CN111577882B - Power gear shifting control method for automatic transmission of off-road vehicle - Google Patents

Power gear shifting control method for automatic transmission of off-road vehicle Download PDF

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CN111577882B
CN111577882B CN202010423045.5A CN202010423045A CN111577882B CN 111577882 B CN111577882 B CN 111577882B CN 202010423045 A CN202010423045 A CN 202010423045A CN 111577882 B CN111577882 B CN 111577882B
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gear
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road
speed
shifting
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CN111577882A (en
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李春明
吴维
李慎龙
郭智蔷
苑士华
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Beijing Institute of Technology BIT
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/02—Selector apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/14—Inputs being a function of torque or torque demand
    • F16H59/24—Inputs being a function of torque or torque demand dependent on the throttle opening
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/48—Inputs being a function of acceleration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/18—Preventing unintentional or unsafe shift, e.g. preventing manual shift from highest gear to reverse gear

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  • General Engineering & Computer Science (AREA)
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Abstract

The invention relates to a power gear shifting control method for an automatic transmission of an off-road vehicle, belonging to the technical field of vehicle speed change control. According to the invention, the reason for the change of the accelerator opening is judged through the change of the vertical acceleration of the vehicle, so that the error gear shifting caused by the bumpiness of the road is avoided. According to the road driving condition, the maximum gear of the off-road vehicle under the current driving condition is determined, the change of a gear shifting rule caused by the driving resistance coefficient and the gradient change is further considered, frequent gear shifting and wrong gear shifting caused by the change of the driving condition are effectively avoided, the gear shifting times and the power loss in the gear shifting process are effectively reduced, the optimal dynamic gear control of the off-road vehicle is realized, and the dynamic performance of the off-road vehicle is improved. The invention takes the best dynamic property as the target, comprehensively considers the accelerator, the driving force, the running resistance, the vehicle speed, the vertical acceleration, the longitudinal acceleration and the front road condition, realizes the best gear decision of the vehicle transmission under the off-road working condition, and leads the vehicle to obtain the best off-road dynamic property.

Description

Power gear shifting control method for automatic transmission of off-road vehicle
Technical Field
The invention relates to a power shift control method for an automatic transmission of an off-road vehicle, in particular to a shift rule and a control strategy of the vehicle transmission aiming at the optimal power of the off-road vehicle, and belongs to the technical field of vehicle speed change control.
Background
When the vehicle runs under the working condition of a road, the corresponding gear control strategy of the automatic transmission is relatively mature, the proper compromise between the dynamic property and the economical efficiency of the vehicle can be obtained to obtain the proper running gear, and the gear shifting strategy with the priority of the dynamic property or the gear shifting strategy with the priority of the economical efficiency can be selected according to the individual requirements of a driver. However, when the vehicle runs under the off-road condition, because the off-road condition is complex and changeable, time-varying and random excitation action is generated on the vehicle, so that the vehicle generates vertical vibration and running resistance change, and the problems of accidental gear shifting, cyclic gear shifting and the like can be caused by adopting a gear control strategy under the on-road condition, thereby seriously affecting the power performance of the vehicle.
In the prior art, a driving style gear shifting strategy is proposed, but the strategy considers dynamic parameters of a vehicle, such as accelerator opening, engine speed, output torque and the like, and does not consider road surface parameters; in the prior art, the adaptive gear shifting strategy according to the load degree also considers the dynamic characteristics of the vehicle. Aiming at the problems of accidental and frequent gear shifting in the off-road environment, the prior art performs smoothing treatment on the variation amplitude of the accelerator, avoids accidental gear shifting caused by violent variation of the accelerator, but does not consider the parameter which can reflect the vehicle bumping state most and is the vertical acceleration of the vehicle; in the prior art, estimation of mass and gradient generalized resistance coefficients is provided, and road resistance types are classified, but an article only considers the road resistance types and wheel slip rates to correct gears, does not limit the highest gear, and does not consider the problem of early downshift.
Disclosure of Invention
The invention aims to provide a power shift control method of an automatic transmission of an off-road vehicle, which aims at the optimal power, comprehensively considers an accelerator, a driving force, a driving resistance, a vehicle speed, a vertical acceleration, a longitudinal acceleration and a front road condition, realizes the optimal gear decision of the vehicle transmission under the off-road working condition and ensures that the vehicle obtains the optimal off-road power performance.
