Fire-fighting power-assisted vehicle slope angle self-adaptive power-assisted braking control method and system

Abstract

The present application relates to the technical field of electric power-assisted bicycle control, and discloses a fire power-assisted bicycle slope inclination self-adaptive power braking control method and system, which collects angular velocity and acceleration data through an inertial measurement unit, calculates real-time slope inclination through coordinate transformation and complementary filtering, and then inputs power and braking control sub-models after sliding mean filtering: the power model maps torque coefficients according to slope intervals, and generates motor instructions in combination with pedal force; the braking model calculates basic braking force according to slope direction and inclination absolute value, and outputs braking instructions after correction by speed table. The system contains data acquisition, inclination calculation, double-channel control and execution modules, and supports ms-level closed-loop regulation. The present application improves the stability and safety of the vehicle in steep slope, continuous ramp and emergency braking scenarios, and realizes smooth self-adaptive collaborative control of power and braking force.

Description

Technical Field

[0001] This invention belongs to the field of electric-assisted vehicle control technology, specifically relating to a method and system for adaptive power-assisted braking control of a fire-fighting vehicle with tilt angle on slopes. Background Technology

[0002] With the widespread application of electric-assisted bicycles in special scenarios such as fire emergency response, mountain rescue, and operations in complex terrain, higher requirements are placed on their power response and braking safety under slope driving conditions. Traditional electric-assisted bicycle control systems are mostly designed for flat or gentle slope scenarios, and their core control logic relies on the linear mapping relationship between pedal torque and vehicle speed, which is essentially an open-loop control architecture under static conditions. However, fire-assisted bicycles often face extreme environments in actual combat, such as continuous steep slopes, undulating terrain, and sudden obstacles. The slope angle where the vehicle is located exhibits high-frequency dynamic changes, and the load fluctuates drastically with an extremely short operating response window. Existing systems lack direct perception and closed-loop feedback of the slope angle, resulting in lag or overload of motor assist output when going uphill, exacerbating the instantaneous discharge pressure on the battery; when going downhill, the braking force distribution is rigid and cannot dynamically adjust the hydraulic pressure of the front and rear wheels according to the slope gradient, which can easily lead to wheel lock-up or sideslip loss of control. In addition, the assist system and braking system operate independently without a coordinated state machine mechanism, which can easily cause conflicts between power and braking torque during slope switching or emergency braking, significantly reducing the stability of the entire vehicle.

[0003] Among these advancements, slope tilt angle adaptive power-assisted braking control technology has become a key direction for improving the safety performance of special-purpose power-assisted vehicles. This technology aims to construct a closed-loop control chain of "perception-decision-execution" through high-precision tilt angle sensing, multi-source data fusion, and electromechanical-hydraulic coordinated execution. This enables all-terrain control capabilities, including on-demand power enhancement for uphill driving, intelligent intervention for downhill resistance, and coordinated stability in emergency situations. The core challenge lies in how to complete dynamic tilt angle calibration, operating mode recognition, and precise actuator control within a millisecond-level response time, while ensuring that the system's robustness does not diminish under harsh environments such as vibration, bumps, and temperature changes.

[0004] A search revealed a patent for an electric-assisted bicycle with starting control method and the bicycle itself, publication number CN115214835B, published on August 1, 2023. This patent calculates and outputs motor torque commands by acquiring parameters such as pedal torque, pedal speed, and ground slope, combined with pre-stored chain drive ratio, current assist ratio, and user weight, thereby achieving a comfortable start. However, this technical solution primarily targets starting control on flat ground or with slight inclines, failing to fully consider the impact of dynamic changes in slope angle on assist and braking. Furthermore, the solution lacks a mechanism for detecting and responding to real-time slope angle during vehicle operation, potentially leading to inaccurate assist and braking output in complex incline environments, affecting vehicle stability and safety.

[0005] A search revealed a control system for an electric bicycle, publication number CN106904242B, published on October 29, 2019. This patent uses an accelerometer to detect the bicycle's acceleration and pedal acceleration, and determines changes in road resistance based on the difference, thereby adjusting the output of the assist motor and battery. While this solution can handle complex road conditions such as slopes to some extent, its reliance on indirect judgment from the accelerometer may not accurately reflect actual changes in the slope's angle. Furthermore, this technical solution lacks adaptive control of the braking system, making it difficult to provide precise braking force adjustment during downhill or emergency situations, potentially posing safety hazards.

[0006] In existing technologies, some solutions attempt to indirectly calculate the slope using acceleration sensors or judge road resistance based on differences in pedal acceleration. However, these methods are severely affected by instantaneous vehicle acceleration, with tilt angle detection errors generally exceeding ±3° and response delays exceeding 500ms, making it difficult to support real-time responses to sudden terrain changes in firefighting scenarios. Other solutions, while incorporating slope parameters, only use them for torque compensation during the initial stage, failing to establish a graded tilt angle control matrix covering the entire travel distance and neglecting to integrate the braking system into the collaborative control framework. This results in reliance on manual adjustments based on driver experience during downhill driving, posing significant safety hazards. Especially in complex situations involving a sudden downhill obstacle after a heavily loaded uphill climb, existing systems cannot seamlessly switch between power assist disengagement and braking intervention within 100ms, easily leading to loss of vehicle speed or exceeding braking distance limits. These deficiencies are amplified in high-risk operations such as firefighting and rescue, urgently requiring a slope adaptive control solution with high-precision tilt angle perception, millisecond-level dynamic response, and deep electromechanical-hydraulic coordination capabilities to ensure personnel safety and mission efficiency. Summary of the Invention

[0007] This invention provides a slope tilt angle adaptive power-assisted braking control method and system for fire-assisted vehicles, aiming to solve the technical problems of insufficient vehicle stability and low handling safety caused by low slope tilt angle detection accuracy and delayed power-assisted braking response when existing electric-assisted vehicles are driving on complex slope terrain.

