JP6256319B2 - Power steering control device - Google Patents

Description

  The present invention relates to a power steering control device for a vehicle such as an automobile, and more particularly to a power steering control device that performs lane keeping assist control (lane keep assist) control.

  The power steering device applies an assist torque to the steering unit, thereby reducing the steering burden on the driver, that is, the burden when the driver rotates the steering wheel, and improves the steering feeling. The power steering control device calculates a target assist torque for reducing the driver's steering burden and improving the steering feeling, and controls the power steering device so that the assist torque becomes the target assist torque.

  Lane maintenance support control has been already put into practical use, in which the steering wheel is steered using assist torque generated by the power steering device, thereby causing the vehicle to travel along the traveling lane. A lane keeping assist control device that performs lane keeping assist control calculates a target rudder angle of a steered wheel for causing a vehicle to travel along a traveling lane, and calculates a lane keeping assist control amount of assist torque based on the target rudder angle. To do. The power steering control device is a basic control amount for reducing the driver's steering burden, an auxiliary control amount for improving the steering feeling (such as a return torque control amount for returning the steering wheel to the reference steering angle position). And the target assist torque is calculated as the sum of the lane keeping assist control amount.

  The position of the reference steering angle at which the steering wheel is returned by the return torque control amount is a position where the steering angle is 0, that is, a straight traveling position of the vehicle. However, when the lane keeping assist control is being performed, it is preferable that the return torque control amount does not affect the steering angle of the steered wheels to the target rudder angle of the lane keeping assist control. Therefore, for example, in Patent Document 1 below, when the lane keeping assist control is performed, the position of the reference steering angle is set to the target steering angle corresponding to the target rudder angle of the lane keeping assist control. A configured power steering control device is described.

JP-A-11-198844

[Problems to be Solved by the Invention]
According to the power steering control device described in the above-mentioned Patent Document 1, the torque by the return torque control amount acts to urge the steering wheel to the position of the steering angle corresponding to the target steering angle of the lane keeping assist control. Therefore, when the lane keeping assist control is being performed, the steered angle of the steered wheels is set to the target rudder angle of the lane keeping assist control as compared with the case where the reference steering angle is at the position where the steering angle is 0. It can be controlled efficiently and stably.

  However, when the vehicle travels with the steered wheels being steered, self-aligning torque acts on the steered wheels, and the self-aligning torque acts to urge the steering wheel to a position where the steering angle is 0. . Therefore, the self-aligning torque acts in the same direction as the torque by the return torque control amount when the steering angle is larger than the target steering angle of the lane keeping assist control, but the steering angle is 0 and the lane. When the value is between the target steering angle of the maintenance support control, it acts in the direction opposite to the torque by the return torque control amount. Therefore, when the driver steers in a situation where the steering wheel is controlled to the target steering angle position of the lane keeping assist control, the steering reaction force greatly differs depending on whether the steering is increased or decreased. This makes it easier for the driver to feel uncomfortable.

  In view of the above-described problems in the conventional power steering control device configured to set the reference steering angle position to the target steering angle position of the lane keeping assist control when the lane keeping assist control is performed. It has been made. The main problem of the present invention is that even if the driver steers during execution of the lane keeping assist control, the possibility that the driver feels uncomfortable due to the great difference in the steering reaction force depending on the steering direction is reduced. It is to be.

[Means for Solving the Problems and Effects of the Invention]
According to the present invention, the main problems described above are a power steering device that applies assist torque to the steering unit, and a neutral position of the steering wheel is set to 0, and a steering angle is set as a rotation angle of the steering wheel from the neutral position. When the steering angle detection device to detect and the execution condition of the lane keeping assist control are satisfied, the target steering angle of the steered wheels for causing the vehicle to travel along the traveling lane is calculated, and based on the target steering angle A lane keeping assist control device for calculating a lane keeping assist control amount for causing the vehicle to travel along the driving lane, and a basic torque control amount for reducing a driver's steering burden and a steering wheel to a reference steering angle position. A return torque control amount is calculated, and the assist torque control amount is calculated based on the lane keeping assist control amount, the basic torque control amount, and the return torque control amount. A power steering control device having an assist torque control device for controlling torque, wherein the assist torque control device sets the reference steering angle to 0 when an execution condition of the lane keeping assist control is not satisfied. When the execution condition of the lane keeping assist control is satisfied, the reference steering angle is set to a target steering angle corresponding to the target steering angle, and the steering angle detected by the steering angle detection device When the steering angle detected by the steering angle detection device is a value on the side of 0 with respect to the target steering angle even if the difference between the steering angle detection device and the target steering angle is the same, the steering angle detection device Compared with the case where the steering angle detected by the above is a value on the side opposite to 0 with respect to the target steering angle, the magnitude of the return torque control amount is increased. It is achieved by the ring control unit.

