A method for excavator working point optimization based on comprehensive evaluation model

Abstract

A kind of excavator working point optimization method based on comprehensive evaluation model.For the method of stabilizing working point by controlling the displacement of hydraulic pump, the fuel consumption of excavator engine, the efficiency of hydraulic pump and the load variation of excavator are comprehensively considered.According to the engine universal characteristic curve, the relationship between the fuel consumption of engine and its speed, torque is determined;According to the experimental data of hydraulic pump, the relationship between the efficiency of hydraulic pump and its speed, differential pressure, displacement ratio is determined;The pressure value of engine load is converted and fitted into the torque value of engine.The working speed of excavator is selected, the fuel consumption of engine is low, the efficiency of hydraulic pump is high when working, the fluctuation of engine working point is small during actual work, and the comprehensive evaluation optimization model is established, wherein the importance of engine fuel consumption and load fluctuation is determined by setting weight coefficient, the upper and lower limits of working point torque are determined according to the efficiency of hydraulic pump, and finally the torque of actual working point of engine is determined.

Description

Technical Field

[0001] The present invention belongs to the technical field of engineering machinery excavators, and in particular relates to an excavator working point optimization method based on a comprehensive evaluation model. Background Art

[0002] Construction machinery is widely used in mining, construction, and other construction sites, significantly advancing resource exploration and urban development. While there are many types of construction machinery, excavators are a key component in the excavation sector. Excavators are widely used due to their durability, powerful performance, and adaptability to harsh and changing operating environments.

[0003] However, current excavators still have drawbacks, the most significant of which is their high energy consumption and low energy utilization, resulting in significant energy waste. Due to my country's vast land area, abundant mineral resources, and rapidly developing urban construction, excavators are still widely used, resulting in significant energy waste. Therefore, improving excavator energy utilization and reducing energy waste are key issues that urgently need to be addressed in the field of construction machinery.

[0004] In related research, many scholars have reduced the fuel consumption of excavators by optimizing the working point of the engine. Generally, the economic fuel consumption area is found on the universal characteristic curve of the engine, and the working point of the engine is set in this working area. During the operation of the excavator, the engine or the hydraulic pump connected to the engine is controlled so that the working point of the engine is stabilized at the set working point during the actual operation of the excavator. However, many scholars have not considered the efficiency of the hydraulic pump and the fluctuation of the working point during the adjustment process during the actual working process. If the efficiency of the hydraulic pump is low, a lot of useless work will be generated, which will also cause energy waste; and in the actual working process, during the adjustment process, when the working point fluctuates greatly, that is, the speed and torque of the working point fluctuate greatly during the adjustment process, if the maximum torque that the engine can provide is reached at a certain moment, the engine may stall. Therefore, the patent of this invention proposes a method for optimizing the working point of an excavator based on a comprehensive evaluation model, targeting the method of stabilizing the working point by controlling the displacement of the hydraulic pump. Summary of the Invention

[0005] This invention proposes a method for optimizing the working point of an excavator based on a comprehensive evaluation model. This method is based on the method of stabilizing the working point by controlling the displacement of the hydraulic pump. It comprehensively considers the fuel consumption of the excavator engine, the efficiency of the hydraulic pump, and the load variation of the excavator to propose a comprehensive performance evaluation method for the working point of the excavator. The engine fuel consumption F is determined based on the universal characteristic curve of the engine. e and its speed n e , torque T eDetermine the efficiency E of the hydraulic pump based on the experimental data of the hydraulic pump P and its speed n p , pressure difference Δp, displacement ratio β; the pressure value p of the engine load l Convert the fitted value into the engine torque value T l . Select the excavator's operating speed n w , based on the actual fuel consumption of the engine during operation F ew Low, hydraulic pump efficiency E pw The optimization goal is to minimize the fluctuation of the engine operating point during the actual working process. A comprehensive evaluation optimization model is established, in which the importance of engine fuel consumption and load fluctuation is determined by setting weight coefficients, and the upper and lower limits of the operating point torque are determined according to the efficiency of the hydraulic pump. Finally, the actual engine operating point torque T is determined. r .

