KR20100018397A - Controller of variable valve timing apparatus - Google Patents

Abstract

PURPOSE: A controller of a variable valve timing system is provided to improve excellent response rate and control precision by reflecting the temperature and the pressure change of oil supplied to an oil control valve. CONSTITUTION: A controller of a variable valve timing system comprises a cam shaft(130), a vane(115), a stator(120), an oil control valve(145), and a sliding mode controller(305). A cam is formed inside the cam shaft. The vane is mounted on one end of the cam shaft. The stator is mounted on the vane and constitutes a retard chamber(100) and an advance chamber(105). The oil control valve supplies oil to the retard chamber and the advance chamber. The sliding mode controller controls the oil control valve. Controlling the oil provided to the retard chamber and the advance chamber through a sliding mode, the sliding mode controller reflects the temperature of the oil provided to the oil control valve and the pressure gradient of the oil.

Description

CONTROLLER OF VARIABLE VALVE TIMING APPARATUS}

The present invention relates to a controller of a variable valve timing mechanism, and more particularly, to a controller of a variable valve timing mechanism that improves the responsiveness of valve timing and ensures robustness against disturbance.

The engine equipped with the variable valve timing mechanism can apply the optimum valve timing according to the driving conditions, thereby improving the fuel efficiency, output and reducing the exhaust gas. In order to improve these performances, the valve timing must be continuously changed at the same time as the operation, and must be supported by fast and accurate control.

The existing variable valve timing mechanism is controlled by a controller of a PID controller or a modified PID controller. The problem with these existing controllers is the need to use a map that matches the temperature or RPM conditions.

Experimental corrections have to be made in each condition to create this map. In addition, this experimental process has a problem that must be performed for each engine due to tolerances.

To overcome this, we need to add a learning algorithm. In addition to these problems, it also has the disadvantage of being vulnerable to unexpected and unknown external input.

9 is a design flowchart of the PID-based controller.

Since the PID-based controller does not reflect the nonlinear characteristics of the variable valve timing mechanism, other control characteristics cannot be satisfied depending on the oil temperature condition and engine speed (RPM). Therefore, it is necessary to tune through experiments according to each condition, make a map, and use it for control.

Accordingly, the present invention has been made to solve the above problems, and to provide a controller of a variable valve timing mechanism that ensures the speed, accuracy and robustness of unknown disturbance of the variable valve timing mechanism.

The controller of the variable valve timing mechanism according to the present invention for achieving the above object is a camshaft cam is formed, a vane mounted on one end of the camshaft, a stator mounted to the vane to form a perceptual chamber and a true chamber, An oil control valve for supplying oil to the crust chamber and the truth chamber and a sliding control unit for controlling the oil control valve, wherein the sliding control unit reflects the pressure change of the oil according to the temperature of the oil and the engine of the engine. And a sliding control unit controlling oil supplied to the perception chamber and the advance chamber.

In addition, it is designed in consideration of the disturbance and other unknown disturbance according to the variation of the battery voltage, and the oil flow model passing through the oil control valve that the oil is controlled, the pressure model in the chamber and the crust chamber and the motion model of the rotor I use it.

As described above, according to the controller of the variable valve timing mechanism according to the present invention, it is possible to ensure the responsiveness and control accuracy superior to the conventional PID-based controller.

In addition, it is possible to apply a relatively simple calibration than the PID controller by reflecting the temperature and oil pressure characteristics in the model and quantifying the robustness against uncertainty and disturbance.

In addition, it can secure robustness against unknown disturbances as well as temperature changes and engine speed changes.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail as follows.

A mathematical model including oil characteristic change according to temperature change of the variable valve timing mechanism and oil pressure change according to RPM was made. Based on this model, a controller for position control of the variable valve timing mechanism was designed. The sliding mode control theory is applied to overcome unexpected disturbances.

FIG. 1 is a configuration diagram of a variable valve timing mechanism, and is shown in FIG. 2 as a free physical diagram for obtaining a mathematical model of the variable valve timing mechanism.

Referring to FIG. 1, the variable valve timing mechanism includes a variable valve mechanism 100, a cam shaft 105, a perceptual flow path 110, an advance path 115, and an oil control valve 120.

In addition, the variable valve mechanism 100 is disposed at one end of the cam shaft 105, and the advance passage 115 and the perceptual flow path are disposed between the variable valve mechanism 100 and the oil control valve 120. 110 is formed.

In addition, the variable valve mechanism 100 includes a rotor 125, a vane 130, a stator housing 135, and a stopper pin 150, and the crust chamber 140 may be disposed at both sides of the vane 130. The shell chamber 145 is formed.

The oil control valve 120 is controlled by the sliding mode controller 305, and the sliding mode controller 305 considers various variables such as oil pressure, oil temperature and battery voltage using a mathematical model.

Referring to FIG. 2, the oil control valve is mounted with a spool 200 for supplying oil to the perceptual chamber 140 or the advance chamber 145 while moving in accordance with a voltage applied from the sliding controller.

