A method and system for regulating the timing of the intake of air into a multi-module free-piston engine group

Abstract

The application provides a kind of multi-module free piston engine group admission timing control method and system, it is related to internal combustion engine admission control technical field, method includes: with the time that piston reaches reference displacement as cycle timing reference;Based on cycle timing reference, the opening time and closing time of each admission splitter valve are calculated;Based on opening time and closing time, the mathematical model of the coupling aerodynamic system of common admission cavity-scavenging tank is established;According to the mathematical model of coupling aerodynamic system, a multi-objective optimization function is constructed;Set constraint condition;Under the constraint condition, according to the multi-objective optimization function, the optimal admission timing parameters and the optimal performance index value are solved by double-layer optimization algorithm;According to the optimal admission timing parameters and the optimal performance index value, the admission timing of engine group is controlled.The application can ensure that multi-module engine runs stably and efficiently in limited space.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine intake control technology, and in particular to an intake timing control method and system for a multi-module free piston engine. Background Technology

[0002] Free-piston engines eliminate the traditional crankshaft and connecting rod mechanism. Piston motion is directly determined by combustion pressure and load force, offering significant advantages such as compact structure, high power density, and strong fuel adaptability. They are the preferred power source for confined space propulsion equipment and can be widely used in underwater vehicles, portable generators, and special engineering machinery. To meet the demands of confined spaces for high-power, compact power systems, multi-module free-piston engine sets achieve kilowatt-level power output through multi-unit collaborative operation. However, due to stringent installation space constraints, their intake and exhaust systems must adopt a centralized arrangement in a common cavity, resulting in significant intake aerodynamic coupling interference problems that limit the overall engine performance.

[0003] Existing technologies for intake control schemes of multi-module free piston engines mostly adopt a single-dimensional optimization approach, typically only adjusting the opening sequence of the intake valve independently, or simply optimizing the geometry of the intake pipeline, without considering the inherent coupling relationship between the intake split structure layout and the opening and closing sequence of the intake valve. The control logic is simple and the design method is fragmented.

[0004] However, existing technologies only use single-parameter optimization and lack coordinated design of structure and intake timing, which can easily lead to intake coupling interference, uneven flow distribution and pressure fluctuation problems. At the same time, they have low space utilization and insufficient power density, making it difficult to meet the application requirements of stable and efficient operation of multi-module engines in confined spaces. Summary of the Invention

[0005] To address the technical challenges of existing technologies that employ single-parameter optimization, lack coordinated design of structure and intake timing, easily lead to intake coupling interference, uneven flow distribution, and pressure fluctuations, while also exhibiting low space utilization and insufficient power density, making it difficult to meet the application requirements of stable and efficient operation of multi-module engines in confined spaces.

[0006] The technical solution provided by this invention is as follows: The first aspect of this invention provides a method for controlling the intake timing of a multi-module free piston engine, comprising: S1: The moment when the piston reaches the reference displacement is used as the cycle timing reference; S2: Based on the cyclic timing reference, calculate the opening and closing times of each intake split valve; S3: Based on the opening and closing times, establish a mathematical model of the coupled aerodynamic system of the common intake chamber and scavenging box; S4: Construct a multi-objective optimization function based on the mathematical model of the coupled aerodynamic system; S5: Set constraints; S6: Under constraints, the optimal intake timing parameters and optimal performance index values ​​are solved using a two-level optimization algorithm based on the multi-objective optimization function. S7: Adjust the intake timing of the engine unit according to the optimal intake timing parameters and the optimal performance index value.

[0007] A second aspect of the present invention provides an intake timing control system for a multi-module free piston engine assembly, applied to the intake timing control method for the multi-module free piston engine assembly of the first aspect, comprising: Intake timing control module, intake boosting module, multi-module free piston engine, sensor module, fuel injection module, and cooling module; The intake timing control module is used to establish a mathematical model of the coupled aerodynamic system of the common intake chamber and scavenging box and solve for the optimal performance. It outputs the intake valve opening and closing timing command to make the intake pressure waves of each module symmetrically interfere in the common chamber and suppress coupling interference. The intake boost module consists of two rectangular common intake chambers symmetrically arranged on both sides of the device, with the inlet connected to the output end of the booster; the installation position of the branch pipe on the common intake chamber is determined by the optimization model to make the intake pressure waves symmetrically interfere and reduce the difference in intake volume. The multi-module free piston engine has a sequential flat layout, with the scavenging air inlets of multiple engine modules vertically connected to a rectangular common air intake chamber via intake branch pipes, forming a common chamber stable air intake structure. The sensor module includes a cylinder pressure sensor, an intake flow meter, a piston displacement sensor, and a temperature sensor, which are respectively located on the inner wall of the scavenging box, the intake seat, the motor, and the cylinder head. The sensor collects parameters and transmits them to the intake timing control module. The fuel injection module includes a fuel pump, an electromagnetic fuel injector, a high-pressure common rail, and a fuel supply support frame. The fuel injection module is linked with the intake timing control module to synchronously adjust the fuel injection timing and fuel injection quantity. The cooling module includes a water pump and a cooling circuit. The water pump is located between the two turbochargers, and the cooling circuit is located above the engine casing to ensure a stable combustion environment.

