JPH11321387A - Vehicle speed control device of vehicle with continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably control the vehicle speed even in the state where the engine torque is saturated in an uphill road or downhill road by changing the time contact of a filter processing applied to the target driving force and actual vehicle speed by a disturbance estimating means, when the saturated state of the engine torque is detected by an engine torque saturation detecting means. SOLUTION: A disturbance estimating device can precisely estimate a disturbance such as traveling resistance on the basis of the difference between the output of a model to be controlled and the output of an actual subject to be controlled. The cutoff frequency (time constant) of a low pass filter in a compensator is set according to saturation or non-saturation of engine torque. The engine torque of an engine 10 can be regulated by controlling the intake air by a throttle actuator, the fuel injection by an injector and the ignition timing by an ignition plug. The change gear ratio of a belt type continuously variable transmission 11 can be regulated in non-stage by varying the radiuses of a primary pulley and a secondary pulley by a hydraulic mechanism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling the running speed of a vehicle, and more particularly to an apparatus for controlling the speed of a vehicle with a continuously variable transmission.

[0002]

2. Description of the Related Art A vehicle to be controlled having a target driving force as an input and an actual vehicle speed as an output is represented by a mathematical model in the form of a product of an integral element and a dead time element. There is known a vehicle speed control device that calculates the actual driving force back from the speed, subtracts the actual driving force from the target driving force, estimates disturbance such as running resistance, and corrects the next target driving force based on the estimated disturbance value. (For example, see Japanese Unexamined Patent Application Publication No.
No. 19). In this apparatus, a target driving force and an actual driving force are subjected to a low-pass filter process to obtain a disturbance estimation value.

For a vehicle with a continuously variable transmission, a combination capable of achieving optimum fuel efficiency is calculated from combinations of an engine torque and a gear ratio for achieving a driving force necessary for maintaining a target vehicle speed. A control algorithm for controlling an engine and a continuously variable transmission has been proposed (for example, Journal of the Society of Automotive Engineers of Japan, vol. 48, No. 10, 1994).
According to this control algorithm, the output of the engine is obtained based on the target driving force and the vehicle speed, and the optimal fuel efficiency driving line and the equal output line for the engine speed and the engine torque are determined on a predetermined engine steady characteristic map. The intersection determines the engine speed and the engine torque, and also determines the gear ratio of the continuously variable transmission.

However, according to the latter control algorithm, the drive shaft torque is controlled by obtaining the engine torque and the gear ratio from the engine steady characteristic map, and the transient characteristics of the engine are not considered at all. Therefore, in a situation where the engine torque is already saturated, for example, when traveling at a constant speed on a steep uphill or downhill road, the drive shaft torque is achieved by the gear ratio, and the transient characteristic of the drive shaft torque is It depends on the transient characteristics of the gear ratio. Since the transient characteristics of the speed ratio are slower than the transient characteristics of the engine, the delay of the actual drive shaft torque with respect to the target drive shaft torque becomes large when traveling at a constant speed on an uphill or downhill.

FIGS. 8 and 9 are diagrams showing changes in actual values with respect to command values of a driving force (drive shaft torque), an engine torque and a gear ratio when the continuously variable transmission is downshifted during acceleration. FIG. 8 shows the characteristics when the engine torque is not saturated, and FIG. 9 shows the characteristics when the engine torque is already saturated. If the continuously variable transmission is downshifted during acceleration, an apparent torque (inert torque) is generated due to a change in the equivalent inertia on the engine side, and the rise of the drive shaft torque is delayed, resulting in insufficient acceleration force during gear shifting. In such a case, even if a correction value for the inertia torque is added to the engine torque command value in order to cancel the influence of the inertia torque, there is no effect because the engine torque is already saturated.

On the other hand, the former vehicle speed control system is based on a stepped transmission, and the vehicle speed control system (vehicle model) assumes that the delay of the drive shaft torque is only the engine delay.
Is designed. For this reason, when the delay of the drive shaft torque becomes significantly larger than the value assumed when designing the control system, there is a problem that the stability margin in the vehicle speed control system is lost and vehicle speed hunting occurs.

An object of the present invention is to stably control the vehicle speed even when the engine torque is saturated on an uphill road or a downhill road.

