Track-based free piston type internal combustion power generation system motion control method, device and equipment and medium

Abstract

The invention discloses a free piston type internal combustion power generation system motion control method and device based on a track, equipment and a medium, and relates to the field of free piston type internal combustion power generation systems.The method comprises the steps that the operation state of a free piston type internal combustion power generation system is determined according to operation parameters of the free piston type internal combustion power generation system; determining reference trajectories of the free piston type internal combustion power generation system in different operation states; a double-loop motion control structure is adopted to track the reference track, and a reference voltage vector is determined; and the reference voltage vector is modulated into a duty ratio signal through a space vector pulse width modulation algorithm, and the free piston type internal combustion power generation system is controlled to move. According to the invention, the track of the piston can be controlled, and the stability of the FPLG system is improved.

Description

Technical Field

[0001] The present application relates to the field of free piston internal combustion power generation systems, and particularly to a motion control method, device, equipment and medium for a free piston internal combustion power generation system based on trajectory. Background Art

[0002] Seeking cleaner and more efficient energy utilization methods is of great significance. As a new type of energy utilization device, the free piston internal combustion power generation system (FPLG) has the advantages of variable compression ratio, multiple fuel usability, high indicated efficiency, and low combustion emissions, and will become a new generation of automotive power devices, mobile power sources, and power generation equipment. However, since the piston movement in the FPLG system is no longer restricted by the crank connecting rod mechanism, it poses challenges to the control of the FPLG system.

[0003] Currently, the control of the FPLG system mainly focuses on the control of the top dead center and bottom dead center. However, such control cannot fully utilize the advantages brought by the completely free piston movement of the FPLG system. Summary of the Invention

[0004] The purpose of the present application is to provide a motion control method, device, equipment and medium for a free piston internal combustion power generation system based on trajectory, which can realize the control of the piston trajectory and improve the stability of the FPLG system.

[0005] To achieve the above purpose, the present application provides the following solutions:

[0006] In the first aspect, the present application provides a motion control method for a free piston internal combustion power generation system based on trajectory, including:

[0007] Determine the operating state of the free piston internal combustion power generation system according to the operating parameters of the free piston internal combustion power generation system;

[0008] Determine the reference trajectory of the free piston internal combustion power generation system in different operating states;

[0009] Adopt a double-loop motion control structure to track the reference trajectory and determine the reference voltage vector;

[0010] Modulate the reference voltage vector into a duty cycle signal through a space vector pulse width modulation algorithm to control the movement of the free piston internal combustion power generation system.

[0011] In the second aspect, the present application provides a motion control device for a free piston internal combustion power generation system based on trajectory, including:

[0012] An operating state determination module, configured to determine the operating state of the free piston internal combustion power generation system according to the operating parameters of the free piston internal combustion power generation system;

[0013] A reference trajectory determination module for determining the reference trajectories of the free piston internal combustion power generation system in different operating states;

[0014] A reference voltage vector determination module for tracking the reference trajectory using a double-loop motion control structure to determine the reference voltage vector;

[0015] A motion control module for modulating the reference voltage vector into a duty cycle signal through a space vector pulse width modulation algorithm to control the motion of the free piston internal combustion power generation system.

[0016] In a third aspect, the present application provides a computer device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, where the processor executes the computer program to implement the above-mentioned trajectory-based motion control method for a free piston internal combustion power generation system.

[0017] In a fourth aspect, the present application provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the above-mentioned trajectory-based motion control method for a free piston internal combustion power generation system.

[0018] In a fifth aspect, the present application provides a computer program product, including a computer program, and when the computer program is executed by a processor, it implements the above-mentioned trajectory-based motion control method for a free piston internal combustion power generation system.