[0006] The object of the present invention is achieved through the following technical solutions:

[0007] A method for optimizing the working point of an excavator based on a comprehensive evaluation model. The specific steps of the method are as follows:

[0008] (1) Establishment of engine fuel consumption model

[0009] According to the engine speed control curve ( Figure 1 ) It can be seen that the engine can be operated in different gears, and different gears correspond to the set speed n e Due to the function of the engine speed governor, the engine can maintain its speed during operation. e During the operation of the engine, its operating point will change on the speed control curve as the load changes. l When it increases, the engine operating point moves upward, and the torque value T e Increase; when the load pressure p l When it decreases, the engine operating point moves downward and the torque value T e decline.

[0010] According to the engine's universal characteristic curve ( Figure 2 ) we can see that the fuel consumption rate of the engine is η e , output power P e Its speed n e and its torque T e There are external characteristic curves, equal fuel consumption rate curves and equal power curves on the universal characteristic curve. The external characteristic curve represents the maximum torque value T that the engine can provide at different speeds. MAX , the fuel consumption rate η at a point on the equal fuel consumption rate curve e Similarly, the power P at a point on the isopower curvee The same. Among them, the fuel consumption F e and output power P e , fuel consumption rate η e The relationship is as follows:

[0011] F e =P e ·η e (1)

[0012] By fitting the universal characteristic curve of the engine with a polynomial, the fuel consumption of the engine F can be obtained. e and its speed n e , torque T e According to the engine speed curve, when the excavator is working, its speed remains unchanged when the gear is determined. A speed is selected according to the working gear as the speed n of the excavator when working. e When the speed n e After determination, the fuel consumption of the engine F can be obtained e With its torque T e The functional relationship is:

[0013] F e =f e (T e ) (2)

[0014] According to the functional relationship, the relationship diagram between the fuel consumption and the speed of the engine is established ( Figure 3 ), it is found that when the engine speed n e At a certain time, its fuel consumption F e With its torque T e Positive correlation.

[0015] Therefore, if you want to reduce the fuel consumption of hydraulic excavators, e , which can reduce its torque T e .

[0016] (2) Establishment of hydraulic pump efficiency model

[0017] From the hydraulic structure diagram of the positive flow plunger variable pump ( Figure 4 ) It can be found that it consists of two sub-pumps, namely front pump 1 and rear pump 2, which provide hydraulic power for different actuators of the excavator. The efficiency of the hydraulic pump E p Its speed n p , pressure difference Δp, displacement ratio β, respectively test the hydraulic pump at different speeds n p , the efficiency under different pressure difference Δp and different displacement ratio β. The hydraulic pump efficiency E can be obtained p Its speed n p , pressure difference Δp, displacement ratio β (Figure 5 ). Among them, the pressure difference is determined by the load pressure p l The hydraulic pump is directly driven by the engine, so the two have the same speed.

[0018] Δp=p l (3)

[0019] n p =n e (4)

[0020] Therefore, the efficiency of the hydraulic pump can be adjusted to E p The only variable that is improved is the displacement ratio β, β∈[0,1] and β is generally not equal to 0. Figure 5 Can be found E p Positively correlated with β. The displacement of the hydraulic pump V p The relationship with its displacement ratio β is:

[0021] V p =V MAX β (5)

[0022] Among them, V MAX is the maximum displacement of the hydraulic pump.

[0023] Therefore, if you want to increase the efficiency of the hydraulic pump E p , you can increase its displacement ratio β, that is, increase its displacement V p .

[0024] (3) Conversion and fitting of load pressure

[0025] Engine power P e for:

[0026]

[0027] Where, P e The unit is kilowatt (kW); T e The unit is Newton per meter (N·m); n e The unit is revolutions per minute (r / min).

[0028] The outlet pressure of the hydraulic pump is its load pressure. Since the hydraulic pump consists of two parts, the front pump and the rear pump, the power of the hydraulic pump is the sum of the power of the two sub-pumps, that is:

[0029]

[0030] Where, P p The unit is kilowatt (kW);

[0031] p p1 is the outlet pressure of the hydraulic pump front pump (MPa);

[0032] p p2 is the outlet pressure of the hydraulic pump (MPa) after the pump;

[0033] Q p1 is the output flow of the hydraulic pump (L / min) before the pump;

[0034] Q p2 is the output flow of the hydraulic pump (L / min) after the pump.

