WO2011068258A1

WO2011068258A1 - Control method for a free-piston engine using a prediction curve and a free-piston engine controlled thereby

Info

Publication number: WO2011068258A1
Application number: PCT/KR2009/007155
Authority: WO
Inventors: 이길용
Original assignee: 주식회사 엔진텍
Priority date: 2009-12-02
Filing date: 2009-12-02
Publication date: 2011-06-09

Abstract

The present invention relates to a control method for a free-piston engine, comprising the steps of: acquiring measurement data containing a measured-position value and a measured-time value obtained by measuring the position and the time of a free piston at a specific point; acquiring calculation data containing a calculated-position value and a calculated-time value obtained by calculating the position and the time at the specific point from a predetermined standardisation curve; determining a prediction curve for predicting the pattern of movement of the piston after the specific point by subjecting the standardisation curve to conversion based on the measurement data and the calculation data; and controlling the free-piston engine by using the prediction curve, wherein a pattern of movement which is very similar to the actual pattern of movement of the free piston can be predicted, and the free-piston engine control performance can be improved.

Description

【Specification】

[Name of invention]

Prepiston engine control method using predictive curve and prepiston engine controlled by it

Technical Field

The present invention relates to a control method of a pre-piston engine, and more particularly, to a control method of a pre-piston engine using a predictive curve for predicting a driving pattern of the pre-piston and a pre-piston engine controlled by the pre-piston engine. It is about.

Background Art

The free-pistion engine is a straight-stroke reciprocating engine, a two-stroke, one-cycle engine, with no crank mechanism. The prepiston engine is connected in a straight line through one shaft (moving shaft), and can be connected to an energy converter such as a hydraulic pump or a generator to generate energy. The prepiston engine has a high piston speed, which allows the mixer to be compressed at a high pressure to realize a high compression ratio. Also, since there is no cramp mechanism, power conversion loss is small and the engine efficiency can be overcome recently. It is attracting much attention.

However, the pre-piston engine is difficult to control due to the variable stroke, and because of the characteristics of the pre-piston engine, the inertia cannot be used, so if the control fails at least once, the engine stops. In addition, a phenomenon in which the driving pattern such as the driving speed changes frequently due to the absence of an inertial body.

Various control methods have been proposed to solve such control problems of the prepiston engine. In particular, Johansen et al. Proposed a method of controlling the prepiston engine by predicting the movement pattern of the pre-piston by the sine curve (Free Piston Diesel Engine Timing and Control. Control Electronic Cam. 一 and Crankshaft, Johansen et al, IEEE Trans. Control

Systems Technology, vol. 9, 2001), since this method predicts the pre-piston driving pattern by the sine curve, which is the driving pattern of the reciprocating engine, even though the driving pattern of the pre-piston engine and the driving pattern of the reciprocating engine are completely different, the top dead center and / or the bottom dead center. The high rate of error in the vicinity made it difficult to achieve precise engine control.

[Detailed Description of the Invention]

[Technical problem]

The present invention has been made to solve the above problems, the first problem to be solved by the present invention is to provide a control method of the pre-piston engine using a predictive curve obtained by converting the standardized curve will be.

The second problem to be solved by the present invention is to provide a pre-piston engine controlled by the control method of the pre-piston engine described above. Technical Solution

The present invention to achieve the first object,

(a) measuring the position and time of the pre-piston at a specific point to obtain measurement data including the measurement position value and the measurement time value;

(b) obtaining the calculation data including the calculation position value and the calculation time value by calculating the position and time of the specific point in a predetermined normalization curve;

(c) determining a prediction curve predicting the movement pattern of the pre-piston after the specific point by converting the normalization curve based on the measured data and the calculated data; And

and (d) controlling the prepiston engine using the predictive curve. Here, the normalization curve is preferably an ideal movement pattern of the pre-piston.

In addition, in the step (C), the prediction curve may be determined by the following equation.

X

Where x = f (t) is a standardized curve function representing the pre-piston position X at time t, n _x is a position conversion coefficient that is the ratio of the calculated position value to the measured position value, and n _t is the measurement time Time conversion factor which is a ratio of the calculated time value to a value)

In addition, the specific point includes the top dead center of the pre-piston, the position conversion coefficient is the ratio of the calculated position value to the measurement position value at the top dead center, the time conversion coefficient is the measurement time value at the top dead center It is preferable that it is the ratio of said calculation time value with respect to.

In addition, the specific point includes the first augmentation point of the pre-piston, the position conversion coefficient is a ratio of the position value of the calculated data to the position value of the measurement data at the top dead center, the time conversion coefficient is It is preferable that it is a ratio of the time value of the said calculation data with respect to the time value of the said measurement data in a 1st center point.

