Apparatus for measuring position of ball joint

• US 5,712,478 A
• Filed: 04/18/1996
• Issued: 01/27/1998
• Est. Priority Date: 04/20/1995
• Status: Expired due to Fees

• Current Assignee: Swedish Conrtol System AB
• Original Assignee: Swedish Conrtol System AB
• Inventors: Olsson, Carl Johan
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US08/634,182
• Time in Patent Office: 649 Days
• Field of Search: 250/231.13, 250/231.16, 250/231.18, 250/221, 250/227.22, 73/510, 73/836, 73/843, 356/373, 356/375, 356/24-25
• US Class Current: 250/231.13
• CPC Class Codes: G01B 7/004 for measuring coordinates of points
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01D 5/2093 using polyphase currents
• CPC Class Codes: G01D 5/26 characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light

Abstract

A sensor for three dimensional detection of the position of a ball joint 1 in which two emitters 14-15 and two collectors 20-21 are located in the ball 4 and socket 5, respectively, of the ball joint 1, and at least one more emitter or collector is located in either the ball 4 or socket 5. Each of the emitters emits a unique signal characteristic and each of the collectors detects and decodes the signals from all emitters. By analyzing the influence of all the emitters on each of the collectors, the position of the ball joint can be deduced. The emitters can be coils or light emitting diodes that emit unique signal frequencies and the collectors can be coils or photo transistors which detects the ratio of signals from each of the emitters. Alternatively, a rotating magnetic field can be induced by three emitter coils in one of the joint halves and detected by three collector coils located in the other joint half.

Claims

1. Device for measuring three dimensional movement in a joint about three mutually orthogonal axes, where the joint comprises two joint halves which are moveable in relation to each other around the three orthogonal axis, with a common centre for each joint half, which device comprises:

at least two signal emitters located at a predetermined distance from each other in a first joint half;

at least two signal collectors located at a predetermined distance from each other in a second joint half;

at least one additional signal emitter or signal collector, the additional emitter being located at a predetermined distance from said at least two signal emitters and in the same joint half, the additional signal collector being located at a predetermined distance from said at least two signal collectors and in the same joint half;

a signal generating unit connected to each signal emitter for causing the signal emitters to emit signals having unique characteristics; and

a signal processing unit connected to each signal collector for detecting signals from the signal emitters.

2. Device according to claim 1, wherein the signal emitters are sources of light of different wavelengths and each signal collector comprises a number of sensors equal to the number of signal emitters, each sensor detecting light with the wavelength of one of the signal emitters.

3. Device according to claim 2, wherein the signal emitters are light emitting diodes which emits light of different wavelengths, and each of the signal collectors comprises a number of photo transistors equal in number to the number of signal emitters, each photo transistor being sensitive only to the wavelength of one of the signal emitters.

4. Device according to claim 1, wherein the signal emitters are transmitters of signals of unique frequencies and the signal collectors are receivers which receive the transmitted electrical signals from the transmitters.

5. Device according to claim 4, wherein each signal emitter is a coil, the signal generating unit includes a frequency generator connected to each coil for generating an electrical signal therein having a unique frequency, each signal collector is a coil, and the signal processing unit includes a bandpass filter unit connected to each collector coil which filters out from each collector coil respective signals having frequencies equal to the signal emitter frequencies.

6. Device according to claim 1, wherein the signal emitters are coils and the signal generating unit includes a generator that applies a sine wave shaped electrical signal to each signal emitter, the signal applied to each signal emitter having a phase skew in relation to the signal applied to the other signal emitters, the number of signal emitters in the first joint half being at least three and generating a rotating magnetic field and the number of signal collectors in the second joint half being at least three, which signal collectors each detects the phase skew of the rotating magnetic field at the location of each signal collector.

7. Device according to claim 1, wherein the joint is a ball joint having a ball in the first joint half and a socket in the second joint half, the ball and socket moving relative to each over respective sliding surfaces, the signal collectors are located on the surface of a first sphere with its centre coinciding with the centre of the ball joint, and the signal emitters are located on the surface of a second sphere with its centre coinciding with the centre of the ball joint.

8. Device according to claim 3, wherein the joint is a ball joint having a ball in the first joint half and a socket in the second joint half, the ball and socket moving relative to each over respective sliding surfaces, the signal collectors are located on the surface of a first sphere with its centre coinciding with the centre of the ball joint, and the signal emitters are located on the surface of a second sphere with its centre coinciding with the centre of the ball joint.

9. Device according to claim 5, wherein the joint is a ball joint having a ball in the first joint half and a socket in the second joint half, the ball and socket moving relative to each over respective sliding surfaces, the signal collectors are located on the surface of a first sphere with its centre coinciding with the centre of the ball joint, and the signal emitters are located on the surface of a second sphere with its centre coinciding with the centre of the ball joint.

10. Device according to claim 6, wherein the joint is a ball joint having a ball in the first joint half and a socket in the second joint half, the ball and socket moving relative to each over respective sliding surfaces, the signal collectors are located on the surface of a first sphere with its centre coinciding with the centre of the ball joint, and the signal emitters are located on the surface of a second sphere with its centre coinciding with the centre of the ball joint.

11. Device according to claim 7, characterized in that the first and second spheres coincide with the sliding surfaces of the ball joint.

12. Device according to claim 8, characterized in that the first and second spheres coincide with the sliding surfaces of the ball joint.

13. Device according to claim 9, characterized in that the first and second spheres coincide with the sliding surfaces of the ball joint.

14. Device according to claim 10, characterized in that the first and second spheres coincide with the sliding surfaces of the ball joint.

15. Device according to claim 1, further comprising a processor having a memory connected to the signal processing units, the processor making a comparison of the signal processing unit output data to a table in the memory which contains predetermined data on the relationship between signal processing unit output data and physical sensor positions, in order to establish the position of the joint.

16. Device according to claim 12, further comprising a processor having a memory connected to the signal processing units, the processor continuously making a comparison of signal processing unit output data to a table in the memory which contains predetermined data on the relationship between signal processing unit output data and physical sensor positions, in order to establish the position of the joint.

17. Device according to claim 13, further comprising a processor having a memory connected to the signal processing units, the processor making a comparison of signal processing unit output data to a table in the memory which contains predetermined data on the relationship between signal processing unit output data and physical sensor positions, in order to establish the position of the joint.

18. Device according to claim 14, further comprising a processor having a memory connected to the signal processing units, the processor making a comparison of signal processing unit output data to a table in the memory which contains predetermined data on the relationship between signal processing unit output data and physical sensor positions, in order to establish the position of the joint.