Control method for improving transient responsiveness in engine constant rotating speed control mode

Abstract

The invention relates to a control method for improving transient responsiveness in a constant rotating speed control mode of an engine. The control method comprises the following steps that the rotating speed change rate and the rotating speed value of the engine are determined; judging whether the engine state meets a state switching condition or not; when the state of the engine is switched from the steady state to the transient state, the dynamic load offset of the engine relative to the steady state in the transient state is calculated, and the target torque in the transient state is determined in combination with engine data of a control period before the engine is switched from the steady state to the transient state; when the state of the engine is switched from the transient state to the steady state, parameters of a traditional rotating speed control PID algorithm are initialized according to different operation data when the steady state is switched to the transient state and when the transient state is switched to the steady state, and the target torque in the steady state is determined through the PID algorithm; and according to the target torque, other control parameters are finely adjusted to realize control. Compared with the prior art, the output torque of the engine can be quickly changed to stabilize the rotating speed of the engine when the load of the engine is instantaneously and greatly changed.

Description

Technical Field

[0001] The present invention relates to the technical field of engine speed control, and in particular to a control method for improving transient response under a constant engine speed control mode. Background Art

[0002] As the power output device of a vehicle or construction machinery, the engine is the "heart" of the entire system, and the operating speed of the engine is the "pulse" of the heart. For different engines, there is an ideal working speed range. Controlling the engine to operate stably within this range plays a crucial role in energy conservation, emission reduction, and extending the machine life. Especially in the power generation field, to ensure a stable power generation frequency, it is necessary to ensure that the generator set operates at a constant speed.

[0003] At present, the commonly used constant speed control method at home and abroad is PID regulation, that is, the proportional (P), integral (I), and derivative (D) control algorithms. Using P control can quickly overcome the influence of disturbances. Increasing the coefficient of P can accelerate the responsiveness of the system, but too large a coefficient will reduce the stability of the system and even cause large fluctuations. The integral I can eliminate the residual error on the basis of the proportion, but it has strong hysteresis. It can have a good control effect in steady-state situations with little load change, but for power generation situations with load changes of up to 50% at every turn, it is easy for the speed to cross the speed set value during the recovery process and fail to "brake" in time, deviating in the opposite direction from the set value. The derivative D has predictability and can predict the trend of deviation changes. When the actual engine speed is about to return to the set value, it brakes in advance to improve the dynamic performance. However, the derivative has an amplifying effect on noise interference. Deviations in the crankshaft machining of the engine and small disturbances in the sensor signals will all cause speed fluctuations in the engine under steady state. The sum of the three parts of PID is the final target torque percentage, which is interpreted as the ratio of the torque output by the engine at the current speed to the maximum torque that the engine can output at the current speed. 0 means no output, and 100 means maximum output. In summary, the existing PID control method is difficult to meet the transient response of the engine. Summary of the Invention

[0004] The purpose of the present invention is to provide a control method for improving transient response under a constant engine speed control mode, which can quickly change the output torque of the engine and stabilize the engine speed when the engine load changes significantly instantaneously, thereby improving the transient response of the engine.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A control method for improving transient response under the constant engine speed control mode. During the operation of the engine, the engine control module periodically implements the control method, and the period of each implementation of the control method is the fuel injection period of the engine. The control method includes the following steps:

[0007] Step 1: When the engine enters the constant speed operation mode, sample the engine crankshaft signal period to determine the engine speed change rate and speed value;

[0008] Step 2: Judge the engine state and whether the state switching condition is met according to the engine speed change rate and speed value. The engine state is one of steady state or transient state;

[0009] Step 3: When the engine state switches from steady state to transient state, calculate the dynamic load offset of the engine in transient state relative to the steady state according to the engine speed change rate, and determine the target torque in transient state according to the load offset and the engine data in the previous control period when the engine switches from steady state to transient state;

[0010] Step 4: When the engine state switches from transient state to steady state, initialize the integral term of the traditional speed control PID algorithm according to the differences in engine operation data when switching from steady state to transient state and from transient state to steady state, calculate the target torque percentage using the traditional speed control PID algorithm, and look up the table to obtain the target torque in steady state;

[0011] Step 5: According to the target torque corresponding to the engine state, and finely adjust other control parameters to set the engine data, and control the engine output torque to reach the target value.

