JP4223501B2 - Electric power steering control device - Google Patents

Description

  The present invention relates to an electric power steering control device that assists a steering force with a motor.

  FIG. 12 is a block diagram illustrating a configuration example of a conventional electric power steering control device (see, for example, Non-Patent Document 1). In the figure, 1 is a torque sensor that detects steering torque when the driver steers, 2 is a phase compensator that improves the frequency characteristics of the output signal of the torque sensor 1, and 3 is a phase compensated torque sensor 1. A torque controller that calculates an auxiliary torque current for assisting the steering torque based on the output, 4 is a damping that calculates a damping current based on, for example, a rotational angular velocity ωM of the motor 8 calculated by a motor angular velocity calculating means (not shown). The controller 5 includes a friction compensation controller 5a that calculates a friction compensation current that compensates the friction torque of the motor 8, and an inertia compensation controller 5b that calculates an inertia compensation current that compensates the inertia moment of the motor 8. The friction compensation current is calculated based on ωM, and the inertia compensation is performed based on the rotational angular acceleration (dωM / dt) obtained by differentiating ωM. A compensation controller 6 for calculating a compensation current, 6 is an auxiliary torque current calculated by the torque controller 3, a damping current calculated by the damping controller 4, a friction compensation current and an inertia compensation current calculated by the compensation controller 5. Is an adder that calculates the target current. Reference numeral 7 denotes a current for controlling the target current calculated by the adder 6 and the drive current of the motor 8 output from the current detector 9 so that the drive current matches the target current. It is a controller.

Next, the operation of the conventional electric power steering control device will be described.
When the driver of the automobile steers the steering wheel, the steering torque at that time is measured by the torque sensor 1, phase-compensated by the phase compensator 2 and improved in frequency characteristics, and then input to the torque controller 3. The torque controller 3 calculates an auxiliary torque current that is substantially proportional to the output signal of the torque sensor 1 with improved frequency characteristics, and drives the motor 8 based on the auxiliary torque current to assist the driver's steering torque. , Reduce the steering torque by the driver.
At this time, in order to stabilize the movement of the steering wheel, the damping controller 4 calculates a damping current proportional to the motor rotational angular speed ωM and adds it to the auxiliary torque current. Further, in order to compensate for the influence of the friction of the motor 8, a friction compensation current that changes according to the sign of the motor rotational angular velocity ωM is added by the friction compensation controller 5a, and further, the influence of the moment of inertia of the motor 8 is compensated. The inertia compensation current proportional to the motor rotation angular acceleration (dωM / dt) obtained by differentiating the motor rotation angular velocity ωM by the inertia compensation controller 5b is applied. These compensation currents are added to the auxiliary torque current to calculate a target current, and the current controller 7 controls the drive current to be supplied to the motor 8 based on the target current, thereby being proportional to the drive current. The assist torque can be generated to reduce the steering torque by the driver and to stabilize the movement of the steering wheel. Each of the controllers 3, 4 and 5 changes the control parameter according to the vehicle speed.
Mitsubishi Electric Technical Review Vol.70 No.9 P43 ~ P48

By the way, the auxiliary torque current calculated by the torque controller 3 becomes a value approximately proportional to the output signal of the torque sensor 1 whose frequency characteristics are improved by the phase compensator 2. At this time, the torque controller 3 As the set torque proportional gain increases, the assist torque increases and the driver's steering torque can be reduced. However, if the torque proportional gain is increased, the control system oscillates and the driver feels uncomfortable torque vibration. Therefore, the torque proportional gain cannot be simply increased.
As a method of preventing the oscillation, a method of increasing the damping current can be considered. However, in the conventional technique, when compensation is performed to increase the damping current, this damping compensation acts as a resistance when turning the handle. Since the steering torque is increased, a large damping current cannot be applied. Therefore, there is a problem that the torque proportional gain cannot be increased and the steering torque of the driver cannot be sufficiently reduced particularly when a large assist torque such as a stationary stop is required.
Further, in order to obtain the rotational angular velocity ωM of the motor 8 with high accuracy, an expensive motor rotational speed sensor is required. Therefore, unlike the conventional electric power steering control device, the motor rotational speed sensor is not used. There is also a method of estimating the motor rotation speed from the motor applied voltage and motor current, and using the estimated value of the motor rotation speed to obtain the damping current, friction compensation current, and inertia compensation current. It has been difficult to accurately estimate the motor rotation speed at the frequency at which it is desired to take effect.

  The present invention has been made to solve the above-described problems, and can reduce the steering torque without causing the driver to feel uncomfortable torque vibration, and can reduce the cost. An object is to provide a steering control device.

