JP4457911B2 - Power steering control device - Google Patents

Description

  The present invention relates to a power steering control device that improves the operability of a vehicle.

  Conventionally, a straight drive comprising a non-straight-running detection means for detecting a single flow, a straight-run intention detection means composed of a steering angle sensor, a vehicle lateral acceleration sensor, a yaw rate sensor, and the like, and a steering means for returning the vehicle body posture to the straight-running side A sex control device is known (see, for example, Patent Document 1).

Further, when the change amount per unit time of the vehicle speed, the steering angle, and the left and right wheel speed difference is equal to or less than a predetermined value, the correction torque is calculated based on the vehicle speed, the steering angle, and the left and right wheel speed difference, and the steering torque is corrected. Thus, there is known an electric power steering device in which straightness is good even when the balance between the left and right wheels is lost (see, for example, Patent Document 2).
Japanese Unexamined Patent Publication No. 63-74768 Japanese Patent Laid-Open No. 2003-2222

  In the above conventional straightness control device, the determination method based on the state quantity from each sensor is unknown, and when traveling along a curve with a large turning radius, it is determined that the vehicle is in a straight drive state by the straight drive decision making means, and non-straight drive detection is performed. There is a possibility that the single flow state is determined by the means, which may cause a malfunction.

  On the other hand, in the above-described conventional electric power steering apparatus, the straight traveling performance of the vehicle is improved by correcting the steering torque. Therefore, in a state where steering torque is not generated, such as a state where a hand is lightly attached to the steering wheel, there is a possibility that the deflection of the vehicle may not be appropriately suppressed.

  The present invention has been made to solve the above-described problems, and has as its main purpose to suppress vehicle deflection and improve operability.

  In order to achieve the above object, one aspect of the present invention includes a right wheel speed detecting means for detecting a right wheel speed of a vehicle, a left wheel speed detecting means for detecting a left wheel speed of the vehicle, and the right wheel speed detecting. Speed difference calculating means for calculating a speed difference between the right wheel speed detected by the means and the left wheel speed detected by the left wheel speed detecting means; and the speed difference calculated by the speed difference calculating means. And a control means for suppressing the deflection of the vehicle, wherein the control means suppresses the deflection according to the speed difference calculated by the speed difference calculating means. A control apparatus for power steering, wherein the method is changed.

  According to this aspect, the control means changes the deflection suppression method according to the speed difference calculated by the speed difference calculation means. Thereby, the deflection of the vehicle is optimally suppressed according to the vehicle operation state and the like, and the operability of the vehicle is improved.

In this aspect, for example, the control means is
(A) When the speed difference calculated by the speed difference calculating means is smaller than a predetermined value, by adjusting the assist torque at the time of steering, the deflection of the vehicle is suppressed,
(B) When the speed difference calculated by the speed difference calculating means is greater than or equal to a predetermined value, the deflection of the vehicle is suppressed by moving and adjusting the rack to a neutral position.

  For example, it is preferable to adjust the assist torque at the time of steering so as to reduce the steering torque when the steering is maintained by the driver of the vehicle, the vehicle is in a straight traveling state, and the speed difference is smaller than a predetermined value. This reduces the steering force input by the driver via the steering wheel, improves operability, and suppresses vehicle deflection. On the other hand, it is preferable to move and adjust the rack to the neutral position when the speed difference is not less than a predetermined value in a state where steering torque is not generated, such as a state where the driver's hand is lightly attached to the steering wheel. Thereby, the deflection | deviation of a vehicle is suppressed automatically and the operativity of a vehicle improves. The rack may be moved and adjusted to the neutral position by the VGRS function. Here, the rack refers to a rack that constitutes a so-called rack and pinion type steering apparatus. The assist torque at the time of steering is, for example, torque that assists the steering force input from the steering wheel.

  In this aspect, the vehicle driver further includes operation state determination means for determining whether the steering is maintained and the vehicle is going to be kept straight, and the vehicle state is kept straight by the operation state determination means. When it is determined that it is about to be performed, the control means preferably suppresses the deflection of the vehicle.

  Further, in this aspect, steering torque detection means for detecting the steering torque of the vehicle is further provided, and when the steering torque detected by the steering torque detection means is equal to or greater than a predetermined torque, the operation state determination means moves straight on the vehicle. It is preferable to determine that the state is about to be maintained.

