Dual-state machine switching regulation and control method based on hot gas bypass and heat pump mode

Abstract

The invention discloses a dual-state machine switching regulation and control method based on a hot gas bypass and heat pump mode, and the switching regulation and control method comprises the following steps: starting an air conditioning system, and switching the air conditioning system to a corresponding state machine for operation based on switching conditions of a hot gas bypass state machine and a heat pump state machine; the running state machine firstly enters an initialized state and judges whether a waiting state skipping condition is met or not, if yes, the state machine skips to enter the waiting state, otherwise, whether a pre-starting condition is met or not is further judged, if yes, the state machine enters the pre-starting state, and if not, the state machine keeps running in the initialized state; the waiting state is designed in the hot gas bypass mode state machine and the heat pump mode state machine, so that the hot gas bypass state machine and the heat pump state machine are linked during operation, unnecessary compressor shutdown in the air conditioning system is avoided, the two state machines can be naturally switched, the comfort of passengers is improved, and the service life of the air conditioning system is prolonged. And a part of loss of energy consumption is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automobile thermal management, and particularly relates to a double-state machine switching control method based on hot gas bypass and heat pump mode. BACKGROUND

[0002] With the rapid popularization of new energy vehicles, automobile consumers have higher and higher requirements for passenger cabin comfort. How to improve passenger comfort while taking into account energy consumption puts higher requirements on the whole vehicle thermal management system. At present, some vehicle models on the market adopt a thermal management scheme of "refrigeration and dehumidification + heat pump + hot gas bypass". For example, in high temperature (such as an ambient temperature greater than 5℃), a refrigeration and dehumidification mode is adopted, in medium and low ambient temperature (such as an ambient temperature of -10~5℃), a heat pump mode is adopted, and in extremely low ambient temperature (such as an ambient temperature less than -10℃), a hot gas bypass mode is adopted. During use of the automobile air conditioner, as the ambient temperature changes, the working mode of the air conditioner will switch between the refrigeration & dehumidification, heat pump and hot gas bypass modes. In the switching process between the heat pump and hot gas bypass modes, the compressor of most vehicle models will stop, and after system conditions are met, such as refrigerant pressure balance or valve opening degree execution, the system can be switched to another mode. According to experience, this time usually reaches more than 10s. This strategy will first cause system jitter, the start and stop of the compressor will be obviously perceived by passengers, secondly, it will cause changes in the outlet air temperature, reducing the passenger heating comfort, and finally, the frequent start and stop of the compressor will also cause unnecessary increase in energy consumption. SUMMARY

[0003] The present application aims to provide a double-state machine switching control method based on hot gas bypass and heat pump mode, comprising a hot gas bypass state machine and a heat pump state machine, the double-state machine switching control method comprising the following steps: S1, starting the air conditioning system, based on the switching conditions of the hot gas bypass state machine and the heat pump state machine, switching the air conditioning system to the corresponding state machine for operation; S2, the operating state machine first enters an initialization state, and judges whether the waiting state jump condition is met, if yes, the state machine jumps into the waiting state, otherwise, it is further judged whether the pre-starting condition is met, if yes, the state machine enters the pre-starting state, otherwise, the initialization state is kept running; S3, after the current state machine jumps into the waiting state, it is judged whether the running state condition is met, if yes, the current state machine enters the running state to control the air conditioning system to run, otherwise, it is further judged whether the switching condition of the remaining state machine is met, if yes, the air conditioning system is switched to the corresponding state machine for operation, otherwise, the original state machine reenters the initialization state, realizing switching control between multiple state machines.

[0004] As preferred, the switching condition of the hot gas bypass state machine in step S1 is that the ambient temperature is less than a preset value one, the switching condition of the heat pump state machine is that the ambient temperature is less than a preset value two, and the preset value one is less than the preset value two.

[0005] As preferred, it is characterized in that, after the heat pump state machine enters the pre-starting state in step S2, it is determined again whether the air conditioning system still satisfies the running state condition of the current state machine, if yes, the heat pump state machine enters the running state after a preset time one, otherwise, it returns to the initial state.

[0006] As preferred, the pre-starting condition of the hot gas bypass state machine entering the pre-starting state in step S2 includes condition one and condition two, the priority of condition one is higher than that of condition two, and the determination of the hot gas bypass state machine entering the pre-starting state includes the following sub-steps: S21, it is determined whether the air conditioning system satisfies condition one, if yes, the hot gas bypass state machine enters the staying state from the initial state, otherwise, the initial state is maintained; S22, the hot gas bypass state machine entering the staying state further determines whether condition two is satisfied, if yes, it enters the pre-starting state, otherwise, the staying state is maintained.

