JP3891258B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus including a motor that supplements a steering force based on a steering torque generated in a steering shaft.
[0002]
[Prior art]
The conventional motor control unit 90 of the electric power steering apparatus employs a configuration as shown in FIG. That is, the sensor output output from the torque sensor that detects the steering torque is input to the phase compensator 91, and the phase is advanced to speed up the response to the torque sensor output, and then input to the assist map 93. . In the assist map 93, a current command value to be transmitted corresponding to a 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 determined in this way is subjected to predetermined proportional-integral control by the PI control unit 95 via the adding unit 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.
[0003]
On the other hand, the motor current flowing through the motor is detected by the motor current detecting unit 97 and then fed back to the adding unit 99 provided in the preceding stage of the PI control unit 95, so that the current command value and the detected value of the motor current are Based on the deviation, the PI control unit 95 performs proportional-integral control so that they match. Thereby, since the motor current given to the motor is feedback-controlled, it is possible to cause the motor to generate assist torque suitable for the steering torque generated by the steering wheel.
[0004]
[Problems to be solved by the invention]
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 same (single) regardless of the rotation direction of the steering wheel, that is, whether the steering wheel is turned or not turned back. One assist map) (see FIG. 4B). For this reason, one of the steering sensations at the time of turning the steering wheel (build-up feeling) and the steering sensation at the time of turning back (feeling of returning) has been preferentially set. Therefore, there is a problem that it is difficult to set both the steering feeling when the steering wheel is turned and the steering feeling when the steering wheel is turned back.
[0005]
The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide an electric power steering apparatus that can improve the steering feeling of both turning and turning back of a steering wheel. It is in.
[0006]
[Means for solving the problems and functions and effects of the invention]
  In order to achieve the above object, in the electric power steering apparatus according to claim 1,
  An electric power steering apparatus including a motor that supplements a steering force based on a steering torque generated in a steering shaft,
  Steering torque detection means for detecting the steering torque;
  A rotation direction detecting means for detecting a rotation direction of the steering wheel;
  A cut-in / back-out determining unit that determines whether the steering wheel is turned in or out based on a steering torque detected by the steering torque detecting unit and a rotation direction of the steering wheel detected by the rotation direction detecting unit;
  A cutting map or a returning map that is selected based on the turning direction of the steering wheel determined by the cutting / cutback determining means and that can determine an assist torque that supplements the steering force from the steering torque, and detected by the steering torque detecting means Current command means for determining a current command value to the motor based on the steering torque,
  Current detecting means for detecting a motor current flowing in the motor;
  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.,
  The current command means includes
  Delay means for delaying a time required for selecting the cut map and the switch back map to a predetermined time or moreIs a technical feature.
[0007]
  According to the first aspect of the present invention, the cutting / returning determining means determines whether the steering wheel is turned or not based on the steering torque detected by the steering torque detecting means and the rotational direction of the steering wheel detected by the rotational direction detecting means. To do. A cutting map or switching map that can be selected by the current command means based on the steering wheel turning direction determined by the cutting / turning-back determination means and that can determine assist torque that supplements the steering force from the steering torque, and steering torque detection means The current command value to the motor is determined based on the steering torque detected by the above. Further, the motor current flowing to the motor is detected by the current detection means, and the motor is fed back by the motor control means 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.The delay means included in the current command means delays the time required to select the cut map and the switch back map to a predetermined time or more.
[0008]
  That is, the current command value determined by the current command means is based on the cutting map or the return map selected based on the steering wheel turning direction and the steering torque. Thus, the current command value can be determined based on the cutting map and the steering torque when the steering wheel is turned, and the current based on the switching map and the steering torque when the steering wheel is turned back. Since the command value can be determined, it is possible to set a good motor current and thus assist torque corresponding to the steering feeling at the time of cutting (build-up feeling) and the steering feeling at the time of returning (return feeling). . Therefore, there is an effect that it is possible to improve the steering feeling of both the turning and turning back of the steering wheel.In addition, the delay means delays the time required for selecting the cut map and the switchback map selected by the current command means to a predetermined time or more, so that the detected steering torque and the direction of rotation of the steering wheel are selected in both maps. The low-pass filter functions by the delay means even when it is close to the threshold value that determines the speed, or when the steering torque or the rotational direction includes a fluctuation component having a response speed exceeding the predetermined value. These can be removed. Thereby, selection of a cutting map and a cutback map can be performed stably. Therefore, there is an effect that the steering feeling of both the turning and turning back of the steering wheel can be further improved.
