JP2013082424A - Electric power steering device - Google Patents

Abstract

An electric power steering apparatus capable of effectively suppressing the deflection of a vehicle with a simple configuration and obtaining a comfortable steering feeling.
In a current command value calculation unit, a time during which the amount of change in the low-pass filtered torque T is within a predetermined value and the amount of change in the low-pass filtered torque T is within a predetermined value is a predetermined time. When the above is continued, a lead pull correction control unit 27 for calculating a lead pull correction amount Iip * as a correction component for reducing the steering torque τ is provided. Then, the current command value calculation unit 22 converts the lead pull correction amount Iip * calculated by the lead pull correction control unit 27 into the basic assist control amount Ias * as the basic component calculated by the basic assist control unit 26 in the adder 28. By superimposing, a current command value Iq * as a target assist force in the power assist control is calculated.
[Selection] Figure 2

Description

  The present invention relates to an electric power steering apparatus.

  2. Description of the Related Art Conventionally, power steering apparatuses for vehicles include an electric power steering apparatus (EPS) using a motor as a drive source. Usually, in such an EPS, the basic component (basic assist control amount) of the assist force applied to the steering system is calculated based on the detected steering torque.

  By the way, during actual traveling, there is a situation in which a steering operation for suppressing the deflection (lead pull) of the vehicle is required even though the vehicle is in a straight traveling state. For example, as shown in FIG. 12, the traveling path 41 of the vehicle 40 is often inclined in the width direction for reasons such as improved drainage. When traveling, the steering torque for suppressing the deflection due to the gravity is required. And when such a cant road driving | running | working takes a long time, the continuous load will be accumulate | stored in a driver | operator as fatigue.

  In order to solve such a problem, conventionally, a method has been proposed in which a cant state of a vehicle travel path is determined and a control component for suppressing the deflection of the vehicle is calculated based on the determination result. For example, the vehicle control device described in Patent Literature 1 learns a cant state of a vehicle travel path based on a plurality of detected state quantities such as vehicle speed and lateral acceleration, or a steering state and travel environment information. A kant state is determined by performing a neural network calculation using the learning result, and a control component for suppressing the deflection of the vehicle due to the presence of the cant is calculated.

JP 2007-22169 A

  However, in the configuration in which precise cant state determination is performed as in Patent Document 1, an increase in cost due to an increase in the calculation load is unavoidable, and in addition, if the complexity of the configuration is considered, this is There is a possibility that it is difficult to say that it is a realistic solution, and there is still room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric power capable of effectively suppressing the deflection of the vehicle with a simple configuration and obtaining a comfortable steering feeling. The object is to provide a steering device.

  In order to solve the above problems, the invention according to claim 1 is directed to a steering force assisting device (13) having a motor (12) for applying an assisting force to a steering system, and power to the motor (12). A control means (21) for supplying and controlling the operation of the steering force assisting device (13), a torque sensor (15) for detecting steering torque, a vehicle speed sensor (16) for detecting vehicle speed, and the torque sensor ( A low-pass filter (30) for removing the high-frequency component of the steering torque detected from 15) and outputting the processed torque, and a change amount detecting means (21) for detecting the change amount of the processed torque, The control means (21) calculates a basic assist force based on the steering torque and the vehicle speed, executes a normal control for controlling the operation of the steering force assisting device (13) according to the basic assist force, When the change amount is within a predetermined value and the time during which the change amount is within the predetermined value continues for a predetermined time or more, the control means (21) reduces the assist force with respect to the basic assist force. The gist of the present invention is to execute lead pull control for controlling the operation of the steering force assisting device (13) so as to gradually increase.

  According to the above configuration, the driver's steering intention can be estimated by detecting the amount of change in the low-pass filtered torque (hereinafter referred to as the processed torque) from which the high-frequency component has been removed by the low-pass filter. . That is, it is possible to estimate the driver's intention to go straight because the amount of change in the processed torque is within a predetermined value and the time within the predetermined value continues for a predetermined time or more. At this time, by gradually increasing the assist force, it is possible to assist the steering torque for suppressing gravity deflection on the cant road. As a result, when a constant steering torque is applied to the steering system for a long time on the cant road, the steering torque can be reduced, so that a comfortable steering feeling can be obtained. Further, by adopting the removal of high-frequency components by a low-pass filter, it is possible to obtain an effect with a simple configuration as compared with a neural network calculation or the like.

  According to a second aspect of the present invention, the control means (21) calculates an additional assist force that gradually increases as time elapses in the lead-pull control, and the control means (21) corresponds to a value obtained by adding the additional assist force to the basic assist force. The gist is to control the operation of the steering force assisting device (13).

According to the above configuration, in the lead pull control, the additional assist force that gradually increases as time elapses is calculated, and control is performed according to the value obtained by adding the additional assist force to the basic assist force.
As a result, since the steering torque for suppressing the gravity deflection on the cant road can be reduced slowly, a comfortable steering feeling can be obtained.

