JP2013141954A - Steering neutral point setting device, and steering neutral point setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering neutral point setting device and a steering neutral point setting method, capable of improving setting accuracy of the neutral point of the steering.SOLUTION: When an absolute value of a steering angle based on a yaw rate StrYr is less than a straight traveling determination value Strth (step S16: YES), a control device carries out update processing for setting a neutral point StrC of steering based on a detection signal output from a steering angle sensor at this time and for changing the straight traveling determination value Strth based on the steering angle based on the yaw rate StrYr at the time point when the neutral point StrC is set (steps S17 and S18). The control device carries out update processing each time an absolute value of the steering angle based on the yaw rate StrYr is less than the straight traveling determination value Strth at the time point.

Description

  The present invention relates to a neutral point setting device and a neutral point setting method for steering a vehicle.

  As vehicle control using the steering angle of the steering as a parameter, ESC (Electronic Stability Control) that adjusts the braking force for each wheel in order to eliminate oversteer and understeer generated in the vehicle is known. In such vehicle control, since the relative angle with respect to the neutral point of the steering is used as the steering angle, the setting of the neutral point is important for improving the control accuracy. The “steering neutral point” refers to the rotational position of the steering wheel at which the yaw moment generated in the traveling vehicle is substantially “0 (zero)”.

  Patent Document 1 discloses a method for setting a neutral point of steering. That is, in this method, the yaw rate is detected based on the detection signal output from the yaw rate sensor while the vehicle is traveling, and it is determined whether or not the absolute value of the yaw rate is less than a predetermined determination value. If the absolute value of the yaw rate remains below the determination value for a predetermined time or more, it is determined that the vehicle is in a straight traveling state, and the neutral position of the steering is determined based on the detection signal output from the steering angle sensor at that time. A point is set. Thereafter, the steering angle of the steering is acquired as a displacement amount with the set neutral point as a reference.

JP-A-2-144262

  By the way, as a steering angle sensor for detecting the steering angle of the steering, a detection signal based on the steering position of the steering at the time when the operation switch for permitting driving of a power source such as an engine is turned on is used. Sensors that output (hereinafter also referred to as “relative angle sensors”) and sensors that output detection signals based on a preset neutral point (hereinafter also referred to as “absolute angle sensors”) are known. Yes.

  In a vehicle equipped with a relative angle sensor, the neutral point may not be set immediately after the operation switch is turned on. In this state, the steering angle of the steering with reference to the neutral point cannot be acquired, and therefore vehicle control using the steering angle of the steering as a parameter cannot be performed. Therefore, it is desirable to set the steering neutral point early after the vehicle starts to travel.

  Thus, in order to set the neutral point early, it is conceivable to set the determination value to a large value. As a result, it is easy to determine that the vehicle is traveling straight, and the steering neutral point is set early after the vehicle starts to travel. However, the setting accuracy of the set neutral point tends to vary. When the set neutral point deviates from the actual steering neutral point, the accuracy of vehicle control using the steering angle of the steering as a parameter may be lowered.

  The setting of the steering neutral point is important not only for the relative angle sensor but also for the absolute angle sensor. That is, the absolute angle sensor is attached to the vehicle so that a preset neutral point coincides with the actual neutral point of steering. However, an error may occur between a neutral point preset in the sensor and an actual neutral point of the steering due to an attachment error of the sensor at this time. In this case, an offset error based on the mounting error occurs between the steering angle of the steering acquired based on the detection signal from the absolute angle sensor and the actual steering angle of the steering. Therefore, it is preferable to set the steering neutral point with high accuracy even in a vehicle equipped with an absolute angle sensor.

  The present invention has been made in view of such circumstances. An object of the present invention is to provide a steering neutral point setting device and a steering neutral point setting method capable of improving the setting accuracy of the steering neutral point.

  In order to achieve the above object, the present invention provides a steering neutral point setting device for setting a neutral point (StrC) of a steering (10) of a vehicle, and a value corresponding to a yaw moment generated in the vehicle. When the absolute value of the vehicle state value (StrYr, Yr) is less than the straight traveling determination value (Strth) that is a criterion for determining whether or not the vehicle is traveling straight (S16: YES), the steering angle at that time The neutral point (StrC) of the steering (10) is set based on the detection signal output from the sensor (SE1), and the vehicle state value (StrYr, Yr) at the time when the neutral point (StrC) is set is set. An update process (S17, S18) for changing the straight traveling determination value (Strth) is performed, and the update process (S17, S18) is changed to the acquired vehicle state value (St Yr, Yr absolute value of) is summarized in that performed for each be less than straight travel determination value at that time (Strth).

