CN116186467A - Excavator working point optimizing method based on comprehensive evaluation model - Google Patents

Excavator working point optimizing method based on comprehensive evaluation model Download PDF

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CN116186467A
CN116186467A CN202310184349.4A CN202310184349A CN116186467A CN 116186467 A CN116186467 A CN 116186467A CN 202310184349 A CN202310184349 A CN 202310184349A CN 116186467 A CN116186467 A CN 116186467A
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hydraulic pump
engine
pump
torque
excavator
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刘伟嵬
邓剑洋
张靖文
宋学官
桑勇
曹旭阳
牛东东
李国锋
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Dalian University of Technology
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D29/00—Controlling engines, such controlling being peculiar to the devices driven thereby, the devices being other than parts or accessories essential to engine operation, e.g. controlling of engines by signals external thereto
    • F02D29/04—Controlling engines, such controlling being peculiar to the devices driven thereby, the devices being other than parts or accessories essential to engine operation, e.g. controlling of engines by signals external thereto peculiar to engines driving pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D31/00—Use of speed-sensing governors to control combustion engines, not otherwise provided for
    • F02D31/001—Electric control of rotation speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/06—Control using electricity
    • F04B49/065—Control using electricity and making use of computers
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G06F17/11—Complex mathematical operations for solving equations, e.g. nonlinear equations, general mathematical optimization problems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B63/00—Adaptations of engines for driving pumps, hand-held tools or electric generators; Portable combinations of engines with engine-driven devices
    • F02B63/06—Adaptations of engines for driving pumps, hand-held tools or electric generators; Portable combinations of engines with engine-driven devices for pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2250/00—Engine control related to specific problems or objectives
    • F02D2250/18—Control of the engine output torque
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B17/00—Pumps characterised by combination with, or adaptation to, specific driving engines or motors
    • F04B17/05—Pumps characterised by combination with, or adaptation to, specific driving engines or motors driven by internal-combustion engines

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Abstract

An excavator working point optimizing method based on a comprehensive evaluation model. The method aims at stabilizing the working point by controlling the displacement of the hydraulic pump, and comprehensively considers the oil consumption of the excavator engine, the efficiency of the hydraulic pump and the load change of the excavator. Determining the relation between the fuel consumption of the engine and the rotation speed and torque of the engine according to the universal characteristic curve of the engine; determining the relation between the efficiency of the hydraulic pump and the rotation speed, the pressure difference and the displacement ratio of the hydraulic pump according to the experimental data of the hydraulic pump; the pressure value of the engine load is fitted to the torque value of the engine in a conversion manner. The working speed of the excavator is selected, the fuel consumption of the engine in actual working is low, the efficiency of the hydraulic pump is high, the fluctuation of the working point of the engine in the actual working process is small as a optimizing target, a comprehensive evaluation optimizing model is established, the importance degree of the engine fuel consumption and the load fluctuation is determined by setting a weight coefficient, the upper limit and the lower limit of the torque of the working point are determined according to the efficiency of the hydraulic pump, and finally the torque of the actual working point of the engine is determined.

Description

Excavator working point optimizing method based on comprehensive evaluation model
Technical Field
The invention belongs to the technical field of engineering machinery excavators, and particularly relates to an excavator working point optimizing method based on a comprehensive evaluation model.
Background
The engineering machinery is widely applied to construction sites such as mines, buildings and the like, and plays a remarkable role in promoting resource exploration and urban construction. There are many kinds of construction machines, and in the field of excavation, an excavator is one of main products. The excavator has the advantages of being firm, durable, full of power and the like, and has strong adaptability and high flexibility under severe and changeable working environments, so that the excavator is widely applied.
However, the existing excavator products have defects, wherein the main problems are large energy consumption and low energy utilization rate, and a great amount of energy waste is caused. Due to the huge land area, abundant mineral resources and rapidly developing city buildings in China, the excavator is still used in a large amount, which also results in a large amount of energy being wasted. Therefore, how to improve the energy utilization rate of the excavator and reduce the energy waste is a key problem which needs to be solved in the field of the current engineering machinery.
In the related studies, many students have reduced the fuel consumption of an excavator by optimizing the operating point of an engine. In general, an economic fuel consumption area is found on a universal characteristic curve of an engine, an operating point of the engine is set in the operating area, and the engine or a hydraulic pump connected with the engine is controlled in the working process of the excavator, so that the operating point of the engine is stabilized at the set operating point in the actual working process of the excavator. Many scholars do not consider the efficiency of the hydraulic pump and the fluctuation of the operating point during the adjustment in actual operation. If the efficiency of the hydraulic pump is low, a great amount of idle work is generated, and energy waste is caused; in the actual working process, when the fluctuation of the working point is large, namely, the fluctuation of the rotating speed and the torque of the working point is large in the regulating process, if the maximum torque which can be provided by the engine is reached at a certain moment, the phenomenon of speed-down flameout can possibly occur. Therefore, the invention provides an excavator working point optimizing method based on a comprehensive evaluation model aiming at the method of controlling the displacement of a hydraulic pump to stabilize the working point.