[0012] As a preferred technical solution, Step 1 includes the following steps:

[0013] Step 1.1: Eliminate system errors, count the ratio of the angle of each tooth of the crankshaft to 360° of one revolution of the crankshaft, calculate the ratio of the interval time of each crankshaft signal in one revolution to the total sum of all crankshaft interval times according to the crankshaft tooth number and its corresponding crankshaft signal interval time recorded during the engine factory test run at a fixed reverse drag speed, and store the ratio in the memory of the engine control module, denoted as the array r[N] = {r 1 , r 2 , r 3 , …, r n}, where n represents the crankshaft tooth number and N represents the total number of teeth of the crankshaft signal disk;

[0014] Step 1.2: When the engine is running, every time an edge signal of a crankshaft tooth is detected, calculate the interval time with the adjacent crankshaft signal once. According to the tooth number of the crankshaft, select different ratios in r[N] to calculate the instantaneous speed of the engine. The instantaneous speed values total N elements, denoted as n[N].

[0015] Step 1.3: When the engine is running, every time an edge signal of a crankshaft tooth is detected, calculate the interval time with the signal of its own tooth number in the previous revolution once. The interval times total N elements, denoted as T[N].

[0016] Step 1.4: When the engine is running, every time an edge signal of a crankshaft tooth is detected, take the average value of the speeds calculated based on the nearest 3 teeth as the average speed. The average speed values total N elements, denoted as ;

[0017] Step 1.5: When the engine is running, every time an edge signal of a crankshaft tooth is detected, before calculating the average speed, copy the historical average speed value calculated at the same position in the previous revolution of the engine to the memory of the engine control module. The historical speed values total N elements, denoted as ;

[0018] Step 1.6: Calculate the speed deviation between the instantaneous speed n of the current crankshaft tooth and the constant speed value set for the engine.

[0019] Step 1.7: Calculate the difference between the average speed of the current crankshaft tooth and the historical average speed , and divide it by the interval time T between the current moment and the signal of its own tooth number in the previous revolution to obtain the speed change rate.

[0020] As a preferred technical solution, step 2 is specifically: According to the state detected in the previous detection period of the engine control module, determine whether the speed deviation and the speed change rate reach the state switching condition. If the condition is met, switch the engine state; if the condition is not met, continue to use the previous detection state.

[0021] As a preferred technical solution, the transient state includes a sudden increase mode and a sudden decrease mode.

[0022] As a preferred technical solution, the state switching conditions include:

[0023] 1) Conditions for switching from the steady state to the transient state - sudden increase mode:

[0024] The speed deviation range is (-∞, N 1 ), and the numerical unit is revolutions per minute;

[0025] The speed change rate range is (-∞, dN 1), with the numerical unit being revolutions per minute per second;

[0026] 2) Conditions for transient - sudden increase mode to switch to steady state:

[0027] The speed deviation range is [N 1 , 0], with the numerical unit being revolutions per minute;

[0028] The speed change rate range is (dN′ 1 , +∞), with the numerical unit being revolutions per minute per second;

[0029] 3) Conditions for steady state to switch to transient - sudden decrease mode:

[0030] The speed deviation range is (N 2 , +∞), with the numerical unit being revolutions per minute;

[0031] The speed change rate range is (dN 2 , +∞), with the numerical unit being revolutions per minute per second;

[0032] 4) Conditions for transient - sudden decrease mode to switch to steady state:

[0033] The speed deviation range is [0, N 2 , with the numerical unit being revolutions per minute;

[0034] The speed change rate range is (-∞, dN′ 2 ), with the numerical unit being revolutions per minute per second;

[0035] Each threshold value N 1 , dN 1 , dN′ 1 , N 2 , dN 2 , dN′ 2 is preset in the engine control module, and its specific value is obtained from engine bench tests.

[0036] As a preferred technical solution, step 3 includes the following steps:

[0037] Step 3.1: When the engine state switches from steady state to transient state, according to the speed change rate, look up the dynamic load offset in the dynamic load offset lookup table, and the dynamic load offset lookup table is preset in the engine control module, and the corresponding relationship between the dynamic load offset and the engine speed change rate is set in the dynamic load offset lookup table;

[0038] Step 3.2: Record the engine data of the previous control cycle when the engine state switches from steady state to transient state;

[0039] Step 3.3: Add the dynamic load offset in Step 3.1 to the engine load before the switching state recorded in Step 3.2 to obtain the instantaneous total load value, and look up the target torque of the engine at the transient state in the preset target torque query table. The target torque query table is pre-set in the engine control module, and the corresponding relationship between the target torque and the real-time engine speed and load is set in the target torque query table.

[0040] As a preferred technical solution, the said Step 4 includes the following steps:

[0041] Step 4.1: When the engine state switches from transient to steady state, record the engine data of the previous control cycle before the engine state switches from transient to steady state.

[0042] Step 4.2: According to the differences in the calculation input items of the engine traditional control PID algorithm recorded at the two time points of steady state switching to transient state and transient state switching to steady state, re-initialize the integral term of the target torque percentage, so that the target torque calculated by the traditional control PID algorithm is equal to the target torque calculated in Step 3 in the previous control cycle before the transient state switches to the steady state, and obtain the target torque in the steady state.

