JP2014070552A - Control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress torsional vibration generated in a power transmission system by accurately estimating behavior of the power transmission system even in shift change for changing a speed reduction ratio of a transmission.SOLUTION: A control device for a vehicle includes a behavior estimating portion 27 for estimating various state quantities including a wheel-side estimated speed ω' and engine-side estimated speed ω' of a drive shaft 3 by using an observer equation, and a feedback portion 22 calculating a torque correction quantity Tas a correction quantity of a request torque Tof an engine 1 according to driver's operation on the basis of an estimated speed difference (ωb'-ωe') as the difference between both speeds, and outputting the calculated torque correction quantity Tto a torque control portion 23. The torque control portion 23 controls each section of the engine 1 so that a corrected target torque Tas a value obtained by adding the torque correction quantity Tinput from the feedback portion 22, to the request torque T, is generated in the engine 1.

Description

  The present invention relates to an apparatus for controlling a vehicle including an engine, a drive shaft connected to an output shaft of the engine via a transmission, and a wheel attached to an end of the drive shaft.

  2. Description of the Related Art Conventionally, in the field of vehicle control technology, techniques for suppressing vehicle vibration due to the behavior of a power transmission system that transmits output torque of a drive source such as an engine to wheels have been studied.

  For example, in Patent Document 1 below, in a hybrid vehicle in which a wheel is driven using both an engine and a motor generator, the torsion angle (elastic interference mechanism) existing between the engine and the motor generator is observed by an observer (observation). It is disclosed that the value of the crank angle of the engine is corrected based on the result or the like. The observer refers to a function that restores the value of the state variable as an estimated value using what can be detected.

  As described above, if the crank angle of the engine including the torsion damper torsion can be accurately estimated, the motor generator and the engine can be controlled in consideration of the accurate crank angle. It becomes possible to improve the riding comfort of the vehicle by suppressing torsional vibration and the like.

JP 2003-301731 A

  By the way, the vehicle is equipped with a transmission that transmits to the wheel side while decelerating the rotation of the crankshaft of the engine, and the reduction ratio of this transmission depends on the operation of the driver while the vehicle is running or It is automatically changed according to the running state of the vehicle. Before and after such a shift change, the engine rotational speed (crankshaft rotational speed) changes suddenly, and an error occurs in the solution of the vibration model using the observer. Although this error converges as the calculation is repeated, if it takes a long time to converge, an accurate crank angle cannot be obtained for that period, so the torsional vibration cannot be suppressed and the ride comfort may deteriorate. There is.

  The present invention has been made in view of the circumstances as described above, and can accurately estimate the behavior of the power transmission system even during a shift change in which the reduction ratio of the transmission changes. An object of the present invention is to provide a vehicle control device capable of effectively suppressing the torsional vibration of the vehicle.

  In order to solve the above problems, the present invention provides a vehicle including an engine, a drive shaft connected to the output shaft of the engine via a transmission, and a wheel attached to an end of the drive shaft. A control device, a torque control unit that sets a control target value of each part of the engine so that a specified torque is generated, and behavior of a control target model that models a power transmission system of a vehicle including the drive shaft Is an estimated value of the wheel-side estimated speed of the drive shaft on the wheel side and an estimated value of the engine speed of the drive shaft from the known value related to the behavior of the vehicle using the observer equation describing A behavior estimation unit for estimating various state quantities including the estimated speed on the engine side, and a wheel side estimation of the drive shaft obtained by the behavior estimation unit. Based on the estimated speed difference that is the difference between the speed and the engine-side estimated speed, a torque correction amount that is a correction amount for the requested torque of the engine according to the driver's operation is calculated, and the calculated torque correction amount The torque control unit controls each part of the engine so that a corrected target torque, which is a value obtained by adding the torque correction amount input from the feedback unit to the required torque, is generated in the engine. It is characterized by controlling (Claim 1).

  According to the present invention, the rotational speeds of the wheel side and the engine side of the drive shaft are estimated by the calculation using the observer equation. Therefore, unlike the case of estimating the rotational speed of the output shaft of the engine, for example, Even when a shift change (change in the reduction ratio) is performed, the estimated value immediately after the shift change does not greatly deviate from the actual value. Therefore, it is possible to accurately estimate the rotational speed of the wheel side of the drive shaft and the engine side (so as to follow the actual value well) and to properly determine the engine torque based on the difference between these estimated speeds (estimated speed difference). Can be corrected. This makes it possible to quickly converge torsional vibration (shift shock) of the drive shaft that occurs particularly during shift changes, thus effectively reducing vibration transmitted to the passenger compartment and improving passenger comfort. Can do.

  In the present invention, preferably, the observer equation includes an observer gain that is a coefficient that determines a convergence speed of an error of the estimated state quantity, and the behavior estimation unit determines the magnitude of the observer gain as an engine The lower the rotation speed, the smaller is set (claim 2).

  As described above, when the magnitude of the observer gain is changed according to the engine speed, the influence of noise components outside the model is weakened on the lower rotation side where the torque generation interval (ignition interval) due to combustion becomes longer. be able to. As a result, it is possible to reliably avoid situations where the estimated value fluctuates microscopically in the low engine speed range and the control becomes unstable, and the convergence speed of the estimated value error is increased outside the low engine speed range. Thus, the estimation accuracy can be further improved.

  In the present invention, it is preferable that the torque control unit corrects the engine torque only when the absolute value of the torque correction amount input from the feedback unit exceeds a predetermined threshold.