[0008] On one hand, this invention provides an adaptive power-assisted braking control method for a fire-assisted vehicle with slope tilt angle, comprising: real-time acquisition of angular velocity and linear acceleration data of the vehicle in three-dimensional space by an inertial measurement unit composed of a three-axis gyroscope and a three-axis accelerometer; time synchronization and coordinate system transformation of the acquired raw angular velocity and linear acceleration data to unify them to the vehicle's body coordinate system; calculation of the vehicle's current pitch angle relative to the horizontal plane using a complementary filtering algorithm based on the transformed angular velocity and linear acceleration data, which is the current slope tilt angle; sliding window mean filtering of the calculated slope tilt angle to eliminate high-frequency noise interference and obtain a stable and reliable slope tilt angle output value; inputting the filtered slope tilt angle into a power-assisted control sub-model, which maps the slope tilt angle to a corresponding power-assisted level coefficient according to a preset slope interval division rule, and the power-assisted level coefficient is correlated with the values ​​obtained by the pedal torque sensor. The collected user pedaling torques are multiplied to generate a target output torque command for the motor. The filtered slope angle is simultaneously input to the braking control sub-model. This sub-model determines whether the vehicle is going uphill or downhill based on the sign of the slope angle, calculates the baseline braking torque value based on the absolute value of the slope angle, and combines this with the current vehicle speed data collected by the vehicle speed sensor. A speed correction coefficient is determined using a lookup table method. The baseline braking torque value is multiplied by the speed correction coefficient to obtain the final braking command output value. The target output torque command for the motor is sent to the motor driver to control the motor to output the corresponding torque. The final braking command output value is sent to the electronic brake controller to adjust the brake caliper clamping force or the brake drum braking torque. During vehicle operation, the above steps of data acquisition, slope angle calculation, filtering, assist command generation, braking command generation, and control execution are continuously and cyclically executed to achieve dynamic closed-loop control under changing slope angles.

[0009] Preferably, the inertial measurement unit is fixedly installed at the geometric center of the vehicle frame, with its mounting plane parallel to the longitudinal symmetry plane of the vehicle, ensuring that the acquired data strictly corresponds to the vehicle's motion attitude; the three-axis gyroscope has a range of ±250° / s and a zero-bias stability better than 0.5° / h; the three-axis accelerometer has a range of ±4g and a noise density lower than 200μg / √Hz; the time synchronization adopts a hardware triggering method, with the main controller sending a synchronization pulse signal to simultaneously trigger the data acquisition actions of the gyroscope and accelerometer, ensuring that the timestamp error between the two sets of data is less than 0.1ms; the coordinate system transformation adopts the direction cosine matrix method, rotating the measured values ​​in the original coordinate system of the sensor to a body coordinate system with the vehicle's forward direction as the X-axis and the vertical upward direction as the Z-axis.

[0010] Preferably, in the complementary filtering algorithm, the weighting coefficient of the gyroscope angular velocity integral term is set to 0.95, and the weighting coefficient of the accelerometer tilt angle observation term is set to 0.05; the window length of the sliding window mean filter is set to 20 sampling points, the sampling frequency is 100Hz, and the corresponding time window is 0.2s; the slope interval division rule divides the slope tilt angle into five intervals: -15° to -5° corresponds to the downhill light assist suppression zone, -5° to 0° corresponds to the downhill transition zone, 0° to 5° corresponds to the flat slope standard assist zone, 5° to 15° corresponds to the uphill moderate assist enhancement zone, and 15° to 30° corresponds to the uphill heavy assist enhancement zone; each interval corresponds to a fixed assist level coefficient, which are 0.3, 0.6, 1.0, 1.4, and 1.8, respectively; the pedal torque sensor is installed at the central shaft crank connection, with a range of 0-50 N·m, and the output signal is sampled by a 12-bit analog-to-digital converter and then input to the main controller.

[0011] Preferably, in the braking control sub-model, when the slope angle is greater than zero, it is determined to be an uphill state, and the basic braking torque reference value is set to zero; when the slope angle is less than zero, it is determined to be a downhill state, and the basic braking torque reference value increases linearly with the absolute value of the slope angle. The calculation formula is: basic braking torque reference value = absolute value of slope angle multiplied by 0.5 N·m / °; the vehicle speed correction coefficient is obtained through a two-dimensional lookup table, where the horizontal axis of the table is the vehicle speed and the vertical axis is the absolute value of the slope angle. The vehicle speed is divided into three intervals: 0-5 km / h, 5-15 km / h, and 15-30 km / h, and the absolute value of the slope angle is divided into three intervals: 0-5°, 5-15°, and 15-30°, forming a total of nine combined regions. Each region corresponds to a preset vehicle speed correction coefficient with a value range of 0.8-1.5; the electronic brake controller adopts a proportional solenoid valve structure, with a current control accuracy better than 2% and a response time of less than 20 ms.

