WO2010034261A1

WO2010034261A1 - Brake vacuum boosting control system for motor vehicle and control method thereof

Info

Publication number: WO2010034261A1
Application number: PCT/CN2009/074269
Authority: WO
Inventors: Xunjin Xu
Original assignee: Byd Company Limited
Priority date: 2008-09-28
Filing date: 2009-09-27
Publication date: 2010-04-01
Also published as: CN101683849B; CN101683849A

Abstract

A brake vacuum boosting control system for a motor vehicle comprises a brake actuating unit for actuating the vehicle to be braked, a sensing unit (11) for sensing a braking signal of the vehicle, a main ECU (12) which receives the braking signal from the sensing unit (11), and a main control circuit connected to the main ECU (12) and the brake actuating unit respectively, and the main ECU (12) outputs a control signal to the brake actuating unit through the main control circuit after receiving the braking signal to brake the vehicle. The control system further comprises an auxiliary ECU (17) connected with the main ECU (12), and an auxiliary control circuit connected with the auxiliary ECU (17), the sensing unit (11), and the brake actuating unit respectively. The auxiliary ECU (17) functions to receive the braking signal and outputs the control signal to the brake actuating unit through the auxiliary control circuit to brake the vehicle when at least one of the main ECU (12) and the main control circuit is in an abnormal state. A control method thereof is also provided. Based on the control system and the control method thereof, the brake boosting can be effectively controlled and safety of a driver can be protected maximally in an abnormal condition such as the main ECU (12) being disabled.

Description

BRAKE VACUUM BOOSTING CONTROL SYSTEM FOR MOTOR VEHICLE AND CONTROL METHOD THEREOF

CROSS-REFERENCE TO RELATED APPLICATIONS The present invention claims the benefit of priority to Chinese Patent

Application No. 200810168835.2 filed on September 28, 2008, which is incorporated by reference herein in its entirety.

FIELD OF TECHNOLOGY The present invention relates to the field of vehicle braking, more particularly to a braking control system and a method of controlling the same.

BACKGROUND OF THE INVENTION

Braking system is indispensable to a vehicle, and now there is an additional braking auxiliary power system in the vehicle, especially the brake vacuum boosting device. The working principle is as follows: pressure difference between negative pressure of the engine in working and the atmospheric pressure is used to push the rubber diaphragm of a braking vacuum booster to drive a piston of a primary brake cylinder so that force for stepping a braking pedal is alleviated. For conventional fuel vehicles, rotation of the engine results in the continual vacuumizing which can ensure a certain braking boosting, and the operating manner is relatively sensitive. For current electric vehicles, however, the engine is replaced by an electric motor. And an engine in a hybrid power vehicle does not work all the time. The motor can not be rotated all the time as does the engine; so the braking effect is far inferior to that of a traditional fuel vehicle.

SUMMARY OF THE INVENTION

In viewing thereof, the present invention is invented to solve at least one technical problem mentioned above. More specifically, the present invention needs to provide a safe and reliable brake vacuum boosting system and a control method thereof to ensure that, in an abnormal condition such as a main control ECU being disabled, the brake boosting can be effectively controlled and safety of a driver can be protected maximally. According to an embodiment of the invention, a brake vacuum boosting control system for a motor vehicle is provided, comprising: a brake actuating unit for actuating the vehicle to be braked; a sensing unit for sensing a braking signal of the vehicle; a main ECU which receives the braking signal from the sensing unit; and a main control circuit connected to the main ECU and the brake actuating unit respectively, and the main ECU outputs a control signal to the brake actuating unit through the main control circuit after receiving the braking signal to brake the vehicle. The control system further comprises an auxiliary ECU connected with the main ECU; and an auxiliary control circuit connected with the auxiliary ECU, the sensing unit, and the brake actuating unit respectively. The auxiliary ECU functions to receive the braking signal and outputs the control signal to the brake actuating unit through the auxiliary control circuit to brake the vehicle when at least one of the main ECU and the main control circuit is in an abnormal state.