Disclosure of Invention
The invention provides an excavator working point optimizing method based on a comprehensive evaluation model. The method aims at the method for stabilizing the working point by controlling the displacement of the hydraulic pump, and comprehensively considers the oil consumption of the engine of the excavator, the efficiency of the hydraulic pump and the load change of the excavator, so as to provide the comprehensive performance evaluation method for the working point of the excavator. Determining the fuel consumption F of an engine on the basis of the universal characteristic curve of the engine e And the rotational speed n e Torque T e Is a relationship of (2); determining the efficiency E of a hydraulic pump from experimental data of the hydraulic pump P And the rotational speed n p Relationship of differential pressure Δp, displacement ratio β; the pressure value p of the engine load is calculated l Conversion fitting of torque value T of engine l . Selecting the working rotation speed n of the excavator w In terms of the fuel consumption F of the engine during actual operation ew Low efficiency E of hydraulic pump pw High, the fluctuation of the engine working point is small as the optimizing target in the actual working process, a comprehensive evaluation optimizing model is established, wherein the importance degree of the engine oil consumption and the load fluctuation is determined by setting a weight coefficient, and the torque of the working point is determined according to the efficiency of the hydraulic pumpUpper and lower limits, and finally determining the torque T of the actual working point of the engine r 。
The aim of the invention is realized by the following technical scheme:
the excavator working point optimizing method based on the comprehensive evaluation model comprises the following specific steps:
(1) Establishment of engine oil consumption model
As can be seen from the speed regulation graph (figure 1) of the engine, the engine can work in different gears, and the different gears correspond to the set rotating speed n e Different. Due to the action of the engine speed regulator, the rotation speed n of the engine can be maintained in the working process of the engine e Is unchanged. During operation of the engine, its operating point will change on the governor curve as the load changes. When the load pressure p l When increasing, the engine operating point moves upwards, the torque value T e An increase; when the load pressure p l When decreasing, the engine operating point moves downwards, torque value T e Descending.
From the universal characteristic diagram (FIG. 2) of the engine, the fuel consumption rate η of the engine is known e Output power P e And the rotation speed n e And its torque T e Related to the following. The external characteristic curve, the equal fuel consumption rate curve and the equal power curve exist on the universal characteristic curve, and the external characteristic curve represents the maximum torque value T which can be provided by the engine at different rotating speeds MAX The fuel consumption rate eta at a point on the equal fuel consumption rate curve e The same, the power P at a point on the equal power curve e The same applies. Wherein the fuel consumption F e And output power P e Fuel consumption rate eta e The relationship of (2) is as follows:
F e ＝P e ·η e (1)
polynomial fitting is carried out on the universal characteristic curve of the engine, so that the fuel consumption F of the engine can be obtained e And the rotational speed n e Torque T e Is a relationship of (3). According to the speed regulation curve of the engine, the excavator rotates under the condition that the gear is determined when the excavator worksThe speed remains unchanged. Selecting a rotating speed according to the working gear as the rotating speed n of the excavator during working e . When the rotation speed n e The fuel consumption F of the engine can be obtained after the determination e With its torque T e Functional relation of (c), namely:
F e ＝f e (T e ) (2)
establishing a graph of fuel consumption of the engine and the rotation speed according to a functional relation (figure 3), and finding that when the rotation speed n of the engine is e At a certain time, its fuel consumption F e With its torque T e Positive correlation.
Therefore, if the fuel consumption F of the hydraulic excavator is desired to be reduced e Can reduce the torque T e 。
(2) Hydraulic pump efficiency model building
It can be seen from the hydraulic structure diagram (fig. 4) of the positive flow plunger type variable pump that the hydraulic structure diagram consists of two sub pumps, namely a front pump 1 and a rear pump 2, which respectively provide hydraulic power for different execution mechanisms of the excavator. Efficiency E of hydraulic pump p And the rotation speed n p The differential pressure delta p and the displacement ratio beta are related, and the hydraulic pump is respectively tested at different rotating speeds n p Efficiency at different differential pressures Δp, different displacement ratios β. Can obtain the hydraulic pump efficiency E p And the rotation speed n p The pressure difference Δp, the displacement ratio β (fig. 5). Wherein the differential pressure is defined by the load pressure p l The hydraulic pump is directly driven by the engine, so that the rotation speeds of the hydraulic pump and the engine are the same. The method can obtain the following steps:
Δp＝p l (3)
n p ＝n e (4)
so that the efficiency E of the hydraulic pump can be adjusted p The only variables to be improved are their displacement ratios beta, beta.E [0,1 ]]And β is generally not equal to 0. From a review of FIG. 5, it can be found that E p Positively correlated with beta. Displacement V of hydraulic pump p The relation with the displacement ratio beta is as follows:
V p ＝V MAX ·β (5)
wherein ,VMAX Is hydraulic pressureMaximum displacement of the pump.
