JP2003118620A - Electric power steering control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering control device capable of affording the rotation angle of a steering shaft with high resolution and high accuracy without requiring accuracy for a setting position in the incorporating process of a neutral point sensor. SOLUTION: A calculation means for the rotation angle of the steering shaft is adopted as follows. A count value by a counter means is reset according to the detection result of a neutral point detection means, and an estimated reaction value of the steering shaft is calculated based on a steering torque and a current signal flowing into a motor. When the absolute value of the reaction value of the shaft is in a range where a vehicle is recognized to be in a straight-ahead travel condition, the count value after the reset by the counter means is stored according to the rotation direction of the motor, which is averaged to calculate a neutral point correction value. Thus, the rotation angle of the steering shaft is calculated based on the neutral point correction value and the count value by the counter means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering control device, and more particularly to an electric power steering control device that calculates a steering angle using a motor angle sensor.

[0002]

2. Description of the Related Art FIG. 16 shows, for example, Japanese Patent Laid-Open No. 2000-20.
Japanese Patent No. 3443 "Electric Power Steering System"
5 is a configuration diagram showing a conventional electric power steering control device described in FIG. In FIG. 16, a steering shaft 1 is connected to a steering wheel 2 and rotates according to an operation of the steering wheel 2 by a driver. The rotation operation of the steering shaft 1 is transmitted to the wheels 3 and 4 via a rack and pinion gear 5.

The steering torque sensor 6 measures the steering torque value generated by the driver operating the steering wheel 2. The measured steering torque value controls the current supplied to the motor 8 (shown in the figure). Not performed by the assist torque control means). The motor 8 is connected to the steering shaft 1 via a motor reduction gear 7 having a gear ratio of, for example, 16.5: 1, and serves to give torque assistance to the steering shaft 1.

The motor 8 is a three-phase permanent magnet brushless motor and includes three Hall effect sensors A, B, and
A motor angle sensor 9 made of C is attached. Details of the motor angle sensor 9 will be described below with reference to FIG.

FIG. 17A is a block diagram showing the arrangement of the motor 8 and the three Hall effect sensors A, B and C. Figure 1
In FIG. 7A, the motor angle sensors 9 are arranged at equal intervals around the rotor electromagnet 100 of the motor and detect the rotation angle of the rotor. That is, each of the sensors A, B, and C can detect the rotation angle of the rotor by detecting whether the north pole or the south pole of the rotor magnet is in the detection range. FIG. 17B shows the motor 8 shown in FIG.
In the above configuration, the combination of the polarities of the rotor magnets detected by the sensors A, B, and C while the motor 8 rotates 120 degrees is shown.

According to the structure of the motor 8, six types of rotor magnet polarities (S1 to S6) can be obtained while the motor 8 rotates 120 degrees, and the motor angle of 120 degrees is divided into six. When converted to the angle of the steering shaft 1 through the motor reduction gear 7, the following formula (1)
As described above, the resolution is 1.2 degrees.

[0007]   120 [degree] /6/16.5=1.2 [degree] ... (1)

However, the output of the motor angle sensor 9 does not represent the absolute angle from the predetermined position. When the rotation continues in the same direction, the sensor output sequence of S1 to S6 shown in FIG. 17B is repeated every 120 degrees. The motor rotation angle counter 10 is means for counting the combinations of the polarities of the rotor magnets of S1 to S6. The motor rotation angle counter 10 counts up when the output of the motor angle sensor 9 changes in the forward direction, for example, S1 → S2, S2 → S3, S3 → S4 ..., S1 → S6, S6 → S.
5, when S5 → S4 ...

The neutral point sensor 11 directly detects a rotation angle of the steering shaft 1 or another steering assembly (steering rack or the like) at a vehicle straight traveling position, a position sensor or a pressure sensor, or indirectly. The vehicle yaw rate sensor and the like.

Further, adding a concrete explanation, when the steering wheel 2 of the vehicle is turned from the left end to the right end, the steering shaft 1 normally makes 3 to 4 revolutions.
The neutral point sensor is the steering shaft 1 as shown in FIG.
Only the state where the rotation angle of is in the vehicle straight ahead position is detected. That is, while the steering wheel 2 is turned from the left end to the right end and the steering shaft rotates 3 to 4 times, the detection signal is issued only at one point corresponding to the straight ahead position of the vehicle. It does not give a signal.

Next, the steering shaft rotation angle calculating means 12
Is for calculating how much the steering shaft 1 is rotated from the straight ahead position of the vehicle. This calculated value is used for control for improving the steering feeling of the electric power steering system, or is supplied to another control device (for example, a brake control device) to improve the vehicle stability. Used for control etc. The operation flow of the steering shaft rotation angle calculation means 12 will be described below.

FIG. 19 shows a steering shaft rotation angle calculating means 1
6 is a flowchart showing the operation of No. 2. First, in step S19-1, the steering shaft rotation angle calculation means 12 reads the detection state of the neutral point sensor 11, and proceeds to step S19-2.

In step S19-2, step S19
It is determined whether the neutral point sensor 11 read at -1 is ON ("neutral point sensor 11 is ON" when the vehicle is in the straight ahead position). As a result of the determination, the neutral point sensor 11
If is ON, the process proceeds to step S19-3, and if it is OFF, the process proceeds to step S19-4.

In step S19-3, the above step S
As a result of the determination in 19-2, when the neutral point sensor 11 is ON, the steering shaft rotation angle calculation means 12 resets the count value of the motor rotation angle counter 10 to zero. FIG. 18 is a correlation diagram schematically showing the relationship between the steering shaft rotation angle and the motor rotation angle. Step S19-3
By resetting the count value at, the value of the motor rotation angle counter 10 becomes according to the steering shaft rotation angle, as shown in FIG.

