Haptic input devices

• US 20040040805A1
• Filed: 05/19/2003
• Published: 03/04/2004
• Est. Priority Date: 10/27/2000
• Status: Active Grant

• Current Assignee: Makex Limited
• Original Assignee: Makex Limited
• Inventors: Bailey, Ralph-Peter Steven
• Granted Patent: US 7,499,021 B2
• Time in Patent Office: Days
• US Class Current: 188/267.2
• CPC Class Codes: G01B 5/008 using coordinate measuring machines
• CPC Class Codes: G06F 3/016 Input arrangements with force or tactile feedback as computer generated output to the user
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors

Abstract

A haptic input device comprises a hexapod or pentapod parallel linkage mechanism with force feedback effected by proportional control of magneto-restrictive fluid brakes constraining the measurement of the struts of the mechanism, through their base nodes. In the pentapod version of the haptic data input device, a haptic stylus is employed which includes an annular compliant feature that can be squeezed and whose squeeze pressure can be monitored.

Claims

1. A haptic device comprising a parallel link mechanism supporting a haptic stylus.

2. A haptic device as claimed in claim 1, which employs a parallel arrangement of struts to support the stylus and where force feedback is effected by proportional control of brakes constraining movement of the struts through their base nodes.

3. A haptic device as claimed in claim 1 or 2, wherein the parallel link mechanism comprises a hexapod having three base nodes, each accommodating two hemispherical parts with each hemisphere supporting one of the struts and allowing the struts to pass through it.

4. A haptic device as claimed in claim 3, wherein the hexapod is mounted with its base nodes beneath the stylus.

5. A haptic device as claimed in claim 3, wherein the hexapod is mounted with its base nodes to one side of the stylus such that the mechanism acts principally horizontally.

6. A haptic device as claimed in claim 1 or 2, comprising five struts arranged as a tripod and a “

V”

with the stylus acting between two common nodes defined one by the apex of the tripod and the other by the apex of the “

V”

.

7. A haptic device as claimed in claim 6, wherein one of the tripod struts acts as a rotational reference in the axis of the stylus enabling the degree of stylus rotation to be monitored.

8. A haptic device as claimed in any of claims 2 to 5 or in claim 6 or claim 7, as dependent on claim 2, where the brake is effected by causing MR fluid to change its viscosity by adjusting a magnetic field.

9. A haptic device as claimed in claim 8, wherein the MR fluid acts between the rim of a rotary disc and its housing, the disc axle extending out of a fluid filled cavity and retaining a friction wheel that acts capstan-like against the axial motion of a strut.

10. A haptic device as claimed in claim 8, where the MR fluid is in a cavity containing meshing gears and an electromagnet is arranged to create a magnetic field across the gear mesh zone that can be adjusted to adjust the viscosity of the fluid and in turn adjust the resistance to rotation of the gears.

11. A haptic device as claimed in any preceding claim, comprising a ball end around which two annular sockets attached to struts are clamped by virtue of a partial snap-on ring with opposite inwards faces, the gap between these faces being sufficient to accommodate the two annular socket rings back to back.

12. A haptic device as claimed in claim 11, where the ball end also accommodated a shirt strut able to pivot in one axis with respect to it, such accommodation occurring by virtue of a core being removed in the ball in the desired hinge axis and a barrel, attached to the strut being received therein, a slot in the ball enabling the strut to exit.

13. A haptic device as claimed in claim 12, wherein said third strut has a kink to enable it to achieve a smaller subtended angle with its adjacent neighbours but still sharing the notional common focal point.

14. A haptic device as claimed in claim 12 or 13, wherein a channel for wiring is cut into the barrel on the end of the strut and provides a path through the strut kink to connect with a hollow portion of the strut.

17. A stylus as claimed in claim 2, wherein the displaced fluid is channelled behind an axially located compliant feature such that it can act to expand such feature as fluid pressure is increased, and means to measure such axial expansion is provided.

18. A stylus as claimed in claim 17, wherein bellows displace a magnet along the axis of the stylus, and where the displacement is measured by a proportional Hall effect sensor.

22. A haptic device as claimed in any of claims 1 to 14, wheren the haptic stylus is as claimed in any of claims 15 to 21.

30. A haptic device as claimed in any of claims 1 to 14 and 22 arranged to operate according to a method as claimed in any one of claims 23 to 26, or a process as claimed in any of claims 27 to 29.

15. A stylus for a haptic device that includes an annular compliant feature that can be squeezed and whose squeeze pressure can be monitored.

16. A stylus as claimed in claim 15, wherein the annular compliant feature traps a fluid that will be displaced when the feature is squeezed.

19. A stylus for a haptic device that has an annular control button that can be operated from any degree of rotation by finger pressure moving it axially backwards and forwards.

20. A stylus as claimed in claim 19, where moving the annular button forward with respect to a neutral position is arranged to activate one switch state, and moving it backwards another.

21. A stylus as claimed in claim 20, where the movement of the annular button is sensed by non-contacting means.

23. A method of controlling a haptic device using proportional brakes to constrain motion such that control of the brake force vector can be used to guide the stylus toward a preferred CAD feature and then to retain it in position, or to slide it along a curve or surface.

24. A method as claimed in claim 23, where the determined brake vector when approaching a feature is a product of its sine component from the direct path and an exponential decay factor.

25. A method as claimed in claim 23 or 24, where the determined brake vector when wanting to be retained by a feature is a product of the cosine from the direct exit path and an exponential decay factor.

26. A method as claimed in claim 25, where the exponential decay factor establishes maximum brake force when the stylus is at the feature and reduces exponentially to zero at the desired maximum zone of influence.

27. A process where a discreet proportional control of the stylus of a haptic device is employed to establish the degree of the stylus'"'"'s resistance to motion, and where the user imposed force vector acting against this resistance is used to determine the relative movement of a CAD model or viewpoint.

28. A method as claimed in claim 27, where the force vector is determined from the product of the movement vector and the prevailing resistance level it is acting against.

29. A method as claimed in claim 27 or 28, where such discreet proportional control comprises a squeezable feature with transducer means to determine squeeze pressure.