阅读说明：本技术 基于dmc算法的自由活塞直线发电机控制系统及控制方法 (Free piston linear generator control system and control method based on DMC algorithm ) 是由 程勇 马宗正 唐娟 吕宏 于 2019-09-30 设计创作，主要内容包括：本发明实施例公开了一种基于DMC算法的自由活塞直线发电机控制系统及控制方法,基于控制系统,控制方法包括获取活塞的运动状态信息；根据所述运动状态信息,计算活塞运动到下一上止点所需的电机做功量；根据做功量,得到电机动子内电流与时间的关系,基于电流变化规律,应用MDC算法计算所需电压,并将该电压施加于电机。通过DMC算法,将电机动子线圈内电流随输入电压的响应值作为预测模型,将输入电压作为控制增量,定子电流作为输出预测,搭建自由活塞直线发电机的电机做功量的控制模型,使电机在控制模块的作用下快速、准确的输出所需功率,实现输入电压的准确控制,保证自由活塞直线发电机的稳定运行。(The embodiment of the invention discloses a free piston linear generator control system and a control method based on a DMC algorithm, wherein the control method comprises the steps of acquiring motion state information of a piston based on the control system; calculating the work done by the motor required by the piston moving to the next upper dead point according to the motion state information; and obtaining the relation between the current in the motor rotor and the time according to the work done, calculating the required voltage by applying an MDC algorithm based on the current change rule, and applying the voltage to the motor. By means of the DMC algorithm, a response value of current in a motor rotor coil along with input voltage is used as a prediction model, the input voltage is used as a control increment, stator current is used as output prediction, and a control model of the motor work capacity of the free piston linear generator is built, so that the motor can rapidly and accurately output required power under the action of the control module, the accurate control of the input voltage is realized, and the stable operation of the free piston linear generator is guaranteed.)

1. A free piston linear generator control system based on a DMC algorithm comprises a free piston linear generator and is characterized by further comprising a control module, wherein the control module comprises an information acquisition unit, an information processing unit and an output control unit, and the information acquisition unit is used for acquiring motion state information of a piston and sending the motion state information to the information processing unit; the information processing unit calculates the work done by the motor required by the piston to move to the next top dead center based on the motion state information; and the output control unit obtains the relation between the current in the motor rotor and the time according to the work amount, calculates the required voltage by applying a DMC algorithm based on a current change rule, and applies the required voltage to the motor.

2. The DMC algorithm based free-piston linear generator control system of claim 1, wherein the information processing unit comprises a microcontroller ECU.

3. The DMC algorithm-based free-piston linear generator control system of claim 1, wherein the output control unit comprises a current prediction model building subunit, a performance roll optimization subunit, and a feedback optimization subunit;

the current prediction model establishing subunit is used for establishing a prediction model of the current, and comprises a modeling time domain, an optimization time domain and a control time domain, wherein voltage increment from the sampling time is added to the motor at each time in the control time domain, so that the current output prediction value in the future optimization time domain is close to an expected value;

the performance rolling optimization subunit is used for selecting an optimized performance index, obtaining a control increment sequence corresponding to the minimum value of the optimized performance index, and taking a first component in the control increment sequence as a voltage increment of the current moment;

the feedback optimization subunit is used for calculating a prediction error formed by the actual response current under the action of the current voltage increment and the prediction model, calculating a prediction output after error correction, and performing new prediction optimization at the next moment.

4. A free piston linear generator control method based on DMC algorithm, based on the control system of any of claims 1-3, characterized in that the method comprises the steps of:

s1, acquiring the motion state information of the piston;

s2, calculating the work amount of the motor required by the piston to move to the next top dead center according to the motion state information;

and S3, obtaining the relation between the current in the motor rotor and the time according to the work amount, calculating the required voltage by applying a DMC algorithm based on the current change rule, and applying the voltage to the motor.

5. The DMC algorithm-based free-piston linear generator control method according to claim 4, wherein the step S3 is implemented as follows:

establishing a prediction model of the current, which comprises determining a modeling time domain, an optimization time domain and a control time domain, and adding a voltage increment from a sampling time to the motor at each time in the control time domain to enable a current output prediction value in the future optimization time domain to be close to an expected value;

selecting an optimized performance index to obtain a control increment sequence corresponding to the minimum value of the optimized performance index, and taking a first component in the control increment sequence as a voltage increment of the current moment;

and calculating a prediction error formed by the actual response current under the action of the current voltage increment and the prediction model, calculating a prediction output after error correction, and performing new prediction optimization at the next moment.