So if it is desired to increase the efficiency E of the hydraulic pump p Can increase the displacement ratio beta, i.e. the displacement V p 。
(3) Scaled fit of load pressure
Power P of engine e The method comprises the following steps:
Figure BDA0004103216940000041
in the formula ,Pe In kilowatts (kW); t (T) e The unit is cow per meter (N.m); n is n e In revolutions per minute (r/min).
The outlet pressure of the hydraulic pump is the load pressure thereof. Since the hydraulic pump consists of a front pump and a rear pump, the power of the hydraulic pump is the sum of the power of the two sub pumps, namely:
Figure BDA0004103216940000042
in the formula ,Pp In kilowatts (kW);
p p1 the outlet pressure (MPa) of the front pump of the hydraulic pump;
p p2 the outlet pressure (MPa) of the rear pump of the hydraulic pump;
Q p1 output flow (L/min) of a front pump of the hydraulic pump;
Q p2 output flow (L/min) of a rear pump of the hydraulic pump; .
The relationship between the flow and displacement of the front and rear pumps of the hydraulic pump is:
Q p1 ＝V p1 ·n p (8)
Q p2 ＝V p2 ·n p (9)
in the formula ,Vp1 Displacement (L/r) of the front pump of the hydraulic pump;
V p2 displacement (L/r) of the rear pump for the hydraulic pump;
n p is the rotation speed (r/min) of the transmission shaft of the hydraulic pump.
Substitution of formulas (8) and (9) into (7) yields:
Figure BDA0004103216940000051
the engine is directly connected with the hydraulic pump, and the power transfer relationship between the engine and the hydraulic pump is as follows:
P e ＝P p ·η ep ，η ep ∈(0,1] (11)
wherein ηep Is the power transfer efficiency between the engine and the hydraulic pump.
Let eta assume ep When=1, substituting (4), (6), and (10) into (11) yields:
Figure BDA0004103216940000052
by measuring the load pressure p of the front and rear pumps during the working time p1 and pp2 Summing to obtain the outlet pressure p of the hydraulic pump p 。
Figure BDA0004103216940000053
Figure BDA0004103216940000054
Figure BDA0004103216940000055
Figure BDA0004103216940000056
Figure BDA0004103216940000061
Figure BDA0004103216940000062
wherein ,
Figure BDA0004103216940000063
i=1, 2,3, …, N, which is the load pressure (N) of the pump before the operating time;
Figure BDA0004103216940000064
i=1, 2,3, …, N, which is the load pressure (N) of the post-pump during the operating time; />
Figure BDA0004103216940000065
I=1, 2,3, …, N for the load pressure sum (N) of the front and rear pumps during the operating time.
The minimum of the formulas (16), (17) and (18) is obtained
Figure BDA0004103216940000066
and />
Figure BDA0004103216940000067
Fitting load pressures for the front, rear and hydraulic pumps.
And then calculate the fitting demand torque of the hydraulic pump
Figure BDA0004103216940000068
The method comprises the following steps:
Figure BDA0004103216940000069
wherein ,VpMAX Is the maximum displacement of the hydraulic pump.
Respectively at
Figure BDA00041032169400000610
Find the minimum and maximum values asMinimum load pressure p of hydraulic pump pmin And maximum load pressure p pmax . And respectively find the minimum required torque T of the hydraulic pump min And a maximum required torque T max The method comprises the following steps:
Figure BDA00041032169400000611
Figure BDA00041032169400000612
at p respectively p1 and pp2 Find the maximum load pressure p of the front pump and the rear pump p1max and pp2max Maximum required torque T of front pump and rear pump is obtained 1max and T2max 。
Figure BDA00041032169400000613
Figure BDA00041032169400000614
(4) Building of comprehensive evaluation model
Assuming that the torque value of the working point of the excavator obtained by optimizing is T r 。
1. Engine oil consumption
During operation of the engine, its operating point will change on the governor curve as the load changes. When the load pressure p l When increasing, the engine working point moves upwards, the torque value T e An increase; when the load pressure p l When decreasing, the engine operating point moves downwards, the torque value T e Descending. As can be seen from FIG. 6, when the engine speed n e At a certain time, its fuel consumption F e With its torque T e Positive correlation. If it is desired to reduce the fuel consumption F of the hydraulic excavator e Can reduce the torque T e 。
The engine oil consumption evaluation model is established as follows:
Figure BDA0004103216940000071
the optimizing target is the order f 1 (T r ) As small as possible.
