Precedent vehicle follow-up controlling device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a control device that follows a preceding vehicle while maintaining a constant inter-vehicle distance.

【0002】

[Conventional technology]

The acceleration / deceleration when traveling on a flat road is estimated based on the throttle valve opening of the engine when traveling on a slope, the shift position of the transmission, and the vehicle speed, and the driven wheel speed is differentiated to determine the vehicle when traveling on a slope. A preceding vehicle tracking control device that detects the actual acceleration / deceleration of the vehicle, estimates the gradient resistance from the acceleration / deceleration of the difference between the actual acceleration / deceleration and the estimated acceleration / deceleration, and corrects the braking force of the vehicle based on the estimated gradient resistance. Is known (see, for example, Japanese Patent Application Laid-Open No. 11-091396).

【0003】

[Problems to be Solved by the Invention]

By the way, in a section where the road gradient of an expressway changes significantly, the traveling speed of each vehicle fluctuates due to the gradient resistance, and the traffic density tends to be sparse and dense, which may reduce the traffic flow rate. Such road sections are commonly referred to as "sags" and are frequently congested. On the other hand, vehicles equipped with a vehicle speed control device (ASCD) for keeping the vehicle speed constant are becoming widespread, and are expected to have the effect of suppressing vehicle speed fluctuations in the sag section and alleviating traffic congestion. However, in reality, there are not many opportunities to continue running on the highway at a constant speed, and the vehicle speed control device is repeatedly activated and stopped every time the distance between the vehicle and the preceding vehicle is adjusted.

【0004】

Therefore, an inter-vehicle distance control device (ACC) for keeping the inter-vehicle distance from the preceding vehicle constant has been developed and has begun to be installed in commercial vehicles. However, in this inter-vehicle distance control device, since the control target is the inter-vehicle distance from the vehicle speed, the vehicle speed fluctuation becomes large due to the influence of the gradient resistance in the sag section. Therefore, it is necessary to compensate the gradient resistance in some way in order to maintain the same tracking characteristics as the flat road even in the sag section. The preceding vehicle tracking control device (Japanese Patent Laid-Open No. 11-091396) described above is designed to solve such a problem, but adopts a method of compensating for gradient resistance while continuing inter-vehicle distance control. Therefore, the following problems occur.

【0005】

In the conventional preceding vehicle follow-up control device described above, the correct gradient resistance estimate cannot be obtained at the entrance and exit of the slope road due to the operation delay of the sensor and actuator, and the estimated value can be immediately reflected in the control. Can not. As a result, a large control error temporarily occurs. For example, at a point where a flat road changes to an uphill road, the vehicle speed will temporarily decrease, and when multiple vehicles are traveling in a platoon by controlling the inter-vehicle distance, the inter-vehicle distance will be narrowed due to the temporary deceleration of the preceding vehicle. The following vehicle will also decelerate, and the upward gradient resistance will further decelerate. This phenomenon is greater for vehicles behind the platoon. On the contrary, at the point where the road changes to a downhill road, a phenomenon occurs in which the vehicle behind the vehicle accelerates and then decelerates significantly.

【0006】

Such fluctuations in vehicle speed in inter-vehicle distance control not only give the vehicle occupants a sense of discomfort, but also may induce congestion due to local sparse and dense traffic flow density.

【0007】

An object of the present invention is to suppress fluctuations in vehicle speed during preceding vehicle tracking control in a road section where a slope changes.

【0008】

[Means for solving problems]

