CN116201891A - Vehicle automatic transmission out-of-step gear shifting decision method based on predicted driving condition dynamic optimization - Google Patents
Vehicle automatic transmission out-of-step gear shifting decision method based on predicted driving condition dynamic optimization Download PDFInfo
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Abstract
The invention discloses a vehicle automatic transmission gear shifting decision method based on prediction running condition dynamic optimization, which comprises the following steps: step one, at a certain time t 0 The override shift decision module receives a shift enabling signal with a value of 1 sent by the shift logic module, and is enabled to start calculation; step two, calculating the predicted termination time t of the future driving working condition by the override gear shift decision module f The method comprises the steps of carrying out a first treatment on the surface of the Step three, obtaining a predicted termination time t f Then, the out-of-step gear shifting decision module starts to calculate an objective function J of the out-of-step gear shifting scheme and the step-by-step gear shifting scheme in the prediction time; step four, if the objective function J of the step-up gear shifting scheme Override An objective function J less than a step-by-step shift scheme Step The out-of-step gear shifting decision module decides that out-of-step gear shifting is needed; objective function J for skip-step shift scheme Override Objective function J greater than step-by-step shift scheme Step The override shift decision module decides that the step-by-step shift is neededAnd (3) a baffle.
Description
Technical Field
The invention relates to the technical field of automobile automatic transmission control systems, in particular to a vehicle automatic transmission override gear shifting decision method based on prediction driving working condition dynamic optimization.
Background
The optimal control of the gear of the automatic gearbox is an important link for realizing multi-objective compromise of dynamic property, economical efficiency and driving comfort by adjusting the distribution of operating working condition points of an engine of a heavy commercial vehicle.
The heavy commercial vehicle has the characteristics of more emphasis on fuel economy and the like due to the large vehicle load change range and complex driving environment, and the number of gears of the automatic transmission matched with the heavy commercial vehicle is often large. The number of gears is more, so that the vehicle can show better traction performance, the acceleration and climbing capacity of the vehicle are improved, and the probability of the engine working in a low fuel consumption rate area can be increased, so that the transportation cost of the commercial vehicle is reduced.
However, the greater number of gears of the automatic transmission of the heavy-duty commercial vehicle brings advantages and also brings adverse effects, such as more gear shifting times and more frequent gear shifting of the heavy-duty commercial vehicle with more gears than the common vehicle in the same vehicle speed change interval. Currently, most of automatic transmissions matched with heavy commercial vehicles are electronic control mechanical automatic transmissions (AMTs), and because the AMTs have power interruption in the gear shifting process, the frequent gear shifting can bring power loss problems, the power loss can be particularly serious when the vehicle runs in a slope, and in addition, the driving comfort of a driver can be greatly reduced due to frequent gear shifting. Therefore, when the speed of the vehicle changes rapidly, the time that the vehicle is kept in a certain gear is short, the time that the engine works in a dominant rotating speed interval in the gear is also short, and compared with the adverse effect caused by frequent gear shifting, if the gear shifting can span a plurality of gears at the moment, the gear shifting times can be reduced, so that the power loss in the gear shifting process is reduced, and in addition, the driving comfort of a driver can be improved.
The over-step shifting has obvious effects of reducing the shifting times and reducing the power loss, but after each over-step shifting, the rotating speed working range of the engine is enlarged relative to the step-by-step shifting, and the potential hazards possibly brought are that the fuel consumption rate and the torque are deteriorated in part of the rotating speed range, and the concrete condition depends on the torque characteristic and the oil consumption characteristic of the engine. The decision of an out-of-step shift is therefore critical, requiring a comprehensive consideration of the fuel economy, power and driving comfort of the driver of the vehicle to make a reasonable and satisfactory decision result.
The existing decision method of the gear shift is mostly a rule-based decision method. For example, literature (Cong Xiaoyan. Heavy truck AMT automatic shift strategy and key parameter study [ D ]. University of shandong, 2017.) establishes a gear shift decision method under different loads based on acceleration, and decides whether gear shift is performed by calibrating different acceleration rules under different loads. The vehicle acceleration represents the speed of the vehicle speed change, the vehicle speed change is fast when the acceleration is large, the time that the vehicle is maintained in a certain gear is short, the vehicle is indeed suitable for gear shifting beyond the level at the moment, so that the decision of guiding gear shifting beyond the level according to the acceleration establishment rule is a feasible scheme, but the acceleration in the acceleration process is greatly affected by the vehicle load and the gear, if the acceleration threshold values under different loads are calibrated to serve as decision basis, the workload is large, the optimization target in the calibration process is too subjective, and the calibration result can not achieve the aims of improving the power performance and reducing the power loss. Therefore, if the vehicle longitudinal dynamics theory is tried to be started, the performance of the over-level gear shifting and the step-by-step gear shifting in economy, power performance and driving comfort are comprehensively compared, and the over-level gear shifting decision method based on the model is of great significance for solving the problem caused by the multi-gear AMT step-by-step gear shifting of the heavy commercial vehicle.