  According to a third aspect of the present invention, the control means (21) sets the assist force to a value at that time when the steering torque becomes zero after starting the gradual increase of the assist force by lead pull control. The gist is to fix.

According to the above configuration, when the steering force becomes zero as a result of gradually increasing the assist force by the lead pull control, the assist force is fixed to the value at that time.
As a result, a state in which the steering torque is almost zero can be continued, and a comfortable steering feeling can be obtained.

  The gist of the invention described in claim 4 is that the control means executes normal control when the amount of change becomes larger than a predetermined value after fixing the assist force during lead pull control. To do.

According to the above configuration, after the assist force is fixed during the lead pull control, if the amount of change becomes larger than a predetermined value, it is determined that the driver has made the cut, the lead pull control is interrupted, and the normal control is performed. Transition.
As a result, the lead-pull control makes it possible to smoothly shift to the assist control even when a large assist force is required from the steered state where the steering torque is almost zero to the notch state. You can get a ring.

  ADVANTAGE OF THE INVENTION According to this invention, the electric power steering apparatus which can suppress the deflection | deviation of a vehicle effectively with a simple structure and can obtain a comfortable steering feeling can be provided.

The schematic block diagram of an electric power steering device (EPS). The control block diagram of EPS. Explanatory drawing which shows the structure of a lead pull correction control part. Explanatory drawing showing the principle of a low-pass filter. Explanatory drawing showing the sampling structure of a steering torque value. Explanatory drawing which shows an example of the lead pull correction amount computed in order to reduce steering torque. The flowchart which shows the process sequence of a lead pull correction | amendment determination part. The flowchart which shows the process sequence of a lead pull correction start determination subroutine. The flowchart which shows the process sequence of a lead pull correction amount calculation subroutine (1/2). The flowchart which shows the process sequence of a lead pull correction amount calculation subroutine (2/2). The flowchart which shows the process sequence of a lead pull correction control subroutine. Explanatory drawing which shows the inclination of a vehicle travel path.

Hereinafter, an embodiment of the present invention embodied in a column type electric power steering apparatus 1 (hereinafter referred to as EPS) will be described with reference to the drawings.
As shown in FIG. 1, in the EPS 1 of the present embodiment, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4. The rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4.

  The steering shaft 3 of this embodiment is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. Then, the reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 6 connected to both ends of the rack shaft 5, whereby the steering angle of the steered wheels 7. Is changed.

  Further, the EPS 1 includes an EPS actuator 13 that applies an assist force for assisting a steering operation to the steering system, and an ECU 11 that serves as a control unit that controls the operation of the EPS actuator 13.

  The EPS actuator 13 of the present embodiment is a column type EPS actuator, and the motor 12 that is a driving source thereof is drivingly connected to the column shaft 8 via a speed reduction mechanism 14. The EPS actuator 13 applies the motor torque as an assist force to the steering system by decelerating the rotation of the motor 12 by the speed reduction mechanism 14 and transmitting it to the column shaft 8.

  The ECU 11 is connected to a vehicle speed sensor 16, a torque sensor 15, a motor rotation angle sensor 18, and front and rear, left and right wheel speed sensors W1 to W4. The wheel speed sensors W1 and W2 are sensors for detecting the wheel speed of the front wheel, and the wheel speed sensors W3 and W4 are sensors for detecting the wheel speed of the rear wheel. The ECU 11 detects the vehicle speed V, the steering torque τ, the motor rotation angle θ, and the front, rear, left and right wheel speeds w1 to w4 based on the output signals of these sensors. For example, the torque sensor 15 of the present embodiment is a twin resolver type torque sensor in which a pair of resolvers are provided at both ends of a torsion bar (not shown). Further, the ECU 11 calculates a target assist force based on each detected state quantity, and controls the operation of the EPS actuator 13, that is, the assist force applied to the steering system through the supply of drive power to the motor 12. To do.

Next, an aspect of assist control in the EPS of the present embodiment will be described.
As shown in FIG. 2, the ECU 11 includes a microcomputer 21 that outputs a motor control signal and a drive circuit 24 that supplies drive power to the motor 12 based on the motor control signal.

  In the present embodiment, the ECU 11 includes a current sensor 25 for detecting the actual current value I supplied to the motor 12 and a motor rotation angle sensor 18 for detecting the rotation angle θ of the motor 12 (see FIG. 1). Is connected. The microcomputer 21 drives the drive circuit 24 based on the vehicle state quantities and the actual current value I of the motor 12 and the motor rotation angle θ detected based on the output signals of the current sensor 25 and the motor rotation angle sensor 18. A motor control signal to be output to is generated.

  Each control block shown below is realized by a computer program executed by the microcomputer 21. Then, the microcomputer 21 detects each state quantity at a predetermined sampling period, and generates a motor control signal by executing each arithmetic processing shown in the following control blocks every predetermined period.