6. The DMC algorithm-based free-piston linear generator control method of claim 5, wherein the optimized performance indicators are:

in the formula (I), the compound is shown in the specification,

for the increment of the voltage for M time instants,

q, R are the error weight matrix and the control weight matrix, respectively.

7. The DMC algorithm-based free-piston linear generator control method of claim 6, wherein the control increment sequence when the optimization performance indicator takes a minimum value is:

wherein, A is a dynamic matrix,

and (4) system output of P times in the future without voltage increment predicted for the time t-kT.

8. The DMC algorithm-based free-piston linear generator control method of claim 7, wherein the prediction error is:

where y (k +1) is the actual response current at time k +1,

weighting and correcting the predicted value by the prediction error to obtain a corrected predicted value

In the formula (I), the compound is shown in the specification,

will be provided with

Wherein S is a matrix.

Technical Field

The invention relates to the technical field of power control, in particular to a free piston linear generator control system and a control method based on a DMC algorithm.

Background

The free piston internal combustion linear generator is a novel energy conversion device formed by coupling a free piston type internal combustion engine and a linear generator, has higher thermal efficiency than a traditional engine, and can play a remarkable role in energy conservation, emission reduction and environmental pressure relief. The free piston linear generator mainly comprises two main components, namely an engine and a generator, and when the free piston linear generator is started, the generator serves as a motor to drag a piston to move to an upper dead point so as to finish a first cycle process; when the linear generator normally operates, the linear generator rapidly moves under the pushing of the piston of the internal combustion engine, and chemical energy of fuel is converted into electric energy for external use.

The generator in the free piston linear generator provides power during starting, the generator serves as a motor to drag the piston to move, the internal combustion engine is ignited to start when the piston speed reaches a target value and the piston dead center is at a set position, and then the linear generator is pushed by the piston of the internal combustion engine to move rapidly to be converted into a generator model. When the combustion condition of the internal combustion engine is poor or a fire occurs, the dead point of the piston cannot reach the set position, so that the compression ratio of the engine and the combustion condition of the next cycle are influenced, the vicious cycle can cause the shutdown, and the advantages of the free piston linear generator cannot be exerted.

The patent application with application number 2019108944998 proposes to add an auxiliary motor on the basis of the existing free piston linear generator, and realizes the stability of the upper dead point by controlling the input voltage of the auxiliary motor. The patent application No. 2019108945115 proposes to control the input voltage of the motor of the conventional free piston linear generator to achieve top dead center stabilization. The two patent applications achieve the purpose of stable operation of the free piston linear generator by controlling input voltage, but the control of voltage in actual operation is a technical difficulty.

Disclosure of Invention

The embodiment of the invention provides a control system and a control method of a free piston linear generator based on a DMC algorithm, and aims to solve the problem that the free piston linear generator is difficult to realize by controlling input voltage.

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

the invention provides a free piston linear generator control system based on a DMC algorithm, which comprises a free piston linear generator and a control module, wherein the control module comprises an information acquisition unit, an information processing unit and an output control unit, and the information acquisition unit is used for acquiring motion state information of a piston and sending the motion state information to the information processing unit; the information processing unit calculates the work done by the motor required by the piston to move to the next top dead center based on the motion state information; and the output control unit obtains the relation between the current in the motor rotor and the time according to the work amount, calculates the required voltage by applying a DMC algorithm based on a current change rule, and applies the required voltage to the motor.

Further, the information processing unit includes a microcontroller ECU.

Further, the output control unit comprises a current prediction model establishing subunit, a performance rolling optimization subunit and a feedback optimization subunit;

the current prediction model establishing subunit is used for establishing a prediction model of the current, and comprises a modeling time domain, an optimization time domain and a control time domain, wherein voltage increment from the sampling time is added to the motor at each time in the control time domain, so that the current output prediction value in the future optimization time domain is close to an expected value;

the performance rolling optimization subunit is used for selecting an optimized performance index, obtaining a control increment sequence corresponding to the minimum value of the optimized performance index, and taking a first component in the control increment sequence as a voltage increment of the current moment;

the feedback optimization subunit is used for calculating a prediction error formed by the actual response current under the action of the current voltage increment and the prediction model, calculating a prediction output after error correction, and performing new prediction optimization at the next moment.