  According to the above configuration, when the execution condition for the lane keeping support control is not satisfied, the reference steering angle is set to 0, and when the execution condition for the lane keeping support control is satisfied, the reference steering is performed. The angle is set to the target steering angle corresponding to the target steering angle of the lane keeping assist control. Further, when the execution condition of the lane keeping assist control is satisfied, the steering angle is 0 with respect to the target steering angle even if the difference between the detected steering angle and the target steering angle is the same. When the value is a value on the side, the magnitude of the return torque control amount is made larger than when the steering angle is a value on the side opposite to 0 with respect to the target steering angle. Therefore, when the steering angle is a value between 0 and the target steering angle, the effect of the self-aligning torque acting in the direction opposite to the torque by the return torque control amount on the steering reaction force is reduced. be able to. Therefore, when the driver steers in a situation where the steering wheel is controlled to the position of the target steering angle of the lane keeping assist control or a position near the target steering angle, the steering reaction force increases depending on whether the steering is turned up or down. It is possible to reduce the difference and the possibility that the driver feels uncomfortable due to the difference.

It is explanatory drawing which shows the outline of one Embodiment of the power steering control apparatus by this invention. It is a flowchart which shows the assist torque control routine in embodiment. 7 is a map for calculating a target basic assist torque Tab based on the steering torque T and the vehicle speed V. 7 is a map for calculating a first target return torque Tr1 based on the steering angle θ and the vehicle speed V. In a situation where the target steering angle θlka of the LKA control is a positive value larger than the reference value θc, the map (solid line) for calculating the second target return torque Tr2 is compared with the conventional case (broken line). FIG. In a situation where the target steering angle θlka of LKA control is a negative value smaller than the reference value −θc, the map (solid line) for calculating the second target return torque Tr2 is compared with the conventional case (broken line). FIG. An example of the change in the second target return torque Tr2 when the LKA control starts and ends, along with the change in the correction coefficient K (lowermost stage), in the case of the embodiment (second stage) and the correction example ( It is explanatory drawing shown about 3rd step | paragraph.

  Hereinafter, preferred embodiments will be described in detail with reference to the accompanying drawings. In the following description, the lane keeping assist control is abbreviated as “LKA control”.

  FIG. 1 is an explanatory diagram showing an outline of one embodiment of a power steering control device 10 according to the present invention. The power steering control device 10 includes an electric power steering device 12, an assist torque control electronic control device 14, an LKA control electronic control device 16, and a steering angle sensor 52 as a steering angle detection device. .

  The power steering device 12 is configured as a column assist type electric power steering device. The power steering device according to the present invention may be another type of power steering device as long as the assist torque can be controlled, such as a rack coaxial type rack-assisted electric power steering device.

  In FIG. 1, the power steering device 12 is applied to a steering unit 18. The steering unit 18 includes a steering wheel 20 that is operated by a driver, an upper steering shaft 22 that rotates together with the steering wheel 20, an intermediate shaft 24, and a steering mechanism 26. The intermediate shaft 24 is connected to the lower end of the upper steering shaft 22 via the universal joint 28 at the upper end, and is connected to the pinion shaft 32 of the steering mechanism 26 via the universal joint 30 at the lower end.

  The steering mechanism 26 includes a rack and pinion device 34 and tie rods 36L and 36R. The rack and pinion device 34 converts the rotation of the pinion shaft 32 into a linear motion of the rack bar 38 in the lateral direction of the vehicle, The reverse conversion is performed. The tie rods 36L and 36R are pivotally attached to the tip of the rack bar 38 at the inner ends, and the outer ends of the tie rods 36L and 36R are knuckle arms 42L provided on carriers (not shown) of the left and right front wheels 40L and 40R. And 42R.

