阅读说明：本技术 一种适用火星着陆任务的系统抗冲击方法 (System impact resistance method suitable for Mars landing task ) 是由 赵宇 刘旺旺 徐李佳 郝策 王云鹏 陈尧 王晓磊 何健 李茂登 张琳 余志鸿 于 2021-09-17 设计创作，主要内容包括：一种适用火星着陆任务的系统抗冲击方法,包括继电器抗冲击、配平翼状态自主诊断及处理、触地开关状态自主诊断及处理；从火工品起爆前到起爆后,对继电器内的电磁线圈持续加电,以使得继电器正常工作；配平翼状态自主诊断及处理包括：在火工品起爆前,如采集到某路配平翼展开到位信号有效,则认为该路开关故障,后续不再使用该路信号；火工品起爆后若采集到一路及以上配平翼展开到位信号有效,则认为配平翼展开到位,否则认为配平翼未展开；触地开关状态自主诊断及处理包括：在触地前,如某路触地开关为触地状态,则认为该路触地开关状态故障,后续不再使用该路信号；触地后,根据剩余触地开关的状态判断是否触地。(A system impact-resistant method suitable for Mars landing tasks comprises relay impact resistance, trim wing state autonomous diagnosis and processing, and touchdown switch state autonomous diagnosis and processing; continuously electrifying an electromagnetic coil in the relay from before the initiating explosive device is initiated to after the initiating explosive device is initiated so that the relay works normally; the autonomous diagnosis and processing of the trim wing state comprises the following steps: before initiating explosive device, if a signal that a trimming span of a certain path is spread to a proper position is collected to be effective, the path of switch is considered to be in fault, and the path of signal is not used subsequently; after initiating explosive devices are detonated, if one or more than one balancing wing unfolding in-place signals are collected to be effective, the balancing wings are considered to be unfolded in place, otherwise, the balancing wings are considered not to be unfolded; the self-diagnosis and processing of the grounding switch state comprises the following steps: before touchdown, if a certain touchdown switch is in a touchdown state, the touchdown switch is considered to be in a fault state, and the signal of the certain touchdown switch is not used subsequently; after the touch down, whether the touch down is performed or not is judged according to the states of the rest touch down switches.)

1. A system impact-resistant method suitable for Mars landing task is used for initiating explosive device action and touchdown period, and is characterized by comprising relay impact resistance, trim wing state self-diagnosis and processing, touchdown switch state self-diagnosis and processing;

continuously electrifying an electromagnetic coil in the relay from before the initiating explosive device is initiated to after the initiating explosive device is initiated so that the relay works normally;

the autonomous diagnosis and processing of the trim wing state comprises the following steps: before initiating explosive device, if a signal that a trimming span of a certain path is spread to a proper position is collected to be effective, the path of switch is considered to be in fault, and the path of signal is not used subsequently; after initiating explosive devices are detonated, if one or more than one balancing wing unfolding in-place signals are collected to be effective, the balancing wings are considered to be unfolded in place, otherwise, the balancing wings are considered not to be unfolded;

the self-diagnosis and processing of the grounding switch state comprises the following steps: before touchdown, if a certain touchdown switch is in a touchdown state, the touchdown switch is considered to be in a fault state, and the signal of the certain touchdown switch is not used subsequently; after the touch down, whether the touch down is performed or not is judged according to the states of the rest touch down switches.

2. The system impact resistance method according to claim 1, characterized in that for the relay impact resistance:

firstly, continuously sending a relay power supply instruction to pull in a relay; then sending a priming instruction of the initiating explosive device; when the lander enters the next state, stopping sending a relay power supply instruction;

and in the process of continuously sending the relay power supply instruction, the time interval between two adjacent times of sending is less than the preset time interval.

3. The system impact resistance method according to claim 2, wherein the relay adopts an impact resistance mode when the leveling wing of the lander is unfolded and the back cover is thrown.

4. The system impact resistance method according to claim 1, wherein the ground controls whether the relay adopts the impact resistance through a control command.

5. The system impact resistance method according to claim 1, wherein when a ground-set wing-in-place switch state fails, the road wing-out-to-place signal will no longer participate in the logic determination of any wing-out-to-place state.

6. The system impact resistance method according to claim 1, wherein the ground can set a certain touchdown switch state fault so that the touchdown switch does not participate in subsequent touchdown switch logic judgment.

