JP4776656B2 - 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.

  The electric power steering device is arranged such that the steering torque generated by the driver rotating the steering wheel is detected by the steering torque detecting means, and the current corresponding to the detected torque is meshed with the mechanism of the steering device. By applying the electric motor to the electric motor, the electric motor is rotationally driven, and assist torque necessary for assisting the steering torque by the driver is generated to assist the steering force.

  On the other hand, tire vibration caused by wheel balance deviation called shimmy and tire vibration caused by eccentricity of the brake rotor called brake judder are transmitted to the steering wheel via the steering mechanism and deteriorates the steering operability, which is inconvenient for the driver. It is known to give pleasure.

As a method for suppressing this unpleasant feeling, for example, Patent Document 1 discloses that the equivalent inertia of the steering shaft determined by the motor inertia and the reduction gear is set to 4x10 ^-2 kg · m ² or more and 10x10 ^-2 kg · m ² or less. A method of canceling disturbance torque input from a tire with a sense of inertia is disclosed.

  In addition, a technique for suppressing disturbance by controlling a motor instead of mechanically suppressing disturbance is also disclosed. For example, Patent Document 2 discloses a method in which disturbance torque is canceled by obtaining a change acceleration of a motor current and multiplying the change acceleration of the motor current by a predetermined gain. In addition to this, for example, Patent Document 3 discloses a method of canceling disturbance torque by advancing the phase of a steering torque signal of 10 Hz or higher.

Japanese Patent Laid-Open No. 2003-40120 JP 2003-267251 A JP 2006-137341 A

  However, the method shown in Patent Document 1 suppresses vibration with a large motor inertia, and when the inertia increases, the resonance frequency of the steering mechanism decreases. Therefore, in some cases, up to the frequency band of road information that is a disturbance to be transmitted. However, there is a problem that it is difficult to realize an electric power steering system that is easy to grasp the road surface condition.

  In addition, in the method disclosed in Patent Document 2, it is necessary to calculate the change acceleration of the motor current. Generally, however, electric noise is mixed in the current value, and the second derivative is differentiated like the change acceleration. In order to do this, there is a problem that it is necessary to use a microprocessor having high noise processing resistance and high processing power.

  In the method disclosed in Patent Document 3, a torque sensor signal for detecting torque is used. Generally, since the torque sensor detects torsion between the steering wheel and the steering shaft, the steering wheel is also caused by disturbance torque. There is a problem that an accurate disturbance torque signal cannot be obtained under a vibrating condition.

  The present invention was made to solve the above-mentioned problems, and by performing vibration suppression control based on the dynamics of the steering system only in the frequency band of steering vibration generated by the vehicle structure such as Shimmy, It is an object of the present invention to provide an electric power steering control device that can suppress steering vibration without affecting the feeling and without adding new mechanical parts.

The electric power steering control device according to the present invention has a steering torque detecting means for detecting a steering torque of the steering mechanism by a driver, calculates an auxiliary torque current corresponding to the steering torque, and uses the electric motor to generate the steering mechanism. An electric power steering control device for assisting steering by giving an auxiliary torque to a vehicle, a vehicle speed detecting means for detecting a vehicle speed of the vehicle, and a gain of a steering vibration control current for suppressing steering vibration from the vehicle speed detected by the vehicle speed detecting means and gain MAP to set the motor rotation signal detecting means for computing a motor rotation signal based on at least one of the current signal flowing through the electric motor and the voltage between the terminals of the electric motor, detected by the motor rotation signal detecting means Frequency separation hand that removes steering frequency component from motor rotation signal A multiplier that multiplies the gain, which is the output of the gain MAP, and the output of the frequency separation means to output a steering vibration control current, and the steering vibration from the multiplier based on the vehicle speed detected by the vehicle speed detection means. A limiter for setting upper and lower limits of the control current, and the electric motor is driven by a target current obtained by adding the steering vibration control current from the limiter and the auxiliary torque current .

  The electric power steering control device according to the present invention is configured as described above, and includes a motor rotation signal detection means for detecting the rotation of the electric motor by a vehicle structure such as Shimmy, and a steering based on the output of the motor rotation signal detection means. Since it has a disturbance suppression means for calculating the steering vibration control current for suppressing the vibration, it is possible to accurately detect that the motor has been rotated by the disturbance torque and to suppress the steering vibration. The user's steering operability can be improved and discomfort can be suppressed.

