JP2015229385A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of resolving an insufficient assistance during a turning of a vehicle at a high speed.SOLUTION: A basic assist torque command value setting part 41 sets a basic assist torque command value Taoon the basis of a detected steering torque T detected by a torque sensor 11 and a vehicle velocity V to be detected by a vehicle speed sensor 24. A compensation amount setting part 63, when a vehicle is determined as in a high-speed traveling state by a high-speed travel state determination part 61 and when the vehicle is determined as in a turning state by a turning state determination part 62, sets an assist torque compensation amount Tac on the basis of a lateral acceleration Gy detected by a lateral acceleration sensor 25. A compensation amount addition part 43 adds the assist torque compensation amount Tac to the basic assist torque command value Tao.

Description

  The present invention relates to an electric power steering apparatus.

Patent Document 1 discloses an electric power steering device that gives a sense of responsiveness when the steering wheel is increased by reducing the assist signal as the lateral acceleration increases.
Patent Document 2 discloses a hydraulic power steering apparatus that reduces the amount of assist when the lateral acceleration increases, thereby increasing the steering wheel when the vehicle enters the corner so that the driver can actually feel the approach to the corner. Is disclosed.

JP-A 63-306972 JP-A-6-107194

  In an electric power steering device, in general, an assist force (steering assist force) is increased so that steering can be performed with a small steering force during low-speed traveling, and the assist force is decreased in order to give the driver a sense of responsiveness during high-speed traveling. The For this reason, when emergency avoidance is performed during high speed traveling or when traveling at a high speed on the winding road, there is a risk that a handle becomes heavy due to insufficient assist force.

  An object of the present invention is to provide an electric power steering device that can solve the shortage of assist force during turning at high speed.

  The invention according to claim 1 is an electric power steering device (1) for applying a steering assist force from an electric motor (18) to a steering mechanism (4) of a vehicle, and a command value setting for setting a basic assist torque command value Means (41), vehicle speed acquisition means (12, 12A, 12B) for acquiring the vehicle speed of the vehicle, and turning state determination means (62, 62A, 62B) for determining whether or not the vehicle is turning. Set by the command value setting means on condition that the vehicle speed acquired by the vehicle speed acquisition means is equal to or higher than a predetermined first threshold and the turning state determination means determines that the vehicle is turning. Correction means (42, 42A, 42B, 43) for correcting the basic assist torque command value so that the absolute value of the basic assist torque command value is increased, and the correction means. Based on the basic assist torque command value after correction, and means for controlling said electric motor, an electric power steering apparatus. In addition, although the alphanumeric character in parentheses represents a corresponding component in an embodiment described later, of course, the scope of the present invention is not limited to the embodiment. The same applies hereinafter.

  In the present invention, the basic assist torque command value is corrected so that the absolute value of the basic assist torque command value is increased on condition that the vehicle speed is equal to or higher than the predetermined first threshold value and the vehicle is in a turning state. As a result, the assist force is increased when the vehicle speed is turning at or above the first threshold. As a result, the shortage of assist force during turning at high speed can be resolved. This makes it possible to suppress or prevent the steering wheel from becoming heavy due to insufficient assist force when performing emergency avoidance during high speed traveling or traveling at a high speed on the winding road.

  The invention according to claim 2 includes steering torque acquisition means (12, 12A, 12B) for acquiring a steering torque applied to the steering member (2) operated for steering the vehicle, and the command value setting The means is configured to set a basic assist torque command value based on the steering torque acquired by the steering torque acquisition means and the vehicle speed acquired by the vehicle speed acquisition means, and the correction means 2. The electric power steering apparatus according to claim 1, further comprising: as a condition for correcting the basic assist torque command value, an absolute value of the steering torque acquired by the steering torque acquisition unit is a predetermined second threshold value or more. is there.

Invention of Claim 3 contains the lateral acceleration acquisition means (12) which acquires the lateral acceleration of the said vehicle, and the said turning state determination means (62) is the absolute value of the lateral acceleration acquired by the said lateral acceleration acquisition means. 3. The electric power steering apparatus according to claim 1, wherein when the vehicle is equal to or greater than a predetermined third threshold value, the vehicle is determined to be in a turning state.
According to a fourth aspect of the present invention, the correction means determines that the vehicle speed acquired by the vehicle speed acquisition means is greater than or equal to a predetermined first threshold and that the vehicle is in a turning state by the turning state determination means. Sometimes, the compensation amount setting means (63) for setting the assist torque compensation amount based on the lateral acceleration acquired by the lateral acceleration acquisition means, and the assist torque compensation amount set by the compensation amount setting means are set to the command The electric power steering apparatus according to claim 3, further comprising an adding means (43) for adding to the basic assist torque command value set by the value setting means.

  The invention according to claim 5 includes a yaw rate acquisition means (12A) for acquiring the yaw rate of the vehicle, and the turning state determination means (62A) has a predetermined absolute value of the yaw rate acquired by the yaw rate acquisition means. 3. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is configured to determine that the vehicle is in a turning state when the threshold value is 4 or more.

