JPH09150646A - Automatic speed control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a drop of actual car speed in moving from a down-hill at a specific inclination to a flat road surface or to an up-grade. SOLUTION: Car speed control is carried out by judging it as a down-hill at a specific incline at the time when throttle opening TVO causes hunting in the neighborhood of total closing, by changing car speed feedback control gain used by a car speed feedback control means 24 over to specific control gain lowered than ordinary control gain by a specific inclination control changeover means 33, by returning the car speed feedback control gain to the ordinary control gain at the time when a deviation of current car speed VSP detected by a car speed deviation detection means 31 and a car speed command value VSPr becomes larger than a specified value by a gain selection means 35 while it is detected to be the down-hill at the specific incline and by changing it over to the specific control gain when the car speed deviation becomes smaller than the specified value. Thereafter a specific inclination finish judgement means 34 judges that a road surface of the down-hill at the specific incline is finished in accordance with a specified vehicle state and returns it to the ordinary control gain.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic vehicle speed control device for automatically controlling the speed of a vehicle so that it runs at a constant target speed.

[0002]

2. Description of the Related Art Generally, an automatic vehicle speed control device attempts to keep a certain vehicle speed, for example, 80 km / h, on a road such as a highway which can travel a long distance at a constant speed. It is a function used for, by turning on the constant speed traveling set switch,
Unless the driver changes the vehicle speed by depressing the brake pedal or the accelerator pedal, the vehicle automatically adjusts the throttle opening by increasing or decreasing the vehicle speed while keeping the current speed and seeing the deviation between the actual vehicle speed and the target vehicle speed. A device for controlling acceleration / deceleration.

As such a vehicle automatic speed control device, a device described in Japanese Patent Application Laid-Open No. 64-12933 is conventionally known. This first conventional vehicle automatic speed control device switches the vehicle speed feedback control gain to a small value to perform constant speed traveling control when the throttle opening is close to full closure, and then sets the vehicle speed and the vehicle speed. When the deviation between and becomes larger than a predetermined value, the original control gain is restored.

As another second conventional example, Japanese Patent Laid-Open No. 2-16
The automatic speed control device for a vehicle described in Japanese Patent No. 834 is known, but in this example, the gain of the vehicle speed feedback control is lowered during the fuel cut operation.

[0005]

However, these conventional examples have the following problems. Generally, the fuel cut is performed when the throttle is fully closed and the engine speed is equal to or higher than a predetermined value. However, a relatively large step difference occurs in the drive torque during execution and non-execution of the fuel cut. Therefore, when a strong feedback control is applied to match the actual vehicle speed with the set vehicle speed on a downhill where the driving force and the running resistance are balanced near the throttle fully closed, hunting occurs near the throttle fully closed, which causes the vehicle speed to decrease. Affects and deteriorates ride comfort.

Therefore, in both the above-mentioned first and second conventional examples,
The purpose is to avoid or reduce the fuel cut hunting that occurs in constant speed running control on a downhill.However, in these conventional examples, the vehicle speed feedback control gain is set to a small value so as to reduce the fuel cut hunting. Since it is switched to, it becomes easier to be affected by changes (disturbance) such as road gradients during that time.
For example, when the road gradient changes from a downhill to an uphill, a large vehicle speed deviation may occur.

In this respect, in the first conventional example, the vehicle speed deviation is compared with a predetermined value and returned to the normal gain, but generally, the vehicle speed hunting cycle is long while the downhill is controlled to run at a constant speed with a low gain. However, since the amplitude becomes large, if the specified value is set too small, it will be mistakenly judged that the gradient causing fuel cut hunting has ended and the gain will immediately return to the normal value. There is a problem that the drop in vehicle speed when turning uphill becomes extremely large.

This point will be described with reference to FIGS. FIG. 12 shows changes in the vehicle speed when the vehicle speed feedback control is performed with a constant gain. In FIG. 12, it is assumed that the road gradient changes from a flat road surface to a downhill slope at point A, a downhill slope to an uphill slope at point B, and a climbing slope to a flat road surface at point C.

Between the point A and the point B, the running resistance corresponds to a step between the driving force at the fuel cut-on and the driving force at the fuel cut-off, so that the set vehicle speed VSPr is maintained. Throttle hunting that repeatedly opens and closes near the fully closed throttle (= 0 °) is caused, which also affects the vehicle speed VSP and causes hunting near the set vehicle speed VSPr. If the gain of the vehicle speed feedback control is set high in order to reduce the influence of disturbance such as gradient change, the vehicle speed hunting cycle becomes shorter,
The riding comfort deteriorates.

In FIG. 13, the road slope changes from a flat road surface to a down slope at a point A, returns to the flat road surface at a point B, then immediately changes to a down slope, and at a point D, changes from a down slope to an up slope. Then, it is assumed that the point E moves to a flat road surface. Then, as in the first conventional example, the throttle opening TVO
Is close to fully closed (= 0 °), the vehicle speed feedback control gain is switched to a small value (Low) to perform constant speed travel control, and then the deviation between the set vehicle speed VSPr and the vehicle speed VSP is a predetermined threshold. If it becomes larger than the value, control to return to the original control gain (Hi) is performed.