The present invention will be described in association with FIG. 1, which shows the configuration of one embodiment. (1) The invention of claim 1 is an own vehicle speed detecting means 2 for detecting the own vehicle speed, an inter-vehicle distance detecting means 1 for detecting the inter-vehicle distance with a preceding vehicle, and a gradient detection for detecting a change in the slope in front of the driving road. Means 3 and from vehicle-to-vehicle distance control that controls the inter-vehicle distance detection value to be the target inter-vehicle distance when a change in slope is detected in front of the driving road, to vehicle speed control that controls the vehicle speed detection value to be the target vehicle speed. Control switching means 4 for switching, control driving force calculation means 4 for calculating the target control driving force for achieving inter-vehicle distance control or vehicle speed control, and control drive for controlling the control drive force of the vehicle based on the target control drive force. It is provided with a force control means 4. (2) The preceding vehicle following control device according to claim 2 is such that the control switching means 4 switches from inter-vehicle distance control to vehicle speed control when the preceding vehicle reaches a point a predetermined distance before the slope change point. is there. (3) The preceding vehicle tracking control device according to claim 3 sets the target vehicle speed to the own vehicle speed or the vehicle speed of the preceding vehicle according to the acceleration / deceleration state of the own vehicle and the preceding vehicle when the inter-vehicle distance control is switched to the vehicle speed control. Alternatively, the target vehicle speed setting means 4 for setting an intermediate value between the own vehicle speed and the preceding vehicle speed is provided. (4) The preceding vehicle tracking control device of claim 4 reduces the target vehicle speed when the driving road is uphill and increases the target vehicle speed when the driving road is downhill by the target vehicle speed setting means 4. It was done. (5) The preceding vehicle tracking control device according to claim 5 uses the control switching means 4 to switch from vehicle speed control to inter-vehicle distance control when the vehicle speed control error on a slope road continues to be equal to or less than a predetermined value for a predetermined time or longer. Is. (6) The preceding vehicle tracking control device according to claim 6 is configured to switch from vehicle speed control to inter-vehicle distance control when the state in which the acceleration estimated value of the preceding vehicle is within a predetermined range continues for a predetermined time or longer by the control switching means 4. It is a thing. (7) The preceding vehicle tracking control device according to claim 7 is switched to inter-vehicle distance control by the control switching means 4 when the inter-vehicle distance to the preceding vehicle exceeds a preset allowable range for the inter-vehicle distance during vehicle speed control. It is a thing. (8) The preceding vehicle tracking control device according to claim 8 expands the permissible range toward a smaller inter-vehicle distance according to the slope inclination angle when the driving road is uphill, and increases the slope inclination angle when the driving road is downhill. Correspondingly, the permissible range is expanded to the one with a larger inter-vehicle distance. (9) The preceding vehicle tracking control device according to claim 9 achieves the target driving force and the inter-vehicle distance control for achieving the vehicle speed control when switching from the vehicle speed control to the inter-vehicle distance control by the control driving force calculation means 4. The target driving force is calculated by averaging the target driving force for vehicle speed control, and the weighted value for the target driving force of vehicle speed control is continuously changed from 1 to 0 to control the distance between vehicles. The weighted value for the driving force is continuously changed from 0 to 1. (10) The preceding vehicle tracking control device according to claim 10 generates a virtual vehicle that continues to run at the target vehicle speed at the same position as the preceding vehicle when switching from the inter-vehicle distance control to the vehicle speed control, and the inter-vehicle distance with respect to the virtual vehicle. The vehicle speed control means 4 for realizing vehicle speed control by performing control is provided. (11) The preceding vehicle tracking control device according to claim 11 is a provisional inter-vehicle distance obtained by weighting and averaging the inter-vehicle distance with the virtual vehicle and the actual inter-vehicle distance detection value when switching from the vehicle speed control by the vehicle speed control means 4 to the inter-vehicle distance control. Inter-vehicle distance control means that calculates the detected value, continuously changes the weighted value for the inter-vehicle distance to the virtual vehicle from 1 to 0, and continuously changes the weighted value for the actual inter-vehicle distance detected value from 0 to 1. Equipped with 4.

【0009】

In the section of means for solving the above-mentioned problems, the figure of one embodiment is used to make the explanation easy to understand, but the present invention is not limited to one embodiment.

【0010】

[Effect of the invention]

