阅读说明：本技术 一种稳定自由活塞直线发电机上止点位置的控制方法 (Control method for stabilizing top dead center position of free piston linear generator ) 是由 唐娟 程勇 吕宏 马宗正 于 2019-09-20 设计创作，主要内容包括：本发明实施例公开了一种稳定自由活塞直线发电机上止点位置的控制方法,包括FPLG启动时,计算活塞运动到下一上止点位置需要的拖动力,通过控制输入电压满足所述拖动力要求；FPLG运行过程中,根据活塞运行的最大加速度,确定活塞在到达下一上止点位置时发电机的做功量,通过控制输入电压,满足发电机的做功需求。FPLG启动和运行过程中,分别预测在达到下一上止点时,电机需要的拖动力和需要做的功,通过控制输入电压,满足电机的做功需求,进而保证活塞能够顺利运行的下一个上止点,实现上止点的稳定,从而保证FPLG的稳定运行。(The embodiment of the invention discloses a control method for stabilizing the top dead center position of a free piston linear generator, which comprises the steps of calculating the dragging force required by the piston moving to the next top dead center position when an FPLG is started, and meeting the dragging force requirement by controlling the input voltage; in the FPLG operation process, the work amount of the generator when the piston reaches the next top dead center position is determined according to the maximum acceleration of the piston operation, and the work requirement of the generator is met by controlling the input voltage. In FPLG starts and the operation process, when predicting respectively reaching next top dead center, the work that the power and the work that need be done of dragging that the motor needs through control input voltage, satisfies the acting demand of motor, and then guarantees the next top dead center that the piston can move smoothly, realizes the stability of top dead center to guarantee FPLG's steady operation.)

1. A control method for stabilizing the top dead center position of a free piston linear generator is characterized by comprising the following steps:

when the FPLG is started, calculating the motor dragging force required by the piston moving to the next top dead center position, and meeting the dragging force requirement by controlling the input voltage;

in the FPLG operation process, the work amount of the motor when the piston reaches the next top dead center position is determined according to the maximum acceleration of the piston operation, and the work requirement of the generator is met by controlling the input voltage.

2. The method as claimed in claim 1, wherein the calculation of the drag force is specifically:

in the formula, p_{Press and press}F (x) is a function of the displacement x of the piston, a representing the force-receiving area of the piston, x_maxRepresenting half of the effective stroke of the piston.

3. The method as claimed in claim 2, wherein said method of controlling the top dead center position of the stable free piston linear generator by controlling the input voltage to meet said drag force requirement is as follows:

calculating the work of the motor moving to the next top dead center position under the action of the current dragging force according to the dragging force;

and determining the input voltage of the motor according to the work done when the motor moves to the next top dead center position, and controlling the input voltage to meet the work doing requirement.

4. The method as claimed in claim 1, wherein said maximum acceleration is calculated by:

respectively setting displacement acquisition points at the position and before and after the maximum acceleration, acquiring at least 3 displacements and corresponding time, and calculating the acceleration as the maximum acceleration, wherein the calculation formula of the maximum acceleration is as follows:

in the formula, S₁、t₁Indicating the first displacement measured and the corresponding time, S₂、t₂Indicating the second bit measuredShift and corresponding time, S₃、t₃Indicating the third displacement measured and the corresponding time.

5. The method as claimed in claim 4, wherein a displacement sensor is provided at said displacement collection point.

6. The method as claimed in claim 5, wherein the displacement sensor is a magnetic grid sensor, a magnetic grid ruler of the magnetic grid sensor is installed on a rotor shaft of the motor, and the magnetic head is fixedly installed on a casing of the FPLG.