  According to the above configuration, the update process for setting the steering neutral point and changing the straight-ahead determination value is performed every time the vehicle state value becomes less than the straight-ahead determination value at that time. As a result, each time the update process is performed, the straight-ahead determination value is changed so that its absolute value becomes smaller. As a result, each time the update process is performed, the criterion for determining whether or not the vehicle is traveling straight becomes stricter. As described above, since the neutral point of the steering is set under conditions where the criterion for determining whether or not the vehicle is traveling straight is severe, the setting accuracy of the neutral point can be improved.

  In the present invention, when the change amount (ΔYr) of the lateral force applied to the vehicle is equal to or greater than the change amount reference value (ΔYrth) (S14: NO), it is preferable to prohibit the update process (S17, S18).

  When the lateral force applied to the vehicle does not change greatly, or when the lateral force is constant, the yaw moment required by the driver (hereinafter also referred to as “requested yaw moment”) is the actual yaw moment generated in the vehicle. And close to the value. However, when the lateral force changes greatly, a change in the actual yaw moment generated in the vehicle tends to be delayed with respect to a change in the requested yaw moment due to steering by the driver or an accelerator operation. Therefore, there is a possibility that a divergence has occurred between the requested yaw moment and the actual yaw moment. Therefore, in the present invention, when the lateral force applied to the vehicle changes greatly, execution of the update process is prohibited. Therefore, it is possible to improve the setting accuracy of the neutral point of the steering as compared with the case where the update process is performed even when the lateral force changes greatly.

  In the present invention, the vehicle state value is calculated based on a yaw rate (Yr) generated in the vehicle or estimated to be generated in the vehicle and a vehicle body speed (VS) of the steering (10). When it is the steering angle estimated value (StrYr) and the steering angle estimated value (StrYr) is less than the straight traveling determination value (Strth) at that time (S16: YES), the updating process (S17, S18) is performed. Is preferred.

  The yaw moment generated in the vehicle changes not only with the steering angle of the steering but also with the vehicle body speed of the vehicle. Therefore, even if it is determined that the yaw moment is the vehicle state value and the vehicle is in the straight traveling state based on the yaw moment, the absolute value of the actual steering angle of the steering is relatively large when the vehicle body speed is low. It can happen. Even if the steering neutral point is set based on the detection signal from the steering angle sensor at this time, the neutral point may be deviated from the actual neutral point.

  In this regard, in the present invention, the steering angle estimated value calculated based on the yaw rate and the vehicle body speed is set as the vehicle state, and it is determined whether or not the vehicle is in the straight traveling state based on the steering angle estimated value. For this reason, when the vehicle body speed is low and the absolute value of the actual steering angle of the steering is large, the possibility that the update process is performed is reduced. In other words, when the update process is performed, the absolute value of the actual steering angle of the steering is likely to be small. Therefore, compared with the case where the yaw moment generated in the vehicle is used as the vehicle state value, the setting accuracy of the neutral point of the steering can be improved.

  The present invention is a steering neutral point setting method for setting a neutral point (StrC) of a steering (10) of a vehicle, and is a vehicle state value (StrYr) that is a value corresponding to a yaw moment generated in the vehicle. ) Is less than the straight traveling determination value (Strth) which is a criterion for determining whether or not the vehicle is traveling straight (S16: YES), it is output from the steering angle sensor (SE1) at that time. An updating step for setting the neutral point (StrC) of the steering wheel (10) based on the detection signal and changing the straight traveling determination value (Strth) based on the vehicle state value (StrYr) at the time of setting the neutral point (StrC). (S17, S18), and the updating step (S17, S18) is determined by the absolute value of the acquired vehicle state value (StrYr) being the straight-ahead determination value at that time. And gist be executed every time less than Strth).