  According to a sixth aspect of the present invention, the correction means determines that the vehicle speed acquired by the vehicle speed acquisition means is greater than or equal to a predetermined first threshold and that the vehicle is in a turning state by the turning state determination means. Sometimes, the compensation amount setting means (63A) for setting the assist torque compensation amount based on the yaw rate acquired by the yaw rate acquisition means, and the assist torque compensation amount set by the compensation amount setting means are set to the command value setting. The electric power steering apparatus according to claim 5, further comprising an adding means for adding to the basic assist torque command value set by the means.

  The invention according to claim 7 includes steering angle acquisition means (12B) for acquiring a steering angle which is a rotation angle of the steering member (2) operated for steering the vehicle, and the turning state determination means ( 62B) is configured to determine that the vehicle is in a turning state when the absolute value of the steering angle acquired by the steering angle acquisition means is greater than or equal to a predetermined fifth threshold value. 2. The electric power steering apparatus according to 2.

  According to an eighth aspect of the present invention, the correction means determines that the vehicle speed acquired by the vehicle speed acquisition means is equal to or higher than a predetermined first threshold and that the vehicle is in a turning state by the turning state determination means. Sometimes, the compensation amount setting means (63B) for setting the assist torque compensation amount based on the steering angle acquired by the steering angle acquisition means, and the assist torque compensation amount set by the compensation amount setting means are used as the command. The electric power steering apparatus according to claim 7, further comprising addition means for adding to the basic assist torque command value set by the value setting means.

FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing an electrical configuration of the ECU. FIG. 3 is a schematic diagram schematically showing the configuration of the electric motor. FIG. 4 is a graph showing a setting example of the basic assist torque command value Tao ^* with respect to the detected steering torque T. FIG. 5 is a graph showing a setting example of the assist torque compensation amount Tac with respect to the lateral acceleration Gy. FIG. 6 is a flowchart for explaining the operation of the assist torque compensation amount calculation unit. FIG. 7 is a flowchart for explaining another example of the operation of the assist torque compensation amount calculation unit. FIG. 8 is a block diagram showing a first modification of the ECU. FIG. 9 is a graph showing a setting example of the assist torque compensation amount Tac with respect to the yaw rate γ. FIG. 10 is a block diagram showing a second modification of the ECU. FIG. 11 is a graph showing a setting example of the assist torque compensation amount Tac with respect to the steering angle θh.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus according to an embodiment of the present invention.
The electric power steering apparatus 1 includes a steering wheel 2 as a steering member for steering the vehicle, a steering mechanism 4 that steers the steered wheels 3 in conjunction with the rotation of the steering wheel 2, and steering by the driver. And a steering assist mechanism 5 for assisting. The steering wheel 2 and the steering mechanism 4 are mechanically coupled via a steering shaft 6 and an intermediate shaft 7.

The steering shaft 6 includes an input shaft 8 connected to the steering wheel 2 and an output shaft 9 connected to the intermediate shaft 7. The input shaft 8 and the output shaft 9 are connected via a torsion bar 10 so as to be relatively rotatable.
A torque sensor 11 is disposed around the steering shaft 6. The torque sensor 11 detects the steering torque T applied to the steering wheel 2 based on the relative rotational displacement amount of the input shaft 8 and the output shaft 9. In this embodiment, the steering torque T detected by the torque sensor 11 is detected, for example, as a torque for steering in the right direction as a positive value and a torque for steering in the left direction as a negative value. It is assumed that the magnitude of the steering torque increases as the absolute value thereof is detected. The upper limit value of the magnitude of the steering torque T that can be detected by the torque sensor 11 is determined in advance by the performance (strength, durability) of the torsion bar 10.

  The steered mechanism 4 includes a rack and pinion mechanism including a pinion shaft 13 and a rack shaft 14 as a steered shaft. The steered wheel 3 is connected to each end of the rack shaft 14 via a tie rod 15 and a knuckle arm (not shown). The pinion shaft 13 is connected to the intermediate shaft 7. The pinion shaft 13 rotates in conjunction with the steering of the steering wheel 2. A pinion 16 is connected to the tip of the pinion shaft 13 (the lower end in FIG. 1).

  The rack shaft 14 extends linearly along the left-right direction of the automobile. A rack 17 that meshes with the pinion 16 is formed at an intermediate portion in the axial direction of the rack shaft 14. By the pinion 16 and the rack 17, the rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14. The steered wheels 3 can be steered by moving the rack shaft 14 in the axial direction.

When the steering wheel 2 is steered (rotated), this rotation is transmitted to the pinion shaft 13 via the steering shaft 6 and the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into an axial movement of the rack shaft 14 by the pinion 16 and the rack 17. Thereby, the steered wheel 3 is steered.
The steering assist mechanism 5 includes an electric motor 18 for assisting steering and a speed reduction mechanism 19 for transmitting the output torque of the electric motor 18 to the steering mechanism 4. In this embodiment, the electric motor 18 is a three-phase brushless motor. In the vicinity of the electric motor 18, a rotation angle sensor 23 made of, for example, a resolver for detecting the rotation angle of the rotor of the electric motor 18 is disposed. The speed reduction mechanism 19 includes a worm gear mechanism that includes a worm shaft 20 and a worm wheel 21 that meshes with the worm shaft 20. The speed reduction mechanism 19 is accommodated in a gear housing 22 as a transmission mechanism housing.

