CN114487910A - Wiring harness open/short circuit detection circuit and method of automobile ECU - Google Patents

Abstract

The invention discloses a circuit and a method for detecting open/short circuit of a wire harness of an automobile ECU (electronic control Unit), wherein one part is a circuit at a control unit end, the other part is a circuit at an execution unit end, the control unit end circuit periodically sends a diagnosis signal to an execution unit end circuit, the execution unit sends a response signal to a host computer end after receiving the diagnosis signal, if the host computer end can receive the response signal returned by the execution unit, the problem of the wire harness is judged, if the response signal is not received, the diagnosis signal is sent again, and if the response signal is not received, the fault of the wire harness is judged. The invention can diagnose the state of the automobile wire harness without disassembling the automobile wire harness in the running or non-running process of the automobile, and make a decision according to the importance degree of the transmission signal, and can timely decelerate, lean to the side, stop and the like the automobile in the most extreme time, thereby ensuring the life safety of a driver.

Description

Wiring harness open/short circuit detection circuit and method of automobile ECU

Technical Field

The invention relates to the technical field of automotive electronics, in particular to a circuit and a method for detecting open and short circuit of a wire harness of an automotive ECU (electronic control unit).

Background

At present, the intelligent and electric development route of the automobile is obvious, and Tesla is a benchmark for domestic automobile factories to refer to. The functions of the intelligent driving, the intelligent cabin and the automobile body can be upgraded remotely through OTA, and the bright functions cannot be achieved by the traditional automobile with an engine architecture. Tesla starts the precedent of intelligent driving, and the 'FSD' automatic driving function of Tesla really carries out mass production on the ground of the automatic driving function in the science fiction world. However, in recent years, the accident frequency of the Tesla model3 vehicle model is frequently reported to be the problems of brake failure, active acceleration, touch runaway, host computer crash and the like.

2021 is the first year of an intelligent driving product outbreak, and new models of many car factories are provided with intelligent driving area controllers. The phenomena that the intelligent driving area controller has brake failure similar to that of Tesla model3 due to the influence of external factors such as wiring harness failure and invalid vehicle body control are avoided. Therefore, in order to solve such problems, a circuit and a method for detecting an open/short circuit of a wire harness of an ECU of an automobile are provided.

Disclosure of Invention

The invention provides a circuit and a method for detecting open and short circuit of a wire harness of an automobile ECU (electronic control Unit), which solve the problems in the background art and provide a hardware circuit for diagnosing the wire harness, and can diagnose and analyze the fault reason of the wire harness related to a controller in the process of not detaching a car or driving the car normally.

In order to achieve the purpose, the invention adopts the following technical scheme:

a wiring harness open/short circuit detection circuit of an automobile ECU comprises two parts, wherein one part is a circuit located at a control unit end, the other part is a circuit located at an execution unit end, the control unit end circuit sends a diagnosis signal to the execution unit end circuit regularly, the execution unit sends a response signal to a host end after receiving the diagnosis signal, if the host end can receive the response signal returned by the execution unit, the connection wiring harness is judged to have no problem, if the response signal is not received, the diagnosis signal is sent again, if the response signal cannot be received, the connection wiring harness is judged to have a fault, and whether the connection wiring harness belongs to an open circuit state or a short circuit state is judged by detecting the circuit or judging whether the response signal is abnormal or not.

Preferably, the control unit is configured to perform SIGNAL transmission and SIGNAL abnormality detection for the execution unit, and includes an MCU for processing data and 5 key SIGNALs, where the 5 key SIGNALs are a VCC12V _ IN SIGNAL, an MCU _ GPIO SIGNAL, a SIGNAL _ OUT SIGNAL, an MCU _ PWM _ IO SIGNAL, and an MCU _ ADC SIGNAL, respectively, and the VCC12V _ IN SIGNAL is configured to be connected to a 12V dc power supply of the control unit.

Preferably, the MCU _ GPIO signal is used to connect to a GPIO of the MCU, and the GPIO outputs a high/low level to control the switching circuit composed of VT1 and VT2, so as to control the on/off of the VCC12V _ IN dc power supply, when the MCU _ GPIO is at a high level, the switching circuit is turned on, and 12V is output via VT 1.