  More specifically, the microcomputer 21 of this embodiment includes a current command value calculation unit 22 that calculates a current command value Iq * that is a target value for power supply to the motor 12, and a current command calculated by the current command value calculation unit 22. And a motor control signal output unit 23 that outputs a motor control signal based on the value Iq *.

  The current command value calculation unit 22 is provided with a basic assist control unit 26 for calculating a basic assist control amount Ias * as a basic component of the assist force target value. In the present embodiment, the basic assist control unit 26 is provided. Is input with the vehicle speed V and the steering torque τ. The basic assist control unit 26 is configured to calculate a basic assist control amount Ias * indicating that a larger assist force should be applied as the absolute value of the steering torque τ is larger and the vehicle speed V is smaller. .

  The motor control signal output unit 23 includes the current command value Iq * output from the current command value calculation unit 22, the actual current value I detected by the current sensor 25, and the motor rotation detected by the motor rotation angle sensor 18. The angle θ is input. The motor control signal output unit 23 calculates a motor control signal by executing current feedback control so that the actual current value I follows the current command value Iq *.

  Specifically, in the present embodiment, a brushless motor that rotates by supplying three-phase (U, V, W) driving power is used as the motor 12. The motor control signal output unit 23 converts the phase current value (Iu, Iv, Iw) of the motor 12 detected as the actual current value I into d and q axis current values in the d / q coordinate system (d / q The current feedback control is performed by performing conversion.

  That is, the current command value Iq * is input to the motor control signal output unit 23 as the q-axis current command value, and the motor control signal output unit 23 is based on the motor rotation angle θ detected by the motor rotation angle sensor 18. The current values (Iu, Iv, Iw) are d / q converted. The motor control signal output unit 23 calculates the d and q-axis voltage command values based on the d and q-axis current values and the q-axis current command value. Then, the phase voltage command values (Vu *, Vv *, Vw *) are calculated by performing d / q inverse conversion on the d and q axis voltage command values, and a motor control signal is generated based on the phase voltage command values. To do.

  The motor control signal generated in this way is output from the microcomputer 21 to the drive circuit 24, and the drive circuit 24 supplies three-phase drive power based on the motor control signal to the motor 12. Then, by generating a motor torque corresponding to the current command value Iq * as an assist force target value based on the steering torque τ, an assist force corresponding to the assist force target value is applied to the steering system. Yes.

(Lead pull correction control)
Next, the aspect of the lead pull correction control in this embodiment will be described.
As described above, when the input of the steering torque for canceling the factor that induces the deflection of the vehicle, such as traveling on the cant road (for example, the inclination of the road surface), is continued for a long time as fatigue. It will be accumulated in the driver.

  Therefore, in the present embodiment, the current command value calculation unit 22 of the microcomputer 21 has a lead pull correction amount Iip as a correction component for reducing the steering torque τ detected when it is determined that the vehicle is in a straight traveling state. A lead pull correction control unit 27 for calculating * is provided. Then, the current command value calculation unit 22 converts the lead pull correction amount Iip * calculated by the lead pull correction control unit 27 into the basic assist control amount Ias * as the basic component calculated by the basic assist control unit 26 in the adder 28. By superimposing, a current command value Iq * as a target assist force in the power assist control is calculated.

  In this embodiment, the assist force generated based on the lead pull correction amount Iip * suppresses the influence (gravity) due to the inclination of the traveling road surface, which is a factor that induces the vehicle deflection, thereby suppressing the deflection. It is designed to reduce the burden on the driver.

Details of the lead pull correction control unit 27 will be described with reference to FIG.
Steering torque τ, vehicle speed V, front and rear wheel speeds ω1 to ω4, and motor rotation angle θ are input to lead pull correction control unit 27. The steering torque τ is input to the lead pull correction determination unit 31 via the low pass filter 30. The lead pull correction determination unit 31 also receives front / rear / right / left wheel speeds w1 to w4. The lead pull correction determination unit 31 calculates a lead pull correction amount Tcon from the input processed torque T and front / rear and left / right wheel speeds w1 to w4, determines whether the lead pull correction control start flag FLGkrs is on / off, and Output.

  When the lead pull correction control start flag FLGkrs is “1”, the switching unit 32 connects the contacts 32a and 32c, and uses the lead pull correction amount Tcon calculated by the lead pull correction determination unit 31 as the preceding stage lead pull correction amount Iip *. * Output to the generation map 34. On the other hand, when the read pull correction control start flag FLGkrs is “0”, the switching unit 32 connects the contacts 32b and 32c and generates the data “0” stored in the memory 33 to generate the previous lead pull correction amount Iip **. Output to the map 34. Then, the preceding stage lead pull correction amount Iip ** generated by the preceding stage lead pull correction amount Iip ** generation map 34 is output to the multiplier 38.