The specific point includes the bottom dead center of the prepiron, the position conversion coefficient is a ratio of the position value of the calculated data to the position value of the measurement data at the bottom dead center, and the time conversion coefficient is the bottom dead center. Is a ratio of the time value of the calculated data to the time value of the measured data.

The specific point may also include a second center point of the prepiston, and the position conversion coefficient may correspond to the position value of the measurement data at the bottom dead center. Preferably, the time conversion coefficient is a ratio of the time value of the calculated data to the time value of the measured data at the second center point.

In addition, in step (d), the ignition timing and injection timing of the prepiston engine may be controlled using the prediction curve.

In addition, the position of the prepistone may be represented by a displacement or an angle. The present invention to achieve the second object,

In a pre-piston engine comprising a combustion cylinder, a prepistron disposed to reciprocate in the combustion cylinder along a movable shaft, an ignition plug installed in the combustion cylinder, and an injector for supplying fuel into the combustion cylinder.

Detection means for detecting a position of the prepistone; And

An engine control unit controlling an ignition timing of the spark plug and an injection timing of the injector,

The engine control unit provides a pre-piston engine, characterized in that the control algorithm including a control method of the pre-piston engine using the above-described prediction curve.

Advantageous Effects

The control method of the pre-piston engine according to the present invention uses a predictive curve obtained by converting a predetermined standardized curve based on measurement data measured by a pre-piston engine in actual operation, so that the motion is very similar to the actual motion pattern of the pre-piston. Predict patterns. In addition, since the ignition timing and injection timing of the prepiston engine can be determined using the predicted motion pattern, the prepiston engine can be controlled more accurately, thereby maximizing the control performance and stability of the prepiston engine. .

[Brief Description of Drawings]

1 is a schematic structural diagram of a general prepiron engine. 2 is a diagram illustrating a movement pattern of the pre-piston.

3 is a graph showing the pressure-volume diagram of an Otto cycle.

4 is a flowchart illustrating a control method of a prepiston engine according to an embodiment of the present invention.

5 is a graph showing the prediction curve of the B section obtained using the measurement curve and the normalization curve of the A section.

FIG. 6 is a graph showing a prediction curve of a section C obtained by using the measurement curve and the normalization curve of the section B. FIG.

7 is a diagram illustrating a process of controlling a prepiston engine according to a prediction curve according to an embodiment of the present invention.

8 is a structural diagram of a pre-piston engine according to an embodiment of the present invention. [Form for implementation of invention]

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. However, these examples are intended to illustrate the present invention in more detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited thereto.

1 is a schematic structural diagram of a general prepiston engine.

In Figure 1, B is the diameter of the bore, A is the cross-sectional area of the bore, TDC and BDC are the top dead center and the bottom dead center of the pre-piston, respectively, P _L is the pressure of the left cylinder, P _R is the pressure of the right cylinder, s is stroke ( stroke, x is the displacement of the prepiston, x _s is the half stroke, and is the maximum half stroke.

The equation of motion of the prepistone having the structure as shown in FIG. 1 is as follows. [Equation 1]

Where F _f is the frictional force, F _ffl is the load absorbing power, and one cycle It can be assumed that the frictional force and the load absorbing force occur within the same.

The solution of the differential equation represented by Equation 1 may be used as a standardized curve representing an ideal motion pattern of the prepiston.

2 is a diagram illustrating a movement pattern of the prepiston to explain the concept of the prepiston control method according to an embodiment of the present invention.

In FIG. 2, the moment when the prepiston passes the top dead center (TDC), predicts the section B (the section from the top dead center to the first center point), and the moment the prepiston passes the first center point, the section C (at the first center point) Predict the interval to the bottom dead center), predict the interval D (the interval from the bottom dead center to the second center of gravity) when the prepiston passes the bottom dead center (BDC), and the moment A when the prepiston passes the second center of gravity; 'Section (section from the second center point to the top dead center) can be predicted. Prediction curves in each section can be obtained by coordinate transformation of the above-described standardization curve, and the coordinate transformation method can be performed in angle units or ratio units in the same way as in a reciprocating engine. A detailed method of calculating the prediction curve will be described later. Here, the center point is a point that is the geometric center of the top dead center and the bottom dead center, means a point where the pre-piston displacement is 0, in this specification, the first center point is the center point that passes when the pre-piston moves from the top dead center to the bottom dead center. The second center point refers to the center point that passes when the prepiston moves from the bottom dead center to the top dead center.

3 is a graph showing the pressure-volume diagram of an Otto cycle.

