JP5746264B2 - Steering control device and steering speed detection method - Google Patents

Description

  The present invention relates to a steering control device and a steering speed detection method, and more particularly to a steering control device and a steering speed detection method for assisting a driver's steering.

  In a conventional electric power steering apparatus, a motor for applying torque to a steering system (vehicle handle) is provided to assist a driver's operation. In the conventional electric power steering apparatus, the steering speed of the driver is detected using the voltage between the terminals of the motor (see, for example, Patent Documents 1 and 2).

  Patent Document 1 describes an electric power steering device that determines the angular velocity of a motor based on the voltage between terminals of the motor.

  Patent Document 2 describes an electric power steering device that detects a steering speed from the current and voltage of a motor. In Patent Document 2, the detected steering speed offset error is removed by a high-pass filter.

JP 2001-171533 A JP 2001-278083 A

  Japanese Patent Application Laid-Open No. 2004-228561 describes the detection of the angular velocity of the motor using the voltage between the terminals of the motor, but does not consider the case where the offset voltage is included in the voltage between the terminals of the motor. Therefore, when the offset voltage is included in the voltage between the terminals of the motor, there is a problem that the detected steering speed also includes the offset error.

  Patent Document 2 describes that the offset error of the steering speed is removed by a high-pass filter, but there is a problem that a low-frequency component of the steering speed is removed by the high-pass filter.

  The present invention has been made to solve such a problem, and an object thereof is to obtain a steering control device and a steering speed detection method capable of obtaining a steering speed that does not include an offset error.

The present invention includes a motor that applies a steering assist torque to a steering system of a vehicle, a steering angle information acquisition unit that detects a steering angle of the steering system, and a steering speed that is estimated from an induced voltage of the motor to estimate steering. A steering speed information acquisition unit that outputs as a speed and a steering speed obtained from the steering angle detected by the steering angle information acquisition unit, and a value obtained by subjecting the steering speed to a low-pass filter process as a correction value, the steering speed information acquisition A correction unit that corrects a low frequency component of the estimated steering speed acquired by performing a high-pass filter process on the estimated steering speed acquired by a unit by adding the correction value, and outputs the corrected steering speed as a steering speed of the steering system; Is a steering control device.

The present invention includes a motor that applies a steering assist torque to a steering system of a vehicle, a steering angle information acquisition unit that detects a steering angle of the steering system, and a steering speed that is estimated from an induced voltage of the motor to estimate steering. A steering speed information acquisition unit that outputs as a speed and a steering speed obtained from the steering angle detected by the steering angle information acquisition unit, and a value obtained by subjecting the steering speed to a low-pass filter process as a correction value, the steering speed information acquisition A correction unit that corrects a low frequency component of the estimated steering speed acquired by performing a high-pass filter process on the estimated steering speed acquired by a unit by adding the correction value, and outputs the corrected steering speed as a steering speed of the steering system; Therefore, a steering speed that does not include an offset error can be obtained.

It is a block diagram which shows the steering control apparatus by Embodiment 1 of this invention, and its periphery. It is a block diagram which shows the structure of the steering control apparatus by Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the steering control apparatus by Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the steering speed calculating part of the steering control apparatus by Embodiment 2 of this invention. It is a block diagram which shows a part of internal structure of the steering speed calculating part of the steering control apparatus by Embodiment 2 of this invention. It is a block diagram which shows a part of modification of the internal structure of the steering speed calculating part of the steering control apparatus by Embodiment 2 of this invention. It is a figure which shows the effect of the steering control apparatus by Embodiment 2 of this invention. It is a flowchart which shows operation | movement of the steering speed calculating part of the steering control apparatus by Embodiment 3 of this invention. It is a block diagram which shows a part of internal structure of the steering speed calculating part of the steering control apparatus by Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing a steering control device according to Embodiment 1 of the present invention and its surroundings. The steering control device is mounted on a vehicle such as an automobile. The vehicle is provided with two front wheels (steered wheels 3) and two rear wheels (drive wheels) (not shown). As shown in FIG. 1, the vehicle is provided with a steering wheel 1 that is a steering system for a driver to operate. A steering shaft 2 is connected to the handle 1. Two steered wheels 3 are connected to the steering shaft 2. When the driver steers the steering wheel 1, the left and right steered wheels 3 are steered according to the rotation of the steering shaft 2. The steering wheel 1 is provided with a steering angle sensor 4 for detecting a steering angle. A torque sensor 5 is disposed on the steering shaft 2. The torque sensor 5 detects a steering torque that acts on the steering shaft 2. Further, the motor 6 is connected to the steering shaft 2 via the speed reduction mechanism 7. The steering assist torque generated by the motor 6 is applied to the steering shaft 2. The vehicle speed is detected by a vehicle speed sensor 8. Further, a current flowing through the motor 6 (hereinafter referred to as a motor current) is detected by a current sensor 9. The voltage between the terminals of the motor 6 (hereinafter referred to as “motor voltage”) is detected by the voltage sensor 10.

