JP2007253670A - Control device for electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an electric power steering device which improves a following performance of steering wheel in a steering holding state or a high-speed steering state, and has a good steering feeling while maintaining a steering performance and a steering sound in a normal steering state. <P>SOLUTION: The control device for the electric power steering device is equipped with a motor for giving an steering auxiliary force to a steering system of a vehicle, a torque sensor for outputting a steering force acting on a steering wheel, a current command value determination means for determining the current value based on the steering torque value from the torque sensor, a current detection means for detecting a motor current, and a current control means for outputting the voltage command value based on the current command value and the motor current. The parameter of the current control means is corrected according to a state of the steering system. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an electric power steering device, and in particular, improves the follow-up performance of a steering wheel during high-speed steering (rapid steering, high-speed steering), and maintains steering performance and steering sound in a normal steering state (during normal steering). The present invention relates to a control device for an electric power steering device with good steering feeling.

  An electric power steering apparatus that applies an assisting force (steering assisting force) to a steering apparatus of a vehicle by a rotational force of a motor is a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a speed reducer. An auxiliary force is given to the. A simple configuration of such an electric power steering apparatus will be described with reference to FIG. The column shaft 2 of the steering handle 1 is connected to a tie rod 6 of a steering wheel via a reduction gear 3, universal joints 4A and 4B, and a pinion rack mechanism 5. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque T of the steering handle 1, and a motor 20 that assists the steering force of the steering handle 1 is applied to the column shaft 2 via the reduction gear 3. It is connected.

  The motor 20 is controlled by the current I from the control unit 30, and the control unit 30 is supplied with electric power from the battery 14, and an ignition key signal is input from the ignition key 11. Further, the vehicle speed V is input to the control unit 30 from the vehicle speed sensor 12.

  Control of the electric power steering apparatus configured as described above will be described with reference to FIG.

  First, the steering torque T detected by the torque sensor 10 and the vehicle speed V detected by the vehicle speed sensor 12 are input to the assist map 311 in the current command value determination unit 310, and the assist map 311 is set to the steering torque T and the vehicle speed V. Based on this, a steering assist command value Ir is calculated and input to the adder 312. A compensation value calculation unit 313 is provided in the current command value determination unit 310. In the compensation value calculation unit 313, the convergence is calculated by a convergence calculation unit 313A, an inertia calculation unit 313B, and a SAT (self-aligning torque) 313C. The adders 314 and 315 add the compensation values for the inertia, inertia, and SAT, and add the addition result to the steering assist command value Ir by the adder 312 to determine the torque command value Tref. The torque command value Tref is input to the current command value calculation unit 316, and the current command value Iref is calculated by the current command value calculation unit 316 and input to the subtraction unit 301.

  When the motor 20 is a brushless motor, in addition to the torque command value Tref, the rotation angle of the rotor is also input to the current command value calculation unit 316 to calculate the current command value Iref.

  On the other hand, the motor current Im supplied to the motor 20 is detected by the current detector 304 and input to the subtraction unit 301 together with the current command value Iref from the current command value determination unit 310, and the deviation ΔI (= Iref) by the subtraction unit 301. -Im) is calculated. Deviation ΔI is input to a proportional-integral control unit in current control unit 320. In this example, it is input to the proportional term 321 that is the proportional gain Kp and the integral term 322 that is the integral gain Ki. The output of the proportional term 321 and the output of the integral term 322 are added by the adder 323 and output as a voltage command value Vref.

  The PWM control unit 302 receives the voltage command value Vref and outputs a PWM signal to the inverter 303, whereby a PWM signal based on the voltage command value Vref is input to the inverter 303. The inverter 303 supplies a motor current Im based on the PWM signal to the motor 20 to drive the motor 20.

  The above description is for the case where PI control is used for the current control unit 320, but the gain Gi related to proportional integration is expressed by the following equation (1).

