JP2014189115A - Steering angle detection device - Google Patents

Abstract

In a power steering apparatus, a highly accurate absolute steering angle is detected and the cost is reduced.
In an initial steering angle setting circuit, a detection value of a steering angle sensor AS is set as an initial value when an ignition switch or an accessory switch is turned on, or an initial value is set to 0 when it is determined that the vehicle is in a straight traveling state. Set as. The absolute rudder angle change amount calculation circuit 12 calculates the absolute rudder angle change amount estimated from the output signal of the motor rotation angle sensor 8. Then, the absolute steering angle calculation circuit 13 adds the amount of change in the absolute steering angle to the initial value, and calculates the absolute steering angle, which is the amount of change from the neutral position of the steering wheel SW.
[Selection] Figure 2

Description

  The present invention relates to a power steering device for a vehicle, and more particularly to a steering angle detection device for a power steering device.

  In recent years, in order to respond to needs such as improvement in steering feeling, high output, and high efficiency of vehicles, those that perform various types of vehicle control using high-precision steering angle sensors and motor rotation angle sensors are increasing.

  The following Patent Document 1 is disclosed as a steering angle sensor of a steering device.

JP 2009-192456 A

  The motor rotation angle sensor has a high detection accuracy for controlling the electric motor, but detects a relative steering angle, and cannot detect an absolute steering angle alone. Therefore, it is necessary to use a highly accurate rudder angle sensor for the purpose of detecting a highly accurate absolute rudder angle. However, when a highly accurate rudder angle sensor and motor rotation angle sensor are used, there is a problem that the cost is increased.

  The present invention has been devised in view of such technical problems, and it is an object of the present invention to detect a highly accurate absolute steering angle and reduce costs in a power steering device.

  The present invention sets the detected value of the rudder angle sensor as an initial value when the ignition switch or accessory switch is turned on, or sets the initial value as 0 when it is determined that the vehicle is traveling straight, and the motor rotation angle sensor A change amount of the absolute steering angle estimated from the output signal is added to the initial value to calculate an absolute steering angle that is a change amount from the neutral position of the steering wheel.

  According to the present invention, in a power steering device, it is possible to detect a highly accurate absolute steering angle and to suppress an increase in cost.

1 is a schematic diagram showing a power steering device in Embodiment 1. FIG. It is a block diagram which shows the steering angle detection apparatus in Embodiment 1. FIG. 3 is a graph showing each signal in the first embodiment. It is a graph which shows the output signal of a motor rotation angle sensor. It is a graph which shows the resolution of a rudder angle sensor, and the output signal of a motor rotation angle sensor. 10 is a graph showing each signal in the second embodiment. It is explanatory drawing of Embodiment 4. FIG.

  Embodiments 1 to 4 of the steering angle detection device for a power steering device according to the present invention will be described below in detail with reference to FIGS.

[Embodiment 1]
FIG. 1 is a schematic diagram illustrating a power steering apparatus according to the first embodiment. In the power steering apparatus shown in FIG. 1, a basic steering mechanism is configured by the steering wheel SW, the steering shaft 1, the pinion shaft 5, and the rack shaft 6. In this steering mechanism, when the steering wheel SW is rotated by the driver, the steering torque of the steering wheel SW is transmitted to the pinion shaft 5 via the steering shaft 1, and the rotational motion of the pinion shaft 5 is transmitted to the rack shaft. The left and right steered wheels (not shown) that are converted into the linear motion 6 and coupled to both ends of the rack shaft 6 are steered. That is, the rack shaft 6 is formed with rack teeth that mesh with the pinion shaft 5, and a conversion mechanism that converts the rotation of the steering shaft 1 into a turning operation by meshing the rack teeth with the pinion shaft is configured. .

The housing of the pinion shaft 5 is provided with a torque sensor TS (for example, a resolver) for detecting the steering angle of the steering wheel SW. The output signal of the torque sensor TS and the motor rotation angle provided in the electric motor M are provided. Based on the output signal of the sensor (for example, resolver, IC, etc.) 8 and vehicle speed information, current control of the electric motor M is performed by a control device (not shown: hereinafter referred to as ECU), and the electric motor M passes through the speed reducer 7. A steering assist force is applied to the rack shaft 6.

  The steering shaft 1 is divided in the axial direction into an input shaft 2 on the steering wheel SW side and an output shaft 3 on the rack shaft 6 side. The input shaft 2 and the output shaft 3 are each formed in a hollow shape, and are coaxially connected to each other via a torsion bar 4 provided on the inner peripheral side of the input shaft 2 and the output shaft 3. As a result, the input shaft 2 and the output shaft 3 can rotate relative to each other with torsional deformation of the torsion bar 4. The torsion bar 4 is provided with a steering angle sensor AS (for example, an MR element or an IC).