  Here, the steering angle sensor 4 constitutes a steering angle information acquisition unit that acquires information related to the steering angle of the steering system of the vehicle. However, the present invention is not limited to this case, and the steering angle information acquisition unit that acquires information related to the steering angle of the vehicle steering system only needs to be able to acquire information related to the steering angle of the vehicle steering system. Also good. The yaw rate sensor is a sensor that detects the yaw rate (the change speed of the rotation angle in the turning direction of the vehicle).

  Detection values from the steering angle sensor 4, torque sensor 5, vehicle speed sensor 8, current sensor 9, and voltage sensor 10 are input to the control unit 11. The control unit 11 calculates a target steering assist torque that should be generated by the motor 6 based on the detected values, and controls the value of the current to be supplied to the motor 6 based on the target steering assist torque.

  FIG. 2 is a diagram illustrating a configuration of the steering control device according to the first embodiment. As shown in FIG. 2, the steering control device includes a steering angle sensor 4, a torque sensor 5, a vehicle speed sensor 8, a current sensor 9, a plurality of sensors including a voltage sensor 10, and a control unit 11. . As shown in FIG. 2, the control unit 11 drives the motor 6 by supplying current to the arithmetic unit 40 including a microcomputer provided with a memory (not shown) including ROM and RAM, and the motor 6. And a current driver 19.

  In the first embodiment, the steering wheel 1 is neutral even in a region where the steering assist of the driver (hereinafter referred to as steering assist control) and the road surface reaction torque are small and the steering wheel 1 does not return to the neutral position. A steering control device having control for returning to the position (hereinafter referred to as steering wheel return control) will be described as an example.

  In the calculation device 40, as shown in FIG. 2, a steering speed calculation unit 12, a steering determination unit 13, a target steering speed setting unit 14, a first steering assist torque calculation unit 15, and a steering state determination A unit 16, a second steering assist torque calculating unit 17, and an adding unit 18 are provided.

  The steering speed calculation unit 12 receives detection values from the steering angle sensor 4, the current sensor 9, and the voltage sensor 10, and calculates the steering speed based on these detection values. The steering speed calculation unit 12 acquires a motor current from the current sensor 9 and acquires a motor voltage from the voltage sensor 10. The steering speed calculation unit 12 obtains an induced voltage of the motor 6 from the motor current and the motor voltage. A method for calculating the induced voltage will be described in Embodiment 2. Next, the steering speed calculation unit 12 estimates the steering speed based on the induced voltage. However, the estimated steering speed includes an offset error due to the contact portion oxide film and aging degradation. Therefore, the steering speed calculation unit 12 obtains a correction value for correcting the estimated steering speed based on the steering angle acquired from the steering angle sensor 4. The steering speed calculator 12 corrects the estimated steering speed using the correction value, and outputs the corrected steering speed.

  Here, the steering speed calculation unit 12 obtains the steering speed information acquisition unit that acquires the first information about the steering speed of the steering system, and the first information acquired by the steering speed information acquisition unit as the steering angle information. A correction unit is configured to perform correction based on information related to the steering angle of the steering system acquired by the acquisition unit (steering angle sensor or yaw rate sensor), and to acquire second information related to the steering speed of the steering system. Here, as the first information regarding the steering speed of the steering system, the induced voltage of the motor 6 is taken as an example. However, the present invention is not limited to this, and the steering speed obtained from a device that detects the steering speed, such as a resolver. May be the first information. The detailed operation of the steering speed calculation unit 12 will be described in Embodiments 2 and 3 described later.

  The steering holding determination unit 13 determines whether or not the steering system of the vehicle is in the steering holding state. That is, the steering retention determination unit 13 determines whether or not the steering wheel 1 remains at a substantially constant steering angle. The steering holding determination unit 13 uses the steering speed calculated by the steering speed calculation unit 12, determines that the steering holding state is “low” when the steering speed is smaller than a threshold, and outputs the steering angle at that time. On the other hand, when the steering speed is equal to or higher than the threshold value, it is determined that the vehicle is not in the steered state, the output steering angle is not updated, and the steering angle at the time of the previous steered determination is output.

  The target steering speed setting unit 14 receives the steering angle from the steering angle sensor 4, the vehicle speed from the vehicle speed sensor 8, and the steering angle from the steering hold determination unit 13. The target steering speed setting unit 14 calculates a target steering speed based on these values. As a calculation method, for example, a look-up table storing target steering speeds for these values is stored in advance, and the steering angle from the steering angle sensor 4, the vehicle speed from the vehicle speed sensor 8, and Alternatively, the steering angle value from the steering determination unit 13 may be input to obtain the corresponding target steering speed. Alternatively, an arithmetic expression for obtaining the target steering speed is stored, and the steering angle from the steering angle sensor 4, the vehicle speed from the vehicle speed sensor 8, and the steering angle from the steering holding determination unit 13 are input to the arithmetic expression. Thus, the target steering speed may be obtained.

