JP3649110B2 - Lane Keep Assist Control Device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention captures white line information during traveling and applies steering torque to the steering force transmission system to control the vehicle in the direction toward the center of the lane, or applies steering reaction force torque to the steering force transmission system. It belongs to the technical field of a lane keep assist control device that controls in a direction toward the lane center.
[0002]
[Prior art]
Lane Keeping Assistance System (Lane Keeping Assistance System), which controls the steering system of the vehicle so that it travels in the center of the lane on an expressway, etc., inputs a steering actuator attached to the steering column via a gear and white line information Actuator driving means for driving the steering actuator with the command current calculated by the lane keep assist control means for information is provided.
[0003]
As shown in FIG. 9, the lane keep assist control means calculates the target lateral position of the vehicle according to the road curvature detected or estimated using the white line information in order to control the vehicle in the direction toward the center of the lane. A target trajectory calculation unit that performs a proportional FB current by multiplying a vehicle lateral position, lateral velocity, yaw rate, yaw angle, yaw angle, steering angle, steering angular velocity, and the like detected or estimated using white line information by a proportional FB gain. In order to prevent steady offset from the target lateral position (or lane center) due to crosswind, cross slope, alignment deviation, etc. from the FB section, from the vehicle lateral displacement and target trajectory calculation section from the vehicle position detection section An integral FB section for calculating an integral FB current obtained by multiplying an integral value of a target deviation with a target lateral displacement by a predetermined integral FB gain, and a product in which an integral limit value of the integral FB current is set in advance. Limit value setting unit, addition unit for adding proportional FB current and integral FB current (integrated FB current = integration limit value if exceeding integral limit value), and limiting the output current to the commanded current limit value. And a command current limiter that obtains a command current to the steering actuator. The notation FB represents feedback.
[0004]
As shown in FIG. 10, the output current limit is performed using an actuator output current limit map in which the horizontal axis is the turning acceleration and the vertical axis is the current limit value, thereby enabling the driver to perform any steering intervention. ing. Hereinafter, the output current limitation will be described in detail.
[0005]
FIG. 11 shows the relationship between steering torque and vehicle turning acceleration during slalom traveling (repeating left and right steering in a relatively short time). The relationship between the steering angle and the steering torque (same during driver steering and automatic steering operation) changes as the vehicle speed changes. That is, if the vehicle speed increases even at the same steering angle, the turning acceleration increases, and as a result, the reaction torque on the steering wheel also increases. On the other hand, the relationship between the steering torque and the turning acceleration of the vehicle is almost constant regardless of the vehicle speed, so if the upper limit value of the assist steering torque is set for the turning acceleration, even if the vehicle speed changes, the lane keep The assist control does not always generate extra steering torque.
[0006]
Has hysteresis characteristics due to the effects of steering friction, etc. and non-linearity (characteristic of broken line between low turning acceleration range and high turning acceleration range) due to power steering characteristics, but assists in lane keeping driving From this point of view, steering is relatively slow compared to slalom driving, FIG. If the steering torque of the shaded portion is generated, generally good lane keeping performance can be obtained.
[0007]
Assuming that the torque applied to the steering wheel by the driver is Td and the assist steering torque by the lane keep assist control is Tassist, the torque Ts for performing the steering operation for generating an arbitrary turning acceleration is as follows.
[0008]
Ts = Td + Tassist
Thereby, as shown in FIG. 12, when the current limit value is a constant value, the following can be said.
(A) When the driver and the lane keep control are traveling in a coordinated manner (when the vehicle is steered in the same direction as the turning direction of the vehicle), the directions of Td and Tassist coincide, and | Ts |> | Td | Therefore, the burden on the driver can be reduced as compared with the case without lane keeping control. Ts is a steering wheel return torque at the time of steering, and the driver may apply torque Ts-Td obtained by subtracting the assist torque from the steering wheel return torque to the steering wheel.
(B) When the driver steers in the opposite direction to the lane keeping control for emergency avoidance (when steered in the direction opposite to the turning direction of the vehicle), the directions of Td and Tassist are reversed, and | Ts | < Since | Td |, the burden on the driver increases compared to the case without lane keeping control.
Therefore, as indicated by the arrow in FIG. 12, the steering wheel operation may not be possible unless a very large steering torque is applied compared to the normal time (without lane keeping control). In particular, if the driver tries to further increase the steering wheel, the lane keep control will generate torque in the direction of returning the steering wheel. Therefore, in order for the driver to move the steering wheel, the steering wheel return torque and the control torque were added. You have to steer with torque.
[0009]
In this system, as shown in FIG. 10, by setting a current limit map corresponding to the turning acceleration of the vehicle, the control torque in the direction opposite to the driver's intention is reduced as shown in FIG. The driver's intervention torque (arrow in FIG. 13) required when the driver steers in the direction opposite to the keep control (when steered in the direction opposite to the turning direction of the vehicle) can be suppressed as much as possible in the case of FIG. Thus, any steering intervention by the driver can be facilitated without providing a special torque sensor.
The turning acceleration used here may be a value directly detected by an acceleration sensor, or may be a value estimated using a vehicle speed, a steering angle, or the like. A similar result can be obtained by using the yaw rate instead of the turning acceleration.
[0010]
[Problems to be solved by the invention]
However, in the above-described conventional lane keep assist control device, the actuator current is limited so as to facilitate any steering intervention by the driver during the lane keep control. However, the command current is easily saturated so that the command current becomes equal to the command current limit value. When the command current is saturated and reaches the current limit value, the deviation between the target lateral position and the lateral position of the vehicle does not decrease, so there is a problem that the vehicle gradually deviates from the lane or is offset.
