JP2003019974A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of improving a steering feeling of both forward steering and backward steering of a steering wheel. SOLUTION: This electric power steering device determines a current command value on the basis of a forward steering assist map 23a or a backward steering assist map 23b selected by a switching part 24 on the basis of the steering direction of the steering wheel determined by a forward steering- backward steering determining part 22, and steering torque detected by a torque sensor 11. Thus, since the current command value can be respectively determined on the basis of the forward steering assist map 23a and the steering torque at forward steering time of the steering wheel and on the basis of the backward steering assist map 23b and the steering torque at backward steering time of the steering wheel, superior assist torque respectively corresponding to a forward steering time steering feeling and a backward steering time steering feeling can be set to thus improve the steering feeling of both the forward steering and the backward steering of the steering wheel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus equipped with a motor for compensating a steering force based on a steering torque generated on a steering shaft.

[0002]

2. Description of the Related Art A motor control unit 90 of a conventional electric power steering apparatus has a structure as shown in FIG. That is, the sensor output output from the torque sensor that detects the steering torque is input to the phase compensating unit 91, the phase is advanced to increase the response to the torque sensor output, and then input to the assist map 93. . In this assist map 93, the current command value to be sent corresponding to the torque (hereinafter referred to as "assist torque") generated in the motor to assist the steering force is determined based on the phase-compensated torque signal. The current command value thus determined is subjected to predetermined proportional-plus-integral control by the PI controller 95 via the adder 99, and then converted into a pulse signal having a pulse width corresponding to the current command value by a PWM circuit or the like. Output to the motor.

On the other hand, the motor current flowing through the motor is detected by the motor current detector 97, and then the PI controller 95.
Since it is fed back to the adding unit 99 provided in the preceding stage, the PI control unit 95 performs proportional-plus-integral control so that the current command value and the detected value of the motor current match based on the deviation. As a result, the motor current applied to the motor is feedback-controlled, so that an assist torque suitable for the steering torque generated by steering the steering wheel can be generated in the motor.

[0004]

Here, in the conventional electric power steering apparatus 90, the assist map 93 for determining the current command value from the torque signal is the steering wheel rotation direction, that is, the steering wheel notch or notch. The same one (single assist map) is used regardless of the return (see Fig. 4 (B)). Therefore, one of the steering feeling when the steering wheel is turned (build-up feeling) and the steering feeling when the steering wheel is turned back (feeling returned) is preferentially set. Therefore, there is a problem that it is difficult to properly set both the steering feeling when the steering wheel is turned and the steering feeling when the steering wheel is turned back.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide an electric power steering apparatus capable of improving the steering feeling both when the steering wheel is turned and when the steering wheel is turned back and forth. To provide.

[0006]

[Means for Solving the Problems and Actions and Effects of the Invention]
In order to achieve the above object, the electric power steering apparatus according to claim 1 is an electric power steering apparatus including a motor for compensating a steering force based on a steering torque generated in a steering shaft. Based on the steering torque detected by the steering torque detecting means, the rotation direction detecting means detecting the rotation direction of the steering wheel, the steering torque detected by the steering torque detecting means, and the rotation direction of the steering wheel detected by the rotation direction detecting means. hand,
Depth cutback determination means for determining the depth of cut and reverse of the steering wheel, and assist torque selected based on the steering direction of the steering wheel determined by the depth cutback return determination means to supplement the steering force from the steering torque. Based on the steering torque detected by the steering torque detection means and the cut-in map or the cut-back map that can determine the current command means for determining the current command value to the motor, and the motor current flowing through the motor. Current detection means for detecting, and motor control means for feedback controlling the motor based on a deviation between a current command value determined by the current command means and a motor current detected by the current detection means. Is a technical feature.

According to the first aspect of the present invention, based on the steering torque detected by the steering torque detecting means and the rotation direction of the steering wheel detected by the rotation direction detecting means by the cut-and-return determining means, the cutting and turning of the steering wheel are performed. Determine the return. Then, the current command means determines the assist torque for supplementing the steering force from the steering torque, which is selected based on the steering direction of the steering wheel determined by the cut-back return determining means, and the steering torque detecting means. The current command value for the motor is determined based on the steering torque detected by. Furthermore, the motor current flowing through the motor is detected by the current detection means, and the motor control means feedbacks the motor based on the deviation between the current command value determined by the current command means and the motor current detected by the current detection means. Control.

That is, the current command value determined by the current command means is based on the steering torque and the cutting map or the switching back map selected based on the steering direction of the steering wheel. Thus, when the steering wheel is turned, the current command value can be determined based on the turning map and the steering torque, and when the steering wheel is turned back, the current command value can be determined based on the turning map and the steering torque. Since the command value can be determined, it is possible to set a good motor current and thus an assist torque corresponding to the steering feeling at the time of turning (build-up feeling) and the steering feeling at turning back (feeling returned). . Therefore, there is an effect that it is possible to improve the steering feeling both when the steering wheel is turned in and out.

Further, in the electric power steering apparatus according to a second aspect of the present invention, in the first aspect, the current command means includes a delay means for reducing a speed for selecting the cut-in map and the cut-back map to a predetermined value or less. This is a technical feature.