  The first steering assist torque calculator 15 receives the steering speed calculated by the steering speed calculator 12 and the target steering speed calculated by the target steering speed setting unit 14. The first steering assist torque calculator 15 calculates a deviation between the steering speed and the target steering speed, and calculates the first steering assist torque based on the deviation. The first steering assist torque is a torque for returning the handle 1 to the neutral position. Note that the first steering assist torque is calculated by storing in advance a look-up table in which the value of the first steering assist torque with respect to the deviation between the steering speed and the target steering speed is stored. And the corresponding first steering assist torque value may be obtained. Alternatively, an arithmetic expression for obtaining the first steering assist torque is stored in advance from the deviation between the steering speed and the target steering speed, and the first steering assist torque is obtained by inputting the value of the deviation into the arithmetic expression. You may do it.

  The first steering assist torque calculated by the first steering assist torque calculator 15 is input to the steering state determination unit 16. The steering state determination unit 16 determines whether or not the first steering assist torque calculated by the first steering assist torque calculation unit 15 is necessary, and determines that the first steering assist torque is unnecessary when it is determined to be necessary. When judged, 0 is output. Here, based on the steering torque from the torque sensor 5, it is determined whether or not the driver has released the steering wheel. If the driver releases the handle, the first steering assist torque is applied. And In the present embodiment, the determination as to whether or not the hand is released is described as an example in which the detection value (absolute value) of the torque sensor 5 is determined to be the steering state when the detected value (absolute value) is equal to or greater than the threshold, and released when the value is less than the threshold.

  A steering torque is input from the torque sensor 5 to the second steering assist torque calculator 17. The second steering assist torque calculator 17 calculates a second steering assist torque for assisting the driver's steering based on the steering torque. The second steering assist torque is calculated by storing a look-up table storing the value of the second steering assist torque with respect to the steering torque in advance, and inputting the steering torque value into the look-up table. The corresponding second steering assist torque value may be obtained from the lookup table. Alternatively, a calculation formula for obtaining the second steering assist torque from the steering torque may be stored in advance, and the value of the steering torque may be input to the calculation formula to obtain the second steering assist torque.

  The adder 18 includes an output value from the steering state determination unit 16 (that is, the first steering assist torque from the first steering assist torque calculator 15 or 0), and a second steering assist torque calculator. The second steering assist torque from 17 is input. The adder 18 adds the output value from the steering state determination unit 16 and the second steering assist torque, and calculates the final steering assist torque.

  The current driver 19 supplies a current based on the steering assist torque obtained by the adding unit 18 to the motor 6 to drive the motor 6. Thereby, the motor 6 generates a necessary steering assist torque.

  Next, the operation of the steering control device according to the first embodiment will be described. FIG. 3 is a flowchart showing the operation of the steering control device according to the first embodiment. Note that the operation of FIG. 3 is repeatedly executed every control cycle.

  First, in step S1, the control unit 11 detects the steering angle from the steering angle sensor 4, the motor voltage from the voltage sensor 10, the motor current from the current sensor 9, the driver steering torque from the torque sensor 5, and the vehicle speed sensor 8. The vehicle speed is obtained from each.

  In step S2, first, the steering speed calculation unit 12 obtains an induced voltage from the motor current and the motor voltage. Next, the steering speed calculation unit 12 calculates the steering speed using the steering angle and the induced voltage, and outputs the steering speed.

  In step S3, the steering determination unit 13 determines whether or not the steering system of the vehicle is in the steering holding state, and outputs the steering angle at that time when it is determined as the steering holding state. On the other hand, if it is determined that the steering is not maintained, the steering angle is not updated and the steering angle at the previous steering determination is output.

  In step S4, the target steering speed setting unit 14 calculates the target steering speed based on the steering angle and vehicle speed acquired in step S1 and the steering angle obtained in step 3, and sets the target steering speed.

  In step S5, the first steering assist torque calculator 15 calculates the first steering assist torque based on the deviation between the target steering speed and the steering speed.

  In step S6, the steering state determination unit 16 determines whether or not the first steering assist torque calculated by the first steering assist torque calculation unit 15 is necessary. When it is determined that the first steering assist torque is necessary, the first steering assist torque is determined. When it is determined that it is unnecessary, 0 is output. Here, as a determination as to whether or not it is necessary, based on the steering torque from the torque sensor 5, it is determined whether or not the driver has released the handle, and if it is released, the first steering assist torque is output, If it is not released, the first steering assist torque is output as 0.

  In step S7, the second steering assist torque calculation unit 17 calculates a second steering assist torque that assists the driver's steering based on the steering torque acquired in step S1.

