A dual-electronic expansion valve refrigerant distribution control method based on a hierarchical state machine

Abstract

The application discloses a kind of based on layered state machine's double electronic expansion valve refrigerant distribution control method, comprising the following steps: obtaining evaporator temperature, battery inlet coolant temperature, suction superheat, evaporator superheat and two electronic expansion valve opening degree;According to the actual evaporator temperature, temperature is layered, according to the battery inlet coolant temperature, battery cooling demand is identified, according to the current opening degree, valve position interval is determined, and according to the compressor suction superheat and the evaporator superheat, the superheat margin is determined;Supervise state machine according to the order of low temperature protection, passenger compartment temperature zone, battery cooling demand, valve position interval and superheat margin to carry out mode determination;According to target control mode, distribute control action;According to the opening degree instruction of two electronic expansion valves generated and outputted according to the distributed control action.The application can coordinate two evaporation branches of common compressor and common suction port, reduce refrigerant competition, low superheat and mode jitter risk.

Description

Technical Field

[0001] This invention relates to the field of vehicle thermal management and refrigeration control technology, and in particular to a dual electronic expansion valve refrigerant distribution control method based on a hierarchical state machine. Background Technology

[0002] Vehicle integrated thermal management systems typically utilize the same compressor and refrigeration circuit to simultaneously meet the cooling, dehumidification, and battery cooling needs of the passenger compartment. After being distributed, the high-pressure liquid refrigerant is throttled through the passenger compartment electronic expansion valve and the battery electronic expansion valve, and evaporates and absorbs heat in the corresponding heat exchangers. It then merges on the low-pressure side and enters the compressor.

[0003] Although each branch has its own throttling actuator, they share the compressor capacity and suction pressure. A change in the opening of either electronic expansion valve can alter the system's total flow rate, suction pressure, and the heat exchange status of the other branch. Therefore, treating the two branches as independent single-input, single-output systems can easily lead to refrigerant contention, inter-branch oscillations, insufficient suction superheat, evaporator frosting at low temperatures, and control instability caused by sudden valve changes.

[0004] Existing control schemes may adjust valves based on a single temperature deviation, lacking a unified arbitration of passenger compartment requirements, battery requirements, valve position ranges, and superheat safety margins, and also making it difficult to achieve smooth switching between different demand stages. Therefore, a collaborative refrigerant distribution scheme is needed that can handle branch coupling, clearly define control allocation, and take into account cryogenic protection. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a dual electronic expansion valve refrigerant distribution control method based on a hierarchical state machine. This method aims to solve the problems of refrigerant distribution conflict, insufficient superheat safety margin, mode switching oscillation, branch access disturbance, and untimely low temperature protection caused by the independent adjustment of the two electronic expansion valves when the two evaporator branches share the suction pressure and compressor capacity. It also enables the control logic to be parameterized and calibrated according to the driving or charging conditions.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a dual electronic expansion valve refrigerant distribution control method based on a hierarchical state machine, applied to a vehicle thermal management system. The vehicle thermal management system includes a passenger compartment evaporator branch and a power battery cooler branch that share a compressor and a common air intake. The passenger compartment evaporator branch is equipped with a passenger compartment electronic expansion valve, and the power battery cooler branch is equipped with a battery electronic expansion valve. The method includes the following steps: obtaining the actual evaporator temperature, the target evaporator temperature under the current operating conditions, the battery inlet coolant temperature, the battery requested inlet coolant temperature, the compressor suction superheat, the evaporator superheat, and the current opening of the two electronic expansion valves; Temperature stratification is performed based on the actual evaporator temperature, battery cooling requirements are identified based on the battery inlet coolant temperature, valve position range is determined based on the current opening degree, and superheat margin is determined based on the compressor suction superheat and the evaporator superheat. The supervisory state machine determines the target control mode from multiple control modes based on the temperature zone, battery cooling requirements, valve position range, and overheat margin. The supervisory state machine performs mode determination in the order of low temperature protection, passenger compartment temperature zone, battery cooling requirements, valve position range, and overheat margin. The temperature zone includes at least the unreached temperature zone where the actual evaporator temperature is higher than the evaporator target temperature, the reached temperature zone where the actual evaporator temperature is not higher than the evaporator target temperature but higher than the low temperature protection threshold, and the low temperature protection zone where the actual evaporator temperature is not higher than the low temperature protection threshold. According to the target control mode, control actions are assigned to the passenger compartment electronic expansion valve and the battery electronic expansion valve respectively in the evaporator temperature closed loop, battery inlet coolant temperature closed loop, compressor suction superheat closed loop, evaporator superheat closed loop, valve position holding and gradual closing. Based on the assigned control actions, the system generates and outputs opening commands for the two electronic expansion valves to coordinate the refrigerant flow between the two branches.