[0043] As a preferred technical solution, the said engine data includes the load of the engine and the calculation input items of the engine traditional control method. The said calculation input items include the speed difference and the integral term of the target torque percentage.

[0044] As a preferred technical solution, the said other control parameters include ignition advance angle, excess air coefficient and injection pressure.

[0045] As a preferred technical solution, the said fine-tuning of other control parameters to set the engine data specifically includes:

[0046] Fine-tuning the ignition advance angle: According to the real-time engine speed difference and fuel injection volume, look up the ignition advance angle correction value of the engine in the preset ignition advance angle correction query table. The ignition advance angle correction query table is pre-set in the engine control module, and the corresponding relationship between the ignition advance angle correction value and the real-time engine speed difference and injection volume is set in the ignition advance angle correction query table.

[0047] Fine-tuning the excess air coefficient: According to the real-time engine speed difference and fuel injection volume, look up the excess air coefficient correction value of the engine in the preset excess air coefficient correction query table. The excess air coefficient correction query table is pre-set in the engine control module, and the corresponding relationship between the excess air coefficient correction value and the real-time engine speed difference and injection volume is set in the excess air coefficient correction query table.

[0048] Fine-tuning injection pressure: Based on the real-time engine speed difference and fuel injection volume, look up the target rail pressure correction value of the engine in the preset target rail pressure correction lookup table of the fuel high-pressure common rail pipe; the target rail pressure correction lookup table is pre-set in the engine control module, and the corresponding relationship between the target rail pressure correction value and the real-time engine speed difference and injection volume is set in the target rail pressure correction lookup table.

[0049] The control method for improving the transient response under the constant engine speed working mode of the present invention optimizes the calculation of the instantaneous speed and the speed change rate on the basis of the traditional control method, and further divides the transient and steady-state working conditions to calculate the target torque through two methods respectively. The algorithm in the transient state is to estimate the dynamic load offset of the engine through the speed change rate, and then further calculate the target torque of the engine according to the dynamic load offset of the engine; the algorithm in the steady state follows the traditional speed control algorithm, but can smoothly switch the target torque output when the state changes.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] (1) The present invention can more reasonably debug the optimal PID parameters in the steady-state working condition, give play to the advantages of the traditional speed control algorithm, and make the engine run more stably without external load disturbance;

[0052] (2) The present invention avoids the disadvantageous interval of the traditional speed control algorithm, calculates the dynamic disturbance according to the speed change rate, and quickly responds to the torque output before the load change has a serious impact on the engine speed, so that the engine can withstand stronger instantaneous load changes;

[0053] (3) The present invention divides the engine into two states, and various algorithms for fine-tuning the combustion efficiency can be added on this basis. In the transient working condition with a very short working time, sacrificing part of the emissions or fuel economy to achieve short-term over-control, further improving the anti-load impact ability of the engine. Description of the Drawings

[0054] Figure 1 is the flowchart of the method of the present invention;

[0055] Figure 2 is the schematic diagram of the calculation process of the engine speed value and the speed change amount of the present invention;

[0056] Figure 3 is the schematic diagram of the method for determining the target torque according to different engine states of the present invention. Detailed Embodiments

[0057] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives the detailed implementation manner and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0058] As Figure 1 shown, this embodiment provides a control method for improving the transient response under the constant engine speed control mode. During the operation of the engine, the ECU periodically implements the control method, and the period of each implementation of the control method is the fuel injection period of the engine. The control method includes the following steps:

[0059] Step 1: When the engine enters the constant speed working mode, sample the engine crankshaft signal period to determine the engine speed change rate and speed value with fast response and low noise.

[0060] Step 2: Judge the engine state and whether the state switching condition is met according to the engine speed change rate and speed value. The engine state is one of steady state or transient state.

[0061] Step 3: When the engine state switches from the steady state to the transient state, calculate the dynamic load offset of the engine in the transient state relative to the steady state according to the engine speed change rate, and determine the target torque in the transient state according to the load offset and the engine data in the previous control cycle when the engine switches from the steady state to the transient state.

[0062] Step 4: When the engine state switches from the transient state to the steady state, initialize the integral term of the traditional speed control PID algorithm according to the differences in the engine operation data when switching from the steady state to the transient state and from the transient state to the steady state, calculate the target torque percentage using the traditional speed control PID algorithm, and look up the table to obtain the target torque in the steady state.

[0063] Step 5: Set the engine data according to the target torque corresponding to the engine state and fine-tune other control parameters to control the engine output torque to reach the target value.

