CN115009260A - Control strategy of four-wheel drive hybrid power tractor - Google Patents
Control strategy of four-wheel drive hybrid power tractor Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W20/00—Control systems specially adapted for hybrid vehicles
- B60W20/10—Controlling the power contribution of each of the prime movers to meet required power demand
- B60W20/11—Controlling the power contribution of each of the prime movers to meet required power demand using model predictive control [MPC] strategies, i.e. control methods based on models predicting performance
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W2300/00—Indexing codes relating to the type of vehicle
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- B60W2300/152—Tractors
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W2510/00—Input parameters relating to a particular sub-units
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Abstract
The invention relates to a control strategy of a four-wheel drive hybrid tractor, the four-wheel drive hybrid tractor adopting the control strategy has a four-wheel drive mode and a rear drive mode, the four-wheel drive mode comprises a common four-wheel drive mode and a hybrid four-wheel drive mode, the rear drive mode comprises a common rear drive mode and a hybrid rear drive mode, and the control strategy comprises the following steps: p1 manually selects a four-wheel drive mode and a rear drive mode according to the SOC of the power battery; p2 calculating a required torque, wherein the required torque is obtained by a traction force mechanical model; when the P3 adopts a rear-drive mode, front and rear torque distribution is not needed, and the required torque is the torque of a rear traction system; when the four-wheel drive mode is adopted, the P4 carries out front and rear torque distribution, the control strategy adopts a control strategy based on fuzzy control, the input parameters are respectively gradient and plowing resistance, the output parameter is a front and rear torque distribution coefficient, and the front traction motor torque and the rear traction system torque are obtained according to the front and rear torque distribution coefficient and the required torque to carry out the front and rear torque distribution.
Description
Technical Field
The invention relates to the field of hybrid tractors, in particular to a control strategy of a four-wheel drive hybrid tractor.
Background
The traditional four-wheel drive tractor adopts the transfer case to distribute front and rear torque, the mechanical structure is complex in arrangement, and due to the limitation of the structural form, the torque ratio of front and rear driving wheels is difficult to change in real time, so that the four-wheel drive tractor is very inconvenient. The electric tractor is a vehicle which takes a vehicle-mounted power supply as power, drives wheels by a motor and meets various working requirements. In the aspect of the influence on the environment, the electric tractor has less influence than a conventional tractor, and the prospect thereof is widely seen. However, the conventional electric tractor has short working endurance, needs frequent charging during working, is limited by the limitation of the current charging speed, and is low in working efficiency and very inconvenient in actual working.
Disclosure of Invention
The invention provides a four-wheel drive hybrid power tractor based on a front driving motor structure, and provides a four-wheel drive hybrid power tractor control strategy.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the four-wheel drive hybrid tractor adopting the control strategy of the four-wheel drive hybrid tractor has two driving modes: the four-wheel drive mode comprises two working modes: the system comprises a common four-wheel drive mode and a hybrid four-wheel drive mode, wherein the rear drive mode comprises two working modes: the control strategy of the four-wheel drive hybrid power tractor comprises the following steps,
selecting a driving mode, manually selecting a four-wheel drive mode or a rear drive mode according to the SOC of the power battery, wherein the SOC can be divided into a small (0.2-0.3), a medium (0.2< medium <0.4) and a large (0.3-0.4), when the SOC is small, the rear drive mode is allowed to be started, and the working mode of the rear drive mode is defaulted to be a common rear drive mode; when the SOC is in the middle, a rear-drive mode or a four-drive mode is allowed to be started, the working mode of the rear-drive mode is defaulted to be a hybrid rear-drive mode, and the working mode of the four-drive mode is defaulted to be a common four-drive mode; when the SOC is large, a rear-drive mode or a four-drive mode is allowed to be started, the working mode of the rear-drive mode is defaulted to be a hybrid rear-drive mode, the working mode of the four-drive mode is defaulted to be a hybrid four-drive mode, and when the driving mode is selected, a control strategy automatically switches the corresponding working mode according to the SOC;
p2, calculating the required torque, the required torque is obtained by a traction force mechanics model,
the traction force mechanics model includes a model of,
F g ＝zbhk,F TM ＝(1.1～1.2)F g ,
wherein V is the maximum speed during ploughing, r is the tractor driving wheel radius, n is the engine speed, i g For the transmission ratio of the transmission in the respective gear, i 0 For the drive ratio of the main reducer of the tractor, i L For the gear ratio of the wheel-side reducer of the tractor, F g The plowing resistance is Z, the number of ploughshares is z, the width of a single ploughshare is b, the plowing depth is h, the soil specific resistance is k, F TM Is the tractive force of a tractor, P T Is the power of the tractor eta t In order to achieve the efficiency of the traction,
the parameters of the ploughshares comprise the number z of the ploughshares, the width b of a single ploughshare and the ploughing depth h,
dividing the above parameters by the engine speed n and the transmission ratio i of the transmission in the corresponding gear g The parameters of the plough share and the parameters of the plough share are known, so that the required torque can be calculated through a traction force mechanical model;
p3, when the rear-drive mode is started, front and rear torque distribution is not needed, the required torque is the torque of the rear traction system, the torque of the rear traction system is input into the rear traction system, and the rear traction system provides driving torque to drive the four-wheel drive hybrid tractor;
p4 when starting fourIn the driving mode, front and rear torque distribution is needed, a control strategy of the four-wheel drive hybrid tractor adopts a fuzzy control-based control strategy, the control strategy comprises 2 independent input parameters and 1 output parameter, the input parameters are respectively gradient and plowing resistance, the output parameters are front and rear torque distribution coefficients, the front and rear torque distribution coefficients are the ratio of driving force converted from the torque of a rear traction system to the torque of a rear wheel to the total driving force, and the gradient and plowing resistance F are converted into the total driving force g The torque is input into a fuzzy controller 1, the fuzzy controller 1 carries out fuzzy operation and then outputs a front and rear torque distribution coefficient, and front traction motor torque and rear traction system torque are obtained according to the front and rear torque distribution coefficient and required torque to carry out front and rear torque distribution.
