1264 results about "Brake pressure" patented technology

The invention discloses a braking pressure degradation strategy of an electronic mechanical braking system, and belongs to the technical field of vehicle braking control, and the braking pressure degradation strategy of the electronic mechanical braking system comprises the following steps: S1, multi-sensor fusion is carried out to correct a friction coefficient in real time, and a high-precision gridding pavement model is constructed; s2, performing time sequence prediction on braking torque distribution, dynamically constraining a braking pressure threshold value and performing pre-adjustment; s3, reinforcement learning is carried out to generate a prospective degradation sequence, and thermal coupling and pressure fluctuation control are optimized; s4, dynamically encrypting the hierarchical communication architecture, and ensuring that the instruction is complete and consistent with the time sequence through redundancy switching; s5, generating an adversarial network compensation failure signal, and dynamically adjusting the weight of the sensor to resist interference; s6, triggering a man-machine interaction strategy in a grading manner, and dynamically adjusting a safety threshold in combination with a driving behavior; s7, carrying out simulation verification on the digital twin platform, and carrying out fault injection encryption to update full-life-cycle parameters; the method has the beneficial effects that self-adaptive optimization and hierarchical fault tolerance of the brake pressure are realized, and the system safety and response efficiency are improved.

A number of variations may include a method including using at least one of brakes or propulsion energy to steer an autonomous or semi-autonomous vehicle if a primary, secondary or other redundant steering system for an autonomous or semi-autonomous vehicle has failed or is insufficiently unhealthy to perform a desired function, the method including determining if a primary, secondary or other redundant steering system of an autonomous or semi-autonomous vehicle has failed or is not sufficiently healthy to perform a desired function, and if so, converting a steer request into a desired yaw rate, curvature, curvature over time, radius, radius or time or yaw rate acceleration, calculating a brake pressure sufficient to produce the desired yaw rate, curvature, curvature over time, radius, radius or time or yaw rate acceleration, delivering brake pressures signals via a lateral control module to an actuator for at least one brake connected to a wheel of the vehicle so that the brake pressure causes the vehicle yaw at the desired yaw rate, curvature, curvature over time, radius, radius or time or yaw rate acceleration.

A brake system includes a reservoir and a motor-driven master cylinder for actuating a plurality of wheel brakes. A secondary power transmission unit provides pressurized hydraulic fluid at first and second PTU outputs for actuating the wheel brakes in at least one of a normal non-failure braking mode and a backup braking mode. The secondary power transmission unit includes an electric PTU motor and at least two pump pistons. At least two brake pressure sensors are provided. Each brake pressure sensor is located directly adjacent a corresponding wheel brake for sensing hydraulic pressure at the corresponding wheel brake and responsively producing a brake pressure signal. An electronic control unit is provided for controlling at least one of the secondary power transmission unit and the master cylinder responsive to at least one brake pressure signal. The secondary power transmission unit is directly fluidly connected to the reservoir.

A driving dynamics system for a vehicle may include a primary control unit for detecting and / or generating steering commands and braking commands; a brake system having first and second electrohydraulic pressure supply units; four hydraulically actuable wheel brakes of respective wheels; electrically actuable brake pressure adjustment valves; and an electric steering actuator for actuating at least one axle. The driving dynamics system may implement a steering command during normal operation to actuate at least one of the pressure supply units and the steering actuator and / or, to implement a braking command during normal operation, to actuate at least the second pressure supply unit and at least the brake pressure adjustment valves for a wheel-specific pressure adjustment and, in a fault case, to actuate at least the first pressure supply unit and at least the brake pressure adjustment valves for a wheel-specific pressure adjustment.

A brake system includes a master cylinder generating pressure at first and second MC outputs for actuating first and second pairs of wheel brakes. A secondary brake module is configured to provide fluid at first and second PTU outputs for actuating the wheel brakes. The secondary brake module includes an electric motor configured to selectively pressurize the hydraulic fluid by transmitting rotary motion to at least two pump pistons. A pump inlet attenuator is interposed hydraulically between a reservoir and the pump pistons and in direct fluid connection with the reservoir via a single return line. An electronic control unit controls at least one of the secondary brake module and the master cylinder responsive to a brake pressure signal. The pump inlet attenuator regulates pressure in the single return line to reduce pressure fluctuations at an inlet side of each pump piston via solely mechanical pressure attenuation.