[0064] Currently, for the calculation of the engine speed change rate, the method of timing the collection of the starting point and the ending point of the speed and dividing by the collection period is adopted, which is easily affected by the crankshaft processing error and the uneven speed during the compression and working strokes of the engine. If the sampling period is too long, the accuracy is poor; if the sampling period is too short, the noise is large. Finally, it acts on the differential (D) of the traditional speed control method, amplifying the error. In this embodiment, the following method is adopted to determine the speed and speed change rate in Step 1:

[0065] Step 1.1: Calculate the ratio of the angle of each tooth of the crankshaft to 360° of one revolution of the crankshaft. Taking the engine of model YC12VTD as an example, the crankshaft signal disk of this engine is processed with 60 teeth evenly distributed, and the positions of the 59th and 60th teeth are ground or unprocessed, serving as the characteristic teeth of the crankshaft. As Figure 2 shown, there are a total of 58 (60 - 2) teeth. Theoretically, one tooth is 6°, and the last crankshaft tooth is a missing tooth, accounting for 18°. According to the crankshaft signal interval time of each tooth among the 1st - 58th teeth recorded when the engine is tested at a fixed reverse - dragging speed during factory production, calculate the ratio of each crankshaft signal interval time in one revolution to the sum of the 58 interval times, obtaining a total of 58 ratios. Store the said ratios in the memory of the ECU, denoted as the array r

[58] ;

[0066] Step 1.2: When the engine is running, every time an edge signal of a crankshaft tooth is detected, calculate the interval time with the adjacent crankshaft signal. According to the tooth number of the crankshaft, select different ratios in r

[58] to calculate the 6° instantaneous speed of the engine. The 6° instantaneous speed values total 58 elements, denoted as n

[58] ;

[0067] Step 1.3: When the engine is running, every time an edge signal of a crankshaft tooth is detected, calculate the interval time with the signal of the same tooth number in the previous revolution. The interval times total 58 elements, denoted as T

[58] ;

[0068] Step 1.4: When the engine is running, every time an edge signal of a crankshaft tooth is detected, take the average value of the speeds calculated based on the speeds of the nearest 3 teeth as the 18° average speed, excluding the missing tooth of the crankshaft. The 18° average speed at the missing - tooth position is equivalent to its instantaneous speed. The 18° average speed values total 58 elements, denoted by ;

[0069] Step 1.5: When the engine is running, every time an edge signal of a crankshaft tooth is detected, before calculating the 18° average speed, copy the historical 18° average speed value calculated at the same position in the previous revolution of the engine to the memory of the engine control module. The historical 18° average speed values total 58 elements, denoted by ;

[0070] Step 1.6: Calculate the speed deviation between the 6° instantaneous speed n of the current crankshaft tooth and the constant - speed value set for the engine;

[0071] Step 1.7: Calculate the difference between the 18° average speed of the current crankshaft tooth and the historical 18° average speed , and divide it by the interval time T between the current moment and the signal of the same tooth number in the previous revolution to obtain the speed change rate.

[0072] As Figure 2, this embodiment is based on the crankshaft signal of the engine and is triggered by the GPIO interrupt at the bottom layer of the controller single-chip microcomputer. Whenever the crankshaft teeth cut the magnetic induction lines of the crankshaft sensor to generate current, causing the input voltage in the controller to flip from top to bottom, the algorithm is executed once. The period of this embodiment is the same as the time interval between two adjacent teeth of the crankshaft. That is to say, the number of teeth in one revolution of the engine crankshaft signal disk has a great influence on the accuracy of this embodiment. In this embodiment, the implementation object of the control algorithm for improving the transient response of the engine is a crankshaft signal disk with 60 - 2 teeth. In other embodiments, the number of elements in a specific array can also be modified according to the present invention. For an engine with a relatively small number of teeth on the crankshaft signal disk, such as the number of teeth less than or equal to the number of engine cylinders, this embodiment is not applicable.

[0073] Figure 2 The parameter explanations are as follows:

[0074] i - The crankshaft tooth number directly opposite the current crankshaft sensor;

[0075] t - The interval time between two adjacent tooth signals, in us;

[0076] T - The time for the current engine to make one revolution, in us;

[0077] r i - The ratio of the interval between two adjacent teeth of the current crankshaft tooth number stored in the controller to one revolution of the crankshaft;

[0078] n i - The real-time engine speed calculated based on the interval between two adjacent teeth of the current crankshaft tooth number, in rpm;

[0079] - The average value of the real-time engine speeds calculated in the last 3 times, in rpm;

[0080] - The average value calculated at the i-th tooth of the previous revolution and stored in the controller, in rpm;

[0081] dn - The engine speed change rate, in rpm / s.