[0011]
In other words, if the command current is saturated, the compensation current for disturbances (crosswind, road surface gradient, curve, driver steering intervention, etc.) will exceed the current limit value and cannot be output to the steering actuator. Deviation from or offset driving.
[0012]
In such a case, the integrated value of the deviation between the target position and the vehicle position increases to a preset integration limit value, and then the lane is changed by a crosswind direction change, a road surface slope change, a curve direction change, or a driver steering intervention. Even when the vehicle changes to a traveling state along the center or the target track, the accumulated integrated value does not decrease rapidly, and an excess steering torque is generated, so that the vehicle is likely to meander.
[0013]
Also, if the integral FB gain is set small to avoid such meandering, or if the integral limit value set in advance is set small, the necessary steering torque cannot be generated. Traveling remains.
[0014]
The saturation of the command current will be described in detail. Here, the sum of the proportional FB current and the integral FB current is set in advance or exceeds the command current limit value calculated according to the turning acceleration or the like. When the command current value (a limiter is provided so as not to exceed the command current value) is equal to the command current limit value, the command current is called a saturated state. In this state, even if the proportional FB current or the integrated FB current changes, the command current stays at a constant value (command current limit value) as long as the sum does not fall below the limit value. As the deviation continues to occur, the integrated value of the deviation continues to increase.
[0015]
The cause of the saturation state of the command current is that a large change speed is required by giving a step-like input to the control target value, or the influence of road surface gradient, wind, and driver intervention is large, and this causes disturbance. This is because a large control current is calculated to cancel the torque component.
[0016]
Since the current is limited by the judgment that it is not necessary for the original lane keeping driving, if the command current is saturated, the steering torque necessary to cancel the disturbance cannot be output, and the vehicle moves in a direction to reduce the target deviation. Gradually deviate from the lane or run offset.
[0017]
Steering torque disturbance (wind, road surface gradient, due to driver intervention) is Td, assist steering torque by lane keep assist control is Tassist, and steering operation torque to generate arbitrary turning acceleration is Ts.
Ts = Td + Tassist
⇔Tassist = Ts-Td
It is. When the assist steering direction and the driver intervention steering direction are opposite, the signs of Ts and Td are reversed.
| Tassist | = | Ts−Td |> | Ts |
Therefore, if the torque limit value Tlmt is set to a value close to Ts in order to improve driver intervention,
| Tassist | >> | Tlmt | >> | Ts |
(Tlmt: limit torque = limit current value × torque constant)
Is likely to occur.
[0018]
Conversely, if Tlmt >> Ts (Tlmt is sufficiently larger than Ts),
| Tlmt | >> | Tassist | >> | Ts |
As a result, the command current hardly saturates, but the driver's steering intervention becomes difficult.
[0019]
The present invention has been made paying attention to the above-mentioned problems, and its object is to stabilize the vehicle behavior after recovery of command current saturation by suppressing the generation of excessive steering torque due to accumulation of integral values. Another object of the present invention is to provide a lane keep assist control device capable of improving straightness.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, in the invention according to claim 1, target trajectory calculating means for calculating the target lateral position of the vehicle according to the road curvature detected or estimated using the white line information;
Proportional to calculate the proportional feedback current by multiplying the vector with the factor of the lateral position, lateral velocity, yaw rate, yaw angle, steering angle, steering angular velocity, etc. of the vehicle detected or estimated using white line information and proportional feedback gain A feedback section;
An integral feedback unit that calculates an integral feedback current obtained by multiplying the integral value of the target deviation between the detected vehicle lateral displacement and the target lateral displacement from the target trajectory calculating means by a predetermined integral feedback gain;
Current adding means for adding the proportional feedback current and the integral feedback current;
Allows any steering intervention of the driver Command current limit value set in advance, or Allows any steering intervention of the driver Command current limiting means for obtaining a command current to the steering actuator by limiting the output current of the current addition value by the command current limit value calculated according to the turning acceleration or the like;
In the lane keep assist control device with
When the command current from the command current limiting means is in a saturated state where the command current is equal to the command current limit value, the integral feedback unit only performs an integration operation in the direction of decreasing the command current and increases the command current. An integral calculation stop judging means for holding the integral value at that time without performing the calculation is provided.
[0021]
In the invention of claim 2, target trajectory calculating means for calculating a target lateral position of the vehicle according to the road curvature detected or estimated using the white line information;
Proportional to calculate the proportional feedback current by multiplying the vector with the factor of the lateral position, lateral velocity, yaw rate, yaw angle, steering angle, steering angular velocity, etc. of the vehicle detected or estimated using white line information and proportional feedback gain A feedback section;
An integral feedback unit that calculates an integral feedback current obtained by multiplying the integral value of the target deviation between the detected vehicle lateral displacement and the target lateral displacement from the target trajectory calculating means by a predetermined integral feedback gain;
Current adding means for adding the proportional feedback current and the integral feedback current;
Allows any steering intervention of the driver Command current limit value set in advance, or Allows any steering intervention of the driver Command current limiting means for obtaining a command current to the steering actuator by limiting the output current of the current addition value by the command current limit value calculated according to the turning acceleration or the like;
In the lane keep assist control device with
When it is determined that the command current from the command current limiting means is in a saturated state in which the command current limit value is equal to the command current limit value, and the command current limit value decreases with time, the difference between the command current and the proportional feedback current An integral limit value calculating means for calculating a corresponding integral limit value and resetting the integral value of the integral feedback unit is provided.
