JP2018114917A - Cruise control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the best drive performance to be always obtained without giving the acceleration insufficient feeling and the uncomfortable feeling due to the fluctuation in the engine speed to a driver when following up the preceding vehicle.SOLUTION: A constant revolution speed calculation unit 15 sets the constant revolution speed Nec necessary for allowing the own vehicle 1 to travel at the constant speed to follow up a preceding vehicle P. A target revolution speed calculation unit 16 sets the target revolution speed Neo necessary for accelerating the own vehicle 1 following acceleration of the preceding vehicle P. A time constant calculation unit 18 sets the time constant T of the primary delay on the basis of the revolution difference between the target revolution speed Neo and the constant revolution speed Nec. A filter processing unit 19 sets the instruction revolution speed Net to be instructed to engine control means by performing filter processing on the target revolution speed Neo with the transfer function of the time constant T.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a cruise control device that controls the engine speed in accordance with the traveling state of a preceding vehicle during traveling by auto cruise control (ACC) that follows the preceding vehicle.

  Generally, in this type of cruise control device, the target torque of the engine and the input of the automatic transmission according to the difference (speed difference) between the vehicle speed (set vehicle speed) set by the driver and the vehicle speed (vehicle speed) of the host vehicle. The target rotational speed of the shaft is set for each calculation cycle, and thereby the own vehicle speed is controlled to converge to the target vehicle speed set based on the set vehicle speed.

  In addition, when the vehicle is running under cruise control, when it reaches a road surface with a large traveling load such as an uphill road and the vehicle speed decreases, the cruise control device uses the throttle valve opening in engine control so that the host vehicle speed can immediately reach the target vehicle speed. Is increased to increase the engine output, while in the shift control, the gear ratio is downshifted to increase the torque, thereby accelerating the vehicle to prevent the vehicle speed from dropping.

  In this case, in a vehicle equipped with an engine with a relatively large displacement (hereinafter referred to as a “high displacement vehicle”), the throttle valve is opened to increase the engine torque even when the traveling load increases. The vehicle speed can be converged relatively easily to the target vehicle speed without greatly shifting down the gear ratio of the automatic transmission.

  On the other hand, a vehicle equipped with a low displacement engine (hereinafter referred to as a “low displacement vehicle”) has a high traveling load such as high altitude traveling, uphill traveling, high speed traveling, and high vehicle weight. When trying to obtain acceleration performance equivalent to both of the above-mentioned high displacements, naturally, it is necessary to increase the engine speed and to greatly downshift the gear ratio. However, such acceleration operation increases vibration and noise and deteriorates the ride comfort.

  Therefore, in the case of Patent Document 1 (Japanese Patent Application Laid-Open No. 2015-189286), the present applicant suppresses a rapid increase in the engine speed even when the traveling load increases during traveling by cruise control. A technology to reduce discomfort for the driver was proposed.

Japanese Patent Laying-Open No. 2015-189286

  However, in the technique disclosed in the above-described document, since the target acceleration is uniformly controlled according to the traveling load, the preceding vehicle accelerates in a state where the vehicle travels uphill following the preceding vehicle. Even so, there is a problem that the host vehicle cannot be followed with good responsiveness and the driver is given a feeling of insufficient acceleration.

  As a countermeasure, if the follow-up response to the preceding vehicle is increased, the engine speed is increased when the preceding vehicle is traveling at a constant speed and the driving load increases and the distance from the preceding vehicle increases. In addition, the transmission is downshifted. However, the engine speed frequently fluctuates during constant speed travel, which may cause inconvenience to the driver.

  In view of the above circumstances, the present invention always provides the best driving performance without causing the driver to feel underaccelerated or uncomfortable regardless of the driving conditions of the preceding vehicle when following the preceding vehicle. An object is to provide a cruise control device that can be obtained.