The purpose of the invention is realized by the following technical scheme.
A power shift control method of an automatic transmission of an off-road vehicle comprises the following steps:
step one, calculating a double-parameter gear-up rule by taking the maximum acceleration as a target through parameters;
the power control strategy of the off-road vehicle transmission takes the acceleration of the off-road vehicle as a core control parameter and takes the maximum acceleration of the off-road vehicle reaching the constraint condition as a control target, and the specific technical scheme is as follows:
based on the driving parameters of the vehicle under the good straight road surface condition, including parameters such as power device characteristics, transmission system transmission ratio and the like, rolling resistance coefficient of a road, vehicle quality of the whole vehicle and the like, the acceleration of the transmission under different accelerator opening degrees under each gear is calculated, the vehicle speed corresponding to the intersection point of the acceleration curves of two adjacent gears is extracted and used as the vehicle speed corresponding to the gear shifting point, if the acceleration curves of the adjacent gears do not have the intersection point, the maximum vehicle speed which can be reached by a low gear is used as the vehicle speed corresponding to the gear shifting point, a two-parameter gear-up rule with the acceleration as the maximum power target is obtained, and the vehicle speed of the gear shifting point which is increased from the i gear toi_up(α,β0,f0) Wherein, alpha is the accelerator opening degree, and alpha belongs to (0, 1)]；β0For straight road slopes, i.e. beta0＝0；f0The rolling resistance coefficient of a good road surface.
Step two, respectively changing the rolling resistance coefficient and the gradient of the road to obtain a new dynamic upshift rule;
respectively changing the rolling resistance coefficient and the gradient of a road, calculating a new dynamic two-parameter gear-up rule to obtain the gear-shifting point vehicle speed deviation caused by the change of the rolling resistance coefficient of the road, and recording the gear-shifting point vehicle speed considering the change of the rolling resistance coefficient when the gear i is shifted into the gear i +1 as vi_up_f(α,β0F), where f is the coefficient of varying rolling resistance, f ∈ ΩfF is taken as the set omegafAny value of (1); similarly, the speed deviation of the gear shifting point caused by gradient change is obtained, and the speed of the gear shifting point which is raised from the i gear to the i +1 gear and considers the gradient change is recorded as vi_up_β(α,β,f0) Where β is the varying road grade, β ∈ ΩβBeta is taken as set omegaβAny value of (1); when the rolling resistance coefficient and the gradient are changed simultaneously, the speed of the corresponding gear shifting point from the i gear to the i +1 gear is recorded as vi_up_con(α,β,f)。
Step three, downshifting
In order to reduce the number of shifts during vehicle travel, avoid cyclic shifts as appropriate, and for downshiftsThe gear shifting delay delta v is set on the basis of the gear-up lawj_udThe vehicle speed at the shift point of the gear from the gear j to the gear j-1 is recorded as vj-1_down_tThen v isj-1_down_t＝vi_up-Δvj_ud. Therefore, when the vehicle decelerates to the down-range, its vehicle speed is less than that at the corresponding upshift. Upshift vehicle speed vi_upIf the condition of maximum acceleration is met, then during the deceleration of the vehicle to the downshift point, the acceleration of the vehicle is less than the maximum acceleration that the vehicle can achieve, and then this process loses a portion of the vehicle dynamics.