[0008] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the intake timing control method for a multi-module free piston engine assembly as described in the first aspect.

[0009] The beneficial effects of the technical solution provided by this invention include: In this embodiment of the invention, a mathematical model and multi-objective optimization function of the coupled aerodynamic system of the common intake chamber-scavenging box are constructed. The intake split structure and intake timing are jointly optimized through a two-layer optimization algorithm, which effectively suppresses intake aerodynamic coupling interference, balances the intake flow of each branch, and reduces system pressure fluctuation. At the same time, the optimal intake timing parameters and optimal performance indicators are solved under multiple constraints, which improves the system space utilization and power density, and ensures that the multi-module engine operates stably and efficiently in a confined space. Attached Figure Description

[0010] Figure 1 A flowchart illustrating an intake timing control method for a multi-module free piston engine assembly provided in an embodiment of the present invention; Figure 2 A schematic diagram of a common air intake chamber arranged symmetrically on both sides, provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of a coupled pneumatic system model of a common intake chamber and a scavenging box provided in an embodiment of the present invention. Figure 4 This is a schematic diagram of the intake timing control system for a multi-module free piston engine assembly provided in an embodiment of the present invention. Detailed Implementation

[0011] Reference manual attached Figure 1 The diagram shows a flowchart of an intake timing control method for a multi-module free piston engine provided by an embodiment of the present invention.

[0012] This invention provides a method for controlling the intake timing of a multi-module free piston engine, which may include the following steps: S1: The time when the piston reaches the reference displacement is used as the cycle timing reference.

[0013] Specifically, detecting piston displacement x ( t )satisfy: ; Furthermore, As the first k Reference time for the cycle.

[0014] in, x ref Indicates the preset reference displacement. Used to distinguish between two crossings of the same displacement during the reciprocating motion of a piston.

[0015] It should be noted that the piston displacement is detected using the bottom dead center position of the piston-moving component as the reference displacement. x ( tThe moment when the above conditions are met is considered as the first... k The reference time of the cycle is used as a unified timing reference for the six intake split valves to distinguish between the compression stroke and expansion stroke of the piston reciprocating motion, thus avoiding timing misalignment of multiple modules.

[0016] In this embodiment of the invention, a unified cyclic timing reference is established at the moment when the piston reaches a preset reference displacement and the movement speed is positive. The bottom dead center position of the piston-moving component is also specifically selected as the reference displacement. This not only accurately distinguishes the two crossings of the same displacement in the piston reciprocating motion through the dual determination of displacement and movement speed, clearly defining the compression stroke and the expansion stroke, but also sets a unified timing reference standard for the six intake manifold valves, effectively avoiding the intake timing misalignment problem in multi-module engines and ensuring that the opening and closing times of each manifold valve are accurately matched with the piston scavenging process.

[0017] S2: Based on the cyclic timing reference, calculate the opening and closing times of each intake split valve.

[0018] In one possible implementation, S2 specifically includes: S201: Based on the cyclic timing reference, define the opening phase offset and opening duration of each intake split valve.

[0019] S202: Calculate the start time and stop time based on the start phase offset and start duration.

[0020] The specific start time is as follows: ; in, i Indicates the index of the intake manifold valve. k Indicates the index of the cycle. Indicates the first k The first cycle i The opening time of each intake manifold valve Indicates the first k The reference time for each cycle, Indicates the first k The first cycle i The opening phase offset of each intake split valve.

[0021] The specific closing time is as follows: ; in, Indicates the first k The first cycle i The closing time of each intake manifold valve Indicates the first k The first cycle i The duration of the intake manifold valve's opening.

[0022] It should be noted that the effective flow area function of each diverter valve adopts an ideal switching form: ; in, t Indicates time, A i Indicates the first i The effective flow area of ​​each intake manifold valve A i,max Indicates the first i The maximum flow area of ​​each intake manifold valve H ( ) represents the Heaviside step function.

[0023] Optionally, .

[0024] In this embodiment of the invention, a unified cyclic timing benchmark is used as the calculation basis. First, the opening phase offset and opening duration of each intake split valve are defined. Then, the opening and closing times of each split valve in the corresponding cycle are accurately calculated using a quantitative formula. This achieves independent quantitative control of the opening and closing timing of each split valve, ensuring that the timing parameters of each valve are precisely matched with the piston movement cycle, and that the timing of a single valve can be adjusted differently according to the intake requirements of multi-module engines. At the same time, an effective flow area function in the form of an ideal switch is configured for each split valve. Combined with an optional fixed maximum flow area parameter, the dynamic change law of the flow area of ​​the split valve from opening to closing can be accurately depicted, so that the valve orifice flow characteristics are highly consistent with the calculated opening and closing times.

[0025] Reference manual attached Figure 2 The diagram shows a schematic of a common air intake chamber arranged symmetrically on both sides according to an embodiment of the present invention.

[0026] It should be noted that the port connects to two symmetrically arranged turbochargers, the left common intake chamber, and six identical sets of intake manifolds and intake branch pipes. The manifold layout of the symmetrical common intake chambers on both sides is exactly the same, with a wall thickness of 2. mm The single-cavity cross-sectional dimension is 110 mm wide. mm × Height 50 mm Cavity length 1310 mm They are symmetrically arranged on the left and right sides of the system along the length of the engine assembly.