Next, in step S19-4, the steering shaft rotation angle calculation means 12 reads the count value from the motor rotation angle counter 10. Then, step S1
In 9-5, the steering shaft rotation angle is calculated by the following equation (2). Steering shaft rotation angle [degree] = (motor rotation angle counter value) × 1.2 (2)

By the above operation, the rotation angle of the steering shaft 1 from the straight ahead position of the vehicle is calculated. In addition, as an exception, after starting the apparatus, until the neutral point sensor 11 is turned on for the first time, steps S19-1 and S19-.
Repeat 2 (dotted line in the figure).

[0017]

As described above, in the conventional electric power steering control device, the neutral point sensor 11 accurately detects the vehicle straight traveling position of the steering shaft 1, and the motor rotation angle counter 10 is reset to zero. It is important to. Therefore, in the process of assembling the neutral point sensor 11, in order to accurately detect the vehicle straight traveling position of the steering shaft 1, high accuracy is required for the mounting position and the cost becomes very high. there were.

The present invention has been made in order to solve the above-mentioned problems. In the process of assembling the neutral point sensor, it is possible to obtain a steering shaft rotation angle with high resolution and high accuracy without requiring precision in the mounting position. An object is to realize an electric power steering control device that can be obtained.

[0019]

The electric power steering control device according to the present invention detects that the rotation angle of the steering shaft that specifies the traveling direction of the vehicle is at a predetermined point within the steering shaft movable range. Neutral point detecting means, a motor angle detecting means for detecting a rotation angle of a motor that applies an auxiliary torque to the steering shaft via a gear, and the motor based on the motor rotation angle detected by the motor angle detecting means. Counter means for counting the number of rotations of a predetermined angle for each rotation direction, motor rotation direction detection means for detecting the rotation direction of the motor, steering torque detection means for detecting the steering torque generated by the rotation operation of the steering shaft, Steering shaft rotation angle calculation means for calculating the rotation angle of the steering shaft from the straight ahead position of the vehicle. The ring shaft rotation angle calculation means resets the count value of the counter means according to the detection result of the neutral point detection means, and the steering shaft reaction force estimated value is calculated based on the steering torque and the current signal flowing to the motor. When the absolute value of the estimated value of the steering shaft reaction force is within the range in which the vehicle is recognized to be traveling straight, the count value after reset by the counter means is calculated based on the motor rotation direction. Stored for each rotation direction, average the stored counter values for each rotation direction to calculate a neutral point correction value, and calculate a steering shaft rotation angle based on the neutral point correction value and the count value by the counter means. To do.

Further, the neutral point detecting means further obtains the same detection result as the detection result at the predetermined one point at a position rotated by a predetermined rotation angle from the predetermined one point, and the steering shaft. The rotation angle calculation means resets the count value of the counter means according to the detection result of the neutral point detection means, and the steering torque and
The steering shaft reaction force estimated value is calculated based on the current signal flowing through the motor, and it is determined that the detection result by the neutral point detection means is based on the vehicle straight traveling position based on the absolute value of the steering shaft reaction force estimated value. In this case, the vehicle straight ahead position is detected, and the steering shaft rotation angle is calculated based on the neutral point correction value, the count value by the counter means, and the predetermined rotation angle from the vehicle straight ahead position. .

Further, in place of the steering torque sensor, wheel speed detecting means for detecting the rotational speed of each of the left and right wheels of the vehicle is provided, and the steering shaft rotation angle detecting means is the neutral point detecting means. The count value of the counter means is reset in accordance with the detection result, and the rotation speed difference between the left and right wheels detected by the wheel speed detection means is calculated. The neutral point correction value is calculated when the value is within the range that is recognized to exist.

Further, the neutral point detecting means is attached to the rotary shaft of the motor.

Further, in place of the motor rotation direction detection means, a motor rotation speed detection means for detecting the rotation speed of the motor is provided, and the steering shaft rotation angle calculation means is
The motor rotation direction is determined based on a comparison between the motor rotation speed detected by the motor rotation speed detection means and two threshold values consisting of a positive speed value and a negative speed value.

Further, a vehicle speed sensor for detecting the traveling speed of the vehicle is further provided, and the steering shaft rotation angle detecting means is neutral when the traveling speed of the vehicle detected by the vehicle speed sensor is equal to or higher than a preset speed. The point correction value is calculated.

The steering shaft rotation angle detecting means calculates the neutral point correction value based on the value detected by the motor rotation speed detecting means.

The steering shaft rotation angle calculating means is provided with a table in which the friction torque generated by the friction of the steering mechanism is stored in advance for each rotation direction of the motor.
The corresponding friction torque is read from the table according to the motor rotation direction, and the neutral point correction value is calculated based on the read friction torque.

The steering shaft rotation angle calculating means is
The calculated neutral point correction value is retained even during power-off.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a configuration diagram showing an electric power steering control device according to Embodiment 1 of the present invention. In FIG. 1, the same reference numerals as those in FIG. 16 indicate the same parts, and the description thereof will be omitted. As a new code, 13 is a motor rotation direction sensor for detecting the rotation direction of the motor 8, and 14 is a steering shaft rotation angle calculating means for performing a different calculation from the steering shaft rotation angle calculating means 12 in FIG.

The steering shaft rotation angle calculation means 14 includes
In addition to the count value from the motor rotation angle counter 10 and the detection signal from the neutral point sensor 11 as in the conventional example,
The steering torque signal from the steering torque sensor 6, the motor current signal flowing through the motor 8, and the motor rotation direction detected by the motor rotation direction sensor 13 are input.