  Therefore, the rotational displacement and rotational torque of the steering wheel 20 are converted into the swing displacement and swing torque around the kingpin shafts (not shown) of the front wheels 40L and 40R by the steering mechanism 26 and the like to the front wheels 40L and 40R. Communicated. The swing displacement and swing torque around the kingpin shaft received by the left and right front wheels 40L and 40R from the road surface 44 are transmitted to the steering wheel 20 by the steering mechanism 26 and the like as rotational displacement and rotational torque, respectively.

  The power steering device 12 includes an electric motor 48 and a conversion device 50. Although not shown in FIG. 1, the conversion device 50 includes a worm gear fixed to the rotating shaft of the electric motor 48 and a worm wheel fixed to the upper steering shaft 22. The rotational torque of the electric motor 48 is converted into rotational torque around the upper steering shaft 22 by the conversion device 50 and transmitted to the upper steering shaft 22 as assist torque. Therefore, the power steering device 12 applies assist torque to the upper steering shaft 22 of the steering unit 18.

  The upper steering shaft 22 is provided with a steering angle sensor 52 and a torque sensor 54, and the assist torque control electronic control device 14 receives a steering angle θ and a steering torque T from the steering angle sensor 52 and the torque sensor 54, respectively. The signal shown is input. The electronic control device 14 also receives a signal indicating the vehicle speed V from the vehicle speed sensor 56. The electronic control unit 14 controls the assist torque Ta to be equal to the target assist torque Taat by calculating the target assist torque Tat according to the flowchart shown in FIG.

  In the embodiment, the assist torque control electronic control unit 14 calculates a basic control amount for reducing the driver's steering burden and an auxiliary control amount for improving the steering feeling, as will be described in detail later. . The auxiliary control amount in the embodiment is a return control amount for returning the steering wheel 20 to the position of the reference steering angle. Further, the electronic control unit 14 calculates the target assist torque Tat as the sum of the basic control amount and the auxiliary control amount and the LKA control torque Tlka calculated by the LKA control electronic control unit 16. The auxiliary control amount may include a friction control amount and / or a damping control amount.

  The LKA control electronic control device 16 receives a signal indicating image information in front of the vehicle taken by the CCD camera 58 and selects whether or not the selection switch 60 is turned on, that is, execution of LKA control. A signal indicating whether or not it has been input is input. The electronic control unit 16 analyzes the image information in front of the vehicle to identify the traveling lane, curves the curvature of the traveling lane, the lateral offset of the vehicle with respect to the center line of the traveling lane, and the yaw angle (with respect to the center line of the traveling lane). The angle formed by the center axis in the longitudinal direction of the vehicle is calculated.

  Further, the electronic control unit 16 calculates a target lateral acceleration of the vehicle for causing the vehicle to travel along the traveling lane based on the curve curvature, the lateral offset of the vehicle, and the yaw angle, and the lateral acceleration of the vehicle is calculated as the target lateral acceleration. To calculate the target steering angle δft of the front wheels 40L and 40R. Further, the electronic control unit 16 calculates the LKA control torque Tlka as an assist torque component for turning the front wheels so that the steering angles of the front wheels 40L and 40R become the target steering angle δft. The LKA control torque Tlka may be calculated in any manner as long as it is calculated as a torque for causing the vehicle to travel along the travel lane so as not to depart from the travel lane. Regarding the calculation of the LKA control torque Tlka, refer to, for example, Japanese Patent Application Laid-Open No. 2007-30612 related to the applicant of the present application if necessary.

  Each of the electronic control devices 14 and 16 includes a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other via a bidirectional common bus. You may remember a map. The electronic control units 14 and 16 exchange necessary signals with each other as necessary. Further, the steering angle sensor 52 and the torque sensor 54 detect the steering angle θ and the steering torque T, respectively, with the case of steering in the right turn direction of the vehicle as positive. The same applies to calculation values such as a target basic assist torque Ta and a target steering angle θt, which will be described later. In particular, the steering angle θ and the target steering angle θt become 0 when the steering wheel 20 is in the neutral position, that is, the straight traveling position of the vehicle.