[0019] According to the specific embodiments provided by the present application, the present application has the following technical effects:

[0020] The present application provides a trajectory-based motion control method, device, equipment, and medium for a free piston internal combustion power generation system. By determining the reference trajectories of the FPLG system in different operating states and using a double-loop motion control structure to track the reference trajectories, the FPLG system can complete smooth switching between various operating states and full-process trajectory tracking, ensuring the long-term stable operation of the FPLG system. And compared with the traditional PID control method, the double-loop motion control structure can significantly improve the responsiveness of the FPLG system and reduce the control error. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1Schematic flowchart of a motion control method for a trajectory-based free piston internal combustion power generation system provided by an embodiment of the present application;

[0023] Figure 2 Schematic flowchart of the optimization of the reference trajectory in the combustion state;

[0024] Figure 3 Schematic diagram of tracking the reference trajectory using a double-loop motion control structure;

[0025] Figure 4 Schematic diagram of the effect of the reference trajectory;

[0026] Figure 5 Schematic diagram of the tracking effect of the reference trajectory in different motion states during cold start experiments;

[0027] Figure 6 Schematic diagram of the structure of a computer device provided by an embodiment of the present application. Detailed implementation manners

[0028] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0029] A control scheme focusing on the complete piston trajectory can bring stronger control effects to the FPLG system, and also has a stronger ability to adjust combustion, providing a basis for freely editing the piston trajectory of the FPLG system. Therefore, for the control of the FPLG system, the research on trajectory-based control will open up a new direction for it. The present application proposes a motion control strategy for a trajectory-based free piston internal combustion power generation system, which realizes the control of the piston trajectory by coordinating various forces in the full-cycle operation process of the FPLG system, and improves the stability of the FPLG system.

[0030] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0031] In an exemplary embodiment, as Figure 1 shown, a motion control method for a trajectory-based free piston internal combustion power generation system is provided. This method is executed by a computer device, and specifically can be executed independently by a computer device such as a terminal or a server, or jointly executed by a terminal and a server. In the embodiments of the present application, taking the application of this method to a server as an example for illustration, it includes the following steps S1 to S4. Among them:

[0032] S1: Determine the operating state of the free piston internal combustion power generation system according to the operating parameters of the free piston internal combustion power generation system.

[0033] Specifically, determine the operating state (starting, transition, combustion, and shutdown) of the FPLG system according to the actual operating parameters (cylinder pressure p, piston displacement x, and piston velocity v) of the FPLG system.

[0034] (1) Starting state: When the linear motor in the free piston internal combustion power generation system starts to operate, and there is no fuel injection and ignition in the engine or misfire occurs (p max < 18 bar), the free piston internal combustion power generation system enters the starting state when the piston displacement reaches the top dead center (x = x TDC ) during the compression stroke (v ≤ 0). p max is the maximum cylinder pressure, and x TDC is the top dead center position.

[0035] (2) Transition state: When fuel injection and ignition start in the engine but the combustion is not complete (20 bar < p max < 35 bar) or the combustion state is poor (18 bar < p max < 30 bar), the free piston internal combustion power generation system enters the transition state when the piston displacement reaches the top dead center during the compression stroke.

[0036] (3) Combustion state: When the engine is completely combusted (p max > 35 bar), the free piston internal combustion power generation system enters the combustion state when the piston displacement reaches the top dead center during the compression stroke.

[0037] (4) Shutdown state: When the free piston internal combustion power generation system receives a shutdown command, the free piston internal combustion power generation system enters the shutdown state when the piston displacement reaches the bottom dead center (x = x BDC ) during the expansion stroke (v ≥ 0). x BDC is the bottom dead center position.

[0038] S2: Determine the reference trajectories of the free piston internal combustion power generation system in different operating states.

[0039] Specifically, determine that the reference trajectories in the starting state, combustion state, and shutdown state are sine-symmetric trajectories; determine that the reference trajectory in the combustion state is an asymmetric high-order polynomial trajectory.

[0040] In a specific example, the reference trajectory in the starting state is a sinusoidal symmetric trajectory with an amplitude of 60 mm and a frequency of 6 Hz; the reference trajectory in the transition state is a sinusoidal symmetric trajectory with an amplitude of 90 mm and a frequency of 8 Hz; the reference trajectory in the combustion state is an asymmetric high-order polynomial trajectory; the reference trajectory in the shutdown state is a sinusoidal symmetric trajectory with an amplitude of 90*e(-5t) mm and a frequency of 8 Hz.