つまり、偏差ΔＩが小さい値であってもゲインＧｉが無限大になるため、ハンドル保舵時やゆっくりした操舵時にも電圧指令値Ｖｒｅｆは大きな値として出力され、以下のような問題が発生する。

That is, even if the deviation ΔI is a small value, the gain Gi becomes infinite, so that the voltage command value Vref is output as a large value even during steering of the steering wheel or during slow steering, causing the following problems.

  In other words, recent electric power steering devices have a large capacity, that is, a large current, but the AD converter used in a control device mainly composed of a CPU, for example, has a resolution of 10 bits. However, the resolution is relatively coarse. The calculation error such as noise generated by the roughness of the resolution is amplified by the feedback gain that becomes infinite when the deviation ΔI at the time of steering or slow steering is small, and the vibration or noise of the steering wheel is increased. As a result, there is a problem that makes the driver feel uncomfortable.

  By the way, in the current control of the electric power steering apparatus, integral control (I control), proportional integral control (PI control) and proportional integral derivative control (PID control) are generally used. However, the current control including the integral term has an infinite gain in the steady state. Therefore, in the case of the steered state or the slow steering of the electric power steering device, the vibration and noise are controlled via the steering wheel. There is a problem that the steering wheel feels uncomfortable.

Therefore, in Japanese Patent Laid-Open No. 2000-108916 (Patent Document 1), in order to solve this problem, in feedback control, the deviation ΔI = Iref−Im between the current command value Iref and the actual motor current Im includes an integral term. An adjustment gain is provided before input to the current control system, and the adjustment gain is reduced when the deviation ΔI is small, and the adjustment gain is increased when the deviation ΔI is large.
JP 2000-108916 A

  However, in the above conventional electric power steering device, the design (threshold value) for determining the adjustment gain that changes according to the deviation of the current feedback is difficult, and the gain of the integral term is infinite. No matter how small, the total gain increases, and the problem of feeling vibration and noise that occurs during steering and slow steering has not been solved. In addition, there is a problem in which discrete time and fixed-point arithmetic, which are mounting problems, are not taken into consideration when the CPU is used as a control device for the electric power steering apparatus.

  Furthermore, the conventional current control unit responsiveness has been designed taking into account the steering noise during normal steering, steering noise, and noise caused by disturbances, so motor follow-up performance during sudden and high-speed steering Was insufficient.

  The present invention has been made under the circumstances described above, and an object of the present invention is to improve the steering performance of the steering wheel during high speed steering, and to improve the steering performance and steering sound during normal steering and medium / low speed steering. An object of the present invention is to provide a control device for an electric power steering device that maintains a good steering feeling while maintaining it.

  The present invention relates to a motor for applying a steering assist force to a steering system of a vehicle, a torque sensor for detecting a steering force acting on a steering wheel, and a current command for determining a current command value based on a steering torque value from the torque sensor. The present invention relates to a control device for an electric power steering apparatus comprising: a value determining means; a current detecting means for detecting a motor current; and a current control means for outputting a voltage command value based on the current command value and the motor current. The object is achieved by correcting the parameters of the current control means according to the state of the steering system.

  The object of the present invention is to increase the gain as a correction of the parameter and decrease the time constant in the case of high-speed steering, or to correct the parameter of the advance compensation and reduce the advance amount, or dead. By correcting the parameter of time compensation and reducing the phase delay of the feedback model, or when the steering torque value is larger than the steering torque predetermined value, increasing the gain and reducing the time constant as the correction of the parameter Alternatively, when the current command value is larger than the current command value predetermined value, the gain is increased as a correction of the parameter, the time constant is decreased, or when the rotational speed of the motor is larger than the predetermined rotational speed value, By increasing the gain and reducing the time constant as correction of the parameter, Results to be achieved.

  According to the control device for the electric power steering apparatus according to the present invention, the steering state is detected by using at least one of the steering torque T, the current command value Iref, the vehicle speed V, the motor angle θ, and the rotational angular velocity ω of the motor. The control gain (parameter) of the current control responsiveness is corrected according to the steered state, and the current control responsiveness parameter is corrected by determining the high-speed steering state. For this reason, the tracking performance of the steering wheel during high speed steering can be remarkably improved, and a better steering feeling can be obtained while maintaining the steering performance and steering sound during normal steering (medium / low speed).