(1) According to the invention of claim 1, the change in the slope in front of the driving road is detected, and when the change in the slope in front of the driving road is detected, the inter-vehicle distance control is switched to the vehicle speed control. It is possible to suppress fluctuations in vehicle speed during preceding vehicle follow-up control in changing road sections, and in particular, even if the slope changes when multiple vehicles are traveling in a row, the vehicle speed due to changes in the road slope of the preceding vehicle It is possible to prevent the phenomenon that the fluctuation is amplified and propagated to the vehicle behind. As a result, it is possible to reduce the occurrence of traffic congestion in the sag section and the feeling of strangeness in the conventional inter-vehicle distance control. (2) According to the invention of claim 2, when the preceding vehicle reaches a point in front of the gradient change point by a predetermined distance, the inter-vehicle distance control is switched to the vehicle speed control, so that the preceding vehicle receives the gradient resistance. It is possible to switch to vehicle speed control before accelerating or decelerating, and it is possible to completely eliminate the influence of vehicle speed changes due to the gradient resistance of the preceding vehicle. (3) According to the invention of claim 3, when the inter-vehicle distance control is switched to the vehicle speed control, the target vehicle speed is set to the own vehicle speed or the vehicle speed of the preceding vehicle or the own vehicle speed according to the acceleration / deceleration state of the own vehicle and the preceding vehicle. Since the value is set to an intermediate value with the vehicle speed, it is possible to avoid a situation in which the inter-vehicle distance becomes too short or too wide during vehicle speed control due to an inappropriate vehicle speed setting. (4) According to the invention of claim 4, the target vehicle speed is reduced when the driving road is uphill, and the target vehicle speed is increased when the driving road is downhill. It is possible to prevent the inter-vehicle distance on the road from becoming too short and the inter-vehicle distance on the downhill road from becoming too wide. (5) According to the invention of claim 5, if the vehicle speed control error on the slope road continues to be equal to or less than a predetermined value for a predetermined time or longer, the vehicle speed control is switched to the inter-vehicle distance control. After the process is completed, the vehicle-to-vehicle distance control is switched to, and it is no longer necessary to compensate for the inter-vehicle distance and the gradient resistance at the same time, and the acceleration / deceleration of the own vehicle can be suppressed to the minimum. (6) According to the invention of claim 6, the acceleration of the preceding vehicle is estimated, and if the state in which the estimated acceleration value of the preceding vehicle is within the predetermined range continues for a predetermined time or longer, the vehicle speed control is switched to the inter-vehicle distance control. After the compensation for the gradient resistance of the vehicle is completed, the inter-vehicle distance control is switched to, the influence of the change in the vehicle speed of the preceding vehicle is reduced, and the acceleration / deceleration of the own vehicle can be suppressed to the minimum. (7) According to the invention of claim 7, if the inter-vehicle distance to the preceding vehicle exceeds the allowable range for the preset inter-vehicle distance during vehicle speed control, the inter-vehicle distance control is switched to, so that the vehicle is too close to the preceding vehicle. Or, if the vehicle is too far away, it can be switched to inter-vehicle distance control before danger or discomfort occurs, and it is possible to respond to a situation in which the preceding vehicle accelerates or decelerates more than expected. (8) According to the invention of claim 8, when the driving road is an uphill slope, the permissible range for the inter-vehicle distance is expanded according to the slope inclination angle, and when the driving road is a downhill slope, the permissible range is expanded. Since the allowable range is expanded to the one with a larger inter-vehicle distance according to the inclination angle, it is possible to predict the approximate degree of speed change of the preceding vehicle by using the information on the slope road, and the vehicle speed is controlled unnecessarily. It is possible to avoid switching from to vehicle-to-vehicle distance control. (9) According to the invention of claim 9, when switching from vehicle speed control to inter-vehicle distance control, a target driving force for achieving vehicle speed control and a target driving force for achieving inter-vehicle distance control are weighted. The target driving force is calculated by averaging, and the weighted value for the target driving force for vehicle speed control is continuously changed from 1 to 0, and the weighted value for the target driving force for inter-vehicle distance control is changed from 0 to 1. Since it is changed continuously, the target driving force of vehicle speed control and inter-vehicle distance control can be continuously switched, and it is possible to prevent a steep driving force or braking force from being generated when the control is switched. it can. (Ten) According to the invention of claim 10, when switching from the inter-vehicle distance control to the vehicle speed control, a virtual vehicle that continues to run at the target vehicle speed is generated at the same position as the preceding vehicle, and the inter-vehicle distance control is performed on the virtual vehicle. The vehicle speed control is realized. As a result, the vehicle speed is equivalently obtained by simply replacing the vehicle-to-vehicle distance measurement value with the calculated value of the inter-vehicle distance with the virtual vehicle (the value obtained by adding the integrated value of the vehicle speed control error to the initial inter-vehicle distance) while keeping the inter-vehicle distance control rule as it is. Control can be realized, and when switching from vehicle speed control to inter-vehicle distance control, the virtual vehicle should be moved so as to match the actual preceding vehicle, so the inter-vehicle distance control control algorithm can be used almost as it is for vehicle speed control. , The software configuration of the control system can be simplified. (11) According to the invention of claim 11, when switching from the vehicle speed control to the inter-vehicle distance control, the inter-vehicle distance with the virtual vehicle and the actual inter-vehicle distance detection value are weighted and averaged to calculate the provisional inter-vehicle distance detection value. The weight value for the inter-vehicle distance with the virtual vehicle is continuously changed from 1 to 0, and the weight value for the actual inter-vehicle distance detection value is continuously changed from 0 to 1. As a result, it is possible to prevent a steep driving force or braking force from being generated when switching between vehicle speed control and inter-vehicle distance control.

【0011】

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a diagram showing equipment arrangement in a vehicle of one embodiment, and FIG. 2 is a diagram showing a configuration of one embodiment. The inter-vehicle distance sensor 1 is attached to the front of the vehicle and irradiates a radar wave in front of the vehicle to measure the inter-vehicle distance from the preceding vehicle. A laser radar or a millimeter-wave radar can be used for the inter-vehicle distance sensor 1. The vehicle speed sensor 2 detects the vehicle speed by attaching a rotary encoder to the wheel and measuring a pulse having a period corresponding to the rotation speed of the wheel. The slope detection device 3 detects a point where the road slope changes in front of the vehicle's course. For example, a GPS receiver and a road map database are used to detect the current position and driving road of the own vehicle, and the road slope change point is detected.

【0012】

The travel control controller 4 is composed of a microcomputer and its peripheral parts, and controls the throttle valve actuator 5, the transmission 7, and the brake actuator 8 based on the information from the inter-vehicle distance sensor 1, the vehicle speed sensor 2, and the slope detection device 3. .. The travel control controller 4 constitutes a target driving force calculation unit 4a, a gradient resistance estimation unit 4b, a control target generation unit 4c, and an actuator command value calculation unit 4d shown in FIG. 2 according to the software form of the microcomputer. Details of each of these parts will be described later.

