阅读说明：本技术 一种基于进气压差的发动机转速估计方法 (Engine speed estimation method based on intake pressure difference ) 是由 唐亮 石珂 邢锐南 于 2021-08-30 设计创作，主要内容包括：本发明提供一种基于进气压差的发动机转速估计方法,涉及汽车发动机技术领域,该方法包括：连续实时采集发动机的进气压差信号；将采集到的发动机实时的进气压差信号缓存到缓冲区中；每存储时间T的进气压差信号数据后就对缓冲区在时间T内存储的进气压差信号进行平滑数据处理；对平滑数据处理后的进气压差信号执行周期检测算法,计算进气压差波动频率；对计算出的进气压差波动频率进行修正；根据修正后的进气压差波动频率计算出发动机转速。本发明能够解决一般传感器与流量计无法获取转速信息的问题,将依据该方法计算出的发动机转速代入发动机理想流量计算公式参与计算,能大幅提高发动机流量计算精度。(The invention provides an engine speed estimation method based on air intake pressure difference, which relates to the technical field of automobile engines and comprises the following steps: continuously acquiring an air inlet pressure difference signal of the engine in real time; caching the acquired real-time air inlet pressure difference signal of the engine into a buffer area; smoothing data processing is carried out on the air inlet pressure difference signal stored in the buffer area in the time T after the air inlet pressure difference signal data of the time T are stored; executing a periodic detection algorithm on the air inlet pressure difference signal after the smooth data processing, and calculating the fluctuation frequency of the air inlet pressure difference; correcting the calculated fluctuation frequency of the intake pressure difference; and calculating the engine speed according to the corrected fluctuation frequency of the intake pressure difference. The invention can solve the problem that the common sensor and the flowmeter can not obtain the rotating speed information, substitutes the rotating speed of the engine calculated according to the method into the ideal flow calculation formula of the engine to participate in calculation, and can greatly improve the flow calculation precision of the engine.)

1. A method of estimating engine speed based on differential intake pressure, the method comprising the steps of:

continuously acquiring an air inlet pressure difference signal of the engine in real time;

caching the acquired real-time air inlet pressure difference signal of the engine into a buffer area;

smoothing data processing is carried out on the air inlet pressure difference signal stored in the buffer area in the time T after the air inlet pressure difference signal data of the time T are stored;

executing a periodic detection algorithm on the air inlet pressure difference signal after the smooth data processing, and calculating the fluctuation frequency of the air inlet pressure difference;

and correcting the calculated fluctuation frequency of the intake pressure difference and calculating the rotating speed of the engine.

2. A differential intake pressure-based engine speed estimation method according to claim 1, wherein the capacity of the buffer area is not less than the sum of the amounts of storage space occupied by the differential intake pressure signals collected during one cycle of fluctuation of the differential intake pressure signals; the time T is not less than the intake pressure difference signal fluctuation period.

3. A method of estimating engine speed based on differential intake air pressure according to claim 1, wherein the smoothed data processing means is low-delay filtering.

4. The intake pressure difference-based engine speed estimation method according to claim 1, wherein the expression for calculating the fluctuation frequency of the intake pressure difference is:

in the formula, n is (sum of times of zero crossing points of the intake pressure difference in the buffer area/2), and T is the difference value of the subscript between two gradient rising zero crossing points of the intake pressure difference.

5. A differential intake pressure based engine speed estimation method as claimed in claim 1, wherein the collected differential intake pressure signal enters and exits the buffer area on a first-in first-out basis.

Technical Field

The invention relates to the technical field of automobile engines, in particular to an engine speed estimation method based on air intake pressure difference.

Background

With the establishment of the national six-emission regulations, the requirements on the air intake system of the automobile are higher and higher, especially for heavy trucks driven by diesel engines. In order to obtain the mixture gas with the optimal concentration under various working conditions of the electronic fuel injection engine, the air quantity sucked into the engine at each moment must be accurately measured and used as a main basis for calculating and controlling the fuel injection quantity by the ECU. Currently, only one company in germany can provide internationally-formed intelligent venturi-based flow meters, and the intake pressure difference based on the venturi can cause data to periodically pulsate due to the rotation of an engine in the actual use process. The ideal gas flow calculation formula has the term of rotating speed, but the venturi-based orifice plate flowmeter cannot acquire rotating speed information, so that the ideal gas flow calculation formula cannot be used for correctly distinguishing flow values at different rotating speeds, and particularly under the working condition of high rotating speed, the amplitude change of differential pressure and the flow trend are completely different, so that the accuracy of the calculated engine flow value is seriously influenced.

Disclosure of Invention

Aiming at the technical problem, the invention provides an engine rotating speed estimation method based on the air inlet pressure difference, which can estimate the corresponding engine rotating speed according to the pressure difference of the current working condition, and substitutes the engine rotating speed calculated according to the method into the intelligent Venturi flow meter, thereby greatly improving the calculation precision of the intelligent Venturi flow meter.