7. The system impact resistance method according to any one of claims 1 to 6, characterized in that a Hall-type touchdown switch is adopted, and the state is disconnected before touchdown; acquiring the state of each path of touchdown switch by using the FPGA in each fixed period, filtering and maintaining the state, and if the FPGA continuously acquires that a path of contact switch is in a closed state, setting the state flag of the path of touchdown switch to be 1, otherwise, setting the state flag of the path of touchdown switch to be 0; where each touchdown switch is initialized to 0 at power-up or to 0 by application software.

8. The system impact resistance method according to claim 7, wherein when the lander is more than 20m from the Mars surface, a certain touchdown switch is in a touchdown state, and the touchdown switch state is considered to be faulty.

9. The system impact resistance method according to any one of claims 1 to 6, wherein the landing gear is attitude-controlled using a thruster when the trim wing is not deployed.

Technical Field

The invention relates to a system impact resisting method suitable for a Mars landing task, and belongs to the field of satellite control technology.

Background

The Mars probe needs to go through a pneumatic deceleration section, a parachuting section and a power deceleration section in the landing process. During the period, the initiating explosive device detonation process of the leveling wings, the parachute bouncing, the large bottom throwing, the landing leg unfolding and the back cover throwing and the parachute unfolding process are sequentially carried out, and during the period, the initiating explosive device detonation and parachute unfolding can generate large impact acceleration which can reach 2200g to the maximum. The GNC subsystem products need to bear the mechanical environment, and the working time sequence of the system is normal and uninterrupted. The Mars landing process is short (about 9 minutes), the measurement and control delay is long (20 minutes per pass), the EDL process cannot be manually interfered on the ground, and the process can be automatically executed only by the system on the track. Therefore, a system impact-resistant method suitable for a mars landing task is needed, and comprises system impact-resistant relay management, trim wing state automatic diagnosis and processing and touchdown switch state automatic diagnosis and processing during initiating explosive devices, so that the independent and reliable completion of a landing process is guaranteed.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the system impact resistance method suitable for the Mars landing task comprises relay impact resistance, trim wing state automatic diagnosis and processing, and grounding switch state automatic diagnosis and processing; continuously electrifying an electromagnetic coil in the relay from before the initiating explosive device is initiated to after the initiating explosive device is initiated so that the relay works normally; the autonomous diagnosis and processing of the trim wing state comprises the following steps: before initiating explosive device, if a signal that a trimming span of a certain path is spread to a proper position is collected to be effective, the path of switch is considered to be in fault, and the path of signal is not used subsequently; after initiating explosive devices are detonated, if one or more than one balancing wing unfolding in-place signals are collected to be effective, the balancing wings are considered to be unfolded in place, otherwise, the balancing wings are considered not to be unfolded; the self-diagnosis and processing of the grounding switch state comprises the following steps: before touchdown, if a certain touchdown switch is in a touchdown state, the touchdown switch is considered to be in a fault state, and the signal of the certain touchdown switch is not used subsequently; after the touch down, whether the touch down is performed or not is judged according to the states of the rest touch down switches.

The purpose of the invention is realized by the following technical scheme:

a system impact-resistant method suitable for Mars landing tasks is used for initiating explosive device actions and grounding periods and comprises relay impact resistance, trim wing state automatic diagnosis and processing and grounding switch state automatic diagnosis and processing;

continuously electrifying an electromagnetic coil in the relay from before the initiating explosive device is initiated to after the initiating explosive device is initiated so that the relay works normally;

the autonomous diagnosis and processing of the trim wing state comprises the following steps: before initiating explosive device, if a signal that a trimming span of a certain path is spread to a proper position is collected to be effective, the path of switch is considered to be in fault, and the path of signal is not used subsequently; after initiating explosive devices are detonated, if one or more than one balancing wing unfolding in-place signals are collected to be effective, the balancing wings are considered to be unfolded in place, otherwise, the balancing wings are considered not to be unfolded;

the self-diagnosis and processing of the grounding switch state comprises the following steps: before touchdown, if a certain touchdown switch is in a touchdown state, the touchdown switch is considered to be in a fault state, and the signal of the certain touchdown switch is not used subsequently; after the touch down, whether the touch down is performed or not is judged according to the states of the rest touch down switches.