[0009]
  According to a second aspect of the present invention, there is provided the electric power steering apparatus according to the first aspect, further comprising a speed sensor for detecting a vehicle speed, wherein the vehicle speed detected by the vehicle speed sensor is substantially zero. One day,
  The current command means includes any one of the cutting map, the switching back map, or another map that is neither the cutting map nor the switching map, and the steering torque detected by the steering torque detection means. And determining a current command value to the motor based on the above.
[0010]
  In the invention of claim 2, when the vehicle speed detected by the vehicle speed sensor is substantially zero, the current command means is a cutting map, a switching map, or another map that is neither a cutting map nor a switching map. Since the current command value to the motor is determined based on any one of them and the steering torque detected by the steering torque detecting means, when the vehicle speed is substantially zero, when the steering wheel is cut, the switch back Regardless of the time, the current command value to the motor can be determined based on one specific map and the steering torque. As a result, it is possible to prevent self-excited oscillation that is likely to occur when the steering wheel is switched back when the vehicle speed is substantially zero. Therefore, even when the vehicle speed is substantially zero, there is an effect that the steering feeling of both the turning and turning back of the steering wheel can be further improved.
[0011]
Furthermore, in the electric power steering apparatus according to claim 3,
An electric power steering apparatus including a motor that supplements a steering force based on a steering torque generated in a steering shaft,
Steering torque detection means for detecting the steering torque;
A rotation direction detecting means for detecting a rotation direction of the steering wheel;
A cut-in / back-out determining unit that determines whether the steering wheel is turned in or out based on a steering torque detected by the steering torque detecting unit and a rotation direction of the steering wheel detected by the rotation direction detecting unit;
A cutting current command value to the motor determined based on a cutting map that can determine an assist torque that supplements the steering force from the steering torque, and a steering torque detected by the steering torque detecting means, and the cutting current command value Current command means for selecting one of the switchback current command values to the motor determined by performing a predetermined calculation on the basis of the turning direction of the steering wheel determined by the cutback return determination means;
Current detecting means for detecting a motor current flowing in the motor;
And a motor control unit that feedback-controls the motor based on a deviation between a current command value determined by the current command unit and a motor current detected by the current detection unit.
[0012]
According to the third aspect of the present invention, the cutting / returning determining means determines whether the steering wheel is turned or not based on the steering torque detected by the steering torque detecting means and the rotational direction of the steering wheel detected by the rotational direction detecting means. To do. Then, the current command means determines the assist torque for supplementing the steering force from the steering torque, the cut current command value to the motor determined based on the cut map that can determine the assist torque detected by the steering torque detection means, and the cut Any one of the switchback current command values to the motor determined by performing a predetermined calculation on the current command value is selected based on the steering wheel turning direction determined by the cutback return determining means. Further, the motor current flowing to the motor is detected by the current detection means, and the motor is fed back by the motor control means 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.
[0013]
In other words, the current command value determined by the current command means is selected based on the turning direction of the steering wheel, and the cut-off current command value and the return current to the motor determined by performing a predetermined calculation on the cutting current command value. It is a 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. Therefore, it is possible to determine the return current command value, so that a good motor current and therefore assist torque can be set corresponding to the steering feeling at the time of cutting (build-up feeling) and the steering feeling at the time of returning (return feeling). In addition to being able to do so, the storage space of the storage device for storing the switchback map and the like can be reduced by the amount that the switchback map is not required. Therefore, in addition to the effect of improving the steering sensation of both the turning and turning back of the steering wheel, there is an effect of further reducing the device cost.
[0014]
In the electric power steering apparatus according to claim 4,
An electric power steering apparatus including a motor that supplements a steering force based on a steering torque generated in a steering shaft,
Steering torque detection means for detecting the steering torque;
A rotation direction detecting means for detecting a rotation direction of the steering wheel;
A cut-in / back-out determining unit that determines whether the steering wheel is turned in or out based on a steering torque detected by the steering torque detecting unit and a rotation direction of the steering wheel detected by the rotation direction detecting unit;
(1) a reference map capable of determining an assist torque that supplements the steering force from the steering torque; (2) amplifying the assist torque selected based on the turning direction of the steering wheel determined by the cut-in / turn-back determining means A current command value to the motor is determined based on a predetermined cutting gain or a predetermined switching back gain set to be larger than the predetermined cutting gain and (3) the steering torque detected by the steering torque detecting means. Current command means for
Current detecting means for detecting a motor current flowing in the motor;
And a motor control unit that feedback-controls the motor based on a deviation between a current command value determined by the current command unit and a motor current detected by the current detection unit.