[0035] The relationship between the flow and displacement of the hydraulic pump before and after the pump is:

[0036] Q p1 = V p1 · n p (8)

[0037] Q p2 = V p2 · n p (9)

[0038] wherein V p1 is the displacement of the hydraulic pump (L / r) before the pump;

[0039] V p2 is the displacement of the hydraulic pump (L / r) after the pump;

[0040] n p is the rotational speed of the hydraulic pump drive shaft (r / min).

[0041] Substituting equations (8) and (9) into (7), we obtain:

[0042]

[0043] The engine is directly connected to the hydraulic pump, and the power transmission relationship between the two is:

[0044] P e = P p · η ep , η ep ∈ (0, 1] (11)

[0045] wherein η ep is the power transmission efficiency between the engine and the hydraulic pump.

[0046] Assuming η ep = 1, substituting (4), (6) and (10) into (11), we obtain:

[0047]

[0048] By measuring the load pressures p p1 and p p2 of the front and rear pumps within the working time of the experiment, we can obtain the relationship between the load pressure and the output flow of the hydraulic pump before and after the pump.The sum is calculated to obtain the outlet pressure p of the hydraulic pump p .

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] in, is the load pressure of the front pump during working hours (N), i=1,2,3,…,n;

[0056] is the load pressure of the rear pump during working hours (N), i=1,2,3,…,n;

[0057] is the sum of the load pressures of the front pump and the rear pump during the working time (N), i = 1, 2, 3, …, n.

[0058] Find the minimum of formula (16), formula (17) and formula (18) respectively and Fitting load pressure for front pump, rear pump and hydraulic pump.

[0059] Then calculate the fitting required torque of the hydraulic pump for:

[0060]

[0061] Among them, V pMAX is the maximum displacement of the hydraulic pump.

[0062] respectively Find the minimum and maximum values ​​in the equation as the minimum load pressure p of the hydraulic pump pmin and maximum load pressure p pmax . And calculate the minimum required torque T of the hydraulic pump respectively min and the maximum required torque T max for:

[0063]

[0064]

[0065] Respectively in p p1 and pp2 Find the maximum load pressure p of the front and rear pumps p1max and p p2max , calculate the maximum required torque T of the front pump and the rear pump 1max and T 2max .

[0066]

[0067]

[0068] (4) Establishment of comprehensive evaluation model

[0069] Assume that the torque value of the excavator's working point obtained by optimization is T r .

[0070] 1. Engine fuel consumption

[0071] During the operation of the engine, its operating point will change on the speed control curve as the load changes. l When it increases, the engine operating point moves upward, and the torque value T e Increase; when the load pressure p l When it decreases, the engine operating point moves downward and the torque value T e Decline. Figure 6 It can be seen that when the engine speed n e At a certain time, its fuel consumption F e With its torque T e If you want to reduce the fuel consumption of hydraulic excavators, e , which can reduce its torque T e .

[0072] The engine fuel consumption evaluation model is established as follows:

[0073]

[0074] The optimization goal is to make f1(T r ) as small as possible.

[0075] 2. Hydraulic pump efficiency

[0076] Due to equations (3) and (4), the efficiency of the hydraulic pump can be adjusted to p The only variable that can be improved is the displacement ratio β, β∈[0,1] and β is generally not equal to 0. Therefore, if you want to increase the efficiency E of the hydraulic pump p , the displacement ratio β can be increased. According to formula (5), it can be found that by increasing the displacement V p To increase its displacement ratio β, thereby improving the efficiency E of the hydraulic pump p .