If the vehicle speed feedback control gain is switched to Low by detecting the fuel cut on the down slope, the vehicle speed hunting period becomes longer, but on the other hand, the set vehicle speed VSPr
The change (that is, the amplitude) of the actual vehicle speed VSP with respect to is large. Therefore, if the threshold value of the vehicle speed deviation is set to a large value so that it is not mistakenly judged that the downhill of the specific gradient such as the fuel cut hunting has ended, when the downhill is changed to the uphill like point D. It causes a big undershoot.

If the threshold value of the vehicle speed deviation is made small in order to avoid this, the vehicle speed feedback is erroneously judged to have ended when the vehicle speed deviation at the point B becomes large and fuel cut hunting occurs. Since the control gain is returned to the normal value, the hunting cycle becomes shorter until the fuel cut is detected in the descending gradient immediately after the point B, and there is a problem that hunting of the vehicle speed occurs and the riding comfort deteriorates.

In the second conventional example, when the throttle opening, which is the reference for operating / not operating the fuel cut, exceeds the predetermined value, the gain is returned to the normal gain (Hi), but the low gain (Low)
Since the throttle responsiveness to changes in road gradients (disturbances) is slow while the vehicle is running at a constant speed on the downhill, the throttle speed changes as shown in the behavior of the vehicle speed VSP near point D in Fig. 13. When the opening TVO reaches a predetermined value indicating that the vehicle has descended from the downhill, there is a problem that a large decrease in vehicle speed may already occur.

The present invention has been made in view of such conventional problems, and it is possible to effectively suppress fuel cut hunting on a downhill of a specific slope, and if the road surface of the downhill of a specific slope is completed. An object of the present invention is to provide an automatic vehicle speed control device capable of continuing constant speed traveling control without causing a large drop in vehicle speed.

[0015]

According to a first aspect of the present invention, there is provided a vehicle automatic speed control device comprising: a current vehicle speed detecting means for detecting a current vehicle speed; and a vehicle speed command value setting means for setting an arbitrary vehicle speed command value. A throttle opening detecting means for detecting a throttle opening; a vehicle speed deviation detecting means for detecting a deviation between the current speed and the vehicle speed command value; and the vehicle speed so that the current speed follows the vehicle speed command value. Vehicle speed feedback control means for controlling the vehicle speed by controlling the throttle opening based on the deviation detected by the deviation detecting means, and determining that the throttle opening is a downhill with a specific slope when hunting occurs near full closure Specific gradient determining means to
A specific gradient control switching means for switching the vehicle speed feedback control gain in the vehicle speed feedback control means to a special control gain lower than the normal control gain when the specific gradient determination means detects that the vehicle is on a downhill of a specific gradient; A specific gradient end determination means for determining that the downhill road surface of the specific gradient has ended based on the vehicle state,
While the specific gradient determination means detects that the vehicle is on a downhill of a specific gradient, the feedback control gain used in the vehicle speed feedback control means is normally controlled according to the magnitude of the deviation detected by the vehicle speed deviation detection means. A gain selecting means for switching between the gain and the special control gain is provided.

In the vehicle automatic speed control device according to the first aspect of the present invention, the specific gradient determining means determines that the vehicle is downhill with a specific gradient when hunting occurs when the throttle opening is close to the fully closed state, and the specific gradient of this specific gradient is determined. When it is detected that the vehicle is downhill, the specific gradient control switching means switches the vehicle speed feedback control gain used by the vehicle speed feedback control means to a special control gain which is lower than the normal control gain, and the specific gradient determination means further descends the specific gradient. While detecting that the vehicle is on a slope, the gain selection means controls the control gain used by the vehicle speed feedback control means when the deviation between the current vehicle speed detected by the vehicle speed deviation detection means and the vehicle speed command value becomes larger than a predetermined value. Return to the normal control gain, and if the vehicle speed deviation becomes smaller than the predetermined value again, switch to the special control gain to change the vehicle speed. To perform the control. When the specific gradient end determination means determines that the downhill road surface of the specific gradient has ended based on the predetermined vehicle state, the normal vehicle speed control by the normal control gain is restored.

This suppresses the occurrence of fuel cut hunting on the downhill of the specific slope, and controls the vehicle speed by the normal control gain without causing a large drop in the vehicle speed at the end of the road surface of the downhill of the specific slope. Can be moved to.

According to a second aspect of the present invention, in the vehicle automatic speed control device according to the first aspect, the specific gradient end determining means determines that the deviation between the current vehicle speed detected by the vehicle speed deviation detecting means and the vehicle speed command value exceeds a predetermined value. It is characterized in that it is determined that the road surface of the downhill of the specific slope has ended when the road is turned on.

Normally, when the road surface on a downhill with a specific slope is completed, the running resistance increases and the current vehicle speed decreases and starts to deviate from the vehicle speed command value. However, in the vehicle automatic speed control device according to the invention of claim 2, When the deviation exceeds a predetermined value, the specific gradient end determination means determines that the downhill road surface of the specific gradient has ended, so that it is possible to accurately determine that the downhill road surface of the specific gradient has ended. Thus, it is possible to shift to normal vehicle speed control without a large drop in vehicle speed.

According to a third aspect of the present invention, in the vehicle automatic speed control device according to the first aspect, the specific gradient end determination means is:
Running resistance estimating means for estimating running resistance applied to the vehicle,
And a traveling resistance storage means for storing the traveling resistance obtained by the traveling resistance estimating means when the specific gradient determining means determines that the vehicle is a downhill with a specific gradient. Is compared with the current estimated value of running resistance, and when the difference between them is equal to or more than a predetermined value, it is determined that the road surface of the downhill of the specific slope has ended.