7. The method as claimed in claim 4, wherein said determining the amount of work performed by the generator when the piston reaches the next top dead center position is selected from the group consisting of:

in the formula, x_maxIs half of the effective stroke of the piston, x₁For piston displacement at the ignition position, v₁Minimum speed, W, required at ignition position for piston to reach top dead center_fWork done for friction;

k_eqthe equivalent rigidity of the gas in the cylinder at the top dead center is expressed as follows:

wherein m is the mass of the piston moving member;

k₁the equivalent stiffness of the gas in the cylinder at the ignition position of the piston is expressed as:

in the formula, P_{Pressure max}D is the piston diameter for the in-cylinder pressure at the firing position.

8. The method as claimed in claim 4, wherein the specific process of meeting the work requirement of the generator by controlling the input voltage comprises:

judging the positive and negative of the work amount;

if the voltage is a non-negative value, the working requirement is met by controlling the input voltage of the generator;

if the voltage is a negative value, the generator is controlled to be converted into a motor state, and the driving force is generated by controlling the input voltage to meet the work-doing requirement.

Technical Field

The invention relates to the technical field of new energy automobile range extenders, in particular to a control method for stabilizing the top dead center position of a free piston linear generator.

Background

At present, the structures of common free-piston linear generators (FPLG) are mainly divided into three types, namely a single-piston type, an opposite double-piston type (short for opposite type) and a back-mounted double-piston type (short for back type). The single-piston type structure is simple and easy to control, but has the problem of unbalance and needs a return device; the opposite balance is good, but a synchronous mechanism and a return device are needed; the back-mounted type has higher energy density and higher thermal efficiency.

Compared with the traditional internal combustion engine, the FPLG reduces a crank link mechanism, so the structure is simple, the friction force is small, the heat efficiency is improved, and the application prospect is better, but the FPLG has the difficulty that the piston motion is difficult to control. PFLG mainly comprises two main components, an engine and an electric machine. In general, a motor in the FPLG provides power during starting, and is used as a motor to drag a piston to move, and after the motor reaches a specified position, the motor is switched from a motor mode to a generator mode, and electric energy is output. During operation, the movement of the piston in the FPLG depends on the combustion pressure in the engine cylinder, the electromagnetic force of the generator, and the friction force. Since the FPLG operation frequency is stabilized around a certain value, the magnitude of the friction force is substantially constant, and the piston movement is mainly determined by the combustion pressure and the generator electromagnetic force.

Free piston linear generator is at the operation in-process, if the in-cylinder burning situation is relatively poor, then probably lead to the unable electromagnetic resistance of overcoming of burning gas physical power, the piston can't reach the opposite side assigned position, and then leads to shutting down, causes FPLG operational stability poor.

Disclosure of Invention

The embodiment of the invention provides a control method for stabilizing the top dead center position of a free piston linear generator, and aims to solve the problem of poor operation stability of an FPLG (floating gate liquid Crystal) in the prior art.

In order to solve the technical problem, the embodiment of the invention discloses the following technical scheme:

the invention provides a control method for stabilizing the top dead center position of a free piston linear generator, which comprises the following steps:

when the FPLG is started, calculating the motor dragging force required by the piston moving to the next top dead center position, and meeting the dragging force requirement by controlling the input voltage;

in the FPLG operation process, the work amount of the motor when the piston reaches the next top dead center position is determined according to the maximum acceleration of the piston operation, and the work requirement of the generator is met by controlling the input voltage.

Further, the calculation of the dragging force is specifically as follows:

in the formula, p_{Press and press}= f (x) is a function of piston displacement x, a represents the force area of the piston, x_maxRepresenting half of the effective stroke of the piston.

Further, the meeting of the dragging force requirement by controlling the input voltage specifically comprises:

calculating the work of the motor moving to the next top dead center position under the action of the current dragging force according to the dragging force;

and determining the input voltage of the motor according to the work done when the motor moves to the next top dead center position, and controlling the input voltage to meet the work doing requirement.