The invention discloses an intelligent automobile longitudinal driving assistance system based on driving characteristics. The intelligent automobile longitudinal driving assistance system comprises a driver state and environment sensing module, a driver characteristic real-time identification module, an intelligent decision-making and mode switching module and a style self-adaption longitudinal control module. The driver state and environment perception module analyzes environment information and driving behavior characteristics by constructing an extended intelligent driver model, and defines acceleration deviation to perform driving style clustering. And the driver feature real-time identification module deploys the BP neural network model in an online system to realize real-time identification of the driving style. The intelligent decision-making and mode switching module intelligently assesses risks in combination with driving styles and environment information, and dynamically switches four modes of cruise control, car following, early warning and emergency braking. And the style self-adaptive longitudinal control module adaptively adjusts a control strategy according to the driving style and the expected acceleration, and converts the expected acceleration into driving torque or braking pressure through a dynamic weight mechanism, so that personalized longitudinal control is realized.

According to the new energy automobile brake pressure control method based on dynamic environment perception, a multi-window environment perception dynamic time warping algorithm is constructed, so that the similarity of different driver brake sequences is analyzed more meticulously; according to the method, a pavement adhesion coefficient observer for optimizing variable structure Kalman filtering based on a deep reinforcement learning algorithm is provided to calculate a pavement adhesion coefficient; secondly, a slip rate dynamic adjustment factor is obtained through calculation based on a wheel dynamics model, a vehicle density correction coefficient is obtained through calculation based on vehicle density, a road adhesion correction coefficient is obtained based on a road adhesion correction parameter constraint expression, and influences of different external environments on the road adhesion coefficient can be fully considered; the brake pressure calculation is more reasonable, and the driving safety is improved. According to the method, classification results of different drivers are combined, a comprehensive self-adaptive brake pressure calculation model is constructed to cope with different types of drivers, and corresponding final brake pressure is obtained.

The invention relates to the technical field of automobile active safety, in particular to an intelligent brake pad abrasion measuring method and system based on multi-sensor fusion, and the method comprises the steps that S1, multi-source sensing signals are synchronously collected, and wheel speed pulse signals and brake pressure signals from a vehicle CAN bus are received; s2, multi-modal signal feature extraction: carrying out time domain filtering processing on the original thickness signal to form a thickness change feature vector, carrying out space partition calculation on the temperature distribution signal to form a temperature gradient feature matrix, and carrying out wavelet packet decomposition on the braking vibration signal to form a frequency domain energy feature set; s3, dynamically fusing decisions, outputting a joint feature vector, and generating a wear loss estimated value and a confidence index; and S4, performing Kalman filtering correction on the wear loss estimated value according to the confidence index to form final wear thickness data. According to the brake pad wear intelligent measurement method and system based on multi-sensor fusion, the problem that brake pad wear cannot be accurately monitored and intelligently diagnosed online in real time can be solved.

A brake system includes a reservoir and first and second motor-driven master cylinders. An electronic control unit is provided for controlling at least one of the first and second master cylinders responsive to at least one brake pressure signal. A secondary power transmission unit is configured for selectively providing pressurized hydraulic fluid at first and second PTU outputs for actuating first and second pairs of wheel brakes in at least one of a normal non-failure braking mode and a backup braking mode. Each of the first and second PTU outputs provides fluid to a corresponding one of the first and second pairs of wheel brakes. The secondary power transmission unit is directly fluidly connected to the reservoir.

An electrohydraulic multi-circuit power brake system for autonomous driving. The power brake system includes a piston-cylinder unit for each brake circuit, using which the brake circuits are connected to a common power brake pressure generator. In the event of a failure of the power brake pressure generator, the power brake system can be actuated with a hydraulic pump of a slip control system of the vehicle brake system.

The invention relates to the technical field of aircraft brake, in particular to an aircraft brake servo valve performance monitoring and health management method, which comprises the following steps of: acquiring a servo valve theoretical output current and a servo valve recovery current; according to the theoretical output current of each channel of the servo valve and the recovery current of the servo valve, whether brake current output loops of the two channels are abnormal or not is judged; when one channel of brake current output loop is abnormal, whether the other channel of brake current output loop is abnormal or not is judged according to the actual brake pressure and the theoretical pressure; and when the brake pressure output loop of the other channel is normal, brake control is carried out on the servo valve through the channel. By monitoring the performance of the servo valve in real time, it is guaranteed that dynamic switching can be achieved when the performance of the servo valve drifts in the airplane braking process, the influence of the performance drifting of the servo valve on the airplane braking effect is avoided, and the safety of a braking system is improved.