According to an embodiment of the invention, a brake vacuum boosting control method for a motor vehicle is provided, comprising the following steps: sensing a braking signal of the vehicle by a sensing unit; receiving the braking signal by a main ECU; outputting a control signal to control a brake actuating unit for braking the vehicle through a main control circuit connected with the main ECU and the brake actuating unit respectively. The method further comprises the following steps: starting an auxiliary ECU and an auxiliary control circuit connected with the auxiliary ECU, the sensing unit, and the brake actuating unit respectively to receive the braking signal by the auxiliary ECU and brake the vehicle by transferring the control signal through the auxiliary control unit to the brake actuating unit when at least one of the main ECU and the main control circuit is in an abnormal state. The brake vacuum boosting control system and the control method thereof of the present invention adopts an auxiliary ECU and an auxiliary control circuit in addition to the original ECU and control circuit being used as the main ECU and the main control circuit. In a normal state, the main ECU and the main control circuit are used to control the opening and closing of the vacuum pump. In an abnormal state of the main ECU and/or the main control circuit, the auxiliary ECU and the auxiliary control circuit are used to control the operation of the vacuum pump to avoid the non-controlling of the vacuum pump. Thus, the reliability and the effectiveness of brake boosting are enhanced, which maximally protects the safety of the driver.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and advantages of the invention will become apparent and more readily appreciated from the following descriptions taken in conjunction with the drawings in which:

Figure 1 is a schematic structural view of a brake vacuum boosting system according to an embodiment of the invention.

Figure 2 is a schematic block diagram of a main ECU and an auxiliary ECU in a brake vacuum boosting system according to an embodiment of the invention. Figure 3 is a schematic block diagram of a hardware control circuit in a brake vacuum boosting system according to an embodiment of the invention.

Figure 4 is a flow chart of a brake vacuum boosting control method according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will be made in detail to embodiments of the present invention. The embodiments described herein with reference to drawings are explanatory, illustrative, and used to generally understand the present invention. The embodiments shall not be construed to limit the present invention. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the descriptions.

According to an embodiment of the invention, the brake vacuum boosting control system for a motor vehicle comprises a brake actuating unit for actuating the vehicle to be braked; a sensing unit for sensing a braking signal of the vehicle; a main ECU (Electronic Control Unit) 12 which receives the braking signal from the sensing unit; and a main control circuit connected with the main ECU 12 and the brake actuating unit respectively, and the main ECU 12 outputs a control signal to the brake actuating unit through the main control circuit after receiving the braking signal to brake the vehicle. The control system may further comprise an auxiliary ECU 17 connected with the main ECU; and an auxiliary control circuit connected with the auxiliary ECU 17, the sensing unit, and the brake actuating unit respectively. The auxiliary ECU 17 functions to receive the braking signal and outputs the control signal to the brake actuating unit through the auxiliary control circuit to brake the vehicle when at least one of the main ECU 12 and the main control circuit is in an abnormal state.

The brake actuating unit may comprise a vacuum pump to trigger the braking operation of the vehicle which will be described in detail hereinafter. The sensing unit may be implemented by a pressure sensor 11. The control system may further comprise a gas storage tank with the braking signal being configured by an electrical signal corresponding to the gas pressure. The pressure sensor 11 may sense gas pressure in the gas storage tank 5 and output the electrical signal corresponding to the gas pressure.

According to an embodiment of the invention, the brake vacuum boosting control system for a motor vehicle, such as an electric motor vehicle, a hybrid vehicle etc, comprises a main ECU 12 and a main control circuit. The main ECU 12 is connected to the main control circuit. And, the main ECU 12 receives the electrical signal corresponding to the gas pressure, and outputs a control signal to control a vacuum pump 6 via the main control circuit the main ECU 12 according to the electrical signal corresponding to the gas pressure. The control system further comprises an auxiliary ECU 17 and an auxiliary control circuit. The auxiliary ECU 17 is connected with the main ECU 12 and the auxiliary control circuit respectively. When at least one of the main ECU 12 and the main control circuit is in abnormal state, the auxiliary ECU 17 is used to replace the main ECU 12 to receive the electrical signal corresponding to the gas pressure and output the control signal to control the vacuum pump 6 via the auxiliary control circuit.