According to the second aspect of the present invention, the speed of selecting the cutting map and the switching back map selected by the current commanding means is reduced to a predetermined value or less by the delay means, so that the detected steering torque and steering wheel rotation direction are controlled. Even if it is in the vicinity of the threshold value that determines the selection of both maps, or if it includes a fluctuation component having a response speed exceeding the predetermined value in the steering torque or the rotation direction, the low range by the delay means is generated. These can be removed by the action of the pass filter. This makes it possible to stably select the cut-in map and the cut-back map. Therefore, there is an effect that it is possible to further improve the steering feeling both when the steering wheel is turned in and out.

Further, in the electric power steering apparatus according to a third aspect of the present invention, the electric power steering apparatus includes a motor for compensating the steering force based on the steering torque generated in the steering shaft, and the steering torque is detected. Steering torque detecting means, rotation direction detecting means for detecting the rotating direction of the steering wheel, based on the steering torque detected by the steering torque detecting means and the rotating direction of the steering wheel detected by the rotating direction detecting means, Based on a cut-and-return determination means for determining a cut and a return of the steering wheel, a cut map capable of determining an assist torque for supplementing the steering force from the steering torque, and a steering torque detected by the steering torque detection means. Cutting current command value to the motor, which is determined by A current command means for selecting either one of a cutback current command value for the motor, which is determined by performing a predetermined calculation on the flow command value, on the basis of the steering direction of the steering wheel determined by the cut-and-return determination means. A feedback control of the motor based on a deviation between a current detection means for detecting a motor current flowing through the motor and a current command value determined by the current command means and a motor current detected by the current detection means. And a motor control means.

According to the third aspect of the present invention, based on the steering torque detected by the steering torque detection means and the rotation direction of the steering wheel detected by the rotation direction detection means by the cut-and-return determination means, the cutting and cutting of the steering wheel are performed. Determine the return. Then, the current command means determines the assist torque for supplementing the steering force from the steering torque, and the cutting current command value to the motor determined based on the steering torque detected by the steering torque detection means, and this cutting. A switchback current command value for the motor, which is determined by performing a predetermined calculation on the current command value,
One of the two is selected based on the steering direction of the steering wheel determined by the cut-and-return determination means.
Furthermore, the motor current flowing through the motor is detected by the current detection means, and the motor control means feedbacks the motor based on the deviation between the current command value determined by the current command means and the motor current detected by the current detection means. Control.

That is, the current command value determined by the current command means is selected based on the steering direction of the steering wheel, and the cutting current command value and the motor to be determined by performing a predetermined calculation on the cutting current command value. This is the switchback current command value. Thus, when the steering wheel is turned, the cutting current command value can be determined based on the cutting map and the steering torque, and when the steering wheel is turned back, a predetermined calculation is performed on the cutting current command value. Since it is possible to determine the switchback current command value, set a good motor current and hence an assist torque corresponding to the steering feel (build-up feel) when turning and the steering feel (return feel) when switching back. In addition to the above, it is possible to reduce the storage space of the storage device that stores the switchback map and the like because the switchback map is not required. Therefore, in addition to the effect of improving the steering feeling both when the steering wheel is turned in and out, the device cost is further reduced.

According to another aspect of the electric power steering apparatus of the present invention, the electric power steering apparatus includes a motor for compensating the steering force based on the steering torque generated in the steering shaft. Steering torque detecting means, rotation direction detecting means for detecting the rotating direction of the steering wheel, based on the steering torque detected by the steering torque detecting means and the rotating direction of the steering wheel detected by the rotating direction detecting means, The steering wheel, a cut-back return determination means for determining the cut-in and return, (1) a reference map capable of determining the assist torque to supplement the steering force from the steering torque, (2) by the cut-back return determination means Amplify the assist torque selected based on the determined steering wheel turning direction Based on the predetermined cut-back gain or a predetermined cut-back gain set to be larger than the predetermined cut-in gain and (3) the steering torque detected by the steering torque detection means, a current command value to the motor is set. Based on the deviation between the current command means for determining, the current detecting means for detecting the motor current flowing through the motor, and the current command value determined by the current command means and the motor current detected by the current detecting means, And a motor control unit that feedback-controls the motor.

According to the fourth aspect of the present invention, based on the steering torque detected by the steering torque detecting means and the rotation direction of the steering wheel detected by the rotation direction detecting means by the cut-and-return determining means, the cutting and cutting of the steering wheel are performed. Determine the return. Then, the current command means (1) a reference map capable of determining the assist torque that supplements the steering force from the steering torque, and (2) the assist torque selected based on the steering wheel turning direction determined by the cut-and-return determination means. Based on the predetermined cut-back gain to be amplified or a predetermined cut-back gain set to be larger than this predetermined cut-off gain, and (3) the steering torque detected by the steering torque detection means, the current command value to the motor is set. decide. Furthermore, the motor current flowing through the motor is detected by the current detection means, and the motor control means feedbacks the motor based on the deviation between the current command value determined by the current command means and the motor current detected by the current detection means. Control.