Preferably, the SIGNAL _ OUT SIGNAL is used for being connected to a connector of the control unit and then connected to a connector of the execution unit end through a transmission cable, and the SIGNAL _ OUT SIGNAL includes a dc/ac mixed SIGNAL composed of a 12V dc voltage from VCC12V _ IN and an ac pulse SIGNAL sent by the MCU _ PWM.

Preferably, the MCU _ PWM _ IO signal is connected to a GPIO of the MCU with PWM function, and the MCU may output a key ac control signal through the MCU _ PWM _ IO signal.

Preferably, the MCU _ ADC signal is connected to a GPIO with an ADC function of the MCU.

Preferably, the execution unit is used for processing data and responding SIGNALs, and comprises an MCU for processing data and 4 control SIGNALs, wherein the 4 control SIGNALs comprise a SIGNAL _ IN SIGNAL, an MCU _ PWM _ IO SIGNAL, a SIGNAL and an MCU _ ADC SIGNAL, the SIGNAL _ IN SIGNAL is connected to the connector and receives a SIGNAL transmitted from a SIGNAL _ OUT by the control unit; the MCU _ PWM _ IO signal is connected to a GPIO of the MCU with a PWM function, and the MCU can output a key alternating current control signal through the MCU _ PWM _ IO signal; the SIGNAL is a 12V direct-current voltage SIGNAL and finally gives a key SIGNAL to an execution circuit; and the MCU _ ADC signal is connected to a GPIO with an ADC function of the MCU.

A method for detecting a circuit of an automobile ECU by opening and short circuit of a wire harness is applied to the circuit, and comprises the following steps: in the control unit:

and (3) direct-current power transmission: the VCC12V _ IN network is connected with a direct current power supply 12V, when the MCU _ GPIO is at a high level, the switching circuit is switched on, the 12V is output through VT1 and then is supplied to the SIGNAL _ OUT network through an inductor L1 and a magnetic bead FB1, wherein L1 and FB1 play roles IN conducting direct current and blocking alternating current;

AC signal transmission: when the control unit needs to send an alternating current SIGNAL, the MCU can input a corresponding alternating current SIGNAL through the MCU _ PWM _ IO network, the alternating current SIGNAL passes through the C3 and is output to the Signal _ OUT network, the Signal _ OUT network is connected to the connector of the control unit, and the SIGNAL is transmitted to the execution unit through the connecting cable, wherein the C3 plays a role in conducting alternating current and blocking direct current;

cable detection at the control unit end: when 12V is powered on, R5 and R6 divide 12V to output a 4V voltage signal, and the MCU _ ADC signal is connected to the ADC interface of the MCU to detect the voltage, and once the voltage of the MCU _ ADC network changes:

if the MCU _ ADC is changed from 4V to 0V, the cable end connected with the SIGNAL _ OUT network can be judged as a cable short circuit or a VT1, C2, R5 and R6 fault;

if the MCU _ ADC is less than 4V but not 0, it can be determined that the voltage of 12V is unstable, the actual voltage is less than 12V, or the cable to which the SIGNAL _ OUT network is connected is short.

Preferably, in the execution unit:

and (3) direct-current power transmission: the SIGNAL _ IN SIGNAL is connected with the direct current and alternating current mixed SIGNAL output by the SIGNAL _ OUT, and after passing through a filter circuit consisting of L2 and FB2, alternating current components are filtered OUT to obtain a 12V direct current voltage SIGNAL which is supplied to a final execution circuit through a SIGNAL network;

AC signal transmission: the SIGNAL _ IN SIGNAL is connected with the direct current and alternating current mixed SIGNAL output by the SIGNAL _ OUT, the alternating current mixed SIGNAL is transmitted to the GPIO with the PWM function of the MCU after being obtained through C3, and the MCU analyzes the alternating current SIGNAL;

cable detection at the execution unit end: when SIGNAL _ IN comes IN, R7 and R8 divide 12V to output a 4V voltage SIGNAL, which is transmitted to the ADC interface of the MCU through the MCU _ ADC SIGNAL for voltage detection, and once the voltage of the MCU _ ADC network changes:

if the MCU _ ADC is changed from 4V to 0V, the end of the cable connected with the SIGNAL _ IN network can be judged to be short-circuited or open-circuited, or L2, FB2, R7, R8 and C5 have faults, but the fault probability of the latter is very small;

if the MCU _ ADC is less than 4V but not 0, it can be determined that the voltage of 12V is unstable, the actual voltage is less than 12V, or the virtual short of the cable to which SIGNAL _ IN is connected.

