JP7530936B2 - Energy-saving deceleration driving control method - Google Patents

Description

This invention relates to an energy-saving deceleration control method that efficiently and effectively utilizes the kinetic energy possessed by a vehicle when it decelerates, and that is superior in kinetic energy utilization efficiency to deceleration using regenerative cooperative braking, as well as conventional braking systems (brakes).

When a traveling vehicle decelerates, coasting is the traveling mode that can most effectively utilize the kinetic energy of the vehicle immediately before the vehicle starts to decelerate.
However, coasting does not necessarily result in an efficient use of kinetic energy.
For example, as shown in FIG. 1, if the vehicle coasts from a speed (vc+Δv) to a speed (vc-Δv) (distance d11), and then accelerates from a speed (vc-Δv) to a speed (vc+Δv) (distance d12), the distance traveled during this period d1 (=d11+d12) will consume the same kinetic energy as traveling at a speed vc, that is, the same kinetic energy as traveling at a constant speed at vc, and this will not be energy-saving traveling.
In contrast to this, in the case of traveling in a unit traveling section as shown in FIG. 2, in the case of decelerating traveling at the braking deceleration rate αb from P4 to P6, the distance between P4 and P6 is the traveling distance with kinetic energy Evc, in the case of coasting traveling at the coasting deceleration rate αi from P3 to P5 and in the case of braking traveling at the braking deceleration rate αb from P5 to P6, the distance between P3-P5-P6 is the traveling distance with kinetic energy Evc, and the distance between P3 and P4 is the energy-saving traveling distance by coasting.
In other words, by coasting from the upstream coastable point P3 toward the target deceleration stop point P6 and subsequent braking from the speed vb, energy-saving deceleration is possible by effectively utilizing the kinetic energy Evc = (m· ^vc2 /2) that the vehicle had just before the start of deceleration.
In other words, when a fixed target point for deceleration and stopping (such as an intersection, a slow-down point such as a crosswalk, or an obstacle ahead on the road) is identified, the vehicle's coasting distance that makes maximum use of the vehicle's kinetic energy is calculated, and energy-saving, low-CO2-emission deceleration driving is achieved by coasting from a point within the coasting distance upstream of the target point to the target deceleration and stopping point.

However, when coasting using the above coasting distance,
1) The coasting start point is several hundred meters upstream from the target deceleration/stop point, i.e., the coasting distance becomes excessive.
2) Therefore, the average running speed during this period is significantly lower than the running speed (constant running speed) before the transition to coasting.
3) In order to determine the coasting distance, it is necessary to determine the coasting deceleration of each vehicle at that time, and therefore the running resistance. However, it is practically difficult to obtain this with the required accuracy in advance for each vehicle.
4) Responding to changes in the driving environment such as road conditions after switching to coasting, for example fluctuations in coasting speed due to changes in road gradient.
There are problems such as:

To address the above problems 1) and 2), a method has been devised in which the deceleration and coasting is achieved by efficiently and effectively combining coasting and braking (Patent Document 1, Patent Document 2, Patent Document 3). That is, if the coasting start speed is vc and the coasting end speed is vb, the kinetic energies Ec and Eb of the vehicle at the start and end of coasting (at the start of braking) are expressed by (Equation 1) and (Equation 2), respectively.
(Equation 1)
Ec = m ^vc2 / 2
(Equation 2)
Eb = m vb ² /2
Here, m is the mass of the vehicle (including the passengers). Therefore, the kinetic energy utilization efficiency ηcb between the coasting start speed vc and the coasting end speed vb (of coasting) is
(Equation 3)
ηcb­­= (vc ² - vb ² )/vc ²
The average speed during the coasting is,
vcb≒(vc+vb)/2
It becomes.
Therefore, for example, if v = 60 km/h and v = 30 km/h,
ηcb­­＝0.75
vcb ≒ 45km/h
It can be said that:
That is, it can be seen that by appropriately setting vc and vb, the deceleration running by coasting described above can bring both the kinetic energy utilization efficiency and the average speed during coasting within an allowable range.

However, with regard to the determination of the coasting distance in 3) above, the methods in Patent Documents 1, 2, and 3 all show a method of provisionally setting the coasting distance and learning and correcting it through actual coasting, but all of these methods have the problem that in practical use, the learning and correction and the control based on the results are cumbersome.

On the other hand, in the case of conventional deceleration running in which deceleration is entirely performed by braking, the problem of the long deceleration running distance caused by coasting is eliminated, but the efficiency of kinetic energy utilization is greatly reduced.
Furthermore, even in regenerative braking cooperative driving, in which kinetic energy is regenerated and utilized for subsequent driving, there are problems in that the efficiency of kinetic energy utilization is inferior to that of coasting, for example, because some of the kinetic energy is consumed by the friction braking used in combination, and because the regenerative power generated by regenerative braking cannot be charged efficiently due to insufficient power density characteristics or temperature characteristics of the large-capacity secondary battery used to store the regenerative power.