【0013】

The throttle valve actuator 5 adjusts the throttle valve opening degree of the engine 6 according to the throttle valve opening degree command from the traveling control controller 4 to control the driving force of the vehicle. The transmission 7 controls the driving force of the vehicle by changing the gear ratio according to the gear ratio command from the travel control controller 4. The brake actuator 8 adjusts the brake fluid pressure according to the brake hydraulic pressure command from the travel control controller 4 to control the braking force of the vehicle.

【0014】

FIG. 3 is a flowchart showing a preceding vehicle follow-up control program. The operation of one embodiment will be described with reference to this flowchart. The travel control controller 4 repeatedly executes this control program when the main switch (not shown) of the preceding vehicle follow-up control device is turned on.

【0015】

In step 1, the inter-vehicle distance measurement value is taken into the memory (not shown) from the inter-vehicle distance sensor 1, and in the following step 2, the own vehicle speed measurement value is taken into the memory from the vehicle speed sensor 2. Further, in step 3, the gradient road information such as the inclination angle of the gradient road in front of the vehicle and the distance to the change point is taken into the memory from the gradient road detection device 3. In step 4, the control target determination routine shown in FIG. 4 is executed, and the control target that the vehicle should take based on the vehicle-to-vehicle distance, the vehicle speed, and the slope road information, that is, the vehicle speed control or the vehicle-to-vehicle distance control, or an intermediate state between them is determined. When the judgment is made and the control target of the judgment result is different from the current control target, the control target is switched and reflected in the target control driving force calculation (control target generation unit 4c). The determination process of this control target will be described later.

【0016】

The gradient resistance acting on the own vehicle is estimated based on the target driving force, the own vehicle speed, and the running model of the vehicle calculated at the time of the previous execution of this preceding vehicle follow-up control program in step 5 (gradient resistance estimation unit). 4b). The specific estimation method will be described later. Next, in step 6, the target driving force is calculated based on the inter-vehicle distance and the own vehicle speed according to the control rule corresponding to the control target of the judgment result, and the target driving force is corrected by the estimated gradient resistance (target driving force). Force calculation unit 4a). In this embodiment, known control rules for inter-vehicle distance control and vehicle speed control are adopted, and detailed description of these control rules will be omitted.

【0017】

In step 7, the throttle valve opening command value, the brake fluid pressure command value, and the gear ratio command value for achieving the target driving force are calculated and sent to the throttle valve actuator 5, the transmission 7, and the brake actuator 8 (actuator). Command value calculation unit 4d). As for the calculation method of these command values, a known method shall be adopted, and the description thereof will be omitted here.

【0018】

Next, a method of estimating the gradient resistance will be described. Assuming that the vehicle speed is V, the gradient resistance acting on the vehicle is f, and the command value to the actuator is u, the relationship between the vehicle speed v, the gradient resistance f, and the command value u is modeled as follows. Can be done.

[Number 1]

<img file="JP2002137652A_D0001.tif" />In Equation 1, P1 (s) is a transfer function that represents the dynamics of the actuator, for example. [Number 2]

<img file="JP2002137652A_D0002.tif" />A transfer function like this can be assumed. In Equation 2, s is the Laplace operator. In addition, P2 (s) is a transmission characteristic from the force acting on the vehicle to the own vehicle speed, and assuming that the mass of the vehicle is M, [Number 3]

<img file="JP2002137652A_D0003.tif" />Will be. In Equation 3, s is the Laplace operator. Next, when Equation 1 is transformed and solved for the gradient resistance f, [Number 4]

<img file="JP2002137652A_D0004.tif" />Is obtained, but P2^-1Since (s) is not proper, a strictly proper filter H (s) with a relative order of 1 or more is introduced, and the following signal is created and used as the correction value.

[Number 5]

<img file="JP2002137652A_D0005.tif" />Let r be the command value of the actuator before correction by the gradient resistance, and let u be the command value after correction. [Number 6]

<img file="JP2002137652A_D0006.tif" />Then, the relationship between the vehicle speed v, the gradient resistance f, and the command value u is [Number 7]

<img file="JP2002137652A_D0007.tif" />Will be. Assuming that the gradient resistance changes stepwise, in order to asymptotically eliminate the influence of the gradient resistance, the zero point of the transfer function of the second term on the right side of Equation 7 should be placed at the origin. As H (s) satisfying such a condition, for example, [Number 8]

<img file="JP2002137652A_D0008.tif" />There is. However, ζ and ω are positive constants.