[0027] Reference manual attached Figure 3 The diagram shows a schematic of a coupled pneumatic system model of a common intake chamber and scavenging box provided by an embodiment of the present invention.

[0028] S3: Based on the opening and closing times, establish a mathematical model of the coupled aerodynamic system of the common intake chamber and scavenging box.

[0029] Optionally, the mathematical model of the coupled aerodynamic system specifically includes: the mass conservation equation and the energy conservation equation.

[0030] It should be noted that the common intake chamber and scavenging chamber are respectively regarded as lumped parameter containers, the gas is regarded as an ideal gas, and the diverter valve and scavenging port adopt a compressible throttling flow model.

[0031] Specifically, the left and right common intake chambers and the scavenging boxes of each unit are all considered as lumped parameter containers, and the intake working fluid (air) is considered as an ideal gas, with specific heat ratio taken as... gas constant Both the diverter valve and the scavenging port adopt a compressible throttling flow model.

[0032] The mass conservation equation for the single-sided common intake chamber parameter model is as follows: ; in, m p This indicates the mass of gas within the single-sided common intake chamber. This indicates the mass flow rate of air supplied by the booster to this chamber. i Indicates the index of the intake manifold valve. n This indicates the total number of intake manifold valves. Indicates the first i Mass flow rate of each intake manifold valve C d Represents the flow coefficient. t Indicates time, A i Indicates the first i The effective flow area of ​​each intake manifold valve p p This indicates the pressure within the common intake chamber on one side. Indicates the specific heat ratio of a gas. R Represents the gas constant. T p This indicates the gas temperature within the single-sided common intake chamber. This represents a compressible throttling function. p s Indicates the pressure of the scavenging air box. Indicates the pressure ratio. This indicates the critical pressure ratio.

[0033] Optionally, C d Take 0.72.

[0034] The ideal gas state equation for the single-sided common intake chamber parameter model is as follows: ; in, Vp This indicates the gas volume within the common intake chamber on one side.

[0035] The mass conservation equation for the scavenging chamber is as follows: ; in, m s This indicates the mass of the gas in the scavenging chamber. Indicates the scavenging port mass flow rate. C sc Indicates the scavenging port flow coefficient. A sc This indicates the effective flow area of ​​the scavenging port triggered by piston displacement. T s This indicates the temperature of the gas inside the scavenging chamber. p c This indicates the cylinder pressure.

[0036] Optionally, C sc Take 0.68.

[0037] It should be noted that the effective flow area of ​​the scavenging port triggered by the piston displacement is determined by the real-time displacement of the piston. When the piston moves to open the scavenging port, the effective area increases with the increase of the piston displacement, and decreases with the decrease of the displacement when the piston is closed.

[0038] The gas state equation for the scavenging chamber is as follows: ; in, V s This indicates the volume of gas inside the scavenging chamber.

[0039] In this embodiment of the invention, a mathematical model of the coupled aerodynamic system of the common intake chamber and scavenging box is built by combining the actual structural parameters of the double-sided symmetrical common intake chamber. The common intake chamber and scavenging box are regarded as lumped parameter containers, and the intake working fluid is regarded as an ideal gas and given specific parameters such as specific heat ratio and gas constant. At the same time, a compressible throttling flow model is configured for the diverter valve and scavenging port and a reference value of the flow coefficient is given. Furthermore, the mass conservation equation and ideal gas state equation for the single-sided common intake chamber and scavenging box are specifically established. The mass flow calculation formula and compressible throttling function of the diverter valve and scavenging port are derived. The flow characteristics, mass transfer law and aerodynamic coupling relationship of the gas in the intake system of a multi-module engine under confined space are accurately and realistically characterized. The model has strong real-world adaptability based on actual structural parameters, and the complete equation system realizes the quantitative description of the dynamic changes of core parameters such as pressure, temperature and gas mass in the intake chamber and scavenging box.

[0040] S4: Construct a multi-objective optimization function based on the mathematical model of the coupled aerodynamic system.

[0041] It should be noted that the nested two-layer optimization variable system and multi-objective optimization function achieve coordinated global optimization of the intake splitter position and intake timing. Inner layer optimization variables: The timing parameters of the six splitter valves are used as inner layer optimization variables, forming a twelve-dimensional optimization vector. ; in, Indicates the first k The opening phase offset of the six intake manifold valves in each cycle. Indicates the first k The core of the inner-layer optimization is to determine the opening duration of the six intake split valves in each cycle, given the positions of the split valves, and to minimize the multi-objective optimization function. Since the dual-sided common intake chamber is symmetrically arranged, the axial positions of the six split valves in each side's common intake chamber are used as outer-layer optimization variables, forming a six-dimensional optimization vector: In the formula, These represent the axial coordinates of the six split ports on a single-sided common air intake chamber along the length of the chamber, which correspond to the installation positions of the six engine units. The core of the outer layer optimization is to solve for the optimal split port layout to achieve optimal global performance.

[0042] Optionally, the multi-objective optimization function specifically includes: scavenging air box pressure tracking term, scavenging air box pressure fluctuation term, branch flow uniformity term, total air supply insufficient penalty term, time sequence change smoothing term, cylinder pressure deviation term, and flow deviation term.