Optionally, the rear traction system comprises an adjusting controller 1, an adjusting controller 2, an engine, a rear traction motor, a power coupler and a rear wheel, when the four-wheel drive mode is selected and the SOC is middle, the torque and the SOC of the rear traction system are input into the adjusting controller 1, the adjusting controller 1 starts the ordinary four-wheel drive mode according to the SOC and the four-wheel drive mode, the adjusting controller 1 transmits the torque and the SOC of the rear traction system to the adjusting controller 2, the adjusting controller 2 calculates a torque distribution coefficient and performs torque distribution, at this time, the engine torque is divided into a driving torque and a charging torque, the charging torque is fixed to be 70% -80% of the rated torque of the front traction motor, the driving torque is transmitted to the rear wheel transmission system through the power coupler, the rear wheel transmission system drives the rear wheel to drive the four-wheel hybrid tractor, and the charging torque drives the rear traction motor to generate power through the power coupler, the power battery is charged to maintain the torque demand of the front traction motor in the four-wheel drive mode.
Optionally, the rear traction system further includes a fuzzy controller 2, when the four-wheel drive mode is selected and the SOC is large, the rear traction system torque and the SOC are input to the adjusting controller 1, the adjusting controller 1 starts the hybrid four-wheel drive mode according to the SOC and the four-wheel drive mode, the adjusting controller 1 inputs the rear traction system torque and the SOC to the fuzzy controller 2, the fuzzy controller 2 performs fuzzy operation and outputs a motor torque coefficient and a rear traction system torque to the adjusting controller 2, the motor torque coefficient is a ratio of the rear traction motor torque to the rear traction system torque, and the adjusting controller 2 performs torque distribution through the motor torque coefficient and the rear traction system torque.
Optionally, when the rear-drive mode is selected and the SOC is small, the adjustment controller 1 selects a normal rear-drive mode according to the rear-drive mode and the SOC, the required torque is a rear traction system torque, the rear traction system torque and the SOC are input to the adjustment controller 1, the adjustment controller 1 outputs the rear traction system torque and the SOC to the adjustment controller 2, the adjustment controller 2 calculates a torque distribution coefficient and performs torque distribution, the engine torque includes a driving torque and a charging torque, the charging torque is fixed to be 70% -80% of a rated torque of the front traction motor, the driving torque is transmitted to the rear wheel transmission system through the power coupler, the rear wheel transmission system drives the rear wheels to drive the four-drive hybrid tractor, the charging torque drives the rear traction motor to generate power through the power coupler, and the power battery is charged, so that the four-drive hybrid tractor can start the four-drive mode.
Alternatively, when the rear drive mode is selected and the SOC is medium or large, the tuning controller 1 selects the hybrid rear drive mode according to the rear drive mode and the SOC, the required torque is a rear traction system torque, the rear traction system torque and the SOC are input to the tuning controller 1, the tuning controller 1 inputs the rear traction system torque and the SOC to the fuzzy controller 2, the fuzzy controller 2 outputs a motor torque coefficient and a rear traction system torque to the tuning controller 2 after fuzzy operation, the motor torque coefficient is a ratio of the rear traction motor torque to the rear traction system torque, and the tuning controller 2 performs torque distribution by the motor torque coefficient and the rear traction system torque.
Optionally, the fuzzy subset of grade i is divided into { VS, S, M, B, VB }, and the plowing resistance F is divided into g The fuzzy subsets are divided into { VS, S, M, B, VB }, fuzzy subsets of front and rear torque distribution coefficients k are divided into { VS, S, RS, RM, LS, M, LM, VM, RB, B, VB }, wherein the fuzzy subsets VS, S, RS, RM, LS, M, LM, VM, RB, B, VB represent minimum, small, medium, large and maximum respectively, and the specific fuzzy rule is as follows,
if i is VS, F g Is VS, the output k is VS,
if i is VS, F g S, M, the output k is S,
if i is VS, F g B, VB, the output k is RS,
if i is S, F g Is VS, the output k is RS,
if i is S, F g S, M, the output k is RM,
if i is S, F g B, VB, the output k is LS,
if i is M, F g VB and B, the output k is LM,
if i is M, F g M, S, VS, the output k is M,
if i is B, F g VB and B, the output k is RB,
if i is B, F g M, S, the output k is VM,
if i is B, F g Is VS, the output k is LM,
if i is VB, F g VB and B, the output k is VB,
if i is VB, F g M, S, the output k is B,
if i is VB, F g At VS, the output k is RB.