  Next, a method for calculating the absolute steering angle in the first embodiment will be described. The motor rotation angle sensor 8 detects a relative steering angle and cannot detect an absolute steering angle alone. Therefore, the absolute steering angle detected by the steering angle sensor AS when the ignition switch or the accessory switch is turned on is used as an initial value. Hereinafter, it demonstrates in detail based on FIG.

  FIG. 2 is a block diagram illustrating the steering angle detection device according to the first embodiment. As shown in FIG. 2, the steering angle detection device 10 is provided in the ECU, and initially sets the absolute steering angle detected by the steering angle sensor AS when the vehicle ignition switch or accessory switch is turned on as an initial value. A rudder angle setting circuit 11, an absolute rudder angle change amount calculating circuit 12 for calculating a change amount of the absolute rudder angle based on the output signal of the motor rotation angle sensor 8 and the reduction ratio of the speed reducer 7, and the initial rudder angle setting circuit. 11 based on the initial value set at 11 and the amount of change in the absolute steering angle calculated by the absolute steering angle change amount calculation circuit 12. And an angle calculation circuit 13.

  FIG. 3 is a waveform diagram showing each signal in the first embodiment. As shown in FIG. 3, when the ignition switch or accessory switch is turned on, the absolute steering angle detected by the steering angle sensor AS is set as an initial value in the initial steering angle setting circuit 11, and this initial value is retained. Is done.

  When the ignition switch or accessory switch is turned on, the absolute rudder angle change calculation circuit 12 corrects the relative rudder angle estimated from the output signal of the motor rotation angle sensor 8 to 0 point, and the relative rudder detected after that is corrected. The angle is detected (calculated) as a change amount of the absolute rudder angle.

  As shown in FIG. 4, the detection range of the motor rotation angle sensor 8 is 360 °, and when it rotates 360 °, the output of the motor rotation angle sensor 8 returns to zero. For this reason, when the motor shaft changes beyond the detection range (360 °), it is determined whether the motor shaft has changed within the detection range 360 ° (± 180 °) and is further rotated N times from there. I can't. Therefore, the number of rotations of the motor shaft in the clockwise direction or the counterclockwise direction is counted as the rotation number information N. As a result, the motor rotation angle sensor 8 can detect a change amount of the absolute steering angle of 360 ° or more.

  Thus, the absolute steering angle detected by the steering angle sensor AS when the ignition switch or the accessory switch is turned on is set as an initial value, and the absolute steering angle estimated from the output signal of the motor rotation angle sensor 8 is set to the initial value. By adding the amount of change (relative rudder angle), it is possible to detect the absolute rudder angle that is the steering angle from the neutral state of the steering wheel SW.

  FIG. 5 is a graph showing the amount of change in the absolute steering angle estimated from the resolution of the steering angle sensor AS and the output signal of the motor rotation angle sensor 8. As shown in FIG. 5, the rudder angle sensor AS used in the first embodiment does not have high resolution. On the other hand, the motor rotation angle sensor 8 has high detection accuracy for controlling the electric motor M, and the amount of change in the absolute steering angle estimated from the output signal of the motor rotation angle sensor 8 has high resolution. Therefore, a highly accurate absolute steering angle can be obtained by adding the amount of change in the absolute steering angle estimated from the output signal of the motor rotation angle sensor 8 to the absolute steering angle detected by the steering angle sensor AS. . As a result, it is possible to reduce the cost by using only the motor angle sensor 8 of high accuracy among the rudder angle sensor and motor angle sensor that have become highly accurate in recent years, and using the rudder angle sensor AS having low accuracy. It becomes possible.

  Further, the output of the rudder angle sensor AS has a swell component due to the structure of the rudder angle sensor AS, but by adding the change amount of the absolute rudder angle estimated from the output signal of the motor rotation angle sensor AS, the rudder angle sensor It is possible to suppress the influence of the swell component of the AS output and increase the detection accuracy.

  Furthermore, since the absolute rudder angle of the rudder angle sensor AS is used as an initial value, it is possible to output a normal absolute rudder angle even when the rotation speed information N has a count error.

  Further, since the output signal of the steering angle sensor AS is an initial value, and the amount of change in the absolute steering angle estimated from the output signal of the motor rotation angle sensor 8 is added to the initial value, the system configuration is simplified. .