  The present invention provides a cruise control device for driving a host vehicle following a preceding vehicle, a driving load calculating means for setting a driving load of the host vehicle, and driving the host vehicle following the acceleration of the preceding vehicle. A target rotational speed calculation means for setting a target rotational speed necessary for accelerating against the vehicle and necessary for causing the host vehicle to follow the vehicle at a constant speed against the traveling load with respect to the preceding vehicle. A constant speed rotational speed calculating means for setting a constant speed rotational speed, a time constant calculating means for setting a time constant of a first-order delay based on a rotational difference between the target rotational speed and the constant speed rotational speed, and the target rotational speed. Filter processing means for setting an instruction rotational speed to be instructed to the engine control means by performing filtering with the time constant transfer function.

  According to the present invention, the target rotational speed necessary for accelerating the host vehicle following the acceleration of the preceding vehicle and the constant speed rotational speed necessary for causing the host vehicle to follow the preceding vehicle at a constant speed. Is set, and the time constant of the first-order lag is set based on the rotation difference. The target rotation speed is filtered by the transfer function based on this time constant, and the instruction rotation speed for instructing the engine control means is set. When the host vehicle is following the preceding vehicle and the driving load increases, if the vehicle is following at a constant speed, the rapid increase in engine speed is suppressed. When the vehicle accelerates, it can follow with good responsiveness.

  Therefore, in the follow-up traveling at a constant speed, the driver does not feel uncomfortable due to the increase in the engine speed, and when the preceding vehicle accelerates, the engine speed can be increased to immediately follow the driver. Therefore, the driver is not given a lack of acceleration. As a result, the best driving performance can always be obtained regardless of the traveling conditions of the preceding vehicle.

Schematic diagram of a vehicle equipped with a vehicle control unit traveling on an uphill road Overall configuration diagram of the vehicle control unit Functional block diagram of the engine speed control unit provided in the cruise control device Conceptual diagram of shift line map Conceptual diagram of primary delay time constant setting table

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Reference numeral 1 in FIG. 1 denotes a vehicle (own vehicle), which is a four-wheel drive vehicle driven by the left and right front wheels 1a and the left and right rear wheels 1b, or a two-wheel drive vehicle driven by only the left and right front wheels 1a or only the left and right rear wheels 1b. .

  The host vehicle 1 is provided with an in-vehicle camera 2 that captures an image of the traveling environment around the host vehicle 1. In this embodiment, a stereo camera having a main camera 2a and a sub camera 2b is adopted as the in-vehicle camera 2. Both the cameras 2a and 2b are fixed to the upper part of the front part of the vehicle interior (for example, both sides of the rearview mirror) with a certain distance therebetween. An image signal of the traveling environment in front of the host vehicle captured by both the cameras 2a and 2b is transmitted to the image processing unit (IPU) 3.

  Based on the image information from the in-vehicle camera 2, the IPU 3 obtains the driving environment information around and around the host vehicle 1. Then, based on the traveling environment information, the preceding vehicle P traveling forward of the host vehicle 1 is recognized, and the recognized various information is transmitted to the ACC control unit (ACC_ECU) 11 described later.

  The host vehicle 1 is equipped with an engine 5, and an automatic transmission 6 is connected to the engine 5. This automatic transmission 6 is a continuously variable transmission (CVT) in this embodiment, and the output shaft of this automatic transmission 6 is a drive wheel (if it is a four-wheel drive vehicle, left and right front wheels 1a and left and right rear wheels 1b). It is connected to.

  The rotational speed of the engine 5 is controlled by an engine control unit (E / G_ECU) 21, and the gear ratio of the automatic transmission 6 is controlled by a transmission control unit (T / M_ECU) 22. Each of these control units 11, 21, 22 is mainly composed of a well-known microcomputer equipped with a CPU, ROM, RAM, etc. The ROM has control programs and various tables for realizing preset operations. Fixed data is stored. The control units 11, 21, and 22 are connected via a vehicle communication line 23 such as CAN (Controller Area Network) communication so that bidirectional communication is possible.