  Further, in the present invention, the parameter for the advance angle compensation is corrected together with the parameter for the current control unit in the high speed steering state, and the parameter for the dead time compensation is corrected, so that the followability of the motor at the time of sudden turning or high speed turning is corrected. And the steering feeling can be maintained.

  In the electric power steering device of the present invention, the steering state is detected using at least one of the steering torque T, the current command value Iref, the vehicle speed V, the motor angle θ, and the rotational angular velocity ω of the motor, and the detected steering state is determined. In addition to correcting the parameters of the current control unit, the high-speed steering state is determined based on the steering torque T, the current command value Iref, the vehicle speed V, and the rotational angular velocity ω of the motor. Alternatively, the dead time compensation parameter is corrected.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an embodiment of the present invention corresponding to FIG. 16. In the present invention, a steering state detection unit 330 for detecting a steering state and a high speed state determination unit 340 for determining high speed steering are provided. The current control unit 320 includes a gradual change gain unit 324 that gradually changes the gain, and a current controller 325 having a transfer function (L · s + R) / (T · s + a) constituted by an advance / delay function. L is an inductance value of the motor 20, R is a resistance value of the motor 20, T is a time constant of the current controller 325, and a (> 0) is a constant.

  As shown in FIG. 1, the steering torque T detected by the torque sensor and the vehicle speed V detected by the vehicle speed sensor are input to the current command value determination unit 310 to determine the current command value Iref and the steering. The torque T and the vehicle speed V are input to the steering state detection unit 330 and the high speed steering determination unit 340. The current command value Iref determined by the current command value determination unit 310 is input to the subtraction unit 301 and also input to the steering state detection unit 330 and the high speed steering determination unit 340. The motor current Im of the motor 20 is detected by the current detector 304 and fed back to the subtractor 301, and a deviation ΔI (= Iref−Im) from the current command value Iref is calculated. In addition, a resolver (or hall sensor) 21 is attached to the motor 20 as a rotor position detection sensor, and the motor angle θ and the rotational angular velocity ω of the motor are detected and input to the steering state detection unit 330. The rotational angular velocity ω is Input to the high-speed steering determination unit 340.

  When the steered state is detected by the steering state detecting unit 330, the steered signal SS is output and input to the gradual gain unit 324 and the current controller 325 in the current control unit 320, and the high speed steering determining unit 340 performs the high speed operation. When the steering is determined, a high-speed steering signal HS is output and input to the gradual change gain unit 324 and the current controller 325 in the current control unit 320.

  The steering state detection unit 330 detects the steering state (open, increased switchback, and steering) using at least one of the steering torque T, the current command value Iref, the vehicle speed V, the motor angle θ, and the rotational angular velocity ω of the motor. The steering holding signal SS is output when the steering holding state is detected, and the steering holding signal SS is not output in the normal steering state. The detection of the steered state will be described later.

  The high-speed steering determination unit 340 determines high-speed steering based on the steering torque T, the current command value Iref, the vehicle speed V, and the rotational angular velocity ω of the motor, and outputs a high-speed steering signal HS when high-speed steering is detected. The high-speed steering determination unit 340 determines that the motor rotation speed based on the rotational angular velocity ω of the motor is equal to or higher than a predetermined value (threshold), and outputs a high-speed steering signal HS to output a current controller in the current control unit 320. The parameter of 325 is corrected. The motor speed is used for the determination of the high speed steering, but the steering torque T and the current command value Iref are also considered from the viewpoint of being based on the state of the power steering. For example, when high-speed steering is performed during normal asphalt running (including stoppage), the motor rotation speed, steering torque T, and current command value Iref are large, and follow-up performance is required, so parameters are corrected. In the case of a low friction road, the motor rotation speed is large, but the steering torque T and the current command value Iref are small. Therefore, emphasis is placed on the steering sound and steering performance rather than the tracking performance, and parameter correction is performed without determining high-speed rotation. Do not do. For example, when the vehicle speed condition requires a follow-up performance such as emergency avoidance at a vehicle speed V equal to or higher than a predetermined vehicle speed value (threshold), it is determined as high-speed turning and parameter correction is performed. Further, when the vehicle speed V is a low vehicle speed or a stop that is equal to or less than a predetermined vehicle speed value (threshold), the parameter is set as a normal control gain in order to emphasize steering performance and steering sound. That is, parameter correction based on the vehicle speed V is performed from the viewpoint of based on the state of the vehicle. Similarly, it is possible to consider the steering torque T and the current command value Iref.