  In this way, when the engine torque is corrected only when the absolute value of the torque correction amount is large, it is not necessary to perform torque correction when the torsional vibration of the drive shaft is small, so passenger comfort is required. While ensuring at a sufficient level, it is possible to effectively prevent the engine performance from being deteriorated due to frequent control (for example, ignition timing retard) required for torque correction.

  In the present invention, it is preferable that the feedback unit at a point in time when a delay time of torque generation based on the ignition interval elapses from the estimated speed difference of the drive shaft according to a predetermined arithmetic expression using the resonance frequency of the drive shaft. An estimated speed difference is obtained, and the torque correction amount is calculated based on the estimated speed difference after the delay time has elapsed.

  According to this configuration, the engine torque can be corrected by an appropriate amount according to the speed difference at the time when the torque is actually generated, and the torsional vibration of the drive shaft can be more reliably converged.

  As described above, according to the vehicle control device of the present invention, the behavior of the power transmission system can be accurately estimated even during a shift change in which the reduction ratio of the transmission changes. Vibration can be effectively suppressed.

It is a top view which shows roughly an example of the vehicle to which the control apparatus of this invention is applied. It is a block diagram which shows the control system of the said vehicle. It is a functional block diagram for demonstrating the role which each part of the said control apparatus plays. It is a figure which shows the control object model which modeled the power transmission system of the said vehicle. It is a figure which shows the relationship between the magnitude | size of an observer gain, and an engine speed. It is a flowchart which shows the specific procedure of the control performed during driving | running | working of the said vehicle. It is a time chart which shows the control state of the engine in driving | running | working of the said vehicle in time series. It is a figure which shows the result of the experiment conducted in order to confirm the effect of this invention. FIG. 9 is a view corresponding to FIG. 8 in a comparative example of the present invention.

(1) Configuration of Vehicle FIG. 1 is a plan view schematically showing an example of a vehicle to which the control device of the present invention is applied. The vehicle shown in the figure includes an engine 1 that is a driving source for traveling, a pair of drive shafts 3 that are connected to a crankshaft 10 that is an output shaft of the engine 1 via a transmission 2, and each drive shaft 3. A pair of wheels 4 attached to the outer ends in the vehicle width direction, and a PCM 20 that controls each part of the engine 1 according to the traveling state of the vehicle and the like.

  The engine 1 is an internal combustion engine that obtains power by burning fuel therein. The type of the internal combustion engine is not particularly limited, but in this embodiment, a four-cycle multi-cylinder gasoline engine is used as the engine 1. Although not shown in detail, the engine 1 according to the present embodiment is provided with a plurality of cylinders 11 in which pistons are reciprocably accommodated, and an intake passage for adjusting the amount of air supplied to each cylinder 11. The throttle valve 12 (FIG. 2), the injector 13 (FIG. 2) for injecting fuel (gasoline) into each cylinder 11, and the mixture of fuel and air injected from the injector 13 is supplied with sparks and mixed. And an ignition plug 14 (FIG. 2) for igniting the mind.

  The engine 1 is provided with an alternator 15 that generates power by obtaining power from the crankshaft 10. The electric power generated by the alternator 15 is charged in power storage means such as a battery (not shown), and the electric power is used to operate various electrical components provided in the vehicle.

  The transmission 2 transmits the rotation of the crankshaft 10 of the engine 1 to the drive shaft 3 while decelerating. Since the vehicle according to the present embodiment is a so-called front engine / front drive type vehicle, the transmission 2 is integrated with a differential device (differential) that distributes the engine rotation after deceleration to the left and right wheels 4. Is used.

  Specifically, the transmission 2 is a multistage transmission that can select any one of a plurality of different reduction ratios. In particular, in this embodiment, the reduction ratio is manually operated by a driver. A manual transmission in which is changed is used as the transmission 2. For this reason, a clutch 16 is provided inside the transmission 2. The clutch 16 transmits torque input from the crankshaft 10 of the engine 1 to the transmission 2 so as to be intermittent according to the operation of the clutch pedal 19 by the driver.

  FIG. 2 is a block diagram showing a vehicle control system of the present embodiment. As shown in the figure, the PCM 20 that controls the engine 1 receives various information from a plurality of sensors provided in the vehicle. Specifically, the vehicle has an engine speed sensor SW1 for detecting the rotational speed of the crankshaft 10 of the engine 1, and a rotational speed (wheel speed) of the wheel 4 or a traveling speed (vehicle speed) of the vehicle. Depending on the vehicle speed sensor SW2, the accelerator position sensor SW3 for detecting the accelerator position that is the operation amount of the accelerator pedal 17 (FIG. 1) operated by the driver, and the brake pedal 18 (FIG. 1) operated by the driver. And a brake pressure sensor SW4 for detecting the pressure (brake pressure) of the brake fluid that changes in response to this, information detected by these sensors SW1 to SW4 is sequentially input to the PCM 20. . The PCM 20 sequentially determines the torque to be generated in the engine 1 while executing various calculations based on the information input from the sensors SW1 to SW4, and sends a control signal corresponding to the result to the throttle valve 12 and the injector. 13 and the spark plug 14.