Disclosure of Invention
The invention aims to solve the problems of complex gear shifting decision process and large calibration workload in the prior art, and provides a gear shifting decision method for a vehicle automatic transmission based on dynamic optimization of predicted driving conditions. It should be noted that the function of the gear shifting logic module is to solve the problem of when the vehicle shifts gears to several gears in the running process, and judge whether the current running condition of the vehicle meets the gear shifting condition according to the real-time information of the opening degree of the accelerator pedal of the driver, the speed, the actual gear and the like. The invention aims at the out-of-step gear shifting behavior in the acceleration process, and the out-of-step level is set to be 1 level, namely 2 levels are shifted at one time. Therefore, the present invention determines whether the current vehicle running condition satisfies the upshift condition. In the invention, whether the gear shift is the skip gear shift or the step-by-step gear shift is determined by comparing the comprehensive performance of the vehicle on economy, dynamic performance and driving comfort under different schemes, in particular by comparing the comprehensive performance advantages and disadvantages of different schemes in the same time (cost function expression is used in the patent). Specifically, in the aspect of economy, hundred kilometers of oil consumption in the predicted driving working condition is taken as a quantization index; in the dynamic aspect, the terminal speed in the predicted running working condition is taken as a quantization index; in terms of driving comfort, a certain frequent shift penalty is given to a step-by-step shift scheme as a quantization index. The final objective function J is a weighted sum of hundred kilometers of oil consumption, terminal speed and frequent gear shifting punishment in the predicted driving working condition. And each quantization index has a corresponding weight coefficient, so that the override shift decision of the expected optimization direction can be conveniently realized.
The technical scheme adopted for realizing the purpose of the invention is as follows:
a vehicle automatic transmission gear shift decision method based on prediction driving condition dynamic optimization comprises the following steps:
step one, at a certain time t 0 The override shift decision module receives a shift enabling signal with a value of 1 sent by the shift logic module, and is enabled to start calculation;
step two, calculating the predicted termination time t of the future driving working condition by the override gear shift decision module f ；
Step three, obtaining a predicted termination time t f Later, the override shift decision module is turned onStarting to calculate the objective function J of the step-up gear shifting scheme and the step-by-step gear shifting scheme in the prediction time, wherein the objective function of the step-up gear shifting scheme is J Override The objective function of the step-by-step shift scheme is J Step ；
Step four, if the objective function J of the step-up gear shifting scheme Override An objective function J less than a step-by-step shift scheme Step The out-of-order gear shifting decision module decides out-of-order gear shifting, and outputs an out-of-order gear shifting enabling signal with the value of 1 to the gear shifting logic module; objective function J for skip-step shift scheme Override Objective function J greater than step-by-step shift scheme Step And the out-of-order gear shifting decision module decides that the gear shifting is needed step by step, outputs an out-of-order gear shifting signal with the value of 0 to the gear shifting logic module, and after receiving out-of-order gear shifting enabling signals with different values, the gear shifting logic module starts to take corresponding upshift measures, out-of-order upshift or step-by-step upshift, and finally outputs a corresponding target gear.
In the above technical solution, in the first step, if at t 0 The moment gear shifting logic module judges that the gear shifting condition is met, and starts to send a gear shifting enabling signal with a value of 1 to the out-of-order gear shifting decision module so as to enable the out-of-order gear shifting decision module; and at other moments when the upshift condition is not met, the gear shifting enabling signal value is 0, and the gear shifting decision module cannot be enabled.