Hereinafter, the control system will be described in detail with reference to FIG. 1. As shown in FIG. 1 , according to an embodiment of the invention, the brake vacuum boosting control system comprises a braking pedal 1, a control valve 2, a vacuum booster 3, a primary brake cylinder 4, a gas storage tank 5, a vacuum pump 6, a braking oil circuit 7, a vacuum servo-air-chamber 8, a liquid storage tank 9, a vacuum check valve 10, a pressure sensor 11 and a main ECU 12. The servo-air-chamber 8 of the vacuum booster 3 includes a back cavity and a front cavity. A linkage mechanism is formed between the back cavity of the servo-air-chamber 8 and the braking pedal 1 via the control valve 2, in order to provide auxiliary boosting to the braking pedal 1. Furthermore, the front cavity of the servo-air-chamber 8 is connected to the gas storage tank 5 by a vacuum pipeline; and the gas storage tank 5 is connected to the vacuum pump 6 by another vacuum pipeline. The vacuum check valve 10 is fixed on the vacuum servo-air-chamber 8 and used to extract air in the front cavity of the vacuum servo-air-chamber 8 via the vacuum check valve 10. The pressure sensor 11 is set on the gas storage tank 5. The main ECU 12, connected to the pressure sensor 11 and the vacuum pump 6 by main control circuit, may detect the pressure corresponding to the gas storage tank 5 by the pressure sensor 11 , and control the open and the close operations of the vacuum pump 6. The primary brake cylinder 4 is connected to vacuum booster 3 and the liquid storage tank 9. By controlling the primary brake cylinder 4 to output the pressure, the vacuum booster 3 transmits liquid in the liquid storage tank 9 to a brake cylinder for braking. FIG. 2 is a schematic structural view of the main ECU 12 and an auxiliary ECU 17 of the brake vacuum boosting system according to an embodiment of the invention. It is clear in FIG.2 that the main ECU 12 is connected with the auxiliary ECU 17. In the main ECU 12, there is an AD (analog-to-digital) converter and a MCU (Micro Controller Unit). The control principle of the main ECU 12 is commonly known in the art: At first, the pressure sensor 11 senses an analog signal representing the pressure. Then the analog signal may be converted to a digital signal by the AD converter of the main ECU 12 and inputted into the MCU of the main ECU 12; finally, the vacuum pump 6 can be controlled to open and close, according to the control signal outputted by the main control circuit representing the different voltage value. In addition, in the auxiliary ECU 17, there also has an AD converter and a MCU. The control principle of the auxiliary ECU 17 is the same as that of the main ECU 12: At first, the pressure sensor 11 collects an analog signal corresponding to the gas pressure; then the analog signal may be converted to a digital signal by the AD converter of the auxiliary ECU 17 and inputted to the MCU of the auxiliary ECU 17; finally, the vacuum pump 6 can be controlled to open and close, according to the control signal outputted by the main control circuit corresponding to the different voltage value.