[0022]
In the invention of claim 3, target trajectory calculating means for calculating the target lateral position of the vehicle according to the road curvature detected or estimated using the white line information;
Proportional to calculate the proportional feedback current by multiplying the vector with the factor of the lateral position, lateral velocity, yaw rate, yaw angle, steering angle, steering angular velocity, etc. of the vehicle detected or estimated using white line information and proportional feedback gain A feedback section;
An integral feedback unit that calculates an integral feedback current obtained by multiplying the integral value of the target deviation between the detected vehicle lateral displacement and the target lateral displacement from the target trajectory calculating means by a predetermined integral feedback gain;
Current adding means for adding the proportional feedback current and the integral feedback current;
Allows any steering intervention of the driver Command current limit value set in advance, or Allows any steering intervention of the driver Command current limiting means for obtaining a command current to the steering actuator by limiting the output current of the current addition value by the command current limit value calculated according to the turning acceleration or the like;
In the lane keep assist control device with
The integral feedback unit only performs an integration operation in the direction of decreasing the command current, does not perform an integration operation that increases the command current, and retains the integral value at that time, a command current and An integral limit value calculating means for calculating an integral limit value according to the difference from the proportional feedback current and resetting the integral value of the integral feedback unit is provided together.
When the command current from the command current limiter is in a saturated state where the command current limit value is equal to the command current limit value, the relationship between the vehicle lateral position detected or estimated by the white line information and the road curvature is the relationship in which the vehicle moves away from the center of the lane. Integral value suppression switching means is provided for switching the processing for suppressing accumulation of integral values, such as selecting the retention of the integral value when the vehicle is moving, and selecting the reset of the integral value when the vehicle is moving toward the center of the lane. It is characterized by that.
[0023]
Operation and effect of the invention
In the first aspect, the target trajectory calculating means calculates the target lateral position of the vehicle according to the road curvature detected or estimated using the white line information. Then, in the proportional feedback unit, a vector having the elements of the lateral position, the lateral speed, the yaw rate, the yaw angle with respect to the lane, the steering angle, the steering angular speed, etc. detected or estimated using the white line information is multiplied by the proportional feedback gain. The proportional feedback current is calculated, and the integral feedback unit calculates the integral feedback current obtained by multiplying the integral value of the target deviation between the detected vehicle lateral displacement and the target lateral displacement from the target trajectory calculation means by a predetermined integral feedback gain. In the current adding means, the proportional feedback current and the integral feedback current are added, and in the command current limiting means, Allows any steering intervention of the driver Command current limit value set in advance, or Allows any steering intervention of the driver A command current to the steering actuator can be obtained by limiting the output current of the current addition value with the command current limit value calculated according to the turning acceleration or the like.
On the other hand, when the command current from the command current limiting unit is in a saturated state where the command current limit value is equal to the command current limit value, the integral calculation stop determination unit performs only the integral calculation in the direction of decreasing the command current in the integral feedback unit. The integral value at that time is held without performing an integral operation that increases the command current.
That is, when the integral calculation stop determination means is not performed, if a lateral displacement occurs in the vehicle, the integral feedback current in the unsaturated state where the command current does not reach the command current limit value continues to increase to a preset integral limit value. As a result, the command current to the steering actuator also continues to increase. After that, even if the command current saturates, the integration calculation is performed in the direction to increase to the preset integration limit value, so even if the lateral displacement of the vehicle starts to decrease and the proportional feedback current decreases, it will continue for a while. The saturated state of the command current is maintained.
For this reason, in a system where the maximum steering torque due to the output current limit and the steering torque of the driver are almost the same value, once the command current is saturated, the excessive lateral displacement integral value accumulates, and the lane center or target trajectory is accumulated. Even after returning to the traveling state along the road, an excessive steering torque is generated for a while, so that the vehicle is likely to meander. Further, in order to prevent such meandering, when the integral feedback gain or the preset integral limit value is set to be small, the integral feedback current itself becomes small, and there is a possibility that offset running may remain.
On the other hand, in the invention according to claim 1, while being saturated at the limit value, the integration calculation is performed only in the direction of decreasing the command current, and the integration is performed without performing the integration calculation in the direction of increasing the command current. By maintaining the value, an extra increase in the integral feedback current can be suppressed, so that if the lateral feedback of the vehicle starts to decrease and the proportional feedback current decreases, the command current to the steering actuator is quickly reduced. be able to.
Therefore, by adopting the integral calculation stop judging means, it is possible to stabilize the vehicle behavior after the recovery of the command current saturation and improve the straight running performance by suppressing the generation of excessive steering torque due to the accumulation of the integral value.
[0024]
The action of obtaining the command current to the steering actuator of the invention of claim 2 is the same as that of the invention of claim 1.
On the other hand, when it is determined that the command current from the command current limiting means is in a saturated state where the command current limit value is equal to the command current limit value, and the command current limit value decreases with time, the integral limit value calculation means An integral limit value corresponding to the difference between the value and the proportional feedback current is calculated, and the integral value of the integral feedback unit is reset by the integral limit value.
In other words, the integral limit value calculated according to the difference between the command current and the proportional feedback current is obtained so that the sum of the proportional feedback current and the integral feedback current matches the command current to the steering actuator after the current limit. Is the integrated value. Therefore, when the current limit value decreases with time while the command current is saturated (for example, when the current limit value decreases with an increase in turning acceleration due to the driver's steering by performing a current limit according to the turning acceleration). The integral value also decreases in proportion to the decrease in the current limit value, and immediately after the current limit value is restored, the saturation of the command current is canceled and the excessive integral value does not occur. It is effective for prevention.