【0019】

Next, the control target determination process will be described with reference to the flowchart shown in FIG. In step 11, it is confirmed whether or not the inter-vehicle distance control is in progress. It is assumed that a preceding vehicle exists on a road having a constant gradient and that the inter-vehicle distance control for controlling the inter-vehicle distance to the preceding vehicle is being performed. When the inter-vehicle distance control is in progress, the process proceeds to step 12, the distance from the preceding vehicle to the slope change point is calculated based on the slope road information from the slope road detection device 3, and it is determined whether or not to switch to the vehicle speed control. The distance from the preceding vehicle to the slope change point may be obtained by subtracting the inter-vehicle distance from the distance from the own vehicle to the slope change point. The switching from the inter-vehicle distance control to the vehicle speed control may be performed when the distance from the preceding vehicle to the gradient change point reaches a predetermined distance, for example, 50 m, or until the preceding vehicle reaches the gradient change point. It may be performed when the time of is a predetermined time, for example, 1.5 sec. In the latter case, the distance for switching to vehicle speed control changes according to the vehicle speed of the preceding vehicle.

【0020】

In this way, when the preceding vehicle reaches a point in front of the gradient change point by a predetermined distance, or when the time until the preceding vehicle reaches the gradient change point reaches a predetermined time, the inter-vehicle distance control is switched to the vehicle speed control. Therefore, it is possible to switch to vehicle speed control before the preceding vehicle receives the gradient resistance and accelerates / decelerates, and the influence of the vehicle speed change due to the gradient resistance of the preceding vehicle can be completely eliminated.

【0021】

If the gradient change points are not approaching in step 12, the inter-vehicle distance control is continued and the vehicle returns to step 5 in FIG. On the other hand, when the gradient change point approaches and the vehicle speed control is switched to, the process proceeds to step 13, the target vehicle speed is set, and the control target is switched from the inter-vehicle distance control to the vehicle speed control. Here, the own vehicle speed at the time of switching or the vehicle speed of the preceding vehicle may be set as the target vehicle speed. Further, as shown in FIG. 5, an appropriate intermediate value may be set from the accelerations of the own vehicle and the preceding vehicle as the target vehicle speed. By setting the target vehicle speed according to the acceleration, it is possible to avoid a situation in which the inter-vehicle distance becomes too short or too wide during vehicle speed control due to an inappropriate vehicle speed setting.

【0022】

In Fig. 5, when the acceleration of the preceding vehicle is positive and the acceleration of the own vehicle is negative, that is, when the preceding vehicle is in the accelerating state and the own vehicle is in the decelerating state, the own vehicle speed V1 is set as the target vehicle speed, and vice versa. , When the acceleration of the own vehicle is a positive value and the acceleration of the preceding vehicle is a negative value, that is, when the preceding vehicle is in the deceleration state and the own vehicle is in the acceleration state, the vehicle speed Vf of the preceding vehicle is set as the target vehicle speed. When the acceleration of the own vehicle and the preceding vehicle is almost 0, that is, when the own vehicle and the preceding vehicle are traveling at a constant speed, the target vehicle speed is the intermediate value (V1 + Vf) / 2 of the own vehicle speed V1 and the vehicle speed Vf of the preceding vehicle. To do. When the accelerations of the own vehicle and the preceding vehicle are both positive or negative, the target is the median value (V1 + 2Vf) / 3 on the vehicle speed side or the median value (2Vl + Vf) / 3 on the preceding vehicle side as shown in the figure. Set to vehicle speed.

【0023】

Further, when the value of the inclination angle of the gradient is known, a more appropriate vehicle speed target can be set by correcting the target vehicle speed according to the inclination angle of the gradient. For example, on an uphill slope where the inclination angle suddenly increases, the vehicle speed of the preceding vehicle decreases significantly. Further, when the preceding vehicle is not traveling by vehicle speed control or inter-vehicle distance control, the vehicle may continue to drive while the vehicle speed is reduced. In such a case, if the preceding vehicle speed before entering the slope road is set as the target vehicle speed, the target vehicle speed is set faster than the preceding vehicle speed after entering the slope road, so that the inter-vehicle distance is shortened. On the contrary, on a downhill slope where the inclination angle suddenly increases, the inter-vehicle distance becomes larger than necessary. In any case, the driver feels uncomfortable on a slope road where the inclination angle changes greatly. Therefore, on a slope road where the inclination angle changes greatly and a large vehicle speed fluctuation is expected, the target vehicle speed is set in consideration of the vehicle speed fluctuation of the preceding vehicle. For example, at a point where the inclination angle changes by 5% or more, the target vehicle speed is increased by 1 km / h on the uphill slope and the target is decreased by 1 km / h on the downhill slope for each 1% increase in the inclination angle. As a result, it is possible to avoid fluctuations in the inter-vehicle distance that give the driver a sense of discomfort even on a slope road with a large change in the inclination angle.