[0043] The multi-objective optimization function is specifically as follows: ; in, k Indicates the index of the cycle. j Indicates the index of the sub-target. Indicates the first k The multi-objective optimization function value of the loop. ω j Indicates the first j The weighting coefficients of each sub-objective Indicates the first k The first cycle j The function value of each sub-objective.

[0044] It should be noted that, considering the priority of engineering applications, the weight coefficients for each sub-objective item are set as follows: .

[0045] The scavenging chamber pressure tracking item specifically includes: ; in, Indicates the first kThe function value of the pressure tracking term for the cyclic scavenging chamber. p s Indicates the pressure of the scavenging air box. t Indicates time, p ref This indicates the target reference pressure.

[0046] Optionally, p ref Take 1.2 bar.

[0047] Specifically, the scavenging chamber pressure fluctuation item is as follows: ; in, Indicates the first k The function value of the pressure fluctuation term in the cyclic scavenging chamber. Indicates the first k The average pressure of each cycle is used to suppress pressure oscillations caused by the intake process.

[0048] Specifically, the term for branch flow uniformity is as follows: ; in, Indicates the first k The function value of the uniformity of flow in each cyclic branch. i Indicates the index of the intake manifold valve. Indicates the first i Mass flow rate of each intake manifold valve This represents the average branch flow rate, used to ensure the consistency of the intake airflow in the six branches and reduce the difference in intake airflow between modules.

[0049] The specific penalties for insufficient total gas supply are as follows: ; in, Indicates the first k The function value of the penalty term for insufficient total gas supply in each cycle; Max indicates taking the maximum value. M ref Indicates the target total gas supply. Indicates the first k The total air supply for each cycle is adjusted. When the total intake air volume in a single cycle is lower than the target total air supply volume, a secondary penalty is applied to ensure the required charge volume for the engine's rated power output.

[0050] The time-series smoothing term specifically includes: ; in, Indicates the first kThe function value of the timing smoothing term in each cycle limits abrupt changes in timing parameters between adjacent cycles, avoiding shocks in valve control actions and fluctuations in system operating conditions. n This indicates the total number of intake manifold valves. Indicates the first k The first cycle i The opening phase offset of each intake split valve Indicates the first k -1st cycle i The opening phase offset of each intake split valve Indicates the first k The first cycle i The duration of the intake manifold valve's opening. Indicates the first k -1st cycle i The duration of the intake manifold valve's opening.

[0051] Specifically, the cylinder pressure deviation item is as follows: ; in, Indicates the first k The function value of the cylinder pressure deviation term in each cycle. p c,m This represents the cylinder pressure measurement value, including bias and noise, used to ensure consistent combustion within each module and reduce power output deviation between cylinders. p c,ref A reference value indicating cylinder pressure. p c Indicates cylinder pressure, b p This represents the fixed bias error in cylinder pressure measurement. η p This represents the random noise error in cylinder pressure measurement.

[0052] Specifically, the flow deviation item is as follows: ; in, Indicates the first k The function value of the cyclic flow deviation term. Indicates the first i Each intake split valve contains flow measurement values ​​for bias and noise, used to ensure the control accuracy of the intake flow in each branch. Indicates the first i The target reference mass flow rate for each intake split valve b m,i Indicates the first i Fixed bias error in flow measurement of each intake split valve η m,i Indicates the first iRandom noise error in the flow measurement of each intake split valve.

[0053] In this embodiment of the invention, a multi-objective optimization function with nested double-layer optimization is constructed based on the established mathematical model of the coupled aerodynamic system. By setting the timing parameters of the six split valves as twelve-dimensional inner-layer optimization variables and the axial positions of the six split ports of the single-sided common intake chamber as six-dimensional outer-layer optimization variables, the coupled and coordinated global optimization design of intake timing and split port positions is realized. At the same time, seven sub-objective functions covering scavenging box pressure tracking, fluctuation suppression, branch flow uniformity, total air supply guarantee, timing smoothness, cylinder pressure deviation, and flow deviation are constructed. Reasonable weight coefficients are assigned to each sub-objective in combination with engineering application priorities. A precise quantitative calculation method is also designed for each sub-objective. This not only comprehensively covers the core performance control requirements of the intake system of a multi-module free piston engine, but also highlights the optimization focus under different operating conditions through weight allocation. In addition, the calculation formulas of each sub-objective are all based on the core parameters of the aerodynamic model and the actual measurement error characteristics, so that the optimization objectives are highly consistent with the actual aerodynamic laws of the intake system and the sensor measurement characteristics.

[0054] S5: Set constraints.

[0055] Optionally, the constraints specifically include: time-series variable constraints, spatial boundary constraints, scavenging box pressure constraints, and backflow prevention constraints.

[0056] Among them, the timing variable constraint condition can ensure that the intake timing is accurately matched with the piston scavenging process, specifically: ; in, i Indicates the index of the intake manifold valve. k Indicates the index of the cycle. Indicates the first i The minimum value of the opening phase offset of each intake split valve Indicates the first k The first cycle i The opening phase offset of each intake split valve Indicates the first i The maximum value of the opening phase offset of each intake split valve. Indicates the first i The minimum duration of opening of each intake manifold valve. Indicates the first k The first cycle i The duration of the intake manifold valve's opening. Indicates the first i The maximum duration of the opening of each intake split valve.