Similarly, during the saturation of the command current, the vehicle's lateral position, lateral velocity, yaw rate, yaw angle relative to the lane, steering angle, steering angular velocity, etc., detected or estimated using the white line information, increase the proportional feedback current. If it increases, the integral value decreases in proportion to the increase of the proportional feedback current, and immediately after the proportional feedback current recovers, the saturation of the command current is canceled and no excessive integral value is generated, so the vehicle behavior is stable. And effective in preventing meandering.
[0025]
The operation for obtaining the command current to the steering actuator of the invention described in claim 3 is the same as that of the invention described in claim 1.
On the other hand, when the command current from the command current limiting means is in a saturated state where the command current limit value is equal to the command current limit value, in the integral value suppression switching means, the relative relationship between the vehicle lateral position detected or estimated by the white line information and the road curvature is When the vehicle moves away from the center of the lane, the integral value is selected to be retained by the integral calculation stop judgment means, and the relative relationship between the vehicle lateral position detected or estimated by the white line information and the road curvature is The process of suppressing the accumulation of the integral value is switched so that the integral value resetting means by the integral limit value calculating means is selected when the relationship is approaching.
That is, when the integral value is held, the integral feedback current tends to be excessive, and when the integral value is decreased, the integral feedback current tends to be insufficient.
Therefore, for example, when the vehicle is on the right side of the road while driving on the right curve, even if the vehicle goes straight, it gradually approaches the center of the lane. Is secured.
In addition, for example, when the vehicle is on the left side of the road while driving on the right curve, when the vehicle goes straight, the vehicle gradually moves away from the center of the lane. Is secured.
In this way, depending on the relative relationship between the vehicle lateral position and the road curvature (turning radius), the integration value is selected when the vehicle moves away from the center of the lane, and the integration is performed when the vehicle approaches the center of the lane. By selecting the value reset, the integral feedback current after the saturation of the command current is eliminated can be set to an appropriate value, so that stable vehicle behavior and lane followability can always be compatible.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
First, the configuration will be described.
[0027]
FIG. 1 is an overall system diagram showing an automobile steering system to which a lane keep assist control device according to Embodiment 1 is applied. A column shaft 2 is inserted and supported in the steering column 1, and an upper end portion of the column shaft 2 is shown. Is provided with a steering wheel 3, and a hydraulic power steering mechanism 6 for turning the left and right wheels 4, 5 is connected to a lower end portion of the column shaft 2, and an auxiliary steering torque is applied to a middle position of the column shaft 2. An assist actuator 7 (steering actuator) to be applied is provided.
[0028]
The assist actuator 7 includes a motor 8, an electromagnetic clutch 9 provided on the motor shaft, a driving gear 10 that is rotationally driven by the motor 8 via the electromagnetic clutch 9, and a driven gear 11 that meshes with the driving gear 10. It has a worm and wheel speed reduction mechanism.
[0029]
A steering angle sensor 13 for detecting the rotation angle of the column shaft 2 is provided at a position near the steering wheel 3 of the column shaft 2, and the gear shaft end portion on the opposite side of the drive gear 10 from the electromagnetic clutch 9 is provided. Is provided with an encoder 14 for detecting the rotation angle of the drive gear 10, and sensor signals from the steering angle sensor 13 and the encoder 14 are input to the lane keep control unit 15.
[0030]
In addition to the sensor signals from the steering angle sensor 13 and the encoder 14, the lane keep control unit 15 includes a CCD camera that captures a road ahead in the traveling direction and an image processing circuit 16 integrated with a camera & image processing device 16. The vehicle running state information and various vehicle system signals from a vehicle speed sensor, etc. are input, and the lane keep control unit 15 outputs a control current for driving the motor to the motor 8 and also a connection / disconnection command to the electromagnetic clutch 9. Is output.
[0031]
The camera & image processing device 16 performs image processing on a front road image based on a signal from a CCD camera, and a boundary line of a front lane such as a white line or a center line is extracted and identified, and a vehicle running position and a lane center position are detected. The own vehicle traveling state information including the lateral displacement is created.
[0032]
FIG. 2 is a block diagram showing a lane keep assist control system. The lane keep control unit 15 includes a steering angle detection unit 15a for detecting a steering angle based on a sensor signal from the steering angle sensor 13, a camera & image. A white line recognition unit 15b that recognizes a white line of a road that is running based on input information from the processing device 16, and a target lateral position y of the vehicle according to the road curvature detected or estimated using the white line information. _r A target trajectory calculating unit 15c (target trajectory calculating means) for calculating the vehicle lateral position y using the white line information, a vehicle position detecting unit 15d for detecting the vehicle lateral position y using the white line information, A proportional FB unit 15e (proportional feedback unit) that calculates a proportional feedback current Ip obtained by multiplying a vector x having factors such as a lateral velocity, a yaw rate, a yaw angle with respect to a lane, a steering angle, and a steering angular velocity by a proportional FB gain Kp is detected. Vehicle lateral displacement y and target lateral displacement y from the target trajectory calculation unit 15c _r Target deviation yy which is the difference between _r The target deviation calculating unit 15f for calculating the target deviation and the target deviation yy _r An integral FB unit 15g (integral feedback unit) that calculates an integral FB current Ii obtained by multiplying the integral value S by a predetermined integral FB gain Ki, and a current adder 15h (current) that adds the proportional FB current Ip and the integral FB current Ii And a command current limiter 15i that obtains a command current Iref to the assist actuator 7 by limiting the output current of the current addition value Is based on the command current limit values Ilmt + and Ilmt− calculated according to the turning acceleration. Command current limiting means) and the command current Iref from the command current limiter 15i are in a saturated state in which the command current limit values Ilmt + and Ilmt− are equal to each other, the integration FB unit 15g is directed to decrease the command current Iref. Integral calculation stop determination unit 15j (integration calculation stop) that performs only the integral calculation and does not perform an integral calculation that increases the command current Iref but retains the integral value S at that time. Stop determination means).