In the exemplary embodiment of the present invention, the sliding mode controller 305 detects the voltage of the battery from the battery sensor, detects the oil temperature from the temperature sensor, and detects the oil pressure according to the variation of the engine of the engine from the oil pressure sensor. do.

The mathematical model consists of three sub-models, an oil flow model supplied from the spool valve 200, a pressure model in the advance chamber 145 and the perceptual chamber 145, and a motion model of the rotor 125. This is it.

The oil flow model supplied from the spool valve 200 is obtained by using Orifice's law, Bernoulli's equation, and continuous equation.

과

은 부하유량과 부하압력이다

. 그 리고

는 유량계수,

는 스풀밸브의 출구 포트 폭 그리고

는 오일 밀도 이다.

and

Is the load flow rate and load pressure

. And

Is the flow coefficient,

Is the outlet port width of the spool valve and

Is the oil density.

는 상기 오일컨트롤밸브(120)에 인가되는 PWM 듀티와 비례관계로 실험을 통해 관계식을 구할 수 있다.Movement amount of the spool valve 200

The relational expression can be obtained through an experiment in a proportional relationship with the PWM duty applied to the oil control valve 120.

In addition, the pressure model in the advance chamber 145 and the perceptual chamber 140 is obtained as in Equation (2) using a continuous equation of two rooms.

은 상기 로터(125) 중심과 상기 베인(130)의 무게중심 사이의 거리이다.

는 상기 베인(130)의 각 위치 즉, 캠 위상이다.Where Vt is the total volume including the volume of the two seals 145 and 140 and the volume of the oil paths 110 and 115,

Is the distance between the center of the rotor 125 and the center of gravity of the vane 130.

Is the angular position of the vanes 130, i.e., the cam phase.

The motion model of the rotor 125 is obtained as in Equation (3) using the equation of motion for the force applied to the rotor 125.

는 상기 베인(130)을 포함하는 상기 로터(125)의 전체 질량이 고 b는 오일의 점성감쇠계수, k는 스프링상수 이다. 그리고

는 마찰력이다.here

Is the total mass of the rotor 125 including the vanes 130, b is the viscous damping coefficient of the oil, k is the spring constant. And

Is the frictional force.

By combining the three submodels above, the mathematical model of the variable valve timing mechanism is shown in Equation (4).

Where the variables and coefficients are

Based on this model, a sliding mode controller is designed to control the position of the variable valve timing mechanism.

는 상태 벡터,

는 제어입력,

는 외란, 그리고

는 시스템 계수 와 제어 게인 이며 오일 온도변화와 오일 압력변화에 대한 특성을 포함하고 있다. In equation (4)

State vector,

Is the control input,

Is disturbance, and

Are system coefficients and control gains, and include characteristics of oil temperature change and oil pressure change.

To quantify the model uncertainty and robustness against disturbances, Eq.

는 공칭값(nominal value)이며,

는 모델 불확실성에 대한 값이다. 그리고 D는 외란의 상한값이다. 이 값들은 다음과 같이 정한다.

Is the nominal value,

Is the value for model uncertainty. And D is the upper limit of disturbance. These values are determined as follows.

는 식 (6)과 같이 알고 있는 함수F에 상한값을 갖는다.Uncertainty about system coefficients

Has an upper limit on a known function F, as shown in equation (6).

는 하한값과 상한값 사이값으로 제한된다. Control gain

Is limited to a value between the lower limit and the upper limit.

Since model uncertainty and unknown disturbance are taken into account during the design stage of the controller, external environmental factors such as changes in the temperature of the system itself, oil pressure, and the effects of repulsive forces, friction factors, and battery voltages coming through the camshaft that are not included in the model It is robust against factors.

차이를 식 (7)과 같이 오차로 정의 하면 슬라이딩 s(t)=0 는 식 (8)과 같이 구해진다.Next, the following value of the variable valve timing mechanism

If the difference is defined as an error as in Eq. (7), the sliding s (t) = 0 is obtained as in Eq. (8).

는 양의 상수값을 선택한다.here

Selects a positive constant value.

Sliding condition is the same as (9).

는 양의 상수값을 선택한다.here

Selects a positive constant value.

When it develops from Formula (9), it is the same as Formula (10).

Through equations (9) and (10), the control input u is obtained as in equation (11).

Since the sign function of the control input can cause electrical or physical chattering, use the saturation function instead of the sign function.

Therefore, Formula (11) is represented by Formula (12) as follows.

3 is a configuration diagram applying the sliding controller obtained above to the variable valve timing system.

Referring to FIG. 3, the sliding controller 305 receives a target cam angle by a model reflecting a nonlinear characteristic and transmits a control input signal to the oil control valve 120 according to the target cam angle value.

In addition, the sliding controller 305 receives a rotational position (phase) signal of the cam from the cam position sensor and the crank position sensor.