[0082] See Figure 2 , it is pre-set that the first tooth after the crankshaft tooth is missing read by the engine controller is tooth No. 1. That is, when the controller first detects that the ratio of the interval time t between two adjacent tooth numbers to the previous time is approximately 3:1, it records the current tooth number as 1. Each time this algorithm is entered subsequently, the tooth number is incremented by 1 on this basis. When it accumulates to 59, the tooth number is reset to 1.

[0083] In the memory of the engine controller, a predefined area is used to store the ratio of 58 teeth to a full circle. When the engine is tested at the factory, the calculated ratio will be written into the memory in the order of the tooth number if the specific speed condition is met. After the controller detects that 58 values ​​have been stored, it will no longer write. This part of the memory data will not be lost when the engine controller is powered off.

[0084] In step 2, based on the state detected by the engine control module in the previous detection cycle, it is determined whether the speed deviation and the speed change rate meet the state switching conditions. If the conditions are met, the engine state is switched. If the conditions are not met, the previous detection state continues to be used.

[0085] See also Figure 3 In this embodiment, the transient state includes the sudden increase mode and the sudden decrease mode. The main difference is that the condition thresholds for the steady state to switch to these two sub-states are different. In addition, the algorithms for calculating the dynamic load according to the speed change rate and the target torque by table lookup are the same for these two sub-states. The corresponding state switching conditions include:

[0086] 1) Conditions for steady-state switching transient (sudden increase mode):

[0087] The speed deviation range is (-∞, N 1 ), the value unit is revolutions per minute;

[0088] The speed change rate range is (-∞, dN 1 ), the value unit is revolutions per minute per second;

[0089] 2) Conditions for transient (sudden increase mode) switching to steady state:

[0090] The speed deviation range is [N 1 , 0], the value unit is revolutions per minute;

[0091] The speed change rate range is (dN′ 1 , +∞) The value unit is revolutions per minute per second;

[0092] 3) Conditions for steady-state switching transient (sudden reduction mode):

[0093] The speed deviation range is (N 2 , +∞), the value unit is revolutions per minute;

[0094] The speed change rate range is (dN 2 , +∞), the value unit is revolutions per minute per second;

[0095] 4) Conditions for switching from transient state (sudden reduction mode) to steady state:

[0096] The speed deviation range is [0, N 2 ], the value unit is revolutions per minute;

[0097] The range of the rotational speed change rate is (-∞, dN′ 2 ), and the numerical unit is revolutions per minute per second;

[0098] Each threshold value N 1 , dN 1 , dN′ 1 , N 2 , dN 2 , dN′ 2 is preset in the ECU, and its specific value is obtained from the engine bench test.

[0099] Specifically, step 3 includes the following steps:

[0100] Step 3.1: When the engine state switches from steady state to transient state, according to the rotational speed change rate, look up the dynamic load offset in the dynamic load offset lookup table. The dynamic load offset lookup table is preset in the ECU, and the corresponding relationship between the dynamic load offset and the engine rotational speed change rate is set in the dynamic load offset lookup table;

[0101] In one embodiment, the dynamic load offset lookup table is shown in Table 1, and its header is the engine rotational speed change rate. After Figure 2 calculating the rotational speed change rate, the dynamic load offset can be looked up in the dynamic load offset lookup table. However, in actual lookup operations, the engine rotational speed change rate is unlikely to be exactly the header value. Therefore, during the lookup process, linear interpolation is used for the lookup operation.

[0102] The specific data in all the shown lookup tables need to be determined according to the engine model. For different models of engines, their moments of inertia are different, and the rotational speed change rates caused by the same load change are also different. Therefore, through engine bench tests, the specific values need to be calibrated. The dynamic load offset lookup table shown in Table 1 is formulated according to the YC12VTD engine.

[0103] Table 1 Dynamic load offset lookup table set for the YC12VTD engine

[0104] Rate of change of rotational speed -700 -600 -500 -400 -300 -250 -200 -150 -100 0 Load 40 32 28 23 20 17 14 9 5 0

[0105] Step 3.2: Record the engine data in the previous control cycle when the engine state switches from steady state to transient state; in this embodiment, the engine data includes the engine load and the calculation input items of the engine traditional control method. The calculation input items include the rotational speed difference and the integral item of the target torque percentage;

[0106] Step 3.3: Add the dynamic load offset in Step 3.1 to the engine load before the switching state recorded in Step 3.2 to obtain the instantaneous total load value, and look up the target torque of the engine at the transient state in a preset target torque query table. The target torque query table is pre-set in the ECU, and the corresponding relationship between the target torque and the real-time engine speed and load is set in the target torque query table.

[0107] Among them, the load of the engine is usually expressed as a percentage, which is interpreted as the ratio of the torque required by the driven machinery for the engine to output at the current speed to the maximum torque that the engine can output at the current speed. 0 means no load, and 100 means full load.