[0007] As preferred, condition one of the hot gas bypass state machine entering the pre-starting state is whether the air conditioning system satisfies the switching condition of the hot gas bypass state machine, and condition two of the hot gas bypass state machine entering the pre-starting state is whether the high pressure and the low pressure of the air conditioning system reach a balance threshold and the hot gas bypass state machine has no fault.

[0008] As preferred, after the hot gas bypass state machine enters the pre-starting state in step S2, the following sub-steps are included: A1, it is determined whether the air conditioning system still satisfies the running state condition of the current state machine, if yes, the hot gas bypass state machine enters the pressure building state after a preset time two; A2, after the hot gas bypass state machine enters the pressure building state, the air conditioning system is controlled to build pressure, and it is determined based on the pressure building condition, if the air conditioning system satisfies the pressure building condition, the current state machine enters the running state to control the air conditioning system to run, otherwise, it enters the shutdown state to control the air conditioning system to shut down; A3, after the air conditioning system enters the shutdown state in step A2, the current state machine enters the pressure balance state after a preset time three to balance the high pressure and the low pressure of the air conditioning system, and then enters the pressure flushing state after a preset time four to perform flushing processing, and then enters the pressure building state again after a preset time five to perform the pressure building processing, until the air conditioning system satisfies the pressure building condition to enter the running state.

[0009] As preferred, the pre-starting state, the pressure building state, the running state, the shutdown state, the pressure balancing state and the ramming state in the hot gas bypass state machine constitute parent nodes of the hot gas bypass state machine, and when the hot gas bypass state machine does not satisfy the running state condition, it directly enters the shutdown state from any state in the parent nodes.

[0010] As preferred, after the air conditioning system enters the shutdown state in step A1, the current state machine enters the pressure balancing state after a preset time three, and then it is judged whether the air conditioning system satisfies the delay condition or the pressure condition, if both are not satisfied, it is further judged whether the current state machine switching condition is satisfied, if not, it enters the initialization state, otherwise, it enters the stay state to control the air conditioning system to be closed.

[0011] As preferred, the hot gas bypass state machine entering the running state from the waiting state comprises the following sub-steps: S31, it is judged whether the air conditioning system still satisfies the running state condition of the current state machine, if yes, it performs the ramming state ramming processing from the waiting state; S32, after the ramming processing, it enters the pressure building state from the ramming state after a preset time five, and performs the pressure building processing in a loop until the air conditioning system satisfies the pressure building condition to enter the running state, and controls the air conditioning system to be operated.

[0012] The present application has the following advantages: 1. The present application designs the waiting state in the hot gas bypass mode state machine and the heat pump mode state machine, so that the hot gas bypass state machine and the heat pump state machine are linked when running, unnecessary compressor shutdown in the air conditioning system is avoided, the two state machines can be switched naturally, passenger comfort is improved, and part of energy loss is avoided.

[0013] 2. The present application sets up the parent node of "non-protection node", so that when the current system condition does not satisfy the maintenance in the hot gas bypass mode, such as the air conditioning system environment temperature rising to the heat pump mode running interval, or the current heat management system executor exists a fault, such as the compressor fault, the state machine can enter the shutdown state in a program 1 running cycle, and the effect of timely protection is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a multi-state machine mutual switching flowchart in the embodiment of the present application; Figure 2 It is a heat pump state machine running flowchart in the embodiment of the present application; Figure 3 It is a hot gas bypass state machine running flowchart in the embodiment of the present application. DETAILED DESCRIPTION

[0015] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0016] Please refer to Figures 1 to 3 The present application provides a kind of based on hot gas bypass and heat pump mode dual state machine switching control method, in the system scheme, including three modes: refrigeration dehumidification mode, heat pump mode, hot gas bypass mode, each operating mode is correspondingly with respective state machine, air conditioning system is started, program will be according to current system environment, with the switching condition of each state machine proportioning judgment, including but not limited to ambient temperature etc., jump to the corresponding mode set.

[0017] In the state of air conditioning system opening, program will be according to current system environment change, including but not limited to ambient temperature change etc., jump between refrigeration dehumidification mode, heat pump mode and hot gas bypass mode.

[0018] Air conditioning system has respective operating state for different operating modes.