[Embodiment 2]
Next, the steering angle detection device according to the second embodiment will be described. The steering angle detection device according to the second embodiment takes into account the torsion angle of the torsion bar 4. Since other configurations are the same as those of the first embodiment, description thereof is omitted here.

  That is, in the first embodiment, only the change amount (relative steering angle) of the absolute steering angle detected by the motor rotation angle sensor 8 is added to the initial value (absolute steering angle) detected by the steering angle sensor AS. In the second embodiment, as shown in FIG. 6, the twist angle of the torsion bar 4 based on the torque value that is the output signal of the torque sensor TS is further added, as shown in FIG. The absolute rudder angle is calculated.

  As a result, the absolute rudder angle detected in the second embodiment is a value that also takes into account the torsion of the torsion bar 4, and a value with higher accuracy than that obtained in the first embodiment is obtained. be able to.

  The torque value may be a torque value used for control instead of an output signal of the torque sensor TS. Thereby, the torque sensor TS can be omitted and the apparatus can be simplified.

[Embodiment 3]
Next, the steering angle detection device according to the third embodiment will be described. The steering angle detection device according to the third embodiment takes into account an angular error due to a backlash of a ball screw or a steering mechanism (pinion shaft 5, rack shaft 5) in the speed reducer 7. Since other configurations are the same as those of the first embodiment, description thereof is omitted here.

  That is, in the first embodiment, only the change amount (relative steering angle) of the absolute steering angle estimated from the output signal of the motor rotation angle sensor 8 with respect to the initial value (absolute steering angle) detected by the steering angle sensor AS. In the third embodiment, the absolute steering angle is calculated by further adding the angle error due to the backlash.

  The angle error due to the backlash can be estimated from the output delay of the torque sensor TS or the steering angle sensor AS with respect to the output value of the motor rotation angle sensor 8, and a method of setting it as a fixed value in advance can be considered.

  And the absolute steering angle which added the variation | change_quantity (relative steering angle) of the absolute steering angle estimated from the output signal of the motor rotation angle sensor 8 with respect to the initial value (absolute steering angle) detected by the steering angle sensor AS. On the other hand, an absolute steering angle with higher accuracy can be obtained by further adding the angle error due to the backlash.

  Furthermore, in addition to the absolute steering angle (initial value) detected by the steering angle sensor AS, the amount of change in the absolute steering angle (relative steering angle) estimated from the output signal of the motor rotation angle sensor 8, the angle error due to the backlash, etc. In addition, by adding the torsion angle of the torsion bar 4 shown in the second embodiment to calculate the absolute steering angle, the accuracy of the absolute steering angle is further improved.

[Embodiment 4]
Next, a steering angle detection device according to the fourth embodiment will be described. The steering angle detection device according to the fourth embodiment omits the steering angle sensor AS.

  In the first to third embodiments, the absolute steering angle detected by the steering angle sensor AS when the ignition switch or the accessory switch is turned on is set as an initial value. However, in the fourth embodiment, the initial steering angle setting circuit 11 is set. The initial value is set to 0 when it is determined that the vehicle is traveling straight.

  Information for determining whether or not the vehicle is traveling straight (hereinafter referred to as straight traveling determination information) includes vehicle speed, yaw rate value, lateral acceleration, left and right wheel rotational speed difference of steered wheels, car navigation system map Information, course information of the in-vehicle camera, and the like.

  When the vehicle speed is high, it can be estimated that the vehicle is traveling straight. Therefore, when the vehicle speed detected by the speed sensor mounted on the vehicle is larger than a preset threshold value, it can be determined that the vehicle is traveling straight.

  Further, when the yaw rate value, the lateral acceleration, and the left and right wheel rotational speed differences of the steered wheels are extremely small, it can be determined that the vehicle is traveling straight.

  Since the curvature information of the course can be obtained from the map information of the car navigation or the course information of the vehicle-mounted camera, it is possible to estimate whether or not the vehicle is in a straight traveling state from the curvature information.

  As shown in FIG. 7, when it is determined that the vehicle is in the straight traveling state based on the straight traveling determination information, the initial value of the absolute steering angle is set to 0 degree, and the output signal of the motor rotation angle sensor 8 is set with respect to this initial value (0). The absolute steering angle can be calculated by adding the amount of change in the absolute steering angle estimated from the above.

  As a result, the absolute steering angle of the steering wheel SW can be obtained without providing the steering angle sensor AS that can detect the absolute steering angle independently.