[0015]
In a fourth aspect of the invention, the cut / return determination means determines whether the steering wheel is cut or returned 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. To do. Then, by the current command means, (1) a reference map that can determine the assist torque that supplements the steering force from the steering torque, and (2) the assist torque selected based on the turning direction of the steering wheel determined by the cut-in / turn-back determining means. Based on the predetermined cutting gain to be amplified or the predetermined switching gain set larger than the predetermined cutting gain, and (3) the steering torque detected by the steering torque detecting means, the current command value to the motor is decide. Further, the motor current flowing to the motor is detected by the current detection means, and the motor is fed back by the motor control means 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.
[0016]
In other words, the current command value determined by the current command means is (1) a reference map that can determine the assist torque that supplements the steering force from the steering torque, and (2) the assist torque that is selected based on the turning direction of the steering wheel. This is based on the predetermined cutting gain or a predetermined switching gain set larger than the predetermined cutting gain, and (3) the steering torque detected by the steering torque detecting means. Thereby, when the steering wheel is turned, the assist torque determined from the steering torque based on the reference map is amplified by a predetermined cutting gain to determine the current command value, and when the steering wheel is turned back, the steering torque is Since the assist torque determined from the reference map is amplified by a predetermined switchback gain that is set to be larger than the predetermined cutting gain, the current command value can be determined. ) And the steering feeling (return feeling) at the time of switching back, a good motor current and thus assist torque can be set. Therefore, there is an effect that it is possible to improve the steering feeling of both the turning and turning back of the steering wheel.
[0017]
Furthermore, in the electric power steering apparatus according to claim 5, in claim 4,
Having a speed sensor for detecting the vehicle speed, and when the vehicle speed detected by the vehicle speed sensor is substantially zero,
The current command means sets the predetermined switchback gain to a value equal to or less than the predetermined switch gain regardless of the turning direction of the steering wheel determined by the switchback determination section. Characteristic.
[0018]
According to the fifth aspect of the present invention, when the vehicle speed detected by the vehicle speed sensor is substantially zero, the current command means has a predetermined return gain regardless of the steering wheel turning direction determined by the turning back / return determining means. Therefore, the predetermined cutback gain selected when the steering wheel is turned back can be set low to a predetermined cut gain value or a lower value. As a result, it is possible to prevent self-excited oscillation that is likely to occur at the time of switching back when the vehicle speed is substantially zero. Therefore, even when the vehicle speed is substantially zero, there is an effect that the steering feeling of both the turning and turning back of the steering wheel can be further improved.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an electric power steering apparatus of the present invention will be described 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.
[0022]
[First embodiment]
First, the main electrical configuration of the electric power steering apparatus will be described with reference to FIG.
As shown in FIG. 2, the electric power steering apparatus 10 according to this embodiment mainly includes a steering wheel, a steering shaft coupled to the steering wheel, a torque sensor 11, a vehicle speed sensor 12, and a steering angle sensor. ECU 15 composed of a sensor group 13 and the like, a CPU 16, an interface 17 and the like, a motor drive circuit 18 controlled by the ECU 15, a motor M connected to the motor drive circuit 18 and capable of generating assist torque, and the motor M And a steering gear box that is driven by the assist torque. The steering wheel, steering shaft and steering gear box are not shown.
[0023]
The torque sensor 11 detects a steering torque, and is detected based on a torsion amount of a torsion bar or the like that connects an input shaft connected to a steering wheel of a vehicle and an output shaft connected to a steering mechanism so as to be relatively rotatable. is doing. The detected steering torque is input to the ECU 15.
[0024]
The vehicle speed sensor 12 detects the vehicle speed, and the detected vehicle speed 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, and can obtain the rotation speed of the steering wheel by differentiating the steering angle with time, and detects the increase or decrease of the angle. Thus, the rotation direction can be obtained. The detected steering angle is also input to the ECU 15.