Step four, predicting the maximum gear
When calculating the acceleration curve of the vehicle, presetting the maximum gear of the off-road vehicle according to any accelerator opening degree alpha1Rolling resistance coefficient f1And a gradient beta1Calculating the maximum speed and the corresponding gear i of the cross-country vehicle under the running conditionmax_t(α1,β1,f1) The maximum acceleration a which can be reached by the vehicle under the gear is obtainedmax_t(α1,β1,f1) Set up ad_minIs an acceleration threshold. When i ismax_t(α1,β1,f1) The following judgment is made when the value is greater than 1: if amax_t(α1,β1,f1)≥ad_minThen the preset maximum gear of the cross-country vehicle under the running condition is imax_d(α1,β1,f1)＝imax_t(α1,β1,f1) (ii) a If amax_t(α1,β1,f1)＜ad_minIf the speed of the off-road vehicle is higher than the maximum speed, the off-road vehicle is difficult to maintain the acceleration condition, the speed of the vehicle is reduced and the gear-shifting probability is greatly improved due to the complex change of the off-road surface, and the vehicle is prohibited from being lifted into the gear in order to reduce the gear-shifting times, avoid the power loss caused by the power interruption in the gear-shifting process and inhibit the vehicle from being lifted into the gear imax_tThe maximum gear of the off-road vehicle is preset as imax_d(α1,β1,f1)＝max{1,imax_t(α1,β1,f1)-1}。
Step five, power gear shifting method
When the off-road vehicle is accelerated, the throttle opening of the vehicle is alphakAnd obtaining the rolling resistance coefficient f of the running of the off-road vehicle according to the road condition in a certain distance ahead when the current gear is gekAnd a gradient betakSatisfy fk∈ΩfAnd betak∈Ωβ. According to the gear shifting point vehicle speed v obtained in the step twoi_up_con(alpha, beta, f) obtaining the upshift speed v of the off-road vehicle under the acceleration condition at the timege_up_con(αk,βk,fk) (ii) a Further obtaining the maximum gear i of the vehicle at the moment according to the prediction method of the step fourmax_d(αk,βk,fk) Judging the current gear ge of the off-road vehicle: if ge is more than or equal to imax_d(αk,βk,fk) Off-road vehicles will not be upshifted; if ge is less than imax_d(αk,βk,fk) Judging the speed of the cross-country vehicle, and when the speed reaches the gear-up point, judging the speed v of the cross-country vehiclege_up_con(αk,βk,fk) When so, the vehicle is upshifted.
When the off-road vehicle decelerates, the current gear is ge, and the vehicle speed v required by the gear to be shifted up is v according to the current speed, the current deceleration and the current gearuEstimating the current vehicle speed v of the vehicledVehicle speed v for decelerating to the current gearuRequired time TsdAnd the distance L the vehicle will travel during this timesd. Observing the road condition in a distance ahead, recording the distance maintained by the section as the length of the deceleration road section, and using L1And (4) showing.
Definition of Ld_maxFor presetting the length of the gear-shifting delay deceleration road section, the length L of the current deceleration road section1The following judgment is made: if L is1-Lsd< 0, i.e. the deceleration road section length is less than LsdIf the vehicle is running in the high gear, the off-road vehicle is not in the down shift operation; if 0 is less than or equal to L1-Lsd≤Ld_maxI.e. deceleration road section length greater than LsdBut over part of the lengthIf the gear shifting delay speed is less than the length of the preset gear shifting delay speed reducing road section, the gear shifting point speed is obtained according to a gear shifting rule with gear shifting delay, namely the gear shifting point speed is v(ge-1)_down_d＝v(ge-1)_down_tIf L is1-Lsd＞Ld_maxIf the length of the deceleration road section is larger than the length of the preset gear-shifting delay deceleration road section, which indicates that the road in front of the off-road vehicle is continuously bad, the speed of the gear-shifting point is set as the corresponding speed of the gear-shifting point which is shifted into the current gear, namely v(ge-1)_down_d＝v(ge-1)_upTherefore, the cross-country vehicle can be lowered into a low gear in time, the target of the maximum acceleration is always met, and the loss of the vehicle dynamic property in the process of waiting for the vehicle to decelerate to the gear-shifting delayed gear-lowering point speed is avoided.
For the change of the accelerator opening degree of an off-road vehicle caused by road bump under the condition of an off-road rugged road, the following strategy is adopted in order to avoid unexpected gear change: taking the statistical average value of the accelerator opening of the current section of stable road as the current accelerator opening alphadriJudging the reason of the future change of the accelerator opening degree, taking the intensity of the change of the vertical acceleration of the vehicle as a judgment basis, and if the vertical acceleration of the vehicle is not less than a set threshold value az0And the absolute value of the change rate of the vertical acceleration is not less than
Figure BDA0002497670320000031
And the amplitude delta alpha of the change of the opening degree of the acceleratordriLess than a set value Δ αdri0The change of the accelerator opening is caused by vehicle bump due to uneven road surface, and the current accelerator opening alpha is takendriThe fixed value is used as a control parameter to carry out gear shifting control; if the vertical acceleration of the vehicle changes stably, namely the vertical acceleration of the vehicle is lower than a set threshold value az0Or absolute value of rate of change of vertical acceleration lower than
Figure BDA0002497670320000032
The accelerator opening change is considered to be generated by a driver, and the actual accelerator opening is taken as a control parameter to carry out gear shifting control.