[0108] Specifically, Step 4 includes the following steps:

[0109] Step 4.1: When the engine state switches from transient to steady state, record the engine data in the previous control cycle before the engine state switches from transient to steady state.

[0110] Step 4.2: According to the differences in the calculation input items of the engine traditional control PID algorithm recorded at the two time points of steady state switching to transient state and transient state switching to steady state, re-initialize the integral term of the target torque percentage so that the target torque calculated by the traditional control PID algorithm is equal to the target torque calculated in Step 3 in the previous control cycle before the transient state switches to the steady state, and obtain the target torque in the steady state.

[0111] Figure 3 Each state includes 3 types of calculation behaviors:

[0112] entry: Entering a state is automatically triggered and only executed once;

[0113] do: Continuously execute when the state is active until the state ends;

[0114] exit: Exiting a state is automatically triggered and only executed once.

[0115] Although the dynamic load offset value is calculated for each crankshaft tooth, its accumulation period should be equal to the engine fuel injection period, that is, after the first calculation, the next accumulation can only be performed until the end of the injection or ignition of the nearest cylinder in the subsequent period. Otherwise, the total offset value calculated in the controller will overwrite the previous value. Therefore, although the update period of the rotational speed change rate in this method is the time when the engine rotates one crankshaft tooth, the final actual period acting on the engine actuator is the interval time between the work of two adjacent cylinders, that is, the engine fuel injection period.

[0116] In Step 5, when the engine is in the transient state, the combustion efficiency of the engine is changed by finely tuning other control parameters to further improve the responsiveness.

[0117] Currently, all engines adopt electronic control technology, and the injection quantity and injection timing can be changed by the values preset in the engine control module (abbreviated as ECU). The output torque of the engine is mainly achieved by controlling the fuel injection quantity, supplemented by changing the environment of the combustion chamber to change the combustion efficiency, and finally controlling the output torque of the engine. Increasing the engine fuel injection quantity can increase the output torque of the engine; increasing the ignition advance angle of the engine within a certain range can increase the in-cylinder explosion pressure and achieve a torque output exceeding 100%; increasing the injection pressure of the engine within a certain range, the strong entrainment makes the fuel and air mix more evenly and the combustion more complete, which can also further increase the torque; at steady state, to ensure the economy of the engine, the excess air coefficient is generally set between 1.05 and 1.15, and at transient state, the engine torque output can be increased by appropriately enriching. Therefore, in this embodiment, the other control parameters set include the ignition advance angle, the excess air coefficient, and the injection pressure.

[0118] The specific fine-tuning method is as follows:

[0119] 1. Fine-tune the ignition advance angle: According to the real-time engine speed difference and fuel injection quantity, look up the ignition advance angle correction value of the engine in the preset ignition advance angle correction query table; the ignition advance angle correction query table is preset in the engine control module, and the corresponding relationship between the ignition advance angle correction value and the real-time engine speed difference and injection quantity is set in the ignition advance angle correction query table.

[0120] For a spark-ignition engine, the ignition advance angle represents the angle that the crankshaft rotates during the period from the spark plug ignition moment to the piston reaching the top dead center of engine compression; for a compression-ignition engine, the ignition advance angle represents the angle that the crankshaft rotates during the period from the fuel nozzle injection moment to the piston reaching the top dead center of engine compression.

[0121] Table 2 shows the ignition advance angle correction query table in an embodiment. Among them, the meaning of similar correction values is to drive the actual engine speed closer to the target speed value. Therefore, when the speed difference > 0, that is, the actual speed is higher than the target speed, the calibrated correction value should be able to reduce the engine power when accumulated on the basis of the normal value; when the speed difference < 0, that is, the actual speed is lower than the target speed, the calibrated correction value should be able to increase the engine power when accumulated on the basis of the normal value.

[0122] Table 2 Ignition advance angle query table set for YC12VTD type engine

[0123]

[0124] 2. Fine-tune the excess air coefficient: Based on the real-time engine speed difference and fuel injection volume, look up the excess air coefficient correction value of the engine in the pre-set excess air coefficient correction query table; the excess air coefficient correction query table is pre-set in the engine control module, and the corresponding relationship between the excess air coefficient correction value, the real-time engine speed difference and the injection volume is set in the excess air coefficient correction query table.

[0125] 3. Fine-tune the injection pressure: Based on the real-time engine speed difference and fuel injection volume, look up the target rail pressure correction value of the engine in the pre-set target rail pressure correction query table for the fuel high-pressure common rail; the target rail pressure correction query table is pre-set in the engine control module, and the corresponding relationship between the target rail pressure correction value, the real-time engine speed difference and the injection volume is set in the target rail pressure correction query table.