(2) Control during vehicle travel (2-1) Overview of control Next, torque control of the engine 1 performed by the PCM 20 during vehicle travel will be described in detail. FIG. 3 is a functional block diagram for explaining the role played by the PCM 20 during traveling of the vehicle. As shown in the figure, PCM 20 includes a torque converter 21 which calculates the required torque T ₀ of the engine 1 based on the accelerator opening degree, the engine 1 based on the required torque T ₀ calculated by the torque converter 21 Torque control unit 23 for setting the control target value of each unit, actual machine measurement unit 24 for acquiring information input from each sensor SW1 to SW4 of the vehicle, and vehicle running resistance based on the information obtained by actual machine measurement unit 24 A running resistance estimation unit 25 that estimates the torque, a torque estimation unit 26 that estimates torque generated in the engine 1 based on a control target value set by the torque control unit 23, an actual machine measurement unit 24, a running resistance estimation unit 25, and Based on the information obtained by the torque estimation unit 26, a behavior estimation unit 27 that estimates the behavior of the vehicle including the state of the drive shaft 3, and a dry motion estimated by the behavior estimation unit 27 And a feedback unit 22 that calculates a correction amount for the required torque T ₀ of the engine 1 based on the state of the bus shaft 3.

More specific functions performed by the units 21 to 27 of the PCM 20 will be described. First, the torque converter 21 calculates a required torque T ₀ required for the engine 1 based on information (accelerator opening) input from the accelerator opening sensor SW3. In the calculation at this stage, the torsion of the drive shaft 3 is not considered, and the required torque T ₀ is calculated under the assumption that the drive shaft 3 is a rigid body. For this reason, the required torque T ₀ is simply set to be proportional to the accelerator opening (larger as the accelerator opening is larger).

The torque control unit 23 calculates the intake air amount, the fuel injection amount, and the ignition timing of the engine 1 necessary for generating the required torque T ₀ obtained by the torque conversion unit 21 and a control target for realizing it. As values, the target opening of the throttle valve 12, the target valve opening period of the injector 13, the target power supply timing to the spark plug 14, and the like are set.

  The actual machine measurement unit 24 sequentially acquires measurement values such as engine rotation speed, vehicle speed, and brake pressure based on input signals from the engine speed sensor SW1, the vehicle speed sensor SW2, and the brake pressure sensor SW4.

The running resistance estimation unit 25 calculates a running resistance (running resistance estimation value) T _b that is expected to be applied to the vehicle based on the vehicle speed and the brake pressure obtained by the actual machine measurement unit 24. Specifically, the estimated running resistance value T _b is calculated by using a predetermined arithmetic expression using the vehicle speed and the brake pressure as variables. The higher the vehicle speed and the brake pressure, the larger the estimated running resistance value T _b is. The

The torque estimation unit 26 actually uses the engine 1 based on the control target values of the throttle valve 12, the injector 13, and the spark plug 14 set by the torque control unit 23 and the engine rotation speed obtained by the actual machine measurement unit 24. torque that is expected to occur and calculates the (engine torque estimated value) T _e. Specifically, the calculation of the engine torque estimation value T _e, the stored torque characteristic data of the engine 1 is used in advance. That is, the PCM 20 has torque characteristic data based on actual measured values of the torque when the engine 1 is operated under various conditions, that is, the generated torque of the engine 1 includes fuel injection amount, air-fuel ratio, ignition timing, engine speed, and the like. Data that experimentally specifies how it changes according to various parameters is stored. Then, based on the torque characteristic data, the throttle valve 12 described above, the injector 13, the engine torque estimated value T _e corresponding to each control target value and the engine rotational speed of the spark plug 14 is determined.

Behavior estimating unit 27 includes an engine rotational speed actual measuring unit 24 is obtained, and the engine torque estimated value T _e of the torque estimation unit 26 was determined, and the running resistance estimated value T _b of the vehicle running resistance estimating unit 25 is determined Based on the above, various state quantities of the vehicle are estimated. Specifically, the behavior estimation unit 27, an engine rotational speed (value converted to a rotation of more precisely the drive shaft), the engine torque estimated value T _e, and the known values such as the running resistance estimation value T _b, below Using the equation (observer equation (2)), various state quantities related to torsion of the drive shaft 3 are estimated. In this way, the state quantity is estimated by the observer equation using known values, and unlike the case where the state quantity is directly measured using a sensor or the like, an accurate state quantity that is not easily affected by noise or the like. Can know.

The state quantity estimated by the behavior estimation unit 27 includes the engine-side rotation speed of the drive shaft 3 and the wheel-side rotation speed of the drive shaft 3. Here, “the rotational speed of the drive shaft 3 on the engine side” refers to the rotational speed of one end portion of the drive shaft 3 located on the side closer to the engine 1 (and the transmission 2) in the control target model of FIG. ω _e and “the rotational speed of the drive shaft 3 on the wheel side” is the rotational speed ω _b of the other end of the drive shaft 3 located on the side close to the wheel 4. Hereinafter, the estimated values of both the speeds ω _e and ω _{b by} the observer equation are respectively expressed as the engine side estimated speed ω _e ′ of the drive shaft 3 and the wheel side estimated speed ω _b ′ of the drive shaft 3.

Based on the difference between the wheel-side estimated speed ω _b ′ of the drive shaft 3 and the engine-side estimated speed ω _e ′ obtained by the behavior estimating unit 27, the feedback unit 22 is a torque for converging torsional vibration of the drive shaft 3. The correction amount _TQ is calculated. That is, the difference between the rotational speeds ω _b ′ and ω _e ′ means that the amount of twist of the drive shaft 3 is changing. Therefore, the feedback unit 22, how the correction or may be the engine torque in order not to cause such a change in torsion amount is calculated, the value is determined as the torque correction amount T _Q.