Preferably, the judgment of the cable connection state:

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 4V, and the communication of alternating current signals of the MCU of the control unit and the execution unit is normal, the cable transmission is normal;

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 4V, and the communication of alternating current signals of the MCU at the control unit side and the execution unit side is abnormal, the cable may be short-circuited to a 12V power supply, or C3 and C4 have faults;

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of alternating current signals of the MCU at the side of the control unit and the execution unit is abnormal, the cable is opened;

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of the alternating current signals of the MCU of the control unit and the execution unit is normal, one or more places of L2, FB2, R7, R8 and C5 are failed;

if the MCU _ ADC signal voltage of the control unit is 0V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of alternating current signals of the MCU at the side of the control unit and the execution unit is abnormal, the cable is short-circuited to the ground;

if the MCU _ ADC signal voltage of the control unit is 0V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of the alternating current signals of the MCU of the control unit and the execution unit is normal, one or more places of VT1, C2, R5 and R6 are failed.

The invention has the beneficial effects that: the invention provides a new scheme, which can diagnose the state of the wire harnesses of an automobile in the running or non-running process of the automobile and under the condition of not disassembling the wire harnesses of the automobile, can quickly and accurately locate the specific fault wire harness according to the transmission of signals when one wire harness has a fault, can prompt the fault for a driver in time, can know the fault information of the cable in the first time if a certain control cable has a fault in the scene of automatic driving, makes a decision according to the importance degree of the transmission signals, can timely decelerate, lean against, park and the like the automobile at the most extreme time, and ensures the life safety of the driver.

Drawings

FIG. 1 is a schematic diagram of the overall architecture of the present invention.

Fig. 2 is a circuit diagram of a control unit according to the present invention.

FIG. 3 is a circuit diagram of an execution unit according to the present invention.

FIG. 4 is a circuit diagram of the connection between the control unit and the execution unit according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

Example 1

Referring to fig. 1 to 4, a wire harness open/short circuit detection circuit of an ECU of a vehicle includes two parts, one of which is a circuit at a control unit side, such as an intelligent driving range controller (or other controller), and another part is a circuit at the end of the execution unit, such as a vehicle lamp controller and a brake controller (the whole frame is shown in fig. 1), the control unit side circuit periodically sends a diagnosis signal to the execution unit side circuit, and after the execution unit receives the diagnosis signal, will send the response signal to the host computer end, if the host computer end can receive the response signal that the execution unit returns, then judge that there is no problem in the connection harness, if does not receive the response signal, will send the diagnostic signal again, if the fault condition is not met, the fault condition of the connecting wire harness is judged, and whether the connecting wire harness is in an open circuit state or a short circuit state is judged through circuit detection or whether the received response signal is abnormal.

As shown IN fig. 2, IN the control Unit, the control Unit is configured to perform SIGNAL transmission and SIGNAL abnormality detection for the execution Unit, and includes an MCU (micro controller Unit, that is, a micro control Unit or a single chip microcomputer) for processing data and 5 key SIGNALs, where the 5 key SIGNALs are VCC12V _ IN SIGNAL, MCU _ GPIO SIGNAL, SIGNAL _ OUT SIGNAL, MCU _ PWM _ IO SIGNAL, and MCU _ ADC SIGNAL, respectively, and the VCC12V _ IN SIGNAL is used to connect to a 12V dc power supply of the control Unit;

the MCU _ GPIO signal is used for being connected to a GPIO (General-purpose input/output) of the MCU, and outputting high/low level through the GPIO to control a switch circuit (hereinafter referred to as a switch circuit) consisting of VT1 and VT2, so as to control the conduction/disconnection of a VCC12V _ IN direct-current power supply, when the MCU _ GPIO is high level, the switch circuit is conducted, and 12V is output through VT 1;

the SIGNAL _ OUT SIGNAL is used for being connected to a connector of the control unit and is connected to a connector of the execution unit end through a transmission cable, and the SIGNAL _ OUT SIGNAL comprises a direct current and alternating current mixed SIGNAL formed by 12V direct current voltage from VCC12V _ IN and an alternating current pulse SIGNAL sent by MCU _ PWM;

the MCU _ PWM _ IO signal is connected to a GPIO of an MCU with a PWM (Pulse Width Modulation) function, and the MCU can output a key alternating current control signal through the MCU _ PWM _ IO signal;

the MCU _ ADC signal is connected to a GPIO of the MCU with an ADC (Analog-to-digital converter) function.