Advantageous effects
1. The power gear control strategy of the off-road vehicle transmission fully considers the deviation of the vehicle speed at the optimal power upshift point caused by the change of the road resistance coefficient and the change of the gradient of the running road;
2. considering that the conditions of the off-road are complex and changeable, and the off-road vehicle may not provide enough driving force to enable the vehicle to effectively keep running under the highest gear obtained by theoretical calculation, the control strategy of the invention provides a preset highest gear for limiting the upshifting operation of the off-road vehicle;
3. considering that the length of the continuous distance of the speed reducing road condition of the off-road is different, and for the condition that the speed reducing road condition is continuous and long, the speed of the gear-shifting point is set to be equal to the speed of the gear-shifting point, the gear-shifting delay is cancelled, the timely gear-shifting in the speed reducing process of the off-road vehicle is realized, and the power loss caused by the existence of the gear-shifting delay is avoided;
4. through observation of the vertical acceleration and the accelerator opening, the change reason of the accelerator opening is judged to be caused by vehicle bump due to uneven road surface or caused by the change of intention of a driver, so that accelerator opening control parameters are determined, and gear control is performed.
Drawings
FIG. 1 is a schematic flow diagram of a pre-calculation module for a off-road vehicle transmission dynamics control strategy in accordance with the present invention;
FIG. 2 is a flow chart illustrating a proposed off-road vehicle transmission dynamics control strategy.
Detailed Description
The following provides a detailed description of a specific embodiment of the off-road vehicle transmission dynamics control strategy in accordance with the present invention, with reference to the accompanying drawings and examples.
A method of controlling a power shift of an automatic transmission for an off-road vehicle, as shown in FIG. 2; the method comprises the following steps:
step one, calculating a double-parameter gear-up rule by taking the maximum acceleration as a target through parameters; as shown in fig. 1;
(1) obtaining basic parameters of the off-road vehicle, including engine power characteristics, transmission system structure parameters, vehicle mass and the like, wherein the off-road vehicle is supposed to have N forward gears, the accelerator opening degree is represented by alpha, and alpha belongs to (0, 1);
(2) obtaining an empirical value f of the rolling resistance coefficient of a good road surface based on good straight road surface driving conditions0Slope value beta of peace road surface0At this time, beta0＝0；
(3) Calculating the acceleration under different accelerator opening degrees and each gear of the transmission, extracting the vehicle speed corresponding to the intersection point of the acceleration curves of two adjacent gears to be used as the vehicle speed corresponding to the gear shifting point, and if the acceleration curves of the adjacent gears do not have the intersection point, taking the maximum vehicle speed which can be reached by the low gear as the vehicle speed of the gear shifting point, thereby obtaining a two-parameter gear-up rule with the acceleration as the maximum power target;
(4) the vehicle speed at the shift point of shifting from the i (i-1 to N-1) gear to the i +1 gear is denoted as vi_up(α,β0,f0)；
(5) Considering the change of the rolling resistance coefficient in the driving process of the off-road vehicle, calculating and obtaining a gear shifting rule considering the influence of the driving condition according to the changed rolling resistance coefficient: let f be the coefficient of rolling resistance, Ω, which variesfIs a value set of the rolling resistance coefficient, f belongs to omegafF is taken as the set omegafThe slope value is the slope value beta of the level road surface0；
(6) Repeating the step (3), obtaining a new dynamic two-parameter upshift rule by considering the shift point vehicle speed deviation caused by the change of the road rolling resistance coefficient, and recording the shift point vehicle speed considering the change of the rolling resistance coefficient, which is increased from the i (i-1-N-1) gear to the i +1 gear, as vi_up_f(α,β0,f)；
(7) Considering the gradient change of the running road of the off-road vehicle, calculating and obtaining a gear shifting rule considering the influence of the working condition of the ramp according to the changed gradient value: let beta be the varying road slope, omegaβIs a value set of gradient values, beta is a set omegaβ(ii) any of the above-mentioned values,
the rolling resistance coefficient is the rolling resistance coefficient value f of a good road surface0；
(8) Repeating step (3) taking into account the effect caused by the change in the gradient valueObtaining a new dynamic two-parameter upshift rule, and recording the gear shifting point vehicle speed considering gradient change for shifting from i (i is 1-N-1) to i +1 as vi_up_β(α,β,f0)；
(9) When the rolling resistance coefficient and the gradient are simultaneously changed in the driving condition of the off-road vehicle, the rolling resistance coefficient is set to be f (f belongs to omega)f) The gradient value is beta (beta is epsilon to omega)β) And (3) repeating the step (3), taking the shift point vehicle speed deviation caused by the simultaneous change of the two parameters into consideration, obtaining a new dynamic two-parameter upshift rule, and recording the shift point vehicle speed which is raised from the i (i-1-N-1) gear to the i +1 gear and takes the rolling resistance coefficient and the gradient into consideration and changes simultaneously as vi_up_con(α,β,f)；