The invention relates to the technical field of pressure sensors, and discloses a structural design method and device applied to a brake pressure sensor, and the method comprises the steps: analyzing the material performance of a sensor material, and analyzing the material demand of a brake demand related to the sensor material; the material matching degree between the material performance and the material requirement is calculated, and the structural material of the brake application scene is determined from the sensor materials; querying geometric parameters of the assembled sensor, and performing force-electricity simulation on the assembled sensor through the piezoelectric constitutive model; the brake sensitivity of the assembled sensor is calculated according to the force-electricity simulation result, the brake failure rate of the assembled sensor is calculated according to the force-electricity simulation result, and defect reason analysis is conducted on the brake sensitivity and the brake failure rate; and querying a structure optimization material of the assembled sensor, and performing structure optimization on the assembled sensor by utilizing the reason analysis result and the structure optimization material. According to the invention, the structural design and materials can be optimized, and the sensitivity and environmental adaptability of the sensor are improved.

The invention discloses a pressure closed-loop control system for an electro-hydraulic pressure servo valve of an aircraft braking system. The pressure closed-loop control system comprises a braking instruction sensor, an FPGA module, a DSP module, a pressure sensor and the electro-hydraulic pressure servo valve. The FPGA module is connected with the DSP module, the brake instruction sensor, the pressure sensor and the electro-hydraulic pressure servo valve. By adopting the incremental PID algorithm and adding the transparent transmission link, the response speed and the control precision of the system are effectively improved, and meanwhile, the problem of brake failure caused by the fault of the pressure sensor is avoided. According to the method, the command pressure change can be quickly responded, and accurate control of the brake pressure is ensured, so that the brake efficiency is improved, the risk of uneven temperature of a brake disc of an aircraft wheel and aircraft yawing is reduced, and the reliability and the safety of an aircraft brake system are enhanced.

The invention provides a vehicle dynamic control method, a vehicle dynamic control system and a vehicle, and relates to the technical field of vehicles, the method comprises the following steps: obtaining current road condition information of a target vehicle; determining whether the target vehicle is in a rainy day driving condition according to the current road condition information; if the target vehicle is in the rainy day driving working condition, the actual yaw velocity, the target yaw velocity, the vehicle speed and the wheel speeds of the multiple wheels of the target vehicle are obtained; calculating an actual yaw deviation angle of the target vehicle according to the actual yaw angular velocity and the target yaw angular velocity, and determining whether a preset yaw control entry triggering condition is met or not; if the preset yaw control entering triggering condition is met, a brake pressure value is calculated according to the actual yaw deviation angle and the vehicle speed; and determining a to-be-controlled tire according to the wheel speeds of the plurality of wheels. The method can accurately inhibit the yaw possibly generated by the target vehicle, and reduces the risk that the vehicle is out of control.

The technical scheme of the invention relates to the technical field of control and adjustment, in particular to a crawler-type articulated vehicle braking system applied to a low-temperature environment. Through multi-module collaborative optimization and a closed-loop control mechanism, the problems of unbalanced dynamic distribution of braking force, insufficient redundancy fault tolerance and signal distortion under the low-temperature working condition are solved. The data acquisition module is used for acquiring a hinging angle, an inertial measurement unit attitude, a braking temperature and a vehicle state signal in real time; the optimization control module performs multi-objective optimization on the dynamic weight coefficient, the redundancy switching threshold value and the fuzzy rule parameter based on a genetic algorithm to generate a weight distribution scheme of a hinge angle compensation mode and an inertial measurement unit dominant mode; the adjusting module generates a brake pressure reference value through temperature self-adaptive analysis and synchronizes hydraulic control units of a front vehicle and a rear vehicle, and all the modules remarkably improve the dynamic stability and the low-temperature working condition fault-tolerant capability of a brake system through full-link cooperation of environment perception, parameter iteration and redundancy execution.