[0007] Preferably, the battery cooling demand is determined using a hysteresis state: when the battery inlet coolant temperature is not higher than the battery requested inlet coolant temperature, it enters the temperature-reaching state; when the battery inlet coolant temperature is higher than the sum of the battery requested inlet coolant temperature and the water temperature hysteresis, it returns to the high-demand state; and within the holding zone between the two, it maintains the original battery cooling demand state.

[0008] Preferably, the superheat margin and the valve position range are respectively formed into holding zones using entry threshold and exit threshold; when the monitored quantity is within the corresponding holding zone, the monitoring state machine maintains the original control mode or the original decision branch; when the mode switching condition continues to reach the condition confirmation time and the current mode reaches the minimum dwell time, the corresponding mode switching is executed.

[0009] Preferably, in the unreached temperature zone: when the battery has cooling requirements, the battery electronic expansion valve is in the large opening zone and the superheat margin is sufficient, the passenger compartment electronic expansion valve performs evaporator temperature closed-loop operation and the battery electronic expansion valve performs compressor suction superheat closed-loop operation; when the battery has cooling requirements, the battery electronic expansion valve is in the large opening zone and the superheat margin is insufficient, the current opening of the passenger compartment electronic expansion valve is maintained, and the battery electronic expansion valve performs compressor suction superheat closed-loop operation; when the battery electronic expansion valve enters the small opening zone, the passenger compartment electronic expansion valve performs evaporator superheat closed-loop operation and the current opening of the battery electronic expansion valve is maintained; when the battery reaches the requested temperature, the passenger compartment electronic expansion valve performs evaporator superheat closed-loop operation and the battery electronic expansion valve gradually closes to a minimum effective opening not lower than the current operating condition according to the battery inlet coolant temperature.

[0010] Preferably, when the temperature range has been reached and the battery still requires cooling, the passenger compartment electronic expansion valve is configured to either execute an evaporator superheat closed-loop or maintain its current opening, based on the first or second valve position of the passenger compartment electronic expansion valve and the superheat margin. The battery electronic expansion valve is also configured to execute a battery inlet coolant temperature closed-loop, a compressor suction superheat closed-loop, or maintain its current opening. When the temperature range has been reached and the battery reaches the requested temperature, the passenger compartment electronic expansion valve is configured to execute an evaporator superheat closed-loop, and the battery electronic expansion valve is gradually closed to the minimum effective opening according to the battery inlet coolant temperature.

[0011] Preferably, when the actual evaporator temperature is not higher than the low-temperature protection threshold, the low-temperature protection mode takes precedence over other control modes; in the low-temperature protection mode, the passenger compartment electronic expansion valve performs the evaporator low-temperature protection closed loop, and the battery electronic expansion valve performs the compressor suction superheat closed loop; the low-temperature protection mode uses an exit threshold, exit hysteresis, and minimum dwell time, and when the exit conditions are met, the target control mode is re-determined in the order of low-temperature protection, passenger compartment temperature zone, battery cooling requirements, valve position range, and superheat margin.

[0012] Preferably, the evaporator target temperature is calculated based on a reference target temperature and at least one operating condition correction, or obtained from an operating condition index parameter table; at least one of the low temperature protection threshold, valve position range threshold, minimum effective opening, superheat threshold, and water temperature hysteresis is indexed based on at least one of the following: driving conditions or charging conditions, ambient temperature, cooling priority, and heat load level.

[0013] Preferably, when two branches are engaged simultaneously, the battery electronic expansion valve and the passenger compartment electronic expansion valve are initialized to the first simultaneous engagement opening degree and the second simultaneous engagement opening degree, respectively; when one branch is running first and the other branch is added later, the corresponding access opening degree is selected for the later branch according to the first running branch and the battery cooling requirement level, and a change rate limit is applied to the opening command of the later branch.