  The vehicle speed V is input to the vehicle speed gain Kv generation map 36, and the vehicle speed gain Kv generated by the vehicle speed gain Kv generation map 36 is output to the multiplier 38. Further, the motor rotation angle θ is differentiated by the differentiator 37 to generate a motor rotation angular velocity ω. The motor rotation angular velocity ω is input to the motor rotation angular velocity gain Kω generation map 35, and the motor rotation angular velocity gain Kω generated by the motor rotation angular velocity gain Kω generation map 35 is output to the multiplier 38. The preceding stage lead pull correction amount Iip **, the motor rotational angular velocity gain Kω, and the vehicle speed gain Kv are multiplied by the multiplier 38 and output from the lead pull correction control unit 27 as the lead pull correction amount Iip *, and the basic assist control amount Ias * described above. The adder 28 adds the values.

Next, details of the function of the low-pass filter 30 will be described with reference to FIGS.
As shown in FIG. 4, the steering torque τ input to the lead pull correction control unit 27 includes a high frequency component on the low pass filter input side 30p (see FIG. 30p). When this signal is passed through the low-pass filter 30, the high-frequency component is removed on the low-pass filter output side 30q to form a smooth curve (see FIG. 30q). The smooth post-processing torque T is input to the lead pull correction determination unit 31. FIG. 5 is a variation diagram of the processed torque T shown in FIG. As shown in FIG. 5, the processed torque T is sampled at a predetermined sampling time (for example, T (1), T (2), etc.) and processed in the lead pull correction determination unit 31.

  In the present embodiment, the amount of change in the processed torque T to be sampled is measured. Specifically, when the amount of change in the processed torque T is within a predetermined value for a predetermined time (the lead pull correction start determination timer predetermined value Tf in FIG. 5) has elapsed, the vehicle is operated in a steered state to suppress vehicle deflection. It is determined that the person has entered, and calculation of the lead pull correction amount Tcon is started. The time for executing the calculation of the lead pull correction amount Tcon is determined by the lead pull correction amount calculation timer predetermined value Tr.

  Then, the post-processing torque T sampled until the lead-pull correction amount calculation timer Tr expires is integrated, and the average value is the steering torque τ required by the driver in the steering holding state for suppressing the deflection of the vehicle. Is determined. Then, the processed torque T obtained by dividing the average value is added to the basic assist control amount Ias * as the lead pull correction amount Iip *.

  More specifically, when the lead pull correction control unit 27 of this embodiment determines that the lead pull correction should be executed, it determines the direction (sign) of the detected steering torque T and is the same as the determined direction. The lead pull correction amount Iip * is gradually increased in the direction, that is, in the direction of decreasing the detected post-processing torque T (see FIG. 6 (L2)). In this embodiment, the left direction is defined as “+” and the right direction is defined as “−” in the traveling direction of the vehicle. Then, the post-processing torque T is gradually reduced (see FIG. 6 (L1)) and finally set to “0”, so that the lead pull correction is performed without giving the driver a sense of incongruity. It has become.

Next, a processing procedure of the lead pull correction determination unit 31 in the lead pull correction control unit 27 configured as described above will be described.
As shown in the flowchart of FIG. 7, the microcomputer 21 performs a read pull correction start determination (step S <b> 101). Next, the lead pull correction amount is calculated (step S102). Then, lead pull correction control is performed (step S103), and the process is terminated.

Next, the contents of steps S101 to S103 will be described in detail.
First, details of the lead pull correction start determination (step S101) will be described based on the flowchart of FIG.
First, the microcomputer 21 resets the processed torque value take-in counter P (step S201). Next, the microcomputer 21 resets the lead pull correction start determination timer T1 (step S202). Further, the microcomputer 21 resets the read pull correction start determination counter Kf (step S203).

  Then, the microcomputer 21 determines whether or not the processed torque value acquisition counter P is equal to or smaller than the processed torque value acquisition counter predetermined value Ps (step S204). When the processed torque value acquisition counter P is equal to or smaller than the processed torque value acquisition counter predetermined value Ps (P ≦ Ps, step S204: YES), the microcomputer 21 determines the processed torque value T (P) at the sampling P point. (Step S205).

  Next, the microcomputer 21 determines whether or not the absolute value of the processed torque value T (P) at the sampling P point is equal to or greater than the predetermined value Tps of the processed torque value (step S206). When the absolute value of the processed torque value T (P) at the sampling P point is equal to or greater than the predetermined value Tps of the processed torque value (| T (P) | ≧ Tps, step S206: YES), A post-difference torque value ΔT (P) between the sampling P point and the (P-1) point is calculated (step S207).

  Next, the microcomputer 21 determines whether or not the absolute value of the post-difference torque value ΔT (P) between the sampling P point and the (P−1) point is equal to or smaller than a predetermined value ΔTs of the post-difference torque value (step). S208). When the absolute value of the difference processed torque value ΔT (P) between the sampling P point and the (P−1) point is equal to or smaller than the predetermined value ΔTs of the difference processed torque value (| ΔT (P) | ≦ ΔTs, step S208: YES), the lead pull correction start determination counter Kf is incremented (Kf = Kf + 1, step S210).