The main ECU 12 and the auxiliary ECU 17 may be any kind of controller that may control the open operation and close operation of the vacuum pump 6, according to the electrical signal of pressure received, such as PLC (Programmable Logic Controller) or MCU. Alternatively, the main ECU 12 may be the MCU LPC2194 with an encrypted ARM (Advanced RISC Machines) chip, the auxiliary ECU 17 may be a PIC18F2480. When the brake pedal 1 is stepped on for braking, the control valve 2 moves forward. The pressure sensor 11 detects the pressure in the gas storage tank 5. Then, the electrical signal is transferred to the vacuum pump 6. When the voltage value of the control signal from the main ECU 12 is greater than the upper limit of the voltage threshold, the vacuum pump 6 operates accordingly. And the air in the front cavity of the vacuum servo-air-chamber 8 is extracted by the vacuum check valve 10. Thus, the two ends of the diaphragm of the vacuum servo-air-chamber 8 bear different pressure, so the primary brake cylinder 4 outputs much larger pressure. Thus, the liquid in the liquid storage tank 9 is transmitted to the brake cylinder via the brake circuit 7 for the sake of braking. When the voltage value of the control signal from the main ECU 12 is lower than the lower limit of the voltage threshold, the vacuum pump 6 closes, namely, the braking does not occur.

The range of the voltage threshold is determined according to the specific conditions. Alternatively, the r predetermined voltage range ranges from about 0.5V to 2.5V.

The vacuum pump 6 is controlled by the main ECU 12 through the main control circuit outputting the control signal, or by the auxiliary ECU 17 through the auxiliary control circuit outputting the control signal.

Furthermore, the main ECU is self-detectable on whether the main ECU is in the abnormal state or not, when the main ECU is in the abnormal state, the connection of the main ECU and the main control circuit is cut off and the auxiliary ECU and the auxiliary control are started.

In particular, the main ECU 12 is used to confirm that if the main ECU 12 itself is in an abnormal state, such as, of signal collection. When the main ECU 12 is confirmed to be in the abnormal state of signal collection, the connection of the main ECU 12 and the main control circuit is cut off and a start signal of the auxiliary control circuit is outputted to the auxiliary ECU 17. Additionally, the auxiliary ECU 17 can receive the start signal of the auxiliary control circuit and then start the auxiliary control circuit. If the electrical signal received by the main ECU 12 is constant during braking, the main ECU 12 is determined to be in the abnormal state.

Moreover, the main ECU is further used to confirm if the main control circuit is in the abnormal state or not, if the main control circuit is confirmed to be in the abnormal state, the connection of the main ECU and the main control circuit is cut off and a start signal from the main ECU is transmitted to the auxiliary ECU through the auxiliary control circuit. Additionally, wherein a feedback signal of the main control circuit is received by the main ECU 12 and the main control circuit is confirmed to be in the abnormal state when the feedback signal from the main control circuit is different from the control signal that is outputted to the brake actuating unit through the main control circuit.

The main control circuit is a closed-loop type. The main control circuit may be detected to be in the normal state or not by the main ECU 12, according to the logical relation between the control signal outputted via the main control circuit and the feedback signal from the main control circuit. Alternatively, the control signal and the feedback signal from the main control circuit may be preset and stored in the main ECU 12 in advance. When the feedback signal from the main control circuit is detected by the main ECU 12 to be different from the control signal outputted via the main control circuit, the main control circuit is in the abnormal state.

In addition, the auxiliary ECU 17 is further used to confirm that if the main ECU 12 is in the abnormal state of dead halt. When the main ECU 12 is confirmed to in the abnormal state of dead halt, the auxiliary control circuit is started.

The auxiliary ECU 17 is connected with the main ECU 12 via a status port. In that case, the main ECU 12 may be monitored by the auxiliary ECU 17. The main ECU may be detected to be in dead halt or not by the auxiliary ECU 17, according to the logical relation between the interaction port status of the main ECU 12 and the auxiliary ECU 17 and the status preset in the status port. The logical relation of interaction port status of the main ECU 12 and the auxiliary ECU 17 may be preset and stored in the auxiliary ECU 17 in advance. When the logical relation of the interaction port status of the main ECU 12 and the auxiliary ECU 17 is detected by the auxiliary ECU 17 to be different from the logical relation of the port status preset, the main ECU 12 is confirmed to be in the dead halt state; at the same time, the auxiliary control circuit is automatically started. For example, the signal received from the main ECU 12 can be preset to be high, low, high ... in turns from the first status port in the auxiliary ECU 17. When the signal received from the auxiliary ECU 17 is low, high, low... or high, high, low... in turns from the first status port, the logical relation is obviously different from that of the status port preset. Thus, the main ECU 12 is confirmed to be in dead halt.

