Method of detecting absolute steering angle of steering angle sensor for vehicle

• US 5,065,324 A
• Filed: 03/16/1990
• Issued: 11/12/1991
• Est. Priority Date: 03/22/1989
• Status: Expired due to Fees

• Current Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Original Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Inventors: Takahashi, Tsutomu, Mouri, Toyohiko, Oshita, Saiichiro
• Primary Examiner(s): Cangialosi, Salvatore
• Application Number:
  US07/494,541
• Time in Patent Office: 606 Days
• Field of Search: 364/424.05, 364/559, 364/571.01, 364/571.04, 180/140-143, 180/79.1, 33/1 PT
• US Class Current: 701/41
• CPC Class Codes: B62D 15/02 Steering position indicators ; Steering position determination; Steering aids
• CPC Class Codes: G01D 5/36 Forming the light into pulses

Abstract

A method for detecting an absolute steering angle of a steering angle sensor such as encoder for a vehicle wherein the steering angle sensor generates an output signal indicating a relative rotation angle of a steering shaft of the vehicle and at least one reference signal representing a reference position for every one rotation of the steering shaft. The method comprises the steps of setting a deviation Δθ between the reference position and an actual straight-ahead driving state position responsive to the output signal and the reference signal, storing the deviation Δθ in a memory of a computer which holds the deviation Δθ while the computer is disconnected from a battery, determining a steering angle with the reference position responsive to the output signal and the reference signal, and correcting by the deviation Δθ the steering angle to obtain the absolute steering angle.

Claims

1. A method for detecting an absolute steering angle of a steering angle sensor mounted on a vehicle wherein said steering angle sensor generates an angle signal indicating a relative rotation angle of a steering shaft of said vehicle and a reference signal representing a reference position for every one rotation of said steering shaft, comprising:

detecting after completing the installation of said steering angle sensor on said vehicle, a deviation of angle between said reference signal and said angle signal generated at the time when said steering shaft is in an actual straight-ahead driving position, said deviation being stored in a memory of a computer, which memory retainer said deviation even though said computer is disconnected from a power supply;

determining a steering angle away from said reference position in response to said angle signal and said reference signal while the vehicle runs; and

correcting said steering angle with said deviation, thereby accurately obtaining an absolute steering angle regardless of any error in installing said steering angle sensor during the assembling of the vehicle.

2. The method according to claim 1, wherein said detecting step comprises the steps of:

adjusting said steering shaft in the actual straight-ahead driving position;

inputting said angle signal output from said steering angle sensor while said steering shaft is in said actual straight-ahead driving position;

rotating said steering shaft alternatively to both rotational direction;

inputting said reference signal from said steering angle sensor while said steering shaft is rotated in said rotating step;

calculating said deviation of angle between said reference signal and said angle signal input in said inputting step; and

storing said deviation in said memory.

3. The method according to claim 2, further comprising:

turning on a manual switch to generate a switch signal after said adjusting step, whereby said angle signal at the straight-ahead driving position is detected in said detecting step responsive to said switch signal.

4. The method according to claim 10, wherein said deciding step comprises:

reconnecting said computer to said battery which have been disconnected from each other;

turning said steering shaft from one rotation limit to the other rotation limit of said steering shaft;

detecting a plurality of reference signals output from said steering angle sensor during said turning step; and

determining a median occurrence reference signal among said plurality of reference signals as an actual reference signal corresponding to said straight-ahead driving position, thereby resetting said reference position.

5. The method according to claim 1, wherein

said steering angle sensor is an optical rotary encoder comprising a slitted disk fixed coaxially to the steering shaft and provided with a reference position mark thereon, and a photointerruptor fixedly mounted on a steering column of the vehicle opposite to the slitted disk.

6. The method according to claim 1, wherein

said steering angle sensor is a magnetic rotary encoder which generates a sinusoidal-wave output signal in accordance with the rotation of the steering shaft.

7. The method according to claim 1, wherein

said steering angle sensor is a rotary encoder which generates a saw-tooth output signal in accordance with the rotation of the steering shaft.

8. The method according to claim 1, wherein

said memory is a non-volatile memory.

9. The method according to claim 1, wherein

said memory is a memory with a backup power supply.

10. The method according to claim 1, further comprises the step of:

deciding the reference position after the computer is reconnected to the battery by selecting a median reference signal from a plurality of reference signals detected by the steering angle sensor while steering from one limit to the other limit.

11. A method for detecting an absolute steering angle of a steering angle sensor mounted on a vehicle wherein said steering angle sensor transmits to a computer an angle signal indicating a relative rotation angle of a steering shaft of said vehicle and a reference signal representing a reference position for every one rotation of said steering shaft and said computer includes a memory retaining a deviation angle of said reference position from an actual straight-ahead driving position of said steering shaft even though said computer is disconnected from a battery, comprising:

reconnecting said computer to said battery which have been disconnected from each other once;

turning said steering shaft from one rotation limit to the other rotation limit of said steering shaft;

detecting a plurality of reference signals output from said steering angle sensor during said turning step;

determining a median occurrence reference signal among said plurality of reference signals as an actual reference signal corresponding to said straight-ahead driving position, thereby identifying said reference position after said reference position is erased from said memory due to disconnecting said battery from said computer;

determining a steering angle away from identified reference position in response to said angle signal and said reference signal representing said identified reference position while the vehicle runs; and

correcting said steering angle with said deviation, thereby accurately obtaining an obsolute steering angle regardless of any error in installation of said steering angle sensor in assembling the vehicle.