The invention provides a free piston linear generator control method based on a DMC algorithm, based on the control system, the method comprises the following steps:

s1, acquiring the motion state information of the piston;

s2, calculating the work amount of the motor required by the piston to move to the next top dead center according to the motion state information;

and S3, obtaining the relation between the current in the motor rotor and the time according to the work amount, calculating the required voltage by applying a DMC algorithm based on the current change rule, and applying the voltage to the motor.

Further, the specific implementation process of step S3 is as follows:

establishing a prediction model of the current, which comprises determining a modeling time domain, an optimization time domain and a control time domain, and adding a voltage increment from a sampling time to the motor at each time in the control time domain to enable a current output prediction value in the future optimization time domain to be close to an expected value;

selecting an optimized performance index to obtain a control increment sequence corresponding to the minimum value of the optimized performance index, and taking a first component in the control increment sequence as a voltage increment of the current moment;

and calculating a prediction error formed by the actual response current under the action of the current voltage increment and the prediction model, calculating a prediction output after error correction, and performing new prediction optimization at the next moment.

Further, the optimized performance index is as follows:

in the formula (I), the compound is shown in the specification,

for the desired value of the response current at P moments in the future,

for the corresponding current output values at P moments in the future,

for the increment of the voltage for M time instants,

q, R are the error weight matrix and the control weight matrix, respectively.

Further, the control increment sequence when the optimization performance index takes the minimum value is as follows:

wherein, A is a dynamic matrix,

and (4) system output of P times in the future without voltage increment predicted for the time t-kT.

Further, the prediction error is:

where y (k +1) is the actual response current at time k +1,

the current is a predicted value;

weighting and correcting the predicted value by the prediction error to obtain a corrected predicted value

In the formula (I), the compound is shown in the specification,

for the output of the prediction vector after correction,

will be provided with

Shift processing is carried out to obtain an initial prediction sequence at the time T ═ k +1) T

Wherein S is a matrix.

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 diagram of the control system of the present invention;

fig. 2 is a flow chart of the control method of the present 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.

As shown in figure 1, the free piston linear generator control system based on the DMC algorithm comprises a free piston linear generator and a control module, wherein the free piston linear generator and the control module are interconnected for information transmission.

Free piston linear generators in embodiments of the present invention include those set forth in patent applications No. 201910896735X, No. 2019108967326, No. 2019108966747, No. 2019108967330, and No. 2019108966732.

The control module comprises an information acquisition unit, an information processing unit and an output control unit. The information acquisition unit is used for acquiring the motion state information of the piston and sending the motion state information to the information processing unit; the information acquisition unit comprises a displacement sensor, and the displacement sensor is arranged near the maximum speed or the maximum acceleration reached by the movement of the piston. And the displacement sensor sends the collected displacement data and the corresponding time to the information processing unit.

The information processing unit comprises a microcontroller ECU (electronic Control Unit), and the ECU calculates the work done by the motor when the piston moves to the next upper dead point based on the motion state information; the output control unit obtains the relation between the current in the motor rotor and the time according to the work amount, calculates the required voltage by applying a DMC algorithm based on the current change rule, and applies the required voltage to the motor.

The output control unit comprises a current prediction model establishing subunit, a performance rolling optimization subunit and a feedback optimization subunit, and is used for respectively realizing model establishment, rolling optimization and feedback correction in a DMC algorithm.

The current prediction model establishing subunit is used for establishing a prediction model of the current, and comprises a modeling time domain, an optimization time domain and a control time domain, wherein voltage increment from the sampling time is added to the motor at each time in the control time domain, so that the current output prediction value in the future optimization time domain is close to an expected value;

the performance rolling optimization subunit is used for selecting an optimized performance index, obtaining a control increment sequence corresponding to the minimum value of the optimized performance index, and taking a first component in the control increment sequence as a voltage increment of the current moment;

the feedback optimization subunit is used for calculating a prediction error formed by the actual response current under the action of the current voltage increment and the prediction model, calculating a prediction output after error correction, and performing new prediction optimization at the next moment.