  In this aspect, steering torque detection means for detecting the steering torque of the vehicle is further provided, and when the steering torque detected by the steering torque detection means is greater than or equal to a predetermined torque, the operation state determination means indicates that the vehicle straight running state is It is preferable to determine that it is being maintained.

  According to the present invention, it is possible to suppress vehicle deflection and improve operability.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the accompanying drawings. The basic concept, main hardware configuration, operating principle, basic control method, and the like of the electric power steering apparatus are known to those skilled in the art, and thus detailed description thereof is omitted.

  FIG. 1 is a schematic diagram of a system configuration of a control device for electric power steering (EPS) according to an embodiment of the present invention. An electric power steering control device (hereinafter referred to as an EPS control device) 1 according to the present embodiment includes a right wheel speed sensor 3 that detects the speed VR of the right wheel and a left that detects the speed VL of the left wheel. A wheel speed sensor 5. The right wheel speed sensor 3 and the left wheel speed sensor 5 are connected to the EPS-ECU 7.

  An EPS-ECU (Electronic Control Unit) 7 and a VGRS-ECU, which will be described later, are composed of a microcomputer, a ROM for storing a control program, a readable / writable RAM for storing calculation results, a timer, a counter, and the like. , An input interface, and an output interface.

  The EPS-ECU 7 is connected to a steering angle sensor 9 that detects a steering angle MA of a steering shaft coupled to a steering wheel, and a vehicle speed sensor 11 that detects a vehicle speed Vv. Further, the EPS-ECU 7 is connected to a steering torque sensor 13 that detects the steering torque MT of the steering shaft, and an EPS gear motor 15 that drives the EPS gear (rack 19). Thus, the EPS-ECU 7 is connected to the right wheel speed VR from the right wheel speed sensor 3, the left wheel speed VL from the left wheel speed sensor 5, the steering angle MA from the steering angle sensor 9, and the vehicle speed sensor. 11, a control signal is transmitted to the EPS gear motor 15 based on the vehicle speed Vv from the steering torque sensor 11 and the steering torque MT from the steering torque sensor 13, and the EPS gear motor 15 is driven and controlled. Further, the EPS-ECU 7 calculates the left and right wheel speed difference ΔV by the following equation (1) based on the right wheel speed VR from the right wheel speed sensor 3 and the left wheel speed VL from the left wheel speed sensor 5.

ΔV = | VR−VL | (1) Further, the EPS-ECU 7 calculates a steering torque differential value ΔMT based on the steering torque MT from the steering torque sensor 13, and based on the steering angle MA from the steering angle sensor 9. Thus, the steering angle differential value ΔMA is calculated.

  Note that a pinion is connected to the steering shaft, and a rack 19 to which the left and right steered wheels are connected to both ends is engaged with the pinion (rack 19 & pinion). The rack 19 is engaged with a gear connected to the EPS gear motor 15, and assist torque is applied to the rack 19 by driving the EPS gear motor 15. In other words, the operation torque input by the steering wheel is transmitted to the steered wheels via the steering shaft, pinion, and rack 19. At this time, the EPS gear motor 15 is driven based on a control signal from the EPS-ECU 7, and an optimum assist torque is applied to the rack 19.

  By the way, while the vehicle is running, the vehicle is deflected (flowed) to the left and right even when the steering angle of the steering is straight, due to a road surface cant, left and right tire performance difference (difference in tire wear speed, difference in tire pressure), and the like. There is. In order to suppress the deflection of the vehicle, the EPS control device 1 according to an embodiment of the present invention includes a vehicle speed Vv, a right wheel speed VR, a left wheel speed VL, a steering angle MA, a vehicle speed Vv, Based on the steering torque MT, (I) MT assist correction control and (II) position correction control are performed.

  Note that (I) MT assist correction control is control in which the EPS gear motor 15 applies assist torque to the rack 19 so that the steering torque MT is reduced when the deflection of the vehicle is detected. Further, (II) position correction control is control for moving and adjusting the rack 19 so that the rack 19 is in the neutral position (rack position correction control). Here, the neutral position of the rack 19 refers to the position of the rack 19 where the wheels are straight. Further, control (main shaft position correction control) may be performed by rotating the main shaft and moving and correcting the rack 19 to the neutral position by the VGRS function. Here, the VGRS (Variable Gear Ratio Steering) function is a function that rotates the steering shaft in addition to the steering by the driver independently of the steering by the driver. More specifically, the VGRS-ECU (VGRS control ECU) 17 controls the VGRS actuator to operate the VGRS gear connected to the VGRS actuator, and “steering angle ∝ (steering angle + rotational angle of the VGRS actuator). ) ”.