[0019] Heat pump mode state includes: initialization state one, pre-start state one, waiting state one, operating state one; Hot gas bypass mode state includes: initialization state two, pressure balance state, shutdown state, pre-start state two, pressure building state, flushing state, stay state, waiting state two, operating state two.

[0020] When air conditioning is closed, the state machine of three modes is in closed state, after air conditioning is started, program can only run in one mode, other modes are in closed state, such as when air conditioning runs in heat pump mode, each state of heat pump mode can jump to each other, but the state machine of refrigeration dehumidification mode and hot gas bypass mode is in initialization state. Figure 1 Briefly summarize the overall process of air conditioning system 3 mode jump.

[0021] Heat pump state machine executes the following logic (such as Figure 2 As shown): When air conditioning is started, and system environment including but not limited to ambient temperature condition etc. is satisfied, enter heat pump mode.

[0022] Among them, initialization state one, waiting state one, pre-start state one, operating state one, are the jump nodes of heat pump state machine mode state, in each node, current state machine can be assigned to air conditioning system state, so as to control air conditioning system to enter corresponding state operation.

[0023] The heat pump mode first enters the initialization state one node, in the initialization state one "system state = off" ("=" is the assignment operator, equivalent to updating the air conditioning system state to off, the same below). Initialization state one corresponds to two jump modes: Jump mode one: judge whether the system meets the waiting state jump condition, that is, "current mode == hot gas bypass mode" (the current mode can be judged according to a certain global variable in the state machine program running; "==" is the judgment operator, that is, whether the current mode is in the hot gas bypass mode, the same below), if the waiting state jump condition is judged to be true, the current state machine jumps to the waiting state, and in the waiting state "system state = off".

[0024] Jump mode two, judge whether the system environment meets the pre-starting condition of the current state machine, that is, the system current mode is in the off state or the refrigeration and dehumidification mode state, and the system environment temperature and other conditions meet the jump to the heat pump mode, then the current state machine jumps from the initialization state one to the pre-starting state one, in the pre-starting state one "system state = pre-starting state", if the waiting state jump condition and the pre-starting condition are not established, then maintain the current state. Figure 2 The jump direction numbers 1 and 2 represent the priority of state jump, and the priority of number 1 is greater than that of number 2, the same below.

[0025] In actual application scenarios, if the current running mode of the air conditioning system is the refrigeration and dehumidification mode, the heat pump state machine will stay in the initialization state one node, waiting for the air conditioning system environment to meet the pre-starting condition of the heat pump state machine, including but not limited to the environment temperature reduction, the heating demand increase, and the system unable to run stably in the refrigeration and dehumidification mode (evaporator temperature protection, etc.), so it is necessary to enter the heat pump mode, and the heat pump mode state machine node will jump from the initialization state one to the pre-starting state one. Jumping into the pre-starting state one node is to let the expansion valve and other actuators run to the corresponding position, to prepare for starting the compressor in the running state one stage (if the expansion valve and other actuators are not opened before starting the compressor, it may cause damage to the system). If the current running mode of the air conditioning system is the hot gas bypass mode, the heat pump state machine will jump to the waiting state one node, waiting for the heat pump state machine switching condition to be met, including but not limited to the environment temperature rising, and the system unable to run stably in the hot gas bypass mode, so it is necessary to enter the heat pump mode. At this time, the expansion valve and other actuators are already in the open state, so the heat pump mode state machine node can jump from the waiting state one to the running state one directly, avoiding the waiting time of the compressor shutdown.

[0026] For the heat pump state machine pre-start state one node, firstly determine whether the current mode of the air conditioning system is still in heat pump mode. If the system environment conditions are not met, resulting in "current mode ~= heat pump mode", then jump back to initialization state one. Secondly, if the current system environment conditions are met and the system remains in heat pump mode, then after a period of time (i.e., preset time one), such as 10 seconds (during which the actuators of the air conditioning system will have corresponding actions, such as the expansion valve and other actuators will move to the corresponding positions), the heat pump mode state machine node will jump from pre-start state one to running state one, in which "system state = running".

[0027] For the heat pump state machine in waiting state one node, first determine whether the system environment meets the switching conditions of the heat pump state machine (i.e., causing the system to switch from hot gas bypass mode to heat pump mode). If it does, the heat pump state machine directly switches from waiting state one to running state one. Secondly, if it switches from hot gas bypass mode to cooling and dehumidification or turns off the air conditioner at this time, the heat pump state machine will switch back to initialization state one, and the heat pump state machine will be in the off state.