  Further, as shown in FIG. 2, on the input side of the ACC_ECU 11, in addition to the IPU 3, a wheel speed sensor 7 for detecting the rotational speed of the drive wheel, the longitudinal acceleration of the host vehicle 1, and the longitudinal inclination angle of the vehicle body are detected. A G (acceleration) sensor 8 is connected.

  The ACC_ECU 11 starts the ACC control when the driver operates a cruise control switch (not shown) during driving to set a desired constant speed vehicle speed, and whether the preceding vehicle P is captured based on the traveling environment information acquired by the IPU 3. If it is determined that the vehicle has been captured, the relative vehicle speed with respect to the preceding vehicle P and the preceding vehicle information such as the inter-vehicle distance are read, and the target vehicle speed for causing the host vehicle 1 to follow the preceding vehicle P is set. If the preceding vehicle P is not captured, the constant vehicle speed (set vehicle speed) set by the driver is set as the target vehicle speed.

  Then, the target rotational speed of the engine 5 corresponding to the target vehicle speed is obtained, and this is subjected to a predetermined filtering process to set an instruction rotational speed Net instructed to the E / G_ECU 21. Further, the T / M_ECU 22 sets the instruction rotational speed Net as the target input shaft rotational speed, and based on the target input shaft rotational speed and the target vehicle speed, an automatic transmission (CVT) that converges the current vehicle speed to the target vehicle speed. ) Set the gear ratio of 6.

  Further, as shown in FIG. 3, the ACC_ECU 11 functions as a function of setting the command rotational speed Net as a gradient estimated value calculation unit 12, a target vehicle speed calculation unit 13, an estimated vehicle weight calculation unit 14, and a constant speed rotation number calculation unit. A constant speed rotation number calculation unit 15, a target rotation number calculation unit 16 as a target rotation number calculation unit, a differentiator 17, a time constant calculation unit 18 as a time constant calculation unit, and a filter processing unit 19 as a filter processing unit are provided. It has been.

  The estimated gradient value calculation unit 12 sets the road gradient value based on the front and rear G information detected by the front and rear G sensor 8 when the host vehicle 1 is stopped. While traveling, the wheel speed of the drive wheel detected by each wheel speed sensor 7 is time-differentiated from the front and rear G information to obtain the wheel acceleration, and the average value is subtracted (corrected) from the front and rear G information to obtain the acceleration component. Remove and estimate the road slope value.

  In addition, when the preceding vehicle P is captured, the target vehicle speed calculation unit 13 sets a target vehicle speed that causes the host vehicle 1 to follow the preceding vehicle P from the relative vehicle speed with respect to the preceding vehicle P, the inter-vehicle distance, and the like. When the preceding vehicle P is not captured, the set vehicle speed set by the driver is set as the target vehicle speed.

  Further, the estimated vehicle weight calculation unit 14 estimates the current vehicle body weight (vehicle weight) such as a state in which an occupant is on board and a state in which luggage is loaded from the traveling state of the host vehicle 1. For example, the estimated vehicle weight is estimated by first estimating the expected value of the vehicle body acceleration from the axial torque (= tire torque) of the drive wheel, and time-differentiating the wheel speed of the drive wheel detected by each wheel speed sensor 7. The acceleration is obtained and averaged to calculate the actual vehicle acceleration. In addition, a vehicle weight meter may be attached to the vehicle body, and the vehicle weight when the vehicle is stopped may be directly measured.

  Then, the amount of increase in the vehicle body is obtained from the ratio of the expected vehicle body acceleration obtained from the shaft torque and the actual vehicle body acceleration obtained from the wheel speed, and the vehicle body weight set in advance is corrected by this vehicle body increase amount. Estimate the weight (actual vehicle weight). The shaft torque is obtained based on, for example, a vehicle model that models characteristics from engine torque calculated based on the intake air amount or throttle opening and fuel injection amount or vehicle speed to the torsional angular velocity of the drive shaft.