Patent Publication No. 2013-177126 Patent Publication 2019-034734 Patent No. 6788942

The present invention provides an energy-saving deceleration control method that is primarily based on coasting, which is superior overall to conventional methods that utilize kinetic energy through regenerative cooperative braking, by rationally and simply resolving or mitigating the following major problems with utilizing the kinetic energy of a moving vehicle for deceleration primarily based on coasting: 1) the increased distance required for deceleration, 2) the decrease in average running speed during deceleration as a result of the increased deceleration distance, 3) the complexity of accurately identifying and controlling the coasting deceleration rate, and 4) changes in the running environment during coasting.

Here, coasting refers to traveling with the transmission of the vehicle drive source power to the drive wheels cut off or reduced. (However, the vehicle drive source power does not necessarily have to be stopped. For example, in a gasoline engine vehicle, it is not necessarily necessary to stop the engine, i.e., to cut off the fuel. Even if the engine is kept in an idling state, a corresponding energy saving effect can be obtained by reducing the fuel consumption during coasting.)
Furthermore, even if the transmission of the vehicle drive source power to the drive wheels is not completely cut off (i.e., the clutch is not disengaged), for example, by using a form in which the accelerator off state in MT 4th gear is used as a "pseudo coasting" state in which the transmission of the vehicle drive source power to the drive wheels is sparse, a corresponding energy saving effect can be obtained.

The basic concept of the present invention will be described below with reference to FIG.
In FIG. 3, a straight line P4-P6 indicates a braking deceleration straight line at a braking deceleration rate αb from point P4 to point P6 of a vehicle traveling at a constant speed vcmax.
That is, a vehicle traveling at a constant speed vcmax normally travels at the constant speed up to point P4, and then brakes from point P4 toward a stop point P6 at a braking deceleration rate αb. As a result, the kinetic energy of the vehicle at the speed vcmax is entirely consumed during braking between points P4 and P6, and the utilization effect of the vehicle's kinetic energy during this period for vehicle travel, i.e., the travel distance, is only the distance between points P4 and P6.
In contrast, in the energy-saving deceleration traveling mode of the present invention, a vehicle traveling within the permissible coasting transition speed range, i.e., the speed range from vcmin to vcmax, transitions from a normal traveling state (accelerating traveling or constant speed traveling) to coasting (for deceleration) at point P3, a certain distance dr upstream from point P6.
In addition, after the transition to coasting, the upstream distance of point P6 on the line P4-P6 where the coasting at speed v transitions to braking is
(Equation 5)
d=v2 ^/ (2・αb)
It becomes.

A vehicle that has passed point P3 and is coasting within the coasting transition speed range of speed vcmin to speed vcmax will coast at speeds above vcmin, and after reaching speed vcmin will coast at a constant speed at speed vcmin until it reaches the braking start line P4-P6, as shown in FIG. 3, and thereafter will brake at a braking deceleration rate αb until it reaches the target deceleration/stop point P6.
Here, point P45 is the point where coasting reaches the initial braking start straight line P4-P6 from the upper limit value vcmax of the coasting transition speed. If the speed at this point is v, then the distance d between point P45 and point P6, d = v2 ^/ (2·αb), is the braking distance.
Further, the distance between point P5 and point P6 is the braking distance from the speed vcmin to the speed 0, that is, db= vcmin ² /(2·αb) .
Furthermore, a vehicle that passes through point P3 at a speed less than vcmin continues to travel at a constant speed, maintaining the speed at which it passed through point P3, until it reaches the braking and deceleration straight line P4-P6.

Furthermore, after transitioning from normal running to coasting at the coasting transition speed vc at point P3, if the coasting speed becomes equal to or exceeds the coasting transition speed vc for some reason (for example, the road gradient), coasting is stopped and the vehicle transitions to normal running, continuing to run at the speed vc up to the braking-running transition point (distance db = { ^vc2 / (2 · αb)} from the target deceleration and stop point), and thereafter the vehicle reaches point P6 while braking at the deceleration speed αb.

Here, from the viewpoint of kinetic energy utilization efficiency, it is desirable that the distance dr between points P3 and P6 is the distance that can be coasted at the speed vcmax. However, as long as the kinetic energy utilization efficiency of decelerated traveling mainly based on coasting at the upper limit value vcmax of the permissible coasting transition speed or the average speed during coasting are both within the permissible range, the distance dr does not necessarily have to be the distance that can be coasted.
That is, problem 3) above does not require learning and correction of the provisional coasting distance through actual traveling every time coasting is performed, and as long as the coasting results from the coasting start point P3 provisionally specified in advance have kinetic energy utilization efficiency and average speed during coasting that fall within the allowable ranges, the coasting start point P3 at speed vcmin to speed vcmax can be set to a point a certain distance dr upstream from point P6.