The Otto cycle shown in FIG. 3 shows the pressure-volume relationship of the left cylinder in the prepiston engine shown in FIG. 1, and the pressure-volume diagram of the right cylinder may be displayed symmetrically.

Referring to FIG. 3, the processes from 1 to 2 are compression strokes, the processes from 2 to 3 are explosion strokes, the processes from 3 to 4 are expansion strokes, and the processes from 4 to 1 'are scavenging strokes and suction strokes. to be. The process from 1 'to 1 It is an inertial expansion stroke. The right cylinder goes through the reverse stroke of the above process. The governing equation for the compression stroke from 1 'to 2 is

[Equation 2]

Yes

Where Pc is the pressure in the compression stroke from 1 'to 2, Vc is the volume at this time, and n is the specific heat ratio.

The governing equations for the expansion strokes from 3 to 4 are as follows.

[Equation 3]

^ e where Pe is the pressure in the expansion stroke from 3 to 4, Ve is the volume at this time, n is the specific heat ratio.

The prepiston movement, defined by equations (2) and (3), occurs simultaneously in the left and right cylinders.

When Ρ _Γ and V _r are determined in Equation 2, Vc is determined by the displacement of the piston, and thus Pc is determined. Meanwhile, in Equation 3, P ₃ and V ₃ are determined, Ve is determined by the displacement of the piston, and Pe is also determined.

As a result, Equations 2 and 3 indicate that the C section can be predicted through the B section of FIG. 2 and the A 'section can be predicted through the D section. Of course, the actual explosion that occurs during combustion is proportional to the amount of fuel, but the process is so complex that it is virtually unpredictable. However, the purpose of engine control is to predict the final ignition timing, and the ignition timing can be controlled by the advance or perception conditions by the prediction, so that the top dead center can be controlled constantly. Hereinafter, a method of controlling a prepiston engine using a prediction curve according to an embodiment of the present invention will be described.

4 is a flowchart of a method for controlling a prepiston engine according to an embodiment of the present invention, and FIG. 8 is a structural diagram of a prepiston engine 100 according to an embodiment of the present invention.

A control method of a prepiston engine according to an embodiment of the present invention includes: acquiring measurement data including an axis position value and a measurement time value by calculating the position and time of the prepiston at a specific point (S10); Obtaining calculated data including a calculated position value and a calculated time value by calculating a position and a time of the specific point in a predetermined normalization curve (S20); Determining a prediction curve predicting the movement pattern of the pre-piston after the specific point by converting the normalization curve based on the measured data and the calculated data (S30); And controlling the prepiston engine using the genital prediction curve (S40).

The measurement data acquiring step S10 may be performed by using detection means installed in the prepiston engine 100. The detecting means 60 is a device for detecting the time-specific position of the prepiron 30, for example, an encoder installed on the outer circumferential surface of the pre-piston engine 100 may be used. By using such a detection means, the position value and time value of the prepiston at a specific point (for example, top dead center, bottom dead center, center point, etc.) can be measured in real time.

Computation data acquisition step (S20) is a step of calculating the position value and time value of the pre-piston at a specific point using a predetermined standardization curve. Assuming that the standardized curve is a solution of the differential equation defined by Equation 1, the calculation data can be easily obtained by substituting the position value X of the prepiston in the solution.

The measurement data acquisition step (S10) and the calculation data acquisition step (S20) described above do not necessarily have to maintain their prognostic relationship, and any of the two steps You may perform the steps first.

Prediction curve determination step (S30) is a step of determining the prediction curve by converting the standardized curve on the basis of the measurement data and the calculation data obtained in the above-described step. This prediction curve, like the normalization curve, is expressed as a function of the position of the prepiston 30 over time. The specific process of determining the prediction curve is as follows.

5 is a graph showing the prediction curve p of section B obtained using the measurement curve M of section A and the standardization curve S. FIG.

In Fig. 5, S is an idealized standard curve representing the position (X) of the prepistone over time (t), S is a measurement curve indicating the movement pattern of the pre-piston actually measured through the above-described means, P is Predictive curves for predicting the pre-piston movement pattern.

In FIG. 5, X * and t * denote the position and time values of the prepistone in the normalization curve S, respectively, and χ ', t' denote the position and time values of the prepistone in the measurement curve M, respectively. t denotes a position value and a time value of the prepistone in the prediction curve P, respectively.

Therefore, the following equation holds for the function f that defines the standardization curve S.

[Equation 4]

Here, the functions f and g are inverse functions of each other.

The conversion factor for converting the standardized curve is defined as the ratio of the calculated data obtained from the standardized curve to the measured data obtained from the measured curve at a specific point.