  In step S8, the adding unit 18 adds the first steering assist torque output from the steering state determining unit 16 and the second steering assist torque output from the second steering assist torque calculating unit 17, and finally. Is output as an appropriate steering assist torque.

  In step S9, the current driver 19 supplies current to the motor 6 based on the final steering assist torque obtained in step S8, and drives the motor 6.

  In the steering wheel return control in the steering control device as described above, the steering holding state is determined from the steering speed and the threshold value. Therefore, when there is an offset error in the steering speed or when the resolution is low, the steering retention determination may be erroneously determined. Further, the first steering assist torque for returning the handle 1 to the neutral position generates the steering assist torque so that the steering speed follows the target steering speed. Therefore, when the steering assist torque includes an offset error, an appropriate steering assist torque cannot be obtained, and the steering wheel return feeling may be deteriorated. Therefore, in the first embodiment, by applying the steering speed calculation processing shown in the following second and third embodiments to the steering speed calculation unit 12, high response and high resolution, and A steering speed with suppressed offset error can be obtained, and a suitable steering wheel return feeling according to the target steering speed can be obtained.

  As described above, in the first embodiment, the steering angle information acquisition unit that acquires information about the steering angle of the steering system of the vehicle, and the steering speed information acquisition unit that acquires the first information about the steering speed of the steering system. And the first information regarding the steering speed acquired by the steering speed information acquisition unit is corrected based on the information regarding the steering angle acquired by the steering angle information acquisition unit, and the second information regarding the steering speed of the steering system is corrected. Therefore, in order to correct the first information relating to the steering speed including the offset error with the information relating to the steering angle, the second information relating to the steering speed not including the offset error is obtained. Can be sought.

  In particular, in the embodiment shown in FIG. 2, a current (motor current) flowing in the steering angle sensor 4 that detects the steering angle of the steering wheel 1 that is the steering system of the vehicle and the motor 6 that applies torque to the steering system is detected. The current sensor 9, the voltage sensor 10 that detects the voltage (motor voltage) between the terminals of the motor 6, the steering angle detected by the steering angle sensor 4, the current detected by the current sensor 9, and the voltage sensor 10 A steering speed calculation unit 12 for obtaining a steering speed of the steering system based on the obtained voltage, a steering assist torque is calculated based on the steering speed of the steering system obtained by the steering speed calculation unit 12, and the first steering assistance torque is calculated. As a first steering assist torque calculator 15 and a current driver 19 for driving the motor 6 based on the first steering assist torque. Accordingly, the steering speed is estimated as the first steering speed (first information regarding the steering speed), and a correction value (information regarding the steering angle) for correcting the first steering speed is calculated based on the steering angle. The first steering speed is corrected using the correction value, and is output as the steering speed of the steering system (second information regarding the steering speed). With this configuration, the first embodiment corrects the first steering speed including the offset error (first information related to the steering speed with a correction value (information related to the steering angle) obtained according to the steering angle). A steering speed that does not include an offset error (second information regarding the steering speed) can be obtained.

  In the first embodiment, the induced voltage of the motor 6 is obtained based on the current detected by the current sensor 9 and the voltage detected by the voltage sensor 10, and the first steering speed is calculated based on the induced voltage. (First information regarding the steering speed) is obtained. Thereby, a high-resolution steering speed can be obtained.

  In the first embodiment, the torque sensor 5 is disposed in the steering system and detects the steering torque of the steering system, and the second steering assist torque is based on the steering torque of the steering system detected by the torque sensor 5. And a current driver 19 based on the added value obtained by adding the first steering assist torque and the second steering assist torque by the adding unit 18. The motor 6 was driven. Thus, the steering assist torque is calculated using both the first steering assist torque for returning the handle 1 to the neutral position and the second steering assist torque for assisting the driver's steering. Both the steering wheel return control and the steering assist control can be performed.

Embodiment 2. FIG.
In the second embodiment, the calculation of the steering speed executed by the steering speed calculation unit 12 provided in the control unit 11 will be described using the flowchart of FIG. That is, the flowchart of FIG. 4 is a diagram showing in detail the process of step S2 of the flowchart of FIG.

  Since the overall configuration and operation of the steering control device according to the second embodiment are the same as those of the first embodiment, description thereof is omitted here. In addition, the same reference numerals are used for configurations common to the above-described first embodiment, and differences from the first embodiment will be mainly described below.

  As shown in FIG. 4, first, in step S <b> 11, the steering speed calculator 12 uses the motor voltage EM from the voltage sensor 10 and the motor current IM from the current sensor 9 to use the motor 6 corresponding to the steering speed. The induced voltage EE is obtained.

  Here, the induced voltage EE of the motor 6 is obtained by the following equation (1) using the motor voltage EM and the motor current IM.