  Next, a control method of the EPS control device 1 will be described.

  FIG. 2 is a flowchart of the control routine of the EPS control device 1 according to the present embodiment. This control routine is repeatedly executed every predetermined minute time, for example, every 64 ms.

  As shown in FIG. 2, the EPS-ECU 7 determines whether the vehicle speed Vv from the vehicle speed sensor 11 is greater than a predetermined speed Vv0 (Vv> Vv0) (S100).

  When the EPS-ECU 7 determines that the vehicle speed Vv is greater than the predetermined speed Vv0, the EPS-ECU 7 determines whether Flag2 = 0 (S110). On the other hand, when the EPS-ECU 7 determines that the vehicle speed Vv is equal to or lower than the predetermined speed Vv0, the control routine ends. Here, when Flag2 = 0, it means that the above-mentioned (II) position correction control is being completed, and when Flag2 = 1, it means that the above-mentioned (II) position correction control is being continued. .

  When the EPS-ECU 7 determines that Flag2 = 0, it determines whether the left-right wheel speed difference ΔV is smaller than a predetermined value XV (| ΔV | <XV) (S120). On the other hand, if the EPS-ECU 7 determines that the control Flag2 = 1 and the position correction control is continuing, the process proceeds to the process of (S220) described later.

  When the EPS-ECU 7 determines that the left / right wheel speed difference ΔV is smaller than the predetermined value XV and that the left / right wheel speed difference does not occur, it determines whether Flag1 = 0 (S130). On the other hand, when the EPS-ECU 7 determines that the left-right wheel speed difference ΔV is equal to or greater than the predetermined value XV and the left-right wheel speed difference has occurred, the process proceeds to the process of (S230) described later. Here, when Flag1 = 0, it means that the above-described (I) MT assist correction control is being terminated. Further, when Flag1 = 1, it means that the above (I) MT assist correction control is being continued.

  When the EPS-ECU 7 determines that Flag1 = 0, it determines whether the steering torque MT from the steering torque sensor 13 is greater than the threshold value XMT (| MT |> XMT) (S140). On the other hand, when the EPS-ECU 7 determines that the MT assist correction control is not being performed instead of Flag1 = 0 (Flag1 = 1), the process proceeds to (S160) described later.

  When the EPS-ECU 7 determines that the steering torque MT is greater than the threshold value XMT, the EPS-ECU 7 determines whether the steering torque differential value ΔMT is smaller than the threshold value ΔXMT (| ΔMT | <ΔXMT) (S150). On the other hand, when the EPS-ECU 7 determines that the steering torque MT is equal to or less than the threshold value XMT and the vehicle deflection has not been corrected (normal steering state), the process proceeds to (S290) described later.

  When the EPS-ECU 7 determines that the steering torque differential value ΔMT is smaller than the threshold value ΔXMT, the EPS-ECU 7 determines whether the steering angle MA from the steering angle sensor 9 is greater than the threshold value XMA (| MA |> XMA) (S160). . On the other hand, when the EPS-ECU 7 determines that the steering torque differential value ΔMT is equal to or greater than the threshold value ΔXMT and is in the normal steering state, the process proceeds to the process of (S290) described later.

  When the EPS-ECU 7 determines that the steering angle MA is greater than the threshold value XMA, the EPS-ECU 7 determines whether the steering angle differential value ΔMA is smaller than the threshold value ΔXMA (| ΔMA | <ΔXMA) (S170). On the other hand, when the EPS-ECU 7 determines that the steering angle MA is equal to or less than the threshold value XMA and is in a normal steering state, the process proceeds to the process of (S290) described later.

  When the EPS-ECU 7 determines that the steering angle differential value ΔMA is smaller than the threshold value ΔXMA, the EPS-ECU 7 adds 1 to the counter value N (N = N + 1), and proceeds to the next processing (S190) (S180). On the other hand, when the EPS-ECU 7 determines that the steering angle differential value ΔMA is equal to or greater than the threshold value ΔXMA and is in the normal steering state, the process proceeds to the process of (S290) described later.