[0025]
The CPU 16 provided in the ECU 15 determines a 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 outputs them to the motor drive circuit 18.
[0026]
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. Thereby, the motor M generates an assist torque for assisting the steering force, or generates a torque for restoring the steering wheel.
[0027]
Next, the configuration and operation of the motor control unit 20 that controls the ECU 15, the motor drive circuit 18, and the motor M will be described with reference to FIGS.
As shown in FIG. 1, the electric power steering apparatus 10 mainly includes a phase compensation unit 21, a cut-in / turn-out determination unit 22, a cut-in assist map 23 a, a switch-back assist map 23 b, a switching unit 24, and a PI control unit 25. The motor current detection unit 27 and the addition unit 29 are included. In addition, these are implement | achieved by the software calculated by CPU16 of ECU15 mentioned above except the motor electric current detection part 27. FIG.
[0028]
The phase compensation unit 21 advances the phase of the torque sensor output output from the torque sensor 11 and performs a phase advance process for increasing the response to the torque sensor output.
The cut-in / turn-back determining unit 22 determines whether the steering wheel is turned in or out, and the torque sensor output output from the torque sensor 11 and the rotation direction of the steering wheel based on the steering angle output from the steering angle sensor 13 are determined. A determination process based on the determination is performed.
[0029]
That is, as shown in FIG. 3, the combination of the sensor output code (steering torque code) output from the torque sensor 11 and the sensor output code (rotation direction code) output from the steering angle sensor 13 is combined. If both codes are the same code, it is determined as “cut-in”, and if both codes are different codes, it is determined as “switch-back”. 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 twist direction of the torsion bar. 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.
[0030]
The cutting assist map 23a and the switching back assist map 23b determine assist torque that supplements the steering force from the steering torque, and are set as shown in FIG. 4 (A), for example, when the vehicle speed is 40 km / h.
That is, as shown in FIG. 4 (A), a characteristic associated with the torque sensor output (TS) so as to generate a predetermined assist torque (Tmo) (current command value) is given. The cut assist map 23a is set so as to draw a curve plotted with white circles (◯), and the cutback assist map 23b is set so as to draw a curve plotted with black triangles (▲) at the time of cutback.
[0031]
Thus, unlike the conventional single assist map as shown in FIG. 4B, different assist maps depending on the turning direction of the steering wheel, that is, the cutting assist map 23a. Since the switchback assist map 23b is provided, the current command value can be determined based on the switch assist map 23a and the steering torque when the steering wheel is turned. When the steering wheel is turned back, the switchback assist map 23b is used. The current command value can be determined based on the assist map 23b and the steering torque.
[0032]
In other words, the steering assist torque (current command value) for switching back gives a hysteresis characteristic that is larger than the assist torque for cutting (current command value), and the steering assist characteristic close to that of a power steering device using hydraulic power is provided. It is given to gearboxes.
[0033]
The switching unit 24 selects the cutting assist map 23a or the switching back assist map 23b based on the turning direction of the steering wheel determined by the cutting / cutback determining unit 22. When the determination result by the cut / return determination unit 22 is “cut”, the cut assist map 23a is selected, and when the determination result is “cut back”, the switch assist map 23b is selected. .
[0034]
Here, each process by the above-described cut-in / turn-out determination unit 22, the cut-in assist map 23a, the switch-back assist map 23b, and the switching unit 24 will be described as a series of current command value calculation processes 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 this sensor output. In the steering torque sign detection process, as described above, a plus sign (right direction) or a minus sign (left direction) is obtained from the twist direction of the torsion bar.
[0035]
In the steering angle acquisition process in step S103, a sensor output is obtained from the steering angle sensor 13. Based on this sensor output, the rotation direction code detection process in step S104 is performed. In the rotation direction code detection process, as described above, a plus sign (right direction) or a minus sign (left direction) is acquired from the rotation direction of the steering wheel. Steps S103 and S104 are processed in parallel with steps S101 and S102.
[0036]
In step S105, based on the steering torque code detected in step S102 and the rotational direction code detected in step S104, it is determined whether both codes are the same code or different codes. That is, this is a process for determining whether the steering wheel has been turned in or returned by the determination method described with reference to FIG.
[0037]
If the sign is the same, the steering wheel is in the cut-in state. Therefore, the cut-in assist map 23a is selected in step S106. If the sign is different, the steering wheel is in the cut-back state. 23b is selected.