  The deviation ΔI from the subtraction unit 301, the steering signal SS from the steering state detection unit 330, and the high speed steering signal HS from the high speed steering determination unit 340 are input to the gradual gain unit 324 in the current control unit 320, and the steering is maintained. The signal SS and the high-speed steering signal HS are input to the current controller 325, the deviation ΔIa gain-corrected by the gradual change gain unit 324 is input to the current controller 325 of the advance / delay function, and the voltage command value Vref from the current controller 325. Is output. The operation after the voltage command value Vref is the same as in FIG. That is, the PWM control unit 302 inputs the voltage command value Vref from the current control unit 320 and outputs a PWM signal to the inverter 303, so that the inverter 303 supplies the motor current Im to the motor 20 based on the PWM signal. Drive.

  FIG. 2 shows the time change of the steering state. When the steering holding signal SS from the steering state detection unit 330 is input to the gradual change gain unit 324, that is, when it is determined that the steering wheel is in the steering holding state ( At time t5 in FIG. 2, the gain G is gradually decreased to increase the time constant T of the current controller 325, thereby reducing the current control response to the current control response in the steered state (time t5 in FIG. 2). t6). In other words, the gain of the current control unit 320 (hereinafter, also simply referred to as “control gain”) is lowered from the normal steering state gain G1 to the steered state gain G2. Further, when the steering holding signal SS is not output from the steering state detection unit 330, that is, when it is determined that the steering wheel is in the normal steering state, the gain is gradually increased to reduce the time constant T of the current controller 325. As a result, the current control responsiveness is returned to the current control responsiveness in the normal steering state as shown at time points t7 to t8 in FIG. In other words, the control gain G of the current control unit 320 is increased from the steered state gain G2 to the normal steering state gain G1.

  When the control gain G is changed by detecting the normal steering state and the steered state in this way, the frequency characteristic of the current control response becomes as shown in FIG. 3, and the steering performance can be secured and maintained in the normal steered state. The rudder sound performance can be ensured in the rudder state.

  On the other hand, when the high-speed steering signal HS from the high-speed steering determination unit 340 is input to the gradual gain unit 324 and the current controller 325, that is, when it is determined that the steering operation is in the high-speed state (time t1 in FIG. 2). By increasing the control gain G of the current controller 320 and reducing the time constant T of the current controller 325, the current control response is increased to the current control response in the high speed steering state. In other words, the control gain G of the current control unit 320 is increased from the normal steering state gain G1 to the high speed state gain G3 (time points t1 to t2). Further, when the high-speed steering signal HS is not output from the high-speed steering determination unit 340, that is, when it is determined that the steering wheel is in the normal steering state (time point t3), by reducing the control gain of the current control unit 320, The current control response is returned to the current control response in the normal steering state. In other words, the control gain G of the current control unit 320 is lowered from the high speed state gain G3 to the normal steering state gain G1 (time points t3 to t4).

  When the control gain G is changed by detecting the normal steering state and the high-speed steering state in this way, the frequency characteristic of the current control response becomes as shown in FIG. Following performance can be ensured in the steering state. Further, the frequency characteristics (Bode diagrams) of the amplitude and phase in the normal steering state and the high speed steering state are as shown in FIGS. 5A and 5B, and the phase difference between the phase characteristics in the normal steering state and the high speed steering state. Therefore, it is necessary to switch the advance angle control.