  EE = EM-IM / RM-Eb (1)

  Here, RM is an amateur resistance of the motor 6, and Eb is a drop voltage of the brush of the motor 6.

  Next, in step S12, the motor rotation speed VM is calculated from the induced voltage EE by the following equation (2).

  VM = EE / Kp (2)

  Here, Kp is an induced voltage coefficient.

Next, in step S13, the steering speed θ _omega is estimated from the motor rotation speed VM. The motor rotation speed and the steering speed have a relationship based on a reduction gear, a handle, a tire shaft rack, and a structural mechanism such as a pinion. In other words, the motor rotation speed and the steering speed are proportional. Therefore, based on the motor rotation speed, the estimated steering speed θ _omega is obtained by the following equation (3). Since the motor rotation speed is obtained based on the induced voltage, the estimated steering speed θ _omega is hereinafter referred to as “estimated steering speed based on the induced voltage” (first steering speed).

θ _omega = G _gear × VM (3)

Here, G _gear is a proportionality coefficient determined by the above structural mechanism.

However, since the drop voltage Eb of the brush of the motor 6 changes due to the influence of the contact portion oxide film and aging deterioration, the induced voltage EE includes those changes as an offset error. Thereby, the steering speed θ _omega estimated from the induced voltage EE also includes an offset error.

Therefore, in step S14, the steering speed calculation unit 12 corrects the steering speed θ _omega using information obtained from the steering angle. FIG. 5 shows the configuration. In FIG. 5, 21 is a high-pass filter to which the steering speed θ _omega is input. Reference numeral 22 denotes a low-pass filter to which a steering speed sθ _h calculated from the steering angle is input. An adder 23 adds the output from the high-pass filter 21 and the output from the low-pass filter 22.

The configuration of FIG. 5 uses the speed obtained from the steering angle θ _h in the low frequency region where the offset error of the induced voltage EE affects, while using the estimated speed θ _omega based on the induced voltage EE in the high frequency region. Thus, the final steering speed θ _hybrid is calculated. When the transfer function G1 of the high-pass filter 21 is G1 = Ts / (Ts + 1) and the transfer function G2 of the low-pass filter 22 is G2 = 1 / (Ts + 1), the configuration of FIG. 5 is expressed by the following equation (4). Can do.

  Here, T is a time constant of the cutoff frequency of the high-pass filter 21 and the low-pass filter 22, and s is a Laplace operator.

In the configuration of FIG. 5, filtering processing by the high-pass filter 21 is performed to remove an offset error of the estimated steering speed θ _omega (first steering speed) based on the induced voltage EE. The cut-off frequency of the high pass filter 21 is set to a value that can remove the offset error. Therefore, the offset error of the steering speed θ _omega can be removed by the filtering process by the high pass filter 21. However, when the steering speed is a low frequency equal to or lower than the cut-off frequency of the high-pass filter 21, the steering speed is removed together with the offset error, and thus cannot be obtained by the processing of the high-pass filter 21.

Therefore, in the configuration of FIG. 5, in order to obtain a low-frequency steering speed, a steering speed sθ _h (second steering speed) obtained from the steering angle θ _h is calculated. Thus, the filtering process by the low-pass filter 22 is performed on the steering speed sθ _h obtained only from the steering angle θ _h . The cutoff frequency of the low pass filter 22 is set to the same value as the cutoff frequency of the high pass filter 21. By the filter processing by the low-pass filter 22, it is possible to obtain a steering speed having a low frequency equal to or lower than the cutoff frequency.

Thus, the cut-off frequencies of the high-pass filter 21 and the low-pass filter 22 are set to the same value, and the output results from the high-pass filter 21 and the low-pass filter 22 are added together by the adder 23. As a result, when the steering angle frequency is higher than the cutoff frequency, the steering speed using the induced voltage EE is used. On the other hand, when the steering angle frequency is equal to or lower than the cutoff frequency, the steering angle θ _h is used for steering. By using the speed, an accurate steering speed θ _hybrid that does not include an offset error can be obtained.

  Further, the above equation (4) can be equivalently transformed as the following equation (5).

This is because the high-pass filter 26 performs filtering on the sum (θ _omega + θ _h / T) of the estimated steering speed θ _omega based on the induced voltage EE and the value obtained by dividing the steering angle θ _h by the time constant T, The final steering speed θ _hybrid is obtained. Expression (5) is shown in a block diagram in FIG. 6, 24 is a divider for dividing the time constant T of the steering angle theta _h. An adder 25 adds the estimated steering speed θ _omega based on the induced voltage EE and the output of the divider 24. Reference numeral 26 denotes a high-pass filter that performs filter processing on the output of the adder 25. T is a time constant of the cutoff frequency of the high-pass filter 22, and s is a Laplace operator. The transfer function G1 of the high pass filter 26 is set to G1 = Ts / (Ts + 1).