Normally, the running resistance increases when the road surface on the downhill of the specific gradient ends, but in the vehicle automatic speed control device according to the invention of claim 3, the specific gradient end determination means travels on the downhill of the specific gradient. The running resistance estimated value of the vehicle inside is compared with the running resistance estimated value immediately after entering the downhill of the specific slope, and if the deviation exceeds a predetermined value, it is determined that the road surface of the downhill of the specific slope has ended. It is possible to accurately determine that the road surface on the downhill of the specific slope has ended, and it is possible to shift to normal vehicle speed control without a large drop in vehicle speed.

According to a fourth aspect of the present invention, in the vehicle automatic speed control device according to any one of the first to third aspects, further, after the specific gradient end determination means determines that the downhill road surface of the specific gradient has finished. A special vehicle speed control transition means for setting the vehicle speed feedback control gain used by the vehicle speed feedback control means to a value larger than a normal control gain until the deviation detected by the vehicle speed deviation detection means falls within a predetermined value. It is a thing.

In the vehicle automatic speed control device according to the invention of claim 4, when the road surface on the downhill of the specific slope is finished, the vehicle speed feedback control gain is made larger than the normal gain to enhance the responsiveness and quickly The vehicle speed can be controlled to match the vehicle speed command value, and constant-speed running control can be performed without a large drop in vehicle speed.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a hardware configuration of one embodiment of the present invention. A constant speed traveling control unit 1 includes a microcomputer 1a including a CPU, a RAM, a ROM, a digital port, an A / D port and various timers. As the main part, the automatic speed control calculation according to the present invention is executed according to various programs to control the operation of various devices. The constant speed traveling control unit 1 also includes a throttle actuator drive circuit 1b.

A main switch (MAIN_SW) as a power switch for the constant speed traveling control unit 1
, A constant speed traveling set switch (SET _SW) for instructing the start of constant speed traveling control, an accelerator switch (ACC _SW) for giving an acceleration command for the current speed, and a coast switch (for giving a deceleration command for the current speed). COAST _SW),
A switch group 2 including a cancel switch (CANCEL_SW) for canceling the constant speed traveling control and a brake switch (BRAKE _SW) for detecting that the brake pedal is depressed, and a vehicle speed sensor 3 using a reed switch.
The potentiometer-type throttle opening sensor 4 and the crank angle sensor 5 for measuring the engine rotation speed are connected as elements that provide input signals. A throttle actuator 6 is connected as a control target by the constant speed traveling control unit 1.

In the vehicle speed sensor 3, the contact of the reed switch is opened and closed by the rotation of the permanent magnet connected to the speedometer cable, and a pulse signal corresponding to the actual vehicle speed is output to the control unit 1 and the control unit 1
The actual vehicle speed VSP is measured by pulse counting at. The throttle opening sensor 4 outputs an analog signal corresponding to the actual throttle opening to the control unit 1, and the control unit 1 performs A / D conversion to convert the actual throttle opening.
Measure TVO.

The throttle actuator 6 is of a negative pressure type and is provided with a vacuum pump 7 driven by a motor, an atmosphere opening solenoid valve 8 and a safety valve 9, and a PW output from the control unit 1.
Pump 7 and solenoid valve 8 with duty ratio of M signal
Is controlled to open and close the throttle 10. The safety valve 9 is for opening the throttle opening to the atmosphere so that the control system does not drive the throttle when the automatic speed control mode is not set, and for fully closing the throttle opening. The unit 1 controls its opening and closing.

The automatic speed control function executed by the constant speed traveling control unit 1 has the structure shown in FIGS. 2 and 3.
When the set switch is operated, the current speed VSP is changed to the target vehicle speed.
The target vehicle speed setting unit 21 that sets the target vehicle speed VSPr to drive at a constant speed with VSPr, the vehicle speed detection unit 22 that detects the current actual vehicle speed VSP based on the signal from the vehicle speed sensor 3, and the throttle opening sensor 4 are used. The opening of the throttle 10 based on the signal
The throttle opening detector 23 for detecting TVO is provided.

A target driving force calculation unit 24 for calculating a target driving force y4 based on a predetermined calculation method described later with respect to the target vehicle speed VSPr set by the target vehicle speed setting unit 21 and an actual vehicle speed.
Estimated running resistance x based on VSP and final target driving force y1
And a target driving force correction unit 26 that corrects the target driving force based on the target driving force y4 and the estimated running resistance value x to output the final target driving force y1. The throttle opening required to output the final target driving force y1 from the force correction unit 26, that is, the target throttle opening
A target throttle opening calculation unit 27 that calculates TVOr and a throttle opening control unit 2 that performs feedback control to match the actual throttle opening TVO with the target throttle opening TVOr.
8. And, as a characteristic part of the present invention, a control gain adjusting unit 29 is provided for performing switching control of the vehicle speed control gain on a downhill of a specific gradient.