[0028] For the heat pump state machine, state one is the stable operating state of heat pump mode. If the air conditioning system does not meet the switching conditions of the current state machine, resulting in "current mode ~= heat pump mode", then the current state machine jumps to initialization state one.

[0029] When the compressor is in the off or pre-start state in heat pump mode, it is prohibited from starting and its speed is 0.

[0030] The hot gas bypass state machine executes the following logic (e.g.) Figure 3 (as shown) When the air conditioner is turned on, if the system environment (including but not limited to ambient temperature) meets the switching conditions of the hot gas bypass state machine, the air conditioning system will enter the hot gas bypass mode.

[0031] The initialization state two, the waiting state two, the stay state, the pressure balance state, the shutdown state, the pre-starting state two, the building pressure state, the running state two and the flushing state are the jump nodes of the hot gas bypass state machine, and the state of the air conditioning system is assigned in each node. The non-protection node (SVIHP) is a parent node of the hot gas bypass mode state machine, and the pressure balance state, the shutdown state, the pre-starting state two, the building pressure state, the running state two and the flushing state are child nodes of the non-protection node (SVIHP). The non-protection node (SVIHP) parent node starts to execute from the pre-starting state two. The parent node of the non-protection node is mainly set to achieve the effect of timely protection when the current system condition does not meet the condition of maintaining the hot gas bypass mode, such as the ambient temperature of the air conditioning system rising to the hot pump mode running interval, or the current thermal management system executor has a fault, such as a compressor fault. The state machine can enter the shutdown state within one program running cycle.

[0032] The starting point of the hot gas bypass state machine is the initialization state two, and in the initialization state two, the system state is closed. In the closed state, the thermal management system related executor is not controlled by the hot gas bypass mode logic. If the system meets the waiting state jump condition, i.e., the current mode is equal to the hot pump mode, the system jumps to the waiting state two, and in the waiting state two, the system state is closed. Secondly, if the current mode of the system is in the air conditioning system closed state or the refrigeration dehumidification mode, and the environmental temperature and other conditions meet the condition one of the hot gas bypass mode pre-starting condition, the system jumps from the initialization state two to the stay state. Otherwise, the hot gas bypass mode state machine always stays in the initialization state two node.

[0033] When the system mode jumps from the air conditioning system closed state or the refrigeration dehumidification mode to the hot gas bypass mode, the current state machine jumps to the stay state. If the system meets the condition two in the pre-starting condition, i.e., the high pressure and the low pressure of the system reach the balance threshold (the balance threshold is usually between 0-6bar, which is different according to the difference of the thermal management system), such as | high pressure-low pressure | < 2bar (bar, a unit of air pressure, equivalent to one atmosphere), and the current thermal management system executor has no fault, such as a compressor fault, the current state machine jumps to the pre-starting state two. In the pre-starting state two, the system state is in the pre-starting state, and in the pre-starting state two, the executor of the thermal management system has corresponding actions, such as the expansion valve and other executors running to the preset position.

[0034] After waiting for a period of time (the preset time two) in the pre-starting state two, such as 20s, the system jumps to the building pressure state, and in the building pressure state, the system state is in the building pressure. The compressor starts to run to increase the high pressure and the low pressure of the system.

[0035] If the system high pressure and low pressure reach the target threshold (build pressure condition, and the target threshold is usually between 3-30bar, different according to the difference of thermal management system), such as high pressure > 9bar, low pressure > 4bar, then the build pressure is successful; otherwise, if the target high and low pressure threshold is not reached within 30s, then the build pressure fails.

[0036] When the build pressure is successful, the node build pressure jumps to the running state two, "system state = running". The running mode is the symbol of the stable running of the hot gas bypass mode, and the actuators of the thermal management system will perform corresponding closed-loop control to maintain the stable operation of the system.

[0037] When the build pressure fails, the state machine jumps to the shutdown state, "system state = shutdown". In the shutdown state, the compressor stops running, and after a period of time (preset time three), such as 10s, it jumps from the shutdown state to the pressure balance state, balancing the high and low pressures in the air conditioning system, "system state = pressure balance". In this state, the compressor is still at 0 speed.

[0038] After a period of time (preset time four), such as 20s, the state machine jumps to the flushing state, "system state = flushing". In the flushing state, the compressor starts running, and the electronic expansion valve and other actuators will run to the specified position, further making the refrigerant more evenly distributed in the system.