【0024】

When the switching from the inter-vehicle distance control to the vehicle speed control is completed in step 13, the process proceeds to step 14 to monitor the inter-vehicle distance with the preceding vehicle. If the inter-vehicle distance becomes so tight that it makes the driver feel uncomfortable, or if there is a divergence, proceed to step 16 and switch to inter-vehicle distance control again to maintain an appropriate inter-vehicle distance. It is necessary to switch from vehicle speed control to inter-vehicle distance control when the preceding vehicle is not traveling by vehicle speed control or inter-vehicle distance control, and when the driver does not adjust the vehicle speed or when the vehicle ahead is congested. .. The condition for switching from one-vehicle speed control to inter-vehicle distance control is that if the inter-vehicle distance or inter-vehicle time (= (inter-vehicle distance) / (preceding vehicle speed or own vehicle speed)) exceeds the allowable range during vehicle speed control, the inter-vehicle distance Switch to distance control. For example, if the distance is 30% or more shorter than the set distance or the set time, or is 50% or more longer, the vehicle is switched to the distance control.

【0025】

In this way, when the inter-vehicle distance or inter-vehicle time with the preceding vehicle exceeds the allowable range for the preset inter-vehicle distance or inter-vehicle time during vehicle speed control, the inter-vehicle distance control is switched to. As a result, even if the preceding vehicle accelerates or decelerates and the inter-vehicle distance or inter-vehicle time increases or decreases more than expected, the inter-vehicle distance or inter-vehicle time can be immediately returned to the set inter-vehicle distance.

【0026】

However, it must be avoided that the vehicle speed control is easily switched to the inter-vehicle distance control for the natural acceleration / deceleration of the preceding vehicle caused only by the gradient resistance. Therefore, if the inclination angle of the slope road is known, the change in vehicle speed of the preceding vehicle is predicted, and the vehicle speed control is easily switched to the inter-vehicle distance control for natural acceleration / deceleration caused only by the gradient resistance of the preceding vehicle. Correct the above tolerance of inter-vehicle distance or inter-vehicle time so that there is no such thing. Now, consider a case where the inter-vehicle distance is controlled by the inter-vehicle time h for the preceding vehicle traveling at a constant speed. Assuming that the inclination angle of the slope road is θ, if the own vehicle switches to vehicle speed control and the preceding vehicle continues to run without adjusting the vehicle speed, the change in the inter-vehicle distance when the own vehicle approaches the slope road is [Number 9]

<img file="JP2002137652A_D0009.tif" />Can be estimated. In Equation 9, g is the gravitational acceleration.

【0027】

Assuming how quickly the compensation for gradient resistance starts, it is conceivable to set the permissible amount of change in inter-vehicle distance using Equation 9 as a guide. Hereinafter, an example of setting the inter-vehicle distance allowance when changing from a flat road to a slope road will be described with reference to FIG. The lower limit of the inter-vehicle distance tolerance before correction, that is, the threshold value for switching from vehicle speed control to inter-vehicle distance control when the inter-vehicle distance becomes smaller than that, is k1 times the target inter-vehicle time (kl is 0 &lt;k1 &lt;1). If it is set as an appropriate constant), the threshold value will be k1, h, v0 (v0 is the target vehicle speed). Introduced the design parameter k2, which corresponds to the allowable degree of compensation delay of gradient resistance, and set the allowable inter-vehicle distance. [Number 10]

<img file="JP2002137652A_D0010.tif" />And set. In Equation 10, h · v0 represents the inter-vehicle distance before the preceding vehicle approaches the gradient change point, so if k2 = 1, the own vehicle reaches the gradient change point if the preceding vehicle does not perform gradient compensation. Matches the inter-vehicle distance at the time. If k2 is increased, the policy is to allow larger deceleration, and conversely, if k2 is decreased, the policy is to switch to inter-vehicle distance control unless the preceding vehicle compensates for the gradient resistance more quickly. The threshold value before correction is compared with the new allowable value of Equation 10, and the smaller value is set as the new threshold value so that Equation 10 falls within the allowable range. That is, the corrected threshold value Rthr is set to [Number 11]

<img file="JP2002137652A_D0011.tif" />It is determined as follows. As a result, the threshold value is corrected so that a slight compensation delay of the preceding vehicle is allowed, and it is possible to avoid unnecessarily switching from vehicle speed control to inter-vehicle distance control. The threshold value can be corrected in the same manner when the slope changes to a downward slope.

【0028】

In this way, when the driving road is an uphill slope, the permissible range of the inter-vehicle distance or the inter-vehicle time is expanded according to the slope inclination angle, and when the driving road is a downward slope, the permissible range of the inter-vehicle distance is expanded according to the slope inclination angle. The above allowable range is expanded to the one with a larger inter-vehicle distance. As a result, it is possible to predict the approximate degree of speed change of the preceding vehicle by using the information on the slope road, and it is possible to avoid unnecessarily switching from the vehicle speed control to the inter-vehicle distance control.