  The constant speed rotational speed calculation unit 15 calculates an engine rotational speed (constant speed rotational speed) Nec necessary for running at a constant speed under a certain load. That is, the traveling load is calculated based on the road surface gradient value calculated by the gradient estimated value calculation unit 12, the target vehicle speed calculated by the target vehicle speed calculation unit 13, and the estimated vehicle weight obtained by the estimated vehicle weight calculation unit 14. Each of the calculation units 12 to 14 corresponds to the traveling load calculation means of the present invention.

  Then, a torque (traveling load torque) necessary for traveling the host vehicle 1 against the traveling load is calculated, and the engine speed (constant speed) at which the traveling load torque and the vehicle body acceleration become 0 (constant speed). The number of revolutions (Nec) is calculated with reference to a shift line map as shown in FIG. The transmission map shown in the figure is exemplified by a continuously variable transmission, and the low speed side transmission line LOW at which the speed ratio (target primary rotational speed≈target rotational speed) is maximized, and the speed ratio is The throttle opening is set in a region surrounded by the minimum high-speed shift line OD. Then, based on the set constant speed rotational speed (target primary rotational speed in the figure) and the vehicle speed, a throttle opening degree that keeps the engine rotational speed constant is determined.

  On the other hand, the target rotational speed calculation unit 16 calculates an engine rotational speed (target rotational speed) Neo necessary for accelerating from a certain load. That is, first, similarly to the above-described constant speed rotation speed calculation unit 15, the traveling load is calculated based on the road surface gradient value, the target vehicle speed, and the estimated vehicle weight. Further, the ACC target acceleration is set based on the difference between the target vehicle speed and the own vehicle speed and the road surface gradient value, the difference between the target vehicle speed and the own vehicle speed, and the difference between the inter-vehicle distance from the preceding vehicle P and the target inter-vehicle distance.

  Next, the ACC target acceleration is multiplied by the vehicle amount, various running resistances are added to the ACC target acceleration, and then the torque conversion coefficient is multiplied to calculate the engine torque that realizes the ACC target acceleration. Then, a throttle opening for generating the engine torque is set, and a necessary engine speed (target speed) Neo is referred to the shift line map shown in FIG. 4 based on the throttle opening and the vehicle speed. Is calculated.

  The subtractor 17 subtracts the constant speed rotational speed Nec obtained by the constant speed rotational speed computing section 15 from the target rotational speed Neo obtained by the target rotational speed computing section 16 to calculate a rotational difference (Neo−Nec). The time constant calculation unit 18 refers to the time constant table shown in FIG. 5 and sets the time constant T of the first-order lag according to the rotation difference (Neo-Nec). This time constant table is set to a characteristic that decreases (shortens) the time constant T in an inverse proportion as the rotation difference (Neo-Nec) increases. Accordingly, when the host vehicle 1 is traveling at a constant speed following the preceding vehicle P, the target rotational speed Neo and the constant speed rotational speed Nec are substantially the same, and thus extended (in the figure, 100 [%]). A time constant T is set. On the other hand, when the preceding vehicle P accelerates and the host vehicle 1 tries to follow it, the target rotational speed Neo increases, and therefore when the vehicle gradually decreases with the increase (approaching the 0% side in the figure) A constant T is set.

The filter processing unit 19 performs a filter process on the target rotational speed Neo obtained by the target rotational speed calculating unit 16 using a transfer function of the first-order lag time constant T obtained by the time constant calculating unit 18, and calculates the designated rotational speed Net. To do.
Net ← Neo / (1 + T ・ s)
Here, s is a Laplace operator. The indicated rotational speed Net obtained by filtering the target rotational speed Neo with a first-order lag time constant T is a relatively slow response when the preceding vehicle P follows at a constant speed. In addition, when trying to follow the acceleration of the preceding vehicle P, quick response is obtained.

  The command rotational speed Net obtained by the ACC_ECU 11 is transmitted to the E / G_ECU 21 to perform engine control for feedback control of the throttle opening and the like so that the engine rotational speed becomes the command rotational speed Net. On the other hand, the T / M_ECU 22 performs shift control for setting a gear ratio according to the throttle opening and the vehicle speed by referring to a gear ratio map (not shown).