  Next, an assist torque control routine executed by the assist torque control electronic control device 14 will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is repeatedly executed at predetermined time intervals when an ignition switch (not shown) is on. In the following description, the assist torque control according to the flowchart shown in FIG. 2 is simply referred to as “control”.

  First, in step 10, a signal indicating the steering angle θ detected by the steering angle sensor 52 and a signal indicating the vehicle speed V detected by the vehicle speed sensor 56 are read. Further, in step 10, from the LKA control electronic control unit 16, a signal indicating whether or not the selection switch 60 is ON, a signal indicating the target steering angle δft of the front wheels 40L and 40R, and a signal indicating the LKA control torque Tlka. Is loaded

  In step 20, based on the vehicle speed V, a map for calculating the target basic assist torque Tab is selected from the map group shown in FIG. Furthermore, a target basic assist torque Tab for reducing the driver's steering burden is calculated from the selected map based on the steering angle θ. As shown in FIG. 3, the target basic assist torque Tab is calculated so as to increase as the steering angle θ increases, and to decrease as the vehicle speed V increases.

  In step 30, based on the vehicle speed V, a map for calculating the first target return torque Trt1 is selected from the map group shown in FIG. Further, based on the steering angle θ, a first target return torque Trt1 for returning the steering wheel 20 to the neutral position that is the position of the reference steering angle (θ = 0) is calculated from the selected map. As shown in FIG. 4, the first target return torque Trt1 is calculated such that it increases as the steering angle θ increases, and increases as the vehicle speed V decreases. .

  In step 40, it is determined whether or not the execution condition of the LKA control is satisfied by determining whether or not the selection switch 60 is on and other preset conditions are satisfied. When a negative determination is made, control proceeds to step 70, and when an affirmative determination is made, control proceeds to step 50.

  In step 50, the target steering angle θlka of the LKA control corresponding to the target steering angle δft of the front wheels 40L and 40R calculated by the LKA control electronic control device 16 and read in step 10 is the target steering angle δft and the steering gear ratio. Is calculated based on

  In step 60, whether or not the calculation of the second target return torque Trt2 is unnecessary by determining whether or not the absolute value of the target steering angle θlka of the LKA control is less than the reference value θc (positive constant). Is determined. When an affirmative determination is made, the second target return torque Trt2 is set to 0 at step 70, and when a negative determination is made, control proceeds to step 80.

  In step 80, it is determined whether or not the target steering angle θlka for LKA control is a positive value. When a negative determination is made, control proceeds to step 100, and when an affirmative determination is made, control proceeds to step 90.

  In step 90, based on the map M1 (one-dot chain line) used for the calculation of the first target return torque Trt1 in step 30 and the target steering angle θlka for LKA control, a map M3 indicated by a solid line in FIG. Is set as follows. Further, a second target return torque Trt2 is calculated from the map M3 based on the steering angle θ.

  First, the map M1 is corrected so that the steering angle at the position where the steering wheel 20 is returned becomes the target steering angle θlka for LKA control, so that a map M2 indicated by a broken line in FIG. 5 is set. The map M2 may be considered to be set by translating the map M1 to the right by θlka along the axis of the steering angle θ, and thus is parallel to the map M1.

  Next, as shown in FIG. 5, in a region where the steering angle θ detected by the steering angle sensor 52 is equal to or larger than the target steering angle θlka of the LKA control, the value of the map M3 is the same as the value of the map M2. Set to a value. In a region where the steering angle θ is not less than “θlka−Δθ” and less than θlka, the value of the map M3 is set to K times the value of the map M2. Further, the value of the map M2 when the steering angle θ is “θlka−Δθ” is Trt21. In the region where the steering angle θ is less than “θlka−Δθ”, the value of the map M3 is “the value of the map M2 · K + Trt21”. "Is set.

  In step 100, a map M5 shown by a solid line in FIG. 6 based on the map M1 (dashed line) used for the calculation of the first target return torque Trt1 in step 30 and the target steering angle θlka of LKA control. Is set as follows. Further, a second target return torque Trt2 is calculated from the map M5 based on the steering angle θ.