According to a first aspect of the present gun includes a steering torque detecting means for detecting a steering torque by the driver, torque control for computing an assist torque current for assisting the steering torque based on the detected steering torque signal A motor that generates torque for assisting the steering torque, a rotational speed estimating means that estimates the rotational speed of the motor, and a steering component removal that removes a steering frequency component from the estimated value of the estimated motor rotational speed And a damping controller that calculates a damping current to be added to the auxiliary torque current using a signal obtained by removing the steering frequency component from the estimated value of the motor rotation speed output from the steering component removing means. the electric power steering control system, the rotation speed estimation means, the detection value or instruction value current supplied to the upper SL motor Fi And inverse characteristics calculating means for calculating a voltage drop equivalent value in the coil in the motor and data processing, the voltage drop from the measured value or command value of the voltage between the terminals of the motor, in the coil obtained by the inverse characteristics calculating means Back electromotive force estimating means for estimating the back electromotive voltage of the motor obtained by subtracting the equivalent value, and rotational speed estimated value calculating means for calculating the estimated value of the motor rotational speed based on the estimated back electromotive voltage. The reverse characteristic calculation means uses a filter having a frequency characteristic such that the reverse characteristic of the impedance including the inductance characteristic of the coil matches the gain and phase in a frequency band in which steering oscillation is likely to occur during steering. The detection value or command value of the current supplied to the motor is filtered .

  According to a second aspect of the present invention, in the electric power steering control device according to the first aspect, the vehicle speed detecting means is provided, and the frequency band removed by the steering component removing means is made variable according to the vehicle speed. It is. At this time, it is desirable that each parameter of the control system is also variable according to the vehicle speed.

According to the present invention, the steering torque detecting means, the torque controller for calculating the auxiliary torque current for assisting the steering torque based on the steering torque signal detected by the steering torque detecting means, and the steering torque are assisted. A motor that generates torque, a rotational speed estimating means that estimates the rotational speed of the motor, a steering component removing means that removes a steering frequency component from the estimated motor rotational speed, and output from the steering component removing means In an electric power steering control device comprising a damping controller for calculating a damping current to be added to the auxiliary torque current using a signal obtained by removing a steering frequency component from an estimated value of a motor rotational speed, a rotational speed detecting means and it is calculated by the detected value or a command value of the motor current from the measured value or command value of the voltage between the terminals of the motors Estimate the back electromotive force of the motor by subtracting the value equivalent to the voltage drop at the coil in the motor and configure the motor speed estimation value from the estimated back electromotive voltage. Even if the damping current is increased as the gain is improved, the damping current does not act as a steering torque resistance, and therefore the steering torque is reduced without the driver feeling the steering wheel vibration. Can do. In addition, since an expensive motor rotation speed sensor is not required, the cost of the electric power steering apparatus can be reduced.

At this time, a voltage drop equivalent value in the coil, steering oscillation in likely frequency band generated at the time of steering, using a filter that have a frequency characteristic including inductance characteristics of the coil, the current applied to the motor If the detection value or command value is filtered and calculated by the inverse characteristic calculation means for obtaining the voltage drop equivalent value in the coil in the motor, the voltage drop equivalent value in the coil can be obtained up to a higher frequency band. In addition to the frequency at which steering oscillation occurs, the gain and phase of the filter can be changed freely, so that the motor rotation speed at the frequency at which damping is desired can be accurately estimated, and the influence of noise at high frequencies Can be reduced.

  Further, since the vehicle speed detection means is provided and the frequency band to be removed by each of the steering component removal means is variable according to the vehicle speed, it is optimal for the steering frequency range and the frequency region where steering oscillation is likely to occur according to the vehicle speed. Control can be performed.

Hereinafter, the best mode of the present invention will be described with reference to the drawings.
Best Mode
FIG. 1 is a block diagram showing a configuration of an electric power steering control device according to the best mode 1 of the present invention. In the figure, 1 is a torque sensor that detects steering torque when the driver steers, 2 is a phase compensator that improves the frequency characteristics of the output signal of the torque sensor 1 by phase compensation, and 3 is phase compensated. A torque controller 11 for calculating an auxiliary torque current for assisting the steering torque based on the output of the torque sensor 1, for example, frequency-separating a motor rotation speed signal output from a motor rotation speed sensor 10 such as a tachometer; A rotational speed high-pass filter (hereinafter referred to as rotational speed HPF), which is a steering component removing means for removing the steering frequency component from the motor rotational speed signal, 4 controls the steering attenuation characteristic based on the output of the rotational speed HPF 11. Damping controller for calculating damping current, 6 is auxiliary torque current calculated by torque controller 3, and damping An adder for calculating the sum to the target current and the damping current computed by the control vessel 4. Reference numeral 7 denotes a current controller, which is applied to a terminal of the motor 8 so that a drive current detection value supplied to the motor 8 detected by the current detector 9 matches the target current in order to generate assist torque. A drive voltage command value to be set is set and output as, for example, a PWM signal.
In the present invention, even if the target current calculation means 20 including the phase compensator 2 and the rotational speed HPF 11 surrounded by the one-dot chain line in the block diagram of FIG. It is possible to solve. Below, the case where the said target current calculating means 20 is comprised only with the software of a microcomputer is demonstrated. The target current calculation means 20 has a memory such as a RAM or a ROM (not shown) common to each component or common to each component, and the detected value of the torque sensor 1 and the like at every predetermined control sampling time. Data is taken in, A / D converted, and stored in a data writing memory such as a RAM.