Alternatively, the gradient i adopts a triangular membership function, and the plowing resistance F g A triangular membership function is adopted, a membership function combining a trapezoidal membership function and the triangular membership function is adopted as the front and rear torque distribution coefficient k, and a gravity center method is adopted to perform anti-fuzzy operation on the distribution coefficient k.
Alternatively, the four-wheel drive hybrid tractor control strategy outputs a mode prompt according to the size of the SOC, outputs an available rear drive mode when the SOC is small, and prompts charging, and outputs an available rear drive mode and a four-wheel drive mode when the SOC is medium, and prompts charging.
The control strategy of the four-wheel drive hybrid tractor provided by the invention can achieve the following beneficial effects:
1. compared with the defect that the components are inconvenient to arrange because the front and the rear of the traditional four-wheel drive tractor are connected by adopting a mechanical transmission shaft, the four-wheel drive hybrid tractor adopting the control strategy of the invention adopts the structural form of a front driving motor and a rear traction system, so that the arrangement of the front and the rear components is convenient.
2. The traditional four-wheel drive tractor adopts the transfer case to distribute torque, and is difficult to change the torque ratio of front and rear driving wheels in real time due to the limitation of a mechanical structure, so that the four-wheel drive tractor is very inconvenient. The four-wheel drive hybrid power tractor adopting the control strategy of the invention adopts the structural form of a front driving motor and a rear traction system, and is beneficial to adjusting the torque of the front traction motor and the rear traction system.
3. The invention is based on the plowing working condition of the tractor, takes the gradient and the plowing resistance as control parameters, and adopts a four-wheel drive hybrid power tractor torque distribution strategy based on fuzzy logic to control the slippage rate within a reasonable range.
4. The traditional electric tractor has short working duration, needs frequent charging during working, is limited by the limitation of the current charging speed, has lower working efficiency in actual work and is very inconvenient. The four-wheel drive tractor adopting the control strategy of the invention adopts a hybrid scheme, is not influenced by short endurance time and does not need frequent charging.
5. According to the control strategy of the four-wheel drive hybrid tractor provided by the invention, when the SOC is small, the four-wheel drive mode cannot be started because the front wheel drive is electrically driven, and at the moment, the charging can be selected, so that the SOC is improved to start the four-wheel drive mode; alternatively, the hybrid tractor can charge the power battery to start the four-wheel drive mode when the SOC is small without charging. The four-wheel drive mode can also be started under the non-charging condition and when the SOC is small, so that the working efficiency is improved.
6. According to the control strategy of the four-wheel drive hybrid tractor provided by the invention, when the SOC is middle, the four-wheel drive mode can be started. At this time, in order to avoid the phenomenon that the SOC is reduced and the four-wheel drive mode cannot be used due to the fact that the electric quantity is consumed too fast, the hybrid tractor can charge the power battery to maintain the four-wheel drive mode when the hybrid tractor is in the SOC, and therefore working efficiency is improved.
7. According to the control strategy of the four-wheel drive hybrid power tractor, when the SOC is small and medium, the battery can be charged in any mode, so that damage caused by too low electric quantity of the battery is avoided, and the service life of the battery is prevented from being reduced.
8. According to the control strategy of the four-wheel drive hybrid tractor, the SOC is always in a reasonable state (the SOC is not too low because the battery is charged in each mode), and the release of the motor performance is facilitated.
Drawings
Fig. 1 is a whole tractor structure diagram adopting the control strategy of the four-wheel drive hybrid tractor of the invention.
Fig. 2 is a control structure diagram of the whole tractor adopting the control strategy of the four-wheel drive hybrid tractor.
Fig. 3 is a diagram of a tractor rear traction system employing a four-wheel drive hybrid tractor control strategy of the present invention.
FIG. 4 is a fuzzy rule schematic diagram of front and rear torque distribution in a control strategy of a four-wheel drive hybrid tractor according to the invention.
FIG. 5 is a schematic representation of a membership function for grade in a four-wheel drive hybrid tractor control strategy according to the present invention.
FIG. 6 is a schematic diagram of a membership function of plowing resistance in a control strategy of a four-wheel drive hybrid tractor according to the present invention.
FIG. 7 is a membership function diagram of the distribution coefficients in a control strategy for a four-wheel drive hybrid tractor according to the present invention.
FIG. 8 is a schematic diagram of a fuzzy rule for torque distribution of a rear traction system in a control strategy of a four-wheel drive hybrid tractor according to the present invention.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples.