Besides, the main ECU 12 may be used to detect if the control system is in the sensor fault state and/or in the abnormal state of signal collection of the main ECU and the auxiliary ECU. When the control system is confirmed to be in the sensor halt state and/or in the abnormal state of signal collection of the main ECU and the auxiliary ECU, the connection of the main ECU and the main control circuit will be delayed to cut off and the warning signal is outputted. That is to say, whether the abnormal state of the sensing unit, and/or the abnormal state of the main ECU and the auxiliary ECU in the control system or not are detected by the main ECU, and the connection of the main ECU and the main control circuit is cut off in a time-delay manner and the warning signal is outputted when the control system is confirmed that the sensing unit in the abnormal state and/or the main ECU and the auxiliary ECU are in abnormal states.

Through detecting the change of the electrical signals corresponding to the gas pressure in the braking process, the main ECU 12 can confirm if the control system is in the sensor fault state and/or in the abnormal state of signal collection of the main ECU and the auxiliary ECU. When the electrical signals corresponding to the gas pressure has no change, the control system is confirmed by the main ECU 12 to be in the sensor fault state and/or in the abnormal state of signal collection of the main ECU 12 and the auxiliary ECU 17, and the connection of the main ECU 12 and the main control circuit is cut off in a time-delay manner and the warning signal is outputted.

The connection of the main ECU 12 and the main control circuit may be cut off by the main ECU 12 after a predetermined time. The predetermined time may be set according to the specific condition. Alternatively, the predetermined time is about 10 seconds to 30 seconds. Further according to an embodiment of the invention, the predetermined time is about 20 seconds. In addition, the main ECU 12 may be connected with a warning device, such as a buzzer. When the control system is confirmed to be in the sensor fault state and/or in the abnormal state of signal collection of the main ECU 12 and the auxiliary ECU 17, the warning signal is outputted to the warning device to remind the driver.

When the main ECU 12 and the auxiliary ECU 17 is in the dead halt state at the same time, the main control circuit and the auxiliary control circuit will lose the control of the vacuum pump 6. In that case, the electrical signal corresponding to the gas pressure from the pressure sensor 11 may exceed the range of the controllable voltage threshold. According to another aspect of the invention, in order to control the vacuum pump 6 in such condition, The brake vacuum boosting control system further comprises a hardware control circuit which receives the electrical signal, compares the electrical signal with a predetermined voltage threshold and controls the brake actuating unit to brake the vehicle when the voltage of the electrical signal falls out of a predetermined voltage range.

FIG. 3 is a schematic structural view of the hardware control circuit of the control system. As shown in FIG. 3, the hardware control circuit comprises a first comparator 19 and a second comparator 20. The input terminals of the first comparator 19 and the second comparator 20 are used separately as the input terminal of the hardware control circuit, to receive the electrical signal corresponding to the gas pressure from the pressure sensor 11. The electrical signal received may be compared with a predetermined voltage threshold. When the voltage value of the electrical signal received is out of the range of the pre-determined voltage threshold value, the vacuum pump 6 is controlled by the control circuit.

An upper limit value of the voltage threshold is predetermined in the first comparator 19. When the voltage value of the electrical signal received is greater than the upper limit of the voltage threshold, the first comparator 19 outputs the control signal Control H to the vacuum pump 6 from the port Q402 , thereby starts the vacuum pump 6.

A lower limit value of the voltage threshold is predetermined in the second comparator 20. when the voltage value of the electrical signal received is lower than the lower limit of the voltage threshold, the second comparator 20 outputs the control signal Control L to the vacuum pump 6 from the port Q401 , thereby closes the vacuum pump 6.