  In addition, since the steering vibration current is calculated from the motor current and the voltage signal between the motor terminals, there is no need to perform advanced calculations such as differentiation of the signal itself, and steering vibration suppression can be achieved only by changing the software with the same configuration as before. It is possible. Further, since the steering vibration current is calculated from the motor current and the voltage signal between the motor terminals, accurate disturbance torque suppression control can be performed even under a situation where the steering wheel is also vibrated together by the disturbance torque.

  Also, by setting a gain map according to the torque sensor value, assist compensation control according to the steering state can be performed, so that a better steering feeling can be realized.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an algorithm of the electric power steering control apparatus according to the first embodiment, and is configured by software. In addition, since it is the structure similar to a well-known electric power steering apparatus about the hardware, the description is abbreviate | omitted.

  In FIG. 1, the steering torque when the driver steers is detected by the torque sensor 1, and the vehicle speed is detected by the vehicle speed detector 8 from the wheel speed sensor. Based on the steering torque detected by the torque sensor 1 and the vehicle speed detected by the vehicle speed detector 8, the target current calculation means 14 calculates the target current of the auxiliary torque current.

The target current calculation means 14 is composed of the following elements. That is, the steering vibration is suppressed from the vehicle speed detected by the vehicle speed detector 8 and the torque controller 2 such as an assist map compensator for calculating the auxiliary torque current for assisting the steering torque based on the output of the torque sensor 1. Gain MAP10 for setting the gain of steering vibration control current, and gain M
A multiplier 11 that multiplies a gain that is an output of the AP 10 and an output of a frequency separation unit 13 that will be described later to output a steering vibration control current, and a steering vibration control that suppresses steering vibration from the vehicle speed detected by the vehicle speed detector 8. A limiter 12 for setting upper and lower limit values of the current, an adder 3 for adding the output of the limiter 12 and the auxiliary torque current calculated by the torque controller 2 to output a target current, and a current of the motor 5 are detected. Motor rotation signal detection means 9 for calculating a motor rotation signal based on at least one of the output of the current detector 6 and the output of the inter-terminal voltage detector 7 for detecting the inter-terminal voltage of the motor 5, and a motor rotation signal detection Disturbance suppression means for calculating a steering vibration control current for suppressing steering vibration from the motor rotation signal detected by the means 9, specifically, the operation. And a frequency separating means 13 for removing frequency components.

  The current controller 4 is applied to the terminal of the motor 5 so that the drive current supplied to the motor 5 detected by the current detector 6 matches the target current output from the adder 3 of the target current calculation means 14. A drive voltage command value to be set is set and output as, for example, a PWM signal so that an appropriate assist torque is generated. In FIG. 1, the target current calculation means 14 is shown in a simplified manner in order to clarify the features of the present invention. However, as an electric power steering control device, in general, a damping compensation for controlling the convergence of the vehicle, It goes without saying that various compensation control elements such as inertia compensation for reducing the inertial feeling of the steering mechanism are added.

Next, the motor rotation signal detection means 9 of the target current calculation means 14 will be described in detail. The motor rotation signal is expressed by the following formula.

Where ω is the motor rotation signal, V _t is the voltage between the motor terminals, V _drop is the compensation value corresponding to the voltage drop from the drive voltage command value to the voltage between the motor terminals, and has a property that depends on the current value. A map for the current value I _act is stored in advance in the memory of the microprocessor. dI _act is a differential signal of current value, R is a value corresponding to the coil resistance of the motor, L is a value corresponding to the coil inductance of the motor, and K _b is a constant corresponding to the counter electromotive voltage and is a constant stored in the memory of the microprocessor in advance.

  Note that even if the coil inductance L is ignored in the equation (1), the equivalent motor rotation signal can be detected, so the coil inductance L may be ignored.

Further, as will be described later, disturbance torque such as shimmy can be generally separated from the steering frequency. The current value I _act that assists the driver's steering load is within the steering frequency range for many electric power steering systems, and in the case of high frequencies such as shimmy, the motor rotation signal is detected only from the voltage signal V _t between the motor terminals. Is also possible. Thus if only the voltage signal V _t between the motor terminals so as to obtain the motor rotation signal, it is possible to realize the functions in a simpler configuration.