The vehicle speed control gain adjusting unit 29 has the functional configuration shown in FIG. 3, and the target vehicle speed from the target vehicle speed setting unit 21 is set.
The vehicle speed deviation detection unit 31 that detects a deviation between the VSPr and the current actual vehicle speed VSP from the vehicle speed detection unit 22 and the behavior of the throttle opening TVO detected by the throttle opening detection unit 23 indicate that the vehicle is going down a specific slope. A specific gradient determining unit 32 that determines whether or not the vehicle is traveling on a slope, and when the specific gradient determining unit 32 determines that the vehicle is traveling downhill with a specific gradient, the vehicle speed feedback control gain used by the target driving force calculation unit 24 is normally set. Based on the running resistance estimated value obtained from the running resistance estimating unit 25 and the running resistance estimating unit 25 that sets a special control gain lower than the control gain, it is determined whether or not the road surface on the downhill of the particular slope has ended. Specific slope end determination unit 3
4 and the specific gradient determining unit 32 determines that the vehicle is traveling on a downhill with a specific gradient, the vehicle speed feedback control gain is normally controlled according to the magnitude of the deviation detected by the vehicle speed deviation detecting unit 31. The control gain switching determination unit 35 that switches between the gain and the special control gain, and the normal control gain setting unit 36 that sets the normal control gain.

The vehicle automatic speed control device having the above-described structure operates as follows. The target vehicle speed setting unit 21 indicates the current speed VSP at the time when the driver operates the set switch, or when the automatic speed control is in progress, the acceleration operation by the accelerator switch is completed, or the deceleration operation by the coast switch is completed. Set as target vehicle speed VSPr.

The target driving force calculation unit 24 calculates the target vehicle speed VSPr set by the target vehicle speed setting unit 21 with respect to the vehicle speed detection unit 22.
The target driving force is calculated based on a predetermined calculation method described later by using the control gain provided from the control gain adjusting unit 29.

The running resistance estimating unit 25 calculates a running resistance estimated value based on the actual vehicle speed VSP and the target driving force from the target driving force calculating unit 24. The target driving force correction unit 26 corrects the target driving force based on the target driving force from the target driving force calculation unit 24 and the running resistance estimated value from the running resistance estimation unit 25, and outputs the final target driving force.

The target throttle opening calculation unit 27 calculates the throttle opening required to output the final target driving force from the target driving force correction unit 26, that is, the target throttle opening TVOr. Then, the throttle opening control unit 28 compares the target throttle opening TVO r from the target throttle opening calculation unit 27 with the actual throttle opening TVO from the throttle opening detection unit 23, and sets the actual throttle opening TVO to the target throttle opening TVO. Feedback control is performed to match the opening degree TVOr, and automatic speed control is performed so that the actual vehicle speed VSP finally matches the target vehicle speed VSPr.

In this automatic speed control, the control gain adjusting section 29 performs automatic switching control of the vehicle speed control gain on a downhill of a specific gradient to suppress fuel cut hunting. Therefore, first, the vehicle speed deviation detection unit 31 detects the deviation between the target vehicle speed VSPr from the target vehicle speed setting unit 21 and the current actual vehicle speed VSP from the vehicle speed detection unit 22, and the specific gradient determination unit 32 detects the throttle opening. Based on the behavior of the throttle opening TVO detected by the unit 23, it is determined whether or not the vehicle is traveling on a downhill with a specific slope.

Then, the specific gradient control gain setting section 33
When the specific gradient determining unit 32 determines that the vehicle is descending a specific gradient, the vehicle speed feedback control gain is set to a special control gain that is lower than the normal control gain, and the target driving force calculating unit 24 is provided with the special control gain. Along with this, the specific gradient end determination unit 34
Determines whether or not the road surface on the downhill of the specific slope has ended, based on the estimated running resistance value obtained from the running resistance estimation unit 25.

Therefore, the control gain switching determination unit 35 determines the magnitude of the deviation detected by the vehicle speed deviation detection unit 31 while the specific slope determination unit 32 determines that the vehicle is traveling on a downhill of the specific slope. The vehicle speed feedback control gain is switched between the special control gain set by the specific gradient control gain setting unit 33 and the normal control gain set by the normal control gain setting unit 36 and given to the target driving force calculation unit 24 according to It suppresses fuel cut hunting on downhill slopes and responds quickly to changes in road slope to prevent the vehicle speed from dropping.

A specific method of automatic speed control processing according to the above embodiment will be described with reference to the flowcharts of FIGS. This automatic speed control process is repeatedly executed at predetermined time intervals, for example, every 50 msec control cycle by a timer interrupt or the like. First, control cycle 50
The average actual speed VSP and the average engine speed Ne are calculated using the count values of the pulse signals of the vehicle speed sensor 3 and the crank angle sensor 5 counted in msec, and the analog signal of the throttle opening sensor 4 is converted into A / D. The actual throttle opening TVO is measured by conversion (step P
1).

Until then, the automatic speed control (ASCD) mode has been used, and it is judged whether or not this has been canceled by the operation of the cancel switch or the operation of the brake switch this time (step P2), and the cancel switch or the brake switch is turned on. If so, all flags and variables are initialized and the automatic speed control mode is canceled (step P16). However, if neither the cancel switch nor the brake switch is turned on, it is next determined whether or not a new set operation in the automatic speed control mode has been performed by operating the set switch (step P3).