The motor rotation direction sensor 13 constantly detects the rotation direction of the motor 8 and constantly outputs a signal indicating any one of left rotation, right rotation and stop state. For example, the output of the motor angle sensor 9 is as shown in FIG.
In the combination of polarities of the rotor magnets detected by the sensors A, B, and C while the motor 8 shown in FIG. 7 (b) rotates 120 degrees, S1 → S2, S2 → S3, S3 → S4 ...
If it changes in the forward direction, rotate left, S1 → S6, S6 →
If it changes in the opposite direction of S5, S5 → S4 ..., It is determined to rotate right, and if it does not change within a predetermined time, it is determined to stop. Note that these three signals are often input by the assist torque control means (not shown), so the steering shaft rotation angle calculation means 14 may be input by the assist torque control means (not shown). Other than the above, it is the same as the conventional example.

The operation of the steering shaft rotation angle calculating means 14 in the first embodiment will be described below. FIG. 2 is a flowchart showing the operation of the steering shaft rotation angle calculation means 14 in the electric power steering control device according to the first embodiment. As in the conventional example, steps S2-3 and S2-4 are repeated until the neutral point sensor is turned on for the first time after the device is activated (dotted line portion in the figure).

First, in step S2-1, the steering shaft rotation angle calculation means 14 determines whether or not the neutral point correction value has been calculated. If it has not been calculated, the process proceeds to step S2-2, the neutral point correction value is calculated by the steering shaft rotation angle calculation means 14 described later, and if it has already been calculated, the process proceeds to step S2-3.

Steps after step S2-3 (S2-
3 to S2-7) are the same as steps S19-1 to S19-5 in FIG. 19 shown in the conventional example, but the following formula (3) is used to calculate the steering rotation angle in the final step S2-7. To use.

[0034]   Steering shaft rotation angle [degree]       = (Motor rotation angle counter value-neutral point correction value) x 1.2 [degrees]                                                         (3)

Next, the operation of the steering shaft rotation angle calculating means 14 when calculating the neutral point correction value will be described.

FIG. 3 is a flow chart showing the operation at the time of calculating the neutral point correction value of the steering shaft rotation angle calculating means 14 in the electric power steering control device according to the first embodiment. First, in step S3-1, the output of the neutral point sensor 11 is read, and then in step S3.
At -2, it is determined whether the neutral point sensor 11 is ON. Until the neutral point sensor is turned on, steps S3-1 and S3-2 are continued. If the neutral point sensor is turned on, the process proceeds to step S3-3, and the motor rotation angle counter 9
The count value, the left rotation correction value storage flag, and the right rotation correction value storage flag are reset to 0. The left rotation correction value storage flag and the right rotation correction value storage flag are flags provided inside the steering shaft rotation angle calculation means 14.

Thereafter, in step S3-4, the steering torque signal, the motor current signal, the motor rotation angle counter, and the motor rotation direction sensor are read, and then step S3-.
At 5, the steering shaft reaction force estimated value is calculated using the following equation (4). Steering shaft reaction force estimated value = (steering torque signal) + (K _t × motor current signal) (4) where K _t is the torque constant of the motor 8 and the torque generated by the motor per predetermined current ( (Converted to steering axis). When the vehicle is traveling straight, the steering shaft reaction force has a very small value.

Next, in step S3-6, it is determined whether or not the absolute value of the steering shaft reaction force estimated value calculated in step S3-5 is smaller than a predetermined value. The predetermined value here is a threshold value for determining whether the vehicle is traveling straight ahead, and may be set to an optimum value from experimental data or the like.

When the absolute value of the steering shaft reaction force estimated value is smaller than the predetermined value, the process proceeds to step S3-7, and the rotation direction of the motor is determined by the value of the motor rotation direction sensor 13 read in step S3-4. If the absolute value of the steering shaft reaction force estimated value is larger than the predetermined value, the process returns to step S3-4.

Next, when it is determined in step S3-7 that the motor rotation direction is counterclockwise rotation, the process proceeds to step S3-8, and the value of the motor rotation angle counter 10 read in step S3-4 is corrected to counterclockwise rotation. The value is stored as a value, and the left rotation correction value storage flag is set to 1.

On the other hand, when it is determined that the motor is rotating in the right direction, the process proceeds to step S3-9 and step S3-4.
The value of the motor rotation angle counter 10 read in is stored as a right rotation correction value, and the right rotation correction value storage flag is set to 1.

When it is determined that the motor 8 is stopped, the process returns to step S3-4, but when it is determined that the motor 8 is rotating left or right, step S3-10. Then, it is determined whether both the left rotation correction value storage flag and the right rotation correction value storage flag are 1 and both are set to 1
In this case, in step S3-11, the neutral point correction value is calculated by the following equation (5). Neutral point correction value = (left rotation correction value + right rotation correction value) / 2 (5)

According to the above operation flow, in the first embodiment, the steering shaft rotation angle calculating means 14 can calculate the neutral point correction value.

Next, the reason why the road surface reaction force can be estimated by the equation (4) will be described in detail below. The equation of motion of the steering mechanism is expressed by the following equation (6). J × dωs / dt = T _hdl + T _mtr −T _fric × sign (ωs) −T _react (6) J: Moment of inertia of steering mechanism (converted to steering shaft) dωs / dt: Steering shaft rotational acceleration T _hdl : Steering torque T _mtr : Motor output torque (converted to steering shaft) T _fric : Friction torque of steering mechanism (converted to steering shaft) sign (ωs): Sign of rotation speed of steering shaft (rotation direction) T _react : Steering shaft _reverse Force (converted to steering shaft)

When the equation (6) is solved for the steering shaft reaction force T _react , the following equation (7) is obtained. T _react = T _hdl + T _mtr −J × dωs / dt−T _fric × sign (ωs) (7)

Therefore, from the steering torque T _hdl , the motor output torque T _mtr , the steering shaft rotational acceleration dωs / dt, and the steering mechanism friction torque T _fric , the road surface reaction force T is obtained.
It turns out that _react can be calculated. A steering torque signal T _sens from the steering torque sensor 6 is used as the steering torque T _hdl , and a motor output torque T _mtr is as follows.
The motor current signal I _mtr flowing through the motor 8 can be used by multiplying it by a known motor torque constant K _t .