  Next, the frequency separation means 13 as the disturbance suppression means will be described in detail. The frequency separation means 13 is provided to remove the steering frequency component from the motor rotation signal. In general, the steering frequency is 5 Hz or less, and frequency components higher than that can be regarded as disturbance torque.

For example, the frequency separation means 13 can be designed by designing a 10 Hz high-pass filter. However, since the steering vibration generated by the vehicle structure, such as Shimmy, varies depending on the vehicle, the break frequency of the high-pass filter may be designed so that the resonance frequency gain in which Shimmy is conspicuous falls between 5 and 20 Hz. Alternatively, at least one converter having a frequency characteristic corresponding to this may be provided.

  Steering vibrations generated by the structure of the vehicle are mainly caused by tire wheel balance deviation and brake rotor eccentricity. The steering vibration of these vehicles occurs when the wheel of the tire is rotating, and the magnitude thereof varies depending on the vehicle speed. In view of such a situation, it is possible to suppress steering vibration due to disturbance torque only in a necessary region by providing a gain setting and a limiter according to the vehicle speed.

  As a specific embodiment of the gain, it may be set so that the gain becomes the largest at the vehicle speed at which the resonance frequency at which shimmy occurs most. In addition, the gain should be set to 0 when the vehicle speed is 0 km / h or the like.

  As a specific embodiment of the limiter, the absolute value of the current may be set to 3 amperes or less, more preferably 2 amperes or less as the largest limiter at the vehicle speed at the resonance frequency where shimmy is most generated. The limiter should be set to 0 when the vehicle speed is 0 km / h or the like.

  By setting the gain and limiter according to the vehicle speed in this way, it is possible to perform disturbance suppression control according to the running state of the vehicle, and to reduce the uncomfortable feeling to the driver that performs control intervention at an unnecessary place. It is possible to accurately suppress vibrations such as shimmy by performing control intervention only at the location. Since the gain setting and the limiter have different setting values depending on the vehicle, it is necessary to change the numerical values according to the vehicle to which the present invention is applied.

  Next, the operation of the electric power steering control apparatus according to Embodiment 1 will be described using the flowchart of FIG. Note that the operation of the first embodiment is different from the prior art in that the motor inertia is not increased to suppress shimmy vibration mechanically, but vibration is generated by a steering vibration suppression current calculated based on the motor rotation signal. The control algorithm is a control algorithm for controlling the drive current to be supplied to the motor 5, such as PID current feedback control or open loop control based on the target current and the motor rotation signal. You may implement in any system of analog control. Therefore, the following description will be limited to the algorithm of the steering vibration suppression current calculation unit in the target current calculation unit 14.

First, in step S101, the motor current generated in the motor 5 is detected by the current detector 6, and the motor current signal is read into the microcomputer and stored in the memory. In step S102, the motor terminal voltage generated in the motor 5 is detected by the terminal voltage detector 7, and the motor terminal voltage signal is read into the microcomputer and stored in the memory. In step S103, the vehicle speed signal from the vehicle speed detector 8 is read into the microcomputer and stored in the memory.
In step S104, a motor rotation signal is calculated by the motor rotation signal detection means 9 from the motor current signal and the voltage signal between the motor terminals, and stored in the memory.

In S105, as described above, the frequency separation means 13 using means such as a high-pass filter calculates a frequency characteristic signal that blocks the steering frequency component from the motor rotation signal and suppresses disturbance torque, and stores it in the memory. In S106, the vehicle speed signal is read, and the steering vibration suppression current gain is read from the gain MAP predetermined by the vehicle and stored in the memory. In S107, the multiplier 11 multiplies the output signal of the frequency separation means 13 and the steering vibration suppression current gain to calculate the steering vibration suppression current, and the limiter 12 determines the upper and lower limit values according to the vehicle speed determined in advance by the vehicle. Clip the current. In S108, the steering vibration suppression current is added to the auxiliary torque current calculated by the torque controller 2 by the adder 3 to obtain a target current.

  As described above, in the first embodiment, steering vibration is suppressed based on the motor current and the voltage between the motor terminals. Therefore, unpleasant steering vibration can be reduced without adding new mechanism parts.