[0041] Among them, Figure 2 As shown, the reference trajectory in the combustion state is optimized using the genetic algorithm (GA). The compression stroke and the expansion stroke respectively adopt a seventh-order polynomial trajectory and a sixth-order polynomial trajectory, and the polynomial trajectory parameters a 0 、a 1 、a 2 …a n etc. are used to parameterize the reference trajectory, and these optimization parameters are binary-encoded. At the beginning of the optimized trajectory, a set of optimization parameters is randomly generated and the numerical values are converted into binary strings for initialization. According to the initialized piston trajectory parameters, a series of piston trajectories are generated. First, it is judged whether the trajectory is reasonable. If the piston displacement exceeds the top dead center (x < x TDC ) and the bottom dead center (x > x BDC ), or the piston speed is greater than zero in the compression stroke or less than zero in the expansion stroke, the trajectory is unreasonable, and the system efficiency of this trajectory is set to zero.

[0042] x = a 0 +a 1 t+a 2 t 2 +...+a n t n

[0043] When the piston trajectory is judged to be reasonable, the system efficiency under this trajectory will be calculated and optimized using the genetic algorithm. According to the system efficiency, this set of piston trajectory parameters is sorted. The top 1 / 4 with high system efficiency is copied and replaces the bottom 1 / 4 with low system efficiency. Subsequently, the binary codes of different piston trajectory parameters are exchanged and the binary codes of the piston trajectory parameters are randomly changed probabilistically, so as to generate a series of new piston trajectory parameters for the next iterative calculation. When the stop rule is satisfied, that is, when the increase in system efficiency is within 0.01%, the trajectory optimization is completed, and the piston trajectory parameters corresponding to the optimal system efficiency are the optimized combustion reference trajectory.

[0044] The calculation formula for the system efficiency is:

[0045]

[0046] Among them, e q is the q-axis back electromotive force, i d, i q are the d-axis and q-axis currents, and R s is the motor resistance, and Q fuel is the fuel calorific value.

[0047] S3: Adopt a double-loop motion control structure to track the reference trajectory and determine the reference voltage vector.

[0048] As Figure 3 shown, in the double-loop motion control structure of this application, the outer loop uses a sliding mode controller (SMC) to output the reference current according to the reference trajectory and the actual operation trajectory, and the inner loop uses a PI controller to output the reference voltage vector according to the reference current and the actual current.

[0049] In the outer loop, calculate the reference current according to the reference trajectory determined in step S2 and the actual operation trajectory of the FPLG system and output it to the inner loop. Among them, in order to ensure that the FPLG system operates at a unity power factor, the d-axis reference current output is zero. Among them, the control law of the q-axis reference current i q * is:

[0050]

[0051] where g(x) is the control constant, f(x) is the system constant; x is the actual piston displacement, and x ref is the piston reference displacement; c 1 , c 2、 α 1 , α 2 are the sliding mode surface parameters, all of which are positive constants, and α 1 > 1; q and K are the reaching law parameters and are positive constants, S = 0 is the sliding mode surface; m is the piston mass, n is the combustion pressure; F s is the scavenging pump gas pressure, F sp is the spring force, F f is the friction force, n > mF c ; τ is the motor pole pitch, and Ψ f is the motor magnetic flux; a and b are positive odd numbers, a > b, and δ is the switching value; e = x ref -x, which is the displacement error.

[0052] In the inner loop, output the reference voltage vectors V d and V q according to the reference current output by the outer loop and the actual current, and adopt a PI controller combined with feedforward decoupling control, and its control law is:

[0053]

[0054] where K p , K Iare the proportional gain and integral gain of the current inner-loop PI controller; i d * and q * are the d-axis reference current and q-axis reference current; ω is the electrical angular velocity of the linear motor; L d and L q are the d-axis inductance and q-axis inductance; e d and e q are the d-axis displacement error and q-axis displacement error.