According to the said structure, the effect | action and effect equivalent to the said neutral point setting apparatus of a steering can be acquired.
In order to explain the present invention in an easy-to-understand manner, it has been described in association with the reference numerals of the drawings showing the embodiments, but it goes without saying that the present invention is not limited to the embodiments.

The block diagram which shows schematic structure of the vehicle carrying the control apparatus which is one Embodiment of the neutral point setting apparatus of the steering concerning this invention. The flowchart which shows the process routine for setting the neutral point of steering. (A) is a timing chart showing the comparison between the actual steering angle of the steering wheel and the yaw rate conversion steering angle, (b) is a timing chart showing the amount of change in the yaw rate, and (c) is updated with the neutral point of the steering and the straight traveling judgment value. The timing chart which shows a mode that it is performed.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment in which a steering neutral point setting device of the present invention is embodied will be described with reference to FIGS. In the following description of the present specification, the traveling direction (forward direction) of the vehicle is assumed to be the front (front of the vehicle).

  As shown in FIG. 1, the vehicle individually adjusts a steering actuator 12 for turning a front wheel 11 as a steered wheel by steering a steering wheel 10 by a driver, and a braking force for the front wheel 11 and the rear wheel. A brake actuator 13 is provided. Such a brake actuator 13 is controlled by a control device 14 as a steering neutral point setting device.

  The controller 14 includes a steering angle sensor SE1 for detecting the steering angle of the steering 10, a wheel speed sensor SE2 for detecting the wheel speed of each wheel, and a yaw rate sensor for detecting the yaw rate generated in the vehicle. SE3 is electrically connected. Then, the control device 14 controls the brake actuator 13 based on detection signals from a plurality of sensors including the steering angle sensor SE1, each wheel speed sensor SE2, and the yaw rate sensor SE3.

  The steering angle sensor SE1 of the present embodiment outputs a detection signal based on the position of the steering 10 at the time when an operation switch for permitting driving of a power source such as an engine is turned on. Angle sensor ". The yaw rate sensor SE3 outputs a detection signal such that the yaw rate becomes a positive value when the vehicle turns left, and the yaw rate becomes a negative value when the vehicle turns right.

  The control device 14 has a digital computer constructed with a CPU, a ROM, a RAM, and the like. Various programs executed by the CPU, various threshold values, maps, and the like are stored in advance in the ROM. The RAM also stores information (such as vehicle speed) that can be appropriately rewritten when the operation switch is on.

  As an example of vehicle control using the steering angle of the steering wheel 10 as a parameter, the control device 14 of this embodiment is an ESC (Electronic Stability Control) that adjusts the braking force applied to each wheel in order to eliminate oversteer and understeer generated in the vehicle. I do. Such vehicle control cannot be executed when the neutral point is not set because the relative displacement amount based on the neutral point of the steering 10 is acquired and used as the steering angle. Therefore, in the control device 14, it is preferable to set the neutral point of the steering wheel 10 early after the operation switch is turned on and the vehicle starts to travel. The “neutral point of the steering wheel 10” refers to the rotational position of the steering wheel 10 at which the yaw moment generated in the traveling vehicle (that is, the yaw rate detected using the yaw rate sensor SE3) is substantially “0 (zero)”. I mean.

Next, a processing routine executed by the control device 14 for setting the neutral point of the steering 10 will be described with reference to a flowchart shown in FIG.
This processing routine is a processing routine that is executed at predetermined intervals set in advance while the above-described operation switch is in the ON state. In such a processing routine, the control device 14 acquires the yaw rate Yr based on the detection signal output from the yaw rate sensor SE3 (step S10). Subsequently, the control device 14 acquires the steering angle Str of the steering 10 based on the detection signal output from the steering angle sensor SE1 (step S11). In step S11, when the neutral point StrC of the steering wheel 10 is not set, a relative angle based on the position of the steering wheel 10 when the operation switch is turned on is acquired as the steering angle. On the other hand, when the neutral point StrC is set, a relative angle based on the neutral point StrC is acquired as the steering angle.