[0039] After the compressor continues to run for a period of time (interval five), such as 60s, it returns to the build pressure state again from the flushing state.

[0040] In any child node of the SVIHP parent node, if the current system condition does not meet the requirement to maintain the hot gas bypass mode, such as the ambient temperature rises to the heat pump mode running interval, or the current thermal management system actuators have faults, such as compressor failure, then it directly jumps from any child node of the parent node to the shutdown state, and after a period of time (preset time three), such as 10s, it jumps to the pressure balance state. In the pressure balance state, if the delay condition is met, such as delay for 20s, or the system high pressure and low pressure reach the balance threshold, such as | high pressure - low pressure | < 2bar, then it jumps from the pressure balance state to the closed state, which is the stay state node. If the current mode does not meet the requirement to maintain the hot gas bypass mode, then it jumps back to the initialization state two node. If the current mode is still in the hot gas bypass mode, then it needs to wait for the thermal management system actuators to recover from the fault before it can jump to the pre-start state two again.

[0041] If the current mode of the system is the heat pump mode, and the system environment (including but not limited to the ambient temperature condition) meets the requirement to enter the hot gas bypass mode, then the hot gas bypass mode state machine directly jumps from the waiting state two node to the flushing state node, and after a period of time (preset time five), it enters the build pressure state.

[0042] Wherein, the compressor is prohibited to start and the rotating speed is 0 when the system state is initialization state, pre-starting state, shutdown state and pressure balance state.

[0043] Linkage of heat pump mode state machine and hot gas bypass mode state machine; The heat pump state machine and the hot gas bypass state machine are linked through the "waiting state one" and "waiting state two" nodes.

[0044] If the air conditioner is turned on and currently runs in the heat pump mode, the hot gas bypass mode state machine will jump from the initialization state two to the waiting state two and wait at this node. When the ambient temperature is reduced below the threshold, such as -10℃, the hot gas bypass mode state machine will jump from the waiting state two to the flushing state node directly, and the compressor can run in the flushing state. After the compressor runs for a period of time, it will jump to the pressure building state. Otherwise, if the state machine is executed according to the refrigeration and dehumidification mode, it will first enter the pre-starting state two node, and the compressor will stop running in the pre-starting state. The compressor will wait for a period of time (preset time five, such as 20s) at 0 rotating speed before entering the pressure building state. Therefore, the existence of the waiting state two node avoids the system entering the pre-starting state, that is, avoids unnecessary shutdown of the compressor.

[0045] If the air conditioner is turned on and currently runs in the hot gas bypass mode, the heat pump state machine will jump from the initialization state one to the waiting state one and wait at this node. When the ambient temperature is increased above the threshold, such as -10℃, the heat pump mode state machine will jump from the waiting state one to the running state one node directly, and the compressor can run normally in the running state. Otherwise, if the state machine is executed according to the refrigeration and dehumidification mode, it will first enter the pre-starting state one node, and the compressor will stop running in the pre-starting state. The compressor will wait for a period of time (preset time one, such as 10s) at 0 rotating speed before entering the running state one. Therefore, the existence of the waiting state one node avoids the system entering the pre-starting state, that is, avoids unnecessary shutdown of the compressor.

[0046] From the principle of thermal management system, when entering the heat pump mode or the hot gas bypass mode from the air conditioner off state or the refrigeration and dehumidification mode, the compressor needs to pass through the 0 rotating speed stage in theory due to the time consumption of the expansion valve and other actuators and the principle limitation of the refrigerant flow reversal. In general state machine design, the hot gas bypass mode and the heat pump mode can also use this conventional state machine jump design essentially, but the existence of the "waiting state one" and "waiting state two" nodes avoids this unnecessary compressor shutdown.

[0047] The above merely provides the preferred embodiment of the present application, and is not used to limit the present application, and any modification, equivalent replacement or improvement made in the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A dual-state machine switching control method based on hot gas bypass and heat pump mode, characterized in that, The double-state machine switching control method comprises the following steps: S1, starting the air conditioning system, and switching the air conditioning system to a corresponding state machine for operation based on switching conditions of the hot gas bypass state machine and the heat pump state machine; S2, the operating state machine first enters an initialization state, and determines whether a waiting state jump condition is met, if yes, the state machine jumps into the waiting state, otherwise, it is further determined whether a pre-starting condition is met, if yes, the state machine enters the pre-starting state, otherwise, the initialization state is maintained; S3, after the current state machine jumps into the waiting state, it is determined whether a running state condition is met, if yes, the current state machine enters a running state to control the air conditioning system to run, otherwise, it is further determined whether a switching condition of the remaining state machine is met, if yes, the air conditioning system is switched to the corresponding state machine for operation, otherwise, the original state machine re-enters the initialization state, thereby realizing switching control among multiple state machines.