[0012] Preferably, after generating the target output torque command for the motor, a torque change rate limiting module is added. This module constrains the difference in torque commands between adjacent control cycles to ensure that the torque change rate does not exceed 20 N·m / s, thus avoiding sudden changes in motor output that could cause shock to the transmission system. After generating the final braking command output value, a brake pressure gradual change control module is added. This module performs first-order inertial filtering on the braking command, with a time constant set to 0.3 s, to ensure that the braking torque rises or falls smoothly, preventing wheel lock-up or vehicle jerking. When the vehicle detects that the absolute value of the slope angle exceeds 25° and lasts for more than 3 s, the hill-start assist mode is automatically activated. In this mode, the motor output torque is maintained at 80% of the current value, and the braking system is preloaded with 30% of the base braking torque until the driver actively releases the brakes or the slope decreases to a safe range.

[0013] On the other hand, a slope tilt angle adaptive power-assisted braking control system for a fire-assisted vehicle is provided, comprising: an inertial measurement unit for real-time acquisition of the vehicle's angular velocity and linear acceleration data in three-dimensional space; a data preprocessing module for time synchronization and coordinate system transformation of the acquired raw angular velocity and linear acceleration data, unifying them to the vehicle's body coordinate system; a slope tilt angle calculation module for calculating the vehicle's current pitch angle relative to the horizontal plane based on the transformed angular velocity and linear acceleration data using a complementary filtering algorithm; a tilt angle filtering module for performing sliding window mean filtering on the calculated slope tilt angle to eliminate high-frequency noise interference and obtain a stable and reliable slope tilt angle output value; and a power-assisted control module for inputting the filtered slope tilt angle into the power-assisted control sub-model. The system is divided into several modules: a slope range division module and a main control module. The first module maps the slope range division to a power assist level coefficient, multiplies it with the pedal torque to generate the target output torque command for the motor; the second module inputs the filtered slope angle into the braking control sub-model, determines the slope direction based on the sign of the angle, calculates the baseline braking torque value based on the absolute value of the angle, and then determines the vehicle speed correction coefficient using a lookup table method, multiplying these values ​​to obtain the final braking command output value; the third module receives the target output torque command for the motor and controls the motor to output the corresponding torque; the fourth module receives the final braking command output value and adjusts the brake caliper clamping force or brake drum braking torque; and the fifth module continuously cycles through all the modules during vehicle operation to achieve dynamic closed-loop control under varying slope angles.

[0014] Preferably, the system also includes a hill-start assist activation module, which automatically activates the hill-start assist mode when the absolute value of the slope angle exceeds 25° for 3 seconds. In this mode, the motor torque output is maintained and the braking pressure is preloaded. The system also includes an abnormal tilt angle alarm module, which triggers a system self-check and switches to a safety degradation mode when the tilt angle calculation value jumps by more than 5° within 5 consecutive control cycles. At this time, the power assist output is limited to 50% of the standard value, and the braking system enters a fully mechanical backup state. The system also includes a data storage module, which records the slope angle, power assist torque command, braking command, vehicle speed, and pedal torque data in each control cycle to form a driving log for post-event analysis and system optimization.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are as follows: By fusing measurements from a three-axis gyroscope and a three-axis accelerometer, the vehicle's pitch angle is directly obtained as the slope tilt angle, avoiding the cumulative error and dynamic response lag caused by indirect calculations from accelerometer sensors. A dual filtering mechanism of complementary filtering and sliding mean effectively suppresses sensor noise and vehicle vibration interference, ensuring stable and reliable tilt angle data. Independent power assist control and braking control sub-models are established, achieving precise adjustments based on slope range and vehicle speed, breaking the existing control architecture where power assist and braking are isolated. Torque change rate limiting and brake pressure gradual control are introduced to improve the smoothness of power output and braking response, reducing mechanical shock and ride discomfort. A dual safety mechanism of hill-start assist and abnormal tilt angle alarm is set up, automatically degrading operation in extreme slopes or sensor failures to ensure basic vehicle handling safety. The overall system achieves millisecond-level closed-loop control, adapting to the high-intensity operational needs of fire-assisted vehicles in complex terrains such as steep slopes, slippery surfaces, and rugged terrain, significantly improving the vehicle's driving stability, operational safety, and mission execution reliability in slope environments. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall technical architecture of the adaptive power-assisted braking control method and system for fire-assisted vehicles on slopes proposed in this invention.

[0017] Figure 2 This is a schematic diagram of the core principle framework of the dynamic sensing and dual-channel control model of slope tilt angle based on inertial measurement and complementary filtering in this invention.

[0018] Figure 3 This is a logical flow diagram of the coordinated execution stage of power assist control and braking control in this invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] This invention provides a method and system for adaptive power-assisted braking control of fire-fighting vehicles on slopes. The core of this system lies in constructing a closed-loop control architecture based on real-time slope angle sensing. Three-dimensional motion data of the vehicle is collected by an inertial measurement unit, and high-precision pitch angle values ​​are obtained through coordinate transformation and complementary filtering. High-frequency noise is then eliminated through sliding window mean filtering. Finally, the stable pitch angle values ​​are input into independently designed power-assisted control sub-models and braking control sub-models, achieving millisecond-level coordinated adjustment of power output and braking torque. This method and system are particularly suitable for high-intensity operation scenarios of fire-fighting vehicles in complex terrains such as steep slopes, slippery surfaces, and rugged terrain, significantly improving vehicle driving stability, operational safety, and mission execution reliability.