If the set switch is newly operated in this control cycle, the average actual speed measured this time
Since the driver instructs the vehicle to run at a constant speed in VSP, set this actual speed VSP to the target speed VSPr (step P4), set the automatic speed control flag, and start automatic speed control from the next time. Prepare (step P5).

In the subsequent control cycles, the automatic speed control is repeated until the cancel switch is operated or the brake is depressed to turn on the brake switch. That is, based on the actual vehicle speed VSP, the actual throttle opening TVO, and the engine speed Ne at the beginning of each control cycle measured in step P1, the throttle opening control is performed so that the actual speed matches the target speed VSPr. (Steps P1 to P3, P6 to P15).

When the automatic speed control is started, first, a processing routine for determining the occurrence / end of fuel cut (F / C) hunting is executed (step P7), and then step P
8 to P12, the final target driving force y1 of the engine is calculated using the compensation calculation circuit 40 shown in FIG. 9 that uses the model matching method and the approximate zeroing method which are widely known linear control methods.

First, the F / C hunting occurrence / end determination processing will be described with reference to FIGS. If this processing routine is entered, first, the state of the flag indicating whether or not fuel cut (F / C) hunting is in progress is checked (step P21). If the F / C hunting flag is set, it is determined that the fuel cut hunting is in progress, and step P
If the flag is cleared after moving to the processing of 41 or later,
Next, the flag (LOWGAIN flag) indicating that the gain of the vehicle speed feedback control is set to a small value is cleared (step P22).

Subsequently, the state of the flag (HIGH GAIN flag) indicating that the gain of the vehicle speed feedback control is set to a large value is checked (step P23). If the HIGHGAIN flag is set, the magnitude of the vehicle speed deviation is determined to determine whether the gain of the vehicle speed feedback control is returned to the normal value, and the vehicle speed deviation is the first reference deviation Δth1 (= 0.5
If the vehicle speed deviation is larger than 0.5 km / h, the gain of the vehicle speed feedback control is maintained at a large value if the vehicle speed deviation is larger than 0.5 km / h (step P2).
4, P25).

Subsequently, the flag (throttle OPEN flag) indicating whether or not the throttle is opened is checked (step P26), and if set, the throttle opening TVO is smaller than the first reference opening (= 0.88 °). It is determined whether it is larger or smaller (step P27), and if the throttle OPEN flag is cleared, the throttle opening TVO is the second reference opening (=
It is determined whether it is larger or smaller than 1.32 ° (step P33).

In step P27, if the throttle opening TVO is smaller than the first reference opening, the process proceeds to step P34 and thereafter to perform the processing during throttle fully closing, and if it is larger than the first reference opening, the throttle is fully closed. In order to perform processing other than medium, proceed to step P28 and open the throttle.
Set a flag. Further, when the throttle opening TVO is 1.32 ° or more in step P33, the process proceeds to step P28 in order to perform the processing other than the fully closing of the throttle, and the throttle OPEN flag is set.

Next, looking at the timer (throttle CLOSE timer) for measuring the time when the throttle is closed, the throttle is longer than the first reference time (= 1 sec) and within the second reference time (= 10 sec). If so, it is determined that fuel cut hunting has occurred, the running resistance estimated value at the time of fuel cut hunting + a predetermined value is stored in the running resistance storage unit 34a, and the F / C hunting flag is set (step P29, After that, the throttle CLOSE timer is cleared and the process returns to the main routine (step P32).

In step P29, the throttle CLOS
If the E timer is not between the first reference value and the second reference value,
Increment the throttle OPEN timer (step P
31), then the throttle CLOSE timer is cleared and the process returns to the main routine (steps P31 and P32).

When the throttle OPEN flag is set and the throttle opening TVO is the first reference value (= 0.88 °) or more, the throttle OPEN flag is cleared,
And the throttle opening TVO is the second reference value (= 1.32 °)
In the above case, proceed to Step P34 to perform the process of fully closing the throttle, first clear the throttle OPEN flag, look at the timer (throttle OPEN timer) that measures the time the throttle was open, and check this throttle OPEN timer. Throttle CLOS if the timer is equal to or greater than the first reference value (= 1 sec) and is within the second reference value (= 10 sec)
The E timer is incremented and the process returns to the main routine (steps P35 and P36).

If the judgment in step P35 is made, the throttle is opened.
If the timer is not between the first reference value and the second reference value, the throttle OPEN timer is cleared and the process returns to the main routine (step P37).

If the fuel cut hunting is already detected in the F / C hunting occurrence / end determination processing routine (step P21), the process proceeds to step P41 to set the gain of the vehicle speed feedback control to a small value. It is determined whether the flag (LOWGAIN flag) indicating is set.

Fuel cut hunting is detected,
If the LOW GAIN flag is also set (step P
21, P41), and then the vehicle speed deviation is set to the second value in order to determine whether to return the gain of the vehicle speed feedback control to the normal value.
Compare with standard deviation Δth2 (= 1km / h) (step P4
2) If the vehicle speed deviation is greater than or equal to the second reference deviation Δth2, LO is set to return the vehicle speed feedback control gain to the normal value.
The WGAIN flag is cleared (step P43).