[0008]

(1) A vehicle speed setting means for setting a target vehicle speed, a vehicle speed detecting means for detecting an actual vehicle speed, and a target for making the actual vehicle speed coincide with the target vehicle speed. A disturbance for estimating a disturbance applied to the vehicle by the target driving force and the actual vehicle speed by using a driving force calculating means for calculating a driving force and a mathematical model of a controlled object having the target driving force as an operation amount and the actual vehicle speed as a control amount. Estimating means, driving force correcting means for correcting a target driving force by a disturbance estimated value, engine control command value calculating means for calculating a target engine torque and a target engine rotation speed for achieving the target driving force correction value,
A continuously variable transmission having an engine torque control means for controlling the engine torque according to the target engine torque, and a speed ratio control means for controlling the speed ratio of the continuously variable transmission so that the engine rotation speed matches the target engine rotation speed. It is applied to a vehicle speed control device of a vehicle with a transmission. An engine torque saturation detecting means for detecting a saturated state of the engine torque is provided. When the engine torque saturation detecting means detects the saturated state of the engine torque, the disturbance estimating means performs a filtering process on the target driving force and the actual vehicle speed. The above object is achieved by changing the time constant of. (2) The vehicle speed control device for a vehicle with a continuously variable transmission according to claim 2 increases the time constant of the low-pass filter to lower the cutoff frequency when the disturbance estimating means detects the saturation state of the engine torque. It was made.

[0009]

According to the present invention, the vehicle speed can be controlled stably even when the gear ratio is changed while the engine torque is saturated on an uphill road or a downhill road.

[0010]

FIG. 1 is a diagram showing the configuration of an embodiment. The vehicle speed controller A controls the vehicle speed, and the engine torque controller B controls the torque of the engine 10. The speed ratio controller C controls the speed ratio of the belt-type continuously variable transmission 11. The controllers A, B, and C each include a microcomputer and a communication circuit, and obtain a target drive shaft torque for achieving a target vehicle speed while communicating with each other. Step transmission 11
Control the transmission gear ratio.

A set switch 1, an accelerate switch 2, a coast switch 3, a cancel switch 4, a brake switch 5, a crank angle sensor 6, and the like are connected to the vehicle speed controller A. Set switch 1
Is a switch for setting the current vehicle speed to the target vehicle speed and starting vehicle speed control. The accelerate switch 2 is a switch for increasing the set vehicle speed, and the coast switch 3 is a switch for decreasing the set vehicle speed. The cancel switch 4 is a switch for releasing the cruise control, and the brake switch 5 is a switch that is activated when the foot brake is operated. This brake switch 5
Is activated, the constant-speed traveling control is released in the same manner as when the cancel switch 4 is operated. The crank angle sensor 6 outputs a pulse train signal having a cycle corresponding to the engine speed. The vehicle speed controller A detects the rotation speed of the engine 10 by measuring the period and the number of pulses of a pulse train signal from the crank angle sensor 6.

A vehicle speed sensor 7, an accelerator sensor 8, and the like are connected to the engine torque controller B. The vehicle speed sensor 7 is attached to an output shaft of the continuously variable transmission 11 and outputs a pulse train signal having a cycle according to the vehicle speed. The engine controller B detects the vehicle speed (output shaft rotation speed) by measuring the period and the number of pulses of the pulse train signal from the vehicle speed sensor 7. The accelerator sensor 8 is a potentiometer-type sensor, and detects the amount of depression of an accelerator pedal as the acceleration intention of the occupant.

The gear ratio controller C is connected to a primary rotational speed sensor 9 in addition to the vehicle speed sensor 7 and the accelerator sensor 8 described above. The primary rotation speed sensor 9 detects a rotation speed of a primary pulley of the belt-type continuously variable transmission 11.

The engine 10 can adjust engine torque by controlling intake air by a throttle actuator, fuel injection by an injector, and ignition timing by a spark plug. The belt-type continuously variable transmission 11 can continuously adjust the speed ratio by changing the radius of the primary pulley and the secondary pulley by a hydraulic mechanism.