Here, the rotational speed HPF11 which is the steering component removing means will be described.
In general, the frequency at which the driver can steer is about 3 Hz or less. Further, for example, the steering frequency at the time of lane change is around 0.2 Hz, and usually such low frequency steering is often performed. On the other hand, the frequency band in which steering oscillation is likely to occur is 30 Hz or more, and frequency separation from the steering frequency is possible. Therefore, the steering component removing means is constituted by a frequency separator that frequency-separates the estimated or measured motor rotation speed and removes the steering frequency component from the motor rotation speed, thereby removing the steering component of the motor rotation speed. Can do.
In general, when a low frequency component is desired to be removed, a high pass filter is used as a frequency separator. By passing the rotational speed of the motor 8 output from the motor rotational speed sensor 10 through a high-pass filter, it is possible to remove a component due to steering, which is a low-frequency component. At this time, if the corner frequency of the high-pass filter is set low, the steering component tends to remain, and if it is set high, the phase shift of the steering oscillation component of the motor rotation speed obtained through the high-pass filter increases. If the corner frequency of the high-pass filter is set to any frequency within the range of the steering frequency from the steering frequency that is generated, it is possible to remove the steering frequency component while leaving the steering oscillation component of the motor rotation speed It is. Therefore, in the best mode 1, a high-pass filter with a break frequency set in the range of 0.2 to 30 Hz is used as the rotation speed HPF11 with the aim of the maximum frequency that can be steered by a general driver. The speed component is appropriately removed.

Next, the operation of the electric power steering control apparatus having the above configuration will be described based on the flowchart of FIG. The difference from the prior art of the present invention is the calculation method of the target current output to the current controller 7, that is, the algorithm until the target current is calculated by the target current calculation means 20 of FIG. As for the control of the drive current energized in FIG. 8, the commonly performed control such as PID type current F / B control or open loop control based on the target current and the motor rotation signal is either digital control or analog control. You may implement based on this system. Therefore, the following description will be limited to the algorithm until the target current calculation means 20 calculates the target current of the motor 8.
First, in step S101, the torque sensor output from the torque sensor 1 is read into the microcomputer and stored in the memory, and in step S102, the motor rotation speed signal from the motor rotation speed sensor 10 is read and stored in the memory. Next, in step S103, the phase compensator 2 reads the torque sensor output stored in the memory, performs phase compensation calculation, and stores it in the memory as the phase compensator output. In step S104, the torque controller 3 reads the phase compensator output stored in the memory, maps the auxiliary torque current, and stores it in the memory.
In step S105, the rotational speed HPF11 reads the motor rotational speed signal stored in the memory, performs a high-pass filter operation, and stores it in the memory as the rotational speed HPF output. In step S106, the damping controller 4 causes the memory to The rotation speed HPF output stored in is read, the control gain is multiplied, and the damping current is calculated and stored in the memory.
In step S107, the adder 6 adds the auxiliary torque current and the damping current stored in the memory and stores them in the memory as a target current.
The operations from step S101 to step S107 are repeated for each control sampling, and the target current of the motor 8 is calculated from the phase compensated torque sensor output and the motor rotational speed signal from which the steering frequency component has been removed.
A map indicating the relationship between the torque sensor output used in step S104 and the auxiliary torque current, and a map necessary for calculating a target current such as a control gain for calculating the damping current used in step S106. And constants such as a proportional coefficient are set in the ROM in advance.

In the best mode 1, the auxiliary torque current is obtained by map calculation and the damping current is obtained by multiplying the gain. However, both the auxiliary torque current and the damping current are calculated by map calculation or gain. You may obtain | require by either of the calculation methods.
In the above example, the phase compensator 2 is configured digitally, but may be configured analog. Alternatively, the phase compensator 2 may be a multi-stage phase compensator combining analog and digital. In this case, the step S101 performs the operation of reading the output of the analog phase compensator that has compensated the phase of the output of the torque sensor 1, not the output of the torque sensor 1, and storing it in the memory. When 2 is composed only of analog, the calculation in step S103 is not necessary.
In the above example, the motor rotation speed sensor 10 such as a tachogenerator is used to detect the motor rotation speed. However, the motor rotation angle signal is detected using a rotary encoder, for example, and the motor rotation angle signal is subjected to differential processing. Then, the motor rotation speed may be obtained.

  Furthermore, in the best mode 1, the target current is obtained from the output of the torque controller 3 and the output of the damping controller 4. However, as in the conventional example, the friction compensation controller 5a and the inertia compensation controller 5b It goes without saying that a configuration may be adopted in which the compensation controller 5 having the above is added, and the target current is obtained by further adding the friction compensation controller output and the inertia compensation controller output.

  Thus, in the best mode 1, after the steering frequency component is removed from the motor rotation speed signal detected by the motor rotation speed sensor 10 using the rotation speed HPF 11, the damping controller 4 determines the steering frequency component. Since the damping current is calculated based on the removed rotational speed HPF output, oscillation of the control system can be prevented even if the torque proportional gain is increased. Accordingly, since the damping gain can be applied more effectively by increasing the control gain (torque proportional gain) of the damping controller 4, the steering torque can be reduced without the driver feeling the steering wheel vibration.