As a result, with the present invention, it is no longer necessary to accurately determine and control the coasting distance possible when decelerating and mainly coasting, as shown in Patent Documents 1, 2, and 3, in which a provisional coasting distance is set and learning, updating, and control is performed using actual coasting.
In this case, however, as described above, the efficiency of utilizing the kinetic energy due to coasting or the running speed during this time will be sacrificed to some extent within an allowable range.

Illustration of the energy-saving effect of coasting Diagram of the running state of a unit running section A diagram explaining the basic concept of the energy-saving deceleration driving control method according to the present invention. 4 is an example of a processing procedure in an energy-saving deceleration driving control support device according to the present invention.

The energy-saving deceleration driving control method according to the present invention can be realized by partially improving an existing car navigation device having a route search and guidance function.
Specifically, the system needs to have the function of searching for a route to the destination from the starting point, identifying (multiple) unit driving sections from the starting point to the destination from the results, identifying and acquiring position information of the target deceleration/stopping point in each unit driving section, and obtaining distance information between the vehicle's current position and the target deceleration/stopping point from the acquired periodic speed information and position information of the vehicle in each unit driving section, thereby performing the coasting or braking driving assistance.

As described above, the present invention is effective as an energy-saving deceleration driving control method and an assistance device thereof by partially improving the above-mentioned current car navigation system for manually operated vehicles (vehicles driven by a driver) such as current gasoline/diesel vehicles or electric vehicles such as EVs, but it is of course also applicable to autonomous vehicles.

FIG. 4 shows a processing procedure in the energy-saving deceleration driving control method and the support device thereof according to the present invention.
However, this example procedure is limited to the procedures for a vehicle intending to travel within a unit travel section to identify a target deceleration/stopping point, transition to deceleration travel mainly based on coasting, and stop at the target deceleration/stopping point.
In this processing procedure, it is assumed that the coasting transition possible speed range vcmin to vcmax, the coasting start fixed distance dr upstream of the target deceleration and stop point, and the braking deceleration rate αb are set and specified in advance.
Also, during this procedure, vehicle speed and current vehicle position information shall be determined periodically in the background with the required frequency and accuracy.

In FIG.
401 is the start point of this procedure example;
402 is a P6 point specified determination process for determining whether or not the (next) target deceleration/stop point position (P6 point in FIG. 3) of the vehicle has been specified;
403 is a P4 point specification process for specifying the P4 point when it is determined in the process 402 that the target deceleration/stop point (P6 point) has not yet been specified;
404 is a process for identifying a coasting transition point that is a certain distance upstream of point P6;
405 is a process for calculating and specifying a distance d between the current vehicle position and P4;
406 is a coasting transition possibility determination process for determining whether or not to transition to coasting by comparing the distance dr specified in the process 404 with the distance d calculated and specified in the process 405;
407 is a normal running process for performing normal running (accelerated running or constant speed running) when the determination of whether or not to transition to coasting is "no" in the process 406;

408 is a coasting transition speed determination process for determining whether the vehicle speed v is within the coasting transition possible speed range vcmin to vcmax if the coasting transition possible/not possible determination is "possible" in the process 406;
409 is a coasting process for switching to coasting or continuing coasting when it is determined in process 408 that the vehicle speed v is within the coasting transition speed range, i.e., when v=vc;
410 is a v>v determination process for determining whether the vehicle speed exceeds the coasting transition speed v;
411 is a constant speed running transition process for stopping coasting and transitioning to constant speed running at a speed v=v when it is determined in process 410 that the vehicle speed v is v>v;
412 is a braking-running transition possibility determination process for determining whether or not the remaining distance d to the point P6 has become a braking-running transition distance of ^v /(2·α) or less as a result of the process 411;
413 indicates that the distance d to the vehicle's current position P6 is the distance at which braking should be started at the current speed v
a braking start determination process A for determining whether d≦{v ² /(2·α b )} has been reached;
In step 414, similarly to step 413, the distance d from the current vehicle position to P6 is determined to be the distance d at which braking should be started.
Braking start determination process B for determining whether {v ² /(2·α b )} has been reached;
415 is a constant speed running process for running at a constant speed vcmin when it is determined in process 414 that the distance d to the vehicle's current position P6 has not yet reached the distance db at which braking should be started;
416 is a braking running process for performing braking at a deceleration rate αb when it is determined in the process 413 or 414 that the distance d to the vehicle current position P6 has reached the distance db≦{ ^v2 /(2·αb)} at which braking should be started from the current speed v;
417 is a target deceleration/stop point arrival determination process for determining whether or not the distance d from the vehicle current position to P6 has reached d=0, i.e., the target deceleration/stop point position (point P6 in FIG. 3) as a result of the braking run in process 416;
418 is a final destination determination process for determining whether the target deceleration/stop point determined in process 417 is the final destination of the main travel;
419 is a process end point for ending this process if it is determined in process 418 that the final destination has been reached;
It is.