That is, the current command value determined by the current command means is (1) a reference map capable of determining the assist torque for supplementing the steering force from the steering torque, and (2) the assist torque selected based on the steering wheel turning direction. A predetermined cut-off gain for amplifying the torque, or a predetermined cut-back gain set to be larger than the predetermined cut-in gain, and
(3) It is based on the steering torque detected by the steering torque detecting means. As a result, when the steering wheel is turned, the assist torque determined by the reference map from the steering torque is amplified with a predetermined turning gain to determine the current command value, and when the steering wheel is turned back, the steering torque is determined. It is possible to determine the current command value by amplifying the assist torque determined by the reference map from the above with a predetermined turning-back gain that is set to be larger than the predetermined cutting-in gain. ) And a steering feeling (return feeling) at the time of switching back, it is possible to set a good motor current and thus an assist torque. Therefore, there is an effect that it is possible to improve the steering feeling both when the steering wheel is turned in and out.

Further, in the electric power steering apparatus according to a fifth aspect of the present invention, the electric power steering apparatus according to the fourth aspect has a speed sensor for detecting a vehicle speed, and when the vehicle speed detected by the vehicle speed sensor is substantially zero, the current is reduced. A technical feature is that the command means sets the predetermined cut-back gain to a value of the predetermined cut-in gain or a value equal to or smaller than the predetermined cut-in gain, regardless of the steering direction of the steering wheel determined by the cut-in / cut-back determination means. And

According to the invention of claim 5, when the vehicle speed detected by the vehicle speed sensor is substantially zero, the current command means is
Regardless of the steering direction of the steering wheel determined by the cut-back return determining means, the predetermined cut-back gain is set to a value of the predetermined cut-in gain or a value equal to or smaller than the predetermined cut-off gain. It is possible to set the cutback gain of the above to a value of a predetermined cutoff gain or a value lower than the predetermined cutoff gain. As a result, it is possible to prevent the self-excited oscillation that tends to occur at the time of switching back when the vehicle speed is substantially zero. Therefore, even if the vehicle speed is substantially zero, there is an effect that the steering feeling of both the cutting and returning of the steering wheel can be further improved.

Furthermore, the electric power steering apparatus according to claim 6 is the electric power steering apparatus according to claim 1 or 2, further comprising a speed sensor for detecting a vehicle speed, and the vehicle speed sensor detects the speed. When the vehicle speed is almost zero,
The current command means is any one of the cut map, the cut back map, or another map that is neither the cut map nor the cut back map, and a steering torque detected by the steering torque detection means. It is a technical feature to determine a current command value to the motor based on the.

According to the sixth aspect of the invention, when the vehicle speed detected by the vehicle speed sensor is substantially zero, the current command means is:
A current command value to the motor based on one of the cut map, the cutback map, or another map that is neither the cutout map nor the cutback map, and the steering torque detected by the steering torque detecting means. Therefore, when the vehicle speed is almost zero, the current command value to the motor is determined based on one specific map and steering torque regardless of whether the steering wheel is turned or not. be able to. As a result, it is possible to prevent self-excited oscillation that tends to occur when the steering wheel is turned back when the vehicle speed is substantially zero. Therefore,
Even if the vehicle speed is almost zero, there is an effect that it is possible to further improve the steering feeling both when the steering wheel is turned in and out.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an electric power steering apparatus of the present invention will be described below with reference to the drawings. In the following embodiments, an electric power steering apparatus provided in a vehicle such as an automobile will be described as an example of the electric power steering apparatus of the present invention.

[First Embodiment] First, the main electrical configuration of an electric power steering apparatus will be described with reference to FIG. As shown in FIG. 2, the electric power steering apparatus 10 according to the present embodiment.
Mainly includes a steering wheel, a steering shaft connected to the steering wheel, a sensor group such as a torque sensor 11, a vehicle speed sensor 12, a steering angle sensor 13, an ECU 15 including a CPU 16 and an interface 17, and the ECU 15. And a motor M that is connected to the motor drive circuit 18 and can generate an assist torque.
The steering gear box and the like are driven by the assist torque of the drive. The steering wheel, steering shaft, and steering gear box are not shown.

The torque sensor 11 detects the steering torque, and determines the amount of twist of a torsion bar or the like that rotatably connects the input shaft connected to the steering wheel of the vehicle and the output shaft connected to the steering mechanism. It is detected based on. The detected steering torque is input to the ECU 15.

The vehicle speed sensor 12 detects the vehicle speed, and the vehicle speed thus detected is also input to the ECU 15. The steering angle sensor 13 detects the steering angle, that is, the rotation angle of the steering wheel. The steering angle can be obtained by differentiating the steering angle, and the rotation speed of the steering wheel can be obtained. Thus, the rotation direction can be obtained. The steering angle thus detected is also input to the ECU 15.

The CPU 16 provided in the ECU 15 determines the current command value to be sent to the motor drive circuit 18 based on the steering torque, the vehicle speed and the steering angle input via the interface 17, and the motor drive circuit 18 is determined. Output.

The motor drive circuit 18 outputs a drive current corresponding to the current command value sent from the CPU 16 to the motor M by the PWM circuit. As a result, the motor M generates an assist torque for assisting the steering force or a torque for restoring the steering wheel.