Best Mode 2
FIG. 3 is a block diagram showing the configuration of the electric power steering control apparatus according to the best mode 2 of the present invention. In the best mode 1, the rotational speed HPF 11 is provided, and the damping current is calculated based on the rotational speed HPF output obtained by removing the steering frequency component from the motor rotational speed signal from the motor rotational speed sensor 10. 3, the motor rotation speed sensor 10 is omitted, and the inter-terminal voltage detector 12 for detecting the inter-terminal voltage of the motor 8 and the inter-terminal voltage detector 12 are detected as shown in FIG. A rotational speed estimator 13 which is rotational speed estimation means for estimating the rotational speed of the motor 8 based on the detected voltage between the terminals and the detected drive current value detected by the current detector 9 is provided to determine the motor rotational speed. In addition, the motor rotational speed estimation signal output from the rotational speed estimator 13 is input to the rotational speed HPF 11 and the steering speed is calculated from the motor rotational speed estimation signal. And configured to remove a few components, the damping controller 4, and which is adapted to calculate a damping current based on the rotation speed HPF output which is removal of the steering frequency component.

Next, the operation of the electric power steering control apparatus having the above configuration will be described based on the flowchart of FIG. The best mode 2 will be described by limiting to the algorithm until the target current is calculated by the target current calculation means 20 as in the case of the best mode 1.
First, in step S201, the torque sensor output from the torque sensor 1 is read and stored in the memory, the drive current detection value from the current detector 9 is read in step S202, and the terminal from the inter-terminal voltage detector 12 is read in step S203. The inter-voltage detection value is read and stored in the memory. In step S204, the phase compensator 2 reads the torque sensor output stored in the memory, performs phase compensation calculation, and stores it in the memory as the phase compensator output. In step S205, the torque controller 3 reads the phase compensator output stored in the memory, maps the auxiliary torque current, and stores it in the memory.
In step S206, the rotational speed estimator 13 reads the drive current detection value (Isns) and the inter-terminal voltage detection value (Vt_sns) stored in the memory, and calculates the motor rotation speed estimation signal ( ωest_bk) is calculated and stored in the memory.
ωest_bk = (Vt_sns−Vcomp−Isns × Rac) / Kec (1)
In the above formula (1), Vcomp is a compensation value corresponding to the voltage drop Vdrop of the applied voltage Va to the coil with respect to the terminal voltage Vt of the motor 8, Rac is equivalent to the coil resistance, and Kec is equivalent to the back electromotive voltage constant. Value. The details of the calculation method of the motor rotation speed estimation signal ωest_bk will be described separately.
Next, in step S207, the motor speed estimation signal ωest_bk stored in the memory is read by the rotation speed HPF11 and a high-pass filter is calculated and stored in the memory as the rotation speed HPF output. In step S208, damping control is performed. The machine 4 reads the rotational speed HPF output stored in the memory and multiplies the control gain to calculate the damping current. In step S209, the adder 6 adds the auxiliary torque current and the damping current stored in the memory and stores them in the memory as a target current.
The operations from step S201 to step S209 are repeated for each control sampling, and the target current of the motor 8 is calculated from the phase compensated torque sensor output and the motor rotation speed estimation signal from which the steering frequency component has been removed.

Here, details of a method of calculating the motor rotation speed estimation signal ωest_bk will be described.
The back electromotive force Ve of the motor is represented by the product of a known back electromotive voltage constant Ke and the motor rotational speed ω, as shown in the following equation (2).
Ve = Ke · ω (2)
Therefore, by estimating the back electromotive force Ve of the motor, it is possible to obtain the motor rotation speed estimation signal ωest_bk in which the motor rotation speed ω is estimated from ω = Ve / Ke.
By the way, the back electromotive force Ve can be calculated from the voltage Va applied to the coil and the voltage drop Vc at the coil, as shown in the following equation (3).
Ve = Va−Vc (3)
Further, the magnitude of the voltage drop Vc in the coil is obtained from the known coil resistance value Ra, coil inductance value La, and motor current Ia by the following equation (4).
Vc = Ra · Ia + La · (dIa / dt) (4)
In the above equation (4), the second term on the right side represents the influence of the inductance, but the influence is small outside the high frequency region, and noise is present in the signal obtained by differentiating the current detection value. Since it is easy to superimpose, it is often seen that the voltage drop Vc in the coil is expressed ignoring the second term as shown in the following equation (5).
Vc ≒ Ra ・ Ia (5)
By the way, although the applied voltage Va to the coil cannot be directly measured, the relationship between the voltage Vt between the motor terminals and the applied voltage Va to the coil is expressed by the following equation (6). By grasping the characteristics of the voltage drop Vdrop up to this point, the value of the voltage Va applied to the coil can be estimated.
Va = Vt−Vdrop (6)
Therefore, the back electromotive force Ve of the motor is obtained from the equations (3), (5), (6):
Ve = Va−Vc≈Va−Ra · Ia
= Vt-Vdrop-Ra · Ia
Therefore, the motor rotation speed estimation signal ωest_bk corresponds to the terminal voltage detection value Vt_sns corresponding to the motor terminal voltage Vt, and the voltage drop Vdrop from the motor terminal voltage Vt to the applied voltage Va to the coil. The compensation value Vcomp, the drive current detection value Isns corresponding to the motor current Ia, the coil resistance equivalent value Rac corresponding to the coil resistance value Ra, and the counter electromotive voltage constant equivalent value Kec corresponding to the counter electromotive voltage constant Ke are used. Can be obtained.
The calculation formula (Equation (1)) of the motor rotation speed estimation signal ωest_bk is shown again below.
ωest_bk = (Vt_sns−Vcomp−Isns × Rac) / Kec (1)
The above equation (1) is a description of the physical formulas expressed by the above equations (2), (3) and (5), (6) on the software, and the parameters of Rac and Kec are preliminarily set. Store in ROM. Further, since the voltage drop Vdrop depends on the current value, the Vcomp is stored in advance in the ROM as a map for the drive current detection value Isns. When the Vdrop is sufficiently small, the compensation value Vcomp may be handled as 0.