[0077] According to formula (12), when the working point is set to T r When the load pressure of the front pump and the rear pump is p p1 and p p2 When the e Trend T r , it is necessary to adjust the displacement V of the hydraulic pump p1 and V p2 When T e Greater than T r When it is necessary to reduce V p1 and V p2 When T e Less than T r When V p1 and V p2 .according to Figure 3 It can be seen that in order to reduce the fuel consumption of the engine, T r The lower the setting, the better, but according to formula (5) reduce V p1 and V p2 This will result in reduced efficiency of the hydraulic pump. r Set too high, according to Figure 3 It can be seen that the fuel consumption of the engine F e will be high, and if p p1 and p p2 When T reaches its maximum value, e Still smaller than T r Then increase V p1 and V p2 Adjust T e to T r In the process, β∈[0,1], when β=1, T e The limit has been reached, if T e Still less than T r , then T cannot be adjusted e to T r . So in order to avoid the above two situations, T r The settings need to have upper and lower limits.

[0078] The efficiency of the hydraulic pump is preferably set above 75%. Figure 5 From the experimental data (in the experimental data, the load pressure of the front pump and the rear pump varies between 0 MPa and 30 MPa), it can be seen that the lower limit of the displacement ratio of the hydraulic pump is β min ∈[0.4,0.6]. According to formula (21), p p1 and p p2 of and p p Both reach the maximum value p pmax , and V p1 and V p2 All reach VMAX When T e is the maximum value T max According to equations (5) and (12), when the displacement ratio of the hydraulic pump is its lower limit β min When the torque value T of the excavator working point is deduced, r The lower limit of is:

[0079]

[0080] According to formula (20) and (21), T min and T max The average value T ave As shown in formula (34).

[0081]

[0082] Among them, T ave =0.5·T min +0.5·T max Close to or even greater than T max β min , so T ave As T r The lower limit of .

[0083] The torque value T of the excavator working point obtained by optimization is r The required torques of the front and rear pumps assigned to the hydraulic pumps are:

[0084]

[0085]

[0086] Among them, T r1 ≤T 1max , T r2 ≤T 2max Right now,

[0087] The torque value T of the excavator working point can be deduced r The upper limit is:

[0088]

[0089] 3. Load fluctuation

[0090] According to formula (18), the minimum is the fitting load pressure of the hydraulic pump, obtained according to formula (19): The cumulative sum of distances required to reach the hydraulic pump's required torque at each moment is minimized, indicating minimal load fluctuation. Load fluctuation represents the total distance the hydraulic pump needs to adjust from the torque calculated by fitting the load pressure at each moment to the torque at the set operating point during actual operation. The greater the sum of these distances, the greater the load fluctuation, the greater the distance the hydraulic pump needs to adjust, and the more difficult it is to adjust the hydraulic pump.

[0091] The load fluctuation evaluation model is established as follows:

[0092]

[0093] The optimization goal is to make f2(T r ) as small as possible.

[0094] 4. Comprehensive evaluation model

[0095] make

[0096] The comprehensive evaluation model is established by combining formulas (24) and (30) as follows:

[0097] f(x1,x2,T r )=x1·f1(T r )+x2·f2(T r ),T rmin ≤T r ≤T rmax (31)

[0098]

[0099] x1+x2=1 (33)

[0100] Among them, x1 and x2 are weight coefficients, representing the proportion of the two evaluation models respectively.

[0101] (5) Optimization of excavator working point

[0102] The optimization goal of the excavator working point is to find the minimum T of formula (32) r .

[0103] According to different emphasis objectives, the weight coefficients of x1 and x2 can be adjusted appropriately according to formula (33). The larger the weight coefficient, the more important the evaluation model is.

[0104] The specific optimization process is shown in the optimization process flow chart ( Figure 6 ) as shown.

[0105] The beneficial effects of the present application: the present application aims at the engine operating point stabilizing method by controlling the displacement of the hydraulic pump, comprehensively considers the engine oil consumption, hydraulic pump efficiency and load fluctuation three factors, respectively according to the engine oil consumption, hydraulic pump efficiency and load fluctuation to establish a comprehensive evaluation model, through setting the weight coefficient to evaluate the importance of engine oil consumption and load fluctuation, and according to the efficiency of the hydraulic pump to determine the upper and lower limit of the operating point torque, and through the optimization of the comprehensive evaluation model to obtain the best torque of the engine operating point. BRIEF DESCRIPTION OF DRAWINGS

[0106] Figure 1 Speed curve diagram of the engine.