Next, the ECU 15 and the motor drive circuit 1
8 and the configuration and operation of the motor control unit 20 that controls the motor M will be described with reference to FIGS. Figure 1
As shown in FIG. 2, the electric power steering apparatus 10 mainly includes a phase compensation unit 21, a cut-and-return determination unit 22, a cut-assist map 23a, a return-assist map 23b, and a switching unit 2.
4, PI controller 25, motor current detector 27, adder 2
It is composed of nine. Note that, except for the motor current detection unit 27, these are realized by software that is arithmetically processed by the CPU 16 of the ECU 15 described above.

The phase compensator 21 advances the phase of the torque sensor output output from the torque sensor 11, and performs a phase advance process for speeding up the response to the torque sensor output. The cut-in / return-back determination unit 22 determines whether the steering wheel is in the cut-in state or the return-direction, and determines whether the torque sensor output is output from the torque sensor 11 or the steering wheel rotation direction based on the steering angle output from the steering angle sensor 13. A determination process is performed based on the determination.

That is, as shown in FIG. 3, the torque sensor 1
If the sign of the sensor output (the sign of the steering torque) output from 1 and the sign of the sensor output output from the steering angle sensor 13 (the sign of the rotation direction) are the same sign, It is determined to be "cut", and if both codes are different, it is determined to be "cutback". The sensor output output from the torque sensor 11 is given a plus sign (right direction) or a minus sign (left direction) depending on the torsion direction of the torsion bar. Further, the sensor output output from the steering angle sensor 13 is given a plus sign (right direction) or a minus sign (left direction) depending on the rotation direction of the steering wheel.

The cut assist map 23a and the return assist map 23b determine the assist torque for supplementing the steering force from the steering torque. For example, the vehicle speed is 40 km.
When / h, the setting is made as shown in FIG. That is, as shown in FIG. 4 (A), a characteristic associated with the torque sensor output (TS) so that a predetermined assist torque (Tmo) (current command value) is generated is given. The cut-in assist map 23a is set so as to draw a curve plotted with a white circle (◯), and the cut-back assist map 23b is set so as to draw a curve plotted with a black triangle (▲) at the time of switchback.

As a result, unlike the conventional single assist map shown in FIG. 4 (B), different assist maps, that is, a cut assist and a return assist, are provided depending on the steering direction of the steering wheel. Since the assist map 23a and the turning-back assist map 23b are provided, when the steering wheel is turned, the current command value can be determined based on the cutting-assist map 23a and the steering torque, and when the steering wheel is turned back. The current command value can be determined based on the switchback assist map 23b and the steering torque.

That is, the assist torque (current command value) for reverting is greater than the assist torque (current command value) for cutting.
The steering gear box or the like is provided with an assist characteristic close to that of a power steering device using hydraulic power.

The switching unit 24 selects the cutting assist map 23a or the returning assist map 23b based on the steering direction of the steering wheel determined by the notch returning determination unit 22. If the determination result by the cut-back return determination unit 22 is "cut", the cut assist map 23a is selected, and if the determination result is "return", the switch back assist map 23b is selected to perform the switching process. .

Here, the cut-in / cut-back determination unit 2 described above is used.
2, each processing by the cutting assist map 23a, the cutting back assist map 23b and the switching unit 24 will be described as a series of current command value calculation processing based on the flowchart shown in FIG. The steering torque acquisition process in step S101 obtains a sensor output from the torque sensor 11, and the steering torque code detection process in step S102 is performed based on the sensor output. In the steering torque code detection process, as described above, a plus sign (right direction) or a minus sign (left direction) is acquired from the torsion direction of the torsion bar.

The steering angle acquisition processing in step S103 is to obtain a sensor output from the steering angle sensor 13, and the rotation direction code detection processing in step S104 is performed based on this sensor output. In the rotation direction code detection process, a plus sign (right direction) or a minus sign (left direction) code is acquired from the rotation direction of the steering wheel as described above. Note that step S103 and step S104 are processed in parallel with step S101 and step S102.

In step S105, step S102
Based on the steering torque code detected by the above and the rotation direction code detected in step S104, it is determined whether the two codes are the same code or different codes. That is, it is a process of determining whether the steering wheel is in the cut-in state or the return-direction by the determination method described with reference to FIG.

If the sign is the same, the steering wheel is in the cut state, so the cut assist map 23a is selected in step S106. If the sign is different, the steering wheel is in the return state, so the step S107 is executed. The return assist map 23b is selected.

Then, in step S108, step S
Assist calculation is performed based on the assist map selected in step 106 or step S107 and the steering torque acquired in step S101 to determine the current command value to be output to the PI control unit 25. The cutting assist map 23a and the turning back assist map 23b described above are provided.
The switching unit 24 and the switching unit 24 correspond to the "current command unit" described in the claims.

The PI control unit 25 performs proportional-plus-integral control based on the difference between the motor current and the current command value calculated and output from the adding unit 29 located in the preceding stage, and the control output is the motor drive circuit 18. To be sent to. The motor current detection unit 27 is a current sensor that detects the motor current flowing through the motor M, and sends the sensor output to the addition unit 29.