[0033]
Next, the operation will be described.
[0034]
[Actuator drive current calculation process]
FIG. 3 is a flowchart showing the flow of the actuator drive current calculation process performed by the lane keep control unit 15 of the first embodiment. Each step will be described below.
[0035]
In step 30, based on the acquisition of the steering angle data by the steering angle sensor 13 and the input information from the camera & image processing device 16, the vehicle running state such as the road curvature, the running position of the vehicle with respect to the white line, the yaw angle with respect to the white line, etc. Perform data acquisition.
[0036]
In step 31, the target lateral position y of the vehicle that is the target travel path using the road curvature data and the vehicle travel state data. _r Is calculated. For example, the target lateral position y _r If is fixed at 0, lane keep control is performed for the purpose of traveling in the center of the lane. Furthermore, the target lateral position y is set so that the behavior of the vehicle is smooth even when the connection of the white lines is discontinuous or when it is bent locally. _r Is interpolated.
[0037]
In step 32, a proportional FB current Ip (= −Kp · x) is always calculated in the direction toward the center of the lane, regardless of a straight line or a curve, using road curvature data, vehicle running state data, and steering angle data. Here, the proportional FB current Ip may be calculated by multiplying only the lateral displacement of the vehicle by the proportional FB gain Kp, and estimated values such as the lateral displacement, lateral velocity, yaw rate, yaw angle with respect to the lane, steering angular velocity, etc. It is also possible to calculate, as the proportional feedback current Ip, the sum of values obtained by multiplying the respective vectors x1, x2,..., Which are calculated and multiplied by the proportional FB gains Kp1, Kp2,.
[0038]
In step 33, when the command current Iref before one control cycle is in a saturated state in which the command current limit values Ilmt + and Ilmt− (FIG. 10) calculated according to the turning acceleration are equal, the command current Iref is further saturated. Make a decision not to integrate to. That is, only integration calculation in the direction in which the command current Iref is decreased (when the vehicle is to the left of the target track at the time of current saturation during left steering, or when the vehicle is to the right of the target track at the time of current saturation during right steering) Integral calculation is not performed in the direction in which the command current Iref is increased (when the vehicle is to the right of the target track when the current is saturated during left steering, or when the vehicle is to the left of the target track when the current is saturated during right steering) Hold the integration value at that time.
[0039]
In step 34, the target lateral displacement y calculated by the target trajectory calculation unit 15c. _r Vehicle lateral displacement y and target lateral displacement y _r Target deviation yy which is the difference between _r Is multiplied by an integral FB gain Ki to calculate an integral FB current Ii (= −Ki · S).
[0040]
In step 35, the proportional FB current Ip and the integral FB current Ii are added to obtain a current addition value Is.
[0041]
In step 36, it is determined whether or not the current addition value Is is less than the command current limit value Ilmt + (upper limit value). In step 37, it is determined whether or not the current addition value Is exceeds the command current limit value Ilmt− (lower limit value). If NO is determined in step 36, the process proceeds to step 38, where the command current limit value Ilmt + is set as the command current Iref, YES is determined in step 36, and NO is determined in step 37. If the command current limit value Ilmt− is set as the command current Iref, YES is determined in step 36 and YES is determined in step 37, the process proceeds to step 40, where the current addition value Is is determined as the command current Iref−. Iref. That is, the output current limiting process of the current addition value Is is performed based on the command current limit values Ilmt + and Ilmt− (FIGS. 10 and 13) calculated according to the turning acceleration.
[0042]
In step 41, the actual actuator current is fed back in accordance with the command current Iref set in step 38, step 39 or step 40, thereby obtaining the duty ratio to be input to the PWM (pulse modulation) drive circuit.
[0043]
[Actuator drive current calculation function]
First, when the command current Iref is not saturated, the flow proceeds to step 30 → step 31 → step 32 → step 33 → step 34 → step 35 → step 36 → step 37 → step 40 in the flowchart of FIG. In step 40, the current addition value Is obtained by adding the proportional FB current Ip and the integral FB current Ii is set as the command current Iref.
[0044]
On the other hand, when the command current Iref is in a saturated state in which the command current limit values Ilmt + and Ilmt− are equal to each other, the flow proceeds from step 30 to step 31 to step 32 to step 33 in the flowchart of FIG. In step S34, only when it is determined that the command current Iref is to be decreased, the process proceeds to step 34 to perform an integral operation. When it is determined that the command current Iref is to be increased, the process proceeds to step 35, and the integral operation is not performed. Is done.
That is, as shown in FIG. 4, when the current is saturated at the time of right steering, the integral calculation is not performed in the direction to further increase the steering torque to the right side, and when the current is saturated at the left steering, the steering torque is further increased to the left side. No integration is performed in the increasing direction.
[0045]
Then, the flow proceeds from step 35 to step 36 → step 38, or step 36 → step 37 → step 39. In step 38, the command current Iref is set to the command current limit value Ilmt +, and in step 39, the command current Iref is commanded. The output current is limited to the current limit value Ilmt−.