As shown in fig. 2, the free piston linear generator control method based on DMC algorithm of the present invention comprises:

s1, acquiring the motion state information of the piston;

s2, calculating the work amount of the motor required by the piston to move to the next top dead center according to the motion state information;

and S3, obtaining the relation between the current in the motor rotor and the time according to the work amount, calculating the required voltage by applying a DMC algorithm based on the current change rule, and applying the voltage to the motor.

The steps S1-S3 correspond to the units of the control module, and the specific implementation processes of the steps S1 and S2 are not described again.

The implementation process of step S3 corresponds to each subunit of the output control unit, and the specific process of applying the DMC algorithm is as follows:

and when the motor parameters are determined, the motor driving force F only depends on the magnitude of the motor current, the motor is abstracted into a simple R-L circuit, and the motor current and the voltage form a linear relation, so that the DMC control model is determined.

The specific process of establishing the model is as follows:

measuring the sampled value of the unit step response of the current in the linear motor to the input voltage according to the selected period T:

a_k＝a(kT),k＝1,2,……N (1)

(1) in the formula, N is the model time domain length, and constitutes a model vector:

setting a control time domain as M, an optimized time domain as P, and sequentially adding M voltage increments delta u (k) from the sampling time t to kT, wherein the delta u (k +1) … … delta u (k + M-1) is sequentially added to the motor at the time k, k +1 … … k + M-1, so that the predicted current output value at the time P in the future is

As close as possible to the desired current values ω (k +1), … … ω (k + P).

The specific process of the rolling optimization is as follows:

selecting the optimized performance indexes as follows:

(3) in the formula (I), the compound is shown in the specification,

for the desired value of the response current at P moments in the future,

for the corresponding current output values at P moments in the future,

for the increment of the voltage for M time instants,

Q＝diag(q₁,…，q_P) Is an error weight matrix, R ═ diag (R)₁,…，r_M) And is a control weight matrix.

(3) The first term in the formula is the voltage increment delta u (k), …, delta u (k + M-1) at M moments from the selection moment, so that the system can make P (N ≧ P ≧ in the futureM) output values at time points

As close as possible to its desired value ω (k +1), … ω (k + P). (3) The second term of the equation is a constraint on the control increment, i.e., the change in the control amount is not allowed to be too severe.

The optimization horizon moves forward continuously over time. Δ u to minimize J (k)_M(k) Passing extreme value requirement

Determining a sequence of control increments Deltau which minimizes the optimization of the performance index J (k)_M(k) Comprises the following steps:

(4) in the formula (I), the compound is shown in the specification,

for a sequence of M control increments from time k,

in the form of a dynamic matrix, the matrix is,

and (4) system output at P times in the future without voltage control increment predicted for the time t-kT.

Selection of Δ u_M(k) The first component Δ u (K) is used as the control increment at time K, which is the optimal solution for the open loop of voltage based on the prediction model.

Because uncertain factors exist in the motion process of the rotor assembly and the actual work doing process of the motor, the open-loop control law of the prediction model does not necessarily enable the output current to closely follow the expected current, meanwhile, the disturbance of the current is also considered, in order to correct the inconsistency of the model prediction and the actual model, the output prediction value needs to be corrected by utilizing error information of the process in time, and the M control increments are not corrected after being implemented.

The specific process of feedback correction is as follows:

by the next sampling time T ═ k +1) T, the actual corresponding current y (k +1) of the system is compared with the current prediction output by the model prediction at that time

The difference of (a) constitutes a prediction error:

weighting and correcting the predicted value by the prediction error in the formula (5) to obtain a corrected predicted value

(6) In (1),

predicting a vector for the corrected output

To correct the vector, where h₁＝1。

To obtain an initial prediction sequence at time T ═ T (k +1) T

Will be provided with

Performing shift processing, namely:

(7) the method comprises the following steps:

in order to shift the matrix, the matrix is shifted,

if, over time, the time base is now repositioned, i.e. the time T is redefined to be (k +1) T, then the current prediction sequence is carried out at (k +1) T

Becomes a current prediction sequence at moment kT

Thus, the current predicts the initial value

The first P components of

Will output ω with the current desired_p(k) Together, participate in the calculation of the control voltage increment at the new moment, so circulate, this process will go on line repeatedly, make the actual motor current closely follow the desired electric current size, reach the effect of quick, stable control motor output.

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.