On the other hand, when the occurrence of fuel cut hunting is detected for the first time, or when fuel cut hunting occurs, the gain of the vehicle speed feedback control is once reduced to a gain smaller than the normal value and then returned to the normal value again. If so, in step P41
Since the LOWGAIN flag has been cleared, step P4
4, the vehicle speed deviation is set to the third reference deviation Δth3 (= 0.72).
(km / h), if the vehicle speed deviation is small, use LOWG to reduce the gain of vehicle speed feedback control.
The AIN flag is set, and if the vehicle speed deviation is not small, the original gain is maintained (steps P44 and P45).

Thereafter, the running resistance estimated value at the present time is compared with the stored value of the running resistance estimated value at the time of fuel cut hunting. If the current running resistance estimated value is larger, fuel cut hunting may occur. It is judged that the vehicle has exited a certain slope downhill, the F / C hunting flag is cleared, a flag (HIGHGAIN flag) for changing the gain of the vehicle speed feedback control to a large value is set, and the process returns to the main routine (step. P46, P4
9).

However, if the current running resistance estimated value is less than or equal to the stored running resistance estimated value when fuel cut hunting occurs, the vehicle speed deviation is checked and the fourth reference deviation Δth is determined.
If it exceeds 4 (= 1.5 km / h), it is determined that the vehicle has escaped the downhill of the specific slope, the F / C hunting flag is cleared, and the flag for changing the gain of the vehicle speed feedback control to a large value (HIGHGAIN Set a flag and return to the main routine (steps P47, P48, P4).
9). In other cases, the process directly returns to the main routine (steps P47 and P48).

Thus, F / in step P7 in FIG.
When the C hunting occurrence / end determination processing routine is finished, the vehicle speed control processing subsequent to step P8 is executed by using the gain of the vehicle speed feedback control which is set and switched here.

In the automatic speed control, in order to match the actual vehicle speed VSP to the target vehicle speed VSPr, the final target driving force y1 is calculated by using the model matching method and the approximate zeroing method which are widely known linear control methods. To do.

First, the outline of the compensator will be described using a pulse transfer function. The transfer characteristic of the controlled object is defined by the pulse transfer function P
If (z ⁻¹ ) is set, the compensator 40 has the configuration shown in FIG. 9. z is a delay operator and is multiplied by z ^-1 to obtain a value one control cycle before. C1 (z ^-1 ), C2 (z ^-1 )
Corresponds to the running resistance estimator 25, which executes the disturbance estimation calculation by the approximate zeroing method to suppress the influence of the disturbance and modeling error. Also C3 (z ^-1 )
Is a model matching compensating unit that executes compensation calculation by the model matching method, and has a reference model H having a first-order delay and a dead time which are predetermined response characteristics of the controlled object.
Match the characteristics of (z ^-1 ).

Assuming that the part for inputting the target driving force VSPr and outputting the actual vehicle speed VSP is a control target, P (z ^-1 ) is the following equation 1
Integral element P1 (z ^-1 ) and dead time element P2 (z ^-1 ) shown in the equation
= Z ^-2 .

(Equation 1) Here, T: control cycle (here, set to 50 msec) M: average vehicle weight

At this time, C1 (z ^-1 ) and C2 (z ^-1 ) are expressed by the following equations 2 and 3.

(Equation 2) (Low-pass filter with time constant Tb)

(Equation 3) Where γ = exp (-T / Tb)

If the reference model H (z ^-1 ) is a first-order low-pass filter with a time constant Ta, ignoring the dead time of the controlled object, C3 of the model matching compensator becomes a constant of the following equation (4).

(Equation 4)

Based on the above control method, in step P8 in the flowchart of FIG. 4, the following equation 5 corresponding to the model matching compensating unit is calculated to obtain the target driving force y4.

[Formula 5] y4 (k) = K · (VSPr (k) -VSP (k))

In the next step P9, the operation of the following equation (6) corresponding to the robust compensator C2 (z ^-1 ) which is a part of the running resistance estimating section is performed. However, the data y (k-1) indicates the data of the (k-1) control cycle immediately before the k control cycle.

(Equation 6)

Next, the following equation 7 for correcting the target driving force by the estimated running resistance value x is executed to obtain the final target driving force.
y1 is obtained (step P10).

## EQU00007 ## y1 (k) = y4 (k) + (y2 (k-2) -y3 (k))

Here, y2 (k-2) is the step P12 described later.
3 shows the data obtained two control cycles before y2 (k) obtained by the calculation corresponding to the low-pass filter unit C1 (z- ¹ ) of (2), that is, (k-2) control cycles.

Further, y2 (k-2) is a driving force which is not affected by the running resistance obtained in the compensator, whereas y3 (k) is a value obtained by subtracting the running resistance from the driving force. Therefore, the equation y2 (k-2) -y3 (k) in the parentheses in the above equation becomes the running resistance estimated value x.

Next, the upper limit of the target driving force is limited (step P11). For that purpose, first, the maximum engine torque Termax and the minimum engine torque Termin are obtained by using the table data in which the engine torque values at the time when the throttle is fully opened and when the throttle is fully closed are stored for each engine rotation speed. Furthermore, using the following formula 8, maximum driving force Fmax and minimum driving force Fm
Find in. However, in the following equation, Gm is the transmission gear ratio, Gf
Is the final gear ratio and Rt is the effective radius of the tire.

(Equation 8)

Then, the final target driving force y1 (k) is limited by the upper limit value Fmax and the lower limit value Fmin to obtain y5 (k).