Preferably, for the relay to resist impact:

firstly, continuously sending a relay power supply instruction to pull in a relay; then sending a priming instruction of the initiating explosive device; when the lander enters the next state, stopping sending a relay power supply instruction;

and in the process of continuously sending the relay power supply instruction, the time interval between two adjacent times of sending is less than the preset time interval.

Preferably, when the leveling wings of the lander are unfolded and the back cover is thrown, the relay adopts an anti-impact mode.

Preferably, the ground controls whether the relay adopts impact resistance through a control command.

Preferably, when a fault occurs in the ground-set trim-wing-in-place switch state, the path trim-wing-out-to-place signal will no longer participate in the logic determination of any trim-wing-out-to-place state.

Preferably, the ground can be configured with a touchdown switch state fault such that the touchdown switch is no longer involved in subsequent touchdown switch logic determinations.

Preferably, a Hall type touchdown switch is adopted, and the switch is in an off state before touchdown; acquiring the state of each path of touchdown switch by using the FPGA in each fixed period, filtering and maintaining the state, and if the FPGA continuously acquires that a path of contact switch is in a closed state, setting the state flag of the path of touchdown switch to be 1, otherwise, setting the state flag of the path of touchdown switch to be 0; where each touchdown switch is initialized to 0 at power-up or to 0 by application software.

Preferably, when the lander is located 20m or more from the spark surface, and a certain ground contact switch is in a ground contact state, it is considered that the ground contact switch state is failed.

Preferably, when the trim wing is not unfolded, the lander adopts a thruster for attitude control.

Compared with the prior art, the invention has the following beneficial effects:

(1) the system impact resistance design method provided by the invention solves the problem of system tolerance under a large impact environment in the Mars landing process of the space inquiry detector I, and the technology has popularization value in the following Mars sampling return, Mars landing detection and other atmospheric extraterrestrial celestial body soft landing projects.

(2) In the impact process, the method improves the impact resistance of the relay by continuously powering on the contact for actuation, is favorable for reducing the impact resistance index of the relay and expanding the model selection range of the relay;

(3) the invention embodies the design concept of ground priority and is beneficial to the control of the on-satellite state by the ground;

(4) the technology for filtering and maintaining the state of the touchdown switch by using the FPGA is beneficial to reducing the hardware complexity of a product and reducing the frequency of software for acquiring the state of the touchdown switch;

(5) the invention solves the problems of fault diagnosis and isolation of the switch sensor under the condition of large impact, and provides a solution for the use of similar products under similar impact environments.

Drawings

Figure 1 is a schematic view of the access compartment composition.

Fig. 2 is a schematic diagram of a mars landing process.

FIG. 3 is a schematic view of a trim span opening.

FIG. 4 is a trim tab diagnostic and processing flow diagram.

Fig. 5 is a touchdown switch diagnostic and processing flow diagram.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The Mars entrance cabin (landing device) is composed of a back cover, a heat release outsole and a landing platform (figure 1), wherein the back cover is provided with a balance wing and a parachute, and the landing platform is provided with landing legs. Before the detector enters the Mars atmosphere, the landing legs are in a compressed state, and the trim wings are in a closed state. The landing platform is wrapped in a closed cabin formed by a back cover and a heat-proof outsole to form an entrance cabin structure. And the entering-cabin GNC subsystem controls the posture and the position of the entering cabin in the Mars landing process, so that the safe landing of the Mars surface of the detector is realized. The entrance GNC subsystem uses an entrance descent control unit as a core controller, the configured sensors comprise a star sensor, an IMU, a microwave distance measurement and speed measurement sensor, a ground contact switch, a trim wing in-place switch and the like, and the configured actuating mechanism comprises various thrusters, trim wings controlled by initiating explosive devices, parachutes and the like. The sensor enters a descending control unit to collect the measurement output of the sensor, after calculation, the attitude and position speed information of the detector is obtained, and then various actuating mechanisms are driven to act, so that the position and the attitude of the detector reach the expected design state. And when the sensor enters the descending control unit, the sensor in the system can be directly controlled to be powered on or powered off.

