, 178/18, 178/19, 364/556, 364/566, 364/558, 341/22, 341/34, 73/65.01, 73/865.7, 73/117
• US Class Current: 345/173
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• 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: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment

Abstract

A method and apparatus is disclosed, particularly, though by no means exclusively, useful in touch--screen computer CRT display systems and the like, and more generally in other force and/or torque measurement systems, as in weighing and the like, in which (1) lineal and/or rotational acceleration of the system is sensed in response to inertial interference effects such as tilt or movement that introduce errors into the force and/or torque measurements, and/or (2) inertial error correction from the force data itself is obtained, such as derivative order corrections; and such data is used to correct the force and/or torque measurements. A novel calibration technique for deriving appropriately descriptive coefficients to the particular system for the correcting data, is also disclosed.

Claims

1. In a touch-input computer and related supported display employing touch force location measurements, a method of eliminating errors introduced into force and/or torque measurements by undesired inertial interference motions of one or more of the support, mechanical system of the display and/or force measuring apparatus itself, that comprises, sensing one or more components of force and/or torque applied to the display by touch forces to provide force and/or torque measurements uncorrected for inertial interference motion effects that arise;

sensing lineal and/or rotational acceleration of the display in response to such inertial interference motions; and

correcting the uncorrected force and/or torque measurements in response to the acceleration sensing to achieve substantial elimination from the measurements of the effects of such inertial interference.

2. A method as claimed in claim 1 and in which said uncorrected force measurements are made and said acceleration is sensed for all relevant degrees of freedom of motion in a plurality of respective channels, and different linear combinations of the acceleration-sensing channels are negatively added in turn to each channel of force measurement, with coefficients of combinations chosen such that the resulting sums reflect the desired force measurements substantially free of inertial motion interference errors.

3. A method as claimed in claim 2 and in which time derivatives including at least a set of the second order derivatives of the uncorrected force measurements are derived and entered in different linear combinations of each order in turn in each channel of force measurement further to correct the same.

4. A method as claimed in claim 3 and in which calibration is effected from the supported display by intentionally moving and disturbing the same in various ways while the touch force ultimately to be measured is allowed to remain at zero, in order to generate a correction matrix the elements of which comprise the desired coefficients of combination to achieve the corrections of the force measurements in each channel.

5. A method as claimed in claim 4 and in which coefficients of combination for the correcting channels are derived at the display.

6. A method as claimed in claim 1 and in which the lineal and/or rotational acceleration sensing in response to said inertial interference motions develops waveforms for use in said correcting, and wherein the correcting is effected by negatively combing the wave-forms with those in the force measurements to cancel out and thus correct for the said inertial motion interference errors.

7. In a touch-input computer and related supported display employing touch force location measurements, a method of eliminating errors introduced into force and/or torque measurements by undesired inertial interference motions of one or more of the support, mechanical systems of the display and/or force measuring apparatus itself, that comprises, sensing one or more components of force and/or torque applied to the display by touch forces to provide a plurality of channels of force and/or torque measurements uncorrected for inertial interference effects that arise;

deriving time derivatives including at least a set of the second order derivatives of the uncorrected force measurements and subtracting the same in different linear combinations of each order in turn from each channel of uncorrected force measurement, with coefficients of combination chosen such that the resulting sums reflect the desired force measurements substantially free of inertial motion interference errors.

8. In a touch-input computer and related supported display employing touch force location measurements, a method of eliminating errors introduced into force and/or torque measurements by undesired inertial interference motions of one or more of the support, mechanical systems of the display and/or force measuring apparatus itself, that comprises, sensing one or more components of force and/or torque applied to the display by touch forces to provide a plurality of channels of force and/or torque measurements uncorrected for inertial interference effects that arise;

intentionally moving and disturbing the supported display in various ways while the touch force ultimately to be measured is not applied and is allowed to remain at zero, in order to generate measurements that enable calibration of the supported display system that renders the same less prone to force measurement errors due to motions of the type created by said moving and disturbing.

9. A method of measuring force and/or torque to be applied to a touch panel display system, including, where desired, objects associated therewith and portions of force measuring apparatus itself, that comprises, sensing one or more components of force and/or torque applied to the system by forces acting thereupon to provide force and/or torque measurements uncorrected for inertial interference motion effects that arise;

sensing lineal and/or rotational acceleration of the system in response to such inertial interference motions; and

correcting the uncorrected force and/or torque measurements in response to the acceleration sensing to achieve elimination from the measurements of the effects of such inertial interference.

