Energy recovery control method for vacuum boosting system of new energy automobile

Abstract

The invention discloses an energy recovery control method for a vacuum booster system of a new energy automobile. The energy recovery control method comprises the following steps that S10, fault monitoring is conducted on a brake system through a fault management system of a VCU; and S20, whether one brake angle sensor breaks down or not is judged, if yes, signals of the other brake angle sensor are obtained through the VCU, and if not, detection is repeated. By designing a braking function safety control strategy, the VCU can still detect the braking intention of a driver and execute electric braking after two paths of braking angle sensor signals all fail under the extreme condition, the braking capacity can effectively solve the problem that the mechanical braking capacity of a pure vacuum boosting system is weak, and the safety of the system is improved. The braking function safety and the braking function robustness of the whole vehicle are improved, and the braking safety of a driver is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy vehicles, and in particular, relates to an energy recovery control method for a vacuum booster system of a new energy vehicle. Background Art

[0002] There are various forms of braking systems for new energy commercial vehicles to meet the needs of different users' vehicle usage scenarios. Among them, vacuum power assist is widely used in the field of light trucks due to its cost advantage and mature products. Vacuum power assist itself is a mechanical brake and has no electronic control-related perception, decision-making and execution, so it has high reliability. The vehicle control unit only needs to detect the vacuum degree to control the start and stop of the vacuum pump.

[0003] For new energy vehicles, electric braking is a major advantage over traditional vehicles. When the vehicle is coasting or braking, part of the vehicle's kinetic energy can be converted into chemical energy and stored in the high-voltage battery, which improves the energy efficiency of the vehicle. For new energy commercial vehicles equipped with a vacuum power assist system, mechanical braking and electric braking are in parallel. A brake switch and a brake angle sensor are installed on the brake pedal to detect the driver's braking action and braking intention. The brake angle sensor is designed with two redundant paths. In order to ensure that after one sensor fails, the other can still detect the driver's braking intensity intention to control the execution of electric braking. For the vacuum power assist system with relatively weak mechanical braking ability, the vehicle relies on electric braking to a certain extent to make up for the lack of mechanical braking ability, thereby strengthening the braking performance and improving braking safety. However, if the vehicle's brake angle sensor itself or wiring harness fails, or the connector becomes loose or short-circuited, the two sensor signals will fail at the same time, the VCU will not be able to detect the driver's braking intensity intention, and the electric brake cannot be calculated and executed. For heavily loaded vehicles, especially on long downhill slopes, the failure of the electric brake will increase the braking safety risk and affect the driver's life safety. Summary of the invention

[0004] The present invention provides an energy recovery control method for a vacuum booster system of a new energy vehicle, which solves the problems raised in the above-mentioned background technology.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a method for controlling energy recovery of a vacuum booster system of a new energy vehicle, comprising the following steps: Step S10, monitoring the brake system for faults through the fault management system of the VCU; Step S20, determining whether one braking angle sensor fails, if so, obtaining a signal from another braking angle sensor through the VCU, if not, repeating the detection; Step S30, determine whether the two brake angle sensors are faulty at the same time, if so, when TwoPathBrkPosSigFltFlag=1, then the VCU sets TwoPathBrkPosSigFltFlag; Step S40, executing processing through the braking function safety control strategy module; Step S50, determining whether the brake switch is closed, if so, the VCU calculates the electric brake torque to be compensated according to the vehicle speed and the braking deceleration, if not, repeating the determination; Step S60, the VCU calculates the vehicle deceleration about 200ms after the brake pressure is established; Step S70, determine whether the vehicle deceleration decreases, if so, the VCU maintains the electric braking torque unchanged, if not, the VCU linearly reduces the electric braking torque.