  Next, the microcomputer 21 determines whether or not the read pull correction start determination counter Kf is equal to or larger than a read pull correction start determination counter predetermined value Kfs (step S211). Then, the microcomputer 21 sets the read pull correction start determination flag FLGkr (FLGkr = “1”) when the read pull correction start determination counter Kf is equal to or larger than the read pull correction start determination counter predetermined value Kfs (Kf ≧ Kfs, step S211: YES). Step S212), and the process ends.

  On the other hand, when the read pull correction start determination counter Kf is less than the read pull correction start determination counter predetermined value Kfs (Kf <Kfs, step S211: NO), the microcomputer 21 determines that the read pull correction start determination timer T1 is the read pull correction start determination timer predetermined value. It is determined whether or not it is equal to or higher than Tf (step S213). The microcomputer 21 resets the read pull correction start determination flag FLGkr (FLGkr = “0”) when the read pull correction start determination timer T1 is equal to or greater than the read pull correction start determination timer predetermined value Tf (T1 ≧ Tf, step S213: YES). Step S214) and the process ends.

  Further, when the read pull correction start determination timer T1 is less than the read pull correction start determination timer predetermined value Tf (T1 <Tf, step S213: NO), the microcomputer 21 increments the read pull correction start determination timer T1 (T1 = T1 + 1, step). S215). Further, the microcomputer 21 increments the processed torque value take-in counter P (P = P + 1, step S216), and proceeds to step S204.

  Further, the microcomputer 21 determines that the absolute value of the post-difference torque value ΔT (P) between the sampling P point and the (P-1) point is greater than the predetermined value ΔTs of the post-difference torque value (| ΔT (P) | > ΔTs, step S208: NO), the processed torque value take-in counter P is incremented (P = P + 1, step S216), and the process proceeds to step S204.

  Furthermore, when the absolute value of the processed torque value T (P) at the sampling P point is less than the predetermined value Tps of the processed torque value (| T (P) | <Tps, step S206: NO), The lead pull correction start determination flag FLGkr is reset (FLGkr = “0”, step S214), and the process is terminated.

Next, details of the lead pull correction amount calculation (step S102) will be described based on the flowchart of FIG.
First, the microcomputer 21 determines whether or not the read pull correction start determination flag FLGkr is set (step S301). If the lead pull correction start determination flag FLGkr is set (FLGkr = “1”, step S301: YES), the microcomputer 21 sets “1” to the post-pull correction amount calculation processed torque value take-in count n. (Step S302).

  Next, the microcomputer 21 resets the post-torque value acquisition counter Kr for the lead-pull correction amount calculation application process (step S303). Further, the microcomputer 21 resets the post-process total torque addition value Tsum for calculating the lead pull correction amount (step S304).

  Next, the microcomputer 21 determines whether or not the processed torque value acquisition counter n for the lead pull correction amount calculation is equal to or smaller than the predetermined value ns after the processing of the torque value acquisition counter for the lead pull correction amount calculation (step S305). Then, the microcomputer 21 performs sampling n when the post-pull correction amount calculation post-processing torque value acquisition counter n is equal to or less than a predetermined value ns after the lead pull correction amount calculation processing torque value acquisition counter (n ≦ ns, step S305: YES). The torque value T (n) after the point processing is taken in (step S306).

  Next, the microcomputer 21 determines whether or not the absolute value of the processed torque value T (n) at the sampling n point is equal to or greater than the predetermined value Tps of the processed torque value (step S306a). When the absolute value of the processed torque value T (n) at the sampling n point is equal to or greater than the predetermined value Tps of the processed torque value (| T (n) | ≧ Tps, S306a: YES), The left and right wheel speeds w1 (n) to w4 (n) are taken in (step S307).

  Next, the microcomputer 21 calculates a post-difference torque value ΔT (n) between the sampling n point and the (n−1) point (step S308). Then, the microcomputer 21 determines whether or not the absolute value of the difference processed torque value ΔT (n) between the sampling n point and the (n−1) point is equal to or less than the predetermined value ΔTs of the difference processed torque value (step S309). ). Then, the microcomputer 21 determines that the absolute value of the difference difference processed value ΔT (n) at the sampling n point and the (n−1) point is equal to or smaller than the predetermined value ΔTs of the difference processed torque value (| ΔT (n) | ≦ ΔTs, step S309: YES), it is determined whether or not the absolute value of the front wheel left and right wheel speed difference w1 (n) −w2 (n) is equal to or smaller than the left and right wheel speed difference predetermined value ws1 (step S310).