The worm shaft 20 is rotationally driven by the electric motor 18. The worm wheel 21 is coupled to the steering shaft 6 so as to be rotatable in the same direction. The worm wheel 21 is rotationally driven by the worm shaft 20.
When the worm shaft 20 is rotationally driven by the electric motor 18, the worm wheel 21 is rotationally driven and the steering shaft 6 rotates. The rotation of the steering shaft 6 is transmitted to the pinion shaft 13 via the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14. Thereby, the steered wheel 3 is steered. That is, the wheel 3 is steered by rotating the worm shaft 20 by the electric motor 18.

  The vehicle is provided with a vehicle speed sensor 24 for detecting the vehicle speed V and a lateral acceleration sensor 25 for detecting the lateral acceleration Gy of the vehicle. In this embodiment, the lateral acceleration Gy detected by the lateral acceleration sensor 25 is, for example, detected as a positive value when the vehicle is turning right, and the lateral acceleration when the vehicle is turning left is It is detected as a negative value, and the magnitude of the lateral acceleration increases as the absolute value increases.

The electric motor 18 is controlled by an ECU (Electronic Control Unit) 12 as a motor control device. The ECU 12 receives a steering torque T detected by the torque sensor 11, a vehicle speed V detected by the vehicle speed sensor 24, a lateral acceleration Gy detected by the lateral acceleration sensor 25, an output signal of the rotation angle sensor 23, and the like. .
FIG. 2 is a block diagram showing an electrical configuration of the ECU 12.

The ECU 12 includes a microcomputer 31, a drive circuit (inverter circuit) 32 that is controlled by the microcomputer 31 and supplies electric power to the electric motor 18, and a current detection unit 33 that detects a motor current flowing through the electric motor 18. Yes.
The electric motor 18 is, for example, a three-phase brushless motor, and includes a rotor 100 as a field and U-phase, V-phase, and W-phase stator windings 101, 102, and 103, as schematically shown in FIG. And a stator 105. The electric motor 18 may be of an inner rotor type having a stator opposed to the outside of the rotor, or may be of an outer rotor type having a stator opposed to the inside of a cylindrical rotor.

  Three-phase fixed coordinates (UVW coordinate system) are defined in which the U, V, and W axes are taken in the direction of the stator windings 101, 102, and 103 of each phase. Further, a two-phase rotational coordinate system (dq coordinate system) in which the d axis (magnetic pole axis) is taken in the magnetic pole direction of the rotor 100 and the q axis (torque axis) is taken in a direction perpendicular to the d axis in the rotation plane of the rotor 100. The actual rotating coordinate system) is defined. The dq coordinate system is a rotating coordinate system that rotates with the rotor 100. In the dq coordinate system, since only the q-axis current contributes to the torque generation of the rotor 100, the d-axis current may be set to zero and the q-axis current may be controlled according to the desired torque. The rotation angle (electrical angle) θe of the rotor 100 is the rotation angle of the d axis with respect to the U axis. The dq coordinate system is an actual rotation coordinate system according to the rotor rotation angle θe. By using the rotor rotation angle θe, coordinate conversion between the UVW coordinate system and the dq coordinate system can be performed.

  Returning to FIG. 2, the microcomputer 31 includes a CPU and a memory (ROM, RAM, nonvolatile memory, etc.), and functions as a plurality of function processing units by executing a predetermined program. . The plurality of function processing units include a basic assist torque command value setting unit 41, an assist torque compensation amount calculation unit 42, a compensation amount addition unit 43, a current command value setting unit 44, a current deviation calculation unit 45, A PI (proportional integration) control unit 46, a dq / UVW conversion unit 47, a PWM (Pulse Width Modulation) control unit 48, a UVW / dq conversion unit 49, and a rotation angle calculation unit 50 are included.

The rotation angle calculation unit 50 calculates the rotation angle θe of the rotor of the electric motor 18 based on the output signal of the rotation angle sensor 23. The rotor rotation angle θe (electrical angle) calculated by the rotation angle calculation unit 51 is given to the dq / UVW conversion unit 47 and the UVW / dq conversion unit 49.
The basic assist torque command value setting unit 41 sets a basic assist torque command value Tao ^* based on the detected steering torque T detected by the torque sensor 11 and the vehicle speed V detected by the vehicle speed sensor 24. An example of setting the basic assist torque command value Tao ^* for the detected steering torque T is shown in FIG. For the detected steering torque T, for example, the torque for steering in the right direction is a positive value, and the torque for steering in the left direction is a negative value. The basic assist torque command value Tao ^* is a positive value when a steering assist force for rightward steering is to be generated from the electric motor 18, and a steering assist force for leftward steering is generated from the electric motor 18. When it should be made negative, it is a negative value. The basic assist torque command value Tao ^* is positive for a positive value of the detected steering torque T, and is negative for a negative value of the detected steering torque T.