[0021] In this embodiment, the adaptive power-assisted braking control method for the fire-assisted vehicle's slope tilt angle includes: real-time acquisition of the vehicle's angular velocity and linear acceleration data in three-dimensional space using an inertial measurement unit composed of a three-axis gyroscope and a three-axis accelerometer; time synchronization and coordinate system transformation of the acquired raw angular velocity and linear acceleration data to unify them into the vehicle's body coordinate system; calculation of the vehicle's current pitch angle relative to the horizontal plane using a complementary filtering algorithm based on the transformed angular velocity and linear acceleration data, which is the current slope tilt angle; sliding window mean filtering of the calculated slope tilt angle to eliminate high-frequency noise interference and obtain a stable and reliable slope tilt angle output value; inputting the filtered slope tilt angle into the power-assisted control sub-model, which maps the slope tilt angle to a corresponding power-assisted level coefficient according to a preset slope interval division rule, and this power-assisted level coefficient is correlated with the values ​​collected by the pedal torque sensor. The user's pedaling torque is multiplied to generate a target output torque command for the motor. The filtered slope angle is simultaneously input to the braking control sub-model. This sub-model determines whether the vehicle is going uphill or downhill based on the sign of the slope angle, calculates a baseline braking torque value based on the absolute value of the slope angle, and combines this with the current vehicle speed data collected by the vehicle speed sensor. A speed correction coefficient is determined using a lookup table. The baseline braking torque value is multiplied by the speed correction coefficient to obtain the final braking command output value. The target output torque command for the motor is sent to the motor driver to control the motor to output the corresponding torque. The final braking command output value is sent to the electronic brake controller to adjust the brake caliper clamping force or the brake drum braking torque. During vehicle operation, the above steps of data acquisition, slope angle calculation, filtering, assist command generation, braking command generation, and control execution are continuously and cyclically executed to achieve dynamic closed-loop control under changing slope angles.

[0022] The inertial measurement unit (IMU) is fixedly installed at the geometric center of the vehicle frame, with its mounting plane parallel to the vehicle's longitudinal symmetry plane, ensuring a strict correspondence between the acquired data and the vehicle's motion attitude. The three-axis gyroscope has a range of ±250° / s and a zero-bias stability better than 0.5° / h; the three-axis accelerometer has a range of ±4g and a noise density lower than 200μg / √Hz. Time synchronization is achieved through hardware triggering, with the main controller sending a synchronization pulse signal to simultaneously trigger the data acquisition actions of the gyroscope and accelerometer, ensuring that the timestamp error between the two sets of data is less than 0.1ms. Coordinate system transformation employs the direction cosine matrix method, rotating the measurements from the original sensor coordinate system to a body coordinate system with the vehicle's forward direction as the X-axis and vertical upward as the Z-axis. Specifically, the direction cosine matrix is ​​constructed based on the vehicle's factory calibration attitude. The rotational relationship between the sensor coordinate system and the vehicle coordinate system is determined through a static calibration procedure. This rotation matrix is ​​loaded into the main controller's memory once during system initialization. All subsequent raw data undergo coordinate transformation through matrix multiplication. The transformation process is executed in real-time within each control cycle, ensuring data spatial consistency. The direction cosine matrix is ​​determined through a static calibration procedure: the vehicle is placed on a level calibration platform, the accelerometer output is collected in a stationary state, and the initial rotation matrix is ​​calculated. Among them, X body =[1,0,0] (direction of movement), Z body =[0,0,1] (vertically upward), the sensor coordinate system vector is obtained through normalized acceleration data; during initialization, R is read from EEPROM. init And load it into memory.

[0023] After coordinate transformation, the slope inclination angle calculation stage begins. This stage employs a complementary filtering algorithm to fuse the gyroscope integral angle and the accelerometer observation angle, balancing dynamic response speed and static accuracy. The weighting coefficient for the gyroscope angular velocity integral term is set to 0.95, and the weighting coefficient for the accelerometer inclination angle observation term is set to 0.05. The specific calculation process of the complementary filtering is as follows: First, the angular velocity data output by the gyroscope is numerically integrated along the pitch axis to obtain the integrated inclination angle at the current moment; second, using the Z-axis and X-axis components of the accelerometer in the vehicle coordinate system, the observed inclination angle at the current moment is calculated using the arctangent function; finally, the integrated inclination angle and the observed inclination angle are weighted and summed according to the weighting coefficients to obtain a preliminary inclination angle estimate. This algorithm effectively suppresses long-term errors caused by gyroscope integral drift, while avoiding instantaneous observation noise from the accelerometer caused by vehicle vibration or acceleration / deceleration. The calculation formula is as follows: Where, θ cf For the complementary filter output tilt angle, θ prevθ is the backslope angle after filtering in the previous cycle, ω is the pitch axis angular velocity output by the three-axis gyroscope (unit: rad / s), Δt is the control cycle time (fixed at 10ms), and θ is the tilt angle after filtering in the previous cycle. acc θ is the tilt angle observed by the accelerometer during the current period. acc via atan2(a z , a x )Calculations show that a x With a z These are the acceleration components along the X-axis (forward direction) and Z-axis (vertically upward) in the vehicle coordinate system (unit: m / s²). 2 α is the gyroscope weighting coefficient, with a value of 0.95.

[0024] After obtaining the initial tilt angle estimate, the signal enters the tilt angle filtering module. This module employs a sliding window mean filter with a window length of 20 sampling points, a sampling frequency of 100Hz, and a corresponding time window of 0.2s. The filter maintains a circular buffer of length 20 in memory. Each time new data arrives, the oldest data is replaced, and the arithmetic mean of all data within the window is recalculated as the current output tilt angle. This design effectively smooths tilt angle fluctuations caused by road bumps, motor vibrations, or high-frequency noise from sensors, ensuring that the subsequent control module receives a stable, continuous, and abrupt tilt angle signal. The filtered tilt angle value is simultaneously fed into both the power assist control module and the braking control module, serving as the core input parameter for dual-channel control.