  And the control apparatus 14 acquires the vehicle body speed VS of the vehicle based on the detection signal output from at least 1 wheel speed sensor SE2 among each wheel speed sensor SE2 provided for every wheel (step S12). Subsequently, the control device 14 calculates the change amount ΔYr per unit time of the yaw rate Yr acquired in step S10 as the change amount of the lateral force applied to the vehicle (step S13). For example, in step S13, the yaw rate Yr acquired in step S10 is time-differentiated, and the calculation result is used as the yaw rate change amount ΔYr. Subsequently, the control device 14 determines whether or not the absolute value of the yaw rate change amount ΔYr calculated in step S13 is less than a preset change amount reference value ΔYrth (step S14).

  Here, when the steering angle Str of the steering wheel 10 and the vehicle body speed VS are constant, that is, when the yaw moment required by the driver (hereinafter also referred to as “requested yaw moment”) hardly changes, it occurs in the vehicle. The actual yaw moment is almost constant. In addition, when the required yaw moment changes little by little as in the case where the steering angle Str and the vehicle body speed VS change slowly, the actual yaw moment generated in the vehicle changes slowly according to the change in the required yaw moment.

  On the other hand, when at least one of the steering angle Str and the vehicle body speed VS changes abruptly, the requested yaw moment changes abruptly, and the actual yaw moment generated in the vehicle changes with a delay from the change in the requested yaw moment. To do. Therefore, when the requested yaw moment changes rapidly, there is a possibility that a divergence has occurred between the requested yaw moment and the actual yaw moment.

  Therefore, when the absolute value of the change amount ΔYr of the yaw rate is equal to or larger than the change amount reference value ΔYrth (step S14: NO), there is a possibility that there is a divergence between the requested yaw moment and the actual yaw moment. The apparatus 14 once ends this processing routine without performing an update process described later. On the other hand, when the absolute value of the change amount ΔYr of the yaw rate is less than the change amount reference value ΔYrth (step S14: YES), it is determined that the requested yaw moment and the actual yaw moment substantially match, and the control device 14 Then, the yaw rate Yr and the vehicle body speed VS acquired in steps S10 and S12 are substituted into the following relational expression (formula 1) to calculate a yaw rate converted steering angle StrYr as a steering angle estimated value (step S15). That is, in step S15, the yaw rate converted steering angle StrYr is acquired as a vehicle state value that is a value corresponding to the yaw moment generated in the vehicle. In the relational expression (Expression 1), “L” is the wheelbase length, “N” is the steering gear ratio, and “A” is the stability factor.

Subsequently, the control device 14 determines whether or not the absolute value of the yaw rate conversion steering angle StrYr calculated in step S15 is less than the straight-ahead determination value Strth at that time (step S16). This straight-ahead determination value Strth is a criterion for determining whether or not the vehicle is traveling straight. The straight traveling determination value Strth is an initial value Th_b (see FIG. 3C) when the update process has not been performed once since the operation switch is turned on. In the present embodiment, the initial value Th_b is set to a relatively large value so that the neutral point of the steering wheel 10 can be set early after the vehicle starts to travel.

  If the absolute value of the yaw rate converted steering angle StrYr is equal to or greater than the straight travel determination value Strth (step S16: NO), the control device 14 once ends this processing routine because it can be determined that the vehicle is not traveling straight. On the other hand, when the absolute value of the yaw rate converted steering angle StrYr is less than the straight traveling determination value Strth (step S16: YES), it can be determined that the vehicle is traveling straight, so that the control device 14 determines from the steering angle sensor SE1 at that time. A neutral point StrC of the steering 10 is set based on the output detection signal, and an update process for changing the straight traveling determination value Strth based on the yaw rate converted steering angle StrYr at the time when the neutral point StrC is set is performed.

  Specifically, the control device 14 sets the neutral point StrC of the steering 10 as the latest steering angle Str acquired in step S11 (step S17), and sets the straight travel determination value Strth as the latest yaw rate converted steering angle StrYr calculated in step S15. (Step S18). Then, the control device 14 stores the neutral point StrC and the straight traveling determination value Strth set in steps S17 and S18 in a predetermined storage area of the RAM. That is, each time an update process is performed, the stored contents of the predetermined storage area of the RAM are updated. Therefore, in this embodiment, an update step is comprised by step S17, S18. Thereafter, the control device 14 once ends this processing routine.

  Next, a method for setting the neutral point StrC of the steering 10 in the vehicle according to the present embodiment will be described with reference to timing charts shown in FIGS. 3 (a), 3 (b), and 3 (c). Note that it is assumed that the steering 10 is largely steered to the right when the operation switch is turned on.