[0014] In one example calibration: when both branches are engaged simultaneously, the initial opening of the battery electronic expansion valve is 200 steps, and the initial opening of the passenger compartment electronic expansion valve is 120 steps; when the battery branch is engaged alone, the initial opening of the battery electronic expansion valve is 200 steps; when the passenger compartment branch is engaged alone, the initial opening of the passenger compartment electronic expansion valve is 150 steps; when the passenger compartment branch operates first and the battery branch is added later, the battery electronic expansion valve openings corresponding to high and low battery cooling requirements are 220 steps and 160 steps, respectively; when the battery branch operates first and the passenger compartment branch is added later, the passenger compartment electronic expansion valve openings corresponding to high and low battery cooling requirements are 90 steps and 140 steps, respectively.

[0015] In one example calibration: when the compressor suction superheat is not less than 5K and the evaporator superheat is not less than 2K, the superheat margin is considered sufficient; when the compressor suction superheat is less than 4K or the evaporator superheat is less than 1K, the superheat margin is considered insufficient; when the battery electronic expansion valve opening is not less than 125 steps, it enters the large opening branch; when the battery electronic expansion valve opening is less than 110 steps, it exits the large opening branch; the water temperature hysteresis of the battery inlet coolant temperature is 2℃; when the actual evaporator temperature is not higher than 2℃, it enters the low temperature protection mode.

[0016] Preferably, when the control authority is switched from one closed loop to another, the integral state of the authorized controller is recalculated based on the current opening degree of the electronic expansion valve, and the disauthorized controller is frozen in its integral state or tracks the current opening degree to achieve a seamless switching; the opening command of the electronic expansion valve also undergoes physical limiting, minimum effective opening limit, rate of change limit and anti-integral saturation processing.

[0017] Preferably, it also includes: performing validity checks, filtering, and message timeout judgments on temperature, pressure, superheat, and valve position signals; identifying valve jamming or loss of synchronization based on the deviation between the valve command opening and the actual feedback opening; performing at least one degraded action among freezing the most recent effective control value, adopting a preset safe opening, switching to single-branch control, and limiting the compressor capacity when the sensor fails, the signal exceeds the limit, the message times out, or the valve executes abnormally; exiting the degraded state after the fault signal meets the recovery criteria; and recording the mode number, the first trigger condition, and key state variables before and after the mode switch.

[0018] A dual electronic expansion valve refrigerant distribution control system based on a hierarchical state machine is characterized by comprising: a signal processing module for acquiring and verifying the actual evaporator temperature, the target evaporator temperature, the battery inlet coolant temperature, the battery requested inlet coolant temperature, the compressor suction superheat, the evaporator superheat, and the current opening degree of the two electronic expansion valves; a demand arbitration module for generating passenger compartment temperature control requirements, battery cooling requirements, and operating condition indexes; a supervisory state machine for determining a target control mode based on low-temperature protection, passenger compartment temperature zone, battery cooling requirements, valve position range, and superheat margin; and an execution control module for distributing control actions to the two electronic expansion valves according to the target control mode and outputting opening commands; wherein the system is configured to execute any of the aforementioned dual electronic expansion valve refrigerant distribution control methods based on a hierarchical state machine.

[0019] A vehicle includes a compressor, a condenser, a passenger compartment evaporator branch, a power battery cooler branch, a passenger compartment electronic expansion valve, a battery electronic expansion valve, and a controller, characterized in that the controller includes the aforementioned control system.

[0020] An electronic controller includes a processor and a memory, characterized in that the memory stores a computer program, which, when executed by the processor, implements any of the above-mentioned dual electronic expansion valve refrigerant distribution control methods based on a hierarchical state machine.

[0021] A computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements any of the above-mentioned dual electronic expansion valve refrigerant distribution control methods based on a hierarchical state machine.

[0022] The working principle and beneficial effects of this invention are as follows: This invention uses a supervisory state machine to uniformly allocate the control objectives of the two electronic expansion valves and explicitly handle the coupling relationship between the two branches, thereby overcoming problems such as refrigerant contention and branch oscillation that are easily caused by independent control. At the same time, it switches between temperature control and superheat safety control as needed, prioritizing superheat safety while meeting temperature regulation requirements, avoiding risks such as insufficient suction superheat, evaporator frosting, and unstable heat exchange, and improving the system's operational safety and heat exchange stability.