For example, when the engine-side estimated speed ω _e ′ of the drive shaft 3 is larger than the wheel-side estimated speed ω _b ′, it is necessary to decrease the engine-side estimated speed ω _e ′ so as not to change the twist amount of the drive shaft 3. Therefore, the engine torque is also corrected in the decreasing direction (torque correction amount _TQ becomes negative). On the other hand, when the engine-side estimated speed ω _e ′ is smaller than the wheel-side estimated speed ω _b ′, it is necessary to increase the engine-side estimated speed ω _e ′ in order not to change the twist amount of the drive shaft 3. The engine torque is also corrected in the increasing direction (torque correction amount _TQ becomes positive).

The torque correction amount T _Q calculated by the feedback unit 22 is output to the torque control unit 23. The torque control unit 23 obtains a corrected target torque T _fb that is a value obtained by adding the torque correction amount T _Q to the above-described required torque T ₀ , and the intake air amount so as to obtain the corrected target torque T _fb. Then, the fuel injection amount and the target value of the ignition timing are reset, and the throttle valve 12, the injector 13, and the spark plug 14 are controlled based on these values.

Here, the method for correcting the torque of the engine 1 by the amount of torque correction amount T _Q is are various, but in those embodiments, and adjusts the torque in the following manner.

First, when the torque correction amount _TQ is a negative value and the generated torque of the engine 1 needs to be reduced, the ignition timing (timing for supplying sparks from the spark plug 14) is retarded. That is, by delaying the ignition timing from the original timing (a timing that is predetermined according to the situation so that the best combustion can be obtained), the timing at which the air-fuel mixture burns in the cylinder is delayed, and the generated torque of the engine 1 Decrease.

On the other hand, when the torque correction amount _TQ is a positive value and the generated torque of the engine 1 needs to be increased, the power generation amount of the alternator 15 that generates power by obtaining power from the engine 1 is decreased. That is, by reducing the power generation amount of the alternator 15, the resistance force applied from the alternator 15 to the engine 1 is reduced. Thereby, substantially the same effect as that in which the generated torque of the engine 1 is increased can be obtained.

(2-2) State Quantity Estimation Method Next, it will be specifically described what kind of calculation is performed by the behavior estimation unit 27 to estimate various state quantities. FIG. 4 is a diagram illustrating a control target model that models a power transmission system that transmits the output torque of the engine 1 to the wheels. As already described with reference to FIG. 1, the power transmission system of the vehicle includes a transmission 2 that decelerates the rotation of the crankshaft 10 of the engine 1, and a drive that connects the output shaft of the transmission 2 and the wheels 4. Shaft 3 is included. Since the drive shaft 3 has an element as a spring that is torsionally deformed in proportion to the torque and an element as a damper that generates a resistance force that is proportional to the speed of the torsional deformation, in the control target model of FIG. The shaft 3 is expressed by a spring and a damper.

  The vehicle state equation derived from the controlled object model of FIG. 4 is described as the following equation (1).

  The meaning of each numerical value in the state equation (1) is as shown in Table 1 below.

  Based on the state equation (1), the following observer equation (2) extended to estimate various state quantities including a running resistance error can be derived.

  The meaning of each numerical value in the observer equation (2) is as shown in Table 2 below.

The behavior estimation unit 27 estimates various state quantities ω _e ′, ω _b ′, θ ′, T _err ′ of the vehicle from known values T _e , T _b , ω _e using the observer equation (2). To do. That is, the behavior estimation unit 27 includes an engine torque estimation value T _e inputted from the torque estimation unit 26, a running resistance estimation value T _b of the vehicle which is inputted from the running resistance estimating unit 25, is input from the actual measuring unit 24 By applying these values to the observer equation (2), the estimated engine-side speed ω _e ′ of the drive shaft 3, the wheel-side rotational speed ω _b ′ of the drive shaft 3, An estimated twist amount θ ′ of the drive shaft 3 and an estimated value T _err ′ of the running resistance error of the vehicle are obtained. Note that the engine rotational speed input from the actual machine measurement unit 24 is converted into the rotational speed of the drive shaft 3 (that is, the value divided by the reduction ratio η of the transmission 2 is obtained), and the value is set as ω _e . Applies to the observer equation (2).

Here, the observer gain K in the observer equation (2) can be calculated from an optimum gain calculation function used in a control design tool such as MATLAB. Here, if the magnitude of the observer gain K is defined as (K ₁ ² + K ₂ ² + K ₃ ² + K ₄ ² ) ^1/2 using the components K _{1 to} K ₄ , the magnitude of the observer gain K Is set to be smaller as the engine rotational speed is slower by the optimum gain calculation function (see FIG. 5). Note that the fact that the magnitude of the observer gain K is small means that one or more of the components K _{1 to} K ₄ are small. Other components may be constant regardless of the engine speed, but at least do not increase. As described above, the reason why the magnitude of the observer gain K is decreased as the engine speed is lower is as follows.

  In other words, a large size of the observer gain K means that the convergence speed of the estimated value error is increased, but at the same time, the influence of high-frequency measurement noise and non-linear elements outside the model is strong. Means that. In particular, when the engine rotation speed is low, the generation interval of torque due to combustion is relatively long, and noise components due to disturbance are likely to occur during that interval. Therefore, in this embodiment, as shown in FIG. 5, when the engine rotation speed is low (particularly when the engine speed is 1000 rpm or less), the magnitude of the observer gain K is set so as to be less affected by noise components outside the model. Is set smaller. Note that the magnitude of the observer gain K may be changed only in a region lower than a specific engine speed (for example, 1000 rpm), and may be maintained at a constant value in a region higher than that.