When the detected steering torque T is a small value (torque dead zone) in the range of -T1 to T1 (for example, T1 = 0.4 N · m), the basic assist torque command value Tao ^* is set to zero. When the detected steering torque T is a value outside the range of -T1 to T1, the basic assist torque command value Tao ^* increases as the absolute value of the detected steering torque T increases. Is set. However, as described above, the torque sensor 11 cannot detect a steering torque equal to or higher than a predetermined upper limit value T2 (T2> 0), so even if the absolute value of the actual steering torque exceeds the upper limit value T2, the basic the absolute value of the assist torque command value Tao ^* becomes a value corresponding to the upper limit T2. The upper limit value T2 is, for example, about 6.5 Nm. Further, the basic assist torque command value Tao ^* is set such that the absolute value thereof decreases as the vehicle speed V detected by the vehicle speed sensor 24 increases. As a result, the steering assist force is increased during low speed travel, and the steering assist force is decreased during high speed travel.

Returning to FIG. 2, the assist torque compensation amount calculation unit 42 is provided in order to eliminate the shortage of the steering assist force (assist force) when turning at high speed. The assist torque compensation amount calculation unit 42 calculates an assist torque compensation amount Tac based on the vehicle speed V detected by the vehicle speed sensor 24 and the lateral acceleration Gy detected by the lateral acceleration sensor 25.
Specifically, the assist torque compensation amount calculation unit 42 includes a high speed traveling state determination unit 61, a turning state determination unit 62, and a compensation amount setting unit 63. The high speed traveling state determination unit 61 determines whether the vehicle is in a high speed traveling state based on the vehicle speed V detected by the vehicle speed sensor 24. Specifically, the high speed traveling state determination unit 61 determines that the vehicle is in a high speed traveling state when the vehicle speed V is equal to or higher than a predetermined first threshold A (A> 0). The first threshold A is set to 80 km / h, for example.

  The turning state determination unit 62 determines whether the vehicle is in a turning state based on the lateral acceleration Gy detected by the lateral acceleration sensor 25. Specifically, the turning state determination unit 62 determines that the vehicle is in a turning state when the absolute value of the lateral acceleration Gy is equal to or greater than a predetermined third threshold C (C> 0). The compensation amount setting unit 63 uses the lateral acceleration sensor 25 when the vehicle is determined to be in a high-speed traveling state by the high-speed traveling state determination unit 61 and the vehicle is in a turning state by the turning state determination unit 62. Based on the detected lateral acceleration Gy, an assist torque compensation amount Tac is set.

  A setting example of the assist torque compensation amount Tac for the lateral acceleration Gy is shown in FIG. When the absolute value of the lateral acceleration Gy is less than the third threshold C, the turning state determination unit 62 determines that the vehicle is not in a turning state, and the assist torque compensation amount Tac is set to zero. On the other hand, when the absolute value of the lateral acceleration Gy is equal to or greater than the third threshold C, the turning state determination unit 62 determines that the vehicle is in a turning state, and the compensation amount setting unit 63 determines that the assist torque compensation amount Tac is a significant value. Set to Specifically, when the lateral acceleration Gy is greater than or equal to the third threshold C (when turning right), the assist torque compensation amount Tac is a positive value, and when the lateral acceleration Gy is less than -C (when turning left) ) Has a negative value for the lateral acceleration Gy. The assist torque compensation amount Tac is set such that the absolute value of the assist torque compensation amount Tac increases as the absolute value of the lateral acceleration Gy increases.

FIG. 6 is a flowchart for explaining the operation of the assist torque compensation amount calculation unit 42. The process of FIG. 6 is repeatedly executed at every predetermined calculation cycle.
The high speed traveling state determination unit 61 determines whether or not the vehicle is in a high speed traveling state by determining whether or not the vehicle speed V detected by the vehicle speed sensor 24 is equal to or higher than a predetermined first threshold A ( Step S1). When the vehicle speed V is less than the first threshold A (step S1: NO), the high speed traveling state determination unit 61 determines that the vehicle is not in the high speed traveling state, and returns to step S1.

  When it is determined that the vehicle speed V is equal to or higher than the first threshold A (step S1: YES), the high speed traveling state determination unit 61 determines that the vehicle is in a high speed traveling state, and proceeds to step S2. In step S2, the turning state determination unit 62 and the compensation amount setting unit 63 determine whether or not the vehicle is in a turning state based on the lateral acceleration Gy detected by the lateral acceleration sensor 25, and the vehicle is in a turning state. Is determined, the assist torque compensation amount Tac is set. Specifically, as described above, the turning state determination unit 62 and the compensation amount setting unit 63 compensate the assist torque for the lateral acceleration Gy detected by the lateral acceleration sensor 25 and the lateral acceleration Gy shown in FIG. Based on the relationship of the amount Tac, the assist torque compensation amount Tac is set.

Returning to FIG. 2, the compensation amount adding unit 43 adds the assist torque compensation amount Tac calculated by the assist torque compensation amount calculating unit 42 to the basic assist torque command value Tao ^* set by the basic assist torque command value setting unit 41. By adding, the assist torque command value Ta ^* is calculated. Thereby, the absolute value of the assist torque command value Ta ^* is larger than the absolute value of the basic assist torque command value Tao ^{* by} the absolute value of the assist torque compensation amount Tac. The assist torque compensation amount calculation unit 42 and the compensation amount addition unit 43 constitute correction means for correcting the basic assist torque command value Tao ^* .