  As described above, in the best mode 2, the rotation of the motor 8 is rotated based on the detected voltage Vt_sns between the terminals detected by the voltage detector 12 between the terminals and the detected drive current Isns detected by the current detector 9. A rotation speed estimator 13 for estimating the speed is provided to calculate a motor rotation speed estimation signal ωest_bk, and the motor rotation speed estimation signal ωest_bk is input to the rotation speed HPF 11 to remove the steering frequency component, based on the rotation speed HPF output. Thus, the damping current is calculated, so that the expensive motor rotation speed sensor 10 is unnecessary, and the cost of the electric power steering apparatus can be reduced.

Best Mode 3
FIG. 5 is a block diagram showing the configuration of the electric power steering control device according to the best mode 3 of the present invention. In the best mode 2, the motor rotational speed is estimated by the rotational speed estimator 13 that estimates the motor rotational speed from the detected voltage Vt_sns between the terminals of the motor and the detected drive current value Isns to obtain the motor rotational speed estimation signal ωest_bk. However, in the best mode 3, as shown in FIG. 5, the rotational speed estimator 13 for estimating the rotational speed of the motor 8 based on the target current from the current controller 7 and the terminal voltage command value. To calculate the motor rotation speed estimation signal ωest_bk, and input the motor rotation speed estimation signal ωest_bk to the rotation speed HPF11 to calculate the damping current based on the rotation speed HPF output from which the steering frequency component has been removed. ing. The target current and the inter-terminal voltage command value are set values set by the controller (current controller 7). Further, the target current from the current controller 7 is assumed to indicate a current value for energizing the motor 8.

Next, the operation of the electric power steering control device having the above-described configuration will be described based on the algorithm until the target current is calculated based on the flowchart of FIG.
First, in step S301, the torque sensor output is read and stored in the memory, and in step S302, the phase compensator 2 reads the torque sensor output stored in the memory and performs the phase compensation calculation, and stores it in the memory as the phase compensator output. Remember. In step S303, the torque controller 3 reads the phase compensator output stored in the memory, maps the auxiliary torque current, and stores it in the memory.
In step S304, the rotational speed estimator 13 calculates the drive current detection value Iref calculated by the adder 6 and stored in the memory, and the drive voltage command value Vt_ind calculated by the current controller 7 and stored in the memory. The motor rotation speed estimation signal ωest_bk is calculated by the following equation (7) and stored in the memory.
ωest_bk = (Vt_ind−Vcomp−Vcomp2−Iref × Rac) / Kec (7)
The Vcomp2 is a compensation value corresponding to a voltage drop (Vt_ind−Vt) from the drive voltage command value to the voltage between the terminals of the motor. Since the voltage drop depends on the current value, the Vcomp2 is As a map for the detected drive current value Isns, it is stored in the ROM in advance. Further, when the voltage drop from the drive voltage command value to the inter-terminal voltage is sufficiently small, Vcomp2 may be handled as 0.

Next, in step S305, the motor rotational speed estimation signal ωest_bk stored in the memory is read by the rotational speed HPF11, a high-pass filter operation is performed, and the rotational speed HPF output is stored in the memory. In step S306, the damping controller 4 reads the rotational speed HPF output stored in the memory, and multiplies the control gain to calculate the damping current. In step S307, the adder 6 adds the auxiliary torque current and the damping current stored in the memory and stores them in the memory as a target current.
The operations from step S301 to step S307 are repeated for each control sampling, and the target current of the motor 8 is calculated from the phase compensated torque sensor output and the motor rotational speed signal from which the steering frequency component has been removed.

  As described above, in the third embodiment, the rotational speed estimator 13 that estimates the motor rotational speed estimation signal ωest_bk from the drive voltage command value Vt_ind that is a set value set by the controller and the target current Iref is provided, and the rotational speed. Since the damping current is calculated based on the rotational speed HPF output that is the motor rotational speed estimation signal ωest_bk from which the steering frequency component is removed by the HPF 11, it is affected by noise when detecting the drive current, terminal voltage, and the like. The damping current can be obtained with high accuracy.

  In the best mode 3, the command value and the target value set by the controller (current controller 7) are used for the voltage applied to the motor and the current value to be energized. Also good.