[0057] Optionally, the time series variable constraints are as follows: ; The specific spatial boundary constraints are as follows: ; in, V Represents the total volume of the system. L Indicates the total length of the system. W Indicates the total width of the system. H Indicates the total height of the system. V max This represents the maximum volume of the confined space. L c Indicates the length of the air intake chamber. L s This indicates the distance from the air inlet of the air intake chamber to the end face of the water pump. w engine This indicates the width of a single engine module. L engine This indicates the length of a single engine module. W oil This indicates the width of the oil supply support frame. H oil Indicates the length of the oil supply support frame. H c This indicates the height of the rectangular common air intake chamber.

[0058] It should be noted that the overall size of the system meets the above conditions, and the axial spacing between adjacent flow ports avoids mutual interference of pressure waves between adjacent flow ports, while also meeting the installation spacing requirements of the engine unit.

[0059] Among them, the scavenging air box pressure constraint condition can prevent insufficient scavenging due to excessively low pressure, or component overload due to excessively high pressure, specifically: ; in, t Indicates time, p s,min This indicates the minimum pressure in the scavenging air box. p s Indicates the pressure of the scavenging air box. p s,max This indicates the maximum pressure of the scavenging air chamber.

[0060] Optionally, the scavenging air box pressure constraint conditions are as follows: ; Among them, the backflow prevention constraint ensures that the pressure before the valve is always higher than the pressure after the valve, preventing high-pressure gas in the scavenging chamber from flowing back into the common intake chamber, which would cause a decrease in intake efficiency and system pressure oscillation. Specifically: ; in, p p Indicates the pressure within a single common intake chamber, ∆ p min This represents the minimum pressure difference threshold between the common intake chamber and the scavenging chamber.

[0061] Optionally, ∆ p min Take 5 kPa .

[0062] In this embodiment of the invention, four core constraints are set to address the intake control and confined space application requirements of multi-module free piston engine units: timing variables, spatial boundaries, scavenging box pressure, and backflow prevention. Specific numerical thresholds tailored to engineering realities are also configured for each constraint. Each constraint performs its function and cooperates with others to form comprehensive optimized boundary control: timing variable constraints limit the range of values ​​for the diverter valve opening phase offset and duration, ensuring precise matching between the intake timing and the piston scavenging process, preventing valve control actions from deviating from the engine's mechanical motion laws; spatial boundary constraints are combined with the core components of the system... The component dimensions are derived and the overall system volume is limited, while taking into account the spacing between the flow dividers and the engine installation requirements. This ensures strict adaptation to the installation boundaries of the confined space and avoids mutual interference of pressure waves from the flow dividers from a structural perspective. The scavenging box pressure constraint effectively avoids insufficient scavenging caused by excessively low pressure and component overload caused by excessively high pressure by limiting the upper and lower pressure limits, thus ensuring the safety of engine combustion and component operation. The backflow prevention constraint ensures that the pressure before the valve is always higher than the pressure after the valve by limiting the minimum pressure difference between the common intake chamber and the scavenging box, thus avoiding the decrease in intake efficiency and system pressure oscillation caused by backflow of gas from the scavenging box from a pressure perspective.

[0063] S6: Under constraints, the optimal intake timing parameters and optimal performance index values ​​are solved using a two-level optimization algorithm based on the multi-objective optimization function.

[0064] In one possible implementation, S6 specifically includes: S601: Set the initial position of the outer layer optimization, the initial timing parameters of the inner layer optimization, and the optimization convergence threshold.

[0065] The initial position of the outer layer optimization is: The connection port between the common intake chamber and the turbocharger, based on the initial layout within the confined space, sets the initial equidistant positions of the six split ports on one side. , .

[0066] The initial timing parameters for the inner layer optimization are: .

[0067] in, Indicates the first iInitial value of the opening phase offset of each intake split valve Indicates the first i Initial value of the opening duration of each intake split valve.

[0068] Wherein, the optimized convergence threshold is The maximum number of iterations is 50 for the outer layer and 200 for the inner layer.

[0069] S602: Under constraints, based on the initial position and initial timing parameters, the initial intake timing parameters and initial performance index values ​​are obtained through a sequential quadratic programming algorithm with the objective of minimizing the multi-objective optimization function.

[0070] Among them, the sequential quadratic programming algorithm is an efficient local numerical optimization algorithm that is suitable for single-objective continuous optimization problems with inner constraints. It can quickly and accurately minimize the multi-objective optimization function under the condition of a given splitter position, and stably solve for the optimal intake timing parameters that satisfy all constraints. It has the characteristics of fast convergence, high accuracy, and suitability for real-time control solutions.

[0071] Specifically, regarding the given location of the shunt port in the outer layer... With the goal of minimizing the multi-objective optimization function, and under the constraints of timing, pressure and anti-backflow, a sequential quadratic programming algorithm is used to solve the inner-layer optimization problem, so as to obtain the initial intake timing parameters and the corresponding initial performance index values ​​under the current layout, and form the performance envelope point under this layout.