[0107] Figure 2 Universal characteristic curve diagram of the engine.

[0108] Figure 3 Fuel consumption and speed relationship diagram of the engine.

[0109] Figure 4 Hydraulic structure diagram of the positive displacement piston variable pump.

[0110] Figure 5 Hydraulic pump efficiency changes with the independent variable diagram.

[0111] Figure 6 Optimization process flow chart.

[0112] Figure 7 Optimization calculation result diagram DETAILED DESCRIPTION

[0113] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments.

[0114] The specific implementation steps of the method of the present application are as follows:

[0115] 1. Determine the gear of the engine, that is, determine the speed curve of the engine in the current working process, and determine the current speed n e The rated speed of the engine is 1700r / min. The relationship between the fuel consumption rate η e , output power P e and its speed n e , torque T e of the engine in the universal characteristic curve of the engine is polynomial fitted, and according to formula (1), the fuel consumption F e of the engine and its speed n e , torque T eThe speed n is determined according to the external characteristic curve of the engine. e The maximum torque value T that the engine can provide MAX .

[0116] 2. Test the hydraulic pump at different speeds n p , the efficiency under different pressure difference Δp and different displacement ratio β. The hydraulic pump efficiency E can be obtained p Its speed n p , pressure difference Δp, displacement ratio β relationship diagram of hydraulic pump efficiency model. p When the pressure difference Δp is constant, it is found that the hydraulic pump efficiency E p It is positively correlated with the displacement ratio β, that is, with the displacement V p Positive correlation.

[0117] 3. Collect the load pressure of the excavator when it is working, that is, the outlet pressure p of the front pump and the rear pump p1 and p p2 , calculate the outlet pressure p of the hydraulic pump according to formula (15) p According to equations (16), (17) and (18), the fitting load pressure of the front pump and the rear pump is obtained. and the fitted load pressure of the hydraulic pump Wherein formula (16), formula (17) and formula (18) are:

[0118]

[0119]

[0120]

[0121] Table 1 Pressure value calculation results

[0122]

[0123] According to formula (19), the fitting required torque of the hydraulic pump is obtained According to equations (20) and (21), the minimum required torque T of the hydraulic pump is obtained: min and the maximum required torque T max According to equations (22) and (23), the maximum required torque T of the front pump and the rear pump of the hydraulic pump are calculated respectively. 1max 、T 2max The maximum displacement of the hydraulic pump is V MAX The maximum output torque of the engine is 125ml / r at the rated speed of 1700r / min. MAX It is 950N.m.

[0124] Table 2 Torque value calculation results

[0125]

[0126] According to formula (33), three cases of x1 = 0.6, x2 = 0.4, x1 = 0.5, x2 = 0.5, and x1 = 0.4, x2 = 0.6 are selected, representing the emphasis on engine fuel consumption and load fluctuation, respectively. The comprehensive evaluation model of the excavator working point is established based on formulas (27), (28), and (32):

[0127]

[0128]

[0129]

[0130] Simplifying equations (37), (38) and (39), we obtain:

[0131]

[0132]

[0133]

[0134] According to equations (40) to (42), the curves of the calculation results of the comprehensive evaluation model as the engine operating point torque value changes in different working stages under the three conditions of x1 = 0.6, x2 = 0.4, x1 = 0.5, x2 = 0.5 and x1 = 0.4, x2 = 0.6 are plotted as follows: Figure 7 shown.

[0135] according to Figure 7 The engine operating point torque can be obtained as 678 (N·m).