In the above technical solution, in the second step, the time t is terminated f Calculated by the following steps:
vehicle speed v passing time t0 0 Calculating the predicted initial time t 0 Vehicle speed of +x
Vehicle speed v 0 Can be directly obtained in real time, and the time t is time t 0 By time t 0 The wind resistance caused by the speed drop in the power interruption process of +x is ignored, and the speed v is directly used 0 The calculated air resistance is taken as the air resistance when the power of xs is interrupted in the future, and the following are: />
Wherein delta is a rotational mass coefficient which is mainly related to the vehicle weight, the wheels, the rotational inertia of the engine flywheel and the transmission gear ratio, m is the vehicle mass, g is the gravitational acceleration, f is the rolling resistance coefficient, theta is the road gradient, C d The wind resistance coefficient is that A is the windward area;
iterative solution using vehicle longitudinal dynamics equations
Still further solve v (t):
the vehicle longitudinal dynamics equation is:
wherein delta is a rotation mass coefficient, T e (t) is the engine output torque at time t, i g I is the transmission ratio in gear n+1 0 For the transmission ratio of the main speed reducer, eta is the transmission efficiency of a transmission system, r is the rolling radius of wheels, v (t) is the speed of the vehicle at the moment t, and the unit is m/s, and the initial moment t is predicted 0 +x，
Acceleration at time t;
in each iterative solving process, the calculation mode of the vehicle speed v (t) is as follows:
wherein dt is an iteration step length of the iterative solution of the vehicle speed;
engine output torque T e (t) is a parameter expressed by accelerator pedal manipulation, and the prediction model of the accelerator pedal is as follows:
wherein alpha (t) is accelerator pedal information, alpha (0) is accelerator pedal opening of the predicted initial moment, and the accelerator pedal opening can be directly obtained in real time and is equal to the moment t of the gear shifting logic module 0 The acquired throttle opening alpha c The change rate of the accelerator opening at the initial time is obtained in real time according to alpha (0), and is equal to (alpha (0) -alpha (0-delta T))/delta T, wherein delta T is the scheduling period of the gear shifting logic module, and alpha (0-delta T) is the time (T) 0 - Δt) the acquired accelerator opening. Mu is the decay rate, defined as mu=α c /(2t′ f ) Wherein t' f As the termination time of the accelerator opening prediction, the discrete step length T of the accelerator opening prediction algorithm s The iteration step dt is the same as the vehicle speed;
engine output torque T e (t) also depends on the engine speed n e (t) there are:
T e (t)＝f(n e (t)，α(t))
engine speed n e (t) can be calculated by calculating the vehicle speed v (t) of each iteration process, and comprises the following steps:
wherein i is g For gear ratios corresponding to gear steps of a step-by-step shift scheme, i.e. gear ratios corresponding to n+1 gear, i 0 R is the wheel rolling radius, 0.1047 is pi/30, and pi is the circumference ratio, which is the final drive ratio.
At each vehicle speed iteration, the vehicle speed result v (t) is increased by the vehicle speed threshold v of n+1 gear and n+2 gear (n+1)-(n+2) Comparing, and the vehicle speed result v (t) is not less than v after a certain iteration is finished (n+1)-(n+2) Recording the iteration times m from the beginning to the moment, and then the moment t f -x is found as: t is t f -x＝m*dt+t 0 +x；
Thus, the predicted termination time t is obtained f ：t f ＝m*dt+t 0 +x+x。
In the above technical solution, in the third step, the specific expression of the objective function is:
wherein J is Eco Is used for the fuel consumption of hundred kilometers,
for the terminal speed of the vehicle, J Shift To address shift penalty for a step-by-step shift scheme, a J is provided in the present invention Shift 1, J of the skip-step shift scheme Shift 0->
The weight coefficients are respectively the economical efficiency, the dynamic performance and the driving comfort.
In the above technical solution, after the iterative computation is completed, at the predicted termination time t f The terminal speed of the over-gear shifting scheme can be obtained
In the above-mentioned technical scheme, the method comprises the steps of,
in which Q Fuel (t) is the fuel consumed by the engine in the time range from the moment t to the moment t+dt, and the unit is g and L Dist And (t) is the mileage of the vehicle in the time range from the moment t to the moment t+dt, and the unit is m.
In the above technical solution, for the skip gear shifting scheme, the driving state is kept all the time in the predicted time range, and the iterative calculation is completed by using the dynamic and energy efficiency model of the driving process and is brought into J Eco In the expression, J under the out-of-step gear shifting scheme can be obtained Eco I under an override shift scheme g The gear ratio corresponding to the n+2 gear is set.
In the above technical solution, for a step-by-step shift scheme, there is a driving process and a non-driving process within a predicted time rangeDynamic process, namely finishing iterative calculation of dynamic and energy efficiency models corresponding to the driving process and the non-driving process and introducing the iterative calculation into an expression J Eco In (3), the J under the step-by-step gear shifting scheme can be obtained Eco I under step-by-step gear shifting scheme g The gear ratio corresponding to the n+1 gear is adopted.