As described above, according to the motor control unit 20 of the electric power steering apparatus 10 according to this embodiment, the switching unit 24 is based on the steering direction of the steering wheel determined by the cut-and-return determination unit 22. The current command value is determined based on the cutting assist map 23a or the turning back assist map 23b selected by, and the steering torque detected by the torque sensor 11. Thus, when the steering wheel is turned, the current command value is determined based on the turning assist map 23a and the steering torque, and when the steering wheel is turned back, the current command value is determined based on the turning back assist map 23b and the steering torque. Because it is possible, steering feeling at the time of cutting (build-up feeling) and steering feeling at the time of switching back (feeling returned)
It is possible to set a good motor current corresponding to and respectively, and thus an assist torque. Therefore, there is an effect that it is possible to improve the steering feeling both when the steering wheel is turned in and out.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. The electric power steering apparatus according to the present embodiment has the same configuration as the electric power steering apparatus 10 according to the first embodiment described above, but EC
The motor control unit 30 that controls the U15, the motor drive circuit 18, and the motor M is different from the above-described motor control unit 20 in that the motor control unit 30 is provided with a smoothing process 32 corresponding to a delay unit. Therefore, the same components as those of the motor control unit 20 of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 6, the motor control unit 30 is
A smoothing process 32 is provided between the cut-and-cut-back determination unit 22 and the switching unit 24. The smoothing process 32 is performed by the cutting assist map 23a and the returning assist map 23b.
It is provided for the purpose of reducing the speed for selecting to a predetermined value or less. For example, the transfer function G shown in the following equation (1)
Is based on. As a result, the operation of a low-pass filter (hereinafter referred to as "LPF") capable of removing a frequency component (hereinafter referred to as "predetermined high-frequency component") higher than the cutoff frequency fc represented by the equation (2) is calculated. Can be realized by In addition, the first described with reference to FIG.
In the series of current command value calculation processes according to the embodiment, the smoothing process 32 includes steps S106 and S1.
This is executed between 07 and step S108.

G = 1 / (Ts + 1) (1) fc = 1 / 2πT (2) where T is a sampling time and s is an operation symbol (time differential symbol). is there.

That is, the smoothing process 3 set in this way
2 can reduce the speed for selecting the cut assist map 23a and the return assist map 23b to (1 / fc) seconds or less, and thus the detected steering torque and the rotation direction of the steering wheel determine the selection of both maps. Even when the values are in the vicinity of the values or when the steering torque or the rotational direction contains the fluctuation component having the response speed exceeding (1 / fc) seconds, these can be removed by the action of the LPF. .

For example, as shown in FIG. 7 (B), if the steering torque or the steering wheel rotation direction switching determination value is in a hunting state in which it frequently fluctuates around a threshold value Th, the influence thereof is exerted. In response to this, switching of the assist map by the switching unit 24 occurs. Therefore, it can be seen that the assist command value (current command value) also frequently changes to include a noise component (lower column in the figure).

On the other hand, as shown in FIG. 7 (A), in the motor control unit 30 of the second embodiment, the cutting assist map 23 selected by the switching unit 24 by the smoothing process 32.
a and the speed for selecting the return assist map 23b are reduced to (1 / fc) seconds or less, so that the detected steering torque or the rotation direction of the steering wheel is in the vicinity of the threshold value Th that determines the selection of both maps. Even if the steering torque or the rotational direction contains a fluctuation component having a response speed exceeding (1 / fc) seconds or less, it can be removed by the action of the LPF by the smoothing process 32. Yes (upper column in the figure). As a result, it is possible to stably select the cutting assist map 23a and the cutting back assist map 23b (lower column in the figure). Therefore, there is an effect that it is possible to further improve the steering feeling both when the steering wheel is turned in and out.

The smoothing process 32 is performed by the equation (1) described above.
The transfer function G is not limited to the transfer function G, and if the speed for selecting the cutting assist map 23a (cutting map) and the switching back assist map 23b (switching back map) can be reduced to a predetermined value or less, for example, a weighted average Alternatively, a moving average algorithm or a digital filter may be used, and the same operation and effect as those described above can be obtained.

[Third Embodiment] Next, a third embodiment of the present invention will be described with reference to FIG. The electric power steering apparatus according to the present embodiment has the same configuration as the electric power steering apparatus 10 according to the first embodiment described above, but a motor control that controls the ECU 15, the motor drive circuit 18, and the motor M. The motor control unit 20 differs from the above-described motor control unit 20 in that the unit 40 includes an assist map 42 and a function calculation unit 44 instead of the cutting assist map 23a and the switching back assist map 23b. Therefore, the same components as those of the motor control unit 20 of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 8, the assist map 42
Is a cutting assist map having substantially the same characteristics as the cutting assist map 23a described above.

On the other hand, the function calculation unit 44 is provided between the assist map 42 and the switching unit 24, and for example, the following equation
The function of (3) is processed. Cutback assist command value = vehicle speed coefficient × cutting assist command value (3) Here, the vehicle speed coefficient is a value that varies depending on the vehicle speed detected by the vehicle speed sensor 12, and is 2.0 when the vehicle speed is 40 km / h, for example. Is set to.