[0006] Preferably, the method for determining whether a braking angle sensor fails in step S20 comprises the following steps: Step S21, designing high-side diagnostic logic in the underlying software; Step S22, the VCU application layer receives the status interface variable fed back by the underlying software to determine the signal status of the brake angle sensor; Step S23, BSW assigns the read AD value to bsw_110_adc_var; Step S24, BSW obtains the fault status by comparing the AD value with the preset fault threshold; Step S25, BSW reflects the pin fault status in bsw_110_HS_fault; Step S26, when bsw_110_HS_fault=1 or 2, and bsw_111_HS_faultVCU=1 or 2; Step S27: The VCU determines that the signals of the two brake angle sensors are simultaneously faulty.

[0007] Preferably, the electric brake torque calculation method in step S50 comprises the following steps: Step S51, the vehicle is fully loaded and the electric brake torque control is turned off; Step S52, setting the mechanical braking intensity to 10% to 100%, with 10% as an interval; Step S53, setting the vehicle speed from 10 kph to 100 kph, and performing a point sweep test at intervals of 10 kph; Step S54, performing a sweep test and recording the test deceleration data; Step S55, calculating the vehicle deceleration at different vehicle speeds and different braking intensities according to the test data, and obtaining the electric brake compensation torque corresponding to the difference with the ideal braking force curve; Step S56, marking the obtained electric brake compensation torque value into a two-dimensional map of vehicle speed and deceleration.

[0008] The beneficial effects of adopting the above technical solution are: 1. First, the accuracy and timeliness of detecting the driver's braking intention in the event of a brake angle sensor failure are significantly improved, ensuring the rapid response of the braking system, effectively shortening the braking distance, and improving driving safety. Secondly, by optimizing the electric brake execution mechanism, the braking capacity is greatly enhanced, improving the problem of weak mechanical braking capacity of the pure vacuum boost system, so that the vehicle can stop more stably and reliably in emergency braking. Furthermore, the designed multiple fault diagnosis and fault tolerance mechanism, as well as the strong robustness, effectively improve the safety and stability of the vehicle's braking function, and reduce the risk of accidents caused by brake system failures. Finally, the self-learning and self-adaptive capabilities enable the braking control strategy to better adapt to different vehicles and driving conditions, providing drivers with a more personalized and reliable braking experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is the overall control strategy flow chart; Figure 2 It is the VCU bottom-level software brake angle sensor signal diagnosis control flow chart; Figure 3 It is a flow chart of the calculation method of electric brake compensation torque; Figure 4 It is a flow chart of human-machine interaction and vehicle restriction handling strategy. DETAILED DESCRIPTION

[0010] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0011] Embodiment 1: Specifically, Figure 1 As shown, a method for controlling energy recovery of a vacuum booster system of a new energy vehicle comprises the following steps: Step S10, monitoring the brake system for faults through the fault management system of the VCU; Step S20, determining whether one braking angle sensor fails, if so, obtaining a signal from another braking angle sensor through the VCU, if not, repeating the detection; Step S30, determine whether the two brake angle sensors are faulty at the same time, if so, when TwoPathBrkPosSigFltFlag=1, then the VCU sets TwoPathBrkPosSigFltFlag; Step S40, executing processing through the braking function safety control strategy module; Step S50, determining whether the brake switch is closed, if so, the VCU calculates the electric brake torque to be compensated according to the vehicle speed and the braking deceleration, if not, repeating the determination; Step S60, the VCU calculates the vehicle deceleration about 200ms after the brake pressure is established; Step S70, determine whether the vehicle deceleration decreases, if so, the VCU maintains the electric braking torque unchanged, if not, the VCU linearly reduces the electric braking torque.