[0023] This application embodiment effectively reduces frequent control mode switching and refrigerant flow mutations and suppresses mode jitter by using hysteresis, holding zone and gradual closing strategies; by selecting the branch access opening degree, limiting the rate of change and tracking the controller integral state, it reduces the intake state impact when two branches are added one after the other, and achieves bumpless switching during the branch switching process.

[0024] The embodiments of this application can improve the diagnosability and failure safety of embedded software through signal validity checks, timeout judgments, degradation status, and mode logs; and coordinate between passenger cabin comfort and power battery thermal safety, taking into account comfort, thermal safety, and energy efficiency, thereby improving system stability and responsiveness; the control structure is modular, and can be adapted to different vehicle models and cooling systems through threshold and minimum opening calibration, reducing calibration and porting costs and enhancing versatility and engineering applicability. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0026] Figure 1 This is a schematic diagram of the dual electronic expansion valve coordinated refrigerant distribution control system and refrigeration circuit of the present invention.

[0027] Figure 2 This is a flowchart of the nine-mode determination process based on evaporator temperature zoning in this invention.

[0028] Among them, 100—operating condition and target input; 200—signal processing module; 300—monitoring state machine; 410—crew compartment valve controller; 420—battery valve controller; 500—actuator module; 511—crew compartment electronic expansion valve; 512—battery electronic expansion valve; 600—refrigeration circuit and heat load object; 610—compressor; 611—crew compartment evaporator; 612—battery cooler; 620—condenser / liquid storage assembly. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. Obviously, the embodiments described are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0030] Examples of embodiments of the present invention Figure 1 As shown, the refrigeration circuit and heat load object 600 include a compressor 610, a condenser / liquid receiver assembly 620, a passenger compartment electronic expansion valve 511, a battery electronic expansion valve 512, a passenger compartment evaporator 611, and a battery cooler 612. High-pressure liquid refrigerant is distributed to two parallel throttling branches after passing through the condenser / liquid receiver assembly 620, and after heat exchange, it converges on the low-pressure side and returns to the compressor 610.

[0031] The control system includes operating condition and target input 100, signal processing module 200, monitoring state machine 300, passenger compartment valve controller 410, battery valve controller 420, and execution module 500. The monitoring state machine 300 outputs mode numbers and control authority allocation results based on the driving or charging conditions, target temperature, feedback signals, valve position status, and the execution module 500 accordingly controls the passenger compartment electronic expansion valve 511 and the battery electronic expansion valve 512. Table 1 shows the main variables used in this embodiment and their physical meanings, as follows: Table 1. Main Variables and Their Physical Meanings: When using Ne and Nb for state determination, the actual valve opening is preferred; when the actuator does not provide position feedback, the estimated valve opening value after out-of-step compensation can be used. The controller stores both the valve opening command and the actual feedback opening for deviation diagnosis.

[0032] Compressor suction superheat SH s It can be determined by the following formula: SH s = T suc - T sat ( p suc (1); In the formula, T suc This refers to the compressor suction temperature. p suc This refers to the compressor's suction pressure. T sat ( p suc () represents the refrigerant saturation temperature corresponding to the intake pressure.

[0033] The universal incremental control output of the two electronic expansion valves can be expressed as: u j ( k ) = sat{ u j ( k - 1) + Δ u j [ e ( k )]}, j ∈ { e , b} (2); In the formula, the discrete control period, the first... k One control moment, e (k ) is the first k The control error at any given moment, specifically which error it is, is determined by the current supervisory state machine mode. Δ u j It can be generated by a proportional-integral-derivative controller, a proportional-integral controller, or a calibrated equivalent controller, where sat(·) represents the physical limit of the opening; different modes change the error variable, the authorized actuator, and the valve that needs to be held, without limiting a single controller structure. u j ( k ) is the first j The valve in the first k The valve opening command at a given moment, Δ u j [ e ( k )] is the first j The valve's opening increment command in this cycle relative to the previous cycle is determined by the error. e ( k This is calculated by the controller. j=e Represents the evaporator branch in the crew compartment; j=b This represents the battery cooler branch.