Best Mode 4
Next, the best mode 4 of the present invention will be described.
In the best mode 4, only the calculation algorithm for calculating the motor rotation speed estimation signal (ωest_bk) in the rotation speed estimator 13 in the best mode 2 is changed, and the motor rotation speed estimation signal in consideration of the inductance characteristic of the coil. (Ωest_bk) is calculated so that the vibration frequency component of the rotational speed of the motor 8 can be accurately estimated even when steering vibration occurs at a high frequency. The configuration of the electric power steering control device according to the best mode 4 is the same as the block diagram shown in FIG.

Next, only the algorithm until the target current is calculated will be described with reference to the flowchart of FIG.
First, in step S401, the torque sensor output is read and stored in the memory, the drive current detection value is read in step S402, the inter-terminal voltage detection value is read in step S403, and each is stored in the memory. In step S404, the phase compensator 2 reads the torque sensor output stored in the memory, performs phase compensation calculation, and stores it in the memory as the phase compensator output. In step S405, the torque controller 3 reads the phase compensator output stored in the memory, maps the auxiliary torque current, and stores it in the memory.

Steps S406 and S407 represent operations in the rotational speed estimator 13. In step S406, the drive current detection value Isns and the inter-terminal voltage detection value Vt_sns stored in the memory are read, and the following equation (8) is obtained. As shown, the difference between the drive current detection value Isns (k) of the current sampling and the drive current detection value Isns (k-1) at the previous sampling is obtained, and the differential value (dIsns) of the drive current detection value (Isns) is obtained. Calculate.
dIsns (k) = {Isns (k) −Isns (k−1)} / Tsamp (8)
k: Control sampling count
Tsamp: Control sampling time Next, in step S407, using the reverse characteristic calculation means for obtaining the coil voltage corresponding to the reverse characteristic of the coil impedance from the coil current, the drive current detection value Isns and the above equation (8) are used. After obtaining the voltage drop Vc at the coil based on the obtained dIsns (k), the motor rotational speed estimation signal (ωest_bk) is calculated by the following equation (9) and stored in the memory.
ωest_bk = (Vt_sns−Vcomp−Isns × Rac−Lac × dIsns) / Kec (9)
Here, Lac is a value corresponding to the coil inductance, and −Lac × dIsns / Kec is a term relating to the inductance characteristic of the coil.

Next, in step S408, the motor rotational speed estimation signal ωest_bk stored in the memory is read by the rotational speed HPF11 and a high-pass filter is calculated and stored in the memory as the rotational speed HPF output. In step S409, the damping control is performed. The machine 4 reads the rotational speed HPF output stored in the memory and multiplies the control gain to calculate the damping current. In step S410, the adder 6 adds the auxiliary torque current and the damping current stored in the memory and stores them in the memory as a target current.
The operations from step S401 to step S410 are repeated for each control sampling, and the target current of the motor 8 is calculated from the phase compensated torque sensor output and the motor rotational speed estimation signal from which the steering frequency component has been removed.
The equation (9) for calculating the motor rotation speed estimation signal ωest_bk is a description of the physical equations (2) to (4) and (6) above on the software, and the coil inductance equivalent value. Lac is stored in advance in the ROM in the same manner as Rac and Kec.

  As described above, when the motor rotation speed is estimated by obtaining the voltage drop equivalent value in the coil from the detected voltage value between the terminals of the motor 8 and the detected drive current value, the best mode 4 Since the inductance characteristic is considered, the vibration frequency component of the rotational speed of the motor 8 can be accurately estimated even when the steering vibration is generated at a high frequency.

  In the best mode 4, the motor rotation speed estimation signal (ωest_bk) is calculated using the drive current detection value (Isns) and the inter-terminal voltage detection value (Vt_sns). In addition, the motor rotation speed estimation signal (ωest_bk) may be calculated using one or both of the voltage value applied to the motor 8 and the current value supplied to the motor 8 as a drive voltage command value and a target current.

Best Mode 5
Next, the best mode 5 of the present invention will be described.
In the best mode 5, only the calculation algorithm for calculating the motor rotation speed estimation signal (ωest_bk) in the rotation speed estimator 13 in the best mode 2 is changed, and the motor rotation speed is driven with the detected voltage value between the terminals of the motor 8. When estimating from the detected current value, the inductance characteristics of the coil are taken into account, the gain and phase of the inverse characteristic calculation means for obtaining the value equivalent to the voltage drop in the coil, the reverse characteristics of the coil impedance, and steering oscillation during steering Thus, the rotational speed of the motor is accurately estimated only at the frequency at which the steering vibration is generated. The configuration of the electric power steering control device of the best mode 5 is the same as the block diagram shown in FIG.

Hereinafter, only the algorithm until the target current is calculated will be described with reference to the flowchart of FIG.
First, in step S501, the torque sensor output is read and stored in the memory, the drive current detection value is read in step S502, the terminal voltage detection value is read in step S503, and each is stored in the memory. In step S504, the phase compensator 2 reads the torque sensor output stored in the memory, performs phase compensation calculation, and stores it in the memory as the phase compensator output. In step S505, the torque controller 3 reads the phase compensator output stored in the memory, maps the auxiliary torque current, and stores it in the memory.