FIG. 2 is a flowchart showing the vehicle speed control of the vehicle speed controller A. The operation of the embodiment will be described with reference to this flowchart. The vehicle speed controller A executes this control program at a predetermined cycle, for example, every 10 ms. In step 1, the actual vehicle speed is determined from the reciprocal of the vehicle speed pulse width (n cycle) measured by the input capture function of the microcomputer. In the following step 2, the operation of the cancel switch 4 and the brake switch 5 is confirmed, and when any of the switches is operated to be in the ON state, the vehicle speed control ASCD
Is determined to have been cancelled, and the process proceeds to step 6; otherwise, the process proceeds to step 3. In step 6, ASC
With the cancellation of D, various flags and variables are initialized, and the process ends.

On the other hand, if the ASCD has not been canceled, the operation of the set switch 1 is confirmed in step 3. When the set switch 1 is operated and in the ON state,
It is determined that the occupant has the intention to set the target vehicle speed Vspr, and the process proceeds to step 4; otherwise, the process proceeds to step 7. In step 4, the current vehicle speed Vsp is set as the target vehicle speed Vspr,
In a succeeding step 5, the ASCD operation flag is set and the processing is ended.

If there is no operation for canceling the ASCD and no operation for setting the target vehicle speed Vspr, the ASCD operation flag is checked in step 7, and if it is set, it is determined that the vehicle speed is being controlled (ASCD operation is being performed). Proceed to step 8, otherwise proceed to step 6. In step 6, various flags and variables are initialized as described above, and the process ends.

If the ASCD is in operation, the operation of the accelerator switch 2 is confirmed in step S8. When the accelerator switch 2 is in the ON state, the acceleration control mode is determined, and the vehicle is accelerated by adding a predetermined value ΔV to the current target vehicle speed Vspr. Then, the acceleration switch 2 is turned off.
The actual vehicle speed Vsp immediately after the state is set to the target vehicle speed Vspr. In a succeeding step 9, the operation of the coast switch 3 is confirmed. When the coast switch 3 is in the ON state, it is determined that the vehicle is in the deceleration mode, and the predetermined value ΔV
Is subtracted to decelerate the vehicle. Then, the actual vehicle speed Vsp immediately after the coast switch 3 is turned off is set to the target vehicle speed Vspr.
Set to.

In step 10, communication with the engine torque controller B is performed to check the engine torque saturation flag. The engine torque controller B determines the saturation of the engine torque and determines whether the torque is positive or negative based on the throttle opening, the engine speed, the combustion mode, the engine coolant temperature, the fuel cut condition, and the like. Set and reset.

In step 11, the inertia torque I_Te generated due to the equivalent inertia change on the engine side when the gear ratio is changed is determined by the following equation.

I_Te = J1 * Gw * Gf * (dGcvtr / dt) where J1 is the moment of inertia on the input side of the engine 10 and the continuously variable transmission 11, Gw is the angular velocity of the driving wheels, and Gf is the final reduction gear. The reduction ratio Gcvtr is a speed ratio command value described later. Note that the method of calculating the inertia torque I_Te is not limited to the method of Expression 1 above.

In step 12, a final target driving force y1 for calculating the actual vehicle speed Vsp to be equal to the target vehicle speed Vspr is calculated. The calculation of the final target driving force y1 is as shown in FIG.
It is performed using a vehicle speed feedback compensator based on a model matching method and an approximate zeroing method, which are linear control methods. The mathematical model of the controlled object built into the vehicle speed feedback compensator is a model of the vehicle with the target driving force as an operation amount and the vehicle speed as a control amount, and thus the transient characteristics of a relatively responsive engine or torque converter. , And the nonlinear steady-state characteristic of the torque converter can be omitted. Then, the target throttle opening is calculated using the previously measured engine non-linear characteristic data map so that the actual driving force coincides with the target driving force, and the throttle opening is servo-controlled to reduce the non-linear characteristics of the engine. Can be linearized. Therefore, the mathematical model in which the target driving force is input and the vehicle speed is output has an integral characteristic, and the compensator can set the transfer characteristic of this vehicle model to the pulse transfer function P (z-1).