Referring to fig. 1, the four-wheel drive hybrid tractor adopting the control strategy of the four-wheel drive hybrid tractor according to the embodiment includes a power battery, a front traction motor, a rear traction motor, and an engine, the power battery is electrically connected to the front traction motor and the rear traction motor, the front traction motor is mechanically connected to two front wheels through a front wheel transmission system, an output torque of the rear traction motor and an output torque of the engine are torque-coupled through a power coupler, and a torque output end of the power coupler is connected to two rear wheels through a rear wheel transmission system. The four-wheel drive hybrid tractor has two drive modes: the four-wheel drive mode comprises two working modes: the system comprises a common four-wheel drive mode and a hybrid four-wheel drive mode, wherein the rear drive mode comprises two working modes: a normal rear drive mode and a hybrid rear drive mode.
The control strategy of the four-wheel drive hybrid power tractor specifically comprises the following steps:
p1, selecting a driving mode, wherein the four-wheel drive mode or the rear-wheel drive mode can be manually selected according to the SOC of the power battery, the SOC can be divided into a small (0.2-0.3), a medium (0.2< medium <0.4) and a large (0.3-0.4), when the SOC is small, the rear-wheel drive mode can be started, and the working mode of the rear-wheel drive mode is a common rear-wheel drive mode; when the SOC is middle, a rear-drive mode or a four-drive mode can be started, wherein the working mode of the rear-drive mode is a hybrid rear-drive mode, and the working mode of the four-drive mode is a common four-drive mode; when the SOC is large, a rear-drive mode or a four-drive mode can be started, wherein the working mode of the rear-drive mode is a hybrid rear-drive mode, and the working mode of the four-drive mode is a hybrid four-drive mode; when the driving mode is selected, the control strategy automatically switches the corresponding working mode according to the SOC; the control strategy of the four-wheel drive hybrid power tractor outputs a mode prompt according to the SOC, and when the SOC is small, an available rear drive mode is output and charging is prompted; when the SOC is in the middle, the back-drive mode or the four-drive mode can be used, and charging is prompted; when the SOC is large, the output can be in a back-drive mode or a four-drive mode.
P2, calculating the required torque, the required torque is obtained by a traction force mechanics model,
the traction force mechanics model includes a model of,
F g ＝zbhk,F TM ＝(1.1～1.2)F g ,
wherein V is the maximum speed during ploughing, r is the tractor driving wheel radius, n is the engine speed, i g For the transmission ratio of the transmission in the respective gear, i 0 For the main reducer gear ratio of the tractor, i L For the gear ratio of the wheel-side reducer of the tractor, F g The plowing resistance is, z is the number of plowshares, b is the width of a single plowshare, h is the plowing depth, k is the soil specific resistance, F TM Is the tractive force of a tractor, P T Is the power of the tractor eta t In order to achieve the efficiency of the traction,
the parameters of the ploughshares comprise the number z of the ploughshares, the width b of a single ploughshare and the ploughing depth h,
dividing the above parameters by the engine speed n and the transmission ratio i of the transmission in the corresponding gear g The parameters of the plough share and the parameters of the plough share are known, so that the required torque can be calculated through a traction force mechanical model;
p3, when the rear-drive mode is adopted, front and rear torque distribution is not needed, the required torque is the torque of the rear traction system, the torque of the rear traction system is input into the rear traction system, and the rear traction system provides driving torque to drive the four-wheel drive hybrid tractor;
p4, when the four-wheel drive mode is adopted, the front and back torque distribution is needed, the control strategy of the four-wheel drive hybrid tractor adopts the control strategy based on fuzzy control, the control strategy has 2 independent input parameters and 1 output parameter, the input parameters are respectively the gradient and the plowing resistance, the output parameters are the front and back torque distribution coefficient, the front and back torque distribution coefficient is the ratio of the driving force of the back traction system torque to the back wheel and the total driving force, the gradient and the plowing resistance F are converted into the gradient and the plowing resistance g The torque is input into a fuzzy controller 1, the fuzzy controller 1 outputs a front and rear torque distribution coefficient after fuzzy operation, and the front traction motor torque and the rear traction system torque are obtained according to the front and rear torque distribution coefficient and the required torque and are distributed.
In some embodiments of the present invention, the rear traction system includes an adjustment controller 1, an adjustment controller 2, an engine, a rear traction motor, a power coupler, and rear wheels, when a four-wheel drive mode is selected and the SOC is medium, a rear traction system torque and the SOC are input to the adjustment controller 1, the adjustment controller 1 starts a normal four-wheel drive mode according to the SOC and the four-wheel drive mode, the adjustment controller 1 transmits the rear traction system torque and the SOC to the adjustment controller 2, the adjustment controller 2 calculates a torque distribution coefficient and performs torque distribution, at this time, the engine torque is divided into a driving torque and a charging torque, the charging torque is fixed to be (70% -80%) of a rated torque of the front traction motor, the driving torque is transmitted to the rear wheel transmission system through the power coupler, the rear wheel transmission system drives the rear wheels to drive the four-wheel hybrid tractor, the charging torque drives the rear traction motor to generate power through the power coupler, the power battery is charged to maintain the torque demand of the front traction motor in the four-wheel drive mode.