The invention is suitable for the technical field of intelligent driving, and provides a method and device for controlling driving equipment, the driving equipment and a computer program product.The method comprises the steps that under the condition that an auxiliary steering function of the driving equipment is activated, the current driving torque, the current braking pressure, the compensation driving torque and the compensation braking pressure of the driving equipment are obtained; according to the current driving torque and the compensation driving torque, a driving torque is redistributed to a driving motor of the driving equipment; and according to the current brake pressure and the compensation brake pressure, the brake pressure of the driving equipment is adjusted, the control accuracy during vehicle steering is improved, the adaptability of the driving equipment to different working conditions is improved, the driving experience of a user is improved, and the comfort and safety of the vehicle are enhanced.

The invention discloses an anti-lock control method and system for butt joint road surface redundancy braking, a vehicle and a medium. The method comprises the steps that firstly, whether two front wheels are on a butt joint road surface or not is recognized according to the slip rate, unstable time, wheel deceleration, vehicle speed and other information of the two front wheels; and when the vehicle anti-lock braking system is recognized as the butt joint road surface from the high-adhesion road surface to the low-adhesion road surface, the vehicle anti-lock braking system enters a pressure reduction state, pressure reduction is continuously conducted till the vehicle leaves the butt joint road surface from the high-adhesion road surface to the low-adhesion road surface, and it is guaranteed that when wheels drive into the low-adhesion road surface from the high-adhesion road surface, pressure reduction can be rapidly conducted, and the wheels are prevented from being locked. And when the vehicle anti-lock braking system is identified as a butt joint road surface from the low-adhesion road surface to the high-adhesion road surface, the vehicle anti-lock braking system enters a pressurizing state and is rapidly pressurized according to a relatively large reinforcing gradient until any front wheel of the vehicle meets an unstable condition, so that when the wheels drive into the high-adhesion road surface from the low-adhesion road surface, the wheels can be rapidly recovered to relatively high braking pressure; and the braking deceleration is improved.

The invention relates to the technical field of vehicle safety, in particular to a vehicle autonomous emergency braking-oriented road surface attachment sensing method, which comprises the following steps of: acquiring all initial point cloud data in a preset sensing area in front of a vehicle by using a laser radar at the top of the vehicle, and segmenting the initial point cloud data to obtain a road surface point cloud data set in the preset sensing area; acquiring a reflected light intensity value of each piece of road surface point cloud data in a preset sensing area, and taking the road surface point cloud data of which the reflection intensity value is not in a high reflection intensity threshold range but is in a road surface reflection intensity threshold range as target point cloud data; based on the reflection intensity values of all the target point cloud data, generating a grayscale image, inputting the grayscale image into a classification model, outputting a pavement type prediction result, determining a pavement adhesion coefficient, and calculating brake pressure; and if the distance between the current vehicle and the front vehicle is smaller than the safe distance, the vehicle performs autonomous emergency braking based on the braking pressure. The safety and comfort of emergency braking are improved.

An electrically-controlled brake voltage buildup module belongs to the technical field of automobile brake systems and comprises a motor assembly, a piston and a transmission component connected between the motor assembly and the piston, the motor assembly comprises a hollow rotor shaft, the piston and the transmission component are mounted in the hollow rotor shaft, and the piston and the transmission component are mounted in the hollow rotor shaft. The transmission assembly is connected with the hollow rotor shaft through a self-aligning structure, or the transmission assembly is connected with the hollow rotor shaft through the self-aligning structure and a bearing seat, and the transmission mechanism has the beneficial effects that the structure is simple and compact, the concentricity of the transmission mechanism can be improved, the occurrence rate of an eccentric wear phenomenon is reduced, and the service life of the transmission mechanism is prolonged. Product life can be effectively prolonged and noise can be effectively reduced.

The invention belongs to the technical field of road traffic safety, and particularly relates to a pedestrian collision avoidance active safety control method and device suitable for multiple road conditions. Comprising the steps of 1, calculating normalized transverse and longitudinal tire forces through a vehicle dynamics model and a tire model, and obtaining an estimated value of a road adhesion coefficient by taking transverse and longitudinal acceleration and yaw velocity of a vehicle as observation vectors; 2, carrying out coordinate conversion based on a current vehicle coordinate system, and predicting a pedestrian motion track; step 3, determining a collision avoidance control opportunity adopted by pedestrian collision avoidance active safety control; 4, making a pedestrian collision avoidance active safety control decision; and 5, by establishing an inverse dynamic model of a vehicle braking system, according to the obtained expected braking deceleration, brake pressure calculation is carried out, so that braking control over the vehicle is achieved. The method is suitable for different road surface working conditions, and the practicability and robustness of the active safety control method for pedestrian protection are effectively improved.