Steps S506 and S507 represent operations in the rotation speed estimator 13. In step S506, the drive current detection value (Isns) and the inter-terminal voltage detection value (Vt_sns) stored in the memory are read, and the following (10) As shown in the equation, the drive current detection value (Isns) is filtered, and the voltage drop equivalent value Vc_est in the coil is calculated.
x (k + 1) = Isns (k) −Gcomp1 · {Isns (k) −x (k)} Vc_est (k)
= Gcomp3 · (x (k) + Gcomp2 · {Isns (k) −x (k)}) (10)
Here, Gcomp1, Gcomp2, and Gcomp3 are parameters of the filter, and are parameters when an analog filter corresponding to the transfer function G (s) of the following equation (11) is digitized and converted, and stored in the ROM in advance. . Further, x (k) is an intermediate state quantity when the voltage drop equivalent value Vc_est in the coil is obtained from the drive current detection value Isns. When k = 0, an initial value stored in advance in the ROM is read. Perform the operation with.
G (s) = Gcomp3 · {(Tcomp1 · S + 1) / (Tcomp2 · S + 1)} (11)
As shown in the Bode diagram of FIG. 9, the filter of the above equation (11) has parameters Tcomp 1, Tcomp 2, and the like so that the reverse characteristics, gain, and phase of the actual coil coincide with each other at the frequency at which steering vibration occurs. Set Gcomp3.
Next, in step S507, using Vc_est (k) obtained by the above equation (10), the motor rotational speed estimation signal ωest_bk is calculated by the following equation (12) and stored in the memory.
ωest_bk = (Vt_sns−Vcomp−Vc_est) / Kec (12)

Next, in step S508, the motor rotation speed estimation signal ωest_bk stored in the memory is read by the rotation speed HPF11, a high-pass filter operation is performed, and the rotation speed HPF output is stored in the memory. In step S509, the damping controller 4 reads the rotational speed HPF output stored in the memory, and multiplies the control gain to calculate the damping current. In step S510, the adder 6 adds the auxiliary torque current and the damping current stored in the memory and stores them in the memory as a target current.
The operations from step S501 to S510 are repeated every control sampling, and the target current of the motor 8 is calculated from the phase compensated torque sensor output and the motor rotation speed estimation signal from which the steering frequency component has been removed.

As described above, in the best mode 5, when estimating the motor rotation speed from the detected voltage value between the terminals of the motor 8 and the detected drive current value, the inductance characteristic of the coil is considered and the frequency at which the steering vibration is generated. Because it is configured to accurately estimate the rotational speed of the motor only, the gain in the high frequency region can be reduced as compared with the case where the rotational speed of the motor is estimated simply by calculating the reverse characteristic of the coil impedance . The influence of high frequency noise can be reduced.
In addition, the detection value or command value of the current supplied to the motor is set so that the reverse characteristics of the coil impedance and the gain and phase match only at the frequency at which steering oscillation occurs during steering. In other cases, the gain and phase of the filter can be freely changed, so that the motor rotation speed can be accurately estimated at the frequency at which damping is desired.

Best Mode
FIG. 10 is a block diagram showing the configuration of the electric power steering control device according to the best mode 6 of the present invention. In the figure, 1 is a torque sensor that detects steering torque when the driver steers, 2 is a phase compensator that improves the frequency characteristics of the output signal of the torque sensor, and 3 is the output of the phase compensated torque sensor 1. A torque controller 4 that calculates an auxiliary torque current based on the reference signal 4 is a damping controller, and inputs a motor rotation speed estimation signal detected by the motor rotation speed sensor 10 to a rotation speed high-pass filter (HPF) 11 to obtain a steering frequency component. The damping current is calculated based on the rotational speed HPF output from which is removed. Reference numeral 6 denotes an adder that adds the auxiliary torque current calculated by the torque controller 3 and the damping current calculated by the damping controller 4 to constitute a target current. Reference numeral 7 denotes a current controller, which is a drive that is applied to the motor terminal so that the detected drive current value detected by the current detector 9 with respect to the drive current supplied to the motor 8 to generate assist torque matches the target current. A voltage command value is set and output as, for example, a PWM signal. In the present best mode 6, the vehicle speed detection means 19 is further provided, and the parameters of the phase compensator 2, the torque controller 3, the rotational speed HPF 11, and the damping controller 4 are changed to the vehicle speed signal Vs from the vehicle speed detection means 19. It is configured to change accordingly.

This is because, in general, the steering frequency range performed by the driver differs depending on the vehicle speed, and the tire reaction force also changes. Accordingly, in accordance with this, the output of the torque sensor 1 compensated by the phase of the torque controller 3 and the auxiliary torque current This is to change the relationship. When the relationship between the output of the phase compensated torque sensor 1 and the auxiliary torque current changes, the frequency region in which steering oscillation easily occurs and the degree of ease of oscillation also change.
In the present best mode 6, by making these parameters variable with respect to the vehicle speed, it is possible to perform optimum control according to a steering frequency range that is generally performed by a different driver depending on the vehicle speed and a frequency region in which steering oscillation is likely to occur. become.