2. Efficiency of hydraulic pump
Because of formulas (3) and (4), the efficiency E of the hydraulic pump can be adjusted p The only variables to be improved are their displacement ratios beta, beta.E [0,1 ]]And β is generally not equal to 0. So if it is desired to increase the efficiency E of the hydraulic pump p The displacement ratio beta thereof may be increased. It was found according to formula (5) that the displacement V can be increased p To increase the displacement ratio beta and further to improve the efficiency E of the hydraulic pump p 。
As can be seen from equation (12), when the operating point is set to T r During actual operation, the load pressure p of the front pump and the rear pump p1 and pp2 In order to make T e Trend T r By adjusting the displacement V of the hydraulic pump p1 and Vp2 . When T is e Greater than T r When V needs to be reduced p1 and Vp2 The method comprises the steps of carrying out a first treatment on the surface of the When T is e Less than T r When V needs to be increased p1 and Vp2 . As can be seen from fig. 3, T is set to reduce the fuel consumption of the engine r The lower the setting, the better, but the V is reduced according to equation (5) p1 and Vp2 Resulting in a decrease in efficiency of the hydraulic pump. If T r Too high a setting, the fuel consumption F of the engine is known from FIG. 3 e Will be high and if p p1 and pp2 Reaching maximum value, T at that time e Still less than T r Then increase V p1 and Vp2 Regulation T e To T r In the process of (2), beta.epsilon.0, 1]When β=1, T e Has reached the limit if T e Or is smaller than T r Then T will not be adjustable e To T r . So in order to avoid the occurrence of the two conditions, T r Upper and lower limits are required for the setting of (c).
The efficiency of the hydraulic pump is preferably set at75% or more. From FIG. 5 and experimental data (the load pressure of the front and rear pumps varies from 0Mpa to 30Mpa in experimental data), it is known that the displacement ratio of the hydraulic pump has a lower limit β min ∈[0.4,0.6]. According to formula (21), p p1 and pp2 And p is the sum of p All reach a maximum value p pmax And V is p1 and Vp2 All reach V MAX At the time, T is determined e Is maximum T max . When the displacement ratio of the hydraulic pump is its lower limit beta according to the formulas (5) and (12) min At the time, the torque value T of the working point of the excavator can be deduced r The lower limit of (2) is:
Figure BDA0004103216940000081
t is determined from formulas (20) and (21) min and Tmax Average value T of (2) ave As shown in equation (34).
Figure BDA0004103216940000082
wherein ,Tave ＝0.5·T min +0.5·T max Near or even greater than T max ·β min Therefore, T can be taken ave As T r Lower limit of (2).
The torque value T of the working point of the excavator obtained by optimizing r The required torques assigned to the front pump and the rear pump of the hydraulic pump are respectively:
Figure BDA0004103216940000083
Figure BDA0004103216940000084
wherein ,Tr1 ≤T 1max ，T r2 ≤T 2max That is to say,
Figure BDA0004103216940000085
torque value T capable of pushing out working point of excavator r The upper limit of (2) is:
Figure BDA0004103216940000086
3. load fluctuation
The smallest value obtained according to formula (18)
Figure BDA0004103216940000091
Fitting load pressure for hydraulic pump, obtained according to formula (19)>
Figure BDA0004103216940000092
The cumulative distance to the required torque value of the hydraulic pump at each moment is the smallest sum, i.e. the load fluctuation is the smallest. Load fluctuations represent the sum of the distances that the torque of the hydraulic pump needs to be adjusted to the torque of the set operating point from the load pressure fit at each moment in time in actual operation. The larger the distance sum, the larger the load fluctuation, the larger the distance the hydraulic pump needs to adjust, and the more difficult the hydraulic pump is to adjust.
The load fluctuation evaluation model is established as follows:
Figure BDA0004103216940000093
/>
the optimizing target is the order f 2 (T r ) As small as possible.
4. Comprehensive evaluation model
Order the
Figure BDA0004103216940000094
The comprehensive evaluation model is built by the comprehensive steps (24) and (30) as follows:
f(x 1 ,x 2 ,T r )＝x 1 ·f 1 (T r )+x 2 ·f 2 (T r ),T rmin ≤T r ≤T rmax (31)
Figure BDA0004103216940000095
x 1 +x 2 ＝1 (33)
wherein x1 ,x 2 The weight coefficients represent the specific weights of the two evaluation models.