[0046]
[Integration stop judgment action at saturation]
As shown in FIG. 5A, based on a typical example in which the vehicle is displaced 0.5 m to the left due to the driver's steering or the like from time t0 to time t1, The integral stop determination operation will be described.
[0047]
First, when the integral stop determination is not performed, as shown in FIG. 5 (b-1), when the vehicle undergoes a lateral displacement, the command current Iref does not reach the command current limit values Ilmt + and Ilmt−. The integrated FB current Ii in the state continues to increase to a preset integration limit value, and as a result, the command current Iref to the steering actuator also continues to increase (area (1)). Thereafter, even if the command current Iref is saturated, the integration calculation is performed in the direction of increasing to the preset integration limit value (region (2)), so that the lateral displacement of the vehicle starts to decrease and the proportional FB current Ip is Even if it decreases, the saturation state of the command current Iref is maintained for a while (region (3)). The integral limit value represents the upper limit value of the integral value necessary for preventing the overflow of the variable in the CPU from the characteristic of the integral calculation. In FIG. 5, the integral limit value set in advance is not reached. Therefore, it is not illustrated.
[0048]
For this reason, in a system where the maximum steering torque due to the output current limit and the steering torque of the driver are almost the same value, once the command current is saturated, the excessive lateral displacement integral value accumulates, and the lane center or target trajectory is accumulated. Even after returning to the traveling state along the road, an excessive steering torque is generated for a while, so that the vehicle is likely to meander. Further, in order to prevent such meandering, when the integral FB gain or the preset integral limit value is set to be small, the integral FB current itself becomes small, and there is a possibility that the offset running may remain.
[0049]
On the other hand, when the integral stop determination is performed as in the first embodiment, as shown in FIG. 5B-2, the command current Iref is set to the command current limit values Ilmt +, Ilmt as shown in FIG. While being saturated at-, the integral operation is performed only in the direction of decreasing the command current Iref, and the integral FB current is maintained by maintaining the integral value S without performing the integration operation in the direction of increasing the command current Iref. Since an excessive increase in Ii can be suppressed (region {circle around (2)}), when the lateral FB current Ip starts to decrease and the proportional FB current Ip decreases, the command current Iref to the assist actuator 7 is quickly decreased. (Region (3)), and the command current Iref is released from the saturated state at an early stage.
[0050]
Next, the effect will be described.
[0051]
In the lane keep assist control device of the first embodiment, integration is performed when the command current Iref from the command current limiter 15i is in a saturated state equal to the command current limit values Ilmt + and Ilmt− as shown in FIG. Provided is an integration calculation stop determination unit 15j that performs integration calculation in the direction in which the command current Iref is decreased in the FB unit 15g, and does not perform integration calculation to increase the command current Iref, and holds the integration value S at that time. Therefore, by suppressing the generation of excessive steering torque due to accumulation of integral values, the vehicle behavior after recovery of command current saturation can be stabilized, and straight running performance can be improved.
[0052]
(Embodiment 2)
First, the configuration will be described. FIG. 6 is a block diagram showing a control system of the lane keep assist control apparatus according to the second embodiment. The lane keep control unit 15 includes the integration calculation stop determination unit 15j according to the first embodiment. Instead, an integral limit value calculating unit 15k (integral limit value calculating means) is provided. Other configurations are the same as those of the first embodiment shown in FIG.
[0053]
The integral limit value calculating unit 15k determines that the command current Iref from the command current limiting unit 15i is in a saturated state where the command current limit values Ilmt + and Ilmt− are equal to those shown in FIG. When the current limit values Ilmt + and Ilmt− decrease (for example, when the command current limit values Ilmt + and Ilmt− decrease as the turning acceleration increases due to the driver's steering by performing the current limit as shown in FIG. 10). ,
Sr = | (Iref−Ip) / Ki |
(Ip: proportional FB current, Ki: integral FB gain)
The integration limit value Sr is calculated, and the integration value S is reset with the obtained integration limit value Sr.
[0054]
Next, the operation will be described.
[0055]
[Actuator drive current calculation process]
FIG. 7 is a flowchart showing the flow of the actuator drive current calculation process performed by the lane keep control unit 15 of the second embodiment. Each step will be described below. Steps 70, 71, 72, 74, 75, 76, 77, 78, 79, 80, 81 are the same as steps 30, 31, 32, 34, 35, 36, 37, 38, 39, 40, FIG. The description is omitted because it is the same as 41.
[0056]
In step 82, when the command current Iref is in a saturated state limited by the command current limit value Ilmt + shown in FIG. 10 in step 78, an integral limit value Sr (≧ 0) is calculated by the above equation, and the obtained integral is obtained. An integral reset process for resetting the integral value S with the limit value Sr is performed.
[0057]
In step 83, when the command current Iref is in a saturated state limited by the command current limit value Ilmt− shown in FIG. 10 in step 79, the integral limit value Sr (≦ 0) is calculated by the above formula and obtained. An integral reset process for resetting the integral value S with the integral limit value Sr is performed.
[0058]
[Integral value reset action at saturation]
The integral limit value Sr calculated by | (Iref−Ip) / Ki | is set so that the sum of the proportional FB current Ip and the integral FB current Ii matches the command current Iref to the assist actuator 7 after the current limitation. This is the calculated integral value.