【0029】

If it is determined in step 14 that there is no abnormal approach or deviation from the preceding vehicle, the process proceeds to step 15 to determine whether or not the compensation for the gradient resistance of the own vehicle or the preceding vehicle has been completed. The end of the gradient resistance compensation of the own vehicle can be determined by the vehicle speed control error of the own vehicle. Vehicle speed control Using the vehicle speed accuracy of ASCD as a guide, set the allowable control error appropriately, for example, 0.5 km / h. The duration is determined by the performance of the gradient resistance estimator. The transfer function from the gradient resistance to the own vehicle can be found from Equation 7 above. [Number 12]

<img file="JP2002137652A_D0012.tif" />Is. The step response of this transfer function has a zero at the origin, so it should rise once and then converge to zero. The time to before the response goes out of the control error range and the time ti until it falls within the control error range are obtained, and an appropriate value is set as the duration of the end judgment in the range of to &lt;t &lt;ti.

【0030】

In this way, if the vehicle speed control error on the slope road continues to be equal to or less than a predetermined value for a predetermined time or longer, it is determined that the gradient resistance compensation of the own vehicle has been completed, and the vehicle speed control is switched to the inter-vehicle distance control. As a result, the vehicle-to-vehicle distance control is switched to after the compensation of the gradient resistance of the own vehicle is completed, so that it is not necessary to compensate the inter-vehicle distance and the gradient resistance at the same time, and the acceleration / deceleration of the own vehicle is minimized. Can be suppressed.

【0031】

On the other hand, the end of the gradient resistance compensation of the preceding vehicle is determined by the acceleration of the preceding vehicle. The acceleration of the preceding vehicle is relative to the speed of the preceding vehicle. [Number 13]

<img file="JP2002137652A_D0013.tif" />An approximate value can be estimated by applying a bandpass filter process such as. The speed of the preceding vehicle can also be obtained by adding the relative speed to the own vehicle speed. Relative velocity can be measured directly using a millimeter-wave radar, but an estimated value can be obtained by applying bandpass filtering as shown in Equation 13 to the inter-vehicle distance data. As the allowable value of acceleration, set an appropriate value, for example, + 0.05G to -0.05G by referring to the statistical value of the driver's deceleration behavior and the performance of the acceleration estimation system, and the duration is the end of compensation for the own vehicle speed. A value similar to the value set for the determination may be set.

【0032】

In this way, the acceleration of the preceding vehicle is estimated, and if the estimated acceleration value remains within the permissible range, for example, + 005G to -0.05G for a predetermined time or longer, it is determined that the gradient resistance compensation of the preceding vehicle is completed. , Switch from vehicle speed control to inter-vehicle distance control. As a result, the inter-vehicle distance control is switched to after the compensation for the gradient resistance of the preceding vehicle is completed, so that the influence of the change in the vehicle speed of the preceding vehicle is reduced, and the acceleration / deceleration of the own vehicle can be suppressed to the minimum.

【0033】

If it is determined in step 15 of FIG. 4 that the gradient resistance compensation is completed, the process proceeds to step 16, otherwise the vehicle speed is controlled and the vehicle returns to step 5 of FIG. In step 16 of FIG. 4, the control target is switched from vehicle speed control to inter-vehicle distance control. A method of switching to the control rule of the inter-vehicle distance control immediately after the judgment of switching to the inter-vehicle distance control is conceivable, but if there is a gap between the vehicle speed control and the inter-vehicle distance control control rule, sudden acceleration / deceleration occurs. It is not preferable because there is a possibility of doing so. Therefore, smooth switching is realized by setting a transient state that continuously connects the two control rules.

【0034】

The first method is to calculate the two control rules independently and take a linear combination of the two. Here, the control input corresponding to the vehicle speed control is uv, and the control input corresponding to the inter-vehicle distance control is ud. Also, consider an appropriate time function c (t) that monotonically increases from 0 to 1. For example [Number 14]

<img file="JP2002137652A_D0014.tif" />Let it be a function like. In Equation 14, γ is an appropriate positive constant. Transient control input utmp, [Number 15]

<img file="JP2002137652A_D0015.tif" />And determine it as the actuator command value. In this way, even if there is a gap between the control inputs uv and ud of the vehicle speed control and the inter-vehicle distance control, the control inputs uv and ud can be smoothly connected by appropriately selecting γ.

【0035】

In this way, when switching from vehicle speed control to inter-vehicle distance control, the control input (target control driving force) uv for achieving vehicle speed control and the control input (target control driving force) ud for achieving inter-vehicle distance control The actuator command value (target control driving force) is calculated by averaging the weighted additions, and the weighted value for the control input uv of vehicle speed control is continuously changed from 1 to 0, and the weighted value for the control input ud of inter-vehicle distance control. Is continuously changed from 0 to 1. As a result, the target driving force for vehicle speed control and inter-vehicle distance control can be continuously switched, and it is possible to prevent a steep driving force or braking force from being generated when the control is switched.