As shown IN fig. 3, IN the execution unit, the execution unit is used for processing data and responding to SIGNALs, and includes an MCU for processing data and 4 control SIGNALs, where the 4 control SIGNALs include a SIGNAL _ IN SIGNAL, an MCU _ PWM _ IO SIGNAL, a SIGNAL and an MCU _ ADC SIGNAL, the SIGNAL _ IN SIGNAL is connected to the connector and receives a SIGNAL transmitted from a SIGNAL _ OUT by the control unit;

the MCU _ PWM _ IO signal is connected to a GPIO of an MCU with a PWM (Pulse Width Modulation) function, and the MCU can output a key alternating current control signal through the MCU _ PWM _ IO signal;

the SIGNAL is a 12V direct-current voltage SIGNAL and finally gives a key SIGNAL to an execution circuit;

the MCU _ ADC signal is connected to a GPIO of the MCU with an ADC (Analog-to-digital converter) function.

Example 2

A method for detecting a circuit of an automobile ECU by opening and short circuit of a wire harness is applied to the circuit, and comprises the following steps:

as shown in fig. 2, in the control unit: and (3) direct-current power transmission: IN fig. 2, a VCC12V _ IN network is connected to a dc power supply 12V, when MCU _ GPIO is at a high level, a switching circuit is turned on, and 12V is output via VT1, then passes through an inductor L1 and a magnetic bead FB1, and then is supplied to a SIGNAL _ OUT network, where L1 and FB1 play roles IN conducting dc and blocking ac;

AC signal transmission: when the control unit needs to send an alternating current SIGNAL, the MCU can input a corresponding alternating current SIGNAL through the MCU _ PWM _ IO network, the alternating current SIGNAL passes through the C3 and is output to the Signal _ OUT network, the Signal _ OUT network is connected to the connector of the control unit, and the SIGNAL is transmitted to the execution unit through the connecting cable, wherein the C3 plays a role in conducting alternating current and blocking direct current;

cable detection at the control unit end: when 12V is powered on, R5 and R6 divide 12V to output a 4V voltage signal, and the MCU _ ADC signal is connected to the ADC interface of the MCU to detect the voltage, and once the voltage of the MCU _ ADC network changes:

if the MCU _ ADC is changed from 4V to 0V, the cable end connected with the SIGNAL _ OUT network can be judged as a cable short circuit or a VT1, C2, R5 and R6 fault;

if the MCU _ ADC is less than 4V but not 0, it can be determined that the voltage of 12V is unstable, the actual voltage is less than 12V, or the cable to which the SIGNAL _ OUT network is connected is short.

As shown in fig. 2, fig. 3 and fig. 4, in the execution unit: and (3) direct-current power transmission: the SIGNAL _ IN SIGNAL IN fig. 3 is connected to the dc/ac mixed SIGNAL output by the SIGNAL _ OUT IN fig. 2, and after passing through the filter circuit composed of L2 and FB2, the ac component is filtered OUT to obtain a 12V dc voltage SIGNAL, which is sent to the final execution circuit through the SIGNAL network, wherein L1 and FB1 play a role IN conducting dc and blocking ac;

AC signal transmission: the SIGNAL _ IN SIGNAL IN fig. 3 is connected to the dc-ac mixed SIGNAL output by the SIGNAL _ OUT IN fig. 2, and after passing through C3, the ac SIGNAL is obtained and transmitted to the GPIO with PWM function of the MCU, and the MCU analyzes the ac SIGNAL, wherein C3 plays a role IN conducting ac and blocking dc;

cable detection at the execution unit end: when SIGNAL _ IN comes IN, R7 and R8 divide 12V to output a 4V voltage SIGNAL, which is transmitted to the ADC interface of the MCU through the MCU _ ADC SIGNAL for voltage detection, and once the voltage of the MCU _ ADC network changes:

if the MCU _ ADC is changed from 4V to 0V, the end of the cable connected with the SIGNAL _ IN network can be judged to be short-circuited or open-circuited, or L2, FB2, R7, R8 and C5 have faults, but the fault probability of the latter is very small;

if the MCU _ ADC is less than 4V but not 0, it can be determined that the voltage of 12V is unstable, the actual voltage is less than 12V, or the virtual short of the cable to which SIGNAL _ IN is connected.