  First, the map M1 is corrected so that the steering angle at the position where the steering wheel 20 is returned becomes the target steering angle θlka for LKA control, so that a map M4 indicated by a broken line in FIG. 6 is set. The map M4 may be considered to be set by translating the map M1 to the left by θlka along the axis of the steering angle θ and is therefore parallel to the map M1.

  Next, as shown in FIG. 6, in a region where the steering angle θ detected by the steering angle sensor 52 is equal to or smaller than the target steering angle θlka of the LKA control, the value of the map M5 is the same as the value of the map M4. Set to a value. In the region where the steering angle θ is larger than θlka and equal to or smaller than “θlka + Δθ”, the value of the map M5 is set to K times the value of the map M4. Further, the value of the map M4 when the steering angle θ is “θlka + Δθ” is Trt22, and in the region where the steering angle θ is larger than “θlka + Δθ”, the value of the map M5 is set to “value of the map M4 · K + Trt22”. Is done.

  In steps 90 and 100, the steering angle deviation Δθ may be variably set in accordance with the target steering angle θlka as a positive value equal to or smaller than the target steering angle θlka of the LKA control. The correction coefficient K may be a positive constant value regardless of the target steering angle θlka.

  In step 110, the target assist torque Tat is calculated as the sum Tab + Trt1 + Trt2 + Tlka of the target basic assist torque Tab, the first target return torque Trt1, the second target return torque Trt2, and the LKA control torque Tlka.

  In step 120, the power steering device 12 is controlled based on the target assist torque Ta so that the assist torque Ta of the power steering device 12 becomes the target assist torque Ta.

  As will be understood from the above description, in step 20, the target basic assist torque Tab for reducing the driver's steering burden is calculated, and in step 30, the first target return for returning the steering wheel 20 to the neutral position. Torque Trt1 is calculated.

  If it is determined in step 40 that the execution condition of the LKA control is satisfied, and it is determined in step 60 that the absolute value of the target steering angle θlka of the LKA control is greater than or equal to the reference value θc, in steps 80 to 100, A second target return torque Trt2 is calculated. The second target return torque Trt2 is a torque for returning the steering wheel 20 to the reference steering angle position with the position of the target steering angle θlka as the reference steering angle position. As shown in FIGS. 5 and 6, the second target return torque Trt2 is obtained from maps M2 and M4 when the steering angle θ is a value on the side of 0 with respect to the target steering angle θlka of the LKA control. Is also calculated as a large value.

  Therefore, the magnitude of the return torque can be increased in a situation where the self-aligning torque acts in a direction opposite to the return torque for returning the steering wheel 20 to the reference steering angle position. Therefore, compared to the case where the magnitude of the return torque is not corrected as described above, when the driver performs steering in a situation where the steering angle θ is a value at or near the target steering angle θlka, It is possible to reduce a sense of incongruity caused by a great difference in steering reaction force.

  In particular, according to the above-described embodiment, when the target steering angle θlka is a positive value, the value of the map M3 is “the value of the map M2 · in the region where the steering angle θ is less than“ θlka−Δθ ”. K + Trt21 ". When the target steering angle θlka is a negative value, the value of the map M5 is “the value of the map M4 · K + Trt21” in the region where the steering angle θ is larger than “θlka + Δθ”. Thus, in a region where the target steering angle θlka is a positive value and the steering angle θ is less than “θlka−Δθ”, and a region where the target steering angle θlka is a negative value and the steering angle θ is larger than “θlka + Δθ”, It is possible to prevent the return torque from becoming excessively large.

  Further, since the magnitude of the self-aligning torque when the steering angle θ is small is small, the self-aligning torque acts in a direction opposite to the return torque for returning the steering wheel 20 to the reference steering angle position. The impact of doing is minimal. According to the embodiment described above, even if the LKA control is being executed, if the absolute value of the target steering angle θlka of the LKA control is less than the reference value θc, an affirmative determination is made in step 60 and the second target return is performed. The torque Trt2 is set to 0 without being calculated. Therefore, in the situation where the effect of the reverse acting directions of the self-aligning torque and the return torque is slight, the control can be simplified by omitting the correction of the return torque.