In the above technical solution, in the prediction time range, there are kinetic and energy efficiency models for the driving process:
in the above technical solution, in the prediction time range, for the non-driving process, there are kinetic and energy efficiency models:
compared with the prior art, the invention has the beneficial effects that:
1) The invention provides the thought of carrying out the override shift decision by comparing the benefits of different shift strategies based on dynamic and energy efficiency model rolling prediction in a future time window, effectively considers the problem of dynamic loss caused by the interruption of the driving force in the shift process, and ensures that the override shift decision has stronger pertinence.
2) The method provides a multi-objective cost function for comprehensive dynamic performance, economy and driving comfort in a future time window, realizes an idea of automatic optimizing based on a model, and effectively solves the problems that the traditional algorithm depends on a large number of shift tables (MAP) for calibration and has weak adaptability.
Drawings
FIG. 1 is a frame diagram of an override shift decision method of the present invention;
FIG. 2 is a schematic flow chart of a step-up shift decision method of the present invention;
FIG. 3 is an abstract schematic diagram of step two and step three of the override shift decision method of the present invention;
FIG. 4 is a flow chart of step four of the skip shift decision method of the present invention;
FIG. 5 is a gear effect diagram of the over-step shift decision method of the present invention in a next stage of acceleration and deceleration process with greater attention to dynamic performance;
FIG. 6 is a gear effect diagram of the next stage of acceleration and deceleration process of the over-step shift decision method of the present invention with greater attention to economy;
FIG. 7 is a gear effect diagram of the over-step shift decision method of the present invention in a next stage of acceleration/deceleration process with greater attention to driving comfort;
Detailed Description
The present invention will be described in further detail with reference to specific examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
As shown in the frame diagram of fig. 1, the invention provides a vehicle automatic transmission gear shift decision method based on the dynamic optimization of the predicted driving working condition, which specifically comprises the following steps:
step one, as shown in FIG. 2, at a certain time t 0 The override shift decision module receives a shift enabling signal with a value of 1 sent by the shift logic module, the override shift decision module is enabled, and calculation is started:
if at t 0 The moment gear shifting logic module judges that the gear shifting condition is met, and starts to send a gear shifting enabling signal with a value of 1 to the out-of-order gear shifting decision module so as to enable the out-of-order gear shifting decision module; and at other moments when the upshift condition is not met, the gear shifting enabling signal value is 0, and the gear shifting decision module cannot be enabled. The method for determining whether the upshift condition is satisfied by the shift logic module is known in the industry and is well known to the skilled person, and is not described in detail in this patent. The scheduling period for the overall vehicle automatic transmission shift strategy recommends, but is not limited to, 0.02s.
Step two, as shown in FIG. 3, the skip shift decision module calculates the predicted termination time t of the future driving condition f . The vehicle speed curve in the figure represents only the acceleration/deceleration process, and does not represent the vehicle speed change curve in the actual acceleration/deceleration process.
At the moment of timet 0 The skip shift decision module is enabled to begin calculation at time t 0 And +x is the initial time of the driving condition prediction. Where x is the duration of the shift. At time t 0 Starting from the same starting point a (same vehicle speed), the gear of the two schemes is different, assuming that the step-by-step shift scheme is at time t 0 If +x is shifted to n+1, then the upshift scheme is at time t 0 +x is shifted to n+2.
Vehicle speed v passing time t0 0 Calculating the predicted initial time t 0 Vehicle speed of +x
Vehicle speed v 0 Can be directly obtained in real time, and the time t is time t 0 By time t 0 The wind resistance caused by the speed drop in the power interruption process of +x is ignored, and the speed v is directly used 0 The calculated air resistance is taken as the air resistance when the power of xs is interrupted in the future, and the following are:
wherein delta is a rotational mass coefficient which is mainly related to the vehicle weight, the wheels, the rotational inertia of the engine flywheel and the transmission gear ratio, m is the vehicle mass, g is the gravitational acceleration, f is the rolling resistance coefficient, theta is the road gradient, C d The wind resistance coefficient is A, and the windward area is A.