[0038]
In step S108, an assist calculation is performed based on the assist map selected in step S106 or step S107 and the steering torque acquired in step S101, and a current command value to be output to the PI control unit 25 is determined. The above-described cutting assist map 23a, switching back assist map 23b, and switching unit 24 correspond to “current command means” recited in the claims.
[0039]
The PI control unit 25 performs proportional-integral control based on the difference between the motor current and the current command value that is calculated and output from the addition unit 29 positioned in the preceding stage, and sends the control output to the motor drive circuit 18. Is.
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.
[0040]
As described above, according to the motor control unit 20 of the electric power steering apparatus 10 according to the present embodiment, the switching unit 24 selects the steering wheel turning direction determined by the cut-in / turn-back determination unit 22. The current command value is determined based on the turning assist map 23a or the turning back assist map 23b and the steering torque detected by the torque sensor 11. Thus, the current command value is determined based on the cutting assist map 23a and the steering torque when the steering wheel is turned on, and based on the switching back assist map 23b and the steering torque when the steering wheel is turned back. Therefore, it is possible to set a good motor current and an assist torque corresponding to the steering feeling at the time of cutting (build-up feeling) and the steering feeling at the time of returning (return feeling), respectively. Therefore, there is an effect that it is possible to improve the steering sensation of both the turning and turning back of the steering wheel.
[0041]
[Second Embodiment]
Next, a second 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 that of the electric power steering apparatus 10 according to the first embodiment described above, but the motor control that controls the ECU 15, the motor drive circuit 18, and the motor M is provided. The difference between the motor control unit 20 and the motor control unit 20 is that the unit 30 includes an annealing process 32 corresponding to a delay unit. Therefore, substantially the same components as those of the motor control unit 20 of the first embodiment are denoted by the same reference numerals and description thereof is omitted.
[0042]
As shown in FIG. 6, the motor control unit 30 includes an annealing process 32 between the cut-in / turn-back determination unit 22 and the switching unit 24.
This annealing process 32 is provided for the purpose of lowering the speed at which the cutting assist map 23a and the switching back assist map 23b are selected to a predetermined value or less. For example, the transfer function G shown in the following equation (1) is used. Based on. As a result, the operation of the 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 expression (2) is calculated. Can be realized. In the series of current command value calculation processes according to the first embodiment described with reference to FIG. 5, the smoothing process 32 is executed between steps S106 and S107, and step S108. is there.
[0043]
G = 1 / (Ts + 1) (1)
fc = 1 / 2πT (2)
Here, T indicates a sampling time, and s indicates an operation symbol (time differential symbol).
[0044]
  That is, the cutting assist map 23a and the cutback assist map 23b are selected by the annealing process 32 set in this way.Time required forLess than (1 / fc) secondsUpInDelayTherefore, when the detected steering torque and the rotation direction of the steering wheel are in the vicinity of the threshold for determining the selection of both maps, or the steering torque and the rotation direction have a response speed exceeding (1 / fc) seconds. Even when the fluctuation component is included, these can be removed by the action of LPF.
[0045]
For example, as shown in FIG. 7B, when the switching determination value of the steering torque or the rotation direction of the steering wheel is in a hunting state that frequently fluctuates around the threshold Th, the switching is affected by the influence. Switching of the assist map by the unit 24 occurs. Therefore, it can be seen that the assist command value (current command value) also fluctuates frequently and includes a noise component (lower column in the figure).
[0046]
  On the other hand, as shown in FIG. 7A, in the motor control unit 30 of the second embodiment, the cutting assist map 23a and the switchback assist map 23b selected by the switching unit 24 are selected by the annealing process 32. DoTime required forLess than (1 / fc) secondsUpInDelayTherefore, when the detected steering torque and the rotation direction of the steering wheel are in the vicinity of the threshold value Th that determines the selection of both maps, and the response speed exceeding (1 / fc) seconds or less in the steering torque and the rotation direction. Even when a fluctuation component having a value of is included, these can be removed by the action of the LPF by the annealing process 32 (upper column in the figure). Thereby, the selection of the cutting assist map 23a and the switching back assist map 23b can be performed stably (the lower column in the figure). Therefore, there is an effect that the steering feeling of both the turning and turning back of the steering wheel can be further improved.