Here, the term of the steering shaft rotational acceleration (-J × dωs / dt) is generally negligible unless an extremely sudden steering is performed, and the friction torque T _fric of the steering mechanism is generally left-right steering. Since the magnitudes are almost the same and the directions are opposite, the influence of the friction torque T _fric is automatically canceled by steering left and right and performing the arithmetic mean. _Therefore , the term of T _fric × sign (ωs) is also ignored. can do. From the above, the equation (4) is derived, and the neutral point correction value can be calculated based on the road surface reaction force estimated value detected by the equation (4).

In the first embodiment, since the neutral point is corrected by the estimated value of the steering shaft reaction force as described above, the vehicle is more likely to be mounted in the process of incorporating the neutral point sensor 11 into the steering shaft 1 than in the conventional case. Straight ahead position and neutral point sensor 1
Since the precision for matching the neutral point of 1 is not required, it is possible to provide the electric power steering control device with low cost. In addition, if the neutral point correction value is stored when the power of the device is cut off, the next time the device is started,
Since it is not necessary to calculate the neutral point correction value, a highly accurate steering shaft rotation angle can be obtained quickly.

In the first embodiment, when one left rotation correction value and one right rotation correction value are stored, the left rotation correction value storage flag and the right rotation correction value storage flag are set to 1, respectively. However, it is not limited to this, for example,
When 100 data of the left rotation correction value and the right rotation correction value are stored, the left rotation correction value storage flag and the right rotation correction value storage flag are set to 1, and the neutral point correction value is calculated by the following equation (8). If calculated, it becomes an average value of many data, and a more accurate neutral point correction value can be calculated. The same applies to the embodiments described below. Neutral point correction value = (sum of left rotation correction values [1] to [100] + sum of right rotation correction values [1] to [100]) / 200 (8)

Although the motor rotation direction sensor 13 always outputs a signal indicating any one of left rotation, right rotation and stop state, it is equipped with a motor rotation speed sensor and the detected motor rotation speed is steered. It may be input to the shaft rotation angle calculation means 14 and a left rotation, a right rotation, or a stopped state may be determined using a threshold value. The same applies to the embodiments described below. Specifically, for example, when a motor rotation direction sensor is provided so as to detect the speed when the motor is rotating counterclockwise as a positive speed value, it is detected as a negative speed value when rotating clockwise. The Rukoto. Therefore, for example, if +0.1 is set as the first threshold value and -0.1 is set as the second threshold value, if the detection value of the motor rotation speed sensor is +0.1 or more, left rotation, -0 ．
If it is 1 or less, it can be determined to be clockwise rotation, and if it is in the range of −0.1 to +0.1, it can be determined to be a stopped state.

Further, the resolution of the motor angle sensor 9 is set to 1.2.
However, the present invention is not limited to this, and 1.2 [degree] in the equation (3) may be changed according to the resolution of the motor angle sensor 9. The same applies to the embodiments described below.

Further, although the neutral point correction value is calculated only once in the first embodiment, the neutral point correction value may be calculated a plurality of times and the average value thereof may be used. The same applies to the embodiments described below.

Embodiment 2. The steering mechanism is generally a mechanism that ensures symmetric operability when the steering wheel 2 is operated to the left or right, but some vehicles do not have symmetric operability. In the second embodiment, the friction torque T _fric is stored in advance as a table for each rotation direction, and the friction torque T _fric corresponding to the steering shaft rotation direction, that is, the motor rotation direction is _stored.
Is read from the table, and the steering shaft reaction force estimated value is calculated by the following equation (9).

Steering shaft reaction force estimated value = steering torque signal + (K _t × motor current signal) + friction torque value (9)

FIG. 4 is a flowchart showing the operation of the electric power steering control device according to the second embodiment when calculating the neutral point correction value of the steering shaft rotation angle calculating means 14 different from that of the first embodiment. . The operation of the steering shaft rotation angle calculation means 14 when calculating the neutral point correction value will be described below with reference to FIG.

In FIG. 4, step S4-1 to step S4-4 are the same as step S3-1 to step S3-4 of FIG. In step S4-5, the friction torque value corresponding to the motor rotation direction detected by the motor rotation direction sensor 13 read in step S4-4 is read from the table. Next, in step S4-6, the steering axis reaction force estimated value is calculated using the equation (9).

In step S4-7, the above step S4 is executed.
The absolute value of the steering shaft reaction force estimated value calculated in -6 is
It is determined whether it is smaller than a predetermined value. The predetermined value here is a threshold value for determining whether the vehicle is traveling straight ahead, and may be set to an optimum value from experimental data or the like. Next, in step S4-8, the count value of the motor rotation angle counter 10 is read.

As described above, according to the second embodiment,
Even in a vehicle in which the operability of the steering mechanism is asymmetrical, the neutral point correction value can be calculated with high accuracy. Further, the neutral point correction value can be calculated in a short time without averaging the correction values for the respective motor rotation directions.

Third Embodiment Under actual traveling conditions, there is a steering pattern (for example, when changing lanes at high speed) that allows the neutral point to be calculated more accurately. In the third embodiment, in order to accurately calculate the neutral point correction value, the vehicle speed sensor is provided, so that the traveling speed of the vehicle detected by the vehicle speed sensor is higher than the predetermined value (or the vehicle speed is within the predetermined range). ) Calculate the neutral point correction value based on the data only in the case.

FIG. 5 is a flowchart showing the calculation of the neutral point correction value in the electric power steering control device according to the third embodiment. In FIG. 5, steps S5-1 to S5-3 are the same as those in the first embodiment.
Since it is the same as steps S3-1 to S3-3 in step 1, the description thereof will be omitted. In step S5-4, the vehicle traveling speed is read by the vehicle speed sensor. Next, in step S5-5, if the vehicle traveling speed is higher than a predetermined value, step S5
If it is smaller than the predetermined value, the process proceeds to step S5.
-4 and S5-5 are repeated.