10. A method as claimed in claim 9 and in which said uncorrected force measurements are made and said acceleration is sensed for all relevant degrees of freedom of motion in a plurality of respective channels, and different linear combinations of the acceleration-sensing channels are negatively added in turn to each channel of force measurement, with coefficients of combinations chosen such that the resulting sums reflect the desired force measurements substantially free of inertial motion interference errors.

11. A method as claimed in claim 10 and in which time derivatives including at least a set of the second order derivatives of the uncorrected force measurements are derived and extended in different linear combinations of each order in turn in each channel of force measurement further to correct the same.

12. A method as claimed in claim 11 and in which calibration is effected from the supported display by intentionally moving and disturbing the same in various ways while the touch force ultimately to be measured is allowed to remain at zero, in order to generate a correction matrix the elements of which comprise the desired coefficients of combination to achieve the corrections of the force measurements in each channel.

13. A method as claimed in claim 12 and in which coefficients of combination for the correcting channels are derived at the display.

14. A method of measuring force and/or torque to be applied to a touch panel display system, including, where desired, objects associated therewith and portions of forces measuring apparatus itself, that comprises, sensing one or more components of force and/or torque applied to the system by deliberate forces acting thereupon to provide force and/or torque measurements uncorrected by inertial interference motion effects that arise:

deriving time derivatives including a least a set of the second order derivatives of the uncorrected force measurements and subtracting the same in different combinations of each order in turn from each channel of uncorrected force measurement, with coefficients of combination chosen such that the resulting sums reflect the desired force measurements substantially free of inertial motion interference errors.

15. A method of measuring force and/or torque to be applied to a touch panel display system, including, where desired, objects associated therewith and portions of force measuring apparatus itself, that comprises, sensing one or more components of force and/or torque applied to the system by deliberate forces acting thereupon to provide force and/or torque measurements uncorrected by inertial interference motion effects that may arise;

deriving time effects that arise;

intentionally moving and disturbing the system in various ways while said deliberate forces ultimately to be measured are not applied and are allowed to remain at zero, in order to generate measurements that enable calibration of the system that renders the same less prone to force measurement errors due to motions of the type created by said moving and disturbing.

16. In a touch-input computer and related supported display employing touch force location measurements, apparatus for eliminating errors introduced into force and/or to the measurements by undesired inertial interference motions of one or more of the support, mechanical system of the display and/or force measuring apparatus itself having, in combination, means for sensing one or more components of force and/or torque applied to the display by touch forces to provide force and/or torque measurements uncorrected for inertial interference motion effects that arise;

means for sensing lineal and/or rotational acceleration of the display in response to such inertial interference motions; and

means for correcting the uncorrected force and/or torque measurements in response to the acceleration sensing to achieve substantial elimination from the measurements of the effects of such inertial interference.

17. Apparatus as claimed in claim 16 and in which means is provided for making said uncorrected force measurements and sensing said acceleration for all relevant degrees of freedom of motion in a plurality of respective channels, and different linear combinations of the acceleration-sensing channels are subtracted in turn from each channel of force measurement, with coefficients of combinations chosen such that the resulting sums reflect the desired force measurements substantially free of inertial motion interference errors.

18. Apparatus as claimed in claim 17 and in which means is provided for deriving time derivatives including at least a set of the second order derivatives of the uncorrected force measurements and for entering the same in different linear combinations of each order in turn in each channel of force measurement further to correct the same.

19. Apparatus as claimed in claim 18 and in which calibration means is provided comprising means by intentionally moving and disturbing the supported display in various ways while the touch force ultimately to be measured is allowed to remain at zero, in order to generate a correction matrix the elements of which comprise the desired coefficients of combination to achieve the corrections of the force measurements in each channel.

20. A method as claimed in claim 19 and in which means for deriving coefficients of combination for the correcting channels is operated at the display.

21. In a touch-input computer and related supported display employing touch force location measurements, apparatus for eliminating errors introduced into force and/or torque measurements by undesired inertial interference motions of one or more of the support, mechanical systems of the display and/or force measuring apparatus itself, having, in combination, means for sensing one or more components of force and/or torque applied to the display by touch forces to provide a plurality of channels of force and/or torque measurements uncorrected for inertial interference effects that arise;

means for deriving time derivatives including at least a set of the second order derivatives of the uncorrected force measurements and subtracting the same in different linear combinations of each order in turn from each channel of uncorrected force measurement, with coefficients of combination chosen such that the resulting sums reflect the desired force measurements substantially free of inertial motion interference errors.