[0055] S4: Modulate the reference voltage vector into a duty cycle signal through the space vector pulse width (SVPWM) modulation algorithm to control the movement of the free piston internal combustion power generation system.

[0056] Specifically, the reference voltage vector output in step S3 will be modulated by SVPWM into the duty cycle signals of six IGBT switches to control the FPLG system.

[0057] To further verify the effectiveness of the trajectory-based motion control method for the free piston internal combustion power generation system provided in this application, this application applies the dual-loop motion control structure to an actual FPLG prototype to study the actual performance of the dual-loop motion control structure, such as Figure 4 shown, and it is found that the method provided in this application has excellent response speed and stability, and the tracking error is within 4 mm.

[0058] Using the method provided in this application, the FPLG system can complete smooth switching under different operating states, complete the full-process trajectory tracking of the FPLG system, and the tracking of asymmetric combustion reference trajectories, such as Figure 5 shown.

[0059] Based on the same inventive concept, the embodiments of this application also provide an apparatus for implementing the above-mentioned trajectory-based motion control method for the free piston internal combustion power generation system. The solution provided by this system to solve the problem is similar to the solution described in the above method. Therefore, the specific limitations in one or more embodiments of the following trajectory-based motion control apparatus for the free piston internal combustion power generation system can refer to the limitations for the trajectory-based motion control method for the free piston internal combustion power generation system in the above text, and will not be repeated here.

[0060] In an exemplary embodiment, a trajectory-based motion control apparatus for a free piston internal combustion power generation system is provided, including:

[0061] An operating state determination module, configured to determine the operating state of the free piston internal combustion power generation system according to the operating parameters of the free piston internal combustion power generation system.

[0062] A reference trajectory determination module, configured to determine the reference trajectories of the free piston internal combustion power generation system in different operating states.

[0063] A reference voltage vector determination module, configured to track the reference trajectory by adopting a double-loop motion control structure and determine the reference voltage vector.

[0064] A motion control module, configured to modulate the reference voltage vector into a duty cycle signal through a space vector pulse width modulation algorithm to control the motion of the free piston internal combustion power generation system.

[0065] In an exemplary embodiment, a computer device is provided, including a memory and a processor. A computer program is stored in the memory, and when the processor executes the computer program, the steps in the above method embodiments are implemented. The computer device may be a server or a terminal, and its internal structure diagram may be as Figure 6 shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, abbreviated as I / O), and a communication interface. Among them, the processor, the memory, and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store data to be processed. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals through a network connection. When the computer program is executed by the processor, a motion control method for a free piston internal combustion power generation system based on a trajectory is implemented.

[0066] Those skilled in the art can understand that Figure 6 the structure shown in

[0067] is only a block diagram of some structures related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements. In an exemplary embodiment, a computer device is provided, including a memory and a processor. A computer program is stored in the memory, and when the processor executes the computer program, the steps in the above method embodiments are implemented.

[0068] In an exemplary embodiment, a computer program product is provided, including a computer program which, when executed by a processor, implements the steps in the above method embodiments.

[0069] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use, and processing of relevant data need to comply with relevant regulations.

[0070] Those of ordinary skill in the art can understand that all or part of the processes of implementing the above method embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above method embodiments. Among them, any reference to a memory, database, or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memories. Non-volatile memories can include read-only memory (ROM), magnetic tapes, floppy disks, flash memories, optical memories, high-density embedded non-volatile memories, resistive random access memories (ReRAM), magnetoresistive random access memories (MRAM), ferroelectric random access memories (FRAM), phase change memories (PCM), graphene memories, etc. Volatile memories can include random access memories (RAM) or external cache memories, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0071] The databases involved in the embodiments provided in this application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., without limitation. The processors involved in the embodiments provided in this application can be general-purpose processors, central processors, graphics processors, digital signal processors, programmable logics, data processing logics based on quantum computing, etc., without limitation.