[0072] S603: The initial intake timing parameters and initial performance index values ​​are updated using a non-dominated sorting genetic algorithm.

[0073] Among them, the non-dominated sorting genetic algorithm is an intelligent global multi-objective optimization algorithm that is suitable for global optimization of the location of the outer branch outlet. It can traverse multiple feasible solutions in complex spatial layouts and obtain a set of non-dominated optimal layout schemes through iterative evolution, taking into account the balance of multi-dimensional performance indicators, and finally achieving the global optimal matching of the branch outlet location.

[0074] Specifically, the outer layer is located at the branch port. To optimize the variables, the initial performance metrics output by the inner layer are used as the optimization objective, and a non-dominated sorting genetic algorithm is employed for iterative optimization. After each iteration updates the location of the branch outlet, the inner layer is called again to solve for the corresponding time-series parameters and performance metrics.

[0075] S604: Based on the update results, when the outer layer optimization iteration reaches the maximum number of iterations or the change in performance index of adjacent iterations is less than the optimization convergence threshold, solve for the optimal intake timing parameters and the optimal performance index value.

[0076] In this embodiment of the invention, under four types of constraints—timing, space, pressure, and backflow prevention—a nested two-layer optimization algorithm is used to optimize the intake control system. By reasonably setting the initial position of the splitter, the initial timing parameters, the convergence threshold, and the number of iterations, the inner-layer sequential quadratic programming algorithm is used to quickly and accurately solve the optimal intake timing under a fixed layout. Then, the outer-layer non-dominated sorting genetic algorithm is used to globally optimize the optimal splitter position. During the iteration process, the parameters are continuously updated and the calculation is terminated with a convergence condition. This ensures that the local optimal timing solution is obtained quickly and stably under complex constraints, and also achieves global synergistic optimization of the splitter position and the intake timing. The final output of the optimal intake timing parameters and optimal performance index values ​​can be directly used for the precise control of multi-module free piston engine sets, greatly improving the optimization efficiency, solution accuracy, and engineering practicality of the intake system.

[0077] S7: Adjust the intake timing of the engine unit according to the optimal intake timing parameters and the optimal performance index value.

[0078] Furthermore, based on the optimal diversion port location The installation positions of the six shunt ports on the single-sided common air intake chamber were determined as follows: , This serves as the installation location for the six free piston engines, with the common intake chamber arranged symmetrically on both sides, thus completing the optimization and finalization of the system structure layout.

[0079] In one possible implementation, after S7, the following is also included: S8: Feedback correction of the optimal intake timing parameters.

[0080] It should be noted that, in order to suppress control deviations caused by operating condition fluctuations, sensor measurement noise, and component characteristic drift, an online feedback correction stage is added on the basis of the reference timing obtained by offline dual-layer optimization to form closed-loop control and online feedback correction of the intake timing.

[0081] In one possible implementation, S8 specifically includes: S801: Calculate the average deviation of cylinder pressure and the average deviation of intake manifold flow rate.

[0082] Specifically, the average cylinder pressure deviation is as follows: ; in, t Indicates time, Indicates the first k Average cylinder pressure deviation per cycle T ω This represents the time window for calculating cylinder pressure deviation. p c,m This represents the cylinder pressure measurement, including bias and noise.p c,ref This indicates a reference value for cylinder pressure.

[0083] Specifically, the average flow deviation of the intake splitter valve is as follows: ; in, Indicates the first k The first cycle i Average flow deviation of each intake split valve Indicates the first i The intake manifold valve includes flow measurement values ​​for bias and noise. Indicates the first i The target reference mass flow rate for each intake split valve.

[0084] S802: Based on the average deviation of cylinder pressure and the average deviation of flow rate, the optimal intake timing parameters are corrected through an incremental feedback correction law.

[0085] Among them, the incremental feedback correction law is a control law that performs cycle-by-cycle fine-tuning based on real-time deviation. It does not directly recalculate the complete timing parameters, but introduces the corresponding feedback gain coefficient based on the magnitude of the cylinder pressure average deviation and flow average deviation of the previous cycle timing. It incrementally corrects the opening phase offset and opening duration, so that the intake timing of the next cycle is dynamically adjusted in the direction of reducing deviation. At the same time, it is combined with boundary limiting to ensure control safety, thereby achieving adaptive suppression of operating condition fluctuations, measurement noise and component drift, forming a stable and smooth closed-loop intake timing control.

[0086] Specifically, an incremental feedback correction law is used to update the first... k +1 cycle intake timing parameters: ; in, Indicates the first k +1 cycle i The opening phase offset of each intake split valve Indicates the first k The first cycle i The opening phase offset of each intake split valve Indicates the feedback gain coefficient. Indicates the feedback gain coefficient. Indicates the first k +1 cycle i The duration of the intake manifold valve's opening. Indicates the first k The first cycle i The duration of the intake manifold valve's opening. Indicates the feedback gain coefficient. This represents the feedback gain coefficient.

[0087] It should be noted that the corrected timing parameters must meet timing boundary constraints. If the parameters exceed the boundaries, amplitude limiting will be applied to ensure the safety of valve control actions. The intake timing control module outputs PWM control commands to the six intake split valves according to the corrected opening and closing timing, and simultaneously updates the injection timing and injection quantity of the fuel injection module to achieve coordinated closed-loop control and ensure the consistency and stability of multi-module operation.

