A hill zero speed holding and anti-roll system for an electric four-wheeled vehicle

Abstract

The application provides a hill zero-speed keeping and anti-slip system for an electric four-wheeled vehicle. The system does not need to be additionally equipped with a slope sensor, an acceleration sensor, an electronic hand brake and other additional hardware, and can realize anti-slip control only by using a motor self-encoder and an original vehicle FOC control system, so that the hardware cost is reduced, and the faults caused by sensor drift and mechanical mechanism wear are avoided; 0.8 mm level slip trend early identification is adopted, and the vehicle slip displacement control is within 1 mm; the position closed-loop PI control can be self-adapted to different slope and load changes, supports hill stable zero-speed hovering, and the control precision and adaptability are far higher than those of a traditional open-loop scheme. The whole process of triggering, keeping and exiting is automatically completed, and any additional operation of the driver is not needed, the brake is automatically released to enter a preparation state, the slip trend is automatically triggered to control, the accelerator is automatically stepped down to smoothly exit, the hill parking function of the mechanical hand brake is completely replaced, and the problem of complicated hill starting operation of the traditional scheme is solved.

Description

Technical Field

[0001] This invention relates to the field of new energy control technology, and in particular to an electric four-wheeled vehicle ramp zero-speed holding and anti-roll-off system, method, electronic equipment and computer-readable storage medium. Background Technology

[0002] With the rapid development of the new energy short-distance travel industry, the penetration rate of electric four-wheeled vehicles in scenarios such as elderly mobility, urban logistics, and community commuting continues to increase. Slope driving is one of the core operating conditions in their daily use. The problem of vehicle rollback during slope starting and parking is a core pain point affecting the driving safety and operation experience of electric four-wheeled vehicles. It can cause driver panic at best, and lead to traffic accidents such as rear-end collisions and skidding at worst.

[0003] Current mainstream anti-rollover technologies for electric four-wheeled vehicles have inherent defects that cannot be avoided, as follows:

[0004] 1. Slope sensor-dependent open-loop control scheme: This scheme measures the slope angle by adding slope and acceleration sensors and presets a corresponding anti-slip current. This scheme requires additional hardware costs, and the sensors are susceptible to vehicle vibration, temperature drift, and road bumps, with measurement errors reaching ±3°. It cannot adapt to load fluctuations caused by changes in passenger and cargo weight, and the open-loop control lacks displacement feedback, making it prone to slippage or overheating due to overcurrent.

[0005] 2. Mechanical locking auxiliary solution: Relying on mechanical handbrake, electronic handbrake and gearbox parking lock to achieve parking on slopes, it requires manual operation by the driver. Starting on slopes is cumbersome and extremely unfriendly to novice drivers. Electronic handbrake and locking mechanism have complex structure and high cost. There is a delay of more than 200ms between locking and releasing, which can easily cause the vehicle to lurch or roll backwards when starting.

[0006] 3. Speed-triggered lag control scheme: The anti-slip braking is triggered by detecting the reverse speed of the motor. The control can only be started when the vehicle shows obvious slippage (reverse speed ≥ 50 rpm, corresponding slippage displacement ≥ 5 cm). The control lag is serious and zero-speed hovering cannot be achieved. In addition, the speed detection accuracy of the zero-speed range encoder is low, which is prone to false triggering or control failure.

[0007] 4. Simplified square wave stall current control solution: This solution injects a fixed stall current through square wave control of the brushless motor. At zero speed, the torque fluctuates greatly, the noise is obvious, and the torque cannot be adjusted adaptively. This can easily lead to slippage or motor overheating and burnout, and it cannot achieve stable hovering for a long time. Summary of the Invention

[0008] To address the technical problems existing in the prior art, the present invention provides the following technical solution:

[0009] On the one hand, an electric four-wheeled vehicle ramp zero-speed holding and anti-slippage system is provided, including a signal acquisition layer, a core control layer, a drive execution layer, and a safety monitoring layer, wherein:

[0010] The signal acquisition layer is used to acquire the travel signals of the brake pedal and accelerator pedal, as well as the rotor pulse signal of the motor's built-in incremental quadrature encoder, to provide the system with driver operation intentions and vehicle displacement data.