Further, the calculation of the maximum acceleration is specifically:

respectively setting displacement acquisition points at the position and before and after the maximum acceleration, acquiring at least 3 displacements and corresponding time, and calculating the acceleration as the maximum acceleration, wherein the calculation formula of the maximum acceleration is as follows:

in the formula, S₁、t₁Indicating the first displacement measured and the corresponding time, S₂、t₂Representing the measured second displacement and the corresponding time, S₃、t₃Indicating the third displacement measured and the corresponding time.

Further, a displacement sensor is arranged at the displacement acquisition point.

Furthermore, the displacement sensor is a magnetic grid sensor, a magnetic grid ruler of the magnetic grid sensor is installed on a rotor shaft of the motor, and the magnetic head is fixedly arranged on a shell of the FPLG.

Further, the determining the work load of the generator when the piston reaches the next top dead center position is specifically as follows:

in the formula, x_maxIs half of the effective stroke of the piston, x₁For piston displacement at the ignition position, v₁Minimum speed, W, required at ignition position for piston to reach top dead center_fWork done for friction;

k_eqthe equivalent rigidity of the gas in the cylinder at the top dead center is expressed as follows:

wherein m is the mass of the piston moving member;

k₁the equivalent stiffness of the gas in the cylinder at the ignition position of the piston is expressed as:

in the formula, P_{Pressure max}D is the piston diameter for the in-cylinder pressure at the firing position.

Further, the specific process of meeting the work requirement of the generator by controlling the input voltage is as follows:

judging the positive and negative of the work amount;

if the voltage is a non-negative value, the working requirement is met by controlling the input voltage of the generator;

if the voltage is a negative value, the generator is controlled to be converted into a motor state, and the driving force is generated by controlling the input voltage to meet the work-doing requirement.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a schematic flow chart of a control method according to the present invention;

fig. 2 is a schematic diagram of the arrangement position of the displacement acquisition points of the invention.

Detailed Description

In order to clearly explain the technical features of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings. The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. It should be noted that the components illustrated in the figures are not necessarily drawn to scale. Descriptions of well-known components and processing techniques and procedures are omitted so as to not unnecessarily limit the invention.

The present invention is illustrated with a back-set FPLG. At present, engines are arranged at two ends of a motor mandrel in a back-mounted mode, two-stroke engines are generally symmetrically arranged in the middle of the motor mandrel, the motor has two functions of a motor and a generator, and due to combustion cycle change of the engine and response time of conversion between an electric mode and a power generation mode, the FPLG stably operates at present with great difficulty.

As shown in fig. 1, the method for controlling the top dead center position of the stable free piston linear generator according to the present invention comprises:

s1, when the FPLG is started, calculating the dragging force required by the piston moving to the next top dead center position, and meeting the dragging force requirement by controlling the input voltage;

and S2, determining the work amount of the generator when the piston reaches the next top dead center position according to the maximum acceleration of the piston in the operation process of the FPLG, and meeting the work requirement of the generator by controlling the input voltage.

In step S1, in the starting process, the motor serves as a motor to drag the piston to move to the top dead center position, and in order to ensure that the piston can move to the next top dead center position in the first working cycle, the needed drag force provided by the motor is:

(1) in the formula, p_{Press and press}F (x) is a function of the piston displacement x, p_{Press and press}Indicating in-cylinder pressure during compressionThe force being related to the piston displacement x, but at a certain engine timing, p_{Press and press}The functional relationship of f (x) can be determined; a represents the force bearing area of the piston and is a constant; x is the number of_maxRepresents half of the effective stroke of the piston and is constant.

According to the dragging force F calculated by the formula (1), the work W which is done when the piston moves to the next top dead center position under the action of the current dragging force is obtained by integrating the movement displacement of the piston, the work W is UIt according to the formula W, and the work efficiency when the motor is used as a motor is combined, under the condition of determining the time t, the requirement of the dragging force is met by controlling the input voltage, so that the stable starting of the FPLG is ensured.