The present invention makes it possible to efficiently and effectively utilize the vehicle's kinetic energy for deceleration based primarily on coasting through simple calculations and control, instead of the regenerative cooperative driving currently used in hybrid or electric vehicles, which is aimed at utilizing kinetic energy during deceleration, and also in gasoline and diesel engine vehicles.
In other words, the present invention enables simple and effective energy-saving, greenhouse gas-reducing deceleration driving that efficiently utilizes kinetic energy in place of conventional braking driving or regenerative braking cooperative driving in any vehicle, regardless of the vehicle's drive mode and whether it is driven automatically or manually.
The present invention can also be implemented by providing the coasting start signal and the braking start signal to the vehicle from the infrastructure side without assistance from a car navigation device.
In addition, in the present invention, near point P5 (end point of coasting) in Figure 3, the driver can detect the traffic signal state of the signalized intersection which is the target deceleration and stopping point ahead of the vehicle, or the presence or absence of pedestrians on the crosswalk, by visual inspection or by using a sensor such as a camera mounted on the vehicle, and when it is confirmed that the traffic signal is green or there are no pedestrians on the crosswalk, the transition from coasting or constant speed traveling to braking traveling can be stopped and the vehicle can continue traveling toward the next deceleration and stopping point after passing through point P6 (target deceleration and stopping point) while maintaining the vehicle traveling speed v at that time.

In Figs. 1 and 2, P1: starting acceleration start point P2: acceleration end point, constant speed running start point P3: coasting start point P4: low speed running end point, braking running start point P5: coasting end point, braking running start point P6: target deceleration stop point, braking running end point d11: coasting distance d12: accelerated running distance d1: (coasting + acceleration running) running distance in one cycle αa: acceleration αb: braking deceleration αi: coasting deceleration In Figs. 3, 4, and (Equation 1) to (Equation 5) ,
P3: Starting point of coasting between vehicle speeds vcmax and vcmin
P34: Coasting start speed vc3 End of coasting/start of constant speed running
P4: Braking start point from vehicle speed vcmax
P45: Coasting start speed vc1 End of coasting /start of braking of the vehicle
P5: End of coasting from coasting start speed vc2/start of braking: Start of braking from vehicle running speed vcmin
P6: Target deceleration/stop point ηcb: Efficiency of kinetic energy utilization by coasting v: Vehicle running speed (including low-speed coasting and braking speeds)
vc: coasting transition (start) speed vc1, vcmax: upper limit (possible) coasting transition speed vc2, vc3: coasting transition permissible (possible) speed vc4, vcmin: lower limit (possible) coasting transition speed vb: braking start speed vcb: average speed during coasting αi: coasting deceleration αb: braking deceleration d: distance between current point and target deceleration stop point dr: coasting start constant distance upstream of target deceleration/stop point db: braking start distance upstream of target deceleration/stop point dbmax = vcmax ² / (2 αb): braking distance from speed vcmax dbmin = vcmin ² / (2 αb): braking distance from speed vcmin

Claims (1)

In a vehicle traveling at a speed v within a preset coasting transition speed range (vcmin to vcmax), coasting is started at a point dr upstream of a target stopping point within a coasting transition distance range at the coasting transition upper limit speed (vcmax), and the vehicle transitions from coasting to braking at a braking transition point with an upstream distance db from the target stopping point of db = ^v2 /(2·αb) to reach the target stopping point;
However, at the point or time when the coasting speed reaches the lower limit speed (vcmin) at which the coasting transition can be made, if the remaining distance d to the target stopping point is d > { ^vcmin2 /(2·αb)}, constant speed traveling will be performed at speed v = vcmin until the remaining distance d reaches d = {vcmin2/( ² ·αb)}. Also, if the vehicle speed v after transitioning to coasting at a coasting transition start speed vc within the coasting transition speed range becomes equal to or greater than vc, the vehicle will transition from coasting to normal traveling while maintaining speed vc until the remaining distance d reaches d = ^vc2 /(2·αb).
2. An energy-saving deceleration driving control method comprising:
where αb: braking deceleration v: vehicle speed after transition to coasting, vcmin≦v≦vcmax
It is.