(5) Optimizing working point of excavator
The optimization of the working point of the excavator aims at finding the T which minimizes (32) r 。
According to different emphasis targets, x can be adjusted according to formula (33) 1 ,x 2 Weight coefficient size of (c). The larger the weight coefficient, the higher the importance of the evaluation model.
The specific optimizing process is shown in the flowchart (fig. 6) of the optimizing process.
The invention has the beneficial effects that: aiming at the engine working point stabilizing method that the displacement of the hydraulic pump is controlled to stabilize the working point, three factors of oil consumption of the engine, efficiency of the hydraulic pump and fluctuation of load are comprehensively considered, a comprehensive evaluation model is built according to the oil consumption of the engine, the efficiency of the hydraulic pump and the fluctuation of the load respectively, the importance degree of the oil consumption of the engine and the fluctuation of the load is evaluated by setting a weight coefficient, the upper limit and the lower limit of the torque of the working point are determined according to the efficiency of the hydraulic pump, and the best torque of the engine working point is obtained by optimizing the comprehensive evaluation model.
Drawings
The speed regulation diagram of the engine of fig. 1.
FIG. 2 is a graph of the universal behavior of the engine.
Fig. 3 is a graph of fuel consumption versus rotational speed for an engine.
Fig. 4 is a hydraulic structure diagram of a positive-flow plunger type variable displacement pump.
FIG. 5 is a graph of hydraulic pump efficiency as a function of independent variables.
FIG. 6 is a flowchart of the optimization process.
FIG. 7 is a view of the result of the optimizing calculation
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments.
The method comprises the following specific implementation steps:
1. determining gear of engine, i.e. determining speed regulation curve of engine in current working process, and determining current working rotation speed n e The rated rotation speed of the engine is 1700r/min. Engine fuel consumption rate eta in universal characteristic curve of engine e Output power P e And the rotational speed n e Torque T e Polynomial fitting is performed on the relation of (2) and the fuel consumption F of the engine can be obtained according to the formula (1) e And the rotational speed n e Torque T e The relation of formula (2). Determining the rotational speed n from the external characteristic of the engine e Maximum torque value T that lower engine can provide MAX 。
2. Respectively testing the hydraulic pump at different rotation speeds n p Efficiency at different differential pressures Δp, different displacement ratios β. Can obtain the hydraulic pump efficiency E p And the rotation speed n p And the relation diagram of the differential pressure delta p and the displacement ratio beta is a hydraulic pump efficiency model. At a rotational speed n p When the differential pressure Δp is constant, the hydraulic pump efficiency E is found p Positively correlated with displacement ratio beta, i.e. with displacement V p Positive correlation.
3. Collecting the load pressure of the excavator during working, namely the outlet pressure p of the front pump and the rear pump p1 and pp2 Calculating the outlet pressure p of the hydraulic pump according to formula (15) p . Determining the fitted load pressure of the front and rear pumps according to equations (16), (17) and (18)
Figure BDA0004103216940000111
Fitting load pressure to hydraulic pump +.>
Figure BDA0004103216940000112
Wherein formulae (16), formulae (17) and (18) are:
Figure BDA0004103216940000113
Figure BDA0004103216940000114
Figure BDA0004103216940000115
TABLE 1 calculation of pressure values
Figure BDA0004103216940000116
Obtaining a fitting required torque of the hydraulic pump according to (19)
Figure BDA0004103216940000117
The minimum required torque T of the hydraulic pump is determined according to the formulas (20) and (21) min And a maximum required torque T max . Maximum required torques T of a front pump and a rear pump of the hydraulic pump are obtained according to formulas (22) and (23), respectively 1max 、T 2max . Wherein the maximum displacement V of the hydraulic pump MAX 125ml/r, maximum output torque T of the engine at 1700r/min rated speed MAX 950N.m.
Table 2 torque value calculation results
Figure BDA0004103216940000121
According to formula (33) and x is selected 1 ＝0.6、x 2 ＝0.4，x 1 ＝0.5、x 2＝0.5 and x1 ＝0.4、x 2 Three cases =0.6, representing the degree of emphasis on engine fuel consumption and load fluctuation, respectively. . Built up according to formulae (27), (28) and (32)The comprehensive evaluation model of the working point of the vertical excavator is as follows:
Figure BDA0004103216940000122
Figure BDA0004103216940000123
Figure BDA0004103216940000124
simplification of formulas (37), (38) and (39) gives:
Figure BDA0004103216940000125
Figure BDA0004103216940000126
Figure BDA0004103216940000127
x is plotted according to equations (40) - (42) 1 ＝0.6、x 2 ＝0.4，x 1 ＝0.5、x 2＝0.5 and x1 ＝0.4、x 2 A graph of the calculation result of the comprehensive evaluation model as the torque value of the engine operating point changes in different operating phases in three cases=0.6 is shown in fig. 7.