The utility model discloses a brake pump used on a mobile mechanical brake system, belongs to the technical field of mobile machinery, and solves the problems that an existing brake pump is strenuous in brake operation and poor in brake effect. The brake pump comprises a pump body, a boosting assembly, a connecting assembly, a brake assembly and a booster cylinder body, and is characterized in that the boosting assembly used for boosting and pushing the brake assembly is arranged at the front end of the pump body, one end of the boosting assembly is connected with a pedal, a boosting cavity is formed between the boosting assembly and the pump body, the connecting assembly is arranged in the pump body, and the booster cylinder body is arranged in the boosting cavity. The pressurizing cylinder body is arranged at the rear end of the pump body, the braking assembly is arranged between the pump body and the pressurizing cylinder body, and the left end and the right end of the connecting assembly are connected with the boosting assembly and the braking assembly respectively. According to the brake pump used on the mobile mechanical brake system, a pressurization mode is adopted, so that the brake pump has the advantages that the brake pedal is labor-saving to operate, the brake displacement is large, and the brake pressure is high.

An example brake monitoring system for bicycles comprises at least one force sensing element (FSE) for detecting brake pressure. The FSE may be attached to either a brake lever or a brake pad. A component connects to the FSE and reads force data, and includes a custom PCB, a connector, a battery connector, and resistors for logging and storing brake pressure data in non-volatile storage, or relaying it to a remote system using wireless or wired communication. The system also includes a display device to receive and display brake pressure data. The FSE for brake levers, FSE for brake pads, components, and display devices work together to monitor and display brake pressure data. This system has numerous applications in cycling, including training, safety research, bike design improvement, event organization, bike rental monitoring, and city planning.

The invention relates to the technical field of electric tricycle safety, and discloses an electric tricycle safety collision early warning system and method, and the system comprises a multi-source sensor module, a feature extraction and fusion module, a collision risk assessment module, a path optimization module and a grading early warning control module. The method comprises the steps that the multi-source sensor module collects real-time environment and vehicle state data; the convolutional neural network extracts fusion environment data features to generate vectors, and the vectors are input into a Bayesian network model to output a collision risk probability value; constructing a multi-target path optimization model according to the probability value, and searching an optimal obstacle avoidance path by using an improved particle swarm optimization algorithm; and establishing a grading early warning control model according to the path data, and outputting brake pressure and sound-light alarm signals through a fuzzy logic controller. The system can accurately sense the environment, accurately evaluate the risk, optimize the obstacle avoidance path and perform graded early warning control, improves the driving safety of the electro-tricycle, also has sensor self-inspection and hot backup functions, and enhances the system reliability.

The invention relates to a random stability control method and system of an electronic mechanical braking system and an automobile in the technical field of automobile braking. The control method comprises the steps that under the calibrated brake working condition, brake pressure control is conducted on a brake motor, specifically, the target brake pressure # imgabs0 # output by the brake motor is calculated according to the wheel angular velocity omega at the initial moment of automobile brake and the brake pressure FN on a brake block, and the brake pressure output to the brake block by the brake motor is adjusted to # imgabs1 #. The method is used for conducting brake pressure control on the brake motor according to omega and FN under the calibrated brake working condition, automobile brake safety is guaranteed, meanwhile, automobile brake chatter is effectively restrained, the automobile brake performance is improved, and therefore the problem that in the prior art, while automobile brake safety is guaranteed, the automobile brake chatter is effectively restrained is solved. And the technical problem of automobile braking chatter suppression is effectively solved.

The invention belongs to the technical field of vehicle braking control, and provides a vehicle braking system failure auxiliary processing method, system and device and a medium. When the state is a non-failure state, executing a pressure building braking strategy; when the vehicle is in the failure state, an auxiliary processing strategy is executed, and the auxiliary processing strategy comprises the steps that the braking intention is judged based on vehicle braking feedback, and vehicle stability control threshold setting, deceleration distribution of electric braking and hydraulic braking, active adjustment of the braking pressure and active adjustment of the motor torque are sequentially completed based on the judgment result; and the wheel slip rate of the vehicle is monitored in real time, and the steering force of the vehicle is corrected in combination with vehicle braking feedback. While the deceleration of the vehicle meets the requirement of a driver, drifting or rollover of the vehicle due to the fact that the driver suddenly turns the steering wheel can be avoided, so that the stability of the vehicle is ensured.