(10) Presetting the maximum gear of the off-road vehicle under a certain determined running condition: let the throttle opening be alpha1Rolling resistance coefficient of f1And a gradient of beta1The preset maximum gear is imax_d(α1,β1,f1). According to the determined running condition, calculating the acceleration corresponding to different vehicle speeds under each gear to obtain the maximum vehicle speed of the off-road vehicle under the running condition and the gear i used when the maximum vehicle speed is reachedmax_t(α1,β1,f1) Then, the longitudinal acceleration corresponding to different vehicle speeds under the gear is counted to obtain the gear imax_t(α1,β1,f1) Maximum acceleration a obtainable for a cross-country vehiclemax_t(α1,β1,f1) (ii) a Let ad_minAs acceleration threshold, when imax_t(α1,β1,f1) When > 1, the following judgment is made: if amax_t(α1,β1,f1)≥ad_minIf the preset maximum gear of the cross-country vehicle under the driving condition is the gear corresponding to the maximum vehicle speed calculated theoretically, i.e. imax_d(α1,β1,f1)＝imax_t(α1,β1,f1) (ii) a If amax_t(α1,β1,f1)＜ad_minThen, the theory of the cross-country vehicle rising is explainedWhen the calculated maximum vehicle speed corresponds to a gear, the cross-country vehicle is difficult to maintain an acceleration condition, the probability of deceleration and gear reduction of the vehicle is greatly improved due to complex change of a cross-country road surface, and the vehicle is prohibited from rising into the gear i in order to reduce the gear shifting times and avoid power loss caused by power interruption in the gear shifting processmax_tThe maximum gear of the off-road vehicle is preset as the lower first gear of the gear corresponding to the theoretical calculated maximum vehicle speed, i.e. imax_d(α1,β1,f1)＝max{1,imax_t(α1,β1,f1)-1}；
(11) In order to reduce the number of gear shifts during the driving of a vehicle and to avoid cyclic gear shifts, a downshift schedule is generally designed with an appropriate shift delay Δ ν based on an upshift schedulei_udLet the vehicle speed at the shift point where the i (i-2-N) gear is shifted down to the i-1 gear be denoted as vi-1_down_tThen, according to the shift delay: v. ofi-1_down_t＝vi_up-Δvi_ud。
The steps provide a parameter basis for control of the off-road vehicle transmission, and the parameter basis comprises an upshift law with the acceleration as the maximum dynamic target, a preset maximum driving gear of the off-road vehicle and a downshift law considering the gear shifting delay.
For an off-road vehicle in the process of running, acquiring running parameters of the vehicle comprises the following steps: current vehicle speed v, current vehicle acceleration a, current vehicle transmission gear ge, accelerator opening alphaktCoefficient of rolling resistance fk(fk∈Ωf) Slope beta ofk(βk∈Ωβ) Vertical acceleration a of the vehiclez. According to the running parameters of the off-road vehicle, the optimal gear is determined through the following transmission dynamic control strategy, wherein the control strategy is as follows:
1) for the change of the accelerator opening degree of an off-road vehicle caused by road bump under the condition of an off-road rugged road, the following strategy is adopted in order to avoid unexpected gear change: taking throttle opening of current stable road sectionStatistical average as driver intent αdri(ii) a Judging the change reason of the future accelerator opening change by the vertical acceleration a of the vehiclezThe intensity of the change is used as a judgment basis: if the vertical acceleration of the vehicle changes violently, the change of the accelerator opening is considered to be caused by the vehicle bump caused by the uneven road surface, so that the driver intends to alphadriThe fixed value is used as a control parameter to carry out gear shifting control, and the accelerator opening degree control parameter is alphak＝αdri(ii) a If the vertical acceleration of the vehicle does not change violently, the change of the accelerator opening is considered to be caused by the driving intention of the driver, the actual accelerator opening is used as a control parameter to carry out gear shifting control, and the accelerator opening control parameter is alphak＝αkt。
2) Judging the current running state of the off-road vehicle according to the acceleration of the vehicle, and entering the steps 3) -4) if the off-road vehicle is in an acceleration or uniform speed state; if the off-road vehicle is in a deceleration state, entering the steps 5) to 7);
3) the vehicle speed v obtained in the step one and taking into account the simultaneous change of the rolling resistance coefficient and the gradient of the shift point of the gear shifting from the i (i-1 to N-1) to the i +1 geari_up_con(α, β, f) a vehicle speed at an upshift point of the off-road vehicle under the current driving conditions is vge_up_con(αk,βk,fk)；
4) According to the method in the step one and the current running parameters, obtaining a preset maximum gear i of the off-road vehicle under the current running conditionmax_d(αk,βk,fk) Judging the current gear ge of the vehicle: if ge is more than or equal to imax_d(αk,βk,fk) The off-road vehicle will not perform an upshift regardless of vehicle speed; if ge is less than imax_d(αk,βk,fk) And then judging the speed of the off-road vehicle: if the vehicle speed reaches the gear-up point, v is more than or equal to vge_up_con(αk,βk,fk) The off-road vehicle upshifts, otherwise no upshifts.