Claims

1. A method for optimizing the working point of an excavator based on a comprehensive evaluation model, characterized in that: The specific steps of this method are as follows: (1) Establishment of engine fuel consumption model According to the engine speed control curve, the engine is allowed to work in different gears, and different gears correspond to the set speed. Different; Due to the effect of the engine speed governor, the engine maintains its speed during operation During the operation of the engine, its operating point will change on the speed control curve as the load changes; when the load pressure When it increases, the engine operating point moves upward and the torque value Increase; when load pressure When it decreases, the engine operating point moves downward and the torque value decline; According to the universal characteristic curve of the engine, the fuel consumption rate of the engine is , output power Its speed and its torque There are external characteristic curves, equal fuel consumption rate curves and equal power curves on the universal characteristic curve diagram. The external characteristic curve represents the maximum torque value provided by the engine at different speeds. , the fuel consumption rate at a point on the equal fuel consumption rate curve The same, the power of the point on the equal power curve Same; fuel consumption and output power , fuel consumption rate The relationship is as follows: (1) ； Perform polynomial fitting on the engine's universal characteristic curve to obtain the engine's fuel consumption and its speed , torque According to the engine speed curve, when the excavator is working, the speed remains unchanged when the gear is determined; a speed is selected according to the working gear as the speed of the excavator when working. When the speed After determination, the fuel consumption of the engine is obtained With its torque The functional relationship is: (2) ； According to the functional relationship, the relationship diagram between the fuel consumption and the speed of the engine is established. It is found that when the engine speed At a certain time, its fuel consumption With its torque Positive correlation; Therefore, if you want to reduce the fuel consumption of hydraulic excavators , by reducing its torque accomplish; (2) Establishment of hydraulic pump efficiency model From the hydraulic structure diagram of the positive flow plunger variable pump, it is found that it consists of two sub-pumps, namely the front pump 1 and the rear pump 2, which provide hydraulic power for different actuators of the excavator; the efficiency of the hydraulic pump Its speed , pressure difference , displacement ratio Related, respectively test the hydraulic pump at different speeds , different pressure differences , different displacement ratios Efficiency under; get the hydraulic pump efficiency Its speed , pressure difference , displacement ratio where the pressure difference is determined by the load pressure The hydraulic pump is directly driven by the engine, so the two have the same speed; we get: (3) ； (4) ； Therefore, adjust the efficiency of the hydraulic pump The only variable that is improved is its displacement ratio , and Generally not equal to 0; observe the efficiency of the hydraulic pump Its speed , pressure difference , displacement ratio The relationship diagram found and Positive correlation; displacement of hydraulic pump Its displacement ratio The relationship is: (5) ； in, is the maximum displacement of the hydraulic pump; Therefore, if you want to increase the efficiency of the hydraulic pump , by increasing its displacement ratio , that is, increase its displacement To achieve; (3) Conversion and fitting of load pressure Engine power for: (6) ； Where, The unit is kilowatt; The unit is Newton per meter; The unit is revolutions per minute; The outlet pressure of the hydraulic pump is its load pressure. Since the hydraulic pump consists of two parts, the front pump and the rear pump, the power of the hydraulic pump is the sum of the power of the two sub-pumps, that is: (7) ； Where, The unit is kilowatt; is the outlet pressure of the hydraulic pump front pump; is the outlet pressure of the hydraulic pump; is the output flow of the hydraulic pump front pump; is the output flow of the hydraulic pump after the pump; The relationship between the flow rate and displacement of the front and rear hydraulic pumps is: (8) ； (9) ； Where, is the displacement of the hydraulic front pump; is the displacement of the hydraulic pump rear pump; is the speed of the hydraulic pump drive shaft; Substituting equations (8) and (9) into (7), we obtain: (10) ； The engine is directly connected to the hydraulic pump, and the power transmission relationship between the two is: ， (11) ； in is the power transmission efficiency between the engine and the hydraulic pump; assumed Substituting (4), (6) and (10) into (11), we obtain: (12) ； The load pressure of the front pump and the rear pump during the working time is measured by the experiment and The sum is calculated to obtain the outlet pressure of the hydraulic pump ; (13) ； (14) ； (15) ； (16) ； (17) ； (18) ； in, is the load pressure of the front pump during working hours, ; is the load pressure of the rear pump during working hours, ; is the sum of the load pressures of the front pump and the