  When the current controller 325 is configured by the advance / delay function (L · s + R) / (T · s + a), the steady-state (low frequency) gain decreases as shown in FIG. 3 and FIG. When the gain is decreased, the phenomenon further decreases, and the current decreases when the current is large. In order to prevent this, when switching the current control responsiveness, if it is determined that the steering wheel is in the steered state, the constant a is set to 0 or a small value as the gain of the gradual change gain unit 324 is gradually reduced. Gradually change. When it is determined that the steering wheel is in the normal steering state, the value of the constant a is gradually changed to the original value in accordance with the gradual change of the reduced gain to the original value. On the contrary, when it is determined that the steering wheel is in the high speed steering state, the constant a is gradually changed to a large value in accordance with the large change of the gain of the gradually changing gain unit 324. Further, when it is determined that the steering wheel is in the normal steering state, the value of the constant a is gradually changed to the original value in accordance with the gradual change of the increased gain to the original value.

Here, the steered state determination for detecting that the steered state is switched from the normal steered state to the steered state in the steering state detecting unit 330 will be described. For example, the following conditions (A1) to (A7) may be included in the holding state determination.
(A1) The differential value (time change amount) of the steering torque T is equal to or less than a predetermined value.
(A2) The steering torque T belongs to the predetermined value range. That is, T ₁ <T <T ₂ is satisfied.
(A3) This is a case where the vehicle speed V is equal to or lower than a predetermined value, for example, V ≦ 8 kph.
(A4) When there is no change in the motor angle θ, for example, as a motor angle sensor
This is a case where the duration of the Hall IC pattern is equal to or greater than 0.2 seconds.
(A5) The differential value of the motor angle θ is not more than a predetermined value.
(A6) The rotational angular velocity ω of the motor is not more than a predetermined value.
(A7) The current command value Iref is within a predetermined value range, and Iref ₁ <Iref <Iref _{2 is} satisfied.
For example, 2A <Iref <93A.

  Of the above conditions (A1) to (A7), several conditions are combined to obtain a logical product (AND condition), and when the result is “TRUE”, the steering state is switched from the normal steering state to the steered state. The steering holding signal SS is output.

  In cases other than the above conditions (A1) to (A7), or when the logical product is “FALSE”, it is determined that the steering steering state has returned to the normal steering state. For example, when the vehicle speed V is high, the current control responsiveness is always the current control responsiveness in the normal steering state in order to ensure the steering performance during traveling. Further, when the current command value Iref is small, the current control responsiveness is returned from the current control responsiveness in the steered state to the current control responsiveness in the normal steering state in order to ensure the steering performance near the steering wheel neutral position. Further, when the current command value Iref is large, when the constant a of the current controller 325 has some value, if the current control responsiveness is lowered, the control gain G is also lowered, and the output down in the region where the current is large is large. Therefore, the current control response is returned from the current control response in the steering holding state to the current control response in the normal steering state.

  On the other hand, the high speed steering determination unit 340 determines that the steering state has been switched from the normal steering state to the high speed steering state as follows. The high-speed steering determination unit 340 determines that the high-speed steering is performed when the motor rotation speed based on the rotation angular velocity ω of the motor is equal to or higher than a predetermined value (threshold), outputs a high-speed steering signal HS, and outputs the current in the current control unit 320. The parameter of the controller 325 is corrected. The motor rotation speed is used for the determination of the high speed steering, but from the viewpoint of being based on the state of the power steering, the determination is made in consideration of the steering torque T and the current command value Iref.

  As described above, in the control device for the electric power steering apparatus of the present invention, the current control responsiveness is changed by correcting the control gain (time constant T) of the current control unit in accordance with the steering state and the high speed steering of the steering wheel. I am doing so. That is, when it is determined that the steering wheel is in the steering holding state or the normal steering state, the control gain of the current control unit 320 is switched to a state having a small value as shown in FIG. The performance of not generating sound) can be improved. Further, when it is determined that the steering wheel is in the high speed steering state or the normal steering state, the control gain of the current control unit 320 is switched to a state having a large value, so that the follow-up performance can be improved.