[0034] The supervisory state machine first divides the temperature zones based on Te and Te,tar: when Te > Te,tar, the passenger compartment is not yet in the temperature zone, corresponding to modes 1 to 4; when the low-temperature protection threshold < Te ≤ Te,tar, the passenger compartment has reached the temperature zone, corresponding to modes 5 to 8; when Te is not higher than the low-temperature protection threshold, it is in the low-temperature protection zone, corresponding to mode 9. In a driving example, Te,tar is 6℃ and the low-temperature protection threshold is 2℃. Te,tar is not a fixed constant, but can be indexed from the target temperature group based on driving or charging conditions, ambient temperature, cooling priority, and heat load level, or it can be obtained by superimposing the operating condition correction amount on the reference target temperature and subjecting it to upper and lower limit constraints. As shown in Table 2, the correspondence between control modes and the action of the dual electronic expansion valves is as follows: Table 2. Correspondence between nine control modes and dual electronic expansion valve actions: In an example calibration, when both branches are engaged simultaneously, Nb is initialized to 200 steps and Ne to 120 steps; when the battery branch is engaged alone, Nb is initialized to 200 steps; when the passenger compartment branch is engaged alone, Ne is initialized to 150 steps. If the passenger compartment branch operates first and then the battery branch is added, the access degree of Nb can be 220 steps and 160 steps under high battery demand and low demand conditions, respectively; if the battery branch operates first and then the passenger compartment branch is added, the access degree of Ne can be 90 steps and 140 steps under high battery demand and low demand conditions, respectively. All access degrees are example calibration values ​​and should be used in conjunction with rate of change limits.

[0035] The starting or connection opening of the above-mentioned branch is different from the initial value of the controller output when switching between fault-safe and normal modes: when switching to normal mode, the effective valve position before the switch is inherited first and integral state tracking is performed; the fault-safe opening is determined by an independent degradation parameter table.

[0036] The system periodically calculates temperature deviation, superheat margin, and valve position range, and performs demand arbitration between modes 1 to 8; in any normal mode, as long as the low temperature protection condition is met, it will preferentially enter mode 9. To avoid uncertain results when multiple conditions exceed the threshold in the same cycle, the decision order is fixed as "low temperature protection - crew compartment temperature zone - battery water temperature requirement - valve position range - superheat margin".

[0037] To avoid frequent switching near the threshold, each criterion employs an entry threshold, an exit threshold, and a hold zone. For example, when SHs ≥ 5K and SHe ≥ 2K, the superheat margin is considered sufficient; when SHs < 4K or SHe < 1K, the superheat is considered insufficient. When Nb ≥ 125 steps, the system enters the large-opening branch; when Nb < 110 steps, it exits the branch, and the original branch is maintained from steps 110 to 125. When Tb,in ≤ Tb,req, the system enters the temperature-reaching state; only when Tb,in > Tb,req + 2℃ does it return to the high-demand state. The above values ​​are calibration values ​​for an example operating condition and can be adjusted according to the operating condition index based on system volume, refrigerant type, valve characteristics, and heat exchanger capacity. As shown in Table 3: Table 3. Correspondence between multi-level hysteresis, exit threshold and hold region: The first and second valve position regions of the electronic expansion valve in the crew compartment adopt parameterized boundaries Ne,L and Ne,H, where Ne,L < Ne,H; when Ne is between the two, the original valve position branch is maintained. Different threshold groups can be used for different operating conditions to avoid mixing values ​​from different versions or different operating conditions with the same criterion.

[0038] In addition to numerical hysteresis, the supervisory state machine can also set condition confirmation time and minimum mode dwell time. When control switches between temperature closed loop, superheat closed loop, and hold state, the integral term of the newly authorized controller is recalculated based on the current valve position, and the deauthorized controller is frozen or tracks the current valve position; the electronic expansion valve command is subject to rate of change limitation to reduce refrigerant flow abrupt changes caused by mode switching and branch connection.

[0039] In each control cycle, the controller executes the following sequentially: acquires vehicle and thermal management system signals and performs validity checks and filtering; generates evaporator target temperature, battery requested inlet coolant temperature, and operating condition index based on driving or charging conditions; determines the target mode according to the priority order of low temperature protection, passenger compartment temperature zone, battery water temperature requirement, valve position range, and superheat margin; assigns control rights to the two electronic expansion valves; and outputs valve commands after limiting amplitude, minimum effective opening, rate of change, and anti-integral saturation processing.