The current command value setting unit 44 sets a current value to be passed through the coordinate axes of the dq coordinate system as a current command value. Specifically, the current command value setting unit 44 refers to a d-axis current command value I _d ^* and a q-axis current command value I _q ^* (hereinafter, collectively referred to as “two-phase current command value I _dq ^* ”). ) Is set. More specifically, the current command value setting unit 44 sets the q-axis current command value I _q ^* to a significant value and sets the d-axis current command value I _d ^* to zero. More specifically, the current command value setting unit 44, the compensation amount adding section 43 by the calculated assist torque command value Ta ^*, divided by the torque constant K _T of the electric motor 18, q-axis current command value Set I _q ^* . The two-phase current command value I _dq ^* set by the current command value setting unit 44 is given to the current deviation calculation unit 45.

The current detection unit 33 detects the U-phase current I _U , the V-phase current I _V and the W-phase current I _W (hereinafter, collectively referred to as “three-phase detection current I _UVW ”) of the electric motor 18. To do. The three-phase detection current I _UVW detected by the current detection unit 33 is given to the UVW / dq conversion unit 49.
The UVW / dq conversion unit 49 converts the three-phase detection current I _UVW (U-phase current I _U , V-phase current I _V and W-phase current I _W ) in the UVW coordinate system detected by the current detection unit 33 into the dq coordinate system. _Are transformed into two-phase detection currents I _d and I _q (hereinafter collectively referred to as “two-phase detection current I _dq ”). For this coordinate conversion, the rotor rotation angle θe calculated by the rotation angle calculation unit 50 is used.

The current deviation calculation unit 45 calculates a deviation between the two-phase current command value I _dq ^* set by the current command value setting unit 44 and the two-phase detection current I _dq given from the UVW / dq conversion unit 49. More specifically, the current deviation calculation unit 45 calculates the deviation of the d-axis detection current I _d with respect to the d-axis current command value I _d ^* and the deviation of the q-axis detection current I _q with respect to the q-axis current command value I _q ^* . To do. These deviations are given to the PI control unit 46.

The PI control unit 46 performs a PI calculation on the current deviation calculated by the current deviation calculation unit 45, whereby a two-phase voltage command value V _dq ^* (d-axis voltage command value V _d ^* and q-axis voltage command value V _q ^* ) is generated. The two-phase voltage command value V _dq ^* is given to the dq / UVW converter 47.
The dq / UVW conversion unit 47 performs coordinate conversion of the two-phase voltage command value V _dq ^* into the three-phase voltage command value V _UVW ^* . For this coordinate conversion, the rotor rotation angle θe calculated by the rotation angle calculation unit 50 is used. The three-phase voltage command value V _UVW ^* includes a U-phase voltage command value V _U ^* , a V-phase voltage command value V _V ^*, and a W-phase voltage command value V _W ^* . The three-phase voltage command value V _UVW ^* is given to the PWM control unit 48.

The PWM control unit 48 includes a U-phase PWM command signal, a V-phase PWM control signal having a duty corresponding to the U-phase voltage command value V _U ^* , the V-phase voltage command value V _V ^*, and the W-phase voltage command value V _W ^* , respectively. A W-phase PWM control signal is generated and supplied to the drive circuit 32.
The drive circuit 32 includes a three-phase inverter circuit corresponding to the U phase, the V phase, and the W phase. The power elements constituting the inverter circuit are controlled by a PWM control signal supplied from the PWM control unit 48, whereby a voltage corresponding to the three-phase voltage command value V _UVW ^* is set to the stator winding 101 of each phase of the electric motor 18. , 102, 103.

The current deviation calculation unit 45 and the PI control unit 46 constitute a current feedback control unit. By the action of this current feedback control means, the motor current flowing through the electric motor 18 is controlled so as to approach the two-phase current command value I _dq ^* set by the current command value setting unit 44. In other words, the motor torque (assist force) generated from the electric motor 18 is controlled so as to approach the assist torque command value Ta ^* calculated by the compensation amount adding unit 43.

In the above-described embodiment, the assist torque compensation amount Tac is calculated by the assist torque compensation amount calculation unit 42 when turning at high speed. Then, the assist torque command value Ta ^* is calculated by adding the assist torque compensation amount Tac to the basic assist torque command value Tao ^* . Thereby, the absolute value of the assist torque command value Ta ^* is larger than the absolute value of the basic assist torque command value Tao ^{* by} the absolute value of the assist torque compensation amount Tac. Therefore, the magnitude of the assist force increases during turning at high speed. Thereby, the shortage of assist at the time of turning at high speed can be solved. This makes it possible to suppress or prevent the steering wheel from becoming heavy due to insufficient assist force when performing emergency avoidance during high speed traveling or traveling at a high speed on the winding road.