In the process of entering the cabin from the outside of the Mars atmosphere to the surface of the Mars, three processes (figure 2) of a pneumatic deceleration section, an umbrella system deceleration section and a power deceleration section are needed, and the product entering the cabin GNC subsystem is electrified in the whole process to complete the detector control in the landing process. The first stage of entering the cabin and entering the Mars atmosphere is a pneumatic deceleration section, the detector decelerates through the resistance of the Mars atmosphere to entering the cabin, when the deceleration reaches a certain degree, the detector enters the cabin GNC subsystem to detonate the initiating explosive on the back cover, and the leveling wings are unfolded to complete the posture adjustment of entering the cabin (figure 3). The GNC subsystem entering the cabin can obtain whether the trim wing is unfolded or not through the state of a contact switch on the state trim wing, and if the trim wing is not unfolded, the detector posture is adjusted by using a thruster; with the further reduction of the speed of entering the cabin, the pneumatic deceleration efficiency is reduced, and the detector is shifted to an umbrella system deceleration section. And at the moment, initiating explosive devices on the back cover by entering the cabin GNC subsystem, popping up a parachute, continuously decelerating the detector after the parachute is unfolded, initiating the explosive devices by entering the cabin GNC subsystem when the speed is reduced to a proper speed, throwing away the heat-proof undersole, initiating the explosive devices again after a certain time interval and the distance between the undersole and the ground is far enough, and unfolding the landing legs on the landing platform. And then the microwave distance and speed measuring sensor can emit microwaves and switch to a working measuring mode. When the detector reaches a certain height, the detector enters the cabin GNC subsystem to initiate an initiating explosive device, the landing platform is separated from the back cover umbrella assembly, then a main engine on the landing platform is ignited, and the landing platform is controlled to land on the surface of a spark safely.

A magnetic latching relay is mounted on a power supply line of each sensor of the cabin GNC subsystem, a ground contact switch and an electromagnetic coil are arranged in the relay, attraction magnetic force is provided by supplying power to the electromagnetic coil to control the on-off of the ground contact switch, the state of the ground contact switch is maintained after the coil is powered off, and the ground contact switch enters a descending control unit to control the on-off of the sensors by controlling the switch of the relay. According to a product manual of the relay, the impact resistance of the relay is about 100g at most, namely when the impact quantity is larger than 100g, the relay can be subjected to on-off state reversal, at the moment, if the product is in an original power-on state, the product can be powered off, and the impact acceleration of the detector initiating explosive device during detonation can reach 2200g at most, so that the possibility of reversal of a sensor power supply relay exists. The system solves the problem that when the initiating explosive device detonates, the magnetic coil of the relay is continuously powered to provide continuous attraction magnetic force, so that the shock resistance of the relay is improved; in addition, for products such as microwave distance measuring and speed measuring sensors, after initiating explosive devices are detonated, the working state of the products is set again to prevent misoperation of the relay.

The trim span opening on-position switch is a compression switch without a memory function, a two-way design of mutual backup is adopted, and the FPGA entering the cabin descending control unit acquires the switch state and provides the switch state for application software to use. In order to ensure the correct use of the switch state in the entering process, the subsystem designs a set of autonomous trim wing opening to position switch diagnosis and processing logic, and the method is that before a descending control unit sends out a trim wing unfolding initiating explosive device action, if a trim wing opening to position signal of a certain path is collected to be effective, the path of switch is considered to be in fault, and the path of signal is not used subsequently; if one or more than one flatting wing unfolding in-place signals are effective after the descending control unit sends the flatting wing unfolding initiating explosive device to act, the flatting wing is considered to be unfolded in place; if the faultless trim wing extending to the position switch is invalid all the time, the trim wing is considered to be not extended, and then a thruster is adopted to replace the trim wing for attitude control. In addition, the ground can also set the state fault of the in-place switch of a certain path of trim wings, and the logic judgment of the in-place state of the subsequent trim wings is not participated.