At the predicted initial time t 0 The step-by-step shift scheme is theoretically more accelerating than the skip-step shift scheme because of the lower gear and larger gear ratio, so that the upshift speed threshold of the target gear of the skip-step shift scheme, i.e., the vehicle speed threshold of the n+1 gear upshift n+2 gear, is reached more quickly, as shown by the line segment ab in fig. 3. Therefore, the gradual gear shifting scheme can be iteratively solved at the predicted initial time t according to the longitudinal dynamics equation of the vehicle 0 +x starts accelerating, accelerating how long it has reached the threshold vehicle speed (line jk) for n+1 upshift to n+2. In the iterative solving process, there is a longitudinal direction of the vehicleThe kinetic equation:
wherein delta is a rotation mass coefficient, T e (t) is the engine output torque at time t, i g I is the transmission ratio in gear n+1 0 For the transmission ratio of the main speed reducer, eta is the transmission efficiency of a transmission system, r is the rolling radius of wheels, v (t) is the speed of the vehicle at the moment t, and the unit is m/s, and the initial moment t is predicted 0 +x，
Acceleration at time t.
In each iterative solving process, the calculation mode of the vehicle speed v (t) is as follows:
where dt is the iteration step of the iterative solution of the vehicle speed, the invention recommends, but is not limited to, 0.02s.
Engine output torque T in an iterative process e (t) is the key point of the invention for predicting the driving condition, and the output torque of the engine is a parameter expressed by the operation of an accelerator pedal, so that the accurate prediction of the accelerator opening degree is important, and a prediction model of the accelerator pedal is obtained based on literature (Xiangrui ZE, kaisheng HU, fanbo ME.model predictive control for parallel hybrid electric vehicles with potential real-time capability. Journal of Automotive Safety and energy.2012 Jun 18;3 (2): 165):
wherein alpha (t) is accelerator pedal information, and alpha (0) is accelerator for predicting initial timeThe pedal opening can be directly obtained in real time and is equal to the time t of the gear shifting logic module 0 The acquired throttle opening alpha c For the initial accelerator opening rate, the value equal to (α (0) - α (0- Δt))/Δt can be obtained in real time from α (0), Δt being the scheduling period of the shift logic module, and α (0- Δt) being the time (T) 0 - Δt) the acquired accelerator opening. Mu is the decay rate, defined as mu=α c /(2t′ f ) Wherein t' f For the predicted termination time of the accelerator opening, the invention sets the termination time t' f Recommended, but not limited to, 2s, discrete step T of the accelerator opening prediction algorithm s As with the iterative step dt of the vehicle speed, 0.02s is recommended, but not limited.
At the predicted initial time t 0 +1, after obtaining the accelerator pedal opening of 2s in future, the engine outputs torque T e (t) also depends on the engine speed n e (t) there are:
T e (t)＝f(n e (t)，α(t))
in the engine speed n e (t) can be calculated by calculating the vehicle speed v (t) of each iteration process, and comprises the following steps:
wherein i is g For gear ratios corresponding to gear steps of a step-by-step shift scheme, i.e. gear ratios corresponding to n+1 gear, i 0 R is the wheel rolling radius, 0.1047 is pi/30, and pi is the circumference ratio, which is the final drive ratio.
At each vehicle speed iteration, the vehicle speed result v (t) is increased by the vehicle speed threshold v of n+1 gear and n+2 gear (n+1)-(n+2) Comparing, and the vehicle speed result v (t) is not less than v after a certain iteration is finished (n+1)-(n+2) Recording the iteration times m from the beginning to the moment, and then the moment t f -x is found as: t is t f -x＝m*dt+t 0 +x；
Thus, the predicted termination time t is obtained f ：t f ＝m*dt+t 0 +x+x
Step three, solvingObtaining the predicted termination time t f And then, the out-of-step gear shifting decision module starts to calculate an objective function J of the out-of-step gear shifting scheme and the step-by-step gear shifting scheme in the prediction time:
in the invention, the specific expression of the objective function is:
wherein J is Eco Is used for the fuel consumption of hundred kilometers,
for the terminal speed of the vehicle, J Shift To address shift penalty for a step-by-step shift scheme, a J is provided in the present invention Shift 1, J of the skip-step shift scheme Shift Is 0./>
Weight coefficients of economy, dynamic property and driving comfort respectively, wherein J Eco The expression of (2) is:
in which Q Fuel (t) is the fuel consumed by the engine in the time range from the moment t to the moment t+dt, and the unit is g and L Dist And (t) is the mileage of the vehicle in the time range from the moment t to the moment t+dt, and the unit is m.