As a result, a cutback assist command value (switchback current command value) obtained by multiplying the characteristics of the cut assist map 23a by 2.0 is obtained, so that the black triangle (▲) shown in FIG. 4 (A) is obtained. It is possible to generate a cutback assist map of the curve plotted in step 1 by a functional operation.

That is, the motor control unit 4 of the third embodiment
At 0, when the steering wheel is cut,
The cutting assist command value (cutting current command value) can be determined based on the cutting assist map 23a and the steering torque, and when the steering wheel is turned back, the cutting assist command value is calculated by the above formula (3). Since it is possible to determine the switch-back assist command value, it is possible to obtain a good motor current corresponding to the steering feeling (build-up feeling) at the time of cutting and the steering feeling (return feeling) at the time of switching-back, and thus the assist torque. Can be set. In addition to this, the storage space of the memory device for storing the switchback assist map 23b and the like can be reduced because the switchback assist map 23b is not required. Therefore, in addition to the effect of improving the steering feeling both when the steering wheel is turned in and out, the device cost is further reduced.

[Fourth Embodiment] Next, a fourth embodiment of the present invention will be described with reference to FIGS. The electric power steering apparatus according to the present embodiment has the same configuration as the electric power steering apparatus 10 according to the first embodiment described above, but the ECU
15. The motor control unit 50 that controls the motor drive circuit 18 and the motor M includes an assist map 52, a target gain setting unit 54, and a smoothing process 56 in place of the cutting assist map 23a, the switching back assist map 23b, and the switching unit 24. The difference from the above-described motor control unit 20 is that the motor control unit 20 is provided with. Therefore, the motor control unit 20 of the first embodiment
Constituent parts substantially the same as those of FIG.

As shown in FIG. 9, the motor controller 50
An assist map 52 is provided in the subsequent stage of the phase compensating unit 21, a target gain setting unit 54 is provided in the subsequent stage of the cut-and-return judging unit 22, and a smoothing process 56 is provided in the subsequent stage. The multiplication unit 58 that multiplies the outputs of the assist map 52 and the smoothing process 56 is located in the preceding stage of the addition unit 29.

The assist map 52 is an assist map for cutting having substantially the same characteristics as the above-described cut assist map 23a, and can determine a reference assist command value (reference current command value).

The target gain setting unit 54 sets a predetermined cutting gain or a predetermined cutting back gain based on the steering direction of the steering wheel determined by the cutting back switching determination unit 22. For example, if the determination result by the cut-back return determination unit 22 is “cut”, the cut gain 1.0 is set, and if the determination result is “cut back”, the return gain 1.2 is set. Performs gain setting processing.

The smoothing process 56 is the same as the smoothing process 32 of the motor control unit 30 according to the second embodiment described above, and is set by the target gain setting unit 54 for setting the cutting gain and the switching back gain. It is provided for the purpose of reducing the speed below a predetermined value. Note that, specifically, there are the transfer function G by the above-mentioned formula (1), the one by the weighted average or moving average algorithm, the one by the digital filter, etc., and they have the same operation as the LPF.

The multiplying unit 58 multiplies the reference current command value output from the assist map 52 by the cut-in gain or the cut-back gain processed by the smoothing process 56. As a result, the reference current command value output from the assist map 52 is output to the addition unit 29 as a cutting current command value or a switching back current command value amplified by the cutting gain or the switching back gain.

For example, in the case of the fourth embodiment, since the cutting gain 1.0 and the switching back gain 1.2 are set,
A current command value (assist command value) as shown in FIG. 10 is output from the multiplication unit 58. The characteristic of the current command value shown in FIG. 10 is the same as the current command value (assist command value) according to the first embodiment described with reference to FIG. ) Is set to have a hysteresis characteristic such that it becomes larger than the current command value (assist command value) for cutting.

That is, the motor controller 5 of the fourth embodiment.
At 0, when the steering wheel is cut,
The current command value (assist torque) determined by the assist map 52 from the steering torque is amplified by the cutting gain set to 1.0 to determine the cutting current command value. When the steering wheel is turned back, steering is performed. Since the current command value (assist torque) determined by the assist map 52 from the torque can be amplified by the switchback gain set to 1.2, which is larger than the cutoff gain, the switchback current command value can be determined. It is possible to set a good motor current and thus an assist torque corresponding to the steering feeling (build-up feeling) at the time of cutting and the steering feeling (return feeling) at the time of returning. Therefore, there is an effect that it is possible to improve the steering feeling both when the steering wheel is turned in and out.

Further, the motor controller 50 of the fourth embodiment.
Then, since the speed set by the target gain setting unit 54 for setting the cut-in gain and the cut-back gain is reduced to a predetermined value or less by the anneal processing 56, as shown in FIG. "Return", or "return" to "cut", to eliminate spike-like sudden change regions (waveforms within α in Fig. 11 (C)) that may occur in the assist command value when the steering angle changes abruptly. You can This makes it possible to generate continuous assist command values, as shown in FIG. 11 (B). Therefore, there is an effect that it is possible to further improve the steering feeling both when the steering wheel is turned in and out.