In the starting process, whether the piston reaches the ignition position or not is determined, a displacement acquisition point 1 is arranged in front of the ignition position of the engine, the displacement acquisition point 1 can be arranged 1mm in front of the ignition position, and only the situation that the piston can complete signal transmission and control from the sensor position to the ignition position is ensured. Once the engine controller issues an ignition command, the engine can achieve ignition combustion.

In step S2, during the post-ignition FPLG operation, the maximum acceleration of the piston operation is determined. The position of the piston reaching the maximum acceleration can be obtained through measurement or simulation, two displacement acquisition points, namely a displacement acquisition point 1, a displacement acquisition point 2 and a displacement acquisition point 3 shown in fig. 2, are arranged at the position of the maximum acceleration and 1mm in front of and behind the position, 3 displacement acquisition points are arranged in total, the time of the piston passing through the three displacement acquisition points is respectively acquired, and the maximum acceleration of the piston motion is calculated as follows:

(2) in the formula, S₁、t₁Representing the first displacement measured at the first displacement acquisition point 1 and the corresponding time, S₂、t₂Representing the second displacement measured at the displacement acquisition point 2 and the corresponding time, S₃、t₃Representing the third displacement measured by the displacement acquisition point 3 and the corresponding time.

Wherein displacement sensor can be arranged respectively to displacement acquisition department and carry out the collection of displacement data, 3 single-point displacement sensors need to be arranged, also can arrange 1 magnetic grid sensor, and the magnetic grid chi of magnetic grid sensor is installed on the active cell axle, and the magnetic head is fixed on the casing, and the active cell drives the magnetic grid chi and removes, and the magnetic head reads magnetic grid position signal and sends for the controller to the controller realizes giving the accurate control of active cell position. In order to obtain a more accurate maximum acceleration value, a plurality of displacement acquisition points may be set.

The work load of the generator when the piston reaches the next top dead center position is determined as follows:

(3) in the formula, x_maxIs half of the effective stroke of the piston and is a constant; x is the number of₁Is the piston displacement at the ignition position, constant; v. of₁The minimum speed required at the ignition position when the piston can reach the top dead center can be obtained through experiments or simulation and is a constant; w_fThe work done by friction can be measured by simulation or experiment and is constant;

k_eqthe equivalent rigidity of the gas in the cylinder at the top dead center is expressed as follows:

(4) wherein m is the mass of the piston moving part and is a constant;

k₁the equivalent stiffness of the gas in the cylinder at the ignition position of the piston is expressed as:

(5) in the formula, P_{Pressure max}The in-cylinder pressure at the ignition position can be measured through experiments or simulation and is a constant; d is the piston diameter and is a constant.

Based on the above equations (3) - (5), it can be seen that it is established that the piston reaches the next timeRelation between work load of generator and maximum acceleration at top dead center position, calculated maximum acceleration a_maxThen, the corresponding work load W can be obtained_eAccording to the relation between the work-doing amount and the input voltage and the work efficiency, the work-doing amount W can be satisfied by controlling the input voltage_eThe requirements of (1).

Obtaining W according to the formula (3)_eThen, first, W is judged_ePositive or negative of (1), if W_eIf the piston is not negative, the work load is adjusted by controlling the voltage change of the generator, and the piston can smoothly reach the designated position and sequentially circulate. When W is_eIf the value of (A) is negative, the generator is controlled to be switched to the motor state and W is output_eThe corresponding output voltage generates driving force, the auxiliary piston reaches a designated position, and the combustion expansion of the next cycle is carried out according to W_eDetermines whether the motor is convertible into a generator and outputs electrical energy. And by analogy, the stable operation of the free piston linear generator is realized.

For a back-mounted FPLG, the engine burns twice per cycle, 2 acceleration peaks occur during piston reciprocation, and the generator input voltage is regulated twice per cycle. For single piston type FPLG and opposed type FPLG, the stable operation of the FPLG can be achieved by adopting the mode.

The foregoing is only a preferred embodiment of the present invention, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the invention, and such modifications and improvements are also considered to be within the scope of the invention.