[0059]
Therefore, when the current limit value decreases with time during the saturation of the command current Iref (for example, by performing the current limit as shown in FIG. 10, the current limit values Ilmt + and Ilmt− are increased as the turning acceleration is increased by the driver's steering. When the current limit values Ilmt + and Ilmt− decrease, the integral value S also decreases, and immediately after the current limit values Ilmt + and Ilmt− are restored, the saturation of the command current Iref is canceled and excessive integration occurs. Since the value S does not occur, the behavior of the vehicle is stabilized and effective in preventing meandering.
[0060]
Similarly, while the command current Iref is saturated, the lateral position, lateral velocity, yaw rate, yaw angle with respect to the lane, steering angle, steering angular velocity, etc., detected or estimated using the white line information increase, thereby increasing the proportional FB current. When Ip increases, the integral value S decreases in proportion to the increase of the proportional FB current Ip, and immediately after the proportional FB current Ip recovers, the saturation of the command current Iref is canceled and no excessive integral value S is generated. Therefore, the behavior of the vehicle is stabilized and effective in preventing meandering.
[0061]
Next, the effect will be described.
[0062]
In the lane keep assist control device according to the second embodiment, it is determined that the command current Iref from the command current limiter 15i is in a saturated state where the command current limit values Ilmt + and Ilmt− are equal to those shown in FIG. When the command current limit values Ilmt + and Ilmt− decrease with time, the integral limit value Sr is calculated by the expression | (Iref−Ip) / Ki |, and the integral value S is calculated using the obtained integral limit value Sr. Since the integral limit value calculation unit 15k for resetting the current limit values Ilmt +, Ilmt- and the proportional FB current Ip is recovered, the command current Iref is saturated immediately and excessive steering due to the accumulation of the integral value S is performed. By suppressing the generation of torque, it is possible to stabilize the vehicle behavior after recovery from command current saturation and to improve straight running performance.
[0063]
(Embodiment 3)
The control system according to the third embodiment includes both the integral calculation stop determination unit 15j according to the first embodiment and the integral limit value calculation unit 15k according to the second embodiment, and as shown in FIG. When the relative relationship between y and the turning radius R based on the road curvature is a relationship in which the vehicle moves away from the center of the lane, the integral calculation stop determination unit 15j selects to hold the integral value S. Also, the vehicle lateral position y and the road curvature are selected. When the relative relationship of the turning radius R based on the relationship is such that the vehicle approaches the center of the lane, the integral value S is reset by the integral limit value calculation unit 15k, and when the vehicle lateral position y is at the center of the lane, the turning radius R An integral value suppression switching unit (integral value suppression switching means) that is not shown in the figure can be used to switch the process for suppressing the accumulation of the integral value S, such as selecting integral clear (reset to 0) regardless of the direction and magnitude. Digits is an example.
[0064]
Next, the operation will be described.
[0065]
When the integral value S selected by the integral value suppression switching unit is held, the integral FB current Ii tends to be excessive, and the integral value S selected by the integral value suppression switching unit is reset when the integral value S is reset. Due to the decrease, the integrated FB current Ii tends to be insufficient.
[0066]
Therefore, for example, when the vehicle is approaching the right side of the road while traveling on the right curve, the vehicle gradually approaches the center of the lane even if the vehicle goes straight. Is secured. The same applies when the vehicle is on the left side of the road while traveling on the left curve.
[0067]
In addition, for example, when the vehicle is on the left side of the road while traveling on the right curve, and when the vehicle goes straight, the vehicle gradually moves away from the center of the lane. Is secured. The same applies when the vehicle is on the right side of the road while traveling on the left curve.
[0068]
In this way, depending on the relative relationship between the vehicle lateral position y and the turning radius R (or road curvature), when the vehicle moves away from the center of the lane, it is selected to maintain the integrated value S, and the vehicle approaches the center of the lane. By selecting the reset of the integral value S at the time of the relationship, the integral FB current Ii after the saturation of the command current Iref is eliminated can be set to an appropriate value.
[0069]
Next, the effect will be described.
[0070]
In the lane keep assist control apparatus of the third embodiment, when the relative relationship between the vehicle lateral position y and the turning radius R is a relationship in which the vehicle moves away from the center of the lane, the integral value S of the integral calculation stop determination unit 15j In addition, when the relative relationship between the vehicle lateral position y and the turning radius R is a relationship in which the vehicle approaches the center of the lane, the reset of the integral value S by the integral limit value calculation unit 15k is selected. Since the integral value suppression switching unit that switches the processing for suppressing the accumulation of the integral value S is provided, it is possible to cope with various turning traveling situations and to always achieve both stable vehicle behavior and lane followability.
[0071]
(Other embodiments)
Although the present invention has been described in the first, second, and third embodiments, the specific configuration is not limited to the first, second, and third embodiments.
[0072]
For example, in the first, second, and third embodiments, the example in which the output current limit that enables the driver's arbitrary steering intervention is performed using the current limit map shown in FIG. And the lower limit value) can be applied to those set with a constant value.
[Brief description of the drawings]
FIG. 1 is an overall system diagram showing an automobile steering system to which a lane keep assist control device according to a first embodiment is applied;
FIG. 2 is a block diagram showing a control system in the lane keep assist control apparatus of the first embodiment.
FIG. 3 is a flowchart showing a flow of an actuator drive current calculation process performed by the lane keep control unit in the first embodiment.
FIG. 4 is an explanatory view of integral calculation stop determination in the first embodiment.
FIG. 5 is a comparison characteristic diagram showing a conventional current characteristic in which integral stop determination is not performed when a vehicle lateral displacement occurs, and a current characteristic in the first embodiment in which integral stop determination is performed.