【0036】

The second method is to generate a virtual vehicle and continue the inter-vehicle distance control for the virtual vehicle. This method will be described with reference to FIG. In this method, when switching to vehicle speed control, a virtual vehicle that continues to run at the target vehicle speed is generated at the same position as the preceding vehicle, and then vehicle speed control is realized by controlling the inter-vehicle distance for the virtual vehicle. According to this method, the inter-vehicle distance control rule is left as it is, and the inter-vehicle distance measurement value is simply replaced with the calculated value of the inter-vehicle distance with the virtual vehicle (the value obtained by adding the integral value of the vehicle speed control error to the initial inter-vehicle distance). Vehicle speed control can be realized equivalently. When switching from vehicle speed control to inter-vehicle distance control, the virtual vehicle may be moved so as to match the actual preceding vehicle. Using the same time function c (t) as in Equation 14, the following provisional inter-vehicle distance measurement value Rc is obtained, where Ri is the inter-vehicle distance to the virtual vehicle that continues to run at a constant speed and R is the actual inter-vehicle distance measurement value. Calculate.

[Number 16]

<img file="JP2002137652A_D0016.tif" />If the inter-vehicle distance is controlled using this provisional inter-vehicle distance measurement value Rc until c (t) becomes 1, that is, if the inter-vehicle distance control is performed so that the provisional inter-vehicle distance measurement value Rc matches the target inter-vehicle distance, the predetermined time After 1 / γ, the provisional inter-vehicle distance measurement value Rc matches the actual inter-vehicle distance measurement value R, and it is possible to switch to normal inter-vehicle distance control.

【0037】

In this way, when switching from inter-vehicle distance control to vehicle speed control, vehicle speed control is realized by generating a virtual vehicle that continues to run at the target vehicle speed at the same position as the preceding vehicle and performing inter-vehicle distance control for that virtual vehicle. .. Furthermore, when switching from vehicle speed control to inter-vehicle distance control, the provisional inter-vehicle distance measurement value is calculated by weighting and averaging the inter-vehicle distance with the virtual vehicle and the actual inter-vehicle distance measurement value, and with respect to the inter-vehicle distance with the virtual vehicle. The weighted value is continuously changed from 1 to 0, and the weighted value with respect to the actual inter-vehicle distance measurement value is continuously changed from 0 to 1. As a result, it is possible to prevent a steep driving force and braking force from being generated when switching between vehicle speed control and inter-vehicle distance control, and the inter-vehicle distance control control algorithm can be used almost as it is for vehicle speed control. , The software configuration of the control system can be simplified.

【0038】

FIGS. 8 and 9 simulate the speed change of each vehicle when a group of five vehicles enters an uphill road, and FIG. 8 shows a case where the vehicle travels only by the conventional inter-vehicle distance control. Shown, FIG. 9 shows a case where the vehicle travels by a method of switching between vehicle speed control and inter-vehicle distance control according to this embodiment. In FIGS. 8 and 9, the horizontal axis indicates the time [sec], and the vertical axis indicates the traveling speed [km / h] of each vehicle. As is clear from these figures, in the case of only the inter-vehicle distance control, the deceleration becomes larger as the following vehicle decelerates, whereas in the method of switching between the vehicle speed control and the inter-vehicle distance control as in this embodiment, all the vehicles are almost the same. It becomes a deceleration pattern, and it is possible to realize smoother vehicle behavior with less discomfort.

【0039】

As described above, according to the above-described embodiment, it is possible to prevent the phenomenon that the vehicle speed fluctuation of the preceding vehicle is amplified and propagated to the rear vehicle at the point where the gradient changes. As a result, it is possible to reduce the occurrence of traffic congestion in the sag section and the feeling of strangeness in the conventional inter-vehicle distance control.

[Simple explanation of drawings]

[Figure 1]

It is a figure which shows the equipment arrangement to the vehicle of one Embodiment.

[Figure 2]

It is a figure which shows the structure of one Embodiment.

[Fig. 3]

It is a flowchart which shows the preceding vehicle follow-up control program.

[Fig. 4]

It is a flowchart which shows the control target determination routine.

[Fig. 5]

It is a figure which shows the setting example of the target vehicle speed.

[Fig. 6]

It is a figure explaining the setting example of the inter-vehicle distance allowance when changing from a flat road to a slope road.

[Fig. 7]

It is a figure for demonstrating the method of switching the control rule from vehicle speed control to inter-vehicle distance control.

[Fig. 8]

It is a figure which shows the simulation result of the speed change of each vehicle when a group of 5 vehicles enters an uphill road when traveling only by the conventional inter-vehicle distance control.

[Fig. 9]

It is a figure which shows the simulation result of the speed change of each vehicle when a group of 5 vehicles enters an uphill road when traveling by the method of switching between vehicle speed control and inter-vehicle distance control.

[Explanation of symbols]

1 Inter-vehicle distance sensor 2 Vehicle speed sensor 3 Gradient road detector 4 Driving control controller 4a Target driving force calculation unit 4b Gradient resistance estimation unit 4c Control target generator 4d actuator command value calculation unit 5 Throttle valve actuator 6 engine 7 transmission 8 Brake actuator