  Further, the reduction ratio η in the observer equation (2) is specified from the ratio between the engine rotational speed detected by the engine speed sensor SW1 and the wheel speed (rotational speed of the wheel 4) detected by the vehicle speed sensor SW2. . More specifically, a plurality of reduction ratios set corresponding to the respective speed stages of the transmission 2 are identified and matched with or close to the ratio of the engine rotational speed and the wheel speed. Used as the ratio η.

  As described above, the theory that is the basis of state quantity estimation by the behavior estimation unit 27 has been described. However, what is used for the actual calculation in the behavior estimation unit 27 is the following discretization of the observer equation (2). Equation (3).

Δt in the above discrete equation (3) is a time interval (sampling time) for the behavior estimating unit 27 to obtain an estimated value of the state quantity, and is set to about 1 msec, for example. That is, the behavior estimation unit 27 estimates the chi _ext [i] obtained in the past, obtains an estimated value after Δt χ _ext [i + 1] by using the discrete equation (3), such processing Delta] t Repeat every time. Such a process, because it is continued immediately after the engine 1 is started, as the chi _ext initial value chi _ext [0] is selected is (0 0 0 0) ^T.

(2-3) Specific procedure of control during traveling of vehicle FIG. 6 shows each part of the PCM 20 (torque conversion unit 21, torque control unit 23, actual machine measurement unit 24, traveling resistance estimation unit 25, torque estimation during traveling of the vehicle. It is a flowchart which shows the specific procedure of the control performed by the part 26 and the behavior estimation part 27). Here, the torque correction amount T _Q determined based on the difference between the wheel side estimated speed ω _b ′ of the drive shaft 3 and the engine side estimated speed ω _e ′ becomes negative (that is, the generated torque of the engine 1 decreases). The explanation will be made on the assumption that the direction is corrected).

When the flow shown in FIG. 6 starts, the PCM 20 calculates the required torque T ₀ required for the engine 1 based on the information on the accelerator opening (the amount of operation of the accelerator pedal 17) input from the accelerator opening sensor SW3. The calculation process is executed (step S1). At this stage, the torsion of the drive shaft 3 is not considered, and the required torque T ₀ is set so as to be proportional to the accelerator opening.

Next, the PCM 20 executes processing for calculating the intake air amount, the fuel injection amount, and the ignition timing for realizing the required torque T ₀ of the engine obtained in step S1 (step S2).

Then, PCM 20 is speed inputted from the vehicle speed sensor SW2 and the brake pressure sensor SW4, based on the information of the brake pressure, executes a process of calculating the estimated value of the running resistance applied to the vehicle (running resistance estimated value) T _b (Step S3).

Next, the PCM 20 receives information on the engine speed input from the engine speed sensor SW1, the intake air amount, the fuel injection amount, and the ignition timing (that is, the throttle valve 12, the injector 13, and the spark plug 14) obtained in step S2. based on the respective control target value), the estimated value of torque generated by the engine 1 (to execute a process of calculating an engine torque estimated value) T _e (step S4). In place of the torque estimation process using the control target value of the throttle valve 12, the ignition is performed next (in the nearest future) from the measured value of the intake air amount by an air flow sensor or the like and the physical model of the intake system. estimating a cylinder air amount of cracking cylinders, may be calculated engine torque estimated value T _e based on the estimated value.

Then, PCM 20 includes the engine rotational speed information input from the engine speed sensor SW1, a running resistance estimation value T _b of the vehicle obtained in step S3, the engine torque estimated value obtained in step S4 T _e Is applied to the above-described observer equation (2) (more specifically, an equation (3) obtained by discretizing it), thereby estimating the engine-side estimated speed ω _e ′ of the drive shaft 3 and the wheel-side estimation of the drive shaft 3. Processing for calculating various state quantities including the speed ω _b ′ is executed (step S5). At this time, the magnitude of the observer gain K used in the observer equation (2), that is, the square root of the square sum of the components K _{1 to} K ₄ is set to a smaller value as the engine rotational speed is slower as described above. (See FIG. 5).

Next, the PCM 20 determines the drive shaft 3 based on the difference (ω _b ′ −ω _e ′) between the wheel-side estimated speed ω _b ′ of the drive shaft and the engine-side estimated speed ω _e ′ obtained in step S5. It executes a process for calculating the torque correction amount T _Q of the engine 1 to be added in order to converge the torsional vibration (step S6). The absolute value of the torque correction amount T _Q is calculated to be proportional to the absolute value | ω _b ′ −ω _e ′ | of the estimated speed difference of the drive shaft 3 described above. More specifically, The torque correction amount _TQ is calculated through such calculation.

The torque of the engine 1, since the torque generated by the combustion in each cylinder 11, even if calculated torque correction amount T _Q, the torque obtained by adding the torque correction amount T _Q actually occurs, the following Is the timing at which ignition is performed. Therefore, in the present embodiment, at the time when the estimated speed difference (ω _b ′ −ω _e ′) of the drive shaft 3 at the current time advances by a delay time d determined in consideration of the torque generation delay as described above. And a torque correction amount _TQ is obtained based on the estimated value. Here, the generation delay of the torque (that is, the time until the next combustion) can be specified based on the ignition interval of each cylinder 11. The ignition interval is the time difference between the ignition timing of a certain cylinder 11 and the ignition timing of a cylinder 11 that is ignited next. For example, in the case of a 4-cylinder engine, a crank angle of 180 ° (180 ° CA ).