In some embodiments of the present invention, the rear traction system further includes a fuzzy controller 2, when the four-wheel drive mode is selected and the SOC is large, the rear traction system torque and the SOC are input to the tuning controller 1, the tuning controller 1 starts the hybrid four-wheel drive mode according to the SOC and the four-wheel drive mode, the tuning controller 1 inputs the rear traction system torque and the SOC to the fuzzy controller 2, the fuzzy controller 2 performs a fuzzy operation and outputs a motor torque coefficient and a rear traction system torque to the tuning controller 2, the motor torque coefficient is a ratio of the rear traction motor torque to the rear traction system torque, and the tuning controller 2 performs torque distribution by the motor torque coefficient and the rear traction system torque.
In some embodiments of the present invention, when the rear drive mode is selected and the SOC is small, the tuning controller 1 selects the normal rear drive mode according to the rear drive mode and the SOC, the required torque is a rear traction system torque, the rear traction system torque and the SOC are input to the tuning controller 1, the tuning controller 1 outputs the rear traction system torque and the SOC to the tuning controller 2, the tuning controller 2 calculates a torque distribution coefficient, and controls the engine to output an engine torque, the engine torque includes a driving torque and a charging torque, the charging torque is fixed to 70% -80% of a rated torque of the front traction motor, the driving torque is transmitted to the rear wheel transmission system through the power coupler, the rear wheel transmission system drives the rear wheels to drive the four-wheel hybrid tractor, and the charging torque drives the rear traction motor to generate power through the power coupler to charge the power battery, so that the four-wheel hybrid tractor can start the four-wheel drive mode.
In some embodiments of the present invention, when the rear drive mode is selected and the SOC is medium or large, the tuning controller 1 selects the hybrid rear drive mode according to the rear drive mode and the SOC, the required torque is a rear traction system torque, the rear traction system torque and the SOC are input to the tuning controller 1, the tuning controller 1 inputs the rear traction system torque and the SOC to the fuzzy controller 2, the fuzzy controller 2 outputs a motor torque coefficient and a rear traction system torque to the tuning controller 2 after performing a fuzzy operation, the motor torque coefficient is a ratio of the rear traction motor torque to the rear traction system torque, and the tuning controller 2 performs torque distribution by the motor torque coefficient and the rear traction system torque.
When the fuzzy control rule is established, the maximum slip ratio of the tractor is ensured to be about 0.15-0.18 as much as possible.
The fuzzy operation performed by the fuzzy controller 1 comprises fuzzification of input parameters, membership functions, fuzzy rules and defuzzification.
The fuzzification of the input parameters includes fuzzification of grade and plowing resistance.
Dividing the fuzzy subset of the gradient i into { VS, S, M, B, VB }, and dividing the plowing resistance F g The fuzzy subsets are divided into { VS, S, M, B, VB }, fuzzy subsets of front and rear torque distribution coefficients k are divided into { VS, S, RS, RM, LS, M, LM, VM, RB, B, VB }, wherein the fuzzy subsets VS, S, RS, RM, LS, M, LM, VM, RB, B, VB represent minimum, small, medium, large and maximum respectively, and the specific fuzzy rule is as follows:
if i is VS, F g Is VS, the output k is VS,
if i is VS, F g S, M, the output k is S,
if i is VS, F g B, VB, the output k is RS,
if i is S, F g Is VS, the output k is RS,
if i is S, F g In the order of S, M, is,the output k is then the RM and,
if i is S, F g B, VB, the output k is LS,
if i is M, F g VB and B, the output k is LM,
if i is M, F g M, S, VS, the output k is M,
if i is B, F g VB and B, the output k is RB,
if i is B, F g M, S, the output k is VM,
if i is B, F g Is VS, the output k is LM,
if i is VB, F g VB and B, the output k is VB,
if i is VB, F g M, S, the output k is B,
if i is VB, F g At VS, the output k is RB.
The membership function of the input parameter gradient has the argument [ -0.1,0.1]Negative values represent downhill slopes and positive values represent uphill slopes; the input parameter is the membership function of plowing resistance, and the domain is [3.7 multiplied by 10 ] 4 ,4.3×10 4 ](ii) a The torque of the traction system is converted into the ratio k of the driving force of the rear wheel to the total driving force after the parameter is output, and the argument is [0.74,0.88 ]]。
In some embodiments of the invention, the slope i is a triangular membership function and the plowing resistance F g And a triangular membership function is adopted, the front and rear torque distribution coefficients k adopt a membership function combining a trapezoidal membership function and the triangular membership function, and because the output quantity of fuzzy control is fuzzy quantity, a gravity center method is adopted for deblurring, so that the front and rear torque distribution coefficients are obtained. The center of gravity method has smoother output inference control, and the output changes even with a slight change in the input parameter, so that the change in the torque coefficient of the output can be made smoother.
In some embodiments of the invention, the fuzzy operation of the rear traction system comprises fuzzification of input parameters, membership functions, fuzzy rules and defuzzification.