In the equation (4), it is necessary to perform the filtering process by the high-pass filter 21 on the estimated speed θ _omega by the induced voltage EE and the filtering process by the low-pass filter 22 on the steering speed calculated from the steering angle θ _h . . Therefore, in the configuration of the expression (4) shown in FIG. 5, it is necessary to perform the calculation of the filter process twice.

  On the other hand, in the configuration of the equation (5) shown in FIG. 6, the calculation can be performed by one filtering process, and the calculation load is reduced.

  Next, the effect of the second embodiment will be described.

Since the drop voltage Eb of the brush of the motor 6 changes due to the influence of the contact portion oxide film and aging degradation, the induced voltage EE includes those changes as an offset error. Thus, there has been a conventional problem that the estimated steering speed θ _omega based on the induced voltage EE also includes an offset error.

On the other hand, the steering angle detected by the steering angle sensor 4 may have a coarse resolution. When the resolution of the steering angle sensor 4 is θ _step and the speed calculation period is T _step , the resolution of the steering speed that can be calculated from the steering angle sensor 4 is θ _step / T _step . For example, when the resolution θ _step of the steering angle sensor 4 is 1 deg and the speed calculation cycle T _step is 10 ms, the steering speed resolution is 100 deg / s, and the steering speed resolution becomes coarse. In order to make the resolution of the steering speed finer, measures to set the speed calculation cycle T _step large or to apply low-pass filter processing to the calculated steering speed can be considered, but in both cases, the response of the steering speed calculation is delayed. The problem that it ends up occurs.

Moreover, since the steering angle detected by the steering angle sensor 4 is information obtained via the CAN network, the update cycle may be long. In this case, the speed calculation cycle T _step becomes longer than the update cycle, and the response of the steering speed calculation is delayed. That is, the problem that the frequency band of speed calculation cannot be made high arises. Therefore, when the steering speed is calculated from the steering angle sensor 4, when the resolution of the steering speed is made fine, the response of the steering speed calculation is delayed, and conversely, when the response of the steering speed calculation is increased. As a result, there arises a trade-off problem that the resolution of the steering speed becomes coarse.

In the second embodiment, the steering speed calculation unit 12 obtains a high steering speed in a frequency band from which the offset is removed from the estimated steering speed θ _omega based on the induced voltage EE including an offset error, from the effect of the high-pass filter 21. It getting can, on the other hand, from the steering angle theta _h, can be from the effects of the low pass filter 22 to obtain the steering speed with no offset error high resolution. By using both of them, it is possible to obtain a steering speed with high response and high resolution and with reduced offset error.

  FIG. 7 shows the result when the setting of the cut-off frequency of the high-pass filter 21 and the low-pass filter 22 in FIG. 5 is 0.3 Hz. In FIG. 7, 30 is a graph of the steering speed according to the second embodiment, and 31 is a graph of the steering speed based on the induced voltage including an offset error. From FIG. 7, it can be seen that the offset effect of the induced voltage EE can be eliminated near the steering speed of 0, and that a favorable steering speed calculation result is obtained even in the low frequency region.

  As described above, also in the second embodiment, the first information regarding the steering speed is corrected based on the information regarding the steering angle, and the second information regarding the steering speed is acquired. The same effect as in the first embodiment can be obtained.

Furthermore, in the second embodiment (the embodiment shown in FIG. 5), based on the frequency component extracted from the steering speed information calculated from the information on the steering angle and the frequency component extracted from the first information on the steering speed. Since the second information related to the steering speed is acquired, it is possible to obtain a steering speed with high response and high resolution and with reduced offset error. Specifically, in the embodiment illustrated in FIG. 5, the steering speed calculation unit 12 calculates the steering speed of the steering system as the second steering speed based on the steering angle θ _h detected by the steering angle sensor 4. The correction value is added to the value obtained by performing the high-pass filter process on the estimated steering speed θ _omega (first steering speed) based on the induced voltage EE, using the value obtained by performing the low-pass filter process on the second steering speed as the correction value. Thus, the estimated steering speed θ _omega (first information related to the steering speed) based on the induced voltage EE is corrected and output as the steering speed of the steering system (second information related to the steering speed). In other words, a high-frequency steering speed obtained by removing the offset error from the estimated steering speed θ _omega based on the induced voltage EE including the offset error is obtained, while the high resolution low-resolution without the offset error is obtained from the steering angle θ _h. A steering speed having a frequency is obtained. In this manner, by using both steering speeds, it is possible to obtain a steering speed with high response and high resolution and with reduced offset error.