[0040] When operating in modes 1 to 4, if Te drops to Te,tar or below but remains above the cryogenic protection threshold, the system switches to modes 5 to 8 and re-determines the sub-mode. In any normal mode, as long as Te meets the cryogenic protection condition, mode 9 is prioritized. Mode 9 uses a calibrable exit threshold, exit hysteresis, and minimum dwell time. After meeting the exit condition, it does not always return to a specific mode but instead re-determines the current target mode according to a unified priority order to avoid inconsistencies between the protection recovery path and real-time requirements.

[0041] Figure 2 In this context, Tlow represents the low temperature protection threshold, and Te,tar represents the target evaporator temperature under the current operating conditions. The threshold, holding zone, and minimum effective opening can all be calibrated according to the operating conditions.

[0042] The crew compartment valve controller and battery valve controller can employ proportional-integral-derivative (PID) control, proportional-integral (PI) control, feedforward and feedback composite control, or model-based control. Taking PID control as an example, the target valve opening increment can be determined based on the deviation between the target quantity and the feedback quantity, as well as the integral of the deviation, and output after being processed by upper and lower opening limits, rate of change limits, and anti-integral saturation measures.

[0043] The control program can be executed by the vehicle thermal management controller, air conditioning controller, or independent domain controller. Sampling period, filter time constant, valve change rate, hysteresis threshold, minimum opening degree, condition confirmation time, and minimum mode dwell time can all be stored as operating condition index parameters. The control program can also be stored on a non-transitory computer-readable storage medium.

[0044] The following are typical operating condition examples: Example 1: Two branches start simultaneously. Nb and Ne start with initial values ​​of 200 and 120 steps respectively. When the occupant compartment has not reached the required temperature, the battery is under high demand, and the overheat margin is sufficient, it enters mode 1; if the overheat drops to a low threshold during the start-up phase, it switches to mode 2 and maintains the occupant compartment valve; if Nb further enters the small opening zone, it switches to mode 3; if Te reaches Te,tar first, it switches to the already reached temperature zone and re-determines mode 5 to mode 8.

[0045] Example 2: The crew compartment branch operates first. Ne can be started in 150 steps; when the battery branch is added subsequently, the battery valve opening is selected according to the battery demand level, for example, 220 steps for high demand and 160 steps for low demand, and the valve position change rate is limited. When the addition of the branch causes a decrease in superheat, the monitoring state machine switches from mode 1 to mode 2; when the battery water temperature reaches the requested value first, it enters mode 4 or mode 8 depending on whether the crew compartment has reached the required temperature.

[0046] Example 3: The battery branch operates first. Nb can be started in 200 steps; subsequently, when the passenger compartment cooling is added, the passenger compartment valve opening is selected according to the battery demand level, for example, 90 steps for high demand and 140 steps for low demand, to differentiate the existing battery load. After the passenger compartment reaches the required temperature, the monitoring state machine allocates control between mode 5 and mode 7 according to the passenger compartment valve position range and superheat margin.

[0047] Example 4: Battery Temperature and Low Temperature Protection. When Tb,in ≤ Tb,req, if the passenger compartment has not reached the required temperature, mode 4 is entered; if the passenger compartment has reached the required temperature, mode 8 is entered. The battery valve closes to the minimum effective opening corresponding to the current operating condition according to the water temperature closed loop. High demand state is restored only when Tb,in is higher than the sum of Tb,req and water temperature hysteresis. In any normal mode, if Te is not higher than the low temperature protection threshold, mode 9 is entered.

[0048] The signal processing layer performs rationality checks, filtering, and message timeout judgments on temperature, pressure, superheat, and valve position signals. It also identifies valve jamming or loss of synchronization based on the continuous deviation between the commanded valve opening and the actual feedback opening. In the event of sensor failure, signal exceeding limits, message timeout, or abnormal valve execution, the controller enters an independent degraded state, which can freeze the most recent effective control value, adopt a preset safe opening, switch to single-branch control, or limit compressor capacity. Once the fault signal meets the recovery threshold and recovery confirmation time, the normal mode judgment is re-executed. The mode log records the mode before and after the switch, the first trigger condition, key variables, and timestamps to support calibration tracking and fault diagnosis.