For example, a transformation coefficient for obtaining a prediction curve of a section B is defined as follows by determining a specific point as a top dead center. [Equation 5]

^■ TDC _ ^X TDC

-,, η _χ = — ᅳ ᅳ

TDC ^x TDC where n _t is the time conversion factor, which is the ratio of the time value of the normalization curve to the time value of the measurement curve at the top dead center of the prepiston, and n _x is the position conversion coefficient of the measurement curve at the top dead center of the prepiston. The ratio of the position value of the normalization curve to the position value. Therefore, it is possible to determine the time conversion coefficient and the position conversion coefficient at the top dead center by the equation (5).

If the relationship between the prediction curve and the normalization curve is defined as X * = n _x Xx, t * = n _t Xt using the calculated transformation coefficient, the prediction curve is determined as follows. [Equation 6]

Therefore, by calculating the position transformation coefficient and the time transformation coefficient from the predetermined normalization curve and the top dead center of the prepiston, the prediction curve which is the motion pattern of the prepistone in the section B can be calculated using Equation (6).

FIG. 6 is a graph showing the prediction curve P of the C section obtained using the measurement curve M of the B section and the standardization curve S. FIG.

The transformation coefficient for obtaining the prediction curve of the C interval may be defined as follows by determining a specific point as the first center point.

[Equation 7]

The time conversion coefficient and position conversion coefficient defined by Equation (7) A prediction curve for predicting the pre-piston motion pattern in the subinterval C region to the prediction curve function defined by Equation 6 may be determined.

The same process as described above may be used to calculate the prediction curves for each of the D section and the A 'section.

That is, in order to determine the prediction curve of the D interval, when the bottom dead center is determined as a specific point, the time conversion coefficient is defined as the ratio of the time value of the normalization curve to the time value of the measurement curve at the bottom dead center, and the position transformation coefficient is It is defined as the ratio of the position value of the normalization curve to the position value of the measurement curve at the point.

In order to determine the prediction curve of section A ', when the second center point is determined as a specific point, the time conversion coefficient is defined as the ratio of the time value of the normalization curve to the time value of the measurement curve at the second center point, and the position conversion coefficient is It is defined as the ratio of the position value of the normalization curve to the position value of the measurement curve at the bottom dead center.

Through the above-described process, the prediction curve of the subsequent section may be determined using the measurement curve (or measurement data) and the standardization curve (or calculation data) of the previous section.

Pre-piston engine control step (S40) is a step of controlling the pre-piston engine using the prediction curve obtained through the above-described process. In this step, the top dead center of the pre-piston can be made constant by adjusting the ignition timing of the spark plug, the injection timing of the injector, etc. using the determined prediction curve.

FIG. 7 is a graph illustrating a prediction curve derived in a method of controlling a prepiston engine according to an embodiment of the present invention.

The predictive curve of FIG. 7 predicts the driving pattern of the left prepiston in the structural diagram of the prepiston engine shown in FIG. 8, where "L" represents the left prepiston engine 100 and "prefers the right prepiston engine". (100 ¹ ) is referred to.

As shown in FIG. 8, in the case of the opposing pre-piston engines in which the prepiron 30 is installed at both ends of the movable shaft 20 integrally formed with the piron rod, the movements of the respective prepirons are symmetrical with each other. Is made of, It is possible to control the pre-piston engines on both sides by using the operation pattern of the pre-piston.

As illustrated in FIG. 7, the ignition timing and injection timing of the prepiston engine may be determined through the prediction curve. Moreover, in the case of the pre-piston engine provided with the intake valve, the exhaust valve, and the scavenging valve, the intake, exhaust, and scavenging timings can be appropriately adjusted by opening and closing the corresponding valve.

The standardized curve, the measured curve, and the predicted curve have been described by indicating the displacement of the prepistron position. However, when the prepiston position is converted to an angle corresponding to the reciprocating engine, the prepiston engine can be controlled in the same manner as the conventional reciprocating engine. Can be.

8 is a structural diagram of a pre-piston engine according to an embodiment of the present invention, wherein the pre-piston engine 100 is arranged to reciprocate the combustion cylinder 10 and the combustion cylinder along the movable shaft 20. A pre-piston 30, an ignition plug 40 installed inside the combustion cylinder, an injector 50 for supplying fuel to the combustion cylinder, a detection means 60 for detecting the position of the pre-piston and the ignition plug Engine control unit 70 for controlling the ignition timing and the injection timing of the injector.

In addition, the prepiston engine 100 is provided with an intake port 11 and an exhaust port 12 in communication with the combustion cylinder.