In the second embodiment (the embodiment shown in FIG. 6), since the low frequency component of the first information related to the steering speed is corrected based on the information related to the steering angle, high response and high resolution are achieved. In addition, a steering speed with reduced offset error can be obtained. Specifically, in the embodiment shown in FIG. 6, a value (information regarding the steering angle) obtained by dividing the steering angle θ _h detected by the steering angle sensor 4 by the time constant T is used as the correction value. The value obtained by adding the correction value to the estimated steering speed θ _omega (first information related to the steering speed) based on the induced voltage EE is used as the steering speed of the steering system (the second speed related to the steering speed). Information). In other words, a high-frequency steering speed obtained by removing the offset error from the estimated steering speed θ _omega based on the induced voltage EE including the offset error is obtained, while the high resolution low-resolution without the offset error is obtained from the steering angle θ _h. A steering speed having a frequency is obtained. In this manner, by using both steering speeds, it is possible to obtain a steering speed with high response and high resolution and with reduced offset error.

Embodiment 3 FIG.
In the third embodiment, a calculation method different from that of the second embodiment will be described with respect to the calculation of the steering speed executed by the steering speed calculation unit 12 provided in the control unit 11 using the flowchart of FIG. . That is, the flowchart of FIG. 8 is a diagram showing in detail the process of step S2 of the flowchart of FIG.

In the third embodiment, the same reference numerals are used for the configurations common to the first and second embodiments, and the differences from the first and second embodiments will be mainly described below. In the third embodiment, the steering speed obtained from the induced voltage when the change in the steering angle is small is stored in the memory as a correction value, and the estimated steering speed θ _omega based on the induced voltage EE is set as the correction value. It is the structure corrected using.

  FIG. 8 is a flowchart showing the operation of the steering speed calculation unit 12 of the control unit 11 according to the third embodiment. The difference from the flowchart of FIG. 4 shown in the second embodiment is that step S21 and step S22 are added in FIG. 8, and step S23 of FIG. 8 is provided instead of step S14 of FIG. It is.

In the third embodiment, first, in step S21, when the control unit 11 determines that the change in the steering angle obtained from the steering angle sensor 4 is small, the control unit 11 calculates the estimated steering speed θ _omega based on the induced voltage EE. It is obtained and stored in the memory 28 (see FIG. 9) as a correction value θ _ref . The correction value θ _ref will be described below.

When the control unit 11 can determine that the amount of change in the steering angle θ _h obtained from the steering angle sensor 4 is smaller than the threshold, that is, the steering speed θ _h is in the region near 0 (−ε <θ _h <ε , Ε is an arbitrary number), an estimated steering speed θ _omega based on the induced voltage EE at that time is obtained. The calculation method is the same as the calculation method shown in the second embodiment. The estimated steering speed θ _{omega at} this time can be regarded as an offset error from the actual steering speed of zero. Therefore, the control unit 11 stores the estimated steering speed θ _omega in the memory 28 as a steering speed correction value θ _ref .

Next, the steering speed calculation unit 12 performs the processes of steps S11 to S13 to obtain the estimated steering speed θ _omega based on the induced voltage EE. Since the processing in steps S11 to S13 is the same as the processing described in the second embodiment, the description thereof is omitted here.

Next, in step S <b> 22, the steering speed calculation unit 12 reads the steering speed correction value θ _ref stored in the memory 28 in step S <b> 21 from the memory 28.

Next, in step S23, the steering speed calculation unit 12 corrects the estimated steering speed θ _omega determined in step S13 using the steering speed correction value θ _ref stored in the memory 28. FIG. 9 shows the configuration. In FIG. 9, reference numeral 27 denotes a high-pass filter to which an estimated steering speed θ _omega based on the induced voltage EE is input. Reference _numeral 28 denotes a memory in which a steering speed correction value θ _ref is stored. An adder 29 subtracts the steering speed correction value θ _ref read from the memory 28 from the output from the high-pass filter 27.

As described above, in the third embodiment, the control unit 11 regards the steering speed obtained from the induced voltage when the change in the steering angle obtained from the steering angle sensor 4 is small as an offset error, and stores the memory in advance. 28. Then, the steering speed θ _omega based on the induced voltage EE is corrected using the correction steering speed θ _ref stored in the memory 28. Thereby, an offset error can be eliminated, and an accurate steering speed with a high resolution and a high response and a reduced offset error can be obtained, as in the second embodiment.

In the above description, as the correction value theta _ref of the steering speed has been described as using the estimated steering speed when it is determined that a small change in the steering angle theta _h.
However, the present invention is not limited to this, and the steering speed θ _omega based on the induced voltage EE at the steering speed 0 before steering by the driver at the time of system startup of the steering control device is expressed as a steering speed correction value θ. _It may be used as _ref .
Further, by using the detection value, such as wheel speed sensors and a yaw rate sensor may determine whether the change in the steering angle theta _h is small. When the wheel speed sensor is used, the wheel speeds of the front and rear wheels are compared, and when the difference is small, it can be determined that the vehicle is traveling straight. When the straight traveling state continues, it can be determined that the state where the steering angle is 0 is continued, so that the steering speed can be determined as 0. Further, when using the yaw rate sensor, it is possible to determine that there is no change in the turning state of the vehicle by using the change in the vehicle speed and the yaw rate, and it is possible to determine that the steering state, that is, the steering angle is not changed, It can be determined that the steering speed is zero.