The first comparator 19 and the second comparator 20 may be any kind of voltage comparing device that can be used to compare the voltage value of the input electrical signal with the predetermined voltage threshold, and output different control signals according to the comparing result, such as the dual-threshold voltage comparator.

According to one embodiment of the invention, the brake vacuum boosting control method will be described hereinafter. The brake vacuum boosting control method for a motor vehicle, comprises the following steps: sensing a braking signal of the vehicle by a sensing unit; receiving the braking signal by a main ECU 12; outputting a control signal to control a brake actuating unit for braking the vehicle through a main control circuit connected with the main ECU and the brake actuating unit respectively. The method further comprises the following steps: starting an auxiliary ECU and an auxiliary control circuit connected with the auxiliary ECU, the sensing unit, and the brake actuating unit respectively to receive the braking signal by the auxiliary ECU and brake the vehicle by transferring the control signal through the auxiliary control unit to the brake actuating unit when at least one of the main ECU and the main control circuit is in an abnormal state. The sensing unit may comprise a pressure sensor for detecting the gas pressure in the gas storage tank and outputting the electrical signal corresponding to the gas pressure.

FIG. 4 is a flow chart of a brake vacuum boosting control method. According to FIG. 4, the auxiliary ECU 17 is used to confirm if the main ECU 12 is in the dead halt state. The main ECU 12 is used to confirm that if the main ECU 12 is in the abnormal state of signal collection, and if the main control circuit is in the abnormal state. The state confirmation of the main ECU 12 and the main control circuit may be carried at the same time or in turn. At the same time, the voltage value of the received electrical signal is compared with the predetermined voltage threshold by the hardware control circuit to confirm whether control the vacuum pump or not.

The auxiliary ECU is further used to confirm that if the main ECU is in the abnormal state of dead halt or not, when the main ECU is confirmed to be in the abnormal state of dead halt, the auxiliary control circuit is started. Namely, when the logical relation between the interaction port status of the min ECU 12 and the auxiliary ECU 17 is detected by the auxiliary ECU 17 to be different from that of the status port preset, the main ECU 12 is confirmed to be in the dead halt state by the auxiliary ECU 17. Thus, the auxiliary control circuit is started by the auxiliary ECU 17.

If the main control circuit is confirmed to be in the abnormal state, the connection of the main ECU and the main control circuit is cut off and a start signal from the main ECU is transmitted to the auxiliary ECU through the auxiliary control circuit. A feedback signal of the main control circuit is received by the main ECU and the main control circuit is confirmed to be in the abnormal state when the feedback signal from the main control circuit is different from the control signal that is outputted to the brake actuating unit through the main control circuit. That is to say, when the feedback signal from the main control circuit received by the main ECU 12 is different from the control signal outputted via the main control circuit, the main control circuit is confirmed to be in the abnormal state by the main ECU 12. In that case, the connection of the main ECU 12 and the main control circuit is cut off and the auxiliary control circuit is started by the main ECU 12. The vacuum pump 6 is controlled by the auxiliary ECU 17.

The main ECU is self-detectable on whether the main ECU is in the abnormal state or not, when the main ECU is in the abnormal state, the connection of the main ECU and the main control circuit is cut off and the auxiliary ECU and the auxiliary control are started. And the braking signal is configured by an electrical signal corresponding to the gas pressure in a gas storage tank to be sensed by the sensing unit. That is to say, when the electrical signal corresponding to the gas pressure received by the main ECU 12 has some changes, the main ECU 12 is confirmed by the main ECU 12 to be in the normal state, and the vacuum pump 6 is controlled by the main ECU 12.

The main ECU is determined to be in the abnormal state if the electrical signal received by the main ECU is constant during braking. Namely, when the electrical signal corresponding to the gas pressure received by the main ECU 12 has no change but the electrical signal corresponding to the gas pressure received by the auxiliary ECU 17 has some changes, the main ECU 12 is confirmed by the main ECU 12 to be in the abnormal state of signal collection. In that case, the connection of the main ECU 12 and the main control circuit is cut off and the auxiliary control circuit is started. And the vacuum pump 6 is controlled by the auxiliary ECU 17.