  When the absolute value of the front wheel left / right wheel speed difference w1 (n) −w2 (n) is equal to or smaller than the left / right wheel speed difference predetermined value ws1 (| w1 (n) −w2 (n) | ≦ ws1, Step S310: YES), it is determined whether or not the absolute value of the rear wheel left and right wheel speed difference w3 (n) -w4 (n) is equal to or smaller than the left and right wheel speed difference predetermined value ws1 (step S311). When the absolute value of the rear wheel left / right wheel speed difference w3 (n) −w4 (n) is equal to or smaller than the left / right wheel speed difference predetermined value ws1 (| w3 (n) −w4 (n) | ≦ ws1) , Step S311: YES), the post-processing torque value T (n-1) for all the post-pull correction amount calculation is added to the previous value Tsum (n-1), and the post-processing torque value T (n) at the sampling point n is added. The total torque value after processing Tsum (n) is calculated (step S312).

  Next, the microcomputer 21 increments the post-pull torque amount calculation application post-torque value take-in counter Kr (Kr = Kr + 1, step S313). Then, the microcomputer 21 determines whether or not the post-application torque value acquisition counter Kr for the lead pull correction amount calculation is equal to or greater than the predetermined value Krs after the application processing for the lead pull correction amount calculation (step S314).

  When the post-applied torque value acquisition counter Kr for the lead pull correction amount calculation is equal to or greater than the predetermined value Krs after the lead pull correction amount calculation application processing (Kr ≧ Krs, step S314: YES). By dividing the current value Tsum (n) after all processing torque addition value for lead pull correction amount calculation by the applied torque value acquisition counter Kr after lead pull correction amount calculation, the average torque value Tave after all processing for lead pull correction amount calculation is obtained. Calculate (step S315).

  Further, the microcomputer 21 sets the torque average value Tave after all processing for calculating the lead pull correction amount to a predetermined constant R (R is determined to be a value that can provide a good steering feeling when performing the lead pull correction amount control). The lead pull correction amount Tcon is calculated by dividing by (step S316). Then, the microcomputer 21 sets the read pull correction control start flag FLGkrs (FLGkrs = “1”, step S317), and ends the process.

On the other hand, the microcomputer 21 determines that the post-correction torque value acquisition counter Kr for the lead pull correction amount calculation is less than the predetermined value Krs after the application processing for the lead pull correction amount calculation (Kr <Krs, step S314: NO). It is determined whether or not the lead pull correction amount calculation timer T2 is equal to or greater than a lead pull correction amount calculation timer predetermined value Tr (step S318).
When the lead pull correction amount calculation timer T2 is equal to or greater than the lead pull correction amount calculation timer predetermined value Tr (T2 ≧ Tr, step S318: YES), the microcomputer 21 resets the read pull correction control start flag FLGkrs (FLGkrs = “0”). Step S319) and the process ends.

  If the lead pull correction amount calculation timer T2 is less than the lead pull correction amount calculation timer predetermined value Tr (T2 <Tr, step S318: NO), the microcomputer 21 increments the lead pull correction amount calculation timer T2 (T2 = T2 + 1, step). S320). Further, the microcomputer 21 increments the post-pull correction amount calculation post-processing torque value take-in counter n (n = n + 1, step S321), and proceeds to step S305.

  The microcomputer 21 also determines that the absolute value of the difference processed torque value ΔT (n) at the sampling n point and the (n−1) point is greater than the predetermined value ΔTs of the difference processed torque value (| ΔT (n) | > ΔTs, step S309: NO), or when the absolute value of the front wheel right / left wheel speed difference w1 (n) −w2 (n) is greater than the left / right wheel speed difference predetermined value ws1 (| w1 (n) −w2 (n) |> Ws1, Step S310: NO), or when the absolute value of the rear wheel left and right wheel speed difference w3 (n) -w4 (n) is greater than the left and right wheel speed difference predetermined value ws1 (| w3 (n) -w4 ( n) |> ws1, Step S311: NO), the lead pull correction amount calculation post-processing torque value take-in counter n is incremented (n = n + 1, Step S321), and the process proceeds to Step S305.

  Furthermore, when the absolute value of the processed torque value T (n) at the sampling n point is less than the predetermined value Tps of the processed torque value (| T (n) | <Tps, step S306a: NO), The lead pull correction control start flag FLGkrs is reset (FLGkrs = “0”, step S319), and the process ends.

Next, details of the lead pull correction control (step S103) will be described based on the flowchart of FIG.
First, the microcomputer 21 determines whether or not the read pull correction control start flag FLGkrs is set (step S401). When the read pull correction control start flag FLGkrs is set (FLGkrs = “1”, step S401: YES), the microcomputer 21 resets the lead pull correction control counter m (m = “0”, step S402). Next, the microcomputer 21 resets the initial value of the preceding stage lead pull correction amount Iip ** (Iip ** (0) = “0”, step S403). Furthermore, the microcomputer 21 resets the initial value of the difference ΔT in the processed torque value (ΔT (1) = “0”, step S404).

  Then, the microcomputer 21 takes in the processed torque value T (m) at the sampling m point (step S405). Next, the microcomputer 21 determines whether or not the absolute value of the processed torque value T (m) at the sampling m point is equal to or greater than the predetermined value Tps of the processed torque value (step S406a). When the absolute value of the processed torque value T (m) at the sampling m point is equal to or greater than the predetermined value Tps of the processed torque value (| T (m) | ≧ Tps, step S406a: YES), A post-difference torque value ΔT (m) between the sampling m point and the (m−1) point is calculated (step S406).