22. In a touch-input computer and related supported display employing touch force location measurements, apparatus for eliminating errors introduced into force and/or torque measurements by undesired inertial interference motions of one or more of the support, mechanical systems of the display and/or force measuring apparatus itself, having, in combination, means for sensing one or more components of force and/or torque applied to the display by touch forces to provide a plurality of channels of force and/or torque measurements uncorrected for inertial interference effects that may arise;

means for intentionally moving and disturbing the supported display in various ways while the touch force ultimately to be measured is not applied and is allowed to remain at zero, in order to generate measurements that enable calibration of the supported display system that renders the same less prone to force measurement errors due to motions of the type created by said moving and disturbing.

23. Apparatus for measuring force and/or torque to be applied to a touch panel display system, including, where desired, objects associated therewith and portions of force measuring apparatus itself, having, in combination, means for sensing one or more components of force and/or torque applied to the system by forces acting thereupon to provide force and/or torque measurements uncorrected for inertial interference motion effects that arise;

means for sensing lineal and/or rotational acceleration of the system in response to such inertial interference motions; and

means for correcting the uncorrected force and/or torque measurements in response to the acceleration sensing to achieve elimination from the measurements of the effects of such inertial interference.

24. Apparatus as claimed in claim 23 and in which said uncorrected force measurements are made and said acceleration is sensed for all relevant degrees of freedom of motion in a plurality of respective channels, and means is provided for negatively adding different linear combinations of the acceleration-sensing channels in turn to each channel of force measurement, with coefficients of combinations chosen such that the resulting sums reflect the desired force measurements substantially free of inertial motion interference errors.

25. Apparatus as claimed in claim 24 and in which means is provided to derive time derivatives including at least a set of the second order derivatives of the uncorrected force measurements and to enter the same in different linear combinations of each order in turn in each channel of force measurement further to correct the same.

26. Apparatus as claimed in claim 25 and in which calibration means is provided including means for intentionally moving and disturbing the same in various ways while the touch force ultimately to be measured is allowed to remain at zero, with means for generating a correction matrix the elements of which comprise the desired coefficients of combination to achieve the corrections of the force measurements in each channel.

27. Apparatus as claimed in claim 26 and in which means is provided for deriving the coefficients of combination for the correcting channels at the display.

28. In a computer input system providing measurements of the location at which a force is applied to a panel surface, a method of eliminating errors introduced into force and/or torque measurements by the desired inertial interference motions of one or more of the surface and/or force measuring apparatus itself, that comprises, sensing one or more components of force and/or torque applied to the surface by contact forces to provide force and/or torque measurements uncorrected for inertial interference motion effects that arise;

sensing lineal and/or rotational acceleration of the surface in response to such inertial interference motions; and

correcting the uncorrected force and/or torque measurements in response to the acceleration sensing to achieve substantial elimination from the measurements of the effects of such inertial interference.

29. A method as claimed in claim 28 and in which said surface comprises a supported touch-input panel surface to which forces are applied.

30. A method as claimed in claim 28 and in which said uncorrected force measurements are made and said acceleration is sensed for all relevant degrees of freedom of motion in a plurality of respective channels, and different linear combinations of the acceleration-sensing channels are subtracted in turn from each channel of force measurement, with coefficients of combinations chosen such that the resulting sums reflect the desired force measurements substantially free of inertial motion interference errors.

31. A method as claimed in claim 30 and in which time derivatives including at least a set of the second order derivatives of the uncorrected force measurements are derived and entered in different linear combinations of each order in turn in each channel of force measurement further to correct the same.

32. A method as claimed in claim 31 and in which calibration is effected by intentionally moving and disturbing the panel surface in various ways while the touch force ultimately to be measured is allowed to remain at zero, in order to generate a correction matrix the elements of which comprise the desired coefficients of combination to achieve the corrections of the force measurements in each channel.

33. A method of measuring force and/or torque to be applied to a supported touch-input system, including, where desired, objects associated therewith and portions of the force measuring apparatus itself that comprises, sensing one or more components of force and/or torque applied to the system by forces acting thereupon to provide force and/or torque measurements uncorrected by inertial interference motion effects that arise;

deriving time derivatives including at least in one instance, the second time derivative of some or all of the uncorrected force measurements or linear combinations thereof by subtracting such linear combinations of some or all from an uncorrected force measurement, to yield the desired force measurement substantially free of inertial motion interference errors.