  The EPS-ECU 7 determines whether or not the counter value N is greater than or equal to the predetermined value XT (S190). At this time, when the counter value N is equal to or greater than the predetermined value XT, it means that the processing from (S140) to (S170) described above has been continued for a predetermined time or more. Therefore, in the vehicle deflection state, it can be determined that the steering of the vehicle is maintained in the direction opposite to the vehicle deflection direction by the driver of the vehicle and that the vehicle is going straight.

  When the EPS-ECU 7 determines that the counter value N is equal to or greater than the predetermined value XT, Flag1 = 1 is set (S200), and the process proceeds to (S210) described later. On the other hand, when the EPS-ECU 7 determines that the counter value N is smaller than the predetermined value XT and is in the normal steering state, the process proceeds to the process of (S300) described later.

  The EPS-ECU 7 transmits a control signal to the EPS gear motor 15 so as to correct the vehicle deflection, and starts executing the above-described (I) MT assist correction control (S210). As a result, the steering torque MT is reduced in a state where the steering of the vehicle is maintained in a direction opposite to the vehicle deflection direction by the driver of the vehicle and the vehicle is in a state in which the vehicle is going straight, and in a state where the vehicle is deflected. As described above, the assist torque is applied from the EPS gear motor 15 to the rack 19. As a result, the steering force input by the driver via the steering wheel is reduced, operability is improved, and vehicle deflection is appropriately suppressed.

  In the process of (S220), when the EPS-ECU 7 determines that Flag2 = 1 and (II) the position correction control is continuing, the left-right wheel speed difference ΔV is smaller than the predetermined value XV, and the left-right wheel speed difference is Whether or not has occurred is determined.

  When the EPS-ECU 7 determines that the left-right wheel speed difference ΔV is equal to or greater than the predetermined value XV and that the left-right wheel speed difference has occurred, whether the steering torque MT is smaller than the threshold value XMT0 (| MT | <XMT0) or not. Is determined (S230). On the other hand, when the EPS-ECU 7 determines that the left-right wheel speed difference ΔV is smaller than the predetermined value XV and the deflection of the vehicle is suppressed, the process proceeds to (S310) described later.

  When the EPS-ECU 7 determines that the steering torque MT is smaller than the threshold value XMT0 and no steering torque is generated, whether the steering angle MA from the steering angle sensor 9 is smaller than the threshold value XMA0 (| MA | <XMA0) or not. Is determined (S240). On the other hand, when the EPS-ECU 7 determines that the steering torque MT is equal to or greater than the threshold value XMT0 and the steering torque is generated (during steering) and the vehicle is not deflected, the process proceeds to the process of (S310) described later.

  When the EPS-ECU 7 determines that the steering angle MA is smaller than the threshold value XMA0, the steering angle does not occur, and the vehicle is in a deflected state, 1 is added to the counter value N (N = N + 1) (S250). The process proceeds to (S260). In this case, it can be determined that the vehicle has been deflected when the driver puts his hand on the steering wheel or when the driver has released his hand. On the other hand, when the EPS-ECU 7 determines that the steering angle MA is equal to or greater than the threshold value XMA0, the steering angle is generated (during steering), and the vehicle is not deflected, the process proceeds to the processing of (S310) described later.

  In the process of (S260), the EPS-ECU 7 determines whether or not the counter value N is equal to or greater than a predetermined value XT0.

  When the EPS-ECU 7 determines that the counter value N is equal to or greater than the predetermined value XT0, Flag2 = 1 is set (S270), and the process proceeds to (S280) described later. On the other hand, when the EPS-ECU 7 determines that the counter value N is smaller than the predetermined value XT0, the process proceeds to the process of (S320) described later.

  The EPS-ECU 7 transmits a control signal to the EPS gear motor 15 so as to correct the vehicle deflection, and starts executing the above-described (II) position correction control (S280). Specifically, the EPS-ECU 7 transmits a control signal to the EPS gear motor 15 and adjusts so that the rack 19 moves to the neutral position. Thereby, even in a state where the steering torque MT is not generated, such as a state where the driver's hand is lightly attached to the steering wheel, and in a state where the vehicle is deflected, the deflection of the vehicle is automatically suppressed, The operability of the vehicle is improved.