[0025] In the power assist control module, the filtered slope angle is first mapped to five preset slope ranges: -15° to -5° corresponds to the downhill light assist suppression zone, -5° to 0° corresponds to the downhill transition zone, 0° to 5° corresponds to the flat slope standard assist zone, 5° to 15° corresponds to the uphill medium assist enhancement zone, and 15° to 30° corresponds to the uphill heavy assist enhancement zone. Each range corresponds to a fixed assist level coefficient, which are 0.3, 0.6, 1.0, 1.4, and 1.8, respectively. The mapping process is implemented through a lookup table. The table structure is loaded into the controller's read-only memory during system initialization. During runtime, the corresponding coefficient is directly indexed based on the current slope angle value, without any conditional branches or floating-point operations, ensuring that the mapping process is completed within microseconds. The pedal torque sensor is installed at the bottom crank connection, with a range of 0-50 N·m. The output analog voltage signal is sampled at a frequency of 100 Hz by a 12-bit analog-to-digital converter, converted into a digital torque value, and multiplied by the assist level coefficient to generate the target output torque command for the motor. The product operation is performed in the fixed-point arithmetic unit, avoiding the delay of floating-point operations and ensuring the real-time generation of instructions.

[0026] After generating the target output torque command for the motor, a torque change rate limiting module is added. This module constrains the difference in torque commands between adjacent control cycles, ensuring that the torque change rate does not exceed 20 N·m / s. Specifically, at the beginning of each control cycle, the final output torque command value of the previous cycle is read, and the difference between the newly generated command in the current cycle and the command in the previous cycle is calculated. If the absolute value of the difference exceeds 20 N·m / s multiplied by the control cycle time, the current command value is clamped to the previous cycle value plus or minus the maximum allowable change. This limiting mechanism effectively avoids abrupt changes in motor output torque caused by sudden slope changes or drastic fluctuations in user pedaling torque, preventing abnormal noise, wear, or slippage in the drive chain, gearbox, or wheels due to instantaneous impact loads, thus improving power transmission smoothness and mechanical system durability.

[0027] In the braking control module, the filtered slope angle is first used to determine the vehicle's current slope direction. If the slope angle is greater than zero, it is determined to be an uphill state. In this case, the baseline braking torque is set to zero, meaning no active braking intervention is applied, relying entirely on manual operation by the user or the mechanical braking system. If the slope angle is less than zero, it is determined to be a downhill state. In this case, the baseline braking torque increases linearly with the absolute value of the slope angle, calculated as: Baseline braking torque = Absolute value of slope angle multiplied by 0.5 N·m / °. This linear relationship ensures that the steeper the slope, the greater the system's preset baseline braking force, providing a reasonable benchmark for subsequent vehicle speed correction. The vehicle speed sensor collects current vehicle speed data, with a sampling frequency synchronized with the slope angle at 100Hz. The vehicle speed correction coefficient is obtained through a two-dimensional lookup table. The horizontal axis of the table represents vehicle speed, divided into three intervals: 0-5 km / h, 5-15 km / h, and 15-30 km / h. The vertical axis represents the absolute value of the slope angle, divided into three intervals: 0-5°, 5-15°, and 15-30°. A total of nine combined regions are formed, each region corresponding to a preset vehicle speed correction coefficient, with a value range of 0.8-1.5. The vehicle speed correction coefficient is obtained through a two-dimensional lookup table, with the following preset values: 1.0 for vehicle speeds of 0-5 km / h and inclination angles of 0-5°; 1.2 for 0-5 km / h and 5-15°; 1.5 for 0-5 km / h and 15-30°; 0.9 for 5-15 km / h and 0-5°; 1.1 for 5-15 km / h and 5-15°; 1.3 for 5-15 km / h and 15-30°; 0.8 for 15-30 km / h and 0-5°; 1.0 for 15-30 km / h and 5-15°; and 1.2 for 15-30 km / h and 15-30°. The lookup process uses a bilinear interpolation algorithm, performing a weighted average across four adjacent grid points to ensure the correction coefficient changes smoothly and continuously with vehicle speed and inclination, avoiding abrupt changes in braking torque due to abrupt changes in interval boundaries. The final braking command output value = the basic braking torque reference value multiplied by the vehicle speed correction factor.

[0028] After generating the final braking command output value, a brake pressure gradual change control module is added. This module performs first-order inertial filtering on the braking command, with a time constant set to 0.3s. The filter is implemented using a discretized first-order low-pass filter formula: Among them, y k The output after filtering in the current period, x k For the current cycle's original braking command, y k−1 This is the output after filtering in the previous cycle. β is the filtering coefficient, whose value is calculated from the time constant and the control cycle. This filtering process makes the braking torque command rise or fall smoothly in an exponential manner, avoiding pressure jumps in the solenoid valve due to sudden command changes. This prevents wheel lock-up on slippery roads or jerking sensations on slopes, improving braking comfort and tire grip stability.

[0029] The electronic brake controller employs a proportional solenoid valve structure, achieving a current control accuracy better than 2% and a response time of less than 20ms. The controller receives filtered braking commands, converts them into corresponding drive current values, and drives the solenoid valve coil via pulse-width modulation (PWM) signals to regulate brake fluid pressure, thereby controlling the brake caliper clamping force or brake drum braking torque. The motor driver receives torque commands with a rate-of-change limitation and precisely adjusts the motor phase current using a dual closed-loop control algorithm (current loop and speed loop) to achieve the target torque output. Both execution modules have fault feedback mechanisms; if an actuator response timeout or output deviation exceeds a threshold is detected, it immediately reports to the main controller, triggering a safety degradation process.