[Fifth Embodiment] Next, a fifth embodiment of the present invention will be described with reference to FIGS. 12 and 13. The electric power steering apparatus according to the present embodiment has the same configuration as the electric power steering apparatus 10 according to the first embodiment described above, and is substantially the same as the motor control unit 50 of the fourth embodiment described above. Although the configuration is adopted, it differs from the motor control unit 50 in that the sensor output 62 of the vehicle speed sensor 12 is input to the target gain setting unit 54. Therefore, the same components as those of the motor control unit 50 of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. In the present embodiment, the fourth
Similar to the embodiment, the assist map 52 is used, and the assist map 52 corresponds to “another map” that is neither the cut map nor the cut back map.

As shown in FIG. 12, the vehicle speed sensor output 62 output from the vehicle speed sensor 12 is input to the target gain setting unit 64 located between the depth of cut-back determination unit 22 and the smoothing process 56. . As a result, when the vehicle speed detected by the vehicle speed sensor 12 is substantially zero, the target gain setting unit 64 sets the predetermined cutback gain regardless of the steering direction of the steering wheel determined by the cutback return determination unit 22. Set to a gain value or less.

That is, in the target gain setting section 64, as shown in FIG.
The gain setting process shown in is performed. In step S201, the determination flag output from the cutback / return determination unit 22 is acquired, and in the subsequent step S202, the determination flag value is detected. The determination flag value is set to "0" at the time of cutting and "1" at the time of switching back.

On the other hand, step S201 and step S
Steps S203 and 204 that are processed in parallel with 202
Then, the vehicle speed signal which is the vehicle speed sensor output 62 is acquired from the vehicle speed sensor 12, and the vehicle speed value is detected.

Then, in step S205, it is determined whether or not the vehicle speed value is zero, and if the vehicle speed value is zero (S2
If Yes in 05), the target gain is set to G0 (for example, 1.0) in step S206. On the other hand, if the vehicle speed value is not zero (No in S205), it is determined in the next step S207 whether or not the determination flag value is set to "0".

If the determination flag value is set to "0" by the determination of the determination flag value in step S207 (Yes in S207), the target gain is set to G0 (for example, 1.0) in step S208. On the other hand, if the determination flag value is not set to "0" (No in S207), the target gain is set to G1 (for example 1.2) in step S209.

When the target gain setting processing in steps S206, S208, and S209 is completed, this gain setting processing is ended.

In the above-described motor control unit 60, when the vehicle value detected by the vehicle speed sensor 12 is zero, the target gain setting unit 64 is irrespective of the steering direction of the steering wheel determined by the cut-and-return determination unit 22. Cutback gain is the value of cut-in gain (1.2) or less (1.0)
Therefore, the switch-back gain selected when the steering wheel is switched back can be set to a value lower than the cut-in gain. With this, when the vehicle value is substantially zero, it is possible to prevent self-excited oscillation that is likely to occur at the time of switchback due to the target gain being set higher than necessary. Therefore, even if the vehicle value is almost zero, there is an effect that the steering feeling of both the turning and turning back of the steering wheel can be further improved. In each of the above embodiments, the steering angle sensor 13 is used to obtain the rotation direction of the steering wheel, but other means can be adopted. When using the steering angle sensor 13,
The rotation speed is obtained based on the steering angle obtained from the sensor 13, and the rotation direction is obtained from this rotation speed. However, a known voltage that uses the motor terminal voltage and the motor actual current without using the steering angle sensor. It is also possible to estimate the rotational speed of the steering wheel from the equation and obtain the rotational direction from this estimated value.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main electrical configuration of a motor control unit in an electric power steering apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing main electrical configurations of an ECU and a motor drive circuit shown in FIG.

FIG. 3 is an explanatory diagram showing a determination table by a cut-and-return determination unit that constitutes the motor control unit of the first embodiment.

FIG. 4 (A) is an explanatory diagram showing an example of an assist map by the motor control unit of the first embodiment, and FIG. 4 (B) is a motor control unit of a conventional electric power steering apparatus. It is explanatory drawing which shows the example of a single assist map.

FIG. 5 is a flowchart showing a flow of current command value calculation processing by the motor control unit of the first embodiment.

FIG. 6 is a block diagram showing a main electrical configuration of a motor control unit in an electric power steering apparatus according to a second embodiment of the present invention.

7A and 7B are explanatory diagrams showing the effect of the smoothing process of the motor control unit of the second embodiment. FIG. 7A shows the case with the smoothing process, and FIG. 7B shows the case without the smoothing process. The characteristic diagram of each switching determination value and assist command value is shown.

FIG. 8 is a block diagram showing a main electrical configuration of a motor control unit in an electric power steering apparatus according to a third embodiment of the present invention.

FIG. 9 is a block diagram showing a main electrical configuration of a motor control unit in an electric power steering apparatus according to a fourth embodiment of the present invention.

FIG. 10 is a characteristic diagram of an assist command value by a target gain setting unit of the motor control unit of the fourth embodiment.

11A and 11B are explanatory diagrams showing the effect of the smoothing process of the motor control unit according to the fourth embodiment, FIG. 11A is a change example of the steering angle, and FIG. 11B is a steering with the smoothing process. FIG. 11C is a characteristic diagram of the assist command value with respect to the angle, and FIG. 11C is a characteristic diagram of the assist command value with respect to the steering angle without the smoothing process.