  Next, the microcomputer 21 determines whether or not the absolute value of the difference processed torque value ΔT (m) between the sampling m point and the (m−1) point is equal to or less than the predetermined value ΔTss of the difference processed torque value (step). S407). When the absolute value of the difference processed torque value ΔT (m) between the sampling m point and the (m−1) point is equal to or smaller than the predetermined value ΔTss of the difference processed torque value (| ΔT (m) | ≦ ΔTss, Step S407: YES), it is determined whether or not the post-processing torque value T (m) at the sampling m point is positive (Step S408).

  Next, when the processed torque value T (m) at the sampling m point is positive (T (m)> 0, step S408: YES), the microcomputer 21 determines the previous value Iip ** (m− The current value Iip ** (m) of the preceding stage lead pull correction amount is calculated by adding the lead pull correction amount Tcon to 1) (Iip ** (m) = Iip ** (m−1) + Tcon, step S409). . Then, the microcomputer 21 increments the read pull correction control counter m (m = m + 1, step S410), and proceeds to step S401.

  On the other hand, when the processed torque value T (m) at the sampling m point is negative (T (m) <0, step S411: YES), the microcomputer 21 determines the previous value Iip ** (m−1) of the preceding lead pull correction amount. ) To subtract the lead pull correction amount Tcon to calculate the current value Iip ** (m) of the preceding lead pull correction amount (Iip ** (m) = Iip ** (m−1) −Tcon, step S412). . Then, the microcomputer 21 increments the read pull correction control counter m (m = m + 1, step S410), and proceeds to step S401.

  Furthermore, when the processed torque value T (m) at the sampling m point is 0 (T (m) = 0, step S411: NO), the microcomputer 21 determines the previous value Iip ** (m−1) of the preceding lead pull correction amount. ) Is the current value Iip ** (m) of the preceding lead pull correction amount (Iip ** (m) = Iip ** (m−1), step S413). Then, the microcomputer 21 increments the read pull correction control counter m (m = m + 1, step S410), and proceeds to step S401.

  Further, when the absolute value of the processed torque value T (m) at the sampling m point is less than the predetermined value Tps of the processed torque value (| T (m) | <Tps, step S406a: NO), Alternatively, when the absolute value of the difference processed torque value ΔT (m) at the sampling m point and the (m−1) point is larger than the predetermined value ΔTss of the difference processed torque value (| ΔT (m) |> ΔTss, step S407: NO), the read pull correction control start flag FLGkrs is reset (FLGkrs = “0”, step S414), and the process is terminated.

As described above, according to the present embodiment, the following operations and effects can be obtained.
In the current command value calculation unit 22, if the amount of change in the processed torque T is within a predetermined value and the time in which the amount of change in the processed torque T is within the predetermined value continues for a predetermined time or longer, the current command value calculation unit 22 A lead pull correction control unit 27 for calculating a lead pull correction amount Iip * as a correction component for reducing the rear torque T is provided. Then, the current command value calculation unit 22 converts the lead pull correction amount Iip * calculated by the lead pull correction control unit 27 into the basic assist control amount Ias * as the basic component calculated by the basic assist control unit 26 in the adder 28. By superimposing, a current command value Iq * as a target assist force in the power assist control is calculated.

  In this embodiment, the assist force generated based on the lead pull correction amount Iip * suppresses the influence (gravity) due to the inclination of the traveling road surface, which is a factor that induces the vehicle deflection, thereby suppressing the deflection. It is designed to reduce the burden on the driver.

  As a result, when a constant steering torque τ is applied to the steering system for a long time, the steering torque τ can be reduced, so that the vehicle can be effectively prevented from being deflected with a simple configuration and comfortable steering can be performed. Feeling can be obtained.

In addition, you may change this embodiment as follows.
In each of the above embodiments, the present invention is embodied in a so-called column type EPS 1, but the present invention may be applied to a so-called pinion type or rack assist type EPS.

In the above embodiment, the present invention is embodied in EPS using a brushless motor as a drive source. However, the present invention may be applied to EPS using a DC motor with a brush as a drive source.

In the above embodiment, the present invention is configured to calculate the lead pull correction amount Iip * by adding the motor rotational angular velocity gain Kω and the vehicle speed gain Kv to the preceding stage lead pull correction amount Iip **. However, the motor rotational angular velocity gain Kω and the vehicle speed gain Kv may be either one or neither.

In the above embodiment, the present invention is configured to perform the lead pull correction start determination (step S101) before the lead pull correction amount calculation (step S102). However, the lead pull correction start determination (step S101) is not performed, and the absolute value of the difference processed torque value ΔT (n) between the sampling n point and the (n−1) point is equal to or less than the predetermined value ΔTs of the difference processed torque value. In this case, it is of course possible to employ a configuration in which the lead pull correction amount calculation (step S102) is performed immediately.