FIG. 6 is a block diagram showing a control system in the lane keep assist control apparatus according to the second embodiment.
FIG. 7 is a flowchart showing a flow of actuator drive current calculation processing performed by the lane keep control unit in the second embodiment.
FIG. 8 is a diagram showing a selection map of integral holding, integral reset, and integral clear based on a relative relationship between a vehicle lateral position and a turning radius when current is saturated in the integral value suppression switching unit according to the third embodiment.
FIG. 9 is a block diagram showing a control system in a conventional lane keep assist control device.
FIG. 10 is a diagram showing a current limit map at the time of lane keep assist.
FIG. 11 is a vehicle turning acceleration-steering torque characteristic diagram during slalom traveling.
FIG. 12 is a steering intervention torque characteristic diagram when the current limit value is a constant value.
FIG. 13 is a steering intervention torque characteristic diagram when the current of the system is limited.
[Explanation of symbols]
1 Steering column
2 Column shaft
3 Steering wheel
4,5 left and right wheels
6 Hydraulic power steering mechanism
7 Assist actuator (steering actuator)
8 Motor
9 Electromagnetic clutch
10 Drive gear
11 Driven gear
13 Steering angle sensor
14 Encoder
15 Lane Keep Control Unit
16 Camera & image processing device

Claims (3)

A target trajectory calculating means for calculating a target lateral position of the vehicle according to the road curvature detected or estimated using the white line information;
Proportional to calculate the proportional feedback current by multiplying the vector with the factor of the lateral position, lateral velocity, yaw rate, yaw angle, steering angle, steering angular velocity, etc. of the vehicle detected or estimated using white line information and proportional feedback gain A feedback section;
An integral feedback unit that calculates an integral feedback current obtained by multiplying the integral value of the target deviation between the detected vehicle lateral displacement and the target lateral displacement from the target trajectory calculating means by a predetermined integral feedback gain;
Current adding means for adding the proportional feedback current and the integral feedback current;
Based on a preset command current limit value that enables an arbitrary steering intervention of the driver , or a command current limit value calculated according to a turning acceleration that enables an arbitrary steering intervention of the driver, etc. Command current limiting means for obtaining a command current to the steering actuator by performing output current limitation;
In the lane keep assist control device with
When the command current from the command current limiting means is in a saturated state where the command current is equal to the command current limit value, the integral feedback unit only performs an integration operation in the direction of decreasing the command current and increases the command current. A lane-keep assist control device provided with integral calculation stop judging means for holding an integral value at that time without performing a calculation. A target trajectory calculating means for calculating a target lateral position of the vehicle according to the road curvature detected or estimated using the white line information;
Proportional to calculate the proportional feedback current by multiplying the vector with the factor of the lateral position, lateral velocity, yaw rate, yaw angle, steering angle, steering angular velocity, etc. of the vehicle detected or estimated using white line information and proportional feedback gain A feedback section;
An integral feedback unit that calculates an integral feedback current obtained by multiplying the integral value of the target deviation between the detected vehicle lateral displacement and the target lateral displacement from the target trajectory calculating means by a predetermined integral feedback gain;
Current adding means for adding the proportional feedback current and the integral feedback current;
Based on a preset command current limit value that enables an arbitrary steering intervention of the driver , or a command current limit value calculated according to a turning acceleration that enables an arbitrary steering intervention of the driver, etc. Command current limiting means for obtaining a command current to the steering actuator by performing output current limitation;
In the lane keep assist control device with
When it is determined that the command current from the command current limiting means is in a saturated state where the command current limit value is equal to the command current limit value, and the command current limit value decreases with time, the difference between the command current and the proportional feedback current A lane keep assist control device comprising an integral limit value calculating means for calculating a corresponding integral limit value and resetting the integral value of the integral feedback unit. A target trajectory calculating means for calculating a target lateral position of the vehicle according to the road curvature detected or estimated using the white line information;
Proportional to calculate the proportional feedback current by multiplying the vector with the factor of the lateral position, lateral velocity, yaw rate, yaw angle, steering angle, steering angular velocity, etc. of the vehicle detected or estimated using white line information and proportional feedback gain A feedback section;
An integral feedback unit that calculates an integral feedback current obtained by multiplying the integral value of the target deviation between the detected vehicle lateral displacement and the target lateral displacement from the target trajectory calculating means by a predetermined integral feedback gain;
Current adding means for adding the proportional feedback current and the integral feedback current;
Based on a preset command current limit value that enables an arbitrary steering intervention of the driver , or a command current limit value calculated according to a turning acceleration that enables an arbitrary steering intervention of the driver, etc. Command current limiting means for obtaining a command current to the steering actuator by performing output current limitation;
In the lane keep assist control device with
The integral feedback unit only performs an integration operation in the direction of decreasing the command current, does not perform an integration operation that increases the command current, and retains the integral value at that time, a command current and An integral limit value calculating means for calculating an integral limit value according to the difference from the proportional feedback current and resetting the integral value of the integral feedback unit is provided together.
When the command current from the command current limiter is in a saturated state where the command current limit value is equal to the command current limit value, the relationship between the vehicle lateral position detected or estimated by the white line information and the road curvature is the relationship in which the vehicle moves away from the center of the lane. Integral value suppression switching means is provided for switching the processing for suppressing the accumulation of integral values, such as selecting the retention of the integral value when the vehicle is moving, and selecting the reset of the integral value when the vehicle is moving toward the center of the lane. A lane keep assist control device.

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