  When the driving switch is turned on and the vehicle starts to travel, the traveling direction of the vehicle abruptly changes due to the sudden steering of the steering wheel 10 to the left side by the driver. Then, at the first timing t1, since the absolute value of the change amount ΔYr of the yaw rate exceeds the change amount reference value ΔYrth, the execution of the update process is prohibited (see FIGS. 3A and 3B). Even when the driver slowly steers the steering wheel 10, the absolute value of the yaw rate change amount ΔYr may exceed the change amount reference value ΔYrth if the driver depresses the accelerator pedal very quickly. obtain.

  Then, after the first timing t1, the steering speed of the steering wheel 10 by the driver (that is, the rotational speed of the steering wheel 10) decreases, and the yaw rate change amount ΔYr gradually approaches “0 (zero)”. Then, as shown in FIG. 3A, the actual steering angle of the steering wheel 10 (hereinafter also referred to as “actual steering angle Str_R”), the yaw rate converted steering angle StrYr calculated based on the yaw rate Yr and the vehicle body speed VS. The difference with is gradually reduced. Then, at the subsequent second timing t2, since the absolute value of the change amount ΔYr of the yaw rate is less than the change amount reference value ΔYrth, execution of the update process is permitted (see FIG. 3B).

  In addition, at the second timing t2, the absolute value of the yaw rate converted steering angle StrYr is less than the straight-running determination value Strth (that is, the initial value Th_b) at that time, so an update process is performed (FIG. 3C). reference). Then, the neutral point StrC of the steering wheel 10 becomes the steering angle Str that is a sensor value at the second timing t2, and the change amount reference value ΔYrth is changed to the yaw rate converted steering angle StrYr at the second timing t2. The When the neutral point StrC is set in this way, the steering angle Str of the steering 10 is corrected to a relative angle based on the neutral point StrC set at the second timing t2. As a result, the angle difference between the steering angle Str and the actual steering angle Str_R and the angle difference between the steering angle Str and the yaw rate converted steering angle StrYr are smaller than before the neutral point StrC is set. Furthermore, by setting the neutral point StrC, execution of vehicle control using the steering angle Str as a parameter as in the case of ESC is permitted.

  When the subsequent third timing t3 elapses, the steering wheel 10 is steered rapidly by the driver so that the vehicle turns to the right. Then, the absolute value of the yaw rate change amount ΔYr exceeds the change amount reference value ΔYrth due to a sudden change in the traveling direction of the vehicle, and the execution of the update process is prohibited.

  Then, at the fourth timing t4 when the steering angle Str of the steering wheel 10 becomes substantially constant, the absolute value of the yaw rate change amount ΔYr is less than the change amount reference value ΔYrth, and therefore execution of the update process is permitted. . However, at the fourth timing t4, since the yaw rate converted steering angle StrYr is equal to or greater than the straight-ahead determination value Strth at that time, the update process is not performed.

  Thereafter, the steering 10 begins to be steered by the driver so that the steering angle Str approaches “0 (zero)”, and at the fifth timing t5, the absolute value of the yaw rate converted steering angle StrYr is less than the straight-running determination value Strth at that time. In this position, the steering angle Str of the steering 10 is constant. At the fifth timing t5, since the absolute value of the yaw rate change amount ΔYr is less than the change amount reference value ΔYrth, the update process is performed. Then, the neutral point StrC of the steering wheel 10 becomes the steering angle Str at the fifth timing t5, and the variation reference value ΔYrth is changed to the yaw rate converted steering angle StrYr at the fifth timing t5.

  As a result, the neutral point StrC becomes closer to the actual neutral point than before the fifth timing t5. Then, after the fifth timing t5, the steering angle Str of the steering wheel 10 is corrected to a relative angle based on the neutral point StrC newly set at the fifth timing t5. Therefore, the angle difference between the steering angle Str and the actual steering angle Str_R and the angle difference between the steering angle Str and the yaw rate converted steering angle StrYr are smaller than before the fifth timing t5.

  Further, by performing the update process again, the straight traveling determination value Strth becomes a value closer to “0 (zero)” than before the fifth timing t5. That is, the criterion for determining whether or not the vehicle is in a straight traveling state becomes strict.