[0012] It should be noted that the specific description of step S30 is that when the VCU brake function safety control strategy module detects that TwoPathBrkPosSigFltFlag=1, it means that the VCU brake system fault diagnosis module has detected that the brake angle sensor has two faults at the same time, and the brake function safety control strategy module is designed to handle the failure of the brake angle sensor at the same time. When TwoPathBrkPosSigFltFlag=0, that is, when the brake angle sensor has not failed at the same time, the VCU application layer software normally executes the conventional electric brake control strategy, and the VCU calculates the electric brake torque that the motor should perform based on the vehicle speed and the opening converted from the brake angle sensor voltage signal by looking up the table; At the same time, a processing strategy for calculating the electric brake torque based on the vehicle speed and vehicle deceleration is designed. A two-dimensional table lookup is set to calculate the electric brake torque map based on the vehicle speed and vehicle deceleration. When TwoPathBrkPosSigFltFlag=1 and the brake switch is closed, the brake function safety control strategy module switches the electric brake torque control strategy. The calculation of the electric brake torque is based on the two-dimensional table lookup output of the vehicle speed and vehicle deceleration, so the vehicle electric brake torque can still be calculated and executed; The execution principle of the electric brake torque mentioned above is that when both paths of the brake angle sensor fail at the same time, the driver's braking intensity intention cannot be directly calculated through the angle sensor voltage signal, but the mechanical brake is still effective at this time. If the driver steps on the brake pedal, that is, the brake switch is closed, it means that the driver has a braking intention and action. The electric brake intensity can be calculated based on the deceleration test data generated after the mechanical brake is applied to the vehicle. The VCU needs to monitor the vehicle deceleration of about 200ms after the brake switch is closed and the mechanical brake establishes its braking pressure, and compare the theoretical vehicle deceleration calculated after the electric brake torque is applied with the actual deceleration. If the actual deceleration is greater than the theoretical deceleration, it means that the mechanical brake is further enhanced, and the electric brake torque remains unchanged at this time. If the actual deceleration is less than the theoretical deceleration, it means that the mechanical brake has weakened, and the electric brake torque should be weakened synchronously. The change trend of the driver's braking intensity intention is identified through the change of the vehicle deceleration to dynamically control the electric brake torque. In the absence of a credible sensor signal, it does not intervene too much in the braking force, and can also exit the electric brake in time to prevent affecting the drive control.

[0013] Embodiment 2: Specifically, Figure 2 As shown, the method for determining whether a braking angle sensor fails comprises the following steps: Step S21, designing high-side diagnostic logic in the underlying software; Step S22, the VCU application layer receives the status interface variable fed back by the underlying software to determine the signal status of the brake angle sensor; Step S23, BSW assigns the read AD value to bsw_110_adc_var; Step S24, BSW obtains the fault status by comparing the AD value with the preset fault threshold; Step S25, BSW reflects the pin fault status in bsw_110_HS_fault; Step S26, when bsw_110_HS_fault=1 or 2, and bsw_111_HS_faultVCU=1 or 2; Step S27: The VCU determines that the signals of the two brake angle sensors are simultaneously faulty.

[0014] In detail, a fault diagnosis strategy for two brake angle sensors is designed in the brake fault diagnosis module of the VCU fault management system, and a high-side diagnostic logic is designed in the underlying software. The VCU application layer receives the status interface variables fed back by the underlying software to determine the signal status of the brake angle sensor, such as the first signal PIN110 of the brake angle sensor (the second signal PIN111 of the brake angle sensor). The AD value can be read through bsw_110_adc_var, and the fault status of this pin can be read through bsw_110_HS_fault. These two variables are observation quantities used to diagnose the sensor feedback voltage signal pins, while bsw_110_SC_adc_var and bsw_110_OC_adc_var are thresholds for determining the fault of the first signal of the brake angle sensor. The AD value of the PIN110 pin will be different when connected to different loads. Therefore, bsw_110_SC_adc_var and bsw_110_OC_adc_var need to be determined by actual measurements after fault simulation in a vehicle environment. bsw_110_adc_var represents the AD value of the current pin feedback. The pin will have different values ​​when connected to different load resistors. bsw_110_HS_fault represents the current pin status. 0 represents OK, 1 represents open circuit, and 2 represents short circuit. bsw_110_SC_adc_var is used to calibrate open circuit faults. The VCU bottom-layer software will detect the status of the two braking sensors in real time. When bsw_110_adc_var < bsw_110_OC_adc_var, it is determined that the first-channel signal of the angle sensor is open. And bsw_110_OC_adc_var is used to calibrate the short-circuit fault. When bsw_110_adc_var > bsw_110_SC_adc_var, it is determined that the first-channel signal of the braking angle sensor is short-circuited. The application-layer software judges the signal status of the braking angle sensor through the bottom-layer transfer interface variable bsw_110_HS_fault. When the signals of the two sensors simultaneously meet the open-circuit or short-circuit diagnosis conditions, that is, when bsw_110_adc_var < bsw_110_OC_adc_var, or bsw_111_adc_var < bsw_111_OC_adc_var, or bsw_110_adc_var > bsw_110_SC_adc_var, or bsw_111_adc_var > bsw_111_SC_adc_var, and one of the two types of faults occurs simultaneously in the two-sensor signals, bsw_110_HS_fault = 1 or 2, and bsw_111_HS_faultVCU = 1 or 2. The VCU judges that the signals of the two braking angle sensors are simultaneously faulty, and at this time, the two-path braking angle sensor signal simultaneous open-circuit flag bit TwoPathBrkPosSigFltFlag is set.