The operating point torque of the engine is 678 (n·m) according to fig. 7.

Claims (1)

1. The excavator working point optimizing method based on the comprehensive evaluation model is characterized by comprising the following specific steps of:
(1) Establishment of engine oil consumption model
According to speed regulation of the engineThe graph shows that the engine can work in different gears corresponding to the set rotation speed n e Different; due to the action of the engine speed regulator, the rotation speed n of the engine can be maintained in the working process of the engine e Unchanged; in the working process of the engine, the working point of the engine can be changed on a speed regulation curve along with the change of the load; when the load pressure p l When increasing, the engine operating point moves upwards, the torque value T e An increase; when the load pressure p l When decreasing, the engine operating point moves downwards, torque value T e Descending;
from the universal characteristic diagram of the engine, the fuel consumption rate eta of the engine is known e Output power P e And the rotation speed n e And its torque T e Related to; the external characteristic curve, the equal fuel consumption rate curve and the equal power curve exist on the universal characteristic curve, and the external characteristic curve represents the maximum torque value T which can be provided by the engine at different rotating speeds MAX The fuel consumption rate eta at a point on the equal fuel consumption rate curve e The same, the power P at a point on the equal power curve e The same; wherein the fuel consumption F e And output power P e Fuel consumption rate eta e The relationship of (2) is as follows:
F e ＝P e ·η e (1)
polynomial fitting is carried out on the universal characteristic curve of the engine, so that the fuel consumption F of the engine can be obtained e And the rotational speed n e Torque T e Is a relationship of (2); according to the speed regulation curve of the engine, the rotation speed of the excavator is kept unchanged under the condition that the gear is determined when the excavator works; selecting a rotating speed according to the working gear as the rotating speed n of the excavator during working e The method comprises the steps of carrying out a first treatment on the surface of the When the rotation speed n e The fuel consumption F of the engine can be obtained after the determination e With its torque T e Functional relation of (c), namely:
F e ＝f e (T e ) (2)
establishing a relation diagram of fuel consumption and rotation speed of the engine according to the functional relation, and finding that when the rotation speed n of the engine is the same e At a certain time, its fuel consumption F e With its torque T e Positive correlation;
therefore, if the fuel consumption F of the hydraulic excavator is desired to be reduced e Can reduce the torque T e ；
(2) Hydraulic pump efficiency model building
The hydraulic structure diagram of the positive flow plunger type variable pump shows that the hydraulic structure diagram consists of two sub pumps, namely a front pump 1 and a rear pump 2, which are used for providing hydraulic power for different execution mechanisms of the excavator; efficiency E of hydraulic pump p And the rotation speed n p The differential pressure delta p and the displacement ratio beta are related, and the hydraulic pump is respectively tested at different rotating speeds n p Efficiency at different differential pressures Δp, different displacement ratios β; can obtain the hydraulic pump efficiency E p And the rotation speed n p A graph of differential pressure Δp versus displacement ratio β; wherein the differential pressure is defined by the load pressure p l The hydraulic pump is directly driven by the engine, so that the rotation speeds of the hydraulic pump and the engine are the same; the method can obtain the following steps:
Δp＝p l (3)
n p ＝n e (4)
so that the efficiency E of the hydraulic pump can be adjusted p The only variables to be improved are their displacement ratios beta, beta.E [0,1 ]]And β is generally not equal to 0; observing the efficiency E of the hydraulic pump p And the rotation speed n p The relationship between the differential pressure Deltap and the displacement ratio beta can be found to be E p Positively correlated with beta; displacement V of hydraulic pump p The relation with the displacement ratio beta is as follows:
V p ＝V MAX ·β (5)
wherein ,VMAX Maximum displacement for the hydraulic pump;
so if it is desired to increase the efficiency E of the hydraulic pump p Can increase the displacement ratio beta, i.e. the displacement V p ；
(3) Scaled fit of load pressure
Power P of engine e The method comprises the following steps:
Figure FDA0004103216930000021
in the formula ,Pe The unit is kilowatt; t (T) e The unit is cow per meter; n is n e In revolutions per minute;