  Note that the second target return torque Trt2 may be calculated in steps 80 to 100 even when the determination in step 60 is omitted and the absolute value of the target steering angle θlka is less than the reference value θc.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. This will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the target assist torque Tat is the target basic assist torque Tab and the first and second target return torques Tr1 that are return control amounts for returning the steering wheel 20 to the reference steering angle position. And Tr2. However, as long as the target assist torque Tat includes the first and second target return torques Tr1 and Tr2, the damping control for attenuating the vibration change of the target friction torque Tft and / or the steering torque as the friction control amount. It may be calculated as a value including the target damping torque Tdt as a quantity.

  In the above-described embodiment, the reference value θc and the correction coefficient K are positive constants. However, the higher the vehicle speed V, the greater the self-aligning torque, and the effect of acting in the opposite direction to the return torque for returning the steering wheel 20 to the reference steering angle position becomes significant. Therefore, at least one of the reference value C and the correction coefficient K may be variably set according to the vehicle speed V so as to increase as the vehicle speed V increases.

  In the above-described embodiment, the target steering angle is the target steering angle θlka for LKA control. However, the target rudder angle of the steered wheels for stabilizing the traveling motion of the vehicle is calculated, and the vehicle is controlled using the assist torque so that the rudder angle of the steered wheels becomes the target rudder angle. In this case, the target steering angle may be set to a target steering angle corresponding to the target steering angle of the steered wheels for motion control.

  FIG. 7 shows an example of the change in the second target return torque Tr2 when the LKA control starts and ends, along with the change in the correction coefficient K (bottom stage), the embodiment (second stage), and the correction. It is explanatory drawing shown about the case (third stage) of an example. In the second stage and the third stage of FIG. 7, the solid line and the broken line indicate a case where the second target return torque Tr2 becomes a positive value and a negative value when the LKA control is being performed, respectively.

  In the above-described embodiment, as shown in the second stage of FIG. 7, the second target return torque Tr2 changes abruptly depending on whether or not the LKA control is being executed. Therefore, as shown in the third stage of FIG. 7, when the LKA control is started and ended, the correction coefficient K gradually changes, whereby the magnitude of the second target return torque Tr2 is also increased. Embodiments may be modified to change gradually. In particular, when the LKA control is finished, the correction coefficient K is not changed when the driver is not steering, or the change rate of the correction coefficient K is reduced, so that the driver corrects when the steering is not performed. It is preferable to reduce the possibility of feeling uncomfortable due to the coefficient K changing.

DESCRIPTION OF SYMBOLS 10 ... Power steering control device, 12 ... Power steering device, 14 ... Electronic control device for assist torque control, 16 ... Electronic control device for LKA control, 20 ... Steering wheel, 26 ... Steering mechanism, 52 ... Steering angle sensor, 54 ... Torque sensor 56 ... Vehicle speed sensor 58 ... CCD camera 60 ... Select switch

Claims (1)

A power steering device for applying assist torque to the steering unit;
A steering angle detection device for detecting a steering angle as a rotation angle of the steering wheel from the neutral position, wherein the neutral position of the steering wheel is 0;
When the execution condition of the lane keeping assist control is established, the target rudder angle of the steered wheels for causing the vehicle to travel along the traveling lane is calculated, and the vehicle is moved along the traveling lane based on the target rudder angle. A lane keeping support control device for calculating a lane keeping support control amount for running;
A basic torque control amount that reduces the driver's steering burden and a return torque control amount that returns the steering wheel to the reference steering angle position are calculated, and the lane keeping assist control amount, the basic torque control amount, and the return torque control amount are calculated. An assist torque control device for controlling the assist torque based on the power steering control device,
The assist torque control device sets the reference steering angle to 0 when the lane keeping support control execution condition is not satisfied, and when the lane keeping support control execution condition is satisfied. The reference steering angle is set to a target steering angle corresponding to the target steering angle, and the magnitude of the difference between the steering angle detected by the steering angle detection device and the target steering angle is the same. When the steering angle detected by the steering angle detection device is a value on the side of 0 with respect to the target steering angle, the steering angle detected by the steering angle detection device is opposite to 0 with respect to the target steering angle. A power steering control device configured to increase the magnitude of the return torque control amount as compared with a value on the side.

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