  In the above-described embodiment, the assist torque compensation amount calculation unit 42 calculates the assist torque compensation amount Tac when turning at high speed. However, the absolute value of the steering torque T is a predetermined second threshold value B ( The assist torque compensation amount Tac may be calculated during turning when B> 0) or more. That is, the assist torque compensation amount calculation unit 42 determines whether or not the absolute value of the steering torque T detected by the torque sensor 11 is equal to or greater than a predetermined second threshold B as indicated by a broken line 64 in FIG. A steering torque determination unit 64 may be included. In this case, the compensation amount setting unit 63 determines that the vehicle is in the high-speed driving state by the high-speed driving state determination unit 61 and the absolute value of the steering torque T is greater than or equal to a predetermined second threshold value B by the steering torque determination unit 64. The assist torque compensation amount Tac is set based on the lateral acceleration Gy detected by the lateral acceleration sensor 25 when it is determined that the vehicle is in a turning state by the turning state determination unit 62.

The operation of the assist torque compensation amount calculation unit 42 in this case is shown in FIG. The process of FIG. 7 is repeatedly executed at every predetermined calculation cycle.
The high speed traveling state determination unit 61 determines whether or not the vehicle is in a high speed traveling state by determining whether or not the vehicle speed V detected by the vehicle speed sensor 24 is equal to or higher than a predetermined first threshold A ( Step S11). When the vehicle speed V is less than the first threshold A (step S11: NO), the high speed traveling state determination unit 61 determines that the vehicle is not in the high speed traveling state, and returns to step S11.

  When it is determined that the vehicle speed V is equal to or higher than the first threshold A (step S11: YES), the high speed traveling state determination unit 61 determines that the vehicle is in a high speed traveling state, and proceeds to step S12. In step S12, the steering torque determination unit 64 determines whether or not the absolute value of the steering torque T detected by the torque sensor 11 is equal to or greater than a predetermined second threshold value B. When the absolute value of the steering torque T is less than the predetermined second threshold B, the process returns to step S11.

  When it is determined in step S12 that the absolute value of the steering torque T is greater than or equal to the predetermined second threshold value B, the steering torque determination unit 64 proceeds to step S13. In step S13, the turning state determination unit 62 and the compensation amount setting unit 63 determine whether the vehicle is in a turning state based on the lateral acceleration Gy detected by the lateral acceleration sensor 25, and the vehicle is in a turning state. Is determined, the assist torque compensation amount Tac is set. Specifically, as described above, the turning state determination unit 62 and the compensation amount setting unit 63 compensate the assist torque for the lateral acceleration Gy detected by the lateral acceleration sensor 25 and the lateral acceleration Gy shown in FIG. Based on the relationship of the amount Tac, the assist torque compensation amount Tac is set.

For example, the second threshold value B may be set to the upper limit value T2 of the steering torque T that can be detected by the torque sensor 11. When the second threshold value B is set to the upper limit value T2, since the actual steering torque is equal to or higher than the upper limit value T2, the basic assist torque command value Tao ^* corresponding to the actual steering torque cannot be obtained. The absolute value of the assist torque command value Ta ^* can be made larger than the absolute value of the basic assist torque command value Tao ^* . On the other hand, when the actual steering torque is less than the upper limit value T2 and the basic assist torque command value Tao ^* corresponding to the actual steering torque is obtained, the basic assist torque command value Tao ^* is output as the assist torque command value Ta ^* . be able to. The second threshold B can be set to an arbitrary value regardless of the upper limit value T2 of the steering torque T that can be detected by the torque sensor 11.

FIG. 8 is a block diagram showing a first modification of the ECU. 8, portions corresponding to the respective portions in FIG. 2 described above are denoted by the same reference numerals as those in FIG.
In the ECU 12A, the configuration of the assist torque compensation amount calculation unit 42A in the microcomputer 31A is different from that of the ECU 12 in FIG.
As indicated by a broken line 26 in FIG. 1 and a solid line 26 in FIG. 8, the vehicle is provided with a yaw rate sensor 26 for detecting the yaw rate (rotational angular velocity of the vehicle) γ of the vehicle. In this embodiment, the yaw rate γ detected by the yaw rate sensor 26 is detected, for example, as a positive value when the vehicle is turning right, and as a negative value when the vehicle is turning left. It is assumed that the magnitude of the yaw rate increases as the absolute value thereof is detected. The yaw rate γ detected by the yaw rate sensor 26 is given to the assist torque compensation amount calculation unit 42A in the ECU 12A.

  The assist torque compensation amount calculation unit 42A calculates the assist torque compensation amount Tac based on the vehicle speed V detected by the vehicle speed sensor 24 and the yaw rate γ detected by the yaw rate sensor 26. Specifically, the assist torque compensation amount calculation unit 42A includes a high speed traveling state determination unit 61A, a turning state determination unit 62A, and a compensation amount setting unit 63A. Similarly to the high-speed traveling state determination unit 61 in FIG. 2, the high-speed traveling state determination unit 61A determines whether or not the vehicle is in a high-speed traveling state based on the vehicle speed V detected by the vehicle speed sensor 24. Specifically, the high speed traveling state determination unit 61 determines that the vehicle is in a high speed traveling state when the vehicle speed V is equal to or higher than the first threshold A (A> 0).

  The turning state determination unit 62A determines whether or not the vehicle is in a turning state based on the yaw rate γ detected by the yaw rate sensor 26. Specifically, the turning state determination unit 62A determines that the vehicle is in a turning state when the absolute value of the yaw rate γ is equal to or greater than a predetermined fourth threshold value D (D> 0). The compensation amount setting unit 63A is detected by the yaw rate sensor 26 when the vehicle is determined to be in a high-speed traveling state by the high-speed traveling state determination unit 61A and the vehicle is determined to be in a turning state by the turning state determination unit 62A. Based on the yaw rate γ, the assist torque compensation amount Tac is set.