[0047]
The annealing process 32 is not limited to the transfer function G according to the above-described equation (1), and the speed at which the cutting assist map 23a (cutting map) and the switching back assist map 23b (cutback map) are selected is predetermined. For example, a weighted average or moving average algorithm or a digital filter may be used as long as it can be reduced to a value below the value, and the same operations and effects as described above can be obtained.
[0048]
[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 that of the electric power steering apparatus 10 according to the first embodiment described above, but the motor control that controls the ECU 15, the motor drive circuit 18, and the motor M is provided. The difference from the motor control unit 20 described above is 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, substantially the same components as those of the motor control unit 20 of the first embodiment are denoted by the same reference numerals and description thereof is omitted.
[0049]
As shown in FIG. 8, the assist map 42 is a cutting assist map having substantially the same characteristics as the above-described cutting assist map 23a.
[0050]
On the other hand, the function calculation unit 44 is provided between the assist map 42 and the switching unit 24. For example, the function calculation unit 44 calculates a function of the following equation (3).
Switch-back assist command value = vehicle speed coefficient x 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 set to 2.0 when the vehicle speed is 40 km / h, for example.
[0051]
As a result, a switchback assist command value (switchback current command value) obtained by multiplying the characteristics of the switch assist map 23a by 2.0 is plotted with a black triangle (▲) shown in FIG. A curve cutback assist map can be generated by function calculation.
[0052]
That is, the motor control unit 40 of the third embodiment can determine the cutting assist command value (cutting current command value) based on the cutting assist map 23a and the steering torque when the steering wheel is cut. When the steering wheel is turned back, the turning assist command value can be calculated by the above equation (3) to determine the turning back assist command value. It is possible to set a good motor current and an assist torque corresponding to the steering feeling (return feeling) at the time of return. In addition, the storage space of the memory device that stores the switchback assist map 23b and the like can be reduced by the amount that the switchback assist map 23b is not required. Therefore, in addition to the effect of improving the steering sensation of both the turning and turning back of the steering wheel, there is an effect of further reducing the device cost.
[0053]
[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 that of the electric power steering apparatus 10 according to the first embodiment described above, but the motor control that controls the ECU 15, the motor drive circuit 18, and the motor M is provided. It differs from the motor control unit 20 described above in that the unit 50 includes an assist map 52, a target gain setting unit 54, and an annealing process 56 instead of the cutting assist map 23a, the switching back assist map 23b, and the switching unit 24. . Therefore, substantially the same components as those of the motor control unit 20 of the first embodiment are denoted by the same reference numerals and description thereof is omitted.
[0054]
As shown in FIG. 9, the motor control unit 50 includes an assist map 52 in the subsequent stage of the phase compensation unit 21, the target gain setting unit 54 in the subsequent stage of the cut-in / turn-back determination unit 22, and the smoothing in the subsequent stage. Processing 56 is provided. A multiplication unit 58 that multiplies the output of the assist map 52 and the smoothing process 56 is positioned in front of the addition unit 29.
[0055]
The assist map 52 is a cutting assist map having substantially the same characteristics as the above-described cutting assist map 23a, and can determine a reference assist command value (reference current command value).
[0056]
The target gain setting unit 54 sets a predetermined cutting gain or a predetermined switching back gain based on the turning direction of the steering wheel determined by the cutting / cutback determination unit 22. For example, if the determination result by the cut / return determination unit 22 is “cut”, a cut gain of 1.0 is set, and if the determination result is “cutback”, a switchback gain of 1.2 is set. Perform gain setting processing.
[0057]
The annealing process 56 performs the same process as the annealing process 32 of the motor control unit 30 according to the second embodiment described above, and sets the set speed by the target gain setting unit 54 for setting the cutting gain and the switching back gain. It is provided for the purpose of lowering below the value. Specifically, there are a transfer function G according to the above-mentioned equation (1), a weighted average or moving average algorithm, a digital filter, and the like, which have the same effect as the LPF.
[0058]
The multiplication unit 58 multiplies the reference current command value output from the assist map 52 by the cut gain or the return gain processed by the annealing process 56. As a result, the reference current command value output from the assist map 52 is output to the adder 29 as a cut-in current command value or a switch-back current command value amplified by the cut-in gain or the return gain.
[0059]
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. Is done. 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 a hysteresis characteristic that is larger than the cutting current command value (assist command value).