In step S5-6, the steering torque signal,
The values of the motor current signal, motor rotation angle counter, and motor rotation direction sensor are read. The subsequent steps are the same as steps S3-5 to S3-11 of FIG. 3 in the first embodiment.

As described above, in the electric power steering control apparatus according to the third embodiment, the steering axis reaction force estimated value can be calculated only when the vehicle traveling speed is equal to or higher than the predetermined value or within the predetermined range. Therefore, the neutral point correction value can be calculated only when the vehicle is traveling in a desired manner and the neutral point can be calculated accurately.

Similarly, by providing a motor rotation speed sensor, data only when the motor rotation speed or the differential value of the motor rotation speed (motor rotation acceleration) is larger than a predetermined value (or within a predetermined range) The neutral point correction value can also be calculated based on

Fourth Embodiment Embodiment 1 described above
3 to 3, the neutral point sensor 11 is not turned on every time the steering shaft 1 goes around, but the steering wheel 1 is turned from the left end to the right end by turning the steering shaft 1 to 3 to 3.
While it is assumed that it is turned on only at one point corresponding to the straight ahead position of the vehicle during four rotations, the neutral point sensor 11 according to the fourth embodiment is turned on each time the steering shaft 1 goes around. is there. That is, as shown in FIG. 6, not only when the rotation angle of the steering shaft 1 is in the vehicle straight traveling position,
The neutral point sensor is turned on even when the rotation angle is +360 degrees or -360 degrees.

The configuration of the electric power steering control device according to the fourth embodiment includes a vehicle speed sensor as in the third embodiment. The operation flow of the steering shaft rotation angle calculation means 14 will be described.

First, in step S7-1, the steering shaft rotation angle calculating means 14 determines whether or not the neutral point correction value has been calculated. If the result of determination is that calculation has been completed, processing advances to step S7-4. On the other hand, if it has not been calculated, the process proceeds to step S7-2 to calculate the neutral point correction value. Here, the process of calculating the neutral point correction value according to the fourth embodiment will be described. FIG. 8 shows a fourth embodiment of the present invention.
5 is a flowchart showing a process of calculating a neutral point correction value in the steering shaft rotation angle calculating means according to the first embodiment. Hereinafter, FIG. 8 will be described.

First, in step S8-1, the detection values of the vehicle speed sensor and the neutral point sensor are read, and in step S8
At -2, it is determined whether the vehicle speed is higher than a predetermined value and the neutral point sensor is ON. If the determination result is Yes, the process proceeds to step S8-3, and if No, step S8-.
Step S8-1, S until the judgment result of 2 becomes Yes
Repeat 8-2.

In step S8-3, the steering torque signal and the motor current signal are read, and in step S8-4, the steering shaft reaction force estimated value is calculated by the equation (4). Next, in step S8-5, it is determined whether the steering shaft reaction force estimated value is smaller than the predetermined value A or not. The predetermined value A here is that the rotation angle of the steering shaft 1 is in the vehicle straight-ahead position in step S8-1, and the neutral point sensor 11
Is turned on, or +36 to it
It is determined whether the neutral point sensor is turned on at a rotation angle of 0 degree or -360 degrees, and an optimum value may be set based on experimental data or the like. Subsequent processing,
This is similar to the first to third embodiments.

The predetermined value B is a threshold value for determining whether the vehicle is traveling straight ahead, as in the first to third embodiments, and if an optimum value is set from experimental data or the like. good.

After calculating the neutral point correction value, returning to FIG. 7, the orbit value is reset to 0 in step S7-3, the neutral point sensor is read in step S7-4, and step S7-4 is executed.
At 7-5, it is determined whether the neutral point sensor 11 is ON. Here, in step S7-6, when the neutral point sensor 11 is ON, the revolution value is updated. The orbital value is a variable in the steering shaft rotation angle calculation means 14, and indicates how many times the rotation angle of the steering shaft 1 is rotated from the straight ahead position of the vehicle. FIG. 9 is a flow chart showing the process of updating the circulation value.

In FIG. 9, a predetermined value C indicates that the steering shaft 1 makes one rotation to the left from the vehicle straight ahead position, and a predetermined value D indicates that the steering shaft 1 makes one rotation to the right from the vehicle straight ahead position. It is a threshold value for judging from the value of the counter 10. The determination condition may be larger than the predetermined value C, smaller than the predetermined value D, or the like. The process after updating the revolution value is the same as in the first to third embodiments, but the following formula (10) is used to calculate the steering rotation angle in the final step S7-9.

[0072] Steering shaft rotation angle [degree] = (motor rotation angle counter value-neutral point correction value)                                 × 1.2 [degree] + circulation value × 360 [degree]                                                       (10)

FIG. 10 is a correlation diagram showing the correspondence between the value of the motor rotation angle counter and the steering shaft rotation angle. In the fourth embodiment, the correspondence relationship shown in FIG. 10 is established at the time of calculation by equation (10).

As described above, in the fourth embodiment, the rotation angle of the steering shaft 1 is at the vehicle straight-ahead position and the neutral point sensor 11 is turned on, or +360 degrees, -360 degrees. After determining whether the neutral point sensor 11 is turned on at the angle of rotation determined by the steering shaft reaction force estimated value, the motor rotation is performed when the rotation angle of the steering shaft 1 is at the vehicle straight traveling position. The corner counter 10 is reset and the neutral point correction value is calculated.

As described above, according to the electric power steering control device of the fourth embodiment, the revolution value is updated every time the neutral point sensor 11 is turned on, and the steering shaft is rotated in consideration of the revolution value. Since the angle is calculated, the neutral point sensor 11 can calculate the steering shaft rotation angle even if the neutral point sensor 11 is turned on each time the steering shaft 1 goes around.