  Thereafter, at the sixth timing t6, the steering 10 is suddenly steered again by the driver so that the vehicle turns to the right. Then, since the absolute value of the change amount ΔYr of the yaw rate exceeds the change amount reference value ΔYrth, the execution of the update process is prohibited. When the seventh timing t7 has elapsed, the steering angle Str of the steering wheel 10 becomes substantially constant. Therefore, the absolute value of the yaw rate change amount ΔYr becomes less than the change amount reference value ΔYrth, and the execution of the update process is permitted. However, at the seventh timing t7, since the yaw rate converted steering angle StrYr is equal to or greater than the straight-ahead determination value Strth at that time, the update process is not performed.

  When the eighth timing t8 thereafter elapses, the steering 10 is slowly steered by the driver so that the steering angle Str approaches “0 (zero)”. In this case, since the absolute value of the change amount ΔYr of the yaw rate is maintained below the change amount reference value ΔYrth, execution of the update process is permitted even when the steering angle Str of the steering 10 is changing.

  When the ninth timing t9 elapses, the yaw rate converted steering angle StrYr becomes less than the straight traveling determination value Strth at that time, and the update process is performed. Then, the neutral point StrC of the steering wheel 10 becomes the steering angle Str at the ninth timing t9, and the variation reference value ΔYrth is changed to the yaw rate converted steering angle StrYr at the ninth timing t9.

  As a result, the neutral point StrC of the steering wheel 10 is set to a value closer to the actual neutral point as compared with the neutral point before the ninth timing t9, and the straight traveling determination value Strth is set to the ninth timing t9. The value is changed to a value closer to “0 (zero)” than before. As a result, the angle difference between the steering angle Str and the actual steering angle Str_R and the angle difference between the steering angle Str and the yaw rate converted steering angle StrYr are further reduced.

As described above, in the present embodiment, the following effects can be obtained.
(1) In order to set the neutral point StrC of the steering wheel 10 with high accuracy, it is preferable to set the straight traveling determination value Strth to a relatively small value. However, if the initial value Th_b of the straight traveling determination value is set to a relatively small value, the period from when the vehicle starts to run until the neutral point StrC is provisionally set becomes long. In this case, the period during which the neutral point StrC is not set becomes long, and there is a possibility that the period during which vehicle control using the steering angle Str of the steering wheel 10 as a parameter is prohibited, such as ESC, may be lengthened.

  In this regard, in the present embodiment, each time the update process is performed, the straight traveling determination value Strth is changed so that the absolute value thereof becomes smaller. Therefore, the initial value Th_b of the straight traveling determination value can be set to a relatively large value. As a result, the neutral point StrC of the steering wheel 10 can be tentatively set early after the driving switch is turned on and the vehicle starts to travel. Therefore, compared with the case where the initial value Th_b is set to a relatively small value, the period during which vehicle control execution using the steering angle Str of the steering 10 as a parameter, such as ESC, is prohibited can be shortened.

  (2) The setting accuracy of the neutral point StrC of the steering wheel 10 tentatively set first is not so high because the initial value Th_b is a relatively large value. However, in this embodiment, each time the update process is performed, the straight-ahead determination value Strth approaches “0 (zero)”. In this way, by setting a stricter criterion for determining whether or not the vehicle is traveling straight each time the update process is performed, the setting accuracy of the neutral point StrC can be improved each time the update process is performed. Therefore, vehicle control using the steering angle Str of the steering 10 as a parameter, such as ESC, can be performed with high accuracy.

  (3) When the lateral force applied to the vehicle changes greatly, the yaw moment generated in the vehicle changes with a delay relative to the steering of the steering wheel 10 by the driver. Therefore, in the present embodiment, when the absolute value of the change amount ΔYr of the yaw rate is equal to or greater than the change amount reference value ΔYrth, it is determined that the lateral force applied to the vehicle changes greatly, and the execution of the update process is prohibited. That is, the update process is performed only when the lateral force applied to the vehicle does not change significantly or when the lateral force is constant. Therefore, the setting accuracy of the neutral point StrC of the steering wheel 10 by the update process can be improved as compared with the case where the update process is performed even when the lateral force applied to the vehicle changes greatly.