The abnormal state of the sensing unit and/or the abnormal state of the main ECU and the auxiliary ECU in the control system or not are detected by the main ECU, and the connection of the main ECU and the main control circuit is cut off in a time-delay manner and the warning signal is outputted when the control system is confirmed that the sensing unit is in the abnormal state and/or the main ECU and the auxiliary ECU are in the state of abnormal states. That is to say, when the electrical signals corresponding to the gas pressure received by the main ECU 12 and the auxiliary ECU 17 both has no change, the control system is confirmed by the main ECU 12 to be in the sensor fault state and/or in the abnormal state of signal collection of the main ECU and the auxiliary ECU. The connection of the main ECU 12 and the main control circuit is cut off in a time-delay manner. Additionally, the warning signal is outputted so that emergency operation may be adopted to prevent the driver of the vehicle from being harmed in a maximal extent. The control method may further comprise the following step: comparing a voltage of the electrical signal with a pre-determined voltage threshold by a hardware control circuit; and controlling the brake actuating unit to brake the vehicle when the voltage value of the electrical signal falls out of a predetermined voltage range. The predetermined voltage range may range from about 0.5V to about 2.5V. That is to say, when the voltage value of the electrical signal received by the hardware control circuit falls out of the range of the predetermined voltage threshold, the vacuum pump 6 is controlled by the hardware control circuit to be actuated to brake the vehicle. Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that changes, alternatives, and modifications can be made in the embodiments without departing from spirit and principles of the invention. Such changes, alternatives, and modifications all fall into the scope of the claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. A brake vacuum boosting control system for a motor vehicle, comprising: a brake actuating unit for actuating the vehicle to be braked; a sensing unit for sensing a braking signal of the vehicle; a main ECU which receives the braking signal from the sensing unit; and a main control circuit connected with the main ECU and the brake actuating unit respectively, and the main ECU outputs a control signal to the brake actuating unit through the main control circuit after receiving the braking signal to brake the vehicle, wherein the control system further comprising: an auxiliary ECU connected with the main ECU; and an auxiliary control circuit connected with the auxiliary ECU, the sensing unit, and the brake actuating unit respectively, wherein the auxiliary ECU functions to receive the braking signal and outputs the control signal to the brake actuating unit through the auxiliary control circuit to brake the vehicle when at least one of the main ECU and the main control circuit is in an abnormal state.

2. The control system according to claim 1, wherein the main ECU is self-detectable on whether the main ECU is in the abnormal state or not, when the main ECU is in the abnormal state, the connection of the main ECU and the main control circuit is cut off and the auxiliary ECU and the auxiliary control are started.

3. The control system according to claim 1, further comprising a gas storage tank with the braking signal being configured by an electrical signal corresponding to gas pressure therein.

4. The control system according to claim 3, wherein if the electrical signal received by the main ECU is constant during braking, the main ECU is determined to be in the abnormal state.

5. The control system according to claim 1, wherein the main ECU is further used to confirm if the main control circuit is in the abnormal state or not, if the main control circuit is confirmed to be in the abnormal state, the connection of the main ECU and the main control circuit is cut off and a start signal from the main ECU is transmitted to the auxiliary ECU through the auxiliary control circuit.

6. The control system according to claim 5, wherein a feedback signal of the main control circuit is received by the main ECU and the main control circuit is confirmed to be in the abnormal state when the feedback signal from the main control circuit is different from the control signal that is outputted to the brake actuating unit through the main control circuit.

7. The control system according to claim 1, wherein the auxiliary ECU is further used to confirm that if the main ECU is in the abnormal state of dead halt or not, when the main ECU is confirmed to in the abnormal state of dead halt, the auxiliary control circuit is started.