In the electric power steering control device according to the fourth embodiment, even if the neutral point correction value and the orbit value are stored when the power is cut off, if the steering wheel is turned off while the power is cut off, There may be an error in the revolution value at the next startup. In order to prevent this, it is necessary to calculate the neutral point correction value and reset the revolution value to 0 every time the device is started.

As another method, the circulation value setting flowchart shown in FIG. 11 may be executed before step S7-1 shown in FIG. 7 to set the circulation value. However, when the revolution value is set by this revolution value setting flowchart, it is necessary to previously store a table in which the steering shaft reaction force estimated value and the revolution value are associated with each other in the steering shaft rotation angle calculating means 14 or the like. When this orbit value setting flow chart is executed before step S7-1, the neutral point correction value may use the previously stored value, and a highly accurate steering shaft rotation angle can be obtained quickly.

In the fourth embodiment, the neutral point sensor 11 is not limited to the case where the rotation angle of the steering shaft 1 is in the vehicle straight traveling position, but is +360 degrees or -36 degrees.
It is assumed that the neutral point sensor 11 is turned on even when the rotation angle is 0 degrees, but the present invention is not limited to this.
As described above, the rotation angle may be +90 or −90, or the neutral point sensor 11 may be turned on.

In this case, instead of the "turning value", "quarter turn value" is set, and in the final step S7-9, the steering shaft rotation angle is calculated by the equation (11). Steering shaft rotation angle [degree] = (motor rotation angle counter value−neutral point correction value) 1.2 [degree] + (circulation value / 4) × 90 [degree] (11)

Embodiment 5. FIG. 13 shows the fifth embodiment.
It is a system block diagram of the electric power steering control device which concerns on this, and attaches the neutral point sensor 11 in the said Embodiment 1-4 to the rotating shaft of the motor 8. The neutral point sensor 11 is turned on every time the motor 8 makes one rotation.
It will be. When the motor deceleration gear 7 is, for example, 16.5: 1 as in the conventional example, it is converted into a rotation angle of the steering shaft of + 360 / 16.5 [degrees], -360/1.
The neutral point sensor 11 is turned on every 6.5 [degrees].

The operation of the steering rotation angle calculation means 14 in the fifth embodiment is the same as that in the fourth embodiment, except that the "motor revolution value" is used instead of the "motor revolution value" in the fourth embodiment. In the final step S7-9, the expression (1
The steering shaft rotation angle is calculated by 2). Steering shaft rotation angle [degree] = (motor rotation angle counter value−neutral point correction value) × 1.2 [degree] + motor revolution value × 360 / 16.5 [degree] ... (12)

As described above, in the electric power steering control device according to the fifth embodiment, the neutral point sensor 11
Is attached to the rotary shaft of the motor 8, the neutral point sensor 1
1 and the motor 8 can be housed in an integrated package, and in addition to the effects of Embodiments 1 to 4, it is possible to provide an electric power steering control device with low assembly cost.

Sixth Embodiment Embodiment 1 described above
5 to 5, the calculation of the neutral point correction value is performed by referring to whether or not the steering axis reaction force estimated value is smaller than a predetermined value, but in the sixth embodiment, rotation of the left and right front wheels is performed. It is referred to whether the speed difference is smaller than a predetermined value. (When the vehicle travels straight, the difference in rotation speed between the left and right front wheels becomes zero.)

FIG. 14 is a system configuration diagram of an electric power steering control device according to the sixth embodiment. Figure 1
4, the wheel speed detection sensor 15 detects the rotation speed of each wheel, and the detected wheel speed values are read by the steering shaft rotation angle detection means 14.

Next, FIG. 15 shows an operation flowchart for calculating the neutral point correction value of the steering shaft rotation angle calculating means 14 in the electric power steering control device according to the sixth embodiment. Since the method for calculating the neutral point correction value here is almost the same as the method for calculating the neutral point correction value shown in FIG. 4 in the second embodiment, only the differences from FIG. 4 will be described.

In FIG. 15, steps S15-1 and S15 are performed.
15-2 is the same as steps 4-1 and S4-2 in FIG. In step S4-3, the motor rotation angle counter, the left rotation correction value storage flag, and the right rotation correction value storage flag are reset to 0, but only the motor rotation angle counter is reset to 0 in step S15-3.

Next, in step 15-4, the values of the motor rotation angle counter, the left front wheel speed sensor, and the right front wheel speed sensor are read, and in step S15-5, the left front wheel speed sensor and the right front wheel speed read in step S15-4 are read. It is determined whether the absolute value of the difference between the wheel speed sensor and the wheel rotation speed is smaller than a predetermined value. It should be noted that the predetermined value here is a threshold value indicating whether or not the vehicle is traveling straight ahead, and may be set to an optimum value from experimental data or the like.

As a result of the determination in step S15-5, if the absolute value of the difference between the right wheel speed sensor and the wheel rotation speed is smaller than the predetermined value, the motor rotation angle counter read in step S15-4 is read. If the absolute value of the difference between the right wheel speed sensor and the wheel rotation speed is larger than the predetermined value, the value is set as the neutral point correction value, and step S15 is performed.
-4 and S15-5 are repeated.

As described above, the steering shaft rotation angle calculating means 14 can calculate the steering shaft rotation angle based on the acquired neutral point correction value in the same manner as in the above-described first to fifth embodiments. Also in the sixth embodiment, in the process of assembling the neutral point detecting means on the steering shaft, there is no need for the precision for matching the vehicle straight-ahead position and the neutral point of the neutral point detecting means, and the electric power steering control is low in cost. A device can be provided.