[0060]
That is, in the motor control unit 50 of the fourth embodiment, when the steering wheel is turned, the current command value (assist torque) determined by the assist map 52 from the steering torque is changed to the turning gain set to 1.0. When the steering wheel is turned back, the current command value (assist torque) determined by the assist map 52 from the steering torque is set to 1.2, which is larger than the cut gain. Since it can be amplified by the switchback gain and the switchback current command value can be determined, the steering feel at the time of cutting (build-up feeling) and the steering feeling at the time of switchback (feeling of return) are excellent. The motor current and thus the assist torque can be set. Therefore, there is an effect that it is possible to improve the steering feeling of both the turning and turning back of the steering wheel.
[0061]
Further, in the motor control unit 50 of the fourth embodiment, the setting speed by the target gain setting unit 54 for setting the cutting gain and the switching back gain is lowered to a predetermined value or less by the annealing process 56, so that FIG. As shown in FIG. 11, a spike-like sudden change region that can occur in the assist command value when the steering angle changes suddenly from “cut” to “cutback” and from “cutback” to “cut” (FIG. 11 ( C) Waveforms in the middle α) can be removed. Thereby, as shown in FIG. 11 (B), a continuous assist command value can be generated. Therefore, there is an effect that the steering feeling of both the turning and turning back of the steering wheel can be further improved.
[0062]
[Fifth Embodiment]
Next, a fifth 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, and is substantially the same as the motor control unit 50 according to the fourth embodiment described above. Although the configuration is adopted, the motor control unit 50 is different in that the sensor output 62 of the vehicle speed sensor 12 is input to the target gain setting unit 54. Therefore, substantially the same components as those of the motor control unit 50 of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
In the present embodiment, the assist map 52 is used as in the fourth embodiment, and the assist map 52 corresponds to “another map” that is neither a cut-in map nor a cut-back map.
[0063]
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 that is positioned between the cut-in / return 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 switchback gain regardless of the turning direction of the steering wheel determined by the switchback determination unit 22. Set to a value of gain or less.
[0064]
That is, the target gain setting unit 64 performs a gain setting process shown in FIG.
In step S201, the determination flag output from the cut-in / return determination unit 22 is acquired, and in 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.
[0065]
On the other hand, in steps S203 and 204 processed in parallel with step S201 and step S202, a vehicle speed signal which is the vehicle speed sensor output 62 is acquired from the vehicle speed sensor 12, and a vehicle speed value is detected.
[0066]
In step S205, it is determined whether or not the vehicle speed value is zero. If the vehicle speed value is zero (Yes in S205), the target gain is set to G0 (eg, 1.0) in step S206. On the other hand, if the vehicle speed value is not zero (No in S205), it is determined whether or not the determination flag value is set to “0” in the next step S207.
[0067]
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 (eg, 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.
[0068]
When the target gain setting process in steps S206, S208, and S209 is completed, the gain setting process is terminated.
[0069]
In the motor control unit 60 described above, when the vehicle value detected by the vehicle speed sensor 12 is zero, the target gain setting unit 64 sets the return gain regardless of the turning direction of the steering wheel determined by the cut / return determination unit 22. Is set to a value (1.0) that is equal to or less than the value (1.2) of the cutting gain, the switching gain that is selected when the steering wheel is switched back can be set to a value that is lower than the cutting gain. Thereby, when the vehicle value is substantially zero, the self-excited oscillation that is likely to occur at the time of switching back can be prevented because the target gain is set higher than necessary. Therefore, even when the vehicle value is substantially 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 embodiments described above, the rotation direction of the steering wheel is obtained by the steering angle sensor 13, but other means may be employed. When the steering angle sensor 13 is used, the rotational speed is obtained based on the steering angle obtained from the sensor 13, and the rotational direction is obtained from this rotational speed. It is also possible to estimate the rotational speed of the steering wheel from a well-known voltage equation using the actual motor current, and to obtain the rotational direction from this estimated value.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main electrical configuration of a motor control unit by 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-in / turn-back determination unit constituting 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 by 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 a current command value calculation process 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 by 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 annealing process of the motor control unit of the second embodiment. FIG. 7A shows a case where the annealing process is performed, and FIG. 7B shows a case where the annealing process is not performed. The characteristic diagram of each switching judgment value and assist command value is shown.
FIG. 8 is a block diagram showing a main electrical configuration of a motor control unit by 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 by 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.