[0030] The main control loop module operates with a fixed 10ms cycle, completing the entire process from data acquisition to command output within a single cycle, with a total latency controlled within 5ms (i.e., the effective processing time within a single cycle). Each functional module executes sequentially according to a strict time sequence: first, the inertial measurement unit and pedal torque sensor are triggered to synchronously sample; then, coordinate transformation and complementary filtering calculations are performed; next, sliding window mean filtering is applied; then, the power assist control sub-model and braking control sub-model are executed in parallel; subsequently, commands are processed through the torque change rate limiting and brake pressure gradual change control modules, respectively; finally, the final command is sent to the motor driver and electronic brake controller. The total latency of the entire control chain from data acquisition to command output is controlled within 5ms, ensuring that the system's response speed to slope changes meets the real-time requirements of the fire truck in emergency obstacle avoidance or steep slope start-stop scenarios.

[0031] When the vehicle detects a slope angle exceeding 25° for more than 3 seconds, the hill-start assist mode is automatically activated. In this mode, the motor output torque is maintained at 80% of the torque value at the time of activation to prevent the vehicle from rolling backward due to the user releasing the pedal; simultaneously, the braking system preloads 30% of the base braking torque to provide additional static holding force. The hill-start assist mode continues to operate until the driver depresses the accelerator or brake pedal, or the system detects a filtered slope angle of less than 25° and maintains this state for 100 consecutive control cycles (corresponding to 1 second). This mechanism effectively prevents the vehicle from rolling backward on extremely steep slopes due to operational errors or power interruption, improving the safety of firefighters working at the top of the slope.

[0032] The system also includes an abnormal tilt angle alarm module. This module calculates the difference between the current tilt angle and the tilt angle of the previous cycle in each control cycle. If the absolute value of the difference exceeds 5° for five consecutive cycles, it is determined to be an abnormal tilt angle jump, possibly caused by sensor failure, severe collision, or electromagnetic interference. At this time, the system immediately triggers a self-test program, attempting to restart the inertial measurement unit and reload calibration parameters; simultaneously, it switches to a safety degradation mode, limiting the power assist output to 50% of the standard value, and the braking system enters a fully mechanical backup state, meaning it only responds to manual braking operations, and electronic braking commands are forcibly reset to zero. This dual safety mechanism ensures that the vehicle retains basic controllability in the event of sensor failure or data anomalies, preventing serious accidents caused by system malfunction.

[0033] The system also includes a data storage module. This module records five core parameters in each control cycle: slope angle, assist torque command, braking command, vehicle speed, and pedal torque. The data is stored in a circular buffer in non-volatile memory, with a maximum storage time of the most recent two hours of driving data. The stored data can be used for post-event analysis of the vehicle's control performance on specific slopes, identifying areas for control parameter optimization, or as objective evidence in accident investigations. The data export interface supports encrypted transmission to ground station software via the diagnostic port, allowing engineers to perform in-depth analysis and system iteration.

[0034] The adaptive power-assisted braking control system for slope tilt angle of the fire-assisted vehicle includes: an inertial measurement unit for real-time acquisition of the vehicle's angular velocity and linear acceleration data in three-dimensional space; a data preprocessing module for time synchronization and coordinate system transformation of the acquired raw angular velocity and linear acceleration data, unifying them to the vehicle's body coordinate system; a slope tilt angle calculation module for calculating the vehicle's current pitch angle relative to the horizontal plane based on the transformed angular velocity and linear acceleration data using a complementary filtering algorithm; a tilt angle filtering module for performing sliding window mean filtering on the calculated slope tilt angle to eliminate high-frequency noise interference and obtain a stable and reliable slope tilt angle output value; and a power-assisted control module for inputting the filtered slope tilt angle into the power-assisted control sub-model, and according to a preset... The gradient range division rules are mapped to assist level coefficients and multiplied with pedal torque to generate the target output torque command for the motor. The braking control module inputs the filtered slope angle into the braking control sub-model, determines the slope direction based on the sign of the angle, calculates the baseline braking torque value based on the absolute value of the angle, and then determines the vehicle speed correction coefficient by looking up a table, multiplying the results to obtain the final braking command output value. The motor drive execution module receives the target output torque command for the motor and controls the motor to output the corresponding torque. The electronic braking execution module receives the final braking command output value and adjusts the brake caliper clamping force or brake drum braking torque. The main control loop module continuously calls the above modules in a loop during vehicle operation to achieve dynamic closed-loop control under changes in slope angle.

[0035] The inertial measurement unit (IMU) includes a three-axis gyroscope and a three-axis accelerometer, fixedly mounted at the geometric center of the vehicle frame, with its mounting plane parallel to the vehicle's longitudinal plane of symmetry. The data preprocessing module uses hardware synchronous pulse triggering for acquisition, and coordinate system transformation is achieved through a direction cosine matrix. The slope angle calculation module incorporates a complementary filter, with a gyroscope weighting coefficient of 0.95 and an accelerometer weighting coefficient of 0.05. The slope angle filtering module uses a 20-point sliding window mean filter. The power assist control module incorporates a slope interval mapping table containing five slope angle intervals and their corresponding power assist level coefficients. The braking control module incorporates a two-dimensional lookup table structure, with the horizontal axis representing the vehicle speed interval and the vertical axis representing the absolute value interval of the slope angle, outputting a vehicle speed correction coefficient. The motor drive execution module includes a dual closed-loop controller with current and speed loops, outputting torque commands after rate-of-change limiting. The electronic braking execution module includes a proportional solenoid valve drive circuit, outputting braking commands after first-order inertial filtering. The main control loop module runs with a fixed period of 10ms. Within a single period, it completes the entire process from data acquisition to instruction output, with the total delay controlled within 5ms (i.e., the effective processing time within a single period). Each module is executed sequentially according to a fixed timing sequence.