Within the predicted time frame, there are kinetic and energy efficiency models for the driving process:
within the predicted time frame, there are kinetic and energy efficiency models for non-driven processes:
for the skip shift scheme, the driving state is kept in the prediction time range, such as a vehicle speed curve ag and a vehicle speed curve gd in fig. 3, and iterative calculation is completed by a dynamic and energy efficiency model of the driving process and is brought into J Eco In the expression, J under the out-of-step gear shifting scheme can be obtained Eco It should be noted that i under the skip-step shift scheme g The gear ratio corresponding to the n+2 gear is set.
After the iterative calculation is completed, at the predicted termination time t f The terminal speed of the over-gear shifting scheme can be obtained
For a step-by-step shift scheme, there is a driving process, such as a vehicle speed curve ab in fig. 3, and a non-driving process, such as a vehicle speed curve bc in fig. 3, within the predicted time range. Each curve segment is carried into a corresponding dynamics and energy efficiency model to complete iterative calculation and is carried into an expression J Eco In (3), the J under the step-by-step gear shifting scheme can be obtained Eco It should be noted that i under a step-by-step shift scheme g The gear ratio corresponding to the n+1 gear is adopted.
After the iterative calculation is completed, at the predicted termination time t f Terminal vehicle speed capable of obtaining step-by-step gear shifting scheme
J obtained by two schemes Eco 、
J Shift The target function expressions of the schemes are carried into, and different weight coefficients are set according to different optimization targets>
Finally, the objective function J under two schemes can be obtained.
Step four, as shown in FIG. 4, in the calculationAfter obtaining the objective function J of the step-by-step gear shifting scheme and the step-by-step gear shifting scheme, comparing the sizes, if the objective function J of the step-by-step gear shifting scheme is obtained Override An objective function J less than a step-by-step shift scheme Step The out-of-order gear shifting decision module decides out-of-order gear shifting, and outputs an out-of-order gear shifting enabling signal with the value of 1 to the gear shifting logic module; objective function J for skip-step shift scheme Override Objective function J greater than step-by-step shift scheme Step And the out-of-order gear shifting decision module decides that the gear shifting is needed step by step, outputs an out-of-order gear shifting signal with the value of 0 to the gear shifting logic module, and after receiving out-of-order gear shifting enabling signals with different values, the gear shifting logic module starts to take corresponding upshift measures, out-of-order upshift or step-by-step upshift, and finally outputs a corresponding target gear.
It should be noted that, in the second step, the vehicle speed curve ab of the step-by-step shift scheme never reaches the threshold v of the vehicle speed of the n+1 shift up to the n+2 shift under some driving conditions (n+1)-(n+2) (line jk), if it is found that the vehicle speed can no longer be increased, the iterative process is stopped, and the upshift enable signal is 0, only the step-by-step shift scheme can be implemented.
Adjusting weight coefficients
And the optimization target is made to pay more attention to the dynamic property, so that a gear effect diagram of the unloaded and fully loaded vehicles in the acceleration and deceleration process of one section is obtained, as shown in fig. 5. It can be seen from the figure that the off-going upshift can be decided both under no load and under full load, and that the off-going upshift occurs in a relatively low range, because the low range has better acceleration capacity than the high range, and that the off-going upshift scheme has an acceleration time of xs that is greater than the step-by-step upshift scheme in the same time window, and that the specific gravity of the acceleration time of xs to the total predicted time is greater in the low range than in the high range. On the other hand, the vehicle speed curve ab of the step-by-step upshift scheme in the high gear section never reaches the vehicle speed threshold v of n+1 gear upshift n+2 gear (n+1)-(n+2) The probability of (segment jk) is also greater, so that only a stepwise upshift scheme can be implemented.
Adjusting weightsCoefficients of
The optimization objective is made to pay more attention to economy, and a gear effect diagram of an empty and full-load vehicle in a one-stage acceleration and deceleration process is obtained, as shown in fig. 6. As can be seen from the figure, the off-grade upshift can be decided under no load and under full load, but the occurrence frequency of the off-grade upshift is obviously reduced, because the adoption of the step-by-step upshift scheme can increase the probability of the engine operating in the low fuel consumption area, thereby enabling J in the objective function to be reduced Eco Smaller, so that eventually it is decided that no out-of-step upshift should be made.
Adjusting weight coefficients
The optimization objective is made to pay more attention to driving comfort, and a gear effect diagram of an empty and full-load vehicle in a one-stage acceleration and deceleration process is obtained, as shown in fig. 7. From the figure, it can be seen that the out-of-order upshift can be decided under no load and under full load, and the occurrence frequency of the out-of-order upshift is obviously increased, because the out-of-order upshift is equivalent to the step-by-step upshift in terms of improving the driving comfort, the number of gear shifting times is less, and the driving comfort is better.