The invention discloses a multi-mode redundant model-free longitudinal control method for an automatic driving vehicle. The method comprises the following steps: collecting a longitudinal control signal source; establishing an off-line driving torque database and an off-line braking pressure database; designing a model-free vehicle speed control strategy, and calculating a vehicle speed expected driving torque and a vehicle speed expected braking pressure; designing a model-free acceleration control strategy, and calculating an expected acceleration driving torque; a model-free deceleration control strategy is designed, and deceleration expected brake pressure is calculated; and according to the vehicle speed expected driving torque, the vehicle speed expected braking pressure, the acceleration expected driving torque and the deceleration expected braking pressure, a model-free longitudinal control mode arbitration strategy is designed, the request driving torque and the request braking pressure are output, and longitudinal operation is achieved. According to the method, the stability problem of longitudinal control of the automatic driving vehicle can be solved under the condition that vehicle model parameters are missing or the model parameters are uncertain, and unexpected driving or braking caused by interference of factors such as program abnormity and communication congestion is prevented.

The embodiment of the invention provides a zero point learning method and device for a braking system, and relates to the technical field of motor control, and the method comprises the steps: obtaining a starting signal of braking voltage buildup zero point learning, the starting signal of braking voltage buildup zero point learning being generated based on vehicle power-on or vehicle power-off; the motor controls the piston to move forward from a target position by adopting a set moving method, the forward direction is the direction of the brake disc relative to the piston, and the set moving method is used for controlling the speed change of the piston; in the moving process, motor movement data of the motor are collected, real-time change data of the motor movement data are analyzed, if the real-time change data meet the set movement condition, the current position data, corresponding to the real-time change data, of the piston serves as the braking zero point, and the set movement condition is that when the motor passes through the braking zero point in the movement process, the current position data of the piston is changed into the braking zero point. The generated empirical data is obtained. According to the method, zero point learning and correction can be flexibly and conveniently carried out, and the driving safety is improved.

Disclosed is a number of variations that may include a method, system, or computer product useful in determining an intended yaw or yaw rate that a driver desires using a model, comparing the yaw or yaw rate with the actual vehicle yaw or yaw rate to determining a yaw error or yaw rate error, using the yaw error or yaw rate error in a model predictive control to determine the brake pressure required to minimize or reduced to zero the yaw error or the yaw rate error.

Electric equipment for a vehicle with an electropneumatic service brake device, in which at least one pneumatic brake control pressure is immediately and directly controlled to the electromagnetic backup valve, which is still being closed by a current, of at least one pressure regulating module in response to an assistance brake request signal regardless of a defect of an electric service brake circuit. For a failure of the electric service brake circuit, the electromagnetic backup valve, which is then in the currentless state, of the at least one pressure regulating module is automatically opened, and the brake pressure is immediately formed in the pressure regulating module based on the at least one pneumatic brake control pressure already present in the pressure regulating module. Thus, the reaction time of a pneumatic redundancy of the electropneumatic service brake device in response to electric defects is reduced.

The invention discloses an electronic brake booster rollback fluid infusion method and system and an automobile, and the method comprises the steps that in the braking process, a pressure buildup unit is controlled to build brake pressure for a wheel end brake cylinder; acquiring a liquid quantity state of a brake system; the liquid quantity state of the braking system comprises the braking demand liquid quantity V1 needing to be consumed by a brake cylinder at the wheel end after braking during current driving, the maximum effective braking liquid quantity V2 capable of being provided by the braking system after braking during current driving and the total consumed liquid quantity V3 when the braking intention of a driver is reached after braking during current driving; determining whether the liquid quantity state of the brake system meets a liquid supplementing condition or not; and if yes, the pressure buildup unit is controlled to obtain the brake fluid from the brake fluid storage pot. According to the system, it can be ensured that enough liquid amount exists in the system to support pressure building, the situation that after the ABS function of a vehicle is activated, the brake liquid amount in the pressure building unit is not enough to continue to support the brake requirement of the next cycle is prevented, and the time of returning and liquid supplementing of the brake system can be accurately recognized.