[0088] In this embodiment of the invention, an online feedback correction stage is added based on the optimal intake timing parameters obtained from offline dual-layer optimization, constructing a closed-loop control system for the intake timing. First, the average cylinder pressure deviation and the average flow deviation of each intake split valve are accurately calculated using a quantitative formula, transforming the control deviations caused by sensor measurement errors and operating condition fluctuations into quantifiable correction criteria. Then, relying on an incremental feedback correction law and combined with a feedback gain coefficient, the opening phase offset and opening duration of the next cycle are specifically corrected. Simultaneously, boundary limiting processing is applied to the corrected timing parameters to ensure the safety of valve control actions. It can also synchronously update the injection timing and injection quantity of the injection module to achieve coordinated control. This effectively suppresses control deviations caused by operating condition fluctuations, sensor measurement noise, and component characteristic drift, making up for the shortcomings of offline optimization in adapting to real-time operating condition changes. It allows the intake timing parameters to be dynamically adjusted according to the actual operating state of the engine, significantly improving the real-time performance, accuracy, and robustness of intake control, further ensuring the control accuracy of cylinder pressure and flow of multi-module engines, as well as the consistency of operation of each module and the long-term stable operation of the overall system.

[0089] Reference manual attached Figure 4 The diagram shows a schematic of the intake timing control system for a multi-module free piston engine provided in an embodiment of the present invention.

[0090] This invention also provides an intake timing control system for a multi-module free piston engine assembly, applied to the aforementioned intake timing control method for the multi-module free piston engine assembly, comprising: The system includes an intake timing control module 1, an intake boosting module 2, a multi-module free piston engine 3, a sensor module 4, a fuel injection module 5, and a cooling module 6.

[0091] The intake timing control module 1 is used to establish a mathematical model of the coupled pneumatic system of the common intake chamber and scavenging box and solve for the optimal performance. It outputs the intake valve opening and closing timing command so that the intake pressure waves of each module interfere symmetrically in the common chamber and suppress coupling interference.

[0092] The intake booster module 2 consists of two rectangular common intake chambers symmetrically arranged on both sides of the device, with the inlet connected to the booster output. The installation position of the split branch pipe on the common intake chamber is determined by an optimization model to ensure symmetrical interference of the intake pressure waves and reduce the difference in intake volume.

[0093] The multi-module free piston engine 3 has a sequential flat layout, with multiple engine module scavenging air box inlets vertically connected to a rectangular common air intake chamber via air intake branch pipes, forming a common chamber stable air intake structure.

[0094] The sensor module 4 includes a cylinder pressure sensor, an intake flow meter, a piston displacement sensor, and a temperature sensor, which are respectively located on the inner wall of the scavenging box, the intake seat, the motor, and the cylinder head. The sensor collects parameters and transmits them to the intake timing control module 1.

[0095] The fuel injection module 5 includes a fuel pump, an electromagnetic fuel injector, a high-pressure common rail, and a fuel supply support frame. The fuel injection module 5 is linked with the intake timing control module 1 to synchronously adjust the fuel injection timing and fuel injection quantity.

[0096] The cooling module 6 includes a water pump and a cooling circuit. The water pump is located between the two turbochargers, and the cooling circuit is located above the engine casing 3 to ensure a stable combustion environment.

[0097] It should be noted that the final overall dimensions of the system are 1320mm in length, 1140mm in width, and 330mm in height, which fully meets the preset space constraints. At the same time, it achieves the optimization effect of ≤3% non-uniformity of air intake flow in each branch and ≤8kPa pressure fluctuation in the scavenging box.

[0098] In this embodiment of the invention, the multi-module free piston engine intake timing control system is highly compatible with the aforementioned intake timing control method, and features hardware and software synergy. It integrates six core modules—intake timing control, intake boosting, multi-module engine, sensing, fuel injection, and cooling—and employs a scientific structural layout and functional design. The intake timing control module outputs precise start-stop timing commands based on a coupled aerodynamic model. The intake boosting module uses a double-sided symmetrical common intake chamber with optimized branch pipe positions to achieve symmetrical interference of intake pressure waves and suppress coupling interference. The multi-module engine adopts a sequential, flat layout to form a stable common-cavity intake structure. The sensor module collects operating parameters in all dimensions to provide real-time data support for control. The system features a coordinated injection and control module that works in tandem to ensure proper injection timing, while a cooling module creates a stable combustion environment. The overall dimensions of the system strictly adhere to space constraints, achieving excellent optimization results with intake flow non-uniformity of ≤3% and scavenging box pressure fluctuation of ≤8kPa across all branches. This hardware structure ensures the practical implementation of the intake control method, and through the coordinated operation of each module, it effectively improves the stability of the multi-module engine intake system and the consistency of operation across modules, significantly reducing intake volume differences and pressure fluctuations. This makes the entire intake control scheme highly practical and feasible for engineering applications, comprehensively guaranteeing the efficient and stable operation of the multi-module free piston engine.

[0099] This invention provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the intake timing control method for a multi-module free piston engine as described in the method embodiment.