[0072] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0073] Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation on the present application.

Claims

1. A trajectory-based free piston internal combustion power generation system motion control method, characterized in that: include: determining an operating state of the free piston type internal combustion power generation system according to operating parameters of the free piston type internal combustion power generation system; Determining reference trajectories of the free-piston internal combustion power generation system under different operating conditions; A dual-loop motion control structure is used to track the reference trajectory and determine a reference voltage vector; The reference voltage vector is modulated into a duty cycle signal through a space vector pulse width modulation algorithm to control the movement of a free piston internal combustion power generation system.

2. The trajectory-based free piston internal combustion power generation system motion control method according to claim 1 is characterized in that: The operating states of the free piston internal combustion power generation system include: a starting state, a transition state, a combustion state and a shutdown state.

3. The trajectory-based free piston internal combustion power generation system motion control method according to claim 2 is characterized in that: The operating state of the free piston internal combustion power generation system is determined according to the operating parameters of the free piston internal combustion power generation system, specifically including: When the linear motor in the free piston internal combustion power generation system starts to run, and the engine has not yet been injected with fuel for ignition or a misfire occurs, the free piston internal combustion power generation system enters a starting state when the piston moves to the top dead center during the compression stroke; When the engine starts to inject fuel and ignite, but the combustion is not complete or the combustion state is poor, the free piston internal combustion power generation system enters a transition state when the piston moves to the top dead center during the compression stroke; the incomplete combustion means 20bar<p max <35bar, the poor combustion state means 18bar <p max <30bar,p max is the maximum cylinder pressure; When the engine is fully burned, the free piston internal combustion power generation system enters the combustion state when the piston moves to the top dead center during the compression stroke; When the free piston type internal combustion power generation system receives a shutdown command, the free piston type internal combustion power generation system enters a shutdown state when the piston moves to the bottom dead center during the expansion stroke.

4. The trajectory-based free piston internal combustion power generation system motion control method according to claim 2, characterized in that: Determining the reference trajectory of the free-piston internal combustion power generation system under different operating conditions specifically includes: Determining that the reference trajectory in the starting state, the combustion state and the shutdown state is a sinusoidal symmetrical trajectory; The reference trajectory under the combustion state is determined to be an asymmetric high-order polynomial trajectory.

5. The trajectory-based free piston internal combustion power generation system motion control method according to claim 4 is characterized in that: The trajectory-based free piston internal combustion power generation system motion control method further includes: A genetic algorithm is used to optimize the reference trajectory under the combustion state.

6. The trajectory-based free piston internal combustion power generation system motion control method according to claim 5, characterized in that: The outer loop of the dual-loop motion control structure uses a sliding film controller, and the inner loop uses a PI controller.

7. The trajectory-based free piston internal combustion power generation system motion control method according to claim 6, characterized in that: The dual-loop motion control structure is used to track the reference trajectory and determine the reference voltage vector, specifically including: Based on the reference trajectory and the actual operation trajectory, a reference current is determined using a synovial controller; Based on the reference circuit and the actual current, a reference voltage vector is determined using a PI controller.

8. A trajectory-based free piston internal combustion power generation system motion control device, characterized in that: include: An operating state determination module, used to determine the operating state of the free piston type internal combustion power generation system according to the operating parameters of the free piston type internal combustion power generation system; A reference trajectory determination module, used to determine the reference trajectory of the free-piston internal combustion power generation system under different operating conditions; A reference voltage vector determination module, used to track the reference trajectory using a dual-loop motion control structure and determine a reference voltage vector; The motion control module is used to modulate the reference voltage vector into a duty cycle signal through a space vector pulse width modulation algorithm to control the motion of the free piston internal combustion power generation system.

9. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the trajectory-based free-piston internal combustion power generation system motion control method described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the trajectory-based free-piston internal combustion power generation system motion control method described in any one of claims 1 to 7 is implemented.

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