5) Estimating the speed of the cross-country vehicle from the current vehicle according to the current gear, the current vehicle speed, the current vehicle deceleration and the vehicle speed required for ascending to the current gearThe time T required for the speed to be decelerated to the speed for rising into the current gearsdAnd the distance L the vehicle will travel during this timesd(ii) a And observing the road condition in a distance in front of the running off-road vehicle, recording the distance maintained by the section as the length of the deceleration road section, and using L1And (4) showing. Is provided with Ld_maxPresetting the length of a gear shifting delay deceleration road section;
6) for the length L of the deceleration road section1The following judgment is made: if L is1-LsdIf < 0, the length of the deceleration road section is less than LsdThe off-road vehicle will keep running in high gear without down-shift operation; if 0 is less than or equal to L1-Lsd≤Ld_maxThe length of the deceleration road section is greater than LsdIf the length of the exceeding part is smaller than the length of the preset gear-shifting delay speed-reducing road section, the speed of the gear-shifting point is obtained according to a gear-shifting rule with gear-shifting delay, namely the speed of the gear-shifting point is v(ge-1)_down_d＝v(ge-1)_down_t(ii) a If L is1-Lsd＞Ld_maxThe length of the deceleration road section exceeds LsdThe length of the road section is larger than the length of the preset gear-shifting delay deceleration road section, which shows that the road in front of the off-road vehicle is continuously bad, and the off-road vehicle should be shifted down ahead of time, so that the speed of the shift-down point is set as the corresponding speed of the shift-up point which is shifted up to the current gear: v. of(ge-1)_down_d＝v(ge-1)_upTherefore, the cross-country vehicle can be lowered into a low gear in time, the target of the maximum acceleration is always met, and the loss of the vehicle dynamic property in the process of waiting for the vehicle to decelerate to a downshift point speed with delayed gear shifting is avoided;
7) judging the speed of the cross-country vehicle under the deceleration working condition, and when the speed reaches the downshift point, meeting the condition that v is less than or equal to v(ge-1)_down_dThe off-road vehicle is downshifted, otherwise the vehicle is not downshifted.
The reason for the change of the accelerator opening degree is judged through the change of the vertical acceleration of the vehicle, so that the wrong gear shifting caused by the bumpiness of the road is avoided. According to the road driving condition, the maximum gear of the off-road vehicle under the current driving condition is determined, the change of a gear shifting rule caused by the driving resistance coefficient and the gradient change is further considered, frequent gear shifting and wrong gear shifting caused by the change of the driving condition are effectively avoided, the gear shifting times and the power loss in the gear shifting process are effectively reduced, the optimal dynamic gear control of the off-road vehicle is realized, and the dynamic performance of the off-road vehicle is improved.
In summary, according to the proposed off-road vehicle transmission control strategy, optimal power performance is achieved for the off-road vehicle by controlling the transmission gear. The above description is only exemplary of the present invention and should not be taken as limiting the scope of the invention, which is defined by the appended claims and any modifications, equivalents, improvements, etc. that fall within the true spirit and scope of the invention.

