Angle of rotation sensor

• US 20050030012A1
• Filed: 07/29/2004
• Published: 02/10/2005
• Est. Priority Date: 07/29/2003
• Status: Active Grant

• Current Assignee: MEGATRON Elektronik GmbH & Co. KG
• Original Assignee: TECH3 E. K.
• Inventors: Kunz-Vizenetz, Thomas
• Granted Patent: US 6,894,487 B2
• Time in Patent Office: Days
• US Class Current: 324/207.250
• CPC Class Codes: G01D 2205/22 by converting the rotary movement into a linear movement
• CPC Class Codes: G01D 2205/26 Details of encoders or position sensors specially adapted to detect rotation beyond a full turn of 360°, e.g. multi-rotation
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

An angle of rotation sensor includes a rotary shaft coupled to a permanent magnet. A magnet-sensitive sensor element generates a sinusoidal output signal and a cosinusoidal output signal (V_x, V_y) as a function of the relative angle of rotation (α) between magnet and sensor element. Evaluation electronics generate from the output signals a signal corresponding to the angle of rotation. When the shaft rotates about its axis it moves linearly parallel to its axis along a guide track, and changes the distance between the magnet and sensor. From the sensor signals, a signal (B(z)) is determined, which corresponds to the magnitude of the field strength dependent on the distance. From this signal, a gross signal is determined, from which the number (n) of rotations can be determined. From the sinusoidal and cosinusoidal sensor signals, a fine signal is determined, which is added to the number of rotations multiplied by 360°.

Claims

1. An angle of rotation sensor with a rotary shaft, a magnet coupled to the rotary shaft, and a magnetically sensitive sensor element, which generates a sinusoidal output signal and a cosinusoidal output signal as a function of the relative angle of rotation between the magnet and the sensor element, and with an evaluation unit, which generates from the output signals a signal corresponding to the angle of rotation, characterized in that the shaft is also moved linearly parallel to its axis along a guide track when the shaft rotates about its axis, so that the distance between magnet and sensor changes corresponding to a pitch of the guide track, and the evaluation unit determines from the generated sinusoidal and cosinusoidal output signals of the sensor element a signal, from which the distance between the sensor element and the magnet, and thus a number of full rotations of the shaft, can be determined, wherein from the generated sinusoidal and cosinusoidal output signals a fine signal within a full rotation is determined and this fine signal is added to the full rotation value multiplied by 360°

.

2. The angle of rotation sensor of claim 1 wherein the guide track comprises threads with constant pitch.

3. The angle of rotation sensor of claim 1 wherein the guide track is a sliding block guide, which is coupled by means of a tracing pin to the shaft.

4. The angle of rotation sensor of claim 3 wherein the guide track is continuous and monotonic, but not linear, and preferably follows a quadratic function F(z)=1/z².

5. The angle of rotation sensor of claim 4 wherein the fine signal is performed within a measurement range from 0°

to 360°

by a coordinate transformation according to a CORDIC algorithm.

6. The angle of rotation sensor of claim 5 wherein the evaluation unit has a memory, in which values of support points are stored, and for determining the number of rotations, it is determined which two successive values of support points surround the actual value of the measured field strength.

7. An apparatus for measuring an angle of rotation of a rotary shaft, said rotary shaft being rotatable about an axis of rotation and having a magnet coupled thereto, said apparatus comprising:

a magnetically sensitive sensor element for generating a sinusoidal output signal and a cosinusoidal output signal as a function of a relative angle of rotation between the magnet and the sensor element;

a guide track allowing movement of the shaft in a direction substantially parallel to the axis of rotation as the shaft rotates such that a distance between the magnet and the sensor element changes corresponding to a pitch of the guide track;

an evaluation unit for generating a signal B(z) as a function of the sinusoidal and cosinusoidal output signals generated by the sensor element, said signal B(z) being representative of the distance between the sensor element and the magnet and, thus, a number of full rotations of the shaft, said evaluation unit further generating a fine signal as a function of the sinusoidal and cosinusoidal output signals generated by the sensor element, said fine signal being representative of a partial rotation and is added to the number of full rotations multiplied by 360°

.

8. The apparatus of claim 7 wherein the guide track comprises threads having a substantially constant pitch.

9. The apparatus of claim 7 wherein the guide track is a sliding block guide coupled to the shaft by a tracing pin.

10. The apparatus of claim 9 wherein the guide track is substantially continuous and monotonic, but not linear.

11. The apparatus of claim 10 wherein the guide track follows a quadratic function F(z)=1/z² where z is the distance between the magnet and the sensor element.

12. The apparatus of claim 10 wherein the fine signal is performed within a measurement range from 0°

to 360°

by a coordinate transformation according to a CORDIC algorithm.

13. The apparatus of claim 12 wherein the evaluation unit has a memory storing support point values, said support point values corresponding to maximum amplitude values of the sinusoidal output signal for various angles of rotation, and wherein the evaluation unit determines the number of full rotations by determining which two successive values of support points surround the actual value of the signal B(z).

14. The apparatus of claim 7 wherein the magnetically sensitive sensor element comprises a first sensor for generating the sinusoidal output signal and a second sensor for generating the cosinusoidal output signal.

15. A method for measuring an angle of rotation of a rotary shaft, said rotary shaft being rotatable about an axis of rotation and having a magnet coupled thereto, said method comprising:

receiving a sinusoidal output signal and a cosinusoidal output signal from a magnetically sensitive sensor element, said sinusoidal and cosinusoidal output signals being representative of a relative angle of rotation between the magnet and the sensor element;

moving the shaft along a guide track in a direction substantially parallel to the axis of rotation as the shaft rotates such that a distance between the magnet and the sensor element changes corresponding to a pitch of the guide track;

determining a number of full rotations of the shaft as a function of the distance between the sensor element and the magnet;

determining an amount of partial rotation as a function of the sinusoidal and cosinusoidal output signals from the sensor element; and

adding the amount of partial rotation to the number of full rotations multiplied by 360°

to calculate the angle of rotation of the shaft.

16. The method of claim 15 wherein the guide block comprises a sliding block guide and further comprising coupling the sliding block guide to the shaft by a tracing pin.

17. The method of claim 15 wherein determining the amount of partial rotation comprises performing a coordinate transformation according to a CORDIC algorithm within a measurement range from 0°

to 360°

.

18. The method of claim 15 further comprising storing support point values corresponding to maximum amplitude values of the sinusoidal output signal for various angles of rotation, and wherein determining the number of full rotations comprises determining which two successive values of support points surround an actual value of a signal B(z).