(Z-1) is a delay operator, and when it is multiplied by (z-1), it becomes a value one sampling cycle ago. Similarly, (z-n)
Is a general expression of a delay operator, and when multiplied by (z−n), it becomes a value n sampling periods before. In addition, "-1", "-
n ”is the power of“ power to the power ”in algebra and should be strictly expressed in superscripts. However, in this specification, (z−1), (z−1), (z-n)
Is expressed as

FIG. 3 shows an embodiment of a vehicle speed feedback compensator represented by a discrete time system. C1 (z-1), C2
(z-1) is a disturbance estimator using the approximate zeroing method,
Reduce the effects of disturbances and modeling errors. Further, C
3 (z-1) is a compensator based on the model matching method,
The response characteristics of the control target when the target vehicle speed Vspr is input and the actual vehicle speed Vsp is output are matched with the characteristics of the reference model H (z-1) having a predetermined first-order lag and dead time element.

It is necessary to consider the dead time, which is the delay of the power train, as the transfer characteristic of the controlled object. The pulse transfer function P (z-1) of the controlled object which receives the target driving force as input and outputs the actual vehicle speed is represented by an integral element P1 (z-1) and a dead time element P2 (z-1) (= z-n).

P1 (z−1) = T · (z−1) / {M · (1− (z−1))} where T is a sampling period (10 in this embodiment).
msec), M is the average vehicle weight.

At this time, the compensator C1 (z-1) is expressed by the following equation.

C1 (z−1) = (1−γ) · (z−1) / ｛1−γ · (z−
1)｝, that is, the compensator C1 (z-1) is a low-pass filter.

Further, the compensator C2 (z-1) is represented by the following equation as C1 / P1.

## EQU4 ## C2 (z-1) = M. (1-.gamma.). (1- (z-1))
/ {T · (1−γ · (z−1))} The compensator C2 is obtained by applying a low-pass filter to the inverse system of the vehicle model. By inputting the actual vehicle speed Vsp to the compensator C2, The driving force according to the actual vehicle speed Vsp, that is, the driving force obtained by subtracting disturbance such as running resistance from the driving force of the power train can be calculated backward.

The cutoff frequency (time constant) of the low-pass filter in the compensator C1 (z-1) is set based on the saturation and non-saturation of the engine torque. That is, when the engine torque is not saturated,

Γ = exp (−T / Tb1) On the other hand, when the engine torque is saturated,

Γ = exp (−T / Tb2) Here, Tb1 and Tb2 are time constants, and Tb1 <Tb2.

Assuming that the reference model H (z-1) is a first-order low-pass filter with a time constant Ta ignoring the dead time of the control object, the compensator C3 has the following constants.

C3 = K = {1-exp (-T / Ta)}. M / T

An operation corresponding to the model matching compensator C3 (z-1) is performed, and the actual vehicle speed Vsp is calculated based on the target vehicle speed Vsp.
A target driving force y4 for accelerating to r is obtained. Assuming that data y (k) represents the driving force at the time of the current sampling, and data y (k-1) represents the driving force one sampling cycle before,

Y4 (k) = K４ {Vspr (k) -Vsp (k)}

Next, a part corresponding to a part of the robust compensator C2 (z-1) of the disturbance estimator is calculated, and the actual vehicle speed Vsp is calculated.
, Ie, the driving force y3 obtained by subtracting disturbance such as running resistance from the driving force of the power train.

Y3 (k) = γ · y3 (k−1) + (1−γ) · M
{Vsp (k) -Vsp (k-1)} / T

As described above, the driving force y3 (k) is a driving force corresponding to the actual vehicle speed Vsp, that is, a driving force obtained by subtracting disturbance such as running resistance from the driving force of the power train. On the other hand, since the compensator C1 is a low-pass filter, the driving force y2 (k) is a driving force obtained by subjecting the target driving force y1 to low-pass filtering. This driving force y2 (k) is added to the delay operator (z
-n) multiplied by the driving force y2 (kn) is the value of the driving force y2 (k) before n sampling periods, and is regarded as the current actual driving force of the power train in consideration of the power train delay (dead time). be able to. Therefore, if the driving force y3 (k) corresponding to the actual vehicle speed obtained by subtracting the disturbance such as the running resistance from the current driving force y2 (kn) of the power train is subtracted, the disturbance Fr such as the running resistance can be estimated. .