As shown in the sliding mode controller design flowchart of FIG. 4, the influence of oil temperature and engine speed is reflected in the control by designing the controller based on a model of a variable valve timing mechanism including a nonlinear characteristic.

In addition, by quantifying the model uncertainty and robustness against unknown disturbances in the controller design process, it has robust advantages against disturbances such as changes in battery voltage and tolerance of components.

This design process takes about a week and requires only one operation for the same engine due to the robustness of the tolerances. Table 1 below shows the comparison between the PID-based controller and the sliding mode controller.

 Controller type  PID based controller  Sliding mode controller  calibration  Requires experimentation depending on oil temperature and engine speed  Included in the model.  Battery voltage disturbance  Create OCV Holding Duty Cycle Map for Battery Voltage  Included in the model and model uncertainty is taken into account during the controller design phase  Robustness against disturbance  Vulnerable to Unknown Disturbance  Robustness  Control performance -  Better control performance than PID  Robustness to Tolerance  Tolerances require calibration for each engine, or learning algorithm  Robustness Tolerance  Calibration time  About a month  About a week

FIG. 5 shows an experimental result when a target cam angle is input from 5 degrees to 45 degrees using a PID controller and a sliding mode controller (SMC). The results show that the sliding mode controller quickly reaches steady state.

6 shows the result when a Sine function input is given. Comparing the error with the PID controller, you can check the accuracy of the sliding mode controller.

7 and 8 show the robustness against disturbances.

7 is an experimental result when a battery voltage is input from 12 V to 14 V as a disturbance, and FIG. 8 is an experimental result when the battery voltage is swinged from 10 V to 14 V. FIG. The experimental results show the robustness of the sliding mode controller.

In addition, in the PID controller, as shown in FIGS. 7 and 8, the holding PWM duty of the OCV (oil control valve) varies according to the battery voltage, which adversely affects the control performance.

To overcome this problem, the PID controller needs to create and apply a map through experiments with battery voltage.

Therefore, the PID controller needs a calibration period of about one month due to the experiment, and has a problem in that calibration is performed for each engine due to an error. To overcome this, additional learning algorithm is needed.

In the sliding mode controller according to the exemplary embodiment of the present invention, since the consideration of disturbances such as battery voltage is included in the model, the calibration period is shortened because no separate map data is required.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and easily changed and equalized by those skilled in the art from the embodiments of the present invention. It includes all changes to the extent deemed acceptable.

1 is a configuration diagram of a variable valve timing mechanism.

2 is a free object diagram of the variable valve timing mechanism.

3 is a configuration diagram of a sliding mode controller.

4 is a design flowchart of the sliding mode controller.

5 is a graph showing the following results of the PID controller and the sliding mode controller for the step input from 4 degrees to 45 degrees.

6 is a graph showing the following results of a PID controller and a sliding mode controller for inputting a sine function.

FIG. 7 is a graph illustrating a tracking result of a PID controller and a sliding mode controller for battery voltage step input as disturbances.

FIG. 8 is a graph illustrating a tracking result of a PID controller and a sliding mode controller for battery voltage swing as disturbances.

9 is a design flowchart of the PID-based controller.

<Description of the symbols for the main parts of the drawings>

100: tectonic chamber

105: advance chamber

110: rotor

115: vane

120: stator

125: variable valve timing mechanism

130: camshaft

135: Acute Euro

140: Crust Euro

145: oil control valve

Claims (9)

A cam shaft having a cam formed thereon; Vanes mounted on one end of the camshaft; A stator mounted to the vane to form a crust chamber and a true chamber; An oil control valve for supplying oil to the crust chamber and the truth chamber; And A sliding mode controller controlling the oil control valve; Including, The sliding mode controller, And a variable valve timing mechanism for controlling oil supplied to the crust chamber and the true chamber by a sliding mode method by reflecting the temperature of the oil supplied to the oil control valve and the pressure change of the oil. According to claim 1, The sliding mode controller, A controller of a variable valve timing mechanism for controlling the oil control valve based on disturbance caused by a change in battery voltage. According to claim 1, The sliding control unit, A controller of a variable valve timing mechanism using an oil flow model of oil supplied from the oil control valve to the advance chamber and the perception chamber. The method of claim 3, wherein The oil flow model is represented by Equation (1)

The controller of the variable valve timing mechanism calculated by. The method of claim 3, wherein The sliding control unit, A controller of a variable valve timing mechanism using the pressure models in the advance chamber and the perception chamber. 6. The method of claim 5, The pressure model is equation (2)

The controller of the variable valve timing mechanism calculated by. The method of claim 3, wherein A vane and a rotor forming the chamber and the chamber, The sliding control unit is a controller of the variable valve timing mechanism using the motion model of the vane and the rotor. The method of claim 7, wherein The exercise model is equation (3).

The controller of the variable valve timing mechanism calculated by. According to claim 1, And a temperature sensor detecting a temperature of the oil and a pressure sensor detecting a pressure of the oil.

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