8. The control system according to claim 1, wherein whether the abnormal state of the sensing unit, and/or the abnormal state of the main ECU and the auxiliary ECU in the control system or not are detected by the main ECU, and the connection of the main ECU and the main control circuit is cut off in a time-delay manner and the warning signal is output when the control system is confirmed that the sensing unit in the abnormal state and/or the main ECU and the auxiliary ECU are in abnormal states.

9. The control system according to claim 8, further comprising a hardware control circuit which receives the electrical signal, compares the electrical signal with a predetermined voltage threshold and controls the brake actuating unit to brake the vehicle when the voltage of the electrical signal falls out of a predetermined voltage range.

10. The control system according to claim 9, wherein the predetermined voltage range ranges from about 0.5V to about 2.5V.

11. The control system according to claim 3, wherein the sensing unit comprises a pressure sensor for detecting the gas pressure in the gas storage tank and outputting the electrical signal corresponding to the gas pressure.

12. A brake vacuum boosting control method for a motor vehicle, comprising the following steps: sensing a braking signal of the vehicle by a sensing unit; receiving the braking signal by a main ECU; outputting a control signal to control a brake actuating unit for braking the vehicle through a main control circuit connected with the main ECU and the brake actuating unit respectively, wherein the method further comprising the following steps: starting an auxiliary ECU and an auxiliary control circuit connected with the auxiliary ECU, the sensing unit, and the brake actuating unit respectively to receive the braking signal by the auxiliary ECU and brake the vehicle by transferring the control signal through the auxiliary control unit to the brake actuating unit when at least one of the main ECU and the main control circuit is in an abnormal state.

13. The control method according to claim 12, wherein the main ECU is self-detectable on whether the main ECU is in the abnormal state or not, when the main ECU is in the abnormal state, the connection of the main ECU and the main control circuit is cut off and the auxiliary ECU and the auxiliary control are started.

14. The control method according to claim 13, wherein the braking signal is configured by an electrical signal corresponding to gas pressure in a gas storage tank to be sensed by the sensing unit.

15. The control method according to claim 14, wherein the main ECU is determined to be in the abnormal state if the electrical signal received by the main ECU is constant during braking.

16. The control method according to claim 13, wherein the main ECU is further used to confirm if the main control circuit is in the abnormal state or not, if the main control circuit is confirmed to be in the abnormal state, the connection of the main ECU and the main control circuit is cut off and a start signal from the main ECU is transmitted to the auxiliary ECU through the auxiliary control circuit.

17. The control method according to claim 16, wherein a feedback signal of the main control circuit is received by the main ECU and the main control circuit is confirmed to be in the abnormal state when the feedback signal from the main control circuit is different from the control signal that is output to the brake actuating unit through the main control circuit.

18. The control method according to claim 12, wherein the auxiliary ECU is further used to confirm that if the main ECU is in the abnormal state of dead halt or not, when the main ECU is confirmed to be in the abnormal state of dead halt, the auxiliary control circuit is started.

19. The control method according to claim 12, wherein the abnormal state of the sensing unit and/or the abnormal state of the main ECU and the auxiliary ECU in the control system or not are detected by the main ECU, and the connection of the main ECU and the main control circuit is cut off in a time-delay manner and the warning signal is output when the control system is confirmed that the sensing unit is in the abnormal state and/or the main ECU and the auxiliary ECU are in the state of abnormal states.

20. The control method according to claim 19, further comprising the following step: comparing a voltage of the electrical signal with a pre-determined voltage threshold by a hardware control circuit; and controlling the brake actuating unit to brake the vehicle when the voltage value of the electrical signal falls out of a predetermined voltage range.

21. The control method according to claim 20, wherein the predetermined voltage range ranges from about 0.5V to about 2.5V.

22. The control method according to claim 12, wherein the sensing unit comprises a pressure sensor for detecting the gas pressure in the gas storage tank and outputting the electrical signal corresponding to the gas pressure.