FIG. 12 is a block diagram showing a main electrical configuration of a motor control unit in an electric power steering apparatus according to a fifth embodiment of the present invention.

FIG. 13 is a flowchart showing the flow of gain setting processing by a target gain setting unit of the motor control unit of the fifth embodiment.

FIG. 14 is a block diagram showing a main electrical configuration of a motor control unit by a conventional electric power steering apparatus.

[Explanation of symbols]

10 Electric Power Steering Device 11 Torque Sensor (Steering Torque Detection Means) 12 Vehicle Speed Sensor 13 Steering Angle Sensor (Rotation Direction Detection Means) 15 ECU 18 Motor Drive Circuits 20, 30, 40, 50, 60 Motor Control Unit 21 Phase Compensation Part 22 Cut-back return determination unit (cut-back return determination means) 23a Cut-assist map (cut-out map, current command means) 23b Cut-back assist map (cut-back map, current command means) 24 Switching section (current command means) 25 PI Control section (motor control means) 27 Motor current detection section (motor control means) 29 Addition section (motor control means) 32 Smoothing processing (delay means) 42 Assist map (cutting map, current command means) 44 Function calculation section (current Command means) 52 Assist map (reference map, current command means) 54, 64th Gain setting unit (current command means) 56 annealing process 58 multiplier unit (current instruction means)

Claims (6)

[Claims] 1. An electric power steering apparatus including a motor for compensating a steering force based on a steering torque generated on a steering shaft, comprising: steering torque detecting means for detecting the steering torque; and rotation of the steering wheel. A rotation direction detecting means for detecting a direction, and a steering torque detected by the steering torque detecting means and a rotation direction of the steering wheel detected by the rotation direction detecting means for determining whether the steering wheel is cut or turned back. Depth cutback determination means, a depth map or a reversion map capable of determining an assist torque for supplementing the steering force from the steering torque selected based on the steering direction of the steering wheel determined by the depth cutback determination means, The steering torque detected by the steering torque detecting means And a current command means for determining a current command value for the motor, a current detection means for detecting a motor current flowing through the motor, and a current command value and the current determined by the current command means. An electric power steering apparatus comprising: a motor control unit that feedback-controls the motor based on a deviation from the motor current detected by the detection unit. 2. The electric power steering apparatus according to claim 1, wherein the current command means includes a delay means for reducing a speed for selecting the cut-in map and the cut-back map to a predetermined value or less. 3. An electric power steering apparatus including a motor for compensating a steering force based on a steering torque generated on a steering shaft, comprising: steering torque detecting means for detecting the steering torque; and rotation of the steering wheel. A rotation direction detecting means for detecting a direction, and a steering torque detected by the steering torque detecting means and a rotation direction of the steering wheel detected by the rotation direction detecting means for determining whether the steering wheel is cut or turned back. Depth cutback determination means, a cutting current command value to the motor to be determined based on the steering torque detected by the steering torque detecting means and a cutting map capable of determining an assist torque that supplements the steering force from the steering torque, And before making a decision by applying a predetermined calculation to this cutting current command value A current command means for selecting one of a cut-back current command value to the motor based on the steering direction of the steering wheel determined by the cut-and-return determination means, and a current detection for detecting a motor current flowing through the motor. Means, and motor control means for feedback-controlling the motor based on a deviation between a current command value determined by the current command means and a motor current detected by the current detection means. Electric power steering device. 4. An electric power steering apparatus including a motor for compensating a steering force based on a steering torque generated on a steering shaft, comprising: steering torque detecting means for detecting the steering torque; and rotation of the steering wheel. A rotation direction detecting means for detecting a direction, and a steering torque detected by the steering torque detecting means and a rotation direction of the steering wheel detected by the rotation direction detecting means for determining whether the steering wheel is cut or turned back. Depth cutback determination means, (1) a reference map capable of determining an assist torque that supplements the steering force from the steering torque, (2) selection based on the steering direction of the steering wheel determined by the depthwise cutback determination means Amplifies the assist torque,
A current command value to the motor is determined based on a predetermined cut-back gain or a predetermined cut-back gain set to be larger than the predetermined cut-in gain and (3) the steering torque detected by the steering torque detection means. Current command means, current detection means for detecting a motor current flowing through the motor, and the motor based on a deviation between a current command value determined by the current command means and a motor current detected by the current detection means. And a motor control means for feedback controlling the electric power steering apparatus. 5. A speed sensor for detecting a vehicle speed is provided,
When the vehicle speed detected by the vehicle speed sensor is substantially zero, the current commanding means sets the predetermined turning-back gain to the predetermined turning-back gain regardless of the turning direction of the steering wheel determined by the turning-back turning-back determination means. The electric power steering apparatus according to claim 4, wherein the cutting gain value is set to a value equal to or less than the cutting gain. 6. A vehicle having a speed sensor for detecting a vehicle speed,
When the vehicle speed detected by the vehicle speed sensor is substantially zero, the current command means is one of the cut map, the cutback map, or another map that is neither the cut map nor the cutback map. The electric power steering apparatus according to claim 1 or 2, wherein a current command value for the motor is determined based on one of them and the steering torque detected by the steering torque detecting means.