  In the current control unit 320 of the above-described embodiment, the gradual gain unit 324 is provided before the current controller 325, but may be provided after the current controller 325 as shown in FIG. In the embodiment shown in FIG. 6, the current control unit 320 includes a current controller 325 and a gradual gain unit 326. The gradual gain unit 326 receives a deviation ΔIb from the current controller 325 and maintains it. A rudder signal SS and a high speed steering signal HS are input.

FIG. 7 is a circuit diagram showing a specific example of the current controller 325, and the time constant T of the current controller 325 can be changed using this circuit. In the current controller 325 to which the circuit of FIG. 7 is applied, if the intermediate variable W _n−1 of integration is calculated so that the output becomes constant before and after the change of the current control response, the current control response is changed suddenly. However, the output does not change suddenly. A specific example of the intermediate variable W _n-1 reset is expressed as follows.

よって、数３において、今回の出力ｙ_ｎに前回出力ｙ_ｎ−１を代入すれば、今回の出力ｙ_ｎが前回出力ｙ_ｎ−１に等しくなる。

Therefore, the number 3, by substituting the previous output _{y n-1} to the current output _{y n,} the current output _{y n} is equal to the previous output _{y n-1.}

  FIG. 8 is a diagram for explaining the principle of changing the current control response in the present invention. For example, in the current waveform as shown in FIG. 8, the current command value Iref is 10 A, and the current detection value Im is the current waveform shown in the figure. In the case of 10A, the deviation ΔI between the current command value Iref and the current detection value Im becomes a current waveform of 0A. The deviation ΔI is input to the current controller 325, the steering holding signal SS from the steering state detection unit 330 or the high speed steering signal HS from the high speed steering determination unit 340 is input to the gradual change gain unit 326, and from the gradual change gain unit 326. The voltage command value Vref obtained by increasing or decreasing the control gain is output. That is, when the steering holding signal SS is input from the steering state detection unit 330 to the gradual change gain unit 326, or when the high speed steering signal HS is input from the high speed steering determination unit 340 to the gradual change gain unit 326, the current control unit. The responsiveness of 320 is increased and the follow-up performance is improved. When the steering signal SS is input, the responsiveness is lowered, the vibration is reduced, and the steering noise is improved.

  By the way, as shown in FIG. 5B, since there is a phase difference between the frequency response in the normal steering state and the high speed steering state, it is necessary to switch the advance angle control. The advance angle control is a function that improves the performance by compensating for the delay of the motor current in the vector control by the advance angle, and the advance angle control portion is omitted in FIGS. 1 and 6. In other words, in vector control, it is necessary to generate a current command value that theoretically eliminates torque ripple, and in order to eliminate torque ripple, it is a condition that there is no delay in the motor current. The motor current is delayed from the current command value, and advance angle control is performed to compensate for the delay (for example, Japanese Patent Application Laid-Open Nos. 2003-189658 and 2005-199735). In the present invention, the parameters of the advance control unit are corrected in accordance with the determination of the normal steering state and the high-speed steering state, and the configuration will be described with reference to FIG. 9 corresponding to FIG.

  As shown in FIG. 9, the motor angle θ and the rotational angular velocity ω of the motor from the resolver 21 are input to the advance angle control unit 350, and the high speed steering signal HS from the high speed steering determination unit 340 is also input to the advance angle control unit 350. The motor angle θea advanced by the advance angle control unit 350 is input to a predetermined part of the vector control (for example, a 2 phase / 3 phase conversion unit (not shown) or a 3 phase / 2 phase conversion unit (not shown)). Is done.