  Further, since the resolution of the motor rotation angle sensor 8 is higher than the resolution of the steering angle sensor AS, a high-precision absolute steering angle can be obtained by calculating the absolute steering angle using the output signal of the motor rotation angle sensor 8. Can do.

  Further, if the twist angle of the torsion bar 4 shown in the second and third embodiments and the angle error due to the backlash are added, the accuracy of the absolute steering angle can be further improved.

  Here, it is the technical idea grasped | ascertained from each embodiment mentioned above, Comprising: The thing with the effect is described below except what was described in the claim.

  (A) The steering angle detection device according to claim 1, wherein the absolute value when the steering wheel changes according to the steering operation of the steering wheel based on the initial value, the amount of change in the absolute steering angle, and the torsion angle of the torsion bar. The steering angle is calculated.

  According to the technical idea described in (a), it is possible to take into account the twist of the torsion bar and to obtain a more accurate absolute steering angle.

  (B) The steering angle detecting device according to (a), wherein the torsion angle of the torsion bar is estimated from a torque value used for control.

  According to the technical idea described in (b), since the torsion angle of the torsion bar is always estimated using the torque value used for the control without obtaining the angle signal information of the torque sensor separately, the system can be simplified. Can be planned.

  (C) The rudder angle detection device according to claim 1, wherein the steering angle is detected according to the steering wheel steering operation based on the initial value, the amount of change in the absolute rudder angle, and the angle error due to backlash in the steering mechanism or the speed reducer. And calculating the absolute steering angle when changing.

  According to the technical idea described in (c), an angle error due to backlash in the steering mechanism or the speed reducer can be taken into consideration, and a more accurate absolute steering angle can be obtained.

  (D) The rudder angle detection device according to claim 1, wherein the absolute rudder angle change calculation circuit counts how many times the motor shaft has rotated clockwise or counterclockwise as rotation information. It is characterized by.

  According to the technical idea described in (d), it is possible to detect a range of 360 ° or more as the amount of change in the absolute steering angle.

SW ... steering wheel AS ... rudder angle sensor M ... electric motor 7 ... speed reducer 8 ... motor rotation angle sensor 10 ... absolute rudder angle detector 11 ... initial rudder angle setting circuit 12 ... absolute rudder angle change calculation circuit 13 ... absolute rudder Angle calculation circuit

Claims (2)

A steering mechanism that transmits the steering operation of the steering wheel to the steered wheels;
An electric motor that includes a rotor, a stator, and a motor rotation angle sensor that detects a rotational position of the rotor, and applies a steering force to the steering mechanism via a reduction gear;
A steering angle detection device for detecting an absolute steering angle which is a rotation amount from a neutral state of a steering wheel of a power steering device comprising:
A steering angle sensor provided in the steering mechanism for detecting the absolute steering angle;
An absolute steering angle change amount calculation circuit for calculating a change amount of the absolute steering angle based on an output signal of the motor rotation angle sensor and a reduction ratio of the speed reducer;
An initial steering angle setting circuit that sets an absolute steering angle detected by the steering angle sensor as an initial value when an ignition switch or an accessory switch of the vehicle is turned on;
Based on the initial value and the amount of change in the absolute steering angle, an absolute steering angle calculation circuit that calculates the absolute steering angle when changing according to a steering operation of a steering wheel;
A rudder angle detection device comprising: A steering mechanism that transmits the steering operation of the steering wheel to the steered wheels;
An electric motor that includes a rotor, a stator, and a motor rotation angle sensor that detects a rotational position of the rotor, and applies a steering force to the steering mechanism via a reduction gear;
A steering angle detection device for detecting an absolute steering angle which is a rotation amount from a neutral state of a steering wheel of a power steering device comprising:
An absolute steering angle change amount calculation circuit for calculating a change amount of the absolute steering angle based on an output signal of the motor rotation angle sensor and a reduction ratio of the speed reducer;
The vehicle is in a straight traveling state based on at least one of vehicle speed, yaw rate value, lateral acceleration, difference between the left and right wheel rotational speeds of the steered wheels, map information of the car navigation system or course curvature information based on the course information of the in-vehicle camera. An initial rudder angle setting circuit that sets an initial value of the absolute rudder angle to 0 degrees when it is determined whether or not the vehicle is in a straight traveling state;
An absolute steering angle calculation circuit that calculates the absolute steering angle when changing according to the steering operation of the steering wheel based on the initial value set to 0 degrees and the amount of change in the absolute steering angle;
A rudder angle detection device comprising:

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