Pre-piston engines are internal combustion engines using fuels such as hydrogen and two-stroke, one-cycle engines. The pre-piston engine 100 according to an embodiment of the present invention is preferably an opposite pre-piston engine in which the pre-pistons 30 are respectively installed at both ends of the movable shaft 20 for reciprocating linear motion. In this case, both pre-piston engines are arranged to alternately explode. Therefore, in order to generate energy by using the driving force in the linear direction transmitted from both prepiron engines, an energy conversion device 80 such as a hydraulic pump or a generator may be installed in the central portion of the movable shaft. The detection means 60 is installed on one side of the pre-piston engine in association with the movable shaft 20, and the movable shaft 20 is installed in a structure capable of detecting the position of the movable shaft over time when the movable shaft 20 performs a reciprocating linear motion. Can be.

On the other hand, the engine control unit 70 is equipped with a control algorithm including a control method of the pre-piston engine according to an embodiment of the present invention. The engine control unit 70 is configured to transmit and receive data to and from the detection means 70 and to transmit and receive control signals to and from the injector 50 and the spark plug 40.

The injector 50 and the spark plug 40 may be controlled by the engine control unit 70 at an operation time and an operation time. That is, the injection timing (operation time and operation time) of the injector and the ignition timing (operation time and operation time) of the spark plug can be appropriately adjusted using the above-described prediction curve.

Therefore, the pre-piston engine 100 according to the present invention can control the variable stroke based on the predictive curve for predicting the driving pattern of the pre-piston 30, it can be expected a control effect similar to the control of the reciprocating engine.

In addition, the standardized curve can be represented by various variables such as the angle or the number of ^' dimensions ^' instead of the displacement of the prepiston.In particular, the standardized curve is defined by the angle unit corresponding to the reciprocating engine and the prediction curve is displayed by the angle. Can be controlled in the same way as a conventional reciprocating engine. All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims

[Range of request]

[Claim 1]

(b) calculating position and time of the specific point in a predetermined normalization curve to obtain calculated data including a calculated position value and a calculated time value;

and (d) controlling the prepiston engine using the prediction curve.

[Claim 2]

In that U term,

The normalization curve control method of the pre-piston engine using a prediction curve, characterized in that representing the ideal movement pattern of the pre-piston.

[Claim 3]

The method of claim 1,

The control method of the pre-piston engine using the prediction curve in the step (c) is characterized in that the prediction curve is determined by the following equation.

Where X = f (t) is a standardized curve function representing the pre-piston position X at time t, is a position conversion coefficient that is the ratio of the calculated position value to the measured position value, and n _t is the measured time value Is a time conversion factor that is the ratio of the calculated time values for

[Claim 4]

The method of claim 3,

The specific point includes the top dead center of the prepistone

The position conversion coefficient is a ratio of the calculated position value to the measured position value at a top dead center,

And the time conversion coefficient is a ratio of the calculated time value to the measured time value at top dead center.

[Claim 5]

The method of claim 3,

The specific point includes a first center point of the prepiston, the position conversion coefficient is a ratio of a position value of the calculated data to a position value of the measured data at a top dead center,

And the time conversion coefficient is a ratio of a time value of the calculated data to a time value of the measured data at a first increasing center point.

[Claim 6]

According to claim 13,

The specific point includes the bottom dead center of the prepistone,

The position conversion coefficient is a ratio of the position value of the calculated data to the position value of the measured data at the bottom dead center,

And the time conversion coefficient is a ratio of the time value of the calculated data to the time value of the measured data at the bottom dead center.

[Claim 7]

The method of claim 3,

The specific point comprises a second central point of the prepiron, The position conversion coefficient is a ratio of the position value of the calculated data to the position value of the measured data at the bottom dead center;

Said time conversion factor control method for a free piston engine with a prediction curve which is characterized in that the ratio of the time value of the calculated data for the measured ^"time value of the data in a second center point.

[Claim 8]

The method of claim 1,

In the step (d),

The control method of the pre-piston engine using the prediction curve, characterized in that for controlling the ignition timing and injection timing of the pre-piston engine using the prediction curve.

[Claim 9]

According to claim 1,

The position of the pre-piston is a control method of the pre-piston engine using a prediction curve, characterized in that represented by the displacement or angle.

[Claim 10]

A prepiston engine comprising a combustion cylinder, a prepiston arranged to reciprocate in the combustion cylinder along a moving shaft, an ignition plug installed inside the combustion cylinder, and an injector for supplying fuel into the combustion cylinder.

Detection means for detecting a position of the prepistone; And

The engine control unit is a pre-piston engine, characterized in that equipped with a control algorithm including a method according to claim 1.