Claims (2)

1. A power gear-shifting control method of an automatic transmission of an off-road vehicle is characterized by comprising the following steps: the method comprises the following steps:
step one, calculating a double-parameter gear-up rule by taking the maximum acceleration as a target through parameters;
the power control strategy of the off-road vehicle transmission takes the acceleration of the off-road vehicle as a core control parameter and takes the maximum acceleration of the off-road vehicle reaching the constraint condition as a control target, and the specific technical scheme is as follows:
based on the driving parameters of the vehicle under the good straight road surface condition, including the characteristics of a power device, the transmission ratio parameters of a transmission system, the rolling resistance coefficient of a road and the quality of the whole vehicle, the acceleration of the transmission under different accelerator opening degrees under each gear is calculated, the vehicle speed corresponding to the intersection point of the acceleration curves of two adjacent gears is extracted and used as the corresponding vehicle speed of the gear shifting point, if the acceleration curves of the adjacent gears do not have the intersection point, the maximum vehicle speed which can be reached by the low gear is taken as the corresponding vehicle speed of the gear shifting point, the two-parameter gear-up rule with the acceleration as the maximum dynamic target is obtained, and the vehicle speed of the gear shifting point which is increased from the i geari_up(α,β0,f0) Wherein, alpha is the accelerator opening degree, and alpha belongs to (0, 1)]；β0For straight road slopes, i.e. beta0＝0；f0The rolling resistance coefficient of a good road surface;
step two, respectively changing the rolling resistance coefficient and the gradient of the road to obtain a new dynamic upshift rule;
respectively changing the rolling resistance coefficient and the gradient of a road, calculating a new dynamic two-parameter gear-up rule to obtain the gear-shifting point vehicle speed deviation caused by the change of the rolling resistance coefficient of the road, and recording the gear-shifting point vehicle speed considering the change of the rolling resistance coefficient when the gear i is shifted into the gear i +1 as vi_up_f(α,β0F), where f is the coefficient of varying rolling resistance, f ∈ ΩfF is taken as the set omegafAny value of (1); similarly, the speed deviation of the gear shifting point caused by gradient change is obtained, and the speed of the gear shifting point which is raised from the i gear to the i +1 gear and considers the gradient change is recorded as vi_up_β(α,β,f0) Where β is the varying road grade, β ∈ ΩβBeta is taken as set omegaβAny value of (1); when the rolling resistance coefficient and the gradient are changed simultaneously, the speed of the corresponding gear shifting point from the i gear to the i +1 gear is recorded as vi_up_con(α,β,f)；
Step three, downshifting
In order to reduce the number of gear shifts during the driving of the vehicle and to avoid cyclic gear shifts appropriately, for the design of the downshift schedule, a shift delay Deltav is set on the basis of the upshift schedulej_udThe vehicle speed at the shift point of the gear from the gear j to the gear j-1 is recorded as vj-1_down_tThen v isj-1_down_t＝vi_up-Δvj_ud(ii) a Therefore, when the vehicle decelerates to the down-shift, the vehicle speed is less than that when the corresponding gear is shifted up; upshift vehicle speed vi_upIf the condition of maximum acceleration is met, in the process that the vehicle decelerates to the downshift point, the acceleration of the vehicle is smaller than the maximum acceleration which can be achieved by the vehicle, and part of the vehicle dynamic property is lost in the process;
step four, predicting the maximum gear
When calculating the acceleration curve of the vehicle, presetting the maximum gear of the off-road vehicle according to any accelerator opening degree alpha1Rolling resistance coefficient f1And a gradient beta1Calculating the maximum speed and the corresponding gear i of the cross-country vehicle under the running conditionmax_t(α1,β1,f1) To obtain the gearMaximum acceleration a that can be achieved by the lower vehiclemax_t(α1,β1,f1) Set up ad_minIs an acceleration threshold; when i ismax_t(α1,β1,f1) The following judgment is made when the value is greater than 1: if amax_t(α1,β1,f1)≥ad_minThen the preset maximum gear of the cross-country vehicle under the running condition is imax_d(α1,β1,f1)＝imax_t(α1,β1,f1) (ii) a If amax_t(α1,β1,f1)＜ad_minIf the speed of the off-road vehicle is higher than the maximum speed, the off-road vehicle is difficult to maintain the acceleration condition, the speed of the vehicle is reduced and the gear-shifting probability is greatly improved due to the complex change of the off-road surface, and the vehicle is prohibited from being lifted into the gear in order to reduce the gear-shifting times, avoid the power loss caused by the power interruption in the gear-shifting process and inhibit the vehicle from being lifted into the gear imax_tThe maximum gear of the off-road vehicle is preset as imax_d(α1,β1,f1)＝max{1,imax_t(α1,β1,f1)-1}；