  A setting example of the assist torque compensation amount Tac for the yaw rate γ is shown in FIG. When the absolute value of the yaw rate γ is less than the fourth threshold D, the turning state determination unit 62A determines that the vehicle is not in a turning state, and the assist torque compensation amount Tac is set to zero. On the other hand, when the absolute value of the yaw rate γ is greater than or equal to the fourth threshold value D, the turning state determination unit 62A determines that the vehicle is turning, and the compensation amount setting unit 63A sets the assist torque compensation amount Tac to a significant value. Is set. Specifically, when the yaw rate γ is equal to or greater than the fourth threshold D (when turning right), the assist torque compensation amount Tac is a positive value, and when the yaw rate γ is equal to or less than −D (when turning left). The yaw rate γ is a negative value. The assist torque compensation amount Tac is set such that the absolute value of the assist torque compensation amount Tac increases as the absolute value of the yaw rate γ increases.

The assist torque compensation amount calculation unit 42A is different from the above-described embodiment in the turning state determination method and the assist compensation amount setting method, but performs processing according to the same procedure as in FIG. 6 or FIG. 7 in the above-described embodiment. By executing, the same effect can be produced.
FIG. 10 is a block diagram showing a second modification of the ECU. 10, portions corresponding to the respective portions in FIG. 2 are denoted by the same reference numerals as in FIG.

In the ECU 12B, the configurations of the rotation angle calculation unit 50B and the assist torque compensation amount calculation unit 42B in the microcomputer 31B are different from the rotation angle calculation unit 50 and the ECU 12 of FIG. In the ECU 12B, a steering angle calculation unit 51 is added as a function processing unit realized by the microcomputer 31B.
The rotation angle calculation unit 50B calculates the rotation angles θe and θm of the rotor of the electric motor 18 based on the output signal of the rotation angle sensor 23. θe is an electrical angle, and θm is a mechanical angle. The rotation angle θm (mechanical angle) calculated by the rotation angle calculation unit 50B is given to the steering angle calculation unit 51. The steering angle calculation unit 51 calculates a steering angle θh that is the rotation angle of the steering wheel 2 based on the rotor rotation angle θm calculated by the rotation angle calculation unit 50B. The steering angle calculator 51 calculates the amount of rotation (rotation angle) of the steering wheel 2 from the neutral position of the steering wheel 2 based on the rotor rotation angle θm. In this embodiment, for example, The rotation amount in the right direction from the neutral position of the steering wheel 2 is calculated as a positive value, and the rotation amount in the left direction from the neutral position is calculated as a negative value. The steering angle θh calculated by the steering angle calculation unit 51 is given to the assist torque compensation amount calculation unit 42B.

  The assist torque compensation amount calculation unit 42B calculates the assist torque compensation amount Tac based on the vehicle speed V detected by the vehicle speed sensor 24 and the steering angle θh calculated by the steering angle calculation unit 51. The assist torque compensation amount calculation unit 42B includes a high speed traveling state determination unit 61B, a turning state determination unit 62B, and a compensation amount setting unit 63B. The high speed traveling state determination unit 61B determines whether the vehicle is in a high speed traveling state based on the vehicle speed V detected by the vehicle speed sensor 24, similarly to the high speed traveling state determination unit 61 of FIG. Specifically, when the vehicle speed V is equal to or higher than the first threshold A (A> 0), the high-speed traveling state determination unit 61 determines that the traveling state of the vehicle is a high-speed traveling state.

  The turning state determination unit 62B determines whether the vehicle is in a turning state based on the steering angle θh calculated by the steering angle calculation unit 51. Specifically, the turning state determination unit 62B determines that the vehicle is in a turning state when the absolute value of the steering angle θh is equal to or greater than a predetermined fifth threshold E (E> 0). The compensation amount setting unit 63B determines when the vehicle is in a high speed traveling state by the high speed traveling state determination unit 61B and determines that the vehicle is in a turning state by the turning state determination unit 62B. The assist torque compensation amount Tac is set based on the steering angle θh calculated by.

  An example of setting the assist torque compensation amount Tac with respect to the steering angle θh is shown in FIG. When the absolute value of the steering angle θh is less than the fifth threshold E, the turning state determination unit 62B determines that the vehicle is not in a turning state, and the assist torque compensation amount Tac is set to zero. On the other hand, when the absolute value of the steering angle θh is equal to or greater than the fifth threshold E, the turning state determination unit 62B determines that the vehicle is in a turning state, and the compensation amount setting unit 63B determines that the assist torque compensation amount Tac is a significant value. Set to Specifically, when the steering angle θh is greater than or equal to the fifth threshold E (when turning right), the assist torque compensation amount Tac is a positive value, and when the steering angle θh is less than or equal to −E (when turning left) ), The assist torque compensation amount Tac is a negative value. The assist torque compensation amount Tac is set such that the absolute value of the assist torque compensation amount Tac increases as the absolute value of the steering angle θh increases.

