Angular position sensor and rotation control device

1. An angular position sensor comprising:

a sensor element for detecting changes of magnetic field strength of a magnet that rotates in synchronization with a rotating body whose angular position is to be detected; and

compensation means compensating hysteresis characteristics of an output of the sensor element in both a clockwise and a counterclockwise rotation of the rotation body;

wherein different coefficients, approximated by different functions are used for said compensation, when said rotation body rotates clockwise and counterclockwise.

2. An angular position sensor according to claim 1 , wherein said compensation means compensates said outputs of said sensor element with coefficients for compensation approximated by different polynomial functions.

3. An angular position sensor according to claim 1 , wherein said compensation means compensates said outputs of said sensor element with coefficients for compensation approximated by using different cubic functions.

4. An angular position sensor according to claim 1 , wherein:

said sensor element has outputs of two systems; and

said compensation means compensates said outputs of said sensor element with coefficients for compensation when said outputs of said two systems are divided and approximated using a polynomial function.

5. An angular position sensor according to claim 1 , wherein said compensation means compensates said outputs of said sensor element using approximated sensor outputs with the same functions and compensated values different for each rotational direction.

6. An angular position sensor comprising:

a motor for driving a rotation body;

a sensing element for detecting changes of magnetic field strength of a magnet that rotates in synchronization with said rotation body for detecting an angular position of said rotation body;

control means for controlling said motor so that a rotation angle of said rotation body detected by said sensor element becomes a desired angle; and

compensation means compensating hysteresis characteristics of an output of the sensor element in both a clockwise and a counterclockwise rotation of the rotation body;

wherein different coefficients, approximated by different functions, are used for said compensation when said body rotates clockwise and counterclockwise.

7. An angular position sensor according to claim 6 , wherein said compensation means compensates said outputs of said sensor element using coefficients for compensation approximated by using a linear function.

8. A position control device according to claim 6 , wherein said control means judges a rotational direction by a command value for motor drive for rotation of said rotation body.

9. A position control device according to claim 6 , wherein said control means judges a rotational direction by an output current of a motor driver circuit for driving rotation of said rotation body.

10. A position control device according to claim 6 , wherein said control means judges a rotational direction by an output voltage of a motor driver circuit for driving rotation of said rotation body.

11. A position control device according to claim 6 , wherein said control means judges a rotational direction by a change with time of an output signal of said sensor element.

12. An angular position sensor according to claim 6 , wherein said compensation means compensates said outputs of said sensor e element with coefficients for compensation approximated by using different cubic functions.

13. An angular position sensor according to claim 6 , wherein said compensation means compensates said outputs of said sensor element with coefficients for compensation approximated by using different nominal functions.

14. An angular position sensor according to claim 6 , wherein said compensation means compensates said outputs of said sensor element with coefficients for compensation approximated by using different linear functions.