Next, regarding the operation of the best mode 6, an algorithm until the target current is calculated will be described based on the flowchart of FIG.
First, in step S801, the torque sensor output is read and stored in the memory, in step S802, the motor rotational speed estimation signal is read and stored in the memory, and in step S803, the vehicle speed signal is read and stored in the memory. Next, in step S804, parameters for determining the frequency characteristics of the phase compensator 2 are read from the map for the vehicle speed signal Vs, and in step S805, the torque sensor output stored in the memory is read to perform phase compensation calculation, and the phase compensator output. As a memory. In step S806, the torque controller 3 reads the phase compensated output of the torque sensor 1 and the auxiliary torque current from the two-dimensional map for the vehicle speed signal, and in step S807, the phase compensation stored in the memory. The instrument output is read, and the auxiliary torque current is calculated and stored in the memory. In step S808, a parameter for determining a frequency band to be removed by the rotational speed HPF11 is read from the map for the vehicle speed signal Vs from the map for the vehicle speed signal Vs, and in step S809, the motor rotational speed estimation signal stored in the memory is read to And the rotation speed HPF output is stored in the memory. In step S810, the damping controller 4 reads the control gain in the damping controller 4 from the map for the vehicle speed signal, and in step S811, the rotational speed HPF output stored in the memory is read and multiplied by the control gain. Is calculated. In step S812, the adder 6 adds the auxiliary torque current and the damping current stored in the memory, and stores them in the memory as a target current.
Steps S801 to S812 are repeated for each control sampling, and the target current of the motor 8 corresponding to the vehicle speed signal Vs is calculated from the phase compensated torque sensor output and the motor rotational speed estimation signal from which the steering frequency component has been removed. To do.

  As described above, in the sixth embodiment, the frequency band to be removed by each steering component removing unit is varied according to the vehicle speed signal Vs, and each parameter of the control system is also varied according to the vehicle speed signal Vs. Therefore, it is possible to perform optimal control according to the steering frequency range by the steering of the driver, which varies depending on the vehicle speed, and the frequency region in which steering oscillation is likely to occur.

  In the best mode 6, the example in which the control parameter is changed in accordance with the vehicle speed signal Vs with respect to the best mode 1 has been described. However, the electric power steering control device according to the best mode 2 to 5 described above. In contrast, the control parameter may be changed according to the vehicle speed signal Vs.

  As described above, according to the present invention, there is provided an electric power steering control device that can reduce steering torque without using an expensive motor rotation speed sensor and without causing the driver to feel uncomfortable torque vibration. Can be provided.

1 is a block diagram illustrating a configuration of an electric power steering control device according to a best mode 1 of the present invention. FIG. 3 is a flowchart showing an algorithm of the best mode 1; 6 is a block diagram showing a configuration of an electric power steering control device according to a best mode 2. FIG. It is a flowchart which shows the algorithm of the best form 2. FIG. 6 is a block diagram showing a configuration of an electric power steering control device according to best mode 3; It is a flowchart which shows the algorithm of the best form 3. It is a flowchart which shows the algorithm of the best form 4. It is a flowchart which shows the algorithm of the best form 5. It is a figure which shows the characteristic of the filter equivalent to the reverse characteristic of the coil used for the best form 5. FIG. FIG. 10 is a block diagram showing a configuration of an electric power steering control device according to a best mode 6; It is a flowchart which shows the algorithm of the best form 6. It is a block diagram which shows the structure of the conventional electric power steering control apparatus.

Explanation of symbols

1 Torque sensor 2 Phase compensator 3 Torque controller 4 Damping controller
5 Compensation controller, 5a Friction compensation controller, 5b Inertia compensation controller,
6 Adder, 7 Current controller, 8 Motor, 9 Current detector,
10 motor rotation speed sensor, 11 rotation speed HPF, 12 voltage detector between terminals,
13 Rotational speed estimator, 19 Vehicle speed detecting means, 20 Target current calculating means.

Claims (2)

Steering torque detecting means for detecting steering torque by the driver, a torque controller for calculating an auxiliary torque current for assisting the steering torque based on the detected steering torque signal, and generating torque for assisting the steering torque Output from the motor, the rotational speed estimating means for estimating the rotational speed of the motor, the steering component removing means for removing the steering frequency component from the estimated value of the estimated motor rotational speed, and the steering component removing means An electric power steering control device comprising: a damping controller that calculates a damping current to be added to the auxiliary torque current using a signal obtained by removing a steering frequency component from an estimated value of a motor rotation speed, wherein the rotation speed estimating means, a detected value or an instruction value of current supplied to the upper SL motor by filtering with a coil in the motor And inverse characteristics calculating means for calculating a voltage drop equivalent value from the measured value or command value of the voltage between the terminals of the motor, opposite the motor obtained by subtracting a voltage drop equivalent value in the coil obtained by the inverse characteristics calculating means a counter electromotive voltage estimation means for estimating the electromotive voltage, a rotational speed estimation value calculating means for calculating the estimated value of the motor rotational speed based on the estimated counter electromotive voltage, the reverse characteristics computing means steering In a frequency band where steering oscillation is likely to occur, the detected value of the current supplied to the motor using a filter having a frequency characteristic such that the gain and phase match the reverse characteristic of the impedance including the inductance characteristic of the coil. Alternatively , the electric power steering control device is characterized by filtering the command value .   2. The electric power steering control device according to claim 1, further comprising a vehicle speed detecting means, wherein the frequency band removed by the steering component removing means is variable according to the vehicle speed.

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