The landing platform is provided with Hall type grounding switches on four landing legs respectively, and the landing platform is in a disconnected state before grounding. The FPGA of the entry cabin descending control unit collects four paths of grounding switch states, and carries out filtering and state keeping, namely if the FPGA continuously collects that the grounding switch is in a closed state within any 6ms, a grounding switch state mark is 1, and the mark is initialized to 0 during power-on or is set to 0 by application software. Because the large impact of the action of the initiating explosive device can cause the grounding switch to be closed by mistake, a set of autonomous grounding switch diagnosis and processing logic is designed in the system. The specific method is that at the initial stage of starting power deceleration, the four-way touchdown switch state mark of the FPGA is cleared to be 0, then application software detects the four-way touchdown switch mark every period, if the condition that the touchdown switch mark is set to be 1 before 20m from the fire surface occurs, the state fault of the touchdown switch of the path is considered, and the subsequent touchdown shutdown logic judgment is not participated. In addition, the ground can also be provided with a certain path of state fault of the touchdown switch, and the subsequent logic judgment of touchdown shutdown is not involved any more.

A system impact resistance method suitable for Mars landing tasks mainly comprises three aspects of impact resistance relay management, trim wing state automatic diagnosis and processing and touchdown switch state automatic diagnosis and processing.

The system impact-resistant relay management during the action of the initiating explosive device is to improve the impact resistance of the product in a continuous power-on mode of an electromagnetic coil in the relay during the detonation of the initiating explosive device;

before the descending control unit sends the action of the leveling wing unfolding initiating explosive device, if a signal that a leveling wing is unfolded to a proper position is collected to be effective, the state of the leveling wing is automatically diagnosed and processed, the state of the leveling wing is considered to be a fault, and the signal of the leveling wing is not used subsequently; if one or more than one flatting wing unfolding in-place signals are effective after the descending control unit sends the flatting wing unfolding initiating explosive device to act, the flatting wing is considered to be unfolded in place; if the faultless trim wing extending to the position switch is invalid all the time, the trim wing is considered to be not extended, and then a thruster is adopted to replace the trim wing for attitude control. In addition, the ground can also set the state fault of the in-place switch of a certain path of trim wings, and the logic judgment of the in-place state of the subsequent trim wings is not participated;

the automatic diagnosis and processing of the touchdown switch state comprises the steps of entering an FPGA of a cabin descending control unit to acquire four touchdown switch states, filtering and maintaining the states, namely if the FPGA continuously acquires that a contact switch is in a closed state within any 6ms, setting a touchdown switch state flag to be 1, and setting the flag to be 0 during power-on initialization or setting the flag to be 0 by application software. Because the large impact of the action of the initiating explosive device can cause the grounding switch to be closed by mistake, a set of autonomous grounding switch diagnosis and processing logic is designed in the system. The specific method is that at the initial stage of starting power deceleration, the four-way touchdown switch state mark of the FPGA is cleared to be 0, then application software detects the four-way touchdown switch mark every period, if the condition that the touchdown switch mark is set to be 1 before 20m from the fire surface occurs, the state fault of the touchdown switch of the path is considered, and the subsequent touchdown shutdown logic judgment is not participated. In addition, the ground can also be provided with a certain path of state fault of the touchdown switch, and the subsequent logic judgment of touchdown shutdown is not involved any more.

More specifically:

the anti-impact relay management process is as follows:

(1) before the lander starts to enter the Mars atmosphere, a ground injection instruction immediately sets a detonation impact resistant mark Flag _ Antiboom to be 1, which indicates that the following steps 2 to 4 are allowed to be executed on the Mars, otherwise, the following operations are not carried out;

(2) when the speed of the detector is reduced to the speed of unfolding the trim wing, the subsystem firstly sends a sensor power supply instruction, attracts a power supply switch of the sensor and then develops a trim wing initiating explosive device detonation instruction. The single sensor power supply command can enable the electromagnetic coil in the relay to maintain the energizing current for a limited time (set as T1), and in order to ensure that the energizing current lasts for a long enough time, the software sends the sensor power supply command at a time interval not greater than T1;

(3) and about 5s after the vehicle enters the cabin and meets the condition of unfolding the landing leg, stopping sending a sensor power supply instruction by the GNC subsystem. The continuous suction time of the whole relay is about 100s, and the processes of unfolding the leveling wings, bouncing the umbrella, throwing the heat-proof outsole and unfolding the landing legs are covered.

(4) The detector is further decelerated, when the speed is reduced to be capable of throwing the back cover, the subsystem firstly sends a sensor power supply instruction to attract a power supply switch of the sensor, then sends a back cover throwing initiating explosive device initiating instruction, the subsequent subsystem continuously sends the sensor power supply instruction for about 10s, the interval time between two adjacent instructions is ensured to be less than T1, and the instructions cover the process of throwing the back cover and igniting a main engine of a landing platform.