the outlet pressure of the hydraulic pump is the load pressure; since the hydraulic pump consists of a front pump and a rear pump, the power of the hydraulic pump is the sum of the power of the two sub pumps, namely:
Figure FDA0004103216930000031
in the formula ,Pp The unit is kilowatt;
p p1 the outlet pressure of the front pump of the hydraulic pump;
p p2 the outlet pressure of the rear pump of the hydraulic pump;
Q p1 the output flow of the front pump of the hydraulic pump;
Q p2 the output flow of the rear pump of the hydraulic pump;
the relationship between the flow and displacement of the front and rear pumps of the hydraulic pump is:
Q p1 ＝V p1 ·n p (8)
Q p2 ＝V p2 ·n p (9)
in the formula ,Vp1 The displacement of the front pump of the hydraulic pump;
V p2 the displacement of the rear pump of the hydraulic pump;
n p the rotation speed of the transmission shaft of the hydraulic pump;
substitution of formulas (8) and (9) into (7) yields:
Figure FDA0004103216930000032
the engine is directly connected with the hydraulic pump, and the power transfer relationship between the engine and the hydraulic pump is as follows:
P e ＝P p ·η ep ，η ep ∈(0,1] (11)
wherein ηep For engines andpower transfer efficiency between hydraulic pumps;
let eta assume ep When=1, substituting (4), (6), and (10) into (11) yields:
Figure FDA0004103216930000033
by measuring the load pressure p of the front and rear pumps during the working time p1 and pp2 Summing to obtain the outlet pressure p of the hydraulic pump p ；
Figure FDA0004103216930000041
Figure FDA0004103216930000042
Figure FDA0004103216930000043
Figure FDA0004103216930000044
Figure FDA0004103216930000045
/>
Figure FDA0004103216930000046
wherein ,
Figure FDA0004103216930000047
i=1, 2,3, …, n, the load pressure of the front pump during the on-time;
Figure FDA0004103216930000048
i=1, 2,3, …, n, the load pressure of the post pump during the on-time;
Figure FDA0004103216930000049
i=1, 2,3, …, n, the sum of the load pressures of the front and rear pumps during the operating time;
the minimum of the formulas (16), (17) and (18) is obtained
Figure FDA00041032169300000410
and />
Figure FDA00041032169300000411
Fitting load pressures for the front pump, rear pump, and hydraulic pump;
and then calculate the fitting demand torque of the hydraulic pump
Figure FDA00041032169300000412
The method comprises the following steps:
Figure FDA00041032169300000413
wherein ,VpMAX Maximum displacement for the hydraulic pump;
respectively at
Figure FDA00041032169300000414
Find the minimum and maximum values as the minimum load pressure p of the hydraulic pump pmin And maximum load pressure p pmax The method comprises the steps of carrying out a first treatment on the surface of the And respectively find the minimum required torque T of the hydraulic pump min And a maximum required torque T max The method comprises the following steps:
Figure FDA00041032169300000415
Figure FDA00041032169300000416
at p respectively p1 and pp2 Find the maximum load pressure p of the front pump and the rear pump p1max and pp2max Maximum required torque T of front pump and rear pump is obtained 1max and T2max ；
Figure FDA0004103216930000051
Figure FDA0004103216930000052
(4) Building of comprehensive evaluation model
Assuming that the torque value of the working point of the excavator obtained by optimizing is T r ；
1. Engine oil consumption
In the working process of the engine, the working point of the engine can be changed on a speed regulation curve along with the change of the load; when the load pressure p l When increasing, the engine working point moves upwards, the torque value T e An increase; when the load pressure p l When decreasing, the engine operating point moves downwards, the torque value T e Descending; when the engine speed n e At a certain time, its fuel consumption F e With its torque T e Positive correlation; if it is desired to reduce the fuel consumption F of the hydraulic excavator e Can reduce the torque T e ；
The engine oil consumption evaluation model is established as follows:
Figure FDA0004103216930000053
the optimizing target is the order f 1 (T r ) As small as possible；
2. Efficiency of hydraulic pump
Because of formulas (3) and (4), the efficiency E of the hydraulic pump can be adjusted p The only variables to be improved are their displacement ratios beta, beta.E [0,1 ]]And β is generally not equal to 0; so if it is desired to increase the efficiency E of the hydraulic pump p The displacement ratio beta of the valve can be increased; it was found according to formula (5) that the displacement V can be increased p To increase the displacement ratio beta and further to improve the efficiency E of the hydraulic pump p ；