FIGS. 11A and 11B are explanatory diagrams showing effects of the smoothing process of the motor control unit according to the fourth embodiment. FIG. 11A shows a steering angle change example, and FIG. FIG. 11C is a characteristic diagram of the assist command value with respect to the steering angle when there is no smoothing processing.
FIG. 12 is a block diagram showing a main electrical configuration of a motor control unit by an electric power steering apparatus according to a fifth embodiment of the present invention.
FIG. 13 is a flowchart showing a 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 circuit
20, 30, 40, 50, 60 Motor controller
21 Phase compensator
22 Infeed / return determination unit (Incision / return determination means)
23a Cutting assist map (cutting map, current command means)
23b Switchback assist map (switchback map, current command means)
24 switching part (current command means)
25 PI controller (motor control means)
27 Motor current detector (motor control means)
29 Adder (Motor control means)
32 Annealing (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, 64 Target gain setting section (current command means)
56 Annealing
58 Multiplier (Current command means)

Claims (5)

An electric power steering apparatus including a motor that supplements a steering force based on a steering torque generated in a steering shaft,
Steering torque detection means for detecting the steering torque;
A rotation direction detecting means for detecting a rotation direction of the steering wheel;
A cut-in / back-out determining unit that determines whether the steering wheel is turned in or out based on the steering torque detected by the steering torque detecting unit and the rotation direction of the steering wheel detected by the rotation direction detecting unit;
A cutting map or a returning map that is selected based on the turning direction of the steering wheel determined by the cutting / cutback determining means and that can determine an assist torque that supplements the steering force from the steering torque, and detected by the steering torque detecting means Current command means for determining a current command value to the motor based on the steering torque,
Current detecting means for detecting a motor current flowing in the motor;
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 ,
The current command means includes
Electric power steering apparatus according to claim Rukoto a delay means to slow down the time required to select the cut map and the switchback mapped to more than a predetermined time. Having a speed sensor for detecting the vehicle speed, and when the vehicle speed detected by the vehicle speed sensor is substantially zero,
The current command means includes any one of the cutting map, the switching back map, or another map that is neither the cutting map nor the switching map, and the steering torque detected by the steering torque detection means. The electric power steering apparatus according to claim 1, wherein a current command value to the motor is determined based on. An electric power steering apparatus including a motor that supplements a steering force based on a steering torque generated in a steering shaft,
Steering torque detection means for detecting the steering torque;
A rotation direction detecting means for detecting a rotation direction of the steering wheel;
A cut-in / back-out determining unit that determines whether the steering wheel is turned in or out based on the steering torque detected by the steering torque detecting unit and the rotation direction of the steering wheel detected by the rotation direction detecting unit;
A cutting current command value to the motor determined based on a cutting map that can determine an assist torque that supplements the steering force from the steering torque, and a steering torque detected by the steering torque detecting means, and the cutting current command value Current command means for selecting one of the switchback current command values to the motor determined by performing a predetermined calculation on the basis of the turning direction of the steering wheel determined by the cutback return determination means;
Current detecting means for detecting a motor current flowing in the motor;
Electric power comprising: 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. Steering device. An electric power steering apparatus including a motor that supplements a steering force based on a steering torque generated in a steering shaft,
Steering torque detection means for detecting the steering torque;
A rotation direction detecting means for detecting a rotation direction of the steering wheel;
A cut-in / back-out determining unit that determines whether the steering wheel is turned in or out based on the steering torque detected by the steering torque detecting unit and the rotation direction of the steering wheel detected by the rotation direction detecting unit;
(1) a reference map capable of determining an assist torque that supplements the steering force from the steering torque; (2) amplifying the assist torque selected based on the turning direction of the steering wheel determined by the cut-in / turn-back determining means A current command value to the motor is determined on the basis of a predetermined cutting gain or a predetermined switching return gain set larger than the predetermined cutting gain and (3) the steering torque detected by the steering torque detecting means Current command means for
Current detecting means for detecting a motor current flowing in the motor;
Electric power comprising: 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. Steering device. Having a speed sensor for detecting the vehicle speed, and when the vehicle speed detected by the vehicle speed sensor is substantially zero,
The current command means sets the predetermined switchback gain to a value equal to or less than the predetermined switch gain regardless of the turning direction of the steering wheel determined by the switchback determination section. The electric power steering apparatus according to claim 4.

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