After performing the upper limit value limiting process of the target driving force in this way, the calculation of the following equation 9 corresponding to the compensator C1 (z ^-1 ) as a low-pass filter which is a part of the running resistance estimation unit is executed. (Step P12).

[Formula 9] y2 (k) = γ · y2 (k-1) + (1−γ) · y5 (k-1) In the subsequent step P13, the target throttle opening degree calculation unit 2
A target throttle opening degree calculation corresponding to the processing of 7 is executed. For this, the final target driving force y1 (k)
Calculate the target engine torque Ter from

(Equation 10) Further, the target throttle opening TVOr is calculated from the target engine torque Ter using the data map of the engine nonlinear characteristic as shown in FIG.

Then, in the throttle opening control unit 28, the actual throttle opening TVO is compared with the target throttle opening TVOr.
Control to match. That is, the output pulse to the vacuum pump 7 and the vent valve 8 of the negative pressure type throttle actuator 6 is output based on the deviation between the target throttle opening TVOr and the actual throttle opening TVO by a widely known feedback control method such as PID control. The width is calculated (step P14). As the obtained result, the vacuum pump output pulse width Tvac and the vent valve output pulse width Tvent are written in the pulse output register of the microcomputer 1a (step P15).

The characteristics of the vehicle speed control as described above will be described with reference to FIG. Now, the road slope shifts from a flat road surface to a down slope at point A, shifts from a down slope to an up slope at point C, immediately shifts to a down slope at point D, and further shifts to a up slope at point E. Suppose

When the throttle opening hunting occurs once within a predetermined time after passing the point A on such a road gradient, the F / C hunting flag is set at the point B at which the throttle opening hunting is detected. The running resistance estimated value is stored as a downhill equivalent memory value MR.

After that, the vehicle speed deviation is the third at point B '.
LOWGAI when the deviation is within the standard deviation Δth3 (= 0.72km / h)
Set the N flag to switch the vehicle speed feedback control gain to a smaller value. According to the embodiment of the present invention, the switching of the control gain is realized by switching the time constant of the low pass filter of the robust compensator in the compensator 40 of FIG. 10 to a larger value. By switching the control gain to a small value, the stability margin is increased, the hunting cycle is lengthened, the vehicle speed hunting is suppressed, and the riding comfort is improved.

At point C, when the vehicle speed deviation exceeds the second reference deviation Δth2 (= 1 km / h) due to the gradient change, F
The / C hunting flag is not cleared and only the LOWGAIN flag is cleared to return the vehicle speed feedback control gain to the normal value. Then, at point D, the vehicle immediately shifts to the downward slope again, and when the vehicle speed deviation returns to within the third reference deviation Δth3, the vehicle speed feedback control gain is switched to a small value again. When the vehicle further goes up to the ascending grade at the point E, the running resistance estimated value increases due to the change in the grade, and the difference from the downhill equivalent stored value MR reaches a predetermined value or more, or the vehicle speed deviation becomes the fourth reference deviation Δth4. When it is judged that the downhill of a specific gradient that causes fuel cut hunting is finished when it exceeds, the HIGHGAIN flag is set and the vehicle speed feedback control gain is switched to a gain larger than the normal value to improve the response characteristic and Make it possible to eliminate the drop quickly. According to the embodiment of the present invention, the switching of the control gain is realized by switching the time constant of the low pass filter of the robust compensator in the compensator 40 of FIG. 10 to a smaller value.

After that, if the vehicle speed deviation becomes smaller than the first reference deviation Δth1 (= 0.5 km / h) at the point F, the vehicle speed feedback control gain is returned to the normal value and the normal vehicle speed feedback control is returned.

[0076]

As described above, according to the first and second aspects of the present invention, it is determined that the slope is a downhill of a specific slope when hunting occurs when the throttle opening is near full closure, and the downhill of this specific slope is determined. When it is detected that the vehicle is on a slope, the vehicle speed feedback control gain used by the vehicle speed feedback control means is switched to a special control gain that is lower than the normal control gain, and while the vehicle is detecting that it is a downhill with a specific slope, When the deviation between the vehicle speed and the vehicle speed command value becomes larger than a predetermined value, the vehicle speed feedback control gain is returned to the normal control gain, and when the vehicle speed deviation becomes smaller than the predetermined value again, the vehicle speed control is performed by switching to the special control gain. Therefore, it suppresses the occurrence of fuel cut hunting on a downhill of a specific slope, and quickly increases the vehicle speed command value if the vehicle speed deviation becomes large on the specific slope. It can be speed controlled so matched, to improve the riding comfort by suppressing hunting in the vehicle speed, and accurate constant speed running can be maintained.

Further, since the specific gradient end judging means judges that the road surface of the downhill of the specific slope has ended when the deviation between the current vehicle speed and the vehicle speed command value exceeds a predetermined value, the road surface of the downhill of the specific slope ends. It is possible to accurately determine what has been done, and it is possible to shift to normal vehicle speed control without a large drop in vehicle speed.

According to the third aspect of the present invention, the running resistance estimated value obtained by the running resistance estimating means when it is determined that the vehicle is on a downhill of a particular gradient is stored, and the particular gradient end judging means estimates the running resistance. The stored value value is compared with the current running resistance estimated value obtained by the running resistance estimating means, and when the difference between these values exceeds a predetermined value, it is determined that the road surface on the downhill of the specific slope has ended. It is possible to accurately determine that the downhill road surface has ended, and it is possible to shift to normal vehicle speed control without a large drop in vehicle speed.