The advance angle control unit 350 is configured as shown in FIG. 10, and the motor rotation angular velocity ω from the resolver 21 is advanced by the advance angle element 351, and the advance angle controlled rotation angular velocity ωa is added by the addition unit 352. It is added to the motor angle θ, and is output within the limiter 353 limited to within 0 to 360 degrees. The advance angle-controlled motor angle θea is used for vector calculation. As shown in FIG. 11, the advance element 351 is configured to output a linear function obtained by adding (or subtracting) the gain GA to the offset Os. Although FIG. 11 shows only the positive region, the negative region has point-symmetric characteristics, and the advance element 351 performs the calculation of the following equation (4).
(Equation 4)
ωa = ω · GA + sign (ω) · Os

In the present invention, the gain GA of the advance angle element 531 is switched between normal steering and high-speed steering. That is, when the high-speed steering signal HS is not input to the advance angle element 351, the solid line gain GA shown in FIG. 11 is used, and when the high-speed steering signal HS is input to the advance angle element 351, A broken line gain GB (<GA) shown in FIG. In this way, the rotational angular velocity ω is advanced according to the steering state and added to the angle θ, and the addition result is used when generating the current command value, so that the motor current delay amount is adapted to the steering state. It is possible to compensate, and torque ripple and operation noise can be reduced in the entire region.

  On the other hand, in the case of the two-phase motor 20, the PWM control unit 302 and the inverter 303 are an inverter unit composed of FET1 to FET4 that are switching drive elements and a gate control unit that controls each gate of the FET1 to FET4 as shown in FIG. It consists of and. The inverter part is composed of an upper and lower arm made up of FET1 and FET3 and an upper and lower arm made up of FET2 and FET4 to form an H bridge. A current control value Vref from the PWM control unit 302 is input to the conversion unit 3031 to the gate control unit, and timing signals D1 to D4 for driving the FET1 to FET4 are generated, and the gate drive circuits 3032a, 3032b, 3033a, and 3033b are generated. A gate signal that can be input to drive the gates of the FET1 to FET4 is generated. However, the timing signals 3 and D4 are not directly input to the gate drive circuits 3033a and 3033b, but are input to the dead time circuits 3034 and 3035, respectively. The reason for this is as follows.

  The upper and lower arms constituting the inverter unit, for example, FET1 and FET3 are alternately turned on / off, and similarly, FET2 and FET4 are alternately turned on / off. However, the FET is not an ideal switch and does not turn on / off instantaneously as instructed by the gate signal, requiring a turn-on time or a turn-off time. For this reason, when an instruction to turn on FET1 and an instruction to turn off FET3 are made at the same time, FET1 and FET3 are turned on at the same time and the upper and lower arms are short-circuited. Therefore, when an off signal is given to the gate drive circuit 3032a so that the FET1 and FET3 are not turned on at the same time, an on signal is not given immediately to the gate drive circuit 3033a, and the dead time circuit 3034 performs the dead time Δt. In this case, an ON signal is given to the gate drive circuit 3033a to prevent the upper and lower short circuits of the FET1 and FET3. The same applies to FET2 and FET4. Such dead time compensation solves the problem of torque shortage and torque ripple in the control of the electric power steering apparatus, but the conventional dead time compensation does not consider the steering state. That is, since the dead time compensation control system is designed with normal steering parameters, if the current controller time constant changes during high speed steering, the dead time compensation timing may be delayed and the steering feeling may deteriorate. Therefore, in the present invention, at the time of high speed steering, the dead time compensation control system is switched to high speed steering.

A configuration example of the dead time control system will be described with reference to FIG. 13. The current command value Iref from the current command value determination unit 310 is input to the high-speed steering determination unit 340 and also to the dead band characteristic unit (calculation unit) 343. Entered. The dead band characteristic from the dead band characteristic unit (calculation unit) 343 is input to the gain unit 345. The dead band characteristic unit (arithmetic unit) 343 outputs a dead time correction value DB having a dead band characteristic as shown in FIG. 14 with respect to the current command value Iref. In addition, a current model unit 341 that generates a model current IM based on the detected current of the motor or the current command value Iref is provided, and the polarity determination unit 342 determines the polarity of the model current with a characteristic with hysteresis. The model current IM is input from the current model unit 341 to the unit 342, and the current model unit 341 is changed based on the high speed steering signal HS from the high speed steering determination unit 340. The model current IM is obtained by converting the current command value Iref with the following transfer function (5) (for example, Japanese Patent Application No. 2003-310131).
(Equation 5)
MR (s) = 1 / (1 + Tc · s)
Here, Tc = 1 / (2π · fc), and fc is a cutoff frequency of the current control loop.