[0036] The system also includes a hill-start assist activation module, which automatically activates hill-start assist mode when the absolute value of the slope angle exceeds 25° for 3 seconds. In this mode, the system maintains motor torque output and preloads braking pressure. The system also includes an abnormal tilt angle alarm module, which triggers a system self-check and switches to a safety degradation mode when a tilt angle calculation value jumps by more than 5° within five consecutive control cycles. In this mode, the power assist output is limited to 50% of the standard value, and the braking system enters a fully mechanical backup state. The system also includes a data storage module, which records the slope angle, power assist torque command, braking command, vehicle speed, and pedal torque data for each control cycle, forming a driving log for post-event analysis and system optimization.

[0037] The method and system described in this embodiment directly measure the vehicle's pitch angle as the slope inclination angle, avoiding the cumulative errors caused by indirect calculations from traditional acceleration sensors. A dual filtering mechanism of complementary filtering and sliding mean ensures high stability of the inclination angle data under both dynamic and static conditions. An independently designed dual-channel control model for power assist and braking achieves precise coordination between power and braking. Torque change rate limiting and gradual braking pressure control improve system response smoothness. A dual safety mechanism of slope parking assist and abnormal alarm ensures basic safety under extreme conditions. The overall solution meets the high-intensity, high-safety operation requirements of fire-assisted vehicles in complex terrain, demonstrating significant technological advancement and practical value.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for adaptive power-assisted braking control of a fire-fighting vehicle on a slope, characterized in that, include: The inertial measurement unit, composed of a three-axis gyroscope and a three-axis accelerometer, collects real-time data on the vehicle's angular velocity and linear acceleration in three-dimensional space. The collected raw angular velocity and linear acceleration data are synchronized in time and transformed in coordinate system to be unified into the vehicle body coordinate system; Based on the transformed angular velocity and linear acceleration data, a complementary filtering algorithm is used to calculate the vehicle's current pitch angle relative to the horizontal plane. This pitch angle is the current slope inclination angle. The calculated slope inclination angle is subjected to sliding window mean filtering to eliminate high-frequency noise interference and obtain a stable and reliable slope inclination angle output value. The filtered slope angle is input into the power assist control sub-model. The sub-model maps the slope angle to the corresponding power assist level coefficient according to the preset slope interval division rules. The power assist level coefficient is multiplied with the user pedaling torque collected by the pedal torque sensor to generate the target output torque command of the motor. The filtered slope angle is simultaneously input into the braking control sub-model. The sub-model determines whether the vehicle is going uphill or downhill based on the sign of the slope angle, calculates the basic braking torque reference value based on the absolute value of the slope angle, and then combines the current vehicle speed data collected by the vehicle speed sensor to determine the vehicle speed correction coefficient by looking up a table. The basic braking torque reference value is multiplied by the vehicle speed correction coefficient to obtain the final braking command output value. The target output torque command of the motor is sent to the motor driver to control the motor to output the corresponding torque. The final braking command output value is sent to the electronic brake controller to adjust the brake caliper clamping force or the brake drum braking torque. During vehicle operation, the system continuously and cyclically executes data acquisition, tilt angle calculation, filtering, power assist command generation, braking command generation, and control execution steps to achieve dynamic closed-loop control under slope tilt angle changes. The filtered slope angle is input into the braking control sub-model to generate the final braking command output value, including: When the slope angle is greater than zero, it is determined to be an uphill state, and the base braking torque reference value is set to zero. When the slope angle is less than zero, it is determined to be a downhill state. The basic braking torque reference value increases linearly with the absolute value of the slope angle. The calculation formula is: Basic braking torque reference value = absolute value of slope angle × 0.5 N·m / °; Based on the current vehicle speed data, the vehicle speed correction coefficient is determined by a two-dimensional lookup table method. The horizontal axis of the table represents the vehicle speed range, and the vertical axis represents the range of absolute values ​​of the tilt angle. The output is the preset vehicle speed correction coefficient. The final braking command output value is obtained by multiplying the baseline braking torque value by the vehicle speed correction coefficient.

2. The adaptive power-assisted braking control method for slope tilt angle of fire-assisted vehicle according to claim 1, characterized in that, The acquired raw angular velocity and linear acceleration data are synchronized in time and transformed in coordinate system to be unified to the vehicle body coordinate system, including: The main controller sends a hardware synchronization pulse signal to simultaneously trigger the data acquisition actions of the three-axis gyroscope and the three-axis accelerometer, ensuring that the timestamp error between the two sets of data is less than 0.1ms; The direction cosine matrix method is used to rotate the measurement values ​​in the original coordinate system of the sensor to the body coordinate system with the vehicle's forward direction as the X-axis and the vertical upward direction as the Z-axis. The direction cosine matrix is ​​loaded during the system initialization phase and used for real-time coordinate transformation in each control cycle.