Next, the target driving force y4 (k) is corrected by the estimated running resistance Fr to obtain a final target driving force y1 (k) for compensating for the driving force shortage due to the disturbance.

## EQU10 ## Fr = y2 (kn) -y3 (k), y1 (k) = y4
(k) + Fr, = y4 (k) + y2 (kn) -y3 (k) As described above, the disturbance estimator configured by the approximate zeroing method has a difference between the output of the controlled object model and the actual output of the controlled object. It is possible to accurately estimate disturbance such as running resistance on the basis of.

Further, an operation of a part corresponding to the compensator C1 (z-1) as a low-pass filter which is a part of the disturbance estimator is performed.

Y2 (k) = γ · y2 (k−1) + (1−γ) · y1 (k−1)

The target driving torque Tor is calculated based on the final target driving force y1 (k).

Where Rt is an effective radius of the tire.

Returning to FIG. 2, the description of the vehicle speed control will be continued. In step 13, the sign of the target drive shaft torque Tor is determined. If it is positive, the process proceeds to step 14, and if it is negative, the process proceeds to step 15. If the target drive shaft torque Tor is positive, at step 14, an operating point of the engine 10 for obtaining both the target drive shaft torque Tor and the optimal fuel efficiency is determined. First, the target output L is calculated by the following equation.

L = Tor.Vspr / Rt or L = y1 / Vspr

Next, using the engine characteristic diagram shown in FIG. 4, the operating point at which the fuel consumption rate is minimized while achieving the target output L (positive value), that is, the intersection point between the equal output line and the equal fuel consumption line will be described. Search for points on the optimal fuel economy line. Actually, the target engine operating point corresponding to the output value (positive value), that is, the target engine rotational speed Ner determined by the intersection of the equal output line and the optimal fuel consumption line is stored in the map in advance, and the target output L Perform a lookup operation using (positive value).

On the other hand, when the value of the target drive torque Tor is negative, in step 15, the negative target drive shaft torque command value Tor
Is obtained when the throttle 10 is fully closed and the fuel is cut off. First, a target output L is obtained by the following equation.

L = Tor · Vspr / Rt or L = y1 · Vspr

Next, the engine operating point at which the target output L (negative value) is achieved in the fuel cut and throttle fully closed state is determined using the engine characteristic diagram shown in FIG. Actually, a target engine operating point corresponding to an output value (negative value), that is, a target engine rotational speed Ner determined by an intersection of an equal output line and an engine torque line when fuel is cut and the throttle is fully closed is mapped in advance. And the target output L
Perform a lookup operation using (negative value).

In step S16, the target engine speed Ner is limited by the speed ratio range that the continuously variable transmission 11 can take and the engine speed determined by the engine. In step 17, the target gear ratio Gcvtr and the target engine torque Ter
Ask for one.

Gcvtr = Ner · Rt / Vsp / Gf, Ter1 = To
r / Gcvt / Gf where Gf is the final reduction ratio and Gcvt is the actual speed ratio.

At step 18, the target engine torque Ter
A final target engine torque Ter2 is obtained based on 1 and the inertia torque I_Te.

## EQU16 ## Ter2 = Ter1 + I_Te

In step 19, the final target engine torque Ter2 is output to the engine torque controller B,
The target gear ratio Gcvtr is output to the gear ratio controller C. The engine torque controller B controls the engine 10
The throttle actuator and the fuel injection device are controlled such that the torque of the throttle valve reaches the final target value Ter2. Further, the gear ratio controller C controls the continuously variable transmission 11 so that the gear ratio becomes the target value Gcvtr.

FIG. 6 is a time chart showing a simulation result by the conventional vehicle speed control device, and FIG. 7 is a time chart showing a simulation result according to one embodiment of the present invention. These figures show that the vehicle speed is 100 km / h on a steep downhill where the engine torque is saturated.
, The target drive torque Tor and the actual drive torque To, the target engine torque Ter and the actual engine torque Te, the target speed ratio Gcvtr and the actual speed ratio Gcvt, and the target vehicle speed Vsp.
r, the actual vehicle speed Vsp, the road gradient koubai, the time constant Tb of the low-pass filter, and the like. The time constant Tb of the low-pass filter is fixed at 0.4 [sec] in the conventional device, and is switched from 0.4 [sec] to 0.8 [sec] in one embodiment.