The first-order lag function of Equation 5 is a model of a current control loop in which a transfer function 1 / (R + s · L) indicating a motor is derived based on a current control unit 320, a PWM control unit 302, an inverter 303, and a current detector 304. It is a function.

  The actual motor current contains a lot of noise, which makes it difficult to determine the polarity in the vicinity of the zero current, but the current model unit 341 passes the first delay circuit based on the current command value Iref without noise. Therefore, the motor model current IM is generated and the polarity is determined based on the model current IM, so that the accuracy is high. When the high-speed steering determination unit 340 determines high-speed steering, the high-speed steering signal HS is input to the current model unit 341 and the gain unit 345, and the characteristic is switched to high-speed steering. The polarity sign (Pi) determined by the polarity determination unit 342 is input to the multiplication unit 344, multiplied by the gain-adjusted DBa from the gain unit 345, and output as a dead time correction value Δt.

It is a block block diagram which shows the Example of this invention. It is a time chart which shows the operation example of this invention. It is a frequency characteristic figure which shows the operation example (normal steering and a steering hold state) of this invention. It is a frequency characteristic figure which shows the operation example (normal steering and high-speed steering state) of this invention. It is a frequency characteristic (Board diagram) of the amplitude and phase of a normal steering state and a high-speed steering state. It is a block block diagram which shows the other Example of this invention. It is a block block diagram which shows the structural example of a current controller. It is a figure for demonstrating the change principle of electric current control responsiveness. It is a block block diagram which shows the Example of this invention which has an advance angle control part. It is a block diagram which shows the structural example of an advance angle control part. It is a characteristic view which shows the operation example of an advance angle control part. It is a connection diagram which shows the structural example of a PWM control part and an inverter. It is a block diagram which shows the control system of the dead time compensation by this invention. It is a characteristic view which shows an example of a dead band characteristic part. It is a general block diagram of the conventional electric power steering device. It is a block block diagram which shows an example of the control apparatus of the conventional electric power steering apparatus.

Explanation of symbols

10 Torque sensor 12 Vehicle speed sensor 20 Motor 21 Resolver (Hall sensor)
30 Control unit 302 PWM control unit 303 Inverter 310 Current command value determination unit 311 Assist map 313 Compensation value calculation unit 316 Current command value calculation unit 320 Current control unit 324 Gradual change gain unit 325 Current controller 330 Steering state detection unit 340 High-speed steering Judgment part 350 Advance angle control part

Claims (7)

A motor for applying a steering assist force to a steering system of a vehicle, a torque sensor for detecting a steering force acting on a steering wheel, and a current command value determining means for determining a current command value based on a steering torque value from the torque sensor; A control device for an electric power steering apparatus comprising: current detection means for detecting a motor current; and current control means for outputting a voltage command value based on the current command value and the motor current, according to the state of the steering system. A control device for an electric power steering apparatus, wherein the parameter of the current control means is corrected. 2. The control device for an electric power steering apparatus according to claim 1, wherein in high-speed steering, the gain is increased and the time constant is decreased as correction of the parameter. 3. The control device for an electric power steering apparatus according to claim 2, wherein the advance angle compensation parameter is corrected to reduce the advance angle amount. 3. The control device for an electric power steering apparatus according to claim 2, wherein a parameter for dead time compensation is corrected to reduce a phase delay of the feedback model. 2. The control device for an electric power steering apparatus according to claim 1, wherein when the steering torque value is larger than a predetermined value of the steering torque, the gain is increased and the time constant is decreased as correction of the parameter. The control device for an electric power steering apparatus according to claim 1, wherein when the current command value is larger than a current command value predetermined value, the gain is increased and the time constant is decreased as correction of the parameter. 2. The control device for an electric power steering apparatus according to claim 1, wherein when the rotational speed of the motor is larger than a predetermined rotational speed value, the gain is increased and the time constant is decreased as correction of the parameter.

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