And (3) judging the cable connection state:

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 4V, and the communication of alternating current signals of the MCU of the control unit and the execution unit is normal, the cable transmission is normal;

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 4V, and the communication of alternating current signals of the MCU at the control unit side and the execution unit side is abnormal, the cable may be short-circuited to a 12V power supply, or C3 and C4 have faults;

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of alternating current signals of the MCU at the side of the control unit and the execution unit is abnormal, the cable is opened;

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of the alternating current signals of the MCU of the control unit and the execution unit is normal, one or more places of L2, FB2, R7, R8 and C5 are failed;

if the MCU _ ADC signal voltage of the control unit is 0V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of alternating current signals of the MCU at the side of the control unit and the execution unit is abnormal, the cable is short-circuited to the ground;

if the MCU _ ADC signal voltage of the control unit is 0V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of the alternating current signals of the MCU of the control unit and the execution unit is normal, one or more places of VT1, C2, R5 and R6 are failed.

In summary, the main objective of the present invention is to provide a new solution, which is to diagnose and analyze the cause of failure of a wire harness related to a controller without disassembling the wire harness of a whole vehicle, remind a vehicle owner to repair and maintain the failed wire harness in time when the wire harness failure is found, memorize and store the cause of failure of one or more specific signal wire harnesses, such as the cause of short circuit and open circuit, or facilitate operations such as deceleration and parking near side of the vehicle before the vehicle is out of control, and retrieve data for analyzing the cause of failure after the vehicle is out of control.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims (10)

1. A wiring harness open/short circuit detection circuit of an automobile ECU comprises two parts, wherein one part is a circuit located at a control unit end, and the other part is a circuit located at an execution unit end.

2. The circuit of claim 1, wherein the control unit is configured to perform SIGNAL transmission and SIGNAL abnormality detection for the execution unit, and comprises an MCU for processing data and 5 key SIGNALs, the 5 key SIGNALs are VCC12V _ IN SIGNAL, MCU _ GPIO SIGNAL, SIGNAL _ OUT SIGNAL, MCU _ PWM _ IO SIGNAL and MCU _ ADC SIGNAL, respectively, and the VCC12V _ IN SIGNAL is configured to be connected to a 12V dc power supply of the control unit.

3. The circuit of claim 2, wherein the MCU _ GPIO signal is used to connect to a GPIO of the MCU, and the GPIO outputs a high/low level to control the switching circuit of VT1 and VT2, so as to control the on/off of the dc power supply VCC12V _ IN, and when the MCU _ GPIO is at a high level, the switching circuit is turned on, and 12V is output via VT 1.

4. The circuit of claim 2, wherein the SIGNAL _ OUT SIGNAL is used for connecting to a connector of the control unit and then to a connector of the execution unit via a transmission cable, and the SIGNAL _ OUT SIGNAL comprises a dc/ac mixed SIGNAL consisting of a 12V dc voltage from VCC12V _ IN and an ac pulse SIGNAL from MCU _ PWM.

5. The circuit of claim 2, wherein the MCU _ PWM _ IO signal is connected to a GPIO of the MCU with PWM function, and the MCU can output a key ac control signal via the MCU _ PWM _ IO signal.

6. The circuit of claim 2, wherein the MCU _ ADC signal is connected to a GPIO of the MCU with ADC function.

7. The circuit of claim 1, wherein the execution unit is used for processing data and responding SIGNALs, and comprises an MCU for processing data and 4 control SIGNALs, wherein the 4 control SIGNALs comprise a SIGNAL _ IN SIGNAL, an MCU _ PWM _ IO SIGNAL, a SIGNAL and an MCU _ ADC SIGNAL, the SIGNAL _ IN SIGNAL is connected to the connector and receives SIGNALs transmitted from a SIGNAL _ OUT by the control unit; the MCU _ PWM _ IO signal is connected to a GPIO of the MCU with a PWM function, and the MCU can output a key alternating current control signal through the MCU _ PWM _ IO signal; the SIGNAL is a 12V direct-current voltage SIGNAL and finally gives a key SIGNAL to an execution circuit; and the MCU _ ADC signal is connected to a GPIO with an ADC function of the MCU.