  As described above, in the present embodiment, when the preceding vehicle P is traveling following at a constant speed by the ACC control, the constant speed rotation speed Nec set by the constant speed rotation speed calculation section 15 and the target rotation speed calculation section 16 are used. Since a large difference does not occur with the set target rotational speed Neo, the time constant calculation unit 18 sets a large first-order lag time constant T. As a result, the command rotational speed Net set by temporarily delaying the target rotational speed Neo in the filter processing unit 19 is slowed down, and the responsiveness is slow. Even when traveling under conditions where a large traveling load is generated, such as high-speed traveling at high speeds such as high vehicle weight loaded with a lot of luggage, the engine speed does not increase rapidly due to the increase in load, The discomfort given to the driver can be reduced.

  On the other hand, when the preceding vehicle P accelerates, the target rotational speed Neo set by the target rotational speed calculation unit 16 becomes larger than the constant speed rotational speed Nec set by the constant speed rotational speed calculation unit 15, and therefore the time constant. In the calculation unit 18, a small first-order lag time constant T is set. As a result, the indicated rotational speed Net set by the temporary delay filter processing in the filter processing unit 19 becomes faster in response, and causes the driver to feel a sense of rattling or insufficient acceleration due to an increase in the engine rotational speed. And good acceleration performance can be obtained.

  As a result, according to the present embodiment, when the preceding vehicle P follows the preceding vehicle P, when the preceding vehicle P is traveling at a constant speed, a rapid increase in the engine speed is suppressed, while the preceding vehicle P is accelerated. In such a case, the engine speed can be immediately increased to follow, and this is particularly effective in a small displacement vehicle, and can always exhibit the best driving performance.

  The present invention is not limited to the above-described embodiment. For example, the means for recognizing the preceding vehicle P can detect preceding vehicle information such as the inter-vehicle distance from the preceding vehicle and the relative vehicle speed. For example, not only the in-vehicle camera 2 but also a combination of a monocular camera and a distance sensor (such as a millimeter wave radar, a sound wave radar, or a laser radar) may be used.

1 ... own vehicle,
1a ... front left and right wheels,
1b ... left and right rear wheels,
2… In-vehicle camera
2a ... main camera,
2b ... Sub camera,
5 ... Engine,
6 ... Automatic transmission,
7: Wheel speed sensor,
8: Front and rear G sensor,
12 ... gradient estimated value calculation unit,
13 ... Target vehicle speed calculation unit,
14 ... Estimated vehicle weight calculation unit,
15 ... Constant speed rotation speed calculation unit,
16 ... target rotation speed calculation unit,
16: Each wheel speed sensor,
16 ... target rotation speed calculation unit,
17 ... differentiator,
18, Time constant calculation unit,
19: Filter processing unit,
23 ... In-car communication line,
Nec: constant speed,
Neo ... Target speed,
Net ... Indicated rotation speed,
P ... preceding car,
T ... Time constant

Claims (3)

In the cruise control device that drives the vehicle following the preceding vehicle,
Traveling load calculation means for setting the traveling load of the host vehicle;
Target rotational speed calculation means for setting a target rotational speed necessary for accelerating the host vehicle against the traveling load following the acceleration of the preceding vehicle;
A constant speed rotational speed calculating means for setting a constant speed rotational speed necessary for causing the host vehicle to follow the traveling load at a constant speed against the traveling load;
Time constant calculating means for setting a time constant of a first-order lag based on the rotation difference between the target rotation speed and the constant speed rotation speed;
A cruise control device comprising: a filter processing means for setting an instruction rotational speed for filtering the target rotational speed with the transfer function of the time constant and instructing the engine control means. The time constant calculating means subtracts the constant speed rotation number from the target rotation number to obtain the rotation difference, and sets the time constant shortened as the rotation difference increases. The cruise control device according to 1. The cruise control device according to claim 1 or 2, wherein the travel load set by the travel load calculating means is set based on at least a road surface gradient value and a vehicle body weight.

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