The fuzzification of the input parameters includes fuzzification of the rear traction system torque and SOC. The torque and SOC of the rear traction system are equally divided into5 fuzzy subsets. The torque domain of the rear traction system is [0, T max ]By the formula T r ＝T t /T max To convert the discourse domain of the torque of the rear traction system to [0, 1]]An interval. In which Tr is the torque of the rear traction system after switching the domain of discourse, T t For the torque of the rear traction system at a certain moment, T max The maximum torque required by the whole vehicle. The 5 fuzzy subsets of the rear traction system torque are expressed as { small, medium, large } by { TS, S, M, B, TB }. The universe of discourse of SOC is [0, 1]The 5 fuzzy subsets of SOC are expressed as { very low, medium, high, very high } by { TL, L, M, H, TH }.
The output parameter motor torque coefficient lambda has a discourse range of [ -0.5, 1], the motor torque coefficient lambda is averagely divided into 5 fuzzy subsets, and the 5 fuzzy subsets of the motor torque coefficient lambda are expressed by { TS, S, M, B, TB } { small, medium, large }.
The membership functions of the torque and the SOC of the rear traction system are represented by a trapezoidal function and a triangular function, and the membership functions of the torque coefficient of the rear traction motor are represented by triangular functions.
Fuzzy rules: if Tr is TS, SOC is TL, L, M, H and TH, then lambda is TS; if Tr is S and SOC is TL, then lambda is S; if Tr is S and SOC is L, M, H, TH, then lambda is TS; if Tr is M and SOC is TL, then lambda is B; if Tr is M and SOC is L, then lambda is M; if Tr is M and SOC is M, H, then lambda is S; if Tr is M and SOC is TH, then lambda is TS; if Tr is B, SOC is TL and L, lambda is TB; if Tr is B and SOC is M, H, then lambda is M; if Tr is B and SOC is TH, then lambda is S; if Tr is TB and SOC is TL, then lambda is TB; if Tr is TB and SOC is L, then lambda is B; if Tr is TB and SOC is M, then lambda is M; if Tr is TB and SOC is H, then lambda is S; if Tr is TB and SOC is TH, then λ is TS.
The anti-fuzzy calculation method adopts a gravity center method, the gravity center method has smoother output inference control, the output changes even corresponding to small changes of input parameters, and the change of the output torque coefficient can be smoother.
The working principle is as follows:
the control strategy can be understood as a parallel hybrid power system of the rear wheels and a motor of the front wheels, and the parallel hybrid power system provides electric energy for the motor of the front wheels. The present invention can be divided into two drive modes: the four-wheel drive mode and the rear drive mode can respectively subdivide two working modes. The four-wheel drive mode is divided into a common four-wheel drive mode and a hybrid four-wheel drive mode, and the rear drive mode is divided into a common rear drive mode and a hybrid rear drive mode. The four-wheel drive mode or the rear drive mode can be manually selected, the working mode cannot be selected after the four-wheel drive mode is selected, the working mode is automatically selected by the system according to the SOC, and the rear drive mode is the same. The four-wheel drive mode and the rear-wheel drive mode can be selected according to the size of the SOC, the SOC can be divided into small (< 0.2-0.3), medium (<0.2 < medium <0.4) and large (> 0.3-0.4), only the normal rear-wheel drive mode can be started when the SOC is small, the hybrid rear-wheel drive mode or the normal four-wheel drive mode can be started when the SOC is medium, and the hybrid rear-wheel drive mode and the hybrid four-wheel drive mode can be started when the SOC is large. When the common rear-drive mode is started, only the engine provides torque, the engine torque is divided into driving torque and charging torque at the moment, the driving torque is transmitted to the rear wheel transmission system through the power coupler, the rear wheel transmission system drives the rear wheels to be used for driving the tractor, the charging torque drives the rear traction motor to generate electricity through the power coupler, and the SOC of the battery is improved, so that the four-drive hybrid tractor can use the four-drive mode. When the hybrid rear-drive mode is started, the required torque and the adjusted SOC are input to the fuzzy controller 2, fuzzy operation is performed, a motor torque coefficient is output, and torque distribution is performed. When the four-wheel drive mode is started, a control strategy of the four-wheel drive hybrid tractor adopts a fuzzy control-based control strategy, the control strategy comprises 2 independent input parameters and 1 output parameter, the input parameters comprise gradient and plowing resistance, the output parameters are front and rear torque distribution coefficients, the front and rear torque distribution coefficients are the ratio of driving force converted from rear traction system torque to rear wheels to total driving force, the gradient and the plowing resistance are input to a fuzzy controller 1, the fuzzy controller 1 outputs the front and rear torque distribution coefficients after fuzzy operation, and front traction motor torque and rear traction system torque are worked out according to the front and rear torque distribution coefficients and required torque and front and rear torque distribution is carried out. When a common four-wheel drive mode is adopted, the torque and the SOC of a rear traction system are input into an adjusting controller 1, the adjusting controller 1 transmits the torque and the SOC of the rear traction system to an adjusting controller 2, the adjusting controller 2 outputs torque distribution information and transmits the torque distribution information to an engine, the torque of the engine is divided into driving torque and charging torque at the moment, the driving torque is transmitted to a rear wheel transmission system through a power coupler, the rear wheel transmission system drives a rear wheel to be used for driving a tractor, and the charging torque drives a rear traction motor to generate power through the power coupler so as to maintain the torque requirement of a front traction motor in the four-wheel drive mode. When the hybrid four-wheel drive mode is adopted, the torque and the SOC of the rear traction system are input into the adjusting controller 1, the adjusting controller 1 inputs the torque and the SOC of the rear traction system into the fuzzy controller 2, the fuzzy controller 2 carries out fuzzy operation to output a motor torque coefficient, and the engine and the rear traction motor carry out torque distribution according to the torque distribution coefficient and the torque of the rear traction system.