It should be noted that, one of the primary starting points of the out-of-order shift proposed in engineering application is that the step-by-step shift scheme has frequent power interruption, so that the out-of-order shift is theoretically realized to solve the power loss caused by frequent shift, so that in practical engineering application, the out-of-order shift decision method provided by the invention aims to pay more attention to the power.
By combining the steps with the steps shown in fig. 5, fig. 6 and fig. 7, the vehicle automatic transmission out-of-order gear shifting decision method based on the predicted running condition dynamic optimization effectively considers the dynamic property loss problem caused by the interruption of the driving force in the gear shifting process when the running condition is predicted, so that the out-of-order gear shifting decision is more targeted, the vehicle dynamic property, economy and driving comfort in a predicted time window are comprehensively considered, the model-based automatic optimization is performed, the optimizing result is matched with the predicted optimization target, and the problem that the traditional out-of-order gear shifting decision algorithm depends on a large number of gear shifting tables (MAP) and has weak adaptability is effectively solved.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. The vehicle automatic transmission gear shifting decision method based on the predicted driving condition dynamic optimization is characterized by comprising the following steps of:
step one, at a certain time t 0 The override shift decision module receives a shift enabling signal with a value of 1 sent by the shift logic module, and is enabled to start calculation;
step two, calculating the predicted termination time t of the future driving working condition by the override gear shift decision module f ；
Step three, obtaining a predicted termination time t f Then, the out-of-step gear shifting decision module starts to calculate the objective function J of the out-of-step gear shifting scheme and the step-by-step gear shifting scheme within the prediction time, wherein the objective function of the out-of-step gear shifting scheme is J Override The objective function of the step-by-step shift scheme is J Step ；
Step four, if the objective function J of the step-up gear shifting scheme Override An objective function J less than a step-by-step shift scheme Step The out-of-order gear shifting decision module decides out-of-order gear shifting, and outputs an out-of-order gear shifting enabling signal with the value of 1 to the gear shifting logic module; objective function J for skip-step shift scheme Override Objective function J greater than step-by-step shift scheme Step And the out-of-order gear shifting decision module decides that the gear shifting is needed step by step, outputs an out-of-order gear shifting signal with the value of 0 to the gear shifting logic module, and after receiving out-of-order gear shifting enabling signals with different values, the gear shifting logic module starts to take corresponding upshift measures, out-of-order upshift or step-by-step upshift, and finally outputs a corresponding target gear.
2. The method for determining an upshift decision as side-by-side shift of an automatic transmission for a vehicle based on dynamic optimization of predicted driving conditions as claimed in claim 1, wherein in said step one, if at t 0 The moment gear shifting logic module judges that the gear shifting condition is met, and starts to send a gear shifting enabling signal with a value of 1 to the out-of-order gear shifting decision module so as to enable the out-of-order gear shifting decision module; and at other moments when the upshift condition is not met, the gear shifting enabling signal value is 0, and the gear shifting decision module cannot be enabled.
3. The method for determining gear shift of automatic transmission of vehicle based on dynamic optimization of predicted driving condition according to claim 1, wherein in the second step, the termination time t f Calculated by the following steps:
by time t 0 Is the vehicle speed v of (2) 0 Calculating the predicted initial time t 0 Vehicle speed of +x
Vehicle speed v 0 Can be directly obtained in real time, and the time t is time t 0 By time t 0 The wind resistance caused by the speed drop in the power interruption process of +x is ignored, and the speed v is directly used 0 The calculated air resistance is taken as the air resistance when the power of x s is interrupted in the future, and the following are:
wherein delta is a rotational mass coefficient, m is a vehicle mass, g is a gravitational acceleration, f is a rolling resistance coefficient, θ is a road gradient, C d The wind resistance coefficient is that A is the windward area;
iterative solution using vehicle longitudinal dynamics equations
Still further solve v (t):
the vehicle longitudinal dynamics equation is:
wherein delta is a rotation mass coefficient, T e (t) is the engine output torque at time t, i g I is the transmission ratio in gear n+1 0 For the transmission ratio of the main speed reducer, eta is the transmission efficiency of a transmission system, r is the rolling radius of wheels, v (t) is the speed of the vehicle at the moment t, and the unit is m/s, and the initial moment t is predicted 0 +x，