The assist torque compensation amount calculation unit 42B differs from the above-described embodiment in the method of determining the turning state and the method of setting the assist compensation amount, but performs processing according to the same procedure as in FIG. 6 or 7 in the above-described embodiment. By executing, the same effect can be produced.
In the second modification described above, the steering angle θh is calculated based on the output signal of the rotation angle sensor 23 that detects the rotation angle of the rotor of the electric motor 18, but the rotation angle of the steering wheel 2 is detected. The steering angle θh may be detected based on the output signal of the steering angle sensor. In this case, as indicated by a broken line 81 in FIGS. 1 and 10, for example, a steering angle sensor 81 for detecting a steering angle that is a rotation angle of the steering shaft 6 is disposed around the steering shaft 6. As shown in FIG. 10, the steering angle θh detected by the rudder angle sensor 81 may be given to the turning state determination unit 62B and the compensation amount setting unit 63B.

  The present invention can be modified in various ways within the scope of the matters described in the claims.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 2 ... Steering wheel, 4 ... Steering mechanism, 11 ... Torque sensor, 12, 12A, 12B ... ECU, 18 ... Electric motor, 24 ... Vehicle speed sensor, 25 ... Lateral acceleration sensor, 26 ... Yaw rate Sensors 41... Basic assistance torque command value setting unit 42, 42 A, 42 B... Assists torque compensation amount calculation unit 61, 61 A, 61 B... High speed running state determination unit 62, 62 A, 62 B. 63B: Compensation amount setting unit, 64, 64A, 64B ... Steering torque discriminating unit, 81 ... Steering angle sensor

Claims (8)

An electric power steering device that applies a steering assist force from an electric motor to a steering mechanism of a vehicle,
Command value setting means for setting a basic assist torque command value;
Vehicle speed acquisition means for acquiring the vehicle speed of the vehicle;
Turning state determination means for determining whether or not the vehicle is in a turning state;
It is set by the command value setting means on the condition that the vehicle speed acquired by the vehicle speed acquisition means is not less than a predetermined first threshold value and that the vehicle is determined to be turning by the turning state determination means. Correction means for correcting the basic assist torque command value so that the absolute value of the basic assist torque command value increases,
Means for controlling the electric motor based on a basic assist torque command value corrected by the correcting means. Steering torque acquisition means for acquiring a steering torque applied to a steering member operated for steering the vehicle,
The command value setting means is configured to set a basic assist torque command value based on the steering torque acquired by the steering torque acquisition means and the vehicle speed acquired by the vehicle speed acquisition means,
2. The correction means according to claim 1, further comprising: as a condition for correcting the basic assist torque command value, an absolute value of the steering torque acquired by the steering torque acquisition means is a predetermined second threshold value or more. Electric power steering device. Lateral acceleration acquisition means for acquiring lateral acceleration of the vehicle,
The turning state determination unit is configured to determine that the vehicle is in a turning state when the absolute value of the lateral acceleration acquired by the lateral acceleration acquisition unit is equal to or greater than a predetermined third threshold value. Item 3. The electric power steering device according to Item 1 or 2. The correction means includes
The lateral acceleration acquired by the lateral acceleration acquisition means when the vehicle speed acquired by the vehicle speed acquisition means is greater than or equal to a predetermined first threshold and the turning state determination means determines that the vehicle is turning. Compensation amount setting means for setting an assist torque compensation amount based on acceleration;
The electric power steering apparatus according to claim 3, further comprising an adding unit that adds the assist torque compensation amount set by the compensation amount setting unit to a basic assist torque command value set by the command value setting unit. Including a yaw rate acquisition means for acquiring the yaw rate of the vehicle,
The turning state determination unit is configured to determine that the vehicle is in a turning state when the absolute value of the yaw rate acquired by the yaw rate acquisition unit is equal to or greater than a predetermined fourth threshold value. Or an electric power steering apparatus according to 2; The correction means includes
The yaw rate acquired by the yaw rate acquisition means when the vehicle speed acquired by the vehicle speed acquisition means is greater than or equal to a predetermined first threshold and the turning state determination means determines that the vehicle is turning. Compensation amount setting means for setting the assist torque compensation amount based on,
6. The electric power steering apparatus according to claim 5, further comprising an adding unit that adds the assist torque compensation amount set by the compensation amount setting unit to the basic assist torque command value set by the command value setting unit. Steering angle acquisition means for acquiring a steering angle which is a rotation angle of a steering member operated for steering the vehicle,
The turning state determination unit is configured to determine that the vehicle is in a turning state when an absolute value of a steering angle acquired by the steering angle acquisition unit is a predetermined fifth threshold value or more. Item 3. The electric power steering device according to Item 1 or 2. The correction means includes
Steering acquired by the steering angle acquiring means when the vehicle speed acquired by the vehicle speed acquiring means is greater than or equal to a predetermined first threshold and the turning state determining means determines that the vehicle is turning. Compensation amount setting means for setting the assist torque compensation amount based on the angle;
The electric power steering apparatus according to claim 7, further comprising: adding means for adding the assist torque compensation amount set by the compensation amount setting means to the basic assist torque command value set by the command value setting means.

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