The estimated speed difference (ω _b ′ −ω _e ′) of the drive shaft 3 at the present time is f (t), and the estimated speed difference (ω _b ′ −ω _e ′) after the delay time d has elapsed from the current time is f (t). Assuming that t + d), the estimated speed difference f (t + d) of the drive shaft 3 after the lapse of the delay time d can be obtained from the estimated speed difference f (t) at the present time using the following equation (4). .

  In the above formula (4), a is a value corresponding to the resonance frequency (a / 2π) of the drive shaft 3 set in advance for each gear position of the transmission 2, and f ′ (t) is f (t). ) Time derivative.

That is, most of the vibration generated in an actual vehicle is torsional resonance of the drive shaft 3, and therefore the estimated speed difference (f = ω _b ′ −ω _e ′) of the drive shaft 3 depends on the resonance frequency. Since it can be assumed that f (t) = sin (at) is a changing value, f (t + d) at the time point advanced by the delay time d based on the assumption is expressed by the above equation (4). It can be expressed as

When the estimated speed difference f (t + d) of the drive shaft 3 after the lapse of the delay time d is obtained as in the above equation (4), it is determined in advance as f (t + d) as shown in the following equation (5). A value multiplied by the feedback gain k, that is, k × f (t + d) can be calculated as the torque correction amount T _Q.

Here, in this flow (FIG. 6), it is assumed that the torque of the engine 1 is corrected in the decreasing direction. For this reason, f (t + d) = ω _b ′ −ω _e ′ is negative unless otherwise specified (that is, the estimated speed ω _e ′ on the engine side is higher than the estimated speed ω _b ′ on the wheel side of the drive shaft 3). Therefore, the torque correction amount _TQ is also negative.

That is, when the speed difference (ω _b '-ω _e') is negative, in order to converge the speed difference, it is necessary to reduce the engine side rotational speed of the drive shaft 3, the negative torque correction amount T _Q Is added (that is, the engine torque is corrected in a decreasing direction).

When the torque correction amount T _Q is obtained as described above, the PCM 20 determines whether or not the absolute value (| T _Q |) of the torque correction amount T _Q is larger than a predetermined threshold value X _T. The process which performs is performed (step S7). The threshold value _XT is determined from the viewpoint of whether or not torsional vibration generated in the drive shaft 3 is detected by the occupant when the torque is not corrected.

When it is determined NO in step S7 and it is confirmed that | T _Q | ≦ X _T , the PCM 20 executes a process of operating the engine 1 at normal ignition timing (step S12). That is, the PCM 20 maintains the timing of ignition performed by the spark plug 14 at the timing set in step S2 in order to realize the required torque T ₀ based on the accelerator opening, and operates the engine 1 in that state.

On the other hand, if it is determined YES in step S7 and it is confirmed that | T _Q |> X _T , the PCM 20 determines the retard amount of the ignition timing, that is, the ignition according to the value of the torque correction amount T _Q. A process of determining how much the timing is delayed from the normal timing (the timing set in step S2) is executed (step S8). That is, in this flow, since it is assumed that the torque correction amount _TQ is negative, it is necessary to retard the ignition timing in order to reduce the generated torque of the engine 1 by this negative amount, and the retard amount at that time Is determined in step S8.

Next, the PCM 20 starts a process of operating the engine 1 with the ignition timing delayed by the retard amount determined in step S8 (step S9). That is, as the torque correction amount to the demanded torque T ₀ based on the accelerator opening T _Q corrected target torque T _fb is a value obtained by adding (negative in this case) occurs in the engine, in a state where the ignition timing was retarded The engine 1 is operated. The operation under the retard condition is continued for a predetermined time (step S10), and when the predetermined time has elapsed, the operation under the retard condition is terminated (step S11). Thereafter, unless the condition of | T _Q |> X _T (step S7) is satisfied with respect to the torque correction amount, the ignition timing is returned to the normal timing, that is, the ignition timing corresponding to the required torque T ₀ of the engine 1. become.

As described above, in the flow of FIG. 6, the torque correction amount T _Q of the engine 1 is obtained based on the difference between the wheel side estimated speed ω _b ′ of the drive shaft 3 and the engine side estimated speed ω _e ′. the absolute value of the correction amount T _Q only if greater than a predetermined threshold X _T, an ignition timing is adapted to be retarded for a predetermined time. FIG. 7 is a time chart showing an example of changes in ignition timing and the like based on such control. In this figure, the engine speed, the torque correction amount T _Q , the timer count value, and the retard permission flag are shown in order from the top.

As shown in the second stage of the graph from the top in FIG. 7, a torque correction amount T _Q is decreased in a plurality of time points to the lower line X. This is the absolute value of the torque correction amount T _Q means that exceeds the threshold value X _T described above. Then, in response to this, the retard permission flag becomes “1” (see the lowermost graph), and the ignition timing retard is started. The state is maintained for at least the time S (corresponding to the predetermined time in step S10 described above). Specifically, when the absolute value of the torque correction amount T _Q exceeds the threshold X _T (the time T _Q has decreased to below the line X), the count value of the timer initial value C (e.g., about 1 second ) And the countdown is started (see the second graph from the bottom). When the value becomes zero, the retard permission flag becomes “0”, and the ignition timing retard is prohibited. In some cases, the absolute value of the re-T _Q before the timer countdown is completed sometimes above the threshold X _T, in such a case, is set to an initial value C count value of the timer again After that, the countdown is resumed. The ignition timing is continued until the count value becomes zero.