In order to achieve the purpose, the invention adopts the technical scheme that:

the invention provides an engine speed estimation method based on air intake pressure difference, which comprises the following steps:

continuously acquiring an air inlet pressure difference signal of the engine in real time;

caching the acquired real-time air inlet pressure difference signal of the engine into a buffer area;

smoothing data processing is carried out on the air inlet pressure difference signal stored in the buffer area in the time T after the air inlet pressure difference signal data of the time T are stored;

executing a periodic detection algorithm on the air inlet pressure difference signal after the smooth data processing, and calculating the fluctuation frequency of the air inlet pressure difference;

and correcting the calculated fluctuation frequency of the intake pressure difference and calculating the rotating speed of the engine.

Preferably, the capacity of the buffer area is not less than the sum of the storage space occupied by the intake differential pressure signals collected in one intake differential pressure signal fluctuation period; the time T is not less than the intake pressure difference signal fluctuation period.

Preferably, the smooth data processing mode is low-delay filtering.

Preferably, the expression for calculating the fluctuation frequency of the intake differential pressure is:

in the formula, n is (sum of times of zero crossing points of the intake pressure difference in the buffer area/2), and T is the difference value of the subscript between two gradient rising zero crossing points of the intake pressure difference.

Preferably, the collected differential pressure signal enters and exits the buffer area according to a first-in first-out principle.

The technical scheme has the following advantages or beneficial effects:

the invention provides an engine speed estimation method based on air intake pressure difference, which relates to the technical field of automobile engines and comprises the following steps: continuously acquiring an air inlet pressure difference signal of the engine in real time; caching the acquired real-time air inlet pressure difference signal of the engine into a buffer area; smoothing data processing is carried out on the air inlet pressure difference signal stored in the buffer area in the time T after the air inlet pressure difference signal data of the time T are stored; executing a periodic detection algorithm on the air inlet pressure difference signal after the smooth data processing, and calculating the fluctuation frequency of the air inlet pressure difference; correcting the calculated fluctuation frequency of the intake pressure difference; and calculating the rotating speed of the engine according to the corrected fluctuation frequency of the air intake pressure difference, and repeating the steps to realize continuous estimation of the rotating speed of the engine. The invention can solve the problem that the common sensor and the flowmeter can not obtain the rotating speed information, substitutes the rotating speed of the engine calculated according to the method into the ideal flow calculation formula of the engine to participate in calculation, and can greatly improve the flow calculation precision of the engine.

Drawings

The invention and its features, aspects and advantages will become more apparent from reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Like reference symbols in the various drawings indicate like elements. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

Fig. 1 is a schematic flowchart of an engine speed estimation method based on an intake pressure difference according to embodiment 1 of the present invention;

FIG. 2 is a rotation speed estimation result and error obtained by an engine rotation speed estimation method based on an intake air pressure difference according to embodiment 1 of the present invention;

FIG. 3 is a graph of average error of engine flow values at different rotational speeds according to the method for estimating engine rotational speed based on intake air pressure difference provided in embodiment 1 of the present invention;

fig. 4 shows the estimation result and error of the flow rate value obtained by the method for estimating the engine speed based on the intake air pressure difference according to embodiment 1 of the present invention.

FIG. 5 is a comparison graph of an estimated engine flow value and a recorded engine mount flow value calculated directly from differential pressure, absolute pressure values and temperature, and corrected by corresponding coefficients.

Detailed Description

The invention will be further described with reference to the following drawings and specific examples, which are not intended to limit the invention thereto.

Example 1:

the engine speed estimation method based on the air intake pressure difference provided by the embodiment 1 of the invention comprises the following steps:

s101, continuously acquiring an air inlet pressure difference signal of an engine in real time;

s111, caching the acquired real-time air inlet pressure difference signal of the engine into a buffer area;

s121, after the air inlet pressure difference signal data of the time T are stored, smooth data processing is carried out on the air inlet pressure difference signal stored in the buffer area in the time T;

s131, executing a periodic detection algorithm on the air inlet pressure difference signal after the smooth data processing, and calculating the fluctuation frequency of the air inlet pressure difference;

s141 corrects the calculated intake differential pressure fluctuation frequency to calculate the engine speed.

The method for estimating the rotating speed of the engine based on the air inlet pressure difference is specifically applied to a Venturi intelligent flowmeter during implementation, the Venturi intelligent flowmeter is one of important sensors of an electronic injection engine, the working principle of the method is that a fluid flow beam forms local contraction at a throttling position through a throttling device in a pipeline, so that the flow speed is increased, the static pressure is reduced, differential pressure is generated before and after throttling, and the flow of gas flowing through the throttling device is calculated by measuring the air inlet differential pressure of the engine and substituting the measured differential pressure into an ideal gas flow. Specifically, the ideal gas flow calculation formula is as follows:

wherein, K_sIs the rotational speed of the engine, A_qThe sectional area of the throat (the sectional area adopted by the novel sensor is 0.000754m2), epsilon is the gas expansion coefficient, dp is the differential pressure value measured by the sensor, and rho is the air density at the throat, and the specific calculation formula is as follows:

wherein P is_absIs the absolute pressure at the throat, R_airIdeal gas constant for air (288 as a default), T_kIs the temperature at the throat. The calculation formula of the gas expansion coefficient is as follows:

wherein dp_DesignPressure difference value before and after a specific throat set by manufacturer, P_abs，DesignAbsolute pressure value, K, at a specific throat set by the manufacturer_epsIs constant (set to 1000 in embodiment 1 of the present invention), and is seen from the ideal gas flow calculation formula, ideal conditionsAccurate measurement of the engine flow value requires real-time engine differential pressure values, absolute pressure values, temperatures and rotational speeds. However, the existing venturi intelligent flow meter cannot acquire the real-time rotating speed of the engine, can only calculate according to the pressure difference, the absolute pressure value and the temperature, and then estimate the engine flow value through corresponding coefficient correction, referring to fig. 5, the comparison precision of the engine flow value obtained by the method and the flow value recorded by an engine rack in an experiment of an inventor is low, the error is large, further the control on the fuel injection quantity of an automobile is influenced, and the current requirement that the mixed gas with the optimal concentration can be obtained by an automobile air intake system under various working conditions is difficult to meet.

In order to solve the above problems, the inventor has conducted long-term engine working condition research experiments, and found that the fluctuation frequency of the pressure difference data of the engine under different rotation speed conditions is different in the experiments, and the linear relation exists between the fluctuation frequency of the pressure difference data and the rotation speed of the engine, accordingly, referring to fig. 1, the inventor sets a buffer area in the venturi intelligent flowmeter, continuously collects the air intake pressure difference signal of the engine in real time, and caches the collected air intake pressure difference signal into the buffer area, preferably, the capacity of the buffer area is not less than the sum of the storage space occupied by the air intake pressure difference signal collected in one air intake pressure difference signal fluctuation period; the time T is not less than the intake pressure difference signal fluctuation period. For example, since the rotation speed of a 4-cylinder diesel engine is usually 3200 to 750 revolutions and 750 revolutions to an idle speed, the cycle of fluctuation of the differential pressure of intake air of the diesel engine is about 30ms, and therefore the buffer size is set to 40. In order to avoid the influence of noise data caused by the pulsation of the air inlet pressure difference signal on subsequent data processing, after the air inlet pressure difference signal data of the time T are stored in the buffer area, the air inlet pressure difference signal of the buffer area is periodically detected, and the smooth data processing is carried out on the air inlet pressure difference signal stored in the buffer area in the time T before the fluctuation frequency of the air inlet pressure difference is calculated; the smooth data processing is preferably low-delay filtering, harmonic interference can be effectively weakened, an intake pressure difference signal waveform similar to a sine wave is obtained, then a period detection algorithm is executed on the intake pressure difference signal after the smooth data processing, and the intake pressure difference fluctuation frequency is calculated, specifically, the intake pressure difference waveThe dynamic frequency is calculated by the formulaIn the formula, n is (sum of times of zero crossing points of the intake pressure difference in the buffer area/2), and T is the difference value of the subscripts between two gradient rising zero crossing points of the intake pressure difference; in order to further improve the accuracy and reliability of the fluctuation frequency of the intake pressure difference, the calculated fluctuation frequency of the intake pressure difference is corrected, the engine speed is calculated according to the linear relation between the corrected fluctuation frequency of the intake pressure difference and the engine speed, the calculated engine speed is substituted into an ideal gas flow calculation formula, the comparison between the engine speed estimated according to the method and the implementation speed calculated by an engine bench can be referred to FIG. 2, and the probability that the error is less than 1 speed/minute is 0.17528; the probability that the error is greater than or equal to 1 rpm and less than or equal to 5 rpm is 0.80271; in summary, the probability that the error is greater than 5 rpm and less than or equal to 10 rpm is 0.02201, and the probability that the error is greater than 10 rpm is 0, so that the error of the engine flow measurement result obtained by substituting the engine speed obtained by the engine speed estimation method based on the intake pressure difference into the ideal gas flow formula is mainly concentrated on 1-5 kg, and the overall error can be controlled within 1.3%. The error precision meets the precision requirement of 2 percent, and the high-precision estimation of the engine rotating speed is realized.

Referring to fig. 3, average errors and standard deviations at different rotation speeds in an experiment are recorded, the average error rate is below 1%, and engine flow errors of more than 5 kg mainly occur when the working condition changes, and the rotation speed changes from one value to another value when the working condition changes. The comparison result of the air flow value obtained by substituting the estimated rotating speed into the ideal flow calculation formula and the flow value recorded by the engine bench is shown in fig. 4, compared with fig. 5, the measurement precision of the engine flow value is effectively improved, and a more accurate and reliable basis can be provided for controlling the fuel injection quantity of the automobile.

The above description is of the preferred embodiment of the invention; it is to be understood that the invention is not limited to the particular embodiments described above, in that devices and structures not described in detail are understood to be implemented in a manner common in the art; any person skilled in the art can make many possible variations and modifications, or modify equivalent embodiments, without departing from the technical solution of the invention, without affecting the essence of the invention; therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.