[0100] The computer-readable storage medium provided by this invention can implement the steps and effects of the intake timing control method for the multi-module free piston engine group described in the above method embodiments. To avoid repetition, this invention will not elaborate further.

[0101] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for controlling the intake timing of a multi-module free piston engine, characterized in that, include: S1: The moment when the piston reaches the reference displacement is used as the cycle timing reference; S2: Based on the aforementioned cyclic timing reference, calculate the opening and closing times of each intake split valve; S3: Based on the opening and closing times, establish a mathematical model of the coupled pneumatic system of the common intake chamber and scavenging box; S4: Construct a multi-objective optimization function based on the mathematical model of the coupled aerodynamic system; S5: Set constraints; S6: Under the constraints, the optimal intake timing parameters and optimal performance index values ​​are solved by a two-level optimization algorithm based on the multi-objective optimization function. S7: Adjust the intake timing of the engine unit according to the optimal intake timing parameters and the optimal performance index value.

2. The intake timing control method for a multi-module free piston engine assembly according to claim 1, characterized in that, S2 specifically includes: S201: Based on the cyclic timing reference, define the opening phase offset and opening duration of each of the intake split valves; S202: Calculate the opening time and the closing time based on the opening phase offset and the opening duration.

3. The intake timing control method for a multi-module free piston engine assembly according to claim 1, characterized in that, The mathematical model of the coupled aerodynamic system specifically includes: the mass conservation equation and the energy conservation equation.

4. The intake timing control method for a multi-module free piston engine assembly according to claim 1, characterized in that, The multi-objective optimization function specifically includes: scavenging air box pressure tracking term, scavenging air box pressure fluctuation term, branch flow uniformity term, total air supply insufficient penalty term, time sequence change smoothing term, cylinder pressure deviation term, and flow deviation term.

5. The intake timing control method for a multi-module free piston engine assembly according to claim 1, characterized in that, The constraints specifically include: time-series variable constraints, spatial boundary constraints, scavenging chamber pressure constraints, and backflow prevention constraints.

6. The intake timing control method for a multi-module free piston engine assembly according to claim 1, characterized in that, S6 specifically includes: S601: Set the initial position of the outer layer optimization, the initial timing parameters of the inner layer optimization, and the optimization convergence threshold; S602: Under the constraints, based on the initial position and the initial timing parameters, with the goal of minimizing the multi-objective optimization function, the initial intake timing parameters and initial performance index values ​​are obtained through a sequential quadratic programming algorithm. S603: Update the initial intake timing parameters and the initial performance index values ​​using a non-dominated sorting genetic algorithm; S604: Based on the update results, when the outer layer optimization iteration reaches the maximum number of iterations or the change in performance index of adjacent iterations is less than the optimization convergence threshold, the optimal intake timing parameters and the optimal performance index values ​​are solved.

7. The intake timing control method for a multi-module free piston engine assembly according to claim 1, characterized in that, Following S7, it also includes: S8: Feedback correction is performed on the optimal intake timing parameters.

8. The intake timing control method for a multi-module free piston engine assembly according to claim 7, characterized in that, S8 specifically includes: S801: Calculate the average cylinder pressure deviation and the average flow deviation of the intake manifold valve; S802: Based on the average cylinder pressure deviation and the average flow rate deviation, the optimal intake timing parameters are corrected using an incremental feedback correction law.

9. An intake timing control system for a multi-module free piston engine assembly, applied to the intake timing control method for a multi-module free piston engine assembly as described in any one of claims 1 to 8, characterized in that, include: Intake timing control module (1), intake boosting module (2), multi-module free piston engine (3), sensor module (4), fuel injection module (5) and cooling module (6); The intake timing control module (1) is used to establish a mathematical model of the coupled pneumatic system of the common intake chamber-scavenging box and solve for the optimal performance, output the intake valve opening and closing timing command, so that the intake pressure waves of each module interfere symmetrically in the common chamber and suppress coupling interference. The intake booster module (2) consists of two rectangular common intake chambers symmetrically arranged on both sides of the device, with the inlet connected to the output end of the booster. The installation position of the branch pipe on the common intake chamber is determined by the optimization model to make the intake pressure wave symmetrically interfere and reduce the intake volume difference. The multi-module free piston engine (3) is laid out in sequence, and the air inlets of multiple engine modules are vertically connected to the rectangular common air inlet through the air inlet branch pipe to form a common cavity stable air inlet structure. The sensor module (4) includes a cylinder pressure sensor, an intake flow meter, a piston displacement sensor and a temperature sensor, which are respectively installed on the inner wall of the scavenging box, the intake seat, the motor and the cylinder head, to collect parameters and transmit them to the intake timing control module (1). The fuel injection module (5) includes a fuel pump, an electromagnetic fuel injector, a high-pressure common rail and a fuel supply support frame. The fuel injection module (5) and the intake timing control module (1) are linked to synchronously adjust the fuel injection timing and fuel injection quantity. The cooling module (6) includes a water pump and a cooling circuit. The water pump is located between the two turbochargers, and the cooling circuit is located above the engine (3) housing to ensure a stable combustion environment.

10. A readable storage medium, characterized in that, The readable storage medium stores a program or instructions that, when executed by a processor, implement the steps of the intake timing control method for a multi-module free piston engine assembly as described in any one of claims 1 to 8.

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