The functions of all the components are as follows:
the fuzzy controller 1 outputs the front and rear torque distribution coefficients, and the four-wheel drive mode is activated.
The fuzzy controller 2 outputs a motor torque coefficient, and the hybrid rear-drive mode and the hybrid four-drive mode function.
And the adjusting controller 1 selects a proper working mode according to the magnitude of the SOC value and the driving mode, and inputs the torque and the SOC of the rear traction system into the adjusting controller 2 or the fuzzy controller 2 according to the specific working mode. The torque and SOC of the rear traction system in the normal rear-drive mode and the normal four-drive mode are output to the tuning controller 2, and the torque and SOC of the rear traction system in the hybrid rear-drive mode and the hybrid four-drive mode are output to the fuzzy controller 2.
The adjusting controller 2 outputs torque distribution information according to the torque of the rear traction system and the SOC in the normal rear-drive mode, wherein the engine torque is positive, the motor torque is negative, the motor torque is driven in a positive time, and the motor torque is charged in a negative time, and the engine torque is respectively driving torque and charging torque, the driving torque is used for driving the four-wheel-drive hybrid tractor, and the charging torque is used for charging the power battery so as to use the hybrid rear-drive mode and enable the four-wheel-drive mode. The common four-wheel drive mode is used for distributing information according to the torque of a rear traction system and the SOC output torque, the engine torque is respectively driving torque and charging torque, the driving torque is used for driving a four-wheel drive hybrid power tractor, and the charging torque is used for charging a power battery so as to ensure the normal use of the four-wheel drive mode.
Claims (9)
1. A control strategy of a four-wheel drive hybrid tractor is characterized by comprising the following steps:
p1, manually selecting a four-wheel drive mode or a rear drive mode according to the SOC of the power battery, wherein the SOC is small, the rear drive mode is allowed to be started, and the working mode of the rear drive mode is defaulted to be a common rear drive mode; when the SOC is in the middle, the rear-drive mode or the four-drive mode is allowed to be started, and the working mode of the rear-drive mode defaults to a hybrid rear-drive mode and the working mode of the four-drive mode to be a common four-drive mode; when the SOC is large, the rear-drive mode or the four-drive mode is allowed to be started, and the working mode of the rear-drive mode is defaulted to be the hybrid rear-drive mode and the working mode of the four-drive mode is defaulted to be the hybrid four-drive mode;
p2, calculating a required torque, said required torque being determined by a traction mechanics model,
the traction force mechanics model may include,
F g ＝zbhk,F TM ＝(1.1～1.2)F g ,
wherein V is the maximum speed during ploughing, r is the tractor driving wheel radius, n is the engine speed, i g For the transmission ratio of the transmission in the respective gear, i 0 For the drive ratio of the main reducer of the tractor, i L For the gear ratio of the wheel-side reducer of the tractor, F g The plowing resistance is Z, the number of ploughshares is z, the width of a single ploughshare is b, the plowing depth is h, the soil specific resistance is k, F TM Is the tractive force of a tractor, P T Power of the tractor, eta t To traction efficiency;
the plough share parameters comprise the number z of the plough shares, the width b of the single plough share and the ploughing depth h;
p3, when the rear-drive mode is started, front and rear torque distribution is not needed, the required torque is the torque of a rear traction system, the torque of the rear traction system is input into the rear traction system, and the rear traction system provides driving torque to drive the four-wheel drive hybrid tractor;
p4, when the four-wheel drive mode is started, front and rear torque distribution is required; the control strategy adopts a fuzzy control-based control strategy and comprises 2 independent input parameters and 1 output parameter, wherein the input parameters are respectively gradient and plowing resistance, the output parameters are front and rear torque distribution coefficients, and the front and rear torque distribution coefficients are the ratio of the driving force converted from the rear traction system torque to the rear wheels to the total driving force; the gradient i and the plowing resistance F g The torque distribution method is characterized by comprising the steps of inputting the torque distribution coefficient to a fuzzy controller (1), outputting a front and rear torque distribution coefficient after fuzzy operation is carried out on the fuzzy controller (1), obtaining a front traction motor torque and a rear traction system torque according to the front and rear torque distribution coefficient and a required torque, and distributing the front and rear torques.