Step five, power gear shifting method
When the off-road vehicle is accelerated, the throttle opening of the vehicle is alphakAnd obtaining the rolling resistance coefficient f of the running of the off-road vehicle according to the road condition in a certain distance ahead when the current gear is gekAnd a gradient betakSatisfy fk∈ΩfAnd betak∈Ωβ(ii) a According to the gear shifting point vehicle speed v obtained in the step twoi_up_con(alpha, beta, f) obtaining the upshift speed v of the off-road vehicle under the acceleration condition at the timege_up_con(αk,βk,fk) (ii) a Further obtaining the maximum gear i of the vehicle at the moment according to the prediction method of the step fourmax_d(αk,βk,fk) Judging the current gear ge of the off-road vehicle: if ge is more than or equal to imax_d(αk,βk,fk) Off-road vehicles will not be upshifted; if ge is less than imax_d(αk,βk,fk) Then for the speed of the off-road vehicleJudging that the vehicle speed v reaches the gear-up pointge_up_con(αk,βk,fk) When the vehicle is in gear;
when the off-road vehicle decelerates, the current gear is ge, and the vehicle speed v required by the gear to be shifted up is v according to the current speed, the current deceleration and the current gearuEstimating the current vehicle speed v of the vehicledVehicle speed v for decelerating to the current gearuRequired time TsdAnd the distance L the vehicle will travel during this timesd(ii) a Observing the road condition in a distance ahead, recording the section as the length of a deceleration road section, and using L1Represents;
definition of Ld_maxFor presetting the length of the gear-shifting delay deceleration road section, the length L of the current deceleration road section1The following judgment is made: if L is1-Lsd< 0, i.e. the deceleration road section length is less than LsdIf the vehicle is running in the high gear, the off-road vehicle is not in the down shift operation; if 0 is less than or equal to L1-Lsd≤Ld_maxI.e. deceleration road section length greater than LsdIf the length of the exceeding part is smaller than the length of the preset gear-shifting delay speed-reducing road section, the speed of the gear-shifting point is obtained according to a gear-shifting rule with gear-shifting delay, namely the speed of the gear-shifting point is v(ge-1)_down_d＝v(ge-1)_down_t(ii) a If L is1-Lsd＞Ld_maxIf the length of the deceleration road section is larger than the length of the preset gear-shifting delay deceleration road section, which indicates that the road in front of the off-road vehicle is continuously bad, the speed of the gear-shifting point is set as the corresponding speed of the gear-shifting point which is shifted into the current gear, namely v(ge-1)_down_d＝v(ge-1)_upTherefore, the cross-country vehicle can be lowered into a low gear in time, the target of the maximum acceleration is always met, and the loss of the vehicle dynamic property in the process of waiting for the vehicle to decelerate to the gear-shifting delayed gear-lowering point speed is avoided.
2. The method of claim 1, wherein: for the change of the accelerator opening degree of an off-road vehicle caused by road bump under the condition of an off-road rugged road, the following strategy is adopted in order to avoid unexpected gear change: taking a current section of stable roadTaking the statistical average value of the accelerator opening of the road as the current accelerator opening alphadriJudging the reason of the future change of the accelerator opening degree, taking the intensity of the change of the vertical acceleration of the vehicle as a judgment basis, and if the vertical acceleration of the vehicle is not less than a set threshold value az0And the absolute value of the change rate of the vertical acceleration is not less than
Figure FDA0002906419190000031
And the amplitude delta alpha of the change of the opening degree of the acceleratordriLess than a set value Δ αdri0The change of the accelerator opening is caused by vehicle bump due to uneven road surface, and the current accelerator opening alpha is takendriThe fixed value is used as a control parameter to carry out gear shifting control; if the vertical acceleration of the vehicle changes stably, namely the vertical acceleration of the vehicle is lower than a set threshold value az0Or absolute value of rate of change of vertical acceleration lower than
Figure FDA0002906419190000041
The accelerator opening change is considered to be generated by a driver, and the actual accelerator opening is taken as a control parameter to carry out gear shifting control.
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