  As described above, also in the third embodiment, the first information regarding the steering speed is corrected based on the information regarding the steering angle, and the second information regarding the steering speed is acquired. The same effect as in the first embodiment can be obtained.

  Further, in the third embodiment, the first information regarding the steering speed when the change amount of the information regarding the steering angle is smaller than the threshold value is stored in advance as a correction value (information regarding the steering angle), and the steering speed information is acquired. Since the first information related to the steering speed acquired by the unit is corrected based on the correction value (information related to the steering angle) and the second information related to the steering speed is acquired, the same as in the second embodiment An effect is obtained.

Specifically, in the above-described embodiment, it is determined whether or not the amount of change in the steering angle detected by the steering angle sensor 4 is smaller than the threshold value. Is stored in advance as a correction value θ _ref , and the estimated steering speed θ _omega (first steering speed based on the induced voltage EE when the amount of change in the steering angle is larger than the threshold value is stored. ) Is subtracted from the correction value to correct the first steering speed and output it as the steering speed of the steering system. That is, in the third embodiment, it is determined that the steering speed is near 0, and the estimated steering speed θ _omega based on the induced voltage at that time is stored in the memory 28 as the correction value θ _ref , and is used. By correcting the estimated steering speed θ _omega based on the induced voltage EE when the steering speed is not near 0, the same effect as in the second embodiment can be obtained.

  1 steering wheel, 2 steering shaft, 3 steered wheels, 4 steering angle sensor, 5 torque sensor, 6 motor, 7 deceleration mechanism, 8 vehicle speed sensor, 9 current sensor, 10 voltage sensor, 11 control unit, 12 steering speed calculation unit, 13 Steering hold determination unit, 14 Target steering speed setting unit, 15 First steering assist torque calculation unit, 16 Steering state determination unit, 17 Second steering assist torque calculation unit, 18 Addition unit, 19 Current driver.

Claims (5)

A motor for applying steering assist torque to the steering system of the vehicle;
A steering angle information acquisition unit for detecting a steering angle of the steering system;
A steering speed information acquisition unit that estimates a steering speed from the induced voltage of the motor and outputs the estimated steering speed ;
Wherein from the steering angle detected by the steering angle information acquiring unit obtains a steering speed, a high-pass filter value obtained by performing a low-pass filter process on the steering speed as the correction value, the estimated steering speed obtained by the steering speed information obtaining unit A steering control device comprising: a correction unit that corrects a low-frequency component of the estimated steering speed obtained by performing processing by adding the correction value and outputs the corrected low-frequency component as a steering speed of the steering system. A motor for applying steering assist torque to the steering system of the vehicle;
A steering angle information acquisition unit for detecting a steering angle of the steering system;
A steering speed information acquisition unit that estimates a steering speed from the induced voltage of the motor and outputs the estimated steering speed ;
The value obtained by dividing the steering angle acquired by the steering angle information acquisition unit by a time constant is used as a correction value, and the correction value is added to the estimated steering speed acquired by the steering speed information acquisition unit to correct the value. A steering control device comprising: a correction unit that outputs a value subjected to filter processing as a steering speed of the steering system. The first steering assist torque calculation unit that calculates the steering assist torque based on a deviation between a steering speed of the steering system and a target steering speed output from the correction unit. Steering control device. A steering angle information acquisition step of detecting a steering angle of a steering system of the vehicle using a steering angle sensor ;
Steering speed information acquisition step of obtaining a motor rotation speed from an induced voltage of a motor that applies a steering assist torque to the steering system of the vehicle, estimating a steering speed from the motor rotation speed, and outputting the estimated steering speed ;
Wherein from the steering angle detected by the steering angle information acquiring step obtains a steering speed, a high-pass filter value obtained by performing a low-pass filter process on the steering speed as the correction value, the estimated steering speed obtained by the steering speed information obtaining step A correction method of correcting a low frequency component of the estimated steering speed obtained by performing processing by adding the correction value and outputting the corrected low-frequency component as a steering speed of the steering system. A steering angle information acquisition step of detecting a steering angle of a steering system of the vehicle using a steering angle sensor ;
Steering speed information for obtaining a motor rotation speed from an induced voltage of a motor provided in the steering system of the vehicle and applying a steering assist torque to the steering system, estimating the steering speed from the motor rotation speed, and outputting the estimated steering speed. An acquisition step;
A value obtained by dividing the steering angle detected in the steering angle information acquisition step by a time constant is used as a correction value, and the correction value is added to the estimated steering speed acquired in the steering speed information acquisition step to correct the value. A steering speed detection method comprising: a correction step of outputting a value subjected to filter processing as a steering speed of the steering system .

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