In the conventional vehicle speed control device, the delay of the drive shaft torque increases due to the saturation of the engine torque.
Further, when an inertia torque occurs due to the shift, the stability margin in the vehicle speed control system is impaired, and as a result, hunting occurs in the vehicle speed and the like. On the other hand, in one embodiment, when the engine torque is saturated and the inertia torque cannot be corrected, the time constant is switched to 0.8 [sec], so that the stability of the vehicle speed control is secured and the vehicle speed hunting is improved. Is done.

As described above, when the engine torque is already saturated and the influence of the inertia torque cannot be canceled at the time of traveling at a constant speed on a steep uphill or downhill, if the low-pass filter of the disturbance compensator cannot cancel the influence of the inertia torque. Since the cutoff frequency was lowered by increasing the time constant,
Even if the delay of the actual drive shaft torque with respect to the target drive shaft torque increases, and even if an inertia torque occurs,
Since the vehicle speed control system weakens the correction by the disturbance compensator,
Stability of vehicle speed control can be ensured, and hunting such as vehicle speed can be improved.

In the configuration of the above embodiment, the set switch 1 and the vehicle speed control controller A serve as vehicle speed setting means, the vehicle speed sensor 7 serves as vehicle speed detecting means, the vehicle speed control controller A serves as driving force calculating means, disturbance estimating means, The driving force correcting means and the engine control command value calculating means, the engine torque controller B constitutes the engine torque control means and the engine torque saturation detecting means, and the gear ratio controller C constitutes the gear ratio control means.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment.

FIG. 2 is a flowchart illustrating vehicle speed control according to one embodiment.

FIG. 3 is a diagram illustrating a vehicle speed feedback compensator according to an embodiment represented in a discrete time system.

FIG. 4 is an engine characteristic diagram when the engine torque is positive.

FIG. 5 is an engine characteristic diagram when the engine torque is negative.

FIG. 6 is a diagram showing a simulation control result by a conventional vehicle speed control device.

FIG. 7 is a diagram showing a simulation result of one embodiment.

FIG. 8 is a diagram showing response characteristics of a drive shaft torque and a gear ratio when engine torque is not saturated by a conventional vehicle speed control device.

FIG. 9 is a diagram showing response characteristics of a drive shaft torque and a gear ratio when engine torque is saturated by a conventional vehicle speed control device.

[Explanation of symbols]

 A vehicle speed control controller B engine torque controller C gear ratio controller 1 set switch 2 accelerator switch 3 coast switch 4 cancel switch 5 brake switch 6 crank angle sensor 7 vehicle speed sensor 8 accelerator sensor 9 primary rotational speed sensor 10 engine 11 beltless stepless transmission

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16H 61/02 F16H 61/02

Claims (2)

[Claims] 1. A vehicle speed setting means for setting a target vehicle speed, a vehicle speed detecting means for detecting an actual vehicle speed, a driving force calculating means for calculating a target driving force for making the actual vehicle speed coincide with the target vehicle speed, A disturbance estimating means for estimating a disturbance applied to the vehicle by the target driving force and the actual vehicle speed by using a mathematical model of a controlled object having a driving force as an operation amount and an actual vehicle speed as a control amount, and Driving force correcting means for correcting a target driving force; engine control command value calculating means for calculating a target engine torque and a target engine rotation speed for achieving the target driving force correction value; Engine torque control means for controlling engine torque, and speed ratio control for controlling the speed ratio of the continuously variable transmission such that the engine speed matches the target engine speed. A vehicle speed control device for a vehicle with a continuously variable transmission, comprising: engine torque saturation detecting means for detecting a saturated state of engine torque; wherein the disturbance estimating means comprises: A vehicle speed control device for a vehicle with a continuously variable transmission, wherein when a state is detected, a time constant of a filter process applied to the target driving force and the actual vehicle speed is changed. 2. The vehicle speed control device for a vehicle with a continuously variable transmission according to claim 1, wherein the disturbance estimating means increases the time constant of a low-pass filter and cuts when a saturation state of the engine torque is detected. A vehicle speed control device for a vehicle with a continuously variable transmission, characterized in that the off-frequency is reduced.