Further, according to the electric power steering control device of the sixth embodiment, the steering shaft rotation angle calculating means 14 or the like stores a table in which the left-right wheel speed difference and the revolution value are associated in advance, and the above-described embodiment is performed. 11 for the form 4 of FIG. 11, step S11-
4, the rotation speed of the left front wheel and the rotation speed of the right front wheel are input from the wheel speed detection sensor 15, and then step S11-5.
In step S11-6, the left / right wheel speed difference is obtained from the absolute value of the left / right wheel rotation speed. By extracting the value according to
As in the fourth embodiment, a highly accurate steering shaft rotation angle can be quickly obtained.

[0091]

According to the electric power steering system of the present invention, the steering shaft rotation angle calculating means resets the count value of the counter means in accordance with the detection result of the neutral point detecting means, and the steering torque and the motor are controlled. The steering shaft reaction force estimated value is calculated based on the flowing current signal, and when the absolute value of the steering shaft reaction force estimated value is within the range in which it is recognized that the vehicle is traveling straight, it is based on the motor rotation direction. The count value after reset by the counter means is stored for each rotation direction, the stored counter value for each rotation direction is averaged to calculate a neutral point correction value, and the neutral point correction value and the count after resetting are stored. By calculating the steering shaft rotation angle on the basis of the value, the vehicle straight-ahead position and the neutral point detecting means are incorporated in the process of incorporating the neutral point detecting means into the steering shaft. Without requiring precision for matching the neutral point, the cost can be provided a low electric power steering control system.

Further, the neutral point detecting means further obtains the same detection result as the detection result at the predetermined one point at the position rotated from the predetermined one point by the predetermined rotation angle, and calculates the steering shaft rotation angle. The means resets the count value of the counter means according to the detection result of the neutral point detection means, and calculates the steering axis reaction force estimated value based on the steering torque and the current signal flowing to the motor,
When the detection result of the neutral point detecting means is determined based on the absolute value of the steering shaft reaction force estimated value to be the vehicle straight traveling position, the vehicle straight traveling position is detected. Even if it is detected for each predetermined rotation angle, in the process of incorporating the neutral point detection means,
It is possible to provide a low-cost electric power steering control device that does not require the accuracy of the mounting position.

Further, in place of the steering torque sensor, wheel speed detecting means for detecting the rotation speed of each of the left and right wheels of the vehicle is provided, and the steering shaft rotation angle detecting means comprises:
The count value of the counter means is reset according to the detection result of the neutral point detection means, the rotation speed difference between the left and right wheels detected by the wheel speed detection means is calculated, and the absolute value of the rotation speed difference is When it is within the range where it is recognized that the vehicle is traveling straight, the neutral point correction value is calculated, so that the vehicle straight traveling position and the neutral point of the neutral point detecting means are set in the process of incorporating the neutral point detecting means into the steering shaft. It is possible to provide an electric power steering control device that does not require precision for matching and that is low in cost.

Since the neutral point detecting means is provided on the rotary shaft of the motor, the neutral point detecting means and the motor can be housed in an integrated package, and an electric power steering controller with low assembly cost is provided. can do.

Further, instead of the motor rotation direction detecting means,
A motor rotation speed detection means for detecting the rotation speed of the motor is provided, and the steering shaft rotation angle calculation means determines the motor rotation direction by comparing the motor rotation speed with a threshold value. The steering shaft rotation angle can be calculated without detecting

Further, a vehicle speed sensor for detecting the traveling speed of the vehicle is further provided, and the steering shaft rotation angle detecting means corrects the neutral point when the traveling speed of the vehicle detected by the vehicle speed sensor is equal to or higher than a preset speed. Since the value is calculated, the neutral point correction value can be calculated accurately.

Further, the steering shaft rotation angle detecting means is
Since the neutral point correction value is calculated based on the value detected by the motor rotation speed detecting means, the neutral point correction value can be calculated with high accuracy.

Further, the steering shaft rotation angle calculating means is
A table in which the friction torque generated by the friction of the steering mechanism is stored in advance for each rotation direction of the motor is provided, the corresponding friction torque is read from the table according to the rotation direction of the motor, and the neutral point correction value is calculated based on the read friction torque. Since the calculation is performed, the neutral point correction value can be calculated with high accuracy even in a vehicle in which the operability of the steering mechanism is left-right asymmetric. Further, the neutral point correction value can be calculated in a short time without the need of averaging left and right.

The steering shaft rotation angle calculating means is
Since the calculated neutral point correction value is retained even when the power is cut off, it is not necessary to calculate the neutral point correction value the next time the device is started, and a highly accurate steering shaft rotation angle can be obtained quickly.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an electric power steering control device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of steering shaft rotation angle calculating means according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing calculation of a neutral point correction value in steering shaft rotation angle calculation means according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing calculation of a neutral point correction value in steering shaft rotation angle calculation means according to the second embodiment of the present invention.

FIG. 5 is a flowchart showing calculation of a neutral point correction value in a steering shaft rotation angle calculation means according to a third embodiment of the present invention.

FIG. 6 is a schematic diagram showing the detection timing of the neutral point sensor according to the fourth embodiment of the present invention.

FIG. 7 is a flowchart showing an operation of a steering shaft rotation angle calculating means according to the fourth embodiment of the present invention.

FIG. 8 is a flowchart showing calculation of a neutral point correction value in a steering shaft rotation angle calculating means according to a fourth embodiment of the present invention.

[Fig. 9] Fig. 9 is a slow chart showing a process of updating a circulation value according to the fourth embodiment of the present invention.

FIG. 10 is a correlation diagram showing a correspondence relationship between a value of a motor rotation angle counter and a steering shaft rotation angle according to Embodiment 4 of the present invention.

FIG. 11 is a circulation value setting flowchart according to the fourth embodiment of the present invention.

FIG. 12 is a schematic diagram showing the detection timing of the neutral point sensor according to the fourth embodiment of the present invention.