[0049] The control strategy can be verified step-by-step at the model-in-the-loop, software-in-the-loop, hardware-in-the-loop, bench, and vehicle levels. Verification scenarios should include at least nine modes' accessibility and mutual exclusion, simultaneous start-up of two branches, sequential branch addition, sudden demand changes, battery temperature-controlled reversal, low-temperature protection, compressor capacity limitations, sensor latency, message loss, and valve position limiting. Evaluation metrics may include temperature deviation, intake superheat boundary, number of mode switching cycles, valve position change rate, branch addition transients, and system energy consumption; specific limits will be determined by project requirements.

[0050] This embodiment uses two parallel evaporator branches as an example, but the supervisory arbitration concept of this invention can also be extended to thermal management systems with three or more refrigerant branches. Temperature thresholds, superheat thresholds, valve position zones, and the number of modes can be adjusted according to the specific system; the passenger compartment temperature control requirements can also be determined by the compartment temperature, outlet air temperature, evaporator temperature, humidity, or a combination thereof; the battery temperature control requirements can be determined by the cell temperature, inlet coolant temperature, outlet coolant temperature, temperature difference, or a combination thereof.

[0051] The above embodiments are illustrative of the present invention and not intended to limit it. Any equivalent substitutions, parameter adjustments, module combinations, or control logic modifications made within the spirit and principles of the present invention should fall within the protection scope of the present invention. The embodiments of the present invention are not limited to the above examples; any modifications, alterations, substitutions, combinations, or simplifications made without departing from the spirit and principles of the present invention should be considered equivalent substitutions and should be included within the protection scope of the present invention.

Claims

1. A refrigerant distribution control method based on a hierarchical state machine using dual electronic expansion valves, applied to a vehicle thermal management system, wherein the vehicle thermal management system includes a passenger compartment evaporator branch and a power battery cooler branch sharing a compressor and a common intake port, wherein the passenger compartment evaporator branch is equipped with a passenger compartment electronic expansion valve, and the power battery cooler branch is equipped with a battery electronic expansion valve. The method includes the following steps: The system acquires the actual evaporator temperature, the target evaporator temperature under current operating conditions, the battery inlet coolant temperature, the battery requested inlet coolant temperature, the compressor suction superheat, the evaporator superheat, and the current opening of the two electronic expansion valves. Temperature stratification is performed based on the actual evaporator temperature, battery cooling requirements are identified based on the battery inlet coolant temperature, valve position range is determined based on the current opening degree, and superheat margin is determined based on the compressor suction superheat and the evaporator superheat. The supervisory state machine determines the target control mode from multiple control modes based on the temperature zone, battery cooling requirements, valve position range, and overheat margin. The supervisory state machine performs mode determination in the order of low temperature protection, passenger compartment temperature zone, battery cooling requirements, valve position range, and overheat margin. The temperature zone includes at least the unreached temperature zone where the actual evaporator temperature is higher than the evaporator target temperature, the reached temperature zone where the actual evaporator temperature is not higher than the evaporator target temperature but higher than the low temperature protection threshold, and the low temperature protection zone where the actual evaporator temperature is not higher than the low temperature protection threshold. According to the target control mode, control actions are assigned to the passenger compartment electronic expansion valve and the battery electronic expansion valve respectively in the evaporator temperature closed loop, battery inlet coolant temperature closed loop, compressor suction superheat closed loop, evaporator superheat closed loop, valve position holding and gradual closing. Based on the assigned control actions, the system generates and outputs opening commands for the two electronic expansion valves to coordinate the refrigerant flow between the two branches.

2. The dual electronic expansion valve refrigerant distribution control method based on hierarchical state machines according to claim 1, characterized by, The battery cooling demand is determined using a hysteresis state: when the battery inlet coolant temperature is not higher than the battery requested inlet coolant temperature, it enters the temperature-reaching state; when the battery inlet coolant temperature is higher than the sum of the battery requested inlet coolant temperature and the water temperature hysteresis, it returns to the high-demand state; and within the holding zone between the two, it maintains the original battery cooling demand state.

3. The layered state machine based dual electronic expansion valve refrigerant distribution control method according to claim 1, characterized by, The superheat margin and the valve position range are respectively formed into holding zones using entry thresholds and exit thresholds; when the monitored quantity is within the corresponding holding zone, the monitoring state machine maintains the original control mode or the original decision branch. When the mode switching conditions continue to meet the condition confirmation time and the current mode reaches the minimum dwell time, the corresponding mode switch is executed.