  In addition, since the steering vibration current is calculated from the motor current and the voltage signal between the motor terminals, there is no need to perform advanced calculations such as differentiation of the signal itself, and steering vibration suppression can be achieved just by changing the software with the same configuration as before. Is possible. Further, since the steering vibration current is calculated from the motor current and the voltage signal between the motor terminals, accurate disturbance torque suppression control can be performed even under a situation where the steering wheel is also vibrated together by the disturbance torque.

  In the first embodiment, only the example in which the high-pass filter is used in the frequency separation means 13 has been described. However, even if a low-pass filter or the like is used for phase adjustment for high-frequency noise removal or steering vibration suppression, the same effect can be obtained. It is possible to obtain.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing an algorithm of the electric power steering control apparatus according to the second embodiment, which is configured by software. In this figure, the same or corresponding parts as in FIG. The difference from FIG. 1 is that the output of the multiplier 11 is multiplied by a gain corresponding to the torque sensor input.

  3, reference numeral 31 denotes a gain MAP for setting a gain of a steering vibration control current for suppressing the steering signal from the torque sensor signal detected by the torque sensor 1, and 32 denotes a steering torque which is an output of the gain MAP 31 to an output of the multiplier 11. It is a multiplier that multiplies the gain according to.

  As described above, the electric power steering control device has various compensation elements such as assist map compensation. In general, a sufficient assist torque is generated in a region where the steering torque is large. As a result, the steering vibration is hardly transmitted to the driver, and the influence on the steering feeling is small. The steering vibration such as shimmy makes the driver uncomfortable in a region where the steering torque is near neutral and the assist torque is small.

  Specifically, the value of the torque sensor signal may be set to a gain of 1 within 1 Nm and set to be smoothly attenuated to 0 from 1 Nm to 2 Nm. It should be noted that within 1 Nm is the dead band width of general assist map compensation. If the dead band width is 0.5 Nm, it may be set so that 0.5 Nm is set to gain 1 and attenuates to 0 over 2 Nm.

  By setting the gain MAP 31 according to the torque sensor signal so that the steering vibration suppression current acts as the steering torque is near the neutral position, it becomes possible to apply the steering vibration suppression current only in the necessary region, and the steering state By performing compensation control according to the above, better steering feeling can be realized.

It is a block diagram which shows the algorithm of the electric power steering control apparatus by Embodiment 1 of this invention. 3 is a flowchart for explaining the operation of the first embodiment. It is a block diagram which shows the algorithm of the electric power steering control apparatus by Embodiment 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Torque sensor, 2 Torque controller, 3 Adder, 4 Current controller, 5 Motor, 6 Current detector, 7 Terminal voltage detector, 8 Vehicle speed detector, 9 Motor rotation signal detector, 10 Gain MAP, 11 Multiplier, 12 limiter, 13 frequency separation means, 14 target current calculation means, 31 gain MAP, 32 multiplier.

Claims (3)

Has a steering torque detecting means for detecting a steering torque of a steering mechanism by the driver, the steering and computing an assist torque current corresponding to the torque, the electric power steering assist by applying an auxiliary torque to the steering mechanism by an electric motor A steering control device for detecting a vehicle speed of the vehicle; a gain MAP for setting a gain of a steering vibration control current for suppressing steering vibration from the vehicle speed detected by the vehicle speed detection means; and the electric motor Motor rotation signal detection means for calculating a motor rotation signal based on at least one of a flowing current signal and a voltage between terminals of the electric motor, and a steering frequency component is removed from the motor rotation signal detected by the motor rotation signal detection means Frequency separation means for performing, and gain and output that are outputs of the gain MAP A multiplier that multiplies the output of the number separating means and outputs a steering vibration control current; and a limiter that sets an upper and lower limit value of the steering vibration control current from the multiplier according to the vehicle speed detected by the vehicle speed detecting means. And an electric power steering control device that drives the electric motor with a target current obtained by adding a steering vibration control current from the limiter and the auxiliary torque current . The steering frequency separation means for removing frequency components, according to claim 1, characterized in that it comprises a converter frequency characteristic corner frequency corresponds highpass filter or it is set to a range of 5~20Hz least one The electric power steering control device described. The electric power steering control device according to claim 1 or 2, wherein the steering vibration control current is determined based on the steering torque signal.

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