As can be seen from equation (12), when the operating point is set to T r During actual operation, the load pressure p of the front pump and the rear pump p1 and pp2 In order to make T e Trend T r By adjusting the displacement V of the hydraulic pump p1 and Vp2 The method comprises the steps of carrying out a first treatment on the surface of the When T is e Greater than T r When V needs to be reduced p1 and Vp2 The method comprises the steps of carrying out a first treatment on the surface of the When T is e Less than T r When V needs to be increased p1 and Vp2 The method comprises the steps of carrying out a first treatment on the surface of the In order to reduce the fuel consumption of the engine, T is r The lower the setting, the better, but the V is reduced according to equation (5) p1 and Vp2 Resulting in reduced efficiency of the hydraulic pump; if T r Too high an engine fuel consumption F e Will be high and if p p1 and pp2 Reaching maximum value, T at that time e Still less than T r Then increase V p1 and Vp2 Regulation T e To T r In the process of (2), beta.epsilon.0, 1]When β=1, T e Has reached the limit if T e Or is smaller than T r Then T will not be adjustable e To T r The method comprises the steps of carrying out a first treatment on the surface of the So in order to avoid the occurrence of the two conditions, T r Upper and lower limits are required for setting;
the efficiency of the hydraulic pump is preferably set to be more than 75%; according to the efficiency E of the hydraulic pump p And the rotation speed n p The relation graph of the differential pressure delta p and the displacement ratio beta and experimental data can know that the lower limit beta of the displacement ratio of the hydraulic pump min ∈[0.4,0.6]The method comprises the steps of carrying out a first treatment on the surface of the According to formula (21), p p1 and pp2 And p is the sum of p All reach a maximum value p pmax And V is p1 and Vp2 All reach V MAX At the time, T is determined e Is maximum T max The method comprises the steps of carrying out a first treatment on the surface of the When the displacement ratio of the hydraulic pump is its lower limit beta according to the formulas (5) and (12) min At the time, the torque value T of the working point of the excavator can be deduced r The lower limit of (2) is:
Figure FDA0004103216930000061
t is determined from formulas (20) and (21) min and Tmax Average value T of (2) ave As shown in formula (34);
Figure FDA0004103216930000062
wherein ,Tave ＝0.5·T min +0.5·T max Near or even greater than T max ·β min Therefore, T can be taken ave As T r Lower limit of (2);
the torque value T of the working point of the excavator obtained by optimizing r The required torques assigned to the front pump and the rear pump of the hydraulic pump are respectively:
Figure FDA0004103216930000063
Figure FDA0004103216930000064
wherein ,Tr1 ≤T 1max ，T r2 ≤T 2max That is to say,
Figure FDA0004103216930000065
torque value T capable of pushing out working point of excavator r The upper limit of (2) is:
Figure FDA0004103216930000071
3. load fluctuation
The smallest value obtained according to formula (18)
Figure FDA0004103216930000072
Fitting load pressure for hydraulic pump, obtained according to formula (19)>
Figure FDA0004103216930000076
The sum of the cumulative distance to the required torque value of the hydraulic pump at each moment is minimum, i.e. the load fluctuation is minimum; load fluctuations represent the sum of distances that require the hydraulic pump to adjust the torque from the load pressure fit at each moment to the torque at the set operating point during actual operation; the larger the distance sum is, the larger the load fluctuation is, the larger the distance the hydraulic pump needs to be adjusted is, and the more difficult the hydraulic pump is to be adjusted;
the load fluctuation evaluation model is established as follows:
Figure FDA0004103216930000073
the optimizing target is the order f 2 (T r ) As small as possible;
4. comprehensive evaluation model
Let T rmin ＝T ave ，
Figure FDA0004103216930000074
The comprehensive evaluation model is built by the comprehensive steps (24) and (30) as follows:
f(x 1 ,x 2 ,T r )＝x 1 ·f 1 (T r )+x 2 ·f 2 (T r ),T rmin ≤T r ≤T rmax (31)
Figure FDA0004103216930000075
x 1 +x 2 ＝1 (33)
wherein x1 ,x 2 The weight coefficients respectively represent the proportion of the two evaluation models;
(5) Optimizing working point of excavator
The optimization of the working point of the excavator aims at finding the T which minimizes (32) r ；
According to different emphasis targets, x can be adjusted according to formula (33) 1 ,x 2 The weight coefficient size of (2);
the larger the weight coefficient, the higher the importance of the evaluation model.
CN202310184349.4A 2023-03-01 2023-03-01 Excavator working point optimizing method based on comprehensive evaluation model Pending CN116186467A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116450654A (en) * 2023-06-12 2023-07-18 北谷电子股份有限公司 Energy consumption optimization method and system for excavator based on N-T database

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116450654A (en) * 2023-06-12 2023-07-18 北谷电子股份有限公司 Energy consumption optimization method and system for excavator based on N-T database

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