[0126] The present invention discloses a control method for improving transient response under the constant engine speed control mode. The method proposes a calculation method for engine speed and speed change rate with high precision and low noise, and divides the advantage and disadvantage intervals of the traditional engine speed control algorithm according to it. The speed change rate is used to calculate the dynamic load offset under the engine working conditions where the processing ability of the traditional algorithm is weak, and the target torque of the engine is obtained, and it can be smoothly switched back to the traditional engine speed control method. It can enable the engine performance calibration personnel not to sacrifice the control effect of the traditional engine speed control algorithm at steady state in order to be compatible with all intervals during the bench test of the engine. In addition, during the operation of the engine, the method detects the crankshaft speed signal periodically and with high precision. After dividing the engine state, temporary fine-tuning of the combustion chamber ignition attitude and over-control can be carried out under the transient working conditions with a relatively small time proportion in the entire engine working cycle, further improving the anti-load impact ability of the engine. By combining transient control and steady-state control of the traditional algorithm, "as fast as a rabbit when moving, as quiet as a virgin when still", the engine of the vehicle manufacturer is more competitive in the range extender and power generation fields where the constant speed control mode is used more frequently. The control method for improving transient response under the constant engine speed control mode of the present invention is particularly suitable for engines in the range extender field of construction machinery and generator sets.

[0127] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A control method for improving transient responsiveness under the constant engine speed control mode. During the operation of the engine, the engine control module periodically implements the control method, and the period of each implementation of the control method is the fuel injection period of the engine. Characterized in that, The control method includes the following steps: Step 1: When the engine enters the constant speed operation mode, sample the engine crankshaft signal period to determine the engine speed change rate and the speed value. Step 2: Judge the engine state and whether the state switching condition is satisfied according to the engine speed change rate and the speed value. The engine state is one of steady state or transient state. Step 3: When the engine state switches from steady state to transient state, calculate the dynamic load offset of the engine in transient state relative to the steady state according to the engine speed change rate, and determine the target torque in transient state according to the load offset and the engine data in the previous control cycle when the engine switches from steady state to transient state. Step 4: When the engine state switches from transient state to steady state, initialize the integral term of the traditional speed control PID algorithm according to the differences in the engine operation data when switching from steady state to transient state and from transient state to steady state, calculate the target torque percentage using the traditional speed control PID algorithm, and look up the table to obtain the target torque in steady state. Step 5: According to the target torque corresponding to the engine state, and fine-tune other control parameters to set the engine data, and control the engine output torque to reach the target value.

2. A control method for improving transient responsiveness under the constant engine speed control mode according to claim 1, Characterized in that, The said step 1 includes the following steps: Step 1.1: Eliminate systematic errors, calculate the ratio of the angle of each tooth of the crankshaft to 360° of one revolution of the crankshaft. According to the crankshaft tooth number recorded during the reverse drag at a fixed speed during the factory test run of the engine and the corresponding crankshaft signal interval time, calculate the ratio of each crankshaft signal interval time in one revolution to the sum of all crankshaft interval times, and store the ratio in the memory of the engine control module, denoted as the array r[N] = {r 1 , r 2 , r 3 , …, r n}, where n represents the crankshaft tooth number and N represents the total number of teeth of the crankshaft signal disk; Step 1.2: During the engine operation, every time an edge signal of a crankshaft tooth is detected, calculate the interval time with the adjacent crankshaft signal once, and select different ratios in r[N] according to the tooth number of the crankshaft to calculate the instantaneous speed of the engine. The instantaneous speed values total N elements, denoted as n[N]. Step 1.3: During the engine operation, every time an edge signal of a crankshaft tooth is detected, calculate the interval time with the signal of its own tooth number in the previous circle once. The interval times total N elements, denoted as T[N]. Step 1.4: When the engine is running, every time an edge signal of a crankshaft tooth is detected, the average value of the rotational speeds calculated based on the last three teeth is taken as the average rotational speed. The average rotational speed values total N elements, which are represented by ; Step 1.5: When the engine is running, every time an edge signal of a crankshaft tooth is detected, before calculating the average speed, copy the historical average speed value calculated at the same position in the previous revolution of the engine to the memory of the engine control module. The historical speed values total N elements, represented by ; Step 1.6: Calculate the speed deviation between the instantaneous speed n of the current crankshaft tooth and the constant speed value set by the engine. Step 1.7: Calculate the average rotational speed of the current crankshaft gear and the historical average rotational speed to find the difference, and divide it by the time interval T between the signal of the current time and the signal of its own tooth number in the previous revolution, to obtain the rotational speed change rate.

3. A control method for improving transient responsiveness under the constant engine speed control mode according to claim 2, Characterized in that, The said step 2 is specifically: Judge whether the speed deviation and the speed change rate reach the state switching condition according to the state detected by the engine control module in the previous detection cycle. If the condition is satisfied, switch the engine state. If the condition is not satisfied, continue to use the previous detection state.