[0015] Embodiment 3: Specifically, as Figure 3 shown, the electric braking torque calculation method includes the following steps: Step S51, the whole vehicle is fully loaded and the electric braking torque control is turned off; Step S52, set the mechanical braking strength to 10% - 100%, with an interval of 10%; Step S53, set the vehicle speed from 10 kph to 100 kph, and perform sweep-point tests at intervals of 10 kph; Step S54, perform the sweep-point test and record the test deceleration data; Step S55, calculate the vehicle deceleration at different vehicle speeds and different braking strengths according to the test data, and obtain the electric braking compensation torque corresponding to the difference from the ideal braking force curve; Step S56, mark the obtained electric braking compensation torque value into the two-dimensional map of vehicle speed and deceleration.

[0016] It should be noted that the required electric brake strength is detected based on the deceleration generated after the mechanical brake is applied to the vehicle. Actual vehicle testing is required to obtain real and effective data. The mechanical brake strength needs to be set to 10%~100% respectively, with a 10% interval, and the vehicle speed ranges from 10kph~100kph, with a sweep test every 10kph. The vehicle should be fully loaded during the test so that the electric brake torque calculated based on the test data covers the braking performance requirements under most vehicle operating conditions to improve braking safety. Through the measured data mentioned above, based on the ideal braking force curve, the required electric brake compensation torque value is calculated, and the required electric brake torque corresponding to each vehicle speed and braking deceleration is marked into the vehicle speed and vehicle deceleration two-dimensional lookup table to calculate the electric brake torque map, so that the brake function safety control strategy module can switch the electric brake torque control strategy and then perform table lookup output.

