ROTATIONAL ANGLE DETECTION DEVICE AND ELECTRIC POWER STEERING SYSTEM

• US 20110080160A1
• Filed: 09/29/2010
• Published: 04/07/2011
• Est. Priority Date: 10/06/2009
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Inventors: TOMITA, Akihiro
• Granted Patent: US 8,558,534 B2
• Time in Patent Office: Days
• US Class Current: 324/76.77
• CPC Class Codes: B62D 15/0245 Means or methods for determination of the central position of the steering system, e.g. straight ahead position
• CPC Class Codes: B62D 5/0484 for reaction to failures, e.g. limp home
• CPC Class Codes: B62D 5/049 detecting sensor failures
• CPC Class Codes: G01D 5/245 using a variable number of pulses in a train

Abstract

An ECU detects a steering angle that is an absolute angle based on a sine signal and a cosine signal that are output from a steering sensor. The ECU includes a three-phase pulse generator that generates, based on the sine signal and the cosine signal, three-phase pulse signals that have edges corresponding to predetermined rotational angles and that are set in such a manner that the predetermined rotational angles corresponding to the respective edges do not overlap each other and are at regular intervals. A microcomputer has a function as a second rotational angle detector that calculates a steering angle based on the pulse signals.

Claims

1. A rotational angle detection device, comprising:

a rotational angle sensor that outputs a sine signal and a cosine signal of which output levels are changed in accordance with a rotational angle of a detection target;

a first rotational angle detector that detects the rotational angle based on the sine signal and the cosine signal;

a pulse signal generator that generates, based on the sine signal and the cosine signal, three-phase pulse signals that have edges corresponding to predetermined rotational angles and that are set in such a manner that the predetermined rotational angles do not overlap each other and are at regular intervals; and

a second rotational angle detector that detects the rotational angle based on the pulse signals.

2. The rotational angle detection device according to claim 1, wherein

the pulse signal generator includes:

a voltage-dividing circuit which is formed by connecting four resistances, of which resistance values are equal to each other, in series, and to which a voltage that corresponds to a maximum value of the sine signal and the cosine signal is applied;

a first comparator that receives a high potential signal that is one of voltage-dividing signals output from the voltage-dividing circuit and the cosine signal;

a second comparator that receives a medium potential signal that is one of the voltage-dividing signals output from the voltage-dividing circuit and the sine signal; and

a third comparator that receives a low potential signal that is one of the voltage-dividing signals output from the voltage-dividing circuit and the cosine signal.

3. The rotational angle detection device according to claim 2, wherein the first rotational angle detector corrects an initial value of the rotational angle that is calculated when the first rotational angle detector restarts, using a second rotational angle that is continuously detected by the second rotational angle detector based on the pulse signals while the first rotational angle detector is stopped.

4. The rotational angle detection device according to claim 3, further comprising:

a starting unit that starts the second rotational angle detector when the edge is detected.

5. The rotational angle detection device according to claim 1, further comprising:

a first abnormality determination unit that determines whether the sine signal and the cosine signal that are received by the first rotational angle detector are abnormal; and

a second abnormality determination unit that determines whether the pulse signals that are received by the second rotational angle detector are abnormal.

6. An electric power steering system that detects a steering angle formed by a steering wheel using the rotational angle detection device according to claim 1.

7. An electric power steering system that detects a steering angle formed by a steering wheel using the rotational angle detection device according to claim 5, wherein:

a power assist control is executed using a first steering angle that is detected based on the sine signal and the cosine signal; and

when the sine signal and the cosine signal that are received by the first rotational angle detector are abnormal, if the pulse signals that are received by the second rotational angle detector are normal, the power assist control is continued using a second steering angle that is detected based on the pulse signals.

8. The rotational angle detection device according to claim 2, further comprising:

a first abnormality determination unit that determines whether the sine signal and the cosine signal that are received by the first rotational angle detector are abnormal; and

a second abnormality determination unit that determines whether the pulse signals that are received by the second rotational angle detector are abnormal.

9. The rotational angle detection device according to claim 3, further comprising:

a first abnormality determination unit that determines whether the sine signal and the cosine signal that are received by the first rotational angle detector are abnormal; and

a second abnormality determination unit that determines whether the pulse signals that are received by the second rotational angle detector are abnormal.

10. The rotational angle detection device according to claim 4, further comprising:

a first abnormality determination unit that determines whether the sine signal and the cosine signal that are received by the first rotational angle detector are abnormal; and

a second abnormality determination unit that determines whether the pulse signals that are received by the second rotational angle detector are abnormal.

11. An electric power steering system that detects a steering angle formed by a steering wheel using the rotational angle detection device according to claim 2.

12. An electric power steering system that detects a steering angle formed by a steering wheel using the rotational angle detection device according to claim 3.

13. An electric power steering system that detects a steering angle formed by a steering wheel using the rotational angle detection device according to claim 4.

14. An electric power steering system that detects a steering angle formed by a steering wheel using the rotational angle detection device according to claim 8, wherein:

a power assist control is executed using a first steering angle that is detected based on the sine signal and the cosine signal; and

when the sine signal and the cosine signal that are received by the first rotational angle detector are abnormal, if the pulse signals that are received by the second rotational angle detector are normal, the power assist control is continued using a second steering angle that is detected based on the pulse signals.

15. An electric power steering system that detects a steering angle formed by a steering wheel using the rotational angle detection device according to claim 9, wherein:

a power assist control is executed using a first steering angle that is detected based on the sine signal and the cosine signal; and

when the sine signal and the cosine signal that are received by the first rotational angle detector are abnormal, if the pulse signals that are received by the second rotational angle detector are normal, the power assist control is continued using a second steering angle that is detected based on the pulse signals.

16. An electric power steering system that detects a steering angle formed by a steering wheel using the rotational angle detection device according to claim 10, wherein:

a power assist control is executed using a first steering angle that is detected based on the sine signal and the cosine signal; and

when the sine signal and the cosine signal that are received by the first rotational angle detector are abnormal, if the pulse signals that are received by the second rotational angle detector are normal, the power assist control is continued using a second steering angle that is detected based on the pulse signals.