3. The adaptive power-assisted braking control method for slope tilt angle of fire-assisted vehicle according to claim 2, characterized in that, The complementary filtering algorithm is used to calculate the vehicle's current pitch angle relative to the horizontal plane, including: The pitch axis angular velocity data output by the gyroscope is numerically integrated to obtain the integrated tilt angle at the current moment; The observation tilt angle at the current moment is calculated using the Z-axis and X-axis components of the accelerometer in the vehicle coordinate system through the arctangent function; The integrated tilt angle and the observed tilt angle are weighted and summed using weighted coefficients, where the weighted coefficient for the gyroscope integral term is 0.95 and the weighted coefficient for the accelerometer observation term is 0.05, to obtain a preliminary tilt angle estimate as the current slope tilt angle.

4. The adaptive power-assisted braking control method for slope tilt angle of the fire-assisted vehicle according to claim 3, characterized in that, The calculated slope angle is subjected to sliding window mean filtering to eliminate high-frequency noise interference and obtain a stable and reliable slope angle output value, including: Maintain a circular buffer with a length of 20 sampling points in memory, with a sampling frequency of 100Hz; Each time new tilt angle data arrives, the oldest data is replaced and the arithmetic mean of all data in the window is recalculated as the current output tilt angle.

5. The adaptive power-assisted braking control method for slope tilt angle of fire-assisted vehicle according to claim 4, characterized in that, The filtered slope angle is input into the power assist control sub-model to generate the target output torque command for the motor, including: According to the preset slope range division rules, the slope angle is mapped to the assistance level coefficient. The slope range includes: -15° to -5° corresponding to a coefficient of 0.3; -5° to 0° corresponding to a coefficient of 0.6; 0° to 5° corresponding to a coefficient of 1.0; 5° to 15° corresponding to a coefficient of 1.4; 15° to 30° corresponding to a coefficient of 1.

8. The mapped assist level coefficient is multiplied by the user's pedaling torque collected by the pedal torque sensor to generate the target output torque command for the motor.

6. The adaptive power-assisted braking control method for slope tilt angle of fire-assisted vehicle according to claim 5, characterized in that, After generating the target output torque command for the motor, torque change rate limiting processing is added, including: Calculate the difference between the torque command in the current cycle and the torque command in the previous cycle; If the absolute value of the difference exceeds 20 N·m / s multiplied by the control cycle time, the current command value will be clamped to the previous cycle value plus or minus the maximum allowable change amount to ensure that the torque change rate does not exceed 20 N·m / s.

7. The adaptive power-assisted braking control method for slope tilt angle of fire-assisted vehicle according to claim 1, characterized in that, After generating the final braking command output value, a gradual braking pressure control process is added, including: The braking command is filtered by a first-order inertial element with a time constant of 0.3s. Discretized first-order low-pass filter formula: Where y k The output after filtering in the current period, x k For the current cycle's original braking command, y k−1 This is the output after filtering in the previous cycle, and β is the filtering coefficient calculated from the time constant and the control cycle.

8. A slope-adaptive power-assisted braking control system for a fire-fighting vehicle, characterized in that, The method for adaptive power-assisted braking control of a fire-assisted vehicle with slope tilt angle according to any one of claims 1 to 7 includes: An inertial measurement unit is used to collect real-time data on the vehicle's angular velocity and linear acceleration in three-dimensional space using a three-axis gyroscope and a three-axis accelerometer. The data preprocessing module is used to synchronize the collected raw angular velocity and linear acceleration data in time and transform the coordinate system to unify them into the vehicle body coordinate system. The slope angle calculation module is used to calculate the vehicle's current pitch angle relative to the horizontal plane based on the transformed angular velocity data and linear acceleration data, using a complementary filtering algorithm. The tilt angle filtering module is used to perform sliding window mean filtering on the calculated slope tilt angle to eliminate high-frequency noise interference and obtain a stable and reliable slope tilt angle output value. The power assist control module is used to input the filtered slope angle into the power assist control sub-model, map it into a power assist level coefficient according to the preset slope interval division rules, and multiply it with the pedal torque to generate the target output torque command of the motor. The braking control module is used to input the filtered slope angle into the braking control sub-model, determine the slope direction based on the sign of the slope angle, calculate the basic braking torque reference value based on the absolute value of the slope angle, and then determine the vehicle speed correction coefficient by looking up a table in combination with the current vehicle speed. After multiplying, the final braking command output value is obtained. The motor drive execution module is used to receive the target output torque command of the motor and control the motor to output the corresponding torque; The electronic brake actuator module is used to receive the final brake command output value and adjust the brake caliper clamping force or brake drum braking torque. The main control loop module is used to continuously and cyclically call the above modules during vehicle operation to achieve dynamic closed-loop control under changes in slope angle.

9. The adaptive power-assisted braking control system for slope tilt angle of the fire-assisted vehicle according to claim 8, characterized in that, The system also includes: The hill start assist activation module is used to automatically activate the hill start assist mode when the absolute value of the slope angle exceeds 25° and lasts for 3 seconds. In this mode, the motor torque output is maintained and the braking pressure is preloaded. The abnormal tilt angle alarm module is used to trigger the system self-test and switch to the safety degradation mode when the tilt angle calculation value jumps by more than 5° within 5 consecutive control cycles. At this time, the power assist output is limited to 50% of the standard value and the braking system enters the full mechanical backup state. The data storage module is used to record the slope angle, assist torque command, braking command, vehicle speed and pedal torque data in each control cycle, forming a driving log for post-event analysis and system optimization.

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