1: Electric power steering device (EPS), 2: Steering,
3: Steering shaft, 4: Rack and pinion mechanism, 5: Rack shaft,
6: Tie rod, 7: Steering wheel, 8: Column shaft,
9: Intermediate shaft, 10: Pinion shaft, 11: ECU,
12: Motor, 13: EPS actuator (steering force assist device), 14: Deceleration mechanism,
15: Torque sensor, 16: Vehicle speed sensor, 18: Motor rotation angle sensor,
21: Microcomputer, 22: Current command value calculation unit, 23: Motor control signal output unit,
24: drive circuit, 25: current sensor, 26: basic assist control unit,
27: lead pull correction control unit, 28: adder, 30: low-pass filter,
30p: low-pass filter input side, 30q: low-pass filter output side,
31: lead pull correction determination unit, 32: switching unit, contacts: 32a, 32b, 32c,
33: Memory, 34: Previous stage lead pull correction amount Iip ** generation map,
35: Motor rotation angular velocity gain Kω generation map, 36: Vehicle speed gain Kv generation map,
37: Differentiator, 38: Multiplier, 40: Vehicle, 41: Traveling road, 42, 43: Kant road,
W1 to W4: Front and rear, left and right wheel speed sensors,
V: vehicle speed, τ: steering torque, θ: motor rotation angle,
w1 (n) to w4 (n): front, rear, left and right wheel speeds,
I: actual current value, ω: motor rotation angular velocity, ws1: left and right wheel speed difference predetermined value,
Iq *: current command value, Ias *: basic assist control amount,
Iip *: Lead pull correction amount, Iip **: Previous lead pull correction amount,
Iu, Iv, Iw: Phase current value, Vu *, Vv *, Vw *: Phase voltage command value,
Kω: motor rotation angular velocity gain, Kv: vehicle speed gain,
T: Torque after processing, T (P): Torque value after processing at sampling P point,
Tps: predetermined value of the processed torque value,
ΔT (P): Torque value after differential processing between sampling P point and (P-1) point,
ΔTs: a predetermined value of the torque value after differential processing,
T (n): Torque value after processing at sampling n point,
ΔT (n): Torque value after differential processing between sampling n point and (n−1) point,
T (m): Torque value after processing at sampling m point
ΔT (m): Torque value after differential processing between sampling m point and (m−1) point,
ΔTss: a predetermined value of the torque value after differential processing,
P: Torque value taking counter after processing, Ps: Torque value taking counter predetermined value after processing,
T1: lead pull correction start determination timer, Tf: lead pull correction start determination timer predetermined value,
T2: lead pull correction amount calculation timer, Tr: lead pull correction amount calculation timer predetermined value,
Kf: lead pull correction start determination counter,
Kfs: Read pull correction start determination counter predetermined value,
FLGkr: Lead pull correction start determination flag,
FLGkrs: Lead pull correction control start flag,
n: Torque value take-in counter after processing for lead pull correction amount calculation,
ns: pre-torque value calculation counter for lead pull correction amount calculation predetermined value,
m: lead pull correction control counter,
Kr: Torque value acquisition counter after application processing for lead pull correction amount calculation,
Krs: Torque value take-in counter predetermined value after application processing for lead pull correction amount calculation,
Tsum: Torque addition value after all processing for calculating lead pull correction amount,
Tave: Average torque value after all processing for lead pull correction calculation
R: Value for obtaining a good steering feeling when performing the lead pull correction amount control,
Tcon: Lead pull correction amount

Claims (4)

A steering force assisting device having a motor for applying assist force to the steering system;
Control means for supplying power to the motor and controlling the operation of the steering force assisting device;
A torque sensor for detecting steering torque;
A vehicle speed sensor for detecting the vehicle speed;
A low-pass filter that removes the high-frequency component of the steering torque detected from the torque sensor and outputs the processed torque;
A change amount detecting means for detecting a change amount of the post-processing torque,
The control means calculates a basic assist force based on the steering torque and the vehicle speed, and executes a normal control for controlling the operation of the steering force assisting device according to the basic assist force,
The control means gradually increases the assist force with respect to the basic assist force when the change amount is within a predetermined value and the time during which the change amount is within the predetermined value continues for a predetermined time or more. Performing lead pull control to control the operation of the steering force assisting device,
Electric power steering device characterized by   In the lead pull control, the control means calculates an additional assist force that gradually increases with time, and controls the operation of the steering force assisting device according to a value obtained by adding the additional assist force to the basic assist force. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is characterized.   The control means fixes the assist force to a value at that time when the steering torque becomes zero after the assist force is gradually increased by lead pull control. The electric power steering apparatus according to claim 2.   4. The electric power according to claim 3, wherein the control means executes normal control when the amount of change becomes larger than a predetermined value after fixing the assist force during lead pull control. 5. Steering device.

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