FIG. 13 is a system configuration diagram of an electric power steering control device according to a fifth embodiment of the present invention.

FIG. 14 is a system configuration diagram of an electric power steering control device according to a sixth embodiment of the present invention.

FIG. 15 is a flowchart showing calculation of a neutral point correction value in steering shaft rotation angle calculation means according to the sixth embodiment of the present invention.

FIG. 16 is a system configuration diagram of a conventional electric power steering control device.

FIG. 17 is a layout diagram of a motor and a Hall effect sensor of a conventional electric power steering control device.

FIG. 18 is a schematic diagram showing the detection timing of the neutral point sensor in the conventional electric power steering control device.

FIG. 19 is a flowchart showing an operation of a steering shaft rotation angle calculating means in a conventional electric power steering control device.

FIG. 20 is a correlation diagram schematically showing the relationship between the steering shaft rotation angle and the motor rotation angle in the conventional electric power steering control device.

[Explanation of symbols]

1 Steering axis, 2 Steering wheel, 3
Wheels, 4 wheels, 5 gears, 6 steering torque sensor, 7
Motor reduction gear, 8 motor, 9 motor angle sensor, 1
0 motor rotation angle counter, 11 neutral point sensor, 12
Steering shaft rotation angle calculation means, 13 Motor rotation direction sensor, 14 Steering shaft rotation angle calculation means, 15
Wheel speed detection sensor.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomoyuki Inoue             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Kazumichi Tsutsumi             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F term (reference) 3D032 CC26 DA03 DA15 DA19 DA24                       DA63 DC33 EB08 EB12                 3D033 CA13 CA16 CA17 CA24 CA27

Claims (9)

[Claims] 1. A rotation angle of a steering shaft for specifying a traveling direction of a vehicle is set to a predetermined value within a steering shaft movable range.
Neutral point detecting means for detecting that there is a point, motor angle detecting means for detecting the rotation angle of the motor that gives auxiliary torque to the steering shaft via a gear, and motor rotation angle detected by the motor angle detecting means. Counter means for counting the number of times the motor has rotated a predetermined angle for each rotation direction, motor rotation direction detection means for detecting the rotation direction of the motor, and steering torque generated by the rotation operation of the steering shaft. Steering torque detecting means and steering shaft rotation angle calculating means for calculating the rotation angle of the steering shaft from the straight ahead position of the vehicle are provided, and the steering shaft rotation angle calculating means is adapted to operate in accordance with the detection result of the neutral point detecting means. The count value of the counter means is reset and based on the steering torque and the current signal flowing through the motor. When the absolute value of the steering shaft reaction force estimated value is within the range in which it is recognized that the vehicle is traveling straight ahead, the counter means based on the motor rotation direction is calculated. The count value after reset by the rotation direction is stored for each rotation direction, the stored counter value for each rotation direction is averaged to calculate a neutral point correction value, and based on the neutral point correction value and the count value by the counter means, The electric power steering control device is characterized in that the steering shaft rotation angle is calculated. 2. The electric power steering control device according to claim 1, wherein the neutral point detection means detects at the predetermined one point at a position rotated by a predetermined rotation angle from the predetermined one point. Further, the same detection result as the result is obtained, and the steering shaft rotation angle calculation means resets the count value of the counter means according to the detection result of the neutral point detection means, and the steering torque and the motor flow. The steering shaft reaction force estimated value is calculated based on the current signal, and when the detection result by the neutral point detecting means is determined to be due to the vehicle straight ahead position based on the absolute value of the steering shaft reaction force estimated value, The vehicle straight-ahead position is detected, and the neutral point correction value, the count value by the counter means, and a predetermined rotation angle from the vehicle straight-ahead position are detected. An electric power steering control system and calculates the steering shaft rotation angle based. 3. The electric power steering control device according to claim 1, further comprising wheel speed detection means for detecting the rotational speed of each of the left and right wheels of the vehicle, in place of the steering torque sensor. The steering shaft rotation angle detection means resets the count value of the counter means according to the detection result of the neutral point detection means, and calculates the rotation speed difference between the left and right wheels detected by the wheel speed detection means, An electric power steering control device, wherein a neutral point correction value is calculated when an absolute value of the rotational speed difference is within a range in which it is recognized that the vehicle is traveling straight. 4. The electric power steering control device according to claim 1, wherein the neutral point detecting means is attached to a rotary shaft of the motor. 5. The electric power steering control device according to claim 1, further comprising motor rotation speed detection means for detecting the rotation speed of the motor, in place of the motor rotation direction detection means. The steering shaft rotation angle calculation means is based on a comparison between the motor rotation speed detected by the motor rotation speed detection means and two threshold values consisting of a positive speed value and a negative speed value, and the motor rotation direction. An electric power steering control device, characterized in that 6. The electric power steering control device according to claim 1, further comprising a vehicle speed sensor for detecting a traveling speed of the vehicle, wherein the steering shaft rotation angle detecting means is the vehicle speed sensor. An electric power steering control device for calculating a neutral point correction value when the detected traveling speed of a vehicle is equal to or higher than a preset speed. 7. The electric power steering control device according to claim 5, wherein the steering shaft rotation angle detection means calculates a neutral point correction value based on a detection value by the motor rotation speed detection means. An electric power steering control device. 8. The electric power steering control device according to claim 1, wherein the steering shaft rotation angle calculation means stores in advance friction torque generated by friction of the steering mechanism for each rotation direction of the motor. An electric power steering control device comprising a table, wherein a corresponding friction torque is read from the table according to the motor rotation direction, and a neutral point correction value is calculated based on the read friction torque. 9. The electric power steering control device according to claim 1, wherein the steering shaft rotation angle calculating means holds the calculated neutral point correction value even when the power is cut off. Electric power steering control device.