rear pump during working hours, ; Find the minimum of formula (16), formula (17) and formula (18) respectively 、 and Fitting load pressure for front pump, rear pump and hydraulic pump; Then calculate the fitting required torque of the hydraulic pump for: (19) ； in, is the maximum displacement of the hydraulic pump; respectively Find the minimum and maximum values ​​as the minimum load pressure of the hydraulic pump and maximum load pressure ; and calculate the minimum required torque of the hydraulic pump respectively and maximum required torque for: (20) ； (21) ； respectively and Find the maximum load pressure of the front and rear pumps and , calculate the maximum required torque of the front pump and the rear pump and ; (22) ； (23) ； (4) Establishment of comprehensive evaluation model Assume that the torque value of the excavator's working point obtained by optimization is ; 1. Engine fuel consumption During the operation of the engine, its operating point will change on the speed control curve as the load changes; when the load pressure When it increases, the engine operating point moves upward and the torque value Increase; when load pressure When it decreases, the engine operating point moves downward and the torque value Decrease; when the engine speed At a certain time, its fuel consumption With its torque Positive correlation; if you want to reduce the fuel consumption of hydraulic excavators , by reducing its torque accomplish; The engine fuel consumption evaluation model is established as follows: (24) ； The optimization goal is to As small as possible; 2. Hydraulic pump efficiency Due to equations (3) and (4), the efficiency of the hydraulic pump is adjusted to The only variable that is improved is its displacement ratio , and Generally not equal to 0; so if you want to increase the efficiency of the hydraulic pump , by increasing its displacement ratio According to formula (5), by increasing its displacement To increase its displacement ratio , thereby improving the efficiency of the hydraulic pump ; According to formula (12), when the torque value of the setting working point is In actual working process, the load pressure of front pump and rear pump and When changes occur, in order to tend , it is necessary to adjust the displacement of the hydraulic pump and ;when Greater than When you need to reduce and ;when Less than When and In order to reduce engine fuel consumption, The lower the setting, the better, but according to formula (5) and Will cause the efficiency of the hydraulic pump to decrease; if If the setting is too high, the engine fuel consumption will be will be high, and if and Reaching a maximum value, Still less than Then increase and adjust arrive In the process, ,when hour, The limit has been reached, if Still less than , then it will not be possible to adjust arrive ; So in order to avoid the above two situations, The setting needs to have upper and lower limits; The efficiency of the hydraulic pump is set at above 75%; according to the efficiency of the hydraulic pump Its speed , pressure difference , displacement ratio The relationship diagram and experimental data show that the lower limit of the hydraulic pump displacement ratio is According to formula (21), when and of All reached maximum value ,and and All reached When is the maximum value According to formulas (5) and (12), when the displacement ratio of the hydraulic pump is its lower limit When the torque value of the excavator working point is deduced The lower limit of is: (25) ； According to formulas (20) and (21), we can get and Average value As shown in formula (34); (26) ； in, Close to or even greater than , so As The lower limit of The torque value of the excavator working point obtained by optimization is The required torques of the front and rear pumps assigned to the hydraulic pumps are: (27) ； (28) ； in, , Right now, , Derived torque value of excavator working point The upper limit is: (29) ； 3. Load fluctuation According to formula (18), the minimum is the fitting load pressure of the hydraulic pump, obtained according to formula (19): ,Then The cumulative sum of distances to the required torque value of the hydraulic pump at each moment is minimized, that is, the load fluctuation is minimized. The load fluctuation represents the total distance that the hydraulic pump needs to adjust from the torque obtained by fitting the load pressure at each moment to the torque of the set working point in actual operation. The larger the sum of distances, the greater the load fluctuation, the greater the distance the hydraulic pump needs to adjust, and the more difficult the hydraulic pump adjustment is. The load fluctuation evaluation model is established as follows: (30) ； The optimization goal is to As small as possible; 4. Comprehensive evaluation model make , The comprehensive evaluation model is established by combining formulas (24) and (30) as follows: , (31) ； ， (32) ； (33) ； in , is the weight coefficient, representing the proportion of the two evaluation models; (5) Optimization of excavator working point The optimization goal of the excavator working point is to find the minimum formula (32) ; According to different emphasis goals, adjust the formula (33) accordingly. , The larger the weight coefficient, the more important the evaluation model is.

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