8. A method of wiring harness open/short detection circuit of ECU of automobile, characterized by being applied to the circuit of any one of the above claims 1 to 7, the method comprising the following: in the control unit:

and (3) direct-current power transmission: the VCC12V _ IN network is connected with a direct current power supply 12V, when the MCU _ GPIO is at a high level, the switching circuit is switched on, the 12V is output through VT1 and then is supplied to the SIGNAL _ OUT network through an inductor L1 and a magnetic bead FB1, wherein L1 and FB1 play roles IN conducting direct current and blocking alternating current;

AC signal transmission: when the control unit needs to send an alternating current SIGNAL, the MCU can input a corresponding alternating current SIGNAL through the MCU _ PWM _ IO network, the alternating current SIGNAL passes through the C3 and is output to the Signal _ OUT network, the Signal _ OUT network is connected to the connector of the control unit, and the SIGNAL is transmitted to the execution unit through the connecting cable, wherein the C3 plays a role in conducting alternating current and blocking direct current;

cable detection at the control unit end: when 12V is powered on, R5 and R6 divide 12V to output a 4V voltage signal, and the MCU _ ADC signal is connected to the ADC interface of the MCU to detect the voltage, and once the voltage of the MCU _ ADC network changes:

if the MCU _ ADC is changed from 4V to 0V, the cable end connected with the SIGNAL _ OUT network can be judged as a cable short circuit or a VT1, C2, R5 and R6 fault;

if the MCU _ ADC is changed from <4V to 0, it can be determined that the voltage of 12V is unstable, the actual voltage is less than 12V, or the cable connected to the SIGNAL _ OUT network is short.

9. The method of claim 8, wherein in the execution unit:

and (3) direct-current power transmission: the SIGNAL _ IN SIGNAL is connected with the direct current and alternating current mixed SIGNAL output by the SIGNAL _ OUT, and after passing through a filter circuit consisting of L2 and FB2, alternating current components are filtered OUT to obtain a 12V direct current voltage SIGNAL which is supplied to a final execution circuit through a SIGNAL network;

AC signal transmission: the SIGNAL _ IN SIGNAL is connected with the direct current and alternating current mixed SIGNAL output by the SIGNAL _ OUT, the alternating current mixed SIGNAL is transmitted to the GPIO with the PWM function of the MCU after being obtained through C3, and the MCU analyzes the alternating current SIGNAL;

cable detection at the execution unit end: when SIGNAL _ IN comes IN, R7 and R8 divide 12V to output a 4V voltage SIGNAL, which is transmitted to the ADC interface of the MCU through the MCU _ ADC SIGNAL for voltage detection, and once the voltage of the MCU _ ADC network changes:

if the MCU _ ADC is changed from 4V to 0V, the end of the cable connected with the SIGNAL _ IN network can be judged to be short-circuited or open-circuited, or L2, FB2, R7, R8 and C5 have faults, but the fault probability of the latter is very small;

if the MCU _ ADC is less than 4V but not 0, it can be determined that the voltage of 12V is unstable, the actual voltage is less than 12V, or the virtual short of the cable to which SIGNAL _ IN is connected.

10. The method of claim 9, wherein the determination of the cable connection state:

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 4V, and the communication of alternating current signals of the MCU at the side of the control unit and the execution unit is normal, the cable transmission is normal;

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 4V, and the communication of alternating current signals of the MCU at the control unit side and the execution unit side is abnormal, the cable may be short-circuited to a 12V power supply, or C3 and C4 have faults;

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of alternating current signals of the MCU at the side of the control unit and the execution unit is abnormal, the cable is opened;

if the MCU _ ADC signal voltage of the control unit is 4V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of the alternating current signals of the MCU of the control unit and the execution unit is normal, one or more places of L2, FB2, R7, R8 and C5 are failed;

if the MCU _ ADC signal voltage of the control unit is 0V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of alternating current signals of the MCU at the side of the control unit and the execution unit is abnormal, the cable is short-circuited to the ground;

if the MCU _ ADC signal voltage of the control unit is 0V, the MCU _ ADC signal voltage of the execution unit is 0V, and the communication of the alternating current signals of the MCU of the control unit and the execution unit is normal, one or more places of VT1, C2, R5 and R6 are failed.

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