  In the process of (S290), the EPS-ECU 7 sets N = 0. Next, the EPS-ECU 7 sets Flag1 = 0 (S300), thereafter ends the MT assist correction control (S305), and ends the processing of the control routine.

  In the process of (S310), the EPS-ECU 7 sets N = 0. Next, the EPS-ECU 7 sets Flag2 = 0 (S320), thereafter ends the position correction control (S330), and ends the processing of the control routine.

  The threshold values XMA, XMA0, ΔXMA, XMT, XMT0, ΔXMT, XT0, and Vv0 are set and stored in the EPS-ECU 7 in advance.

  As described above, the steering torque MT is reduced in a state where the steering of the vehicle is maintained in the direction opposite to the vehicle deflection direction by the vehicle driver so that the vehicle straight-ahead state is maintained and the vehicle is deflected. In addition, an assist torque is applied from the EPS gear motor 15 to the rack 19. As a result, the steering force input by the driver via the steering wheel is reduced, the operability is improved, and the deflection of the vehicle is appropriately suppressed.

  Further, the EPS-ECU 7 transmits a control signal to the EPS gear motor 15 and adjusts so that the rack 19 moves to the neutral position. Thereby, even in a state where the steering torque MT is not generated, such as a state where the driver's hand is lightly attached to the steering wheel, and in a state where the vehicle is deflected, the deflection of the vehicle is automatically suppressed, The operability of the vehicle is improved.

  As mentioned above, although the best mode for carrying out the present invention has been described using one embodiment, the present invention is not limited to such one embodiment, and within the scope not departing from the gist of the present invention, Various modifications and substitutions can be made to the above-described embodiment.

  The present invention can be used for an electric power steering control device. The appearance, weight, size, running performance, etc. of the vehicle to be mounted are not limited.

It is the schematic of the system configuration | structure of the control apparatus for electric power steering (EPS) which concerns on one Example of this invention. It is a flowchart of the control routine of the control device for EPS concerning this one Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control apparatus for electric power steering 3 Right wheel speed sensor 5 Left wheel speed sensor 7 EPS-ECU
9 Steering angle sensor 11 Vehicle speed sensor 13 Steering torque sensor 15 EPS gear motor 19 Rack

Claims (5)

Right wheel speed detecting means for detecting the right wheel speed of the vehicle;
Left wheel speed detecting means for detecting a left wheel speed of the vehicle;
A speed difference calculating means for calculating a speed difference between the right wheel speed detected by the right wheel speed detecting means and the left wheel speed detected by the left wheel speed detecting means;
By adjusting the assist torque during steering based on the speed difference calculated by the speed difference calculating means, the method for suppressing the deflection of the vehicle, and moving and adjusting the rack to the neutral position, A control unit for power steering , comprising: a control unit that suppresses the deflection of the vehicle by any one of the methods for suppressing the deflection of the vehicle ,
The power steering control device, wherein the control means changes a method of suppressing the deflection according to the speed difference calculated by the speed difference calculation means. The power steering control device according to claim 1,
The control means includes
(A) When the speed difference calculated by the speed difference calculating means is smaller than a predetermined value, the deflection of the vehicle is suppressed by adjusting the assist torque during steering;
(B) When the speed difference calculated by the speed difference calculating means is equal to or greater than a predetermined value, the deflection of the vehicle is suppressed by moving and adjusting the rack to a neutral position. . The power steering control device according to claim 1 or 2,
The vehicle further includes an operation state determination means for determining whether the steering is maintained by the driver of the vehicle and whether or not the vehicle straight state is about to be maintained,
The power steering control device according to claim 1, wherein when the operation state determination unit determines that the straight traveling state of the vehicle is to be maintained, the control unit suppresses deflection of the vehicle. The power steering control device according to claim 3,
A steering torque detecting means for detecting a steering torque of the vehicle;
The power steering control device according to claim 1, wherein when the steering torque detected by the steering torque detection means is greater than or equal to a predetermined torque, the operation state determination means determines that the vehicle straight-ahead state is about to be maintained. The power steering control device according to any one of claims 1 to 4,
The control device for power steering, wherein the control means controls to reduce the steering torque.

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