In the flow of FIG. 6 described above, assuming that the estimated speed difference between the drive shaft _{3 (ω b '-ω e'} ) a torque correction amount T _Q calculated based on is negative, is retarded ignition timing The example in which the engine torque is corrected in the decreasing direction has been described, but the basic idea is the same even when the torque correction amount _TQ is positive. That is, the torque correction amount T _Q is determined whether more than a predetermined threshold, performing the actual torque correction only when exceeding. However, when the torque correction amount _TQ is positive, it is necessary to correct the engine torque in the increasing direction. Therefore, instead of the ignition retard, the power generation amount of the alternator 15 is decreased (that is, the resistance torque applied to the engine 1 is reduced). Decrease), thereby substantially increasing the engine torque.

(3) Operation, etc. As described above, in the above embodiment, the observer equation (2) describing the behavior of the control target model (FIG. 4) that models the power transmission system of the vehicle including the drive shaft 3 is used. , A wheel-side estimated speed ω _b ′ that is an estimated value of the wheel-side rotation speed of the drive shaft 3 from a known value (engine rotation speed, engine torque estimated value T _e , running resistance estimated value T _b ) related to the vehicle behavior. And an engine-side estimated speed ω _e ′, which is an estimated value of the engine-side rotational speed of the drive shaft 3, and is a correction amount for the required torque T ₀ of the engine according to the driver's operation (accelerator opening). the torque correction amount T _Q, because you seek based on the difference between the estimated speed _{(ω b '-ω e')} , if the reduction ratio is made a shift change of the transmission 2 is changed Also, high accuracy (i.e. so as to follow better the real value) estimated speed ω _e ', ω _b' can be obtained, it is possible to properly correct the engine torque. As a result, the torsional vibration (shift shock) of the drive shaft 3 that occurs particularly at the time of a shift change can be converged at an early stage, so that the vibration transmitted to the passenger compartment is effectively reduced and passenger comfort is further improved. be able to.

  For example, unlike the above-described embodiment in which the engine-side rotational speed of the drive shaft 3 is estimated, it is possible to use an observer equation that estimates the rotational speed (engine rotational speed) of the crankshaft 10 of the engine 1. However, in this case, when the reduction ratio changes due to the shift change, the actual engine speed changes rapidly, but the estimated engine speed is the same as that before the shift change. Can only continue to calculate. Even in this case, the estimated value of the engine speed gradually approaches the actual value along with the change in the actual state quantity after the shift change, but it takes time to converge such an error. Therefore, it becomes impossible to accurately estimate the behavior immediately after the shift change.

  On the other hand, in the above embodiment, the engine-side rotational speed of the drive shaft 3 is estimated. Since the rotational speed of the drive shaft 3 is basically the same as the rotational speed of the wheel 4, even if a shift change is performed, it does not change abruptly. For this reason, the above-mentioned problem that the estimated value immediately after the shift change greatly deviates from the actual value does not occur, and the estimation accuracy can be maintained well even immediately after the shift change.

  FIG. 8 and FIG. 9 show the results of experiments conducted to confirm the above-described effects. FIG. 8 shows the results when the rotational speed of the drive shaft 3 is an estimation target as in the above embodiment, and FIG. 9 shows the results when the engine rotational speed is an estimation target. In these figures, the solid line waveform in the upper graph represents the actual engine rotation speed, and the alternate long and short dash line waveform represents the estimated value of the engine rotation speed on the model. Note that the engine rotational speed on the model in FIG. 8 (when the rotational speed of the drive shaft 3 is an object of estimation) is the engine using the reduction ratio of the transmission 2 from the rotational speed of the drive shaft 3 obtained by estimation. It is the value converted into the rotation speed of. 8 and 9, the solid line waveform represents the reduction ratio based on the shift position of the transmission 2, and the two-dot chain line waveform represents the actual engine speed and wheel speed. The calculated reduction ratio based on the ratio is represented, and the waveform of the one-dot chain line represents the reduction ratio on the model. Further, the waveforms in the lower graphs of FIGS. 8 and 9 indicate ON / OFF of the clutch.

  Here, in the middle graphs of FIGS. 8 and 9, even if the shift position changes, the calculated reduction ratio does not change at that time t0. This is because the transmission is cut off. The calculated reduction ratio changes for the first time when the clutch starts to be switched from OFF to ON, and on the model, it is determined that the shift change has been substantially made based on this change in the calculated value. At that time t, the reduction ratio (value of η in the observer equation) on the model changes.

  As shown in FIG. 9, when the engine speed is the target of estimation, the estimated value of the rotational speed on the model is significantly different from the actual value immediately after the time t when the shift change is substantially performed. (Refer to the upper graph), and it takes a long time for the error to converge. On the other hand, as shown in FIG. 8, when the rotational speed of the drive shaft 3 is to be estimated (that is, when the method of the above embodiment is adopted), even immediately after the time t of the shift change. The estimated value on the model closely follows the actual value.

As described above, in the above embodiment, the rotational speed of the drive shaft 3 is the target of estimation, and the wheel-side estimated speed ω _b ′ and the engine-side estimated speed ω _e ′ of the drive shaft 3 are obtained. Even if it is performed, the estimated speeds ω _b ′ and ω _e ′ can be obtained with high accuracy immediately after that. Then, both the estimated speed ω _b ', ω _e' by adding an appropriate torque correction amount T _Q based on the difference, it is possible to effectively suppress the torsional vibration of the P caused the drive shaft to shift change.