2. The multi-state machine switching control method based on hot gas bypass and heat pump mode according to claim 1, wherein, In the step S1, the switching condition of the hot gas bypass state machine is that the ambient temperature is less than a preset value one, the switching condition of the heat pump state machine is that the ambient temperature is less than a preset value two, and the preset value one is less than the preset value two.

3. The multi-state machine switching control method based on hot gas bypass and heat pump mode of claim 1, wherein, In the step S2, after the heat pump state machine enters the pre-starting state, it is determined again whether the air conditioning system still meets the running state condition of the current state machine, if yes, the heat pump state machine enters the running state after a preset time one, otherwise, it returns to the initialization state.

4. The multi-state machine switching control method based on hot gas bypass and heat pump mode of claim 1, wherein, In the step S2, the pre-starting condition of the hot gas bypass state machine entering the pre-starting state comprises a condition one and a condition two, the priority of the condition one is higher than that of the condition two, and the determination of the hot gas bypass state machine entering the pre-starting state comprises the following sub-steps: S21, determining whether the air conditioning system meets the condition one, if yes, the hot gas bypass state machine enters a stay state from the initialization state, otherwise, the initialization state is maintained; S22, the hot gas bypass state machine entering the stay state further determines whether the condition two is met, if yes, it enters the pre-starting state, otherwise, the stay state is maintained.

5. The multi-state machine switching control method based on hot gas bypass and heat pump mode of claim 4, wherein, The condition one of the hot gas bypass state machine entering the pre-starting state is whether the air conditioning system meets the switching condition of the hot gas bypass state machine, and the condition two of the hot gas bypass state machine entering the pre-starting state is whether the high pressure and the low pressure of the air conditioning system reach a balance threshold and the hot gas bypass state machine is fault-free.

6. The multi-state machine switching control method based on hot gas bypass and heat pump mode of claim 1, wherein, In the step S2, after the hot gas bypass state machine enters the pre-starting state, the following sub-steps are included: A1, determining whether the air conditioning system still meets the running state condition of the current state machine, if yes, the hot gas bypass state machine enters a pressure building state after a preset time two; A2, after the hot gas bypass state machine enters the pressure building state, the air conditioning system is controlled to build pressure, and a determination is made based on a pressure building condition, if the air conditioning system meets the pressure building condition, the current state machine enters the running state to control the air conditioning system to run, otherwise, it enters a shutdown state to control the air conditioning system to shut down; A3, after the air conditioning system enters the stop state in the step A2, the current state machine enters the pressure balance state after a preset time three, balances the high and low pressure in the air conditioning system, and then enters the pressure flushing state from the pressure balance state after a preset time four to perform flushing processing. After the flushing processing, the system reenters the pressure building state from the pressure state after a preset time five to perform cyclic pressure building processing until the air conditioning system meets the pressure building condition to enter the running state.

7. The multi-state machine switching control method based on hot gas bypass and heat pump mode of claim 6, wherein, The pre-starting state, the pressure building state, the running state, the stop state, the pressure balance state, and the pressure flushing state in the hot gas bypass state machine constitute a parent node of the hot gas bypass state machine. When the hot gas bypass state machine does not meet the running state condition, it directly enters the stop state from any state in the parent node.

8. The multi-state machine switching control method based on hot gas bypass and heat pump mode of claim 6, wherein, After the air conditioning system enters the stop state in the step A1, the current state machine enters the pressure balance state after a preset time three, and then judges whether the air conditioning system meets the delay condition or the pressure condition. If neither condition is met, it further judges whether the current state machine switching condition is met. If not, it enters the initialization state, otherwise, it enters the stay state to control the air conditioning system to be closed.

9. The multi-state machine switching control method based on hot gas bypass and heat pump mode of claim 6, wherein, The hot gas bypass state machine entering the running state from the waiting state includes the following sub-steps: S31, judges whether the air conditioning system still meets the running state condition of the current state machine. If yes, it performs flushing processing from the flushing state; S32, after the flushing processing, it enters the pressure building state from the pressure state after a preset time five to perform cyclic pressure building processing until the air conditioning system meets the pressure building condition to enter the running state, and controls the air conditioning system to run.

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