4. A control method for improving transient responsiveness under the constant engine speed control mode according to claim 1, Characterized in that, The said transient includes sudden increase mode and sudden decrease mode.

5. A control method for improving transient responsiveness under the constant engine speed control mode according to claim 4, Characterized in that, The said state switching conditions include: 1) Conditions for steady-state to transient - sudden increase mode: The rotational speed deviation range is (-∞, N 1 ), and the numerical unit is revolutions per minute; The rotational speed change rate range is (-∞, dN 1 ), and the numerical unit is revolutions per minute per second; 2) Conditions for transient - sudden increase mode to steady state: The rotational speed deviation range is [N 1 , 0], with the numerical unit being revolutions per minute; The speed change rate range is (dN′ 1 , +∞), and the numerical unit is revolutions per minute per second; 3) Conditions for steady-state to transient - sudden decrease mode: The rotational speed deviation range is (N 2 , +∞), and the numerical unit is revolutions per minute; The speed change rate range is (dN 2 , +∞), and the numerical unit is revolutions per minute per second; 4) Conditions for transient - sudden decrease mode to steady state: The rotational speed deviation range is [0, N 2 , and the unit of the value is revolutions per minute; The range of the rotational speed change rate is (-∞, dN′ 2 ), and the numerical unit is revolutions per minute per second; Each threshold value N 1 , dN 1 , dN' 1 , N 2 , dN 2 , dN' 2 Are preset in the engine control module, and their specific values are obtained from engine bench tests.

6. A control method for improving transient response in a constant engine speed control mode according to claim 1, wherein, step 3 includes the following steps: Step 3.1: When the engine state switches from steady state to transient, according to the rotational speed change rate, look up the dynamic load offset in the dynamic load offset lookup table. The dynamic load offset lookup table is pre-set in the engine control module, and the corresponding relationship between the dynamic load offset and the engine rotational speed change rate is set in the dynamic load offset lookup table; Step 3.2: Record the engine data of the previous control cycle when the engine state switches from steady state to transient; Step 3.3: Add the dynamic load offset in step 3.1 to the engine load before the switching state recorded in step 3.2 to obtain the instantaneous total load value, and look up the target torque of the engine during transient in the pre-set target torque lookup table. The target torque lookup table is pre-set in the engine control module, and the corresponding relationship between the target torque and the engine real-time rotational speed and load is set in the target torque lookup table.

7. A control method for improving transient response in a constant engine speed control mode according to claim 1, wherein, step 4 includes the following steps: Step 4.1: When the engine state switches from transient to steady state, record the engine data of the previous control cycle when the engine state switches from transient to steady state, Step 4.2: According to the differences in the calculation input items of the engine traditional control PID algorithm recorded at the two time points of steady-state to transient and transient to steady state, re-initialize the integral term of the target torque percentage so that the target torque calculated by the traditional control PID algorithm is equal to the target torque calculated by step 3 in the previous control cycle before transient to steady state, and obtain the target torque in the steady state.

8. A control method for improving transient response in a constant engine speed control mode according to claim 6 or 7, wherein, the engine data includes the engine load and the calculation input items of the engine traditional control method. The calculation input items include the rotational speed difference and the integral term of the target torque percentage.

9. A control method for improving transient response in a constant engine speed control mode according to claim 1, wherein, the other control parameters include ignition advance angle, excess air coefficient, and injection pressure.

10. A control method for improving transient response in a constant engine speed control mode according to claim 9, wherein, the fine-tuning of other control parameters to set engine data specifically includes: Fine-tune the ignition advance angle: According to the real-time engine speed difference and fuel injection quantity, look up the ignition advance angle correction value of the engine in the pre-set ignition advance angle correction query table; the ignition advance angle correction query table is pre-set in the engine control module, and the corresponding relationship between the ignition advance angle correction value and the real-time engine speed difference and injection quantity is set in the ignition advance angle correction query table; Fine-tune the excess air coefficient: According to the real-time engine speed difference and fuel injection quantity, look up the excess air coefficient correction value of the engine in the pre-set excess air coefficient correction query table; the excess air coefficient correction query table is pre-set in the engine control module, and the corresponding relationship between the excess air coefficient correction value and the real-time engine speed difference and injection quantity is set in the excess air coefficient correction query table; Fine-tune the injection pressure: According to the real-time engine speed difference and fuel injection quantity, look up the target rail pressure correction value of the engine in the pre-set target rail pressure correction query table for the fuel high-pressure common rail; the target rail pressure correction query table is pre-set in the engine control module, and the corresponding relationship between the target rail pressure correction value and the real-time engine speed difference and injection quantity is set in the target rail pressure correction query table.

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