In the above embodiment, the observer equation (2) for obtaining the engine-side estimated speed ω _e ′ and the wheel-side estimated speed ω _b ′ of the drive shaft 3 is used as a coefficient that affects the convergence speed of the estimated value error. Since the magnitude of the observed observer gain K is set so as to become smaller as the engine speed is slower, the influence of noise components outside the model can be weakened toward the lower rotation side where the torque generation interval (ignition interval) due to combustion becomes longer. it can. As a result, it is possible to reliably avoid a situation in which the estimated value fluctuates microscopically in the low rotation range of the engine 1 and the control becomes unstable, and the convergence speed of the error of the estimated value can be reduced outside the low rotation range. The estimation accuracy can be further improved.

Further, as described in the above embodiment, only when the absolute value of the drive estimated speed difference of the shaft _{3 (ω b '-ω e'} ) the basis the obtained torque correction amount T _Q exceeds the predetermined threshold X _T When the engine torque is corrected, it is not necessary to perform the torque correction when the torsional vibration of the drive shaft 3 is small. Therefore, it is necessary for the torque correction while ensuring the passenger comfort at a necessary and sufficient level. Therefore, it is possible to effectively prevent the performance of the engine 1 from being deteriorated due to frequent control (for example, ignition timing retard).

In other words, the fact that the absolute value of the torque correction amount T _Q exceeds the threshold X _T, the estimated speed difference between the drive shaft _{3 (ω b '-ω e'} ) it means that large, this drive shaft 3 This means that the vibration transmitted from the vehicle to the passenger compartment may increase to such an extent that the passenger can sense it. In the above embodiment, the engine torque is corrected by ignition timing retard or the like in such a case, so that the torsional vibration of the drive shaft 3 converges and passenger comfort is ensured.

On the other hand, when the absolute value of the torque correction amount T _Q is equal to or less than the threshold X _T, the estimated speed difference between the drive shaft _{3 (ω b '-ω e'} ) is small, even uncomfortable to the passenger as to leave it It is thought that no vibration is transmitted. In the above-described embodiment, torque correction is prohibited in such a case, so that control such as ignition timing retard is not performed wastefully, and the performance of the engine 1 is sufficiently extracted.

Moreover, in the said embodiment, as shown in Formula (4), the resonant frequency of the drive shaft 3 was utilized from the estimated speed difference of the drive shaft 3 at present: f (t) = ω _b ′ −ω _e ′. An estimated speed difference: f (t + d) when a delay time d of torque generation based on the ignition interval has elapsed is obtained by a predetermined arithmetic expression, and the torque correction is performed based on the estimated speed difference after the delay time d has elapsed. because you to determine the amount T _Q, actually depending on the speed difference when the torque is generated can be corrected the appropriate amount by the engine torque, it is possible to more reliably converge torsional vibration of the drive shaft 3 it can.

In the above embodiment, when the negative torque correction amount _TQ is calculated according to the estimated speed difference (ω _b ′ −ω _e ′) of the drive shaft 3, the engine torque is corrected in the decreasing direction by the ignition retard. On the other hand, when the positive torque correction amount _TQ is calculated, the engine torque is corrected in a substantially increasing direction by decreasing the power generation amount of the alternator 15, but the engine torque is corrected with good responsiveness. Any method that can be used is not limited to this, and various methods can be employed. Moreover, it is only necessary to perform the minimum torque correction when the torque correction amount T _Q where and its absolute value minus exceeds the threshold X _T, when the torque correction amount T _Q is positive even rambling uniformly torque correction Good. Even in this case, the torsional vibration of the drive shaft 3 can be converged effectively to some extent, and above all, control required for torque correction can be simplified.

  Needless to say, various modifications can be made without departing from the spirit of the present invention.

1 Engine 2 Transmission 3 Drive shaft 4 Wheel 10 Crankshaft (engine output shaft)
22 Feedback unit 23 Torque control unit 27 Behavior estimation unit

Claims (4)

An apparatus for controlling a vehicle including an engine, a drive shaft connected to an output shaft of the engine via a transmission, and a wheel attached to an end of the drive shaft,
A torque control unit that sets a control target value of each part of the engine so that a specified torque is generated;
The estimated value of the rotational speed on the wheel side of the drive shaft from the known value related to the behavior of the vehicle, using the observer equation describing the behavior of the model to be controlled that models the power transmission system of the vehicle including the drive shaft. A behavior estimation unit that estimates various state quantities including a wheel side estimated speed and an engine side estimated speed that is an estimated value of the engine speed of the drive shaft;
Based on the estimated speed difference, which is the difference between the estimated wheel speed of the drive shaft and the estimated engine speed determined by the behavior estimation unit, a torque correction amount that is a correction amount for the required torque of the engine according to the driver's operation is calculated. A feedback unit that calculates and outputs the calculated torque correction amount to the torque control unit;
The torque control unit controls each part of the engine so that a corrected target torque, which is a value obtained by adding the torque correction amount input from the feedback unit to the required torque, is generated in the engine. Control device. The vehicle control device according to claim 1,
The observer equation includes an observer gain, which is a coefficient that affects the convergence speed of the estimated state quantity error.
The vehicle control device, wherein the behavior estimation unit sets the magnitude of the observer gain to be smaller as the engine speed is slower. The vehicle control device according to claim 1 or 2,
The vehicle control device, wherein the torque control unit corrects the engine torque only when the absolute value of the torque correction amount input from the feedback unit exceeds a predetermined threshold value. The vehicle control device according to any one of claims 1 to 3,
The feedback unit obtains an estimated speed difference at the time when a delay time of torque generation based on the ignition interval has elapsed from a predetermined calculation formula using the resonance frequency of the drive shaft from the estimated speed difference of the drive shaft. A vehicle control device characterized in that the torque correction amount is calculated based on an estimated speed difference after the delay time has elapsed.

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