  (4) As a parameter corresponding to the amount of change in lateral force applied to the vehicle, for example, the steering speed of the steering wheel 10 when the steering wheel 10 is steered can be considered. In this case, for example, if the vehicle is skidding such as understeer or oversteer, it is difficult to say that the steering speed of the steering 10 indicates the amount of change in the lateral force applied to the vehicle. In this regard, in this embodiment, the change amount ΔYr of the yaw rate is used as a parameter corresponding to the change amount of the lateral force applied to the vehicle. The change amount ΔYr of the yaw rate indicates the change amount of the lateral force applied to the vehicle even when the vehicle is skidding such as understeer or oversteer. Therefore, it is possible to improve the accuracy of determining whether or not the lateral force applied to the vehicle has changed greatly.

  (5) As a method of determining whether or not the vehicle is traveling straight, a method of determining whether or not the yaw rate Yr generated in the vehicle is less than a determination value is conceivable. However, in this method, even if the steering angle Str of the steering 10 is constant, the yaw rate Yr generated in the vehicle varies depending on the vehicle body speed VS. Therefore, there is a possibility that the setting accuracy of the neutral point StrC of the steering 10 may vary under the situation where the vehicle body speed VS of the vehicle changes.

  In this regard, in this embodiment, the yaw rate conversion steering angle StrYr calculated based on the yaw rate Yr generated in the vehicle and the vehicle body speed VS is used as the steering angle estimation value, and it is determined whether or not the vehicle is traveling straight. Determined. Therefore, even if the steering angle Str of the steering wheel 10 is constant, when the vehicle body speed VS changes, the estimated steering angle changes according to the change in the vehicle body speed VS. Variations in the setting accuracy of the 10 neutral points StrC can be suppressed.

The embodiment may be changed to another embodiment as described below.
The yaw rate used for calculating the yaw rate converted steering angle StrYr may be a calculated value calculated (estimated) using the lateral acceleration of the vehicle, instead of a value based on the detection signal from the yaw rate sensor SE3. The lateral acceleration is a value detected based on a detection signal from the lateral acceleration sensor.

  The vehicle state value may be an arbitrary value other than the yaw rate converted steering angle StrYr as long as it is a value corresponding to the yaw moment generated in the vehicle. For example, the yaw rate Yr may be used as the vehicle state value. Even if such a control configuration is employed, the same effects as in the above (1) and (2) can be obtained.

  When the yaw rate Yr is used as the vehicle state value, it is determined that the vehicle is in the straight traveling state when the state in which the yaw rate Yr is less than the straight traveling determination value continues for a predetermined time or more. Also good.

  When the yaw rate Yr is used as the vehicle state value, the yaw rate Yr is less than the straight-running determination value only when the longitudinal acceleration of the vehicle is within a preset acceleration range (a range including 0 (zero)). You may make it determine whether it exists. In this case, when the yaw rate Yr is less than the straight traveling determination value and the absolute value of the acceleration of the vehicle is small, it is determined that the vehicle is in the straight traveling state.

  As the amount of change in the lateral force applied to the vehicle, the amount of change in the steering angle Str of the steering 10 (that is, the steering speed of the steering) may be used, or the amount of change in the lateral acceleration of the vehicle may be used.

-You may abbreviate | omit the determination process of step S14 from the processing routine shown in FIG. Even if such a control configuration is employed, the same effects as in the above (1) and (2) can be obtained.
In the update process, the average value of the steering angle Str of the steering wheel 10 at the execution timing of the current update process and the neutral point StrC of the steering wheel 10 set by the previous update process may be used as the neutral point StrC of the steering wheel 10. . Further, when the current neutral point set in the current update process is “StrC (n)” and the previous neutral point set in the previous update process is “StrC (n−1)”, The neutral point StrC (n) may be set using the relational expression (formula 2) shown below. However, “α” is a coefficient larger than “0 (zero)” and smaller than “1” (for example, “0.2” or “0.7”).

  Similarly, in the update process, an average value of the yaw rate conversion steering angle StrYr at the execution timing of the current update process and the straight travel determination value changed in the previous update process may be used as the straight travel determination value Strth. In addition, when the current straight travel determination value updated in the current update process is “Strth (n)” and the previous straight travel determination value updated in the previous update process is “Str (n−1)”, The current straight traveling determination value Strth (n) may be set using the following relational expression (Expression 3). However, “β” is a coefficient larger than “0 (zero)” and smaller than “1” (for example, “0.2” or “0.7”).