2. A four-wheel drive hybrid tractor control strategy according to claim 1, characterized in that the rear traction system comprises a trim controller (1), a trim controller (2), an engine, a rear traction motor, a power coupling and rear wheels, when a four-wheel drive mode is selected and the SOC is medium, the rear traction system torque and the SOC are input to the trim controller (1), the trim controller (2) initiates the ordinary four-wheel drive mode according to SOC and four-wheel drive mode; the adjusting controller (1) transmits the torque of the rear traction system and the SOC to the adjusting controller (2), the adjusting controller (2) calculates a torque distribution coefficient and distributes the torque, the engine torque is divided into driving torque and charging torque at the moment, the charging torque is fixed to be 70% -80% of the rated torque of the front traction motor, the driving torque is transmitted to a rear wheel transmission system through a power coupler, the rear wheel transmission system drives a rear wheel to be used for driving the four-wheel drive hybrid power tractor, the charging torque drives the rear traction motor to generate power through the power coupler, and a power battery is charged so as to maintain the torque requirement of the front traction motor in the four-wheel drive mode.
3. A four-wheel drive hybrid tractor control strategy according to claim 2, characterized in that the rear traction system further comprises a fuzzy controller (2), when a four-wheel drive mode is selected and the SOC is large, the rear traction system torque and the SOC are input to the tuning controller (1), the tuning controller (1) activates the hybrid four-wheel drive mode according to the SOC and the four-wheel drive mode; the adjusting controller (1) inputs the rear traction system torque and the SOC into the fuzzy controller (2), the fuzzy controller (2) outputs a motor torque coefficient and the rear traction system torque to the adjusting controller (2) after fuzzy operation is carried out, the motor torque coefficient is the ratio of the rear traction motor torque to the rear traction system torque, and the adjusting controller (2) carries out torque distribution through the motor torque coefficient and the rear traction system torque.
4. A four-wheel drive hybrid tractor control strategy according to claim 2, characterized in that when a rear drive mode is selected and the SOC is small, the steering controller (1) selects the normal rear drive mode according to the rear drive mode and the SOC; the required torque is the rear traction system torque, the rear traction system torque and the SOC are input to the regulation controller (1), the regulation controller (1) outputs the rear traction system torque and the SOC to the regulation controller (2), the regulation controller (2) calculates a torque distribution coefficient and performs torque distribution, the engine torque includes a drive torque and a charge torque, the charging torque is fixed to be 70% -80% of the rated torque of the front traction motor, the driving torque is transmitted to a rear wheel transmission system through a power coupler, the rear wheel transmission system drives a rear wheel to drive the four-wheel drive hybrid tractor, the charging torque drives the rear traction motor to generate electricity through the power coupler, and charges the power battery, so that the four-wheel drive hybrid tractor can start a four-wheel drive mode.
5. A four-wheel drive hybrid tractor control strategy according to claim 3, characterized in that when the rear drive mode is selected and the SOC is medium or large, the tuning controller (1) selects the hybrid rear drive mode according to rear drive mode and SOC; the required torque is the rear traction system torque, the rear traction system torque and the SOC are input into the adjusting controller (1), the adjusting controller (1) inputs the rear traction system torque and the SOC into the fuzzy controller (2), the fuzzy controller (2) outputs a motor torque coefficient and the rear traction system torque to the adjusting controller (2) through fuzzy operation, the motor torque coefficient is the ratio of the rear traction motor torque to the rear traction system torque, and the adjusting controller (2) performs torque distribution through the motor torque coefficient and the rear traction system torque.
6. A four-wheel drive hybrid tractor control strategy according to claim 1, characterized in that in step P4, the fuzzy operation performed by the fuzzy controller (1) comprises fuzzification, membership functions, fuzzy rules and defuzzification of input parameters.
7. The control strategy of a four-wheel drive hybrid tractor according to claim 6, wherein the fuzzification of input parameters includes fuzzification of grade and plowing resistance, specifically:
dividing the fuzzy subset of the gradient i into { VS, S, M, B, VB }, and dividing the plowing resistance F g The fuzzy subsets are divided into { VS, S, M, B, VB }, fuzzy subsets of the front and rear torque distribution coefficients k are divided into { VS, S, RS, RM, LS, M, LM, VM, RB, B, VB }, wherein the fuzzy subsets VS, S, RS, RM, LS, M, LM, VM, RB, B, VB represent minimum, small, medium, large and maximum respectively, and the specific fuzzy rule is as follows: if i is the value of VS, then,F g if the output k is VS, the output k is VS; if i is VS, F g S, M, the output k is S; if i is VS, F g B, VB, the output k is RS; if i is S, F g If VS is the result, k is output as RS; if i is S, F g S, M, the output k is RM; if i is S, F g B, VB, the output k is LS; if i is M, F g VB and B, the output k is LM; if i is M, F g M, S, VS, the output k is M; if i is B, F g VB and B, the output k is RB; if i is B, F g M, S, the output k is VM; if i is B, F g If VS is the output k is LM; if i is VB, F g VB and B, the output k is VB; if i is VB, F g M, S, the output k is B; if i is VB, F g At VS, the output k is RB.
8. The control strategy of claim 6, wherein the grade i is a triangular membership function and the plow resistance F is g And a triangular membership function is adopted, and the front and rear torque distribution coefficients k adopt a membership function combining a trapezoidal membership function and the triangular membership function.
9. A four-wheel drive hybrid tractor control strategy according to claim 6, characterized in that the front-rear torque distribution coefficient k is inverse-fuzzy calculated using the center of gravity method.
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