4. The dual electronic expansion valve refrigerant distribution control method based on hierarchical state machines according to claim 1, characterized by, In the under-temperature region, when the battery has cooling demand, the battery electronic expansion valve is in the large opening degree region and the superheat margin is sufficient, the passenger cabin electronic expansion valve is controlled to perform evaporator temperature closed loop and the battery electronic expansion valve is controlled to perform compressor suction superheat closed loop; when the battery has cooling demand, the battery electronic expansion valve is in the large opening degree region and the superheat margin is insufficient, the current opening degree of the passenger cabin electronic expansion valve is maintained and the battery electronic expansion valve is controlled to perform compressor suction superheat closed loop; when the battery electronic expansion valve enters the small opening degree region, the passenger cabin electronic expansion valve is controlled to perform evaporator superheat closed loop and the current opening degree of the battery electronic expansion valve is maintained; when the battery reaches the requested temperature, the passenger cabin electronic expansion valve is controlled to perform evaporator superheat closed loop and the battery electronic expansion valve is gradually closed according to the battery inlet cooling liquid temperature to not less than the minimum effective opening degree corresponding to the current working condition.

5. The method of claim 1, wherein, In the reached-temperature region and when the battery still has cooling demand, according to the first valve position region or the second valve position region of the passenger cabin electronic expansion valve and the superheat margin, the passenger cabin electronic expansion valve is controlled to perform evaporator superheat closed loop or maintain the current opening degree, and the battery electronic expansion valve is controlled to perform battery inlet cooling liquid temperature closed loop, compressor suction superheat closed loop or maintain the current opening degree; in the reached-temperature region and when the battery reaches the requested temperature, the passenger cabin electronic expansion valve is controlled to perform evaporator superheat closed loop and the battery electronic expansion valve is gradually closed according to the battery inlet cooling liquid temperature to the minimum effective opening degree.

6. The method of claim 1, wherein, When the actual evaporator temperature is not higher than the low-temperature protection threshold value, the low-temperature protection mode is prior to other control modes; In the low-temperature protection mode, the passenger cabin electronic expansion valve is controlled to perform evaporator low-temperature protection closed loop and the battery electronic expansion valve is controlled to perform compressor suction superheat closed loop; the low-temperature protection mode adopts an exit threshold value, an exit hysteresis and a minimum residence time, and when the exit condition is met, the target control mode is determined again in the order of low-temperature protection, passenger cabin temperature region, battery cooling demand, valve position region and superheat margin.

7. The method of claim 1, wherein, The evaporator target temperature is calculated according to a reference target temperature and at least one working condition correction amount, or is obtained from a working condition index parameter table; at least one of the low-temperature protection threshold value, the valve position region threshold value, the minimum effective opening degree, the superheat threshold value and the water temperature hysteresis amount is indexed according to at least one of driving working condition or charging working condition, ambient temperature, refrigeration priority and heat load level.

8. The method of claim 1, wherein, When the two branches are simultaneously put into operation, the battery electronic expansion valve and the passenger cabin electronic expansion valve are initialized to a first simultaneous put-in opening degree and a second simultaneous put-in opening degree; when one branch is operated first and the other branch is added later, according to the first operated branch and the battery cooling demand level, a corresponding access opening degree is selected for the later added branch, and a change rate limit is applied to the opening degree command of the later added branch.

9. The method of claim 1, wherein, When the control right is switched from one closed loop to another, the integral state of the gaining controller is calculated according to the current opening degree of the electronic expansion valve, and the losing controller is frozen or tracked to realize the non-disturbance switching; the opening degree of the electronic expansion valve is also subjected to physical limiting, minimum effective opening degree limiting, change rate limiting and anti-integral saturation processing.

10. The method of claim 1, wherein, Further comprising: The temperature, pressure, superheat and valve position signals are subjected to validity check, filtering and message timeout judgment, and the valve sticking or step loss is identified according to the deviation between the valve command opening degree and the actual feedback opening degree; when the sensor fails, the signal is out of limit, the message is timed out or the valve executes abnormally, at least one of the following degradation actions is performed: freezing the latest effective control quantity, adopting a preset safe opening degree, switching to single branch control and limiting the compressor capacity; the degradation state is exited after the fault signal meets the recovery criterion; and the mode number, the first triggering condition and the key state variable before and after the mode switching are recorded.

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