The steering angle sensor may be a so-called absolute angle sensor that outputs a detection signal based on a preset neutral point. Even in this case, an error may occur between the preset neutral point of the absolute angle sensor and the actual neutral point of the steering due to the sensor mounting error. Therefore, it is preferable that the neutral point StrC is corrected by executing the processing routine shown in FIG. 2 even in a control device to which a detection signal from the absolute angle sensor is input.

  In the control device to which the detection signal is input from the absolute angle sensor, the neutral point StrC of the steering wheel 10 set by the update process may be stored in a nonvolatile memory such as an EEPROM.

  The processing routine shown in FIG. 2 may be repeatedly executed until the operation switch is turned off, or may be executed a predetermined number of times. However, the predetermined number is an arbitrary number of “2” or more (for example, five times).

Next, the technical idea that can be grasped from the above embodiment and another embodiment will be added below.
(A) As a change amount of the lateral force applied to the vehicle, a change amount (ΔYr) of the yaw rate based on the detection signal output from the yaw rate sensor (SE3) is acquired (S13),
A steering neutral point setting device that prohibits execution of the update processing (S17, S18) when the yaw rate change amount (ΔYr) is equal to or greater than the change amount reference value (ΔYrth) (S14: NO).

  DESCRIPTION OF SYMBOLS 10 ... Steering, 14 ... Control apparatus as neutral point setting device, SE1 ... Steering angle sensor, StrC ... Neutral point, Strth ... Straight-run determination value, StrYr ... Yaw rate converted steering angle (steering angle estimated value) as vehicle state value, Yr: yaw rate, VS: body speed, ΔYr: change amount of yaw rate, ΔYrth: change amount reference value.

Claims (4)

A steering neutral point setting device for setting a neutral point (StrC) of a steering (10) of a vehicle,
The absolute value of the vehicle state value (StrYr, Yr), which is a value corresponding to the yaw moment generated in the vehicle, is less than the straight travel determination value (Strth) that is a criterion for determining whether or not the vehicle is in a straight travel state. In this case (S16: YES), the neutral point (StrC) of the steering (10) is set based on the detection signal output from the steering angle sensor (SE1) at that time, and the neutral point (StrC) is set. An update process (S17, S18) for changing the straight traveling determination value (Strth) based on the vehicle state values (StrYr, Yr) at the time point is performed,
Steering neutral point setting characterized in that the updating process (S17, S18) is performed each time the absolute value of the acquired vehicle state value (StrYr, Yr) becomes less than the straight traveling determination value (Strth) at that time. apparatus.   2. The steering process according to claim 1, wherein the update process (S <b> 17, S <b> 18) is prohibited when the change amount (ΔYr) of the lateral force applied to the vehicle is equal to or greater than the change reference value (ΔYrth) (S <b> 14: NO). Neutral point setting device. The vehicle state value is an estimated steering angle value of the steering (10) calculated based on a yaw rate (Yr) generated in the vehicle or estimated to be generated in the vehicle and a vehicle body speed (VS) of the vehicle. (StrYr),
The steering according to claim 1 or 2, wherein the update process (S17, S18) is performed when the estimated steering angle value (StrYr) is less than the straight-running determination value (Strth) at that time (S16: YES). Neutral point setting device. A steering neutral point setting method for setting a neutral point (StrC) of a steering (10) of a vehicle,
When the absolute value of the vehicle state value (StrYr), which is a value corresponding to the yaw moment generated in the vehicle, is less than the straight travel determination value (Strth) that is a criterion for determining whether or not the vehicle is in a straight travel state (S16: YES), the vehicle at the time of setting the neutral point (StrC) of the steering (10) and setting the neutral point (StrC) based on the detection signal output from the steering angle sensor (SE1) at that time An update step (S17, S18) for changing the straight travel determination value (Strth) based on the state value (StrYr);
A method for setting a neutral point of steering, wherein the updating step (S17, S18) is executed each time the absolute value of the acquired vehicle state value (StrYr) becomes less than a straight traveling determination value (Strth) at that time.