Acceleration at time t;
in each iterative solving process, the calculation mode of the vehicle speed v (t) is as follows:
wherein dt is an iteration step length of the iterative solution of the vehicle speed;
engine output torque T e (t) is a parameter expressed by accelerator pedal manipulation, and the prediction model of the accelerator pedal is as follows:
wherein alpha (t) is accelerator pedal information, alpha (0) is accelerator pedal opening of the predicted initial moment, and the accelerator pedal opening can be directly obtained in real time and is equal to the moment t of the gear shifting logic module 0 The acquired throttle opening alpha c The change rate of the accelerator opening at the initial moment is obtained in real time according to alpha (0), and is equal to (alpha (0) -alpha (0-delta T))/delta T, wherein delta T is the scheduling period of the gear shifting logic module, and alpha (0-delta T) is the moment(t 0 - Δt), μ is the decay rate, defined as μ=α c /(2t′ f ) Wherein t' f As the termination time of the accelerator opening prediction, the discrete step length T of the accelerator opening prediction algorithm s The iteration step dt is the same as the vehicle speed;
engine output torque T e (t) also depends on the engine speed n e (t) there are:
T e (t)＝f(n e (t)，α(t))
engine speed n e (t) can be calculated by calculating the vehicle speed v (t) of each iteration process, and comprises the following steps:
wherein i is g For gear ratios corresponding to gear steps of a step-by-step shift scheme, i.e. gear ratios corresponding to n+1 gear, i 0 R is the rolling radius of the wheel, 0.1047 is pi/30, and pi is the circumference ratio;
at each vehicle speed iteration, the vehicle speed result v (t) is increased by the vehicle speed threshold v of n+1 gear and n+2 gear (n+1)-(n+2) Comparing, and the vehicle speed result v (t) is not less than v after a certain iteration is finished (n+1)-(n+2) Recording the iteration times m from the beginning to the moment, and then the moment t f -x is found as: t is t f –x＝m*dt+t 0 +x；
Thus, the predicted termination time t is obtained f ：t f ＝m*dt+t 0 +x+x。
4. The vehicle automatic transmission gear shift decision method based on the predicted driving condition dynamic optimization of claim 1, wherein in the third step, the specific expression of the objective function is:
wherein J is Eco Is used for the fuel consumption of hundred kilometers,
for the terminal speed of the vehicle, J Shift To address shift penalty for a step-by-step shift scheme, a J is provided in the present invention Shift 1, J of the skip-step shift scheme Shift 0->
The weight coefficients are respectively the economical efficiency, the dynamic performance and the driving comfort.
5. The method for making an automatic transmission shift-by-step decision for a vehicle based on dynamic optimization of predicted driving conditions as claimed in claim 4, wherein after completion of the iterative calculation, at a predicted termination time t f The terminal speed of the over-gear shifting scheme can be obtained
6. The vehicle automatic transmission skip-shifting decision-making method based on dynamic optimization of predicted driving conditions as claimed in claim 4, wherein,
in which Q Fuel (t) is the fuel consumed by the engine in the time range from the moment t to the moment t+dt, and the unit is g and L Dist And (t) is the mileage of the vehicle in the time range from the moment t to the moment t+dt, and the unit is m.
7. The method for determining an out-of-step shift in an automatic transmission for a vehicle based on dynamic optimization of predicted driving conditions as claimed in claim 4, wherein for an out-of-step shift scheme, the driving state is maintained for a predicted time period, and iterative calculation is performed with a dynamic and energy efficient model of the driving process and is carried into J Eco In the expression, i.eJ under the scheme of gear shifting with out-of-step Eco I under an override shift scheme g The gear ratio corresponding to the n+2 gear is set.
8. The method for determining an upshift decision as side-by-side shift in an automatic transmission for a vehicle based on dynamic optimization of predicted driving conditions as claimed in claim 4, wherein for a step-by-step shift scheme, there are driving and non-driving processes within a predicted time range, iterative calculation of driving and non-driving process correspondence dynamics and energy efficiency models is completed and is carried into expression J Eco In (3), the J under the step-by-step gear shifting scheme can be obtained Eco I under step-by-step gear shifting scheme g The gear ratio corresponding to the n+1 gear is adopted.
9. The vehicle automatic transmission skip shift decision method based on predictive driving condition dynamic optimization of claim 7 or 8, wherein there are dynamic and energy efficient models for driving process in the predictive time range:
10. the vehicle automatic transmission skip shift decision method based on predictive driving condition dynamic optimization of claim 7 or 8, wherein there are dynamic and energy efficient models for non-driving processes in the predictive time horizon:
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