[0017] Embodiment 4: Specifically, Figure 4 As shown, if one brake sensor fails, the VCU can use the other signal to calculate and control the electric brake required torque normally. When the two brake angle sensors fail at the same time, although the VCU can continue to calculate and control the electric brake required torque through the brake function safety control strategy module, in order to ensure the safety of electric braking as much as possible, the driver should be notified immediately to go to the vehicle maintenance department for inspection. Therefore, when TwoPathBrkPosSigFltFlag=1, the VCU will control the lighting of the brake system fault light, and the brake system fault signal will be set, that is, VCU_BrakeSys_Err=1. The VCU will send this signal to the central gateway, and the central gateway will forward it to the vehicle instrument of the body CAN. The vehicle instrument will receive it and parse it. If VCU_BrakeSys_Err=1, the brake system fault light will be driven to light up, otherwise the brake system fault light will be kept off. In order to further improve braking safety, when TwoPathBrkPosSigFltFlag=1, that is, when the two brake angle sensors fail at the same time, the VCU will further limit the speed and drive power of the vehicle to prevent the braking performance of the vehicle when it is running at high speed or under heavy load in extreme conditions and causing braking safety risks due to failure to meet the braking performance requirements of the vehicle. The VCU will limit the vehicle speed to no more than 60kph, and limit the drive power to no more than 50% of the maximum capacity. The purpose of limiting the drive power is to prevent the vehicle from running at a high speed with heavy loads and requiring braking due to higher curb weight and greater vehicle inertia, so the braking performance requirements are also higher. At this time, if there is a deviation in the electric brake compensation or noise in the data processing, it may lead to insufficient braking performance, resulting in a braking distance higher than the driver's expectations, causing driving safety risks; After two brake angle sensors fail at the same time, if one or even two faults are cured at the same time during vehicle operation, in order to prevent the fault cure from being unreliable due to factors such as poor connection of the wiring harness or intermittent performance of the sensor, the VCU will not immediately switch the braking function safety control strategy, but will continue to maintain the relevant speed limit and power limit and light up the brake system fault light control in this driving cycle. If the vehicle is powered off and then powered on again without reporting a fault, the VCU will immediately release the relevant fault processing lock state and restore normal electric brake torque control, avoiding safety hazards caused by repeated faults after switching to conventional control strategies, and protecting the braking safety of the entire vehicle.

[0018] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above-mentioned concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for controlling energy recovery of a vacuum boost system of a new energy vehicle, characterized in that: The following steps are involved: Step S10, monitoring the brake system for faults through the fault management system of the VCU; Step S20, determining whether one braking angle sensor fails, if so, obtaining a signal from another braking angle sensor through the VCU, if not, repeating the detection; Step S30, determine whether the two brake angle sensors are faulty at the same time, if so, when TwoPathBrkPosSigFltFlag=1, then the VCU sets TwoPathBrkPosSigFltFlag; Step S40, executing processing through the braking function safety control strategy module; Step S50, determining whether the brake switch is closed, if so, the VCU calculates the electric brake torque to be compensated according to the vehicle speed and the braking deceleration, if not, repeating the determination; Step S60, the VCU calculates the vehicle deceleration about 200ms after the brake pressure is established; Step S70, determine whether the vehicle deceleration decreases, if so, the VCU maintains the electric braking torque unchanged, if not, the VCU linearly reduces the electric braking torque.

2. The energy recovery control method of a vacuum booster system of a new energy vehicle according to claim 1, characterized in that: The method for determining whether a braking angle sensor fails in step S20 comprises the following steps: Step S21, designing high-side diagnostic logic in the underlying software; Step S22, the VCU application layer receives the status interface variable fed back by the underlying software to determine the signal status of the brake angle sensor; Step S23, BSW assigns the read AD value to bsw_110_adc_var; Step S24, BSW obtains the fault status by comparing the AD value with the preset fault threshold; Step S25, BSW reflects the pin fault status in bsw_110_HS_fault; Step S26, when bsw_110_HS_fault=1 or 2, and bsw_111_HS_faultVCU=1 or 2; Step S27: The VCU determines that the signals of the two brake angle sensors are simultaneously faulty.

3. The energy recovery control method of a vacuum booster system of a new energy vehicle according to claim 1, characterized in that: The electric brake torque calculation method in step S50 comprises the following steps: Step S51, the vehicle is fully loaded and the electric brake torque control is turned off; Step S52, setting the mechanical braking intensity to 10% to 100%, with 10% as an interval; Step S53, setting the vehicle speed from 10 kph to 100 kph, and performing a point sweep test at intervals of 10 kph; Step S54, performing a sweep test and recording the test deceleration data; Step S55, calculating the vehicle deceleration at different vehicle speeds and different braking intensities according to the test data, and obtaining the electric brake compensation torque corresponding to the difference with the ideal braking force curve; Step S56, marking the obtained electric brake compensation torque value into a two-dimensional map of vehicle speed and deceleration.

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