The trim wing autonomous diagnosis and processing flow is as follows:

the FPGA entering the descending control unit collects the unfolding in-place switch states of the two leveling wings, correspondingly generates two leveling wing in-place switch signals to the application software, and the application software finishes a subsequent autonomous diagnosis program. The diagnostic and processing flow is shown in fig. 4.

(1) Before entering the Mars atmosphere, the 'trim span opening signal available mark' is maintained by the ground and can be modified in an uplink injection mode;

(2) the software automatically maintains a usable mark of a trim wingspan opening signal from entering Mars atmosphere to before meeting the requirement of sending a trim wingspan opening instruction, 2 paths of trim wingspan opening to-bit signals are collected according to a fixed period (such as 128ms), if a certain path of trim wingspan opening to-bit signals is effective, the path is considered to be in fault, and the 'usable mark of the trim wingspan opening signal' of the path is set to be unavailable (one position in the mark is 1); the "trim-wingspan signal availability flag" default is fully available (flag 0).

(3) Software collects the trim span open-bit signals output by the 2 paths of parallel ports according to a fixed period (such as 128ms), and performs OR operation on the open-bit signal ('0' represents open in place, '1' represents not open in place) of each path and a usable mark (a certain bit of the mark) of the trim span open signal of the path, and the output result is the trim span open state of the path (0 represents that the path is in the open state, and 1 represents not open state);

(4) and after the software sends a detonation instruction of the trim wing span firing work piece, the software starts to judge a trim wing unfolding mark. When at least 1 path of trim span opening state is found to be effective, the trim span opening mark is set to be effective, and the trim span opening mark is defaulted to be ineffective; and if the initiating explosive device instruction is sent for 10s, the unfolding mark is invalid all the time, the GNC system adopts the thruster to enter the cabin for attitude control, otherwise, the trim wing is used to enter the cabin for attitude control.

The self-diagnosis and processing flow of the grounding switch state is as follows:

the FPGA entering the descending control unit collects four-way touchdown switch states, 4-way touchdown shutdown signals are respectively generated to the application software after filtering and maintaining, and the application software finishes the subsequent autonomous diagnosis program. The application software can change a certain path of touchdown shutdown signal value output by the FPGA in a way of writing the FPGA. The diagnostic and processing flow is shown in fig. 5.

(1) Before entering into the Mars atmosphere, a 'touchdown shutdown signal available mark' is maintained by the ground and can be modified through uplink injection, and when a certain path of 'touchdown shutdown signal is available' (one position in the mark is 0), the path of the touchdown switch signal output by the FPGA is set to be 1 (representing that a touchdown switch is in an untouched state); the initial value of the available mark of the touchdown shutdown signal is defaulted to be fully available (the mark is 0);

(2) after the landing platform enters the power deceleration section, the software carries out write operation on the FPGA once, and a 4-path ignition switch signal is set to be 1.

(3) Then, until the height of the software is 20m from the surface of the mars, the software autonomously maintains available marks of the touchdown shutdown signals, four paths of touchdown shutdown signals are collected according to a fixed period (such as 128ms), when the touchdown shutdown signals are effective, the path is considered to be in failure, and the 'touchdown shutdown signal available mark' of the path is set as unavailable (one bit in the mark is 1);

(4) after 4 paths of touchdown shutdown signals are acquired by software every fixed period, carrying out OR operation on a certain position of the touchdown shutdown signal of each path ('0' indicates that a switch is closed and is effective and '1' indicates that the switch is opened and is ineffective) and a 'touchdown shutdown signal available mark' of the path, and outputting a result as a touchdown shutdown state of the path (0 indicates that the path is in a touchdown state and 1 indicates that the path is in an untouched state);

(5) and (3) judging the touchdown shutdown mark of the landing platform at a position which is 20m below the surface of the Mars in each period, if the touchdown shutdown mark meets the criterion, judging that the touchdown shutdown mark is 1, considering that the landing platform is landed, and carrying out subsequent operation according to a program.

The method is successfully applied to the Mars detector and successfully landed on the Mars surface, and during the period, the strategy works normally, all products of the subsystem work well, all switch states are judged and read correctly, and the purpose of system design is achieved.

Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.

Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.