According to the fourth aspect of the present invention, after the specific gradient end determining means determines that the road surface on the downhill of the specific gradient is completed, the deviation between the actual vehicle speed and the vehicle speed command value is within a predetermined value. During this period, the vehicle speed feedback control gain is set to a value that is larger than the normal control gain, so that the response of the vehicle speed feedback control can be improved, and the current vehicle speed can be controlled to quickly match the vehicle speed command value. Even on a large road surface, constant speed running control can be performed without a large drop in vehicle speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a hardware configuration of one embodiment of the present invention.

FIG. 2 is a functional block diagram of automatic speed control executed by a microcomputer in the above embodiment.

FIG. 3 is a functional block diagram of a control gain adjustment unit in the above embodiment.

FIG. 4 is a flowchart of an automatic speed control process executed by the microcomputer in the above embodiment.

FIG. 5 is a flowchart of a first part of an F / C hunting occurrence / end determination processing routine in the above automatic speed control processing.

FIG. 6 is a flowchart of a second part of an F / C hunting occurrence / end determination processing routine in the above automatic speed control processing.

FIG. 7 is a flowchart of a third part of an F / C hunting occurrence / end determination processing routine in the above automatic speed control processing.

FIG. 8 is a flowchart of a fourth part of an F / C hunting occurrence / end determination processing routine in the above automatic speed control processing.

FIG. 9 is a block diagram of automatic speed control executed by the microcomputer in the above embodiment.

FIG. 10 is an engine non-linear characteristic data map used for the target throttle opening degree calculation in the above embodiment.

FIG. 11 is a timing chart showing the automatic speed control characteristic in the above embodiment.

FIG. 12 is a timing chart of a conventional automatic speed control characteristic.

FIG. 13 is a timing chart of another conventional automatic speed control characteristic.

[Explanation of symbols]

 1 Control Unit 1a Microcomputer 1b Drive Circuit 2 Switch Group 3 Vehicle Speed Sensor 4 Throttle Opening Sensor 5 Crank Angle Sensor 6 Throttle Actuator 7 Vacuum Pump 8 Vent Valve 9 Safety Valve 10 Throttle 21 Target Vehicle Speed Setting Section 22 Vehicle Speed Detection Section 23 Throttle Open Degree detection unit 24 target driving force calculation unit 25 traveling resistance estimation unit 26 target driving force correction unit 27 target throttle opening calculation unit 28 throttle opening control unit 29 control gain adjustment unit 31 vehicle speed deviation detection unit 32 specific gradient determination unit 33 specific Gradient control gain setting unit 34 Specific gradient end determination unit 34a Running resistance storage unit 35 Control gain switching determination unit 36 Normal control gain setting unit 40 Compensator

Claims (4)

[Claims] 1. A current vehicle speed detecting means for detecting a current vehicle speed, a vehicle speed command value setting means for setting an arbitrary vehicle speed command value, a throttle opening detecting means for detecting a throttle opening, and the current speed Vehicle speed deviation detection means for detecting a deviation from the vehicle speed command value, and by controlling the throttle opening based on the deviation detected by the vehicle speed deviation detection means so that the current speed follows the vehicle speed command value. Vehicle speed feedback control means for performing vehicle speed control, specific slope determination means for determining that the vehicle is a downhill with a specific slope when hunting occurs when the throttle opening is near full closure, and the specific slope determination means has a specific slope for downhill Is detected, the special speed control gain in which the vehicle speed feedback control gain in the vehicle speed feedback control means is lowered below the normal control gain. Specific gradient control switching means, a specific gradient end determination means for determining that the road surface of the downhill of the specific gradient has ended based on a predetermined vehicle state, and the specific gradient determination means for downhill of the specific gradient. Gain selection for switching the feedback control gain used for the vehicle speed feedback control means between the normal control gain and the special control gain according to the magnitude of the deviation detected by the vehicle speed deviation detection means while detecting the existence And an automatic speed control device for a vehicle. 2. The vehicle automatic speed control device according to claim 1, wherein when the deviation detected by the vehicle speed deviation detection means is greater than a predetermined value, the specific gradient end determination means has a downward slope road surface of the specific gradient. An automatic speed control device for a vehicle, characterized in that it is determined that the above has ended. 3. The vehicle automatic speed control device according to claim 1, wherein the specific gradient end determination means estimates the traveling resistance applied to the vehicle, and the specific gradient determination means descends a specific gradient. A running resistance storing unit that stores the running resistance estimated value obtained by the running resistance estimating unit when it is determined to be a slope, and the running resistance stored value and the current running resistance estimated value obtained by the running resistance estimating unit. The automatic speed control device for a vehicle according to claim 1, characterized in that when the difference between them is equal to or larger than a predetermined value, it is determined that the road surface on the downhill of the specific slope has ended. 4. The vehicle automatic speed control device according to claim 1, wherein the vehicle speed deviation is detected after the specific slope end determination means determines that the road surface on the downhill of the specific slope has ended. Until the deviation detected by the means falls within a predetermined value, the vehicle automatic feedback control means for setting the vehicle speed feedback control gain used by the vehicle speed feedback control means to a value larger than a normal control gain Speed control device.