[0011] The core control layer includes a built-in trigger logic judgment unit, a zero-speed position closed-loop control algorithm unit, and a field-oriented control (FOC) algorithm unit. The trigger logic judgment unit is used to complete the trigger and exit logic judgment of the anti-slip control based on the input signal. The zero-speed position closed-loop control algorithm unit is used to adaptively calculate the motor q-axis current setpoint to balance the gravity component of the slope through position closed-loop PI control. The field-oriented control (FOC) algorithm unit is used to realize the decoupled control of the motor dq-axis current and output the SVPWM drive signal.

[0012] The drive execution layer is used to convert the drive signal of the core control layer into a three-phase drive current of the motor, and output a zero-speed braking torque opposite to the direction of the slope through the permanent magnet synchronous motor to achieve zero-speed hovering of the vehicle.

[0013] The security monitoring layer is used to monitor system operating parameters in real time and execute graded fault protection strategies.

[0014] The system does not rely on additional slope sensors, acceleration sensors, or mechanical parking lock mechanisms throughout the entire process. It achieves zero-speed maintenance and anti-slippage on the slope solely through closed-loop position control based on encoder displacement feedback.

[0015] Preferably, the signal acquisition layer includes a pedal status acquisition module and an encoder signal acquisition module; the pedal status acquisition module uses an automotive-grade Hall linear displacement sensor to acquire pedal travel signals at a sampling frequency of 1kHz; the encoder signal acquisition module acquires pulse signals from the motor quadrature encoder at a sampling frequency of 10kHz, and converts the rotor angular displacement into the actual linear displacement of the vehicle through a displacement calculation formula, achieving a displacement detection accuracy of 0.1mm.

[0016] Preferably, the zero-speed position closed-loop control algorithm unit incorporates a vehicle displacement calculation formula:

[0017] In the formula:

[0018] This represents the actual linear displacement of the vehicle. The radius of the wheel's rolling motion. The amount of pulse change captured by the encoder. The reduction ratio of the motor reducer. This refers to the number of pulses per encoder revolution.

[0019] Simultaneously, it incorporates the position closed-loop PI control algorithm formula:

[0020] In the formula:

[0021] The given value for the q-axis current of the motor. This is the position ring proportionality coefficient. These are the integral coefficients of the position loop. For positional error, , The target position zero point is locked when maintaining zero speed. This represents the actual displacement of the vehicle. This is the time integral operation for the position error.

[0022] Preferably, the field-oriented control (FOC) algorithm unit employs... Maximum torque / current ratio control strategy, with built-in electromagnetic torque formula:

[0023] In the formula:

[0024] For the electromagnetic torque of the motor, This represents the number of pole pairs of the motor. For rotor permanent magnet flux linkage, This represents the actual q-axis current of the motor; the d-axis current is set by... This achieves complete decoupling of excitation current and torque current, maximizing torque output efficiency during zero-speed stall.

[0025] Preferably, the drive execution layer includes a three-phase full-bridge FOC drive module and a permanent magnet synchronous motor execution unit; the three-phase full-bridge FOC drive module adopts a three-phase full-bridge inverter topology, executes SVPWM modulation at a control frequency of 20kHz, and collects three-phase current in real time to feed it back to the core controller to form a current closed loop; the permanent magnet synchronous motor execution unit outputs a constant zero-speed stall torque based on the interaction between the stator magnetic field and the rotor permanent magnet, balancing the gravity downhill component of the ramp.

[0026] Preferably, the safety monitoring layer incorporates a three-level protection strategy: early warning level derating protection, fault level limiting protection, and danger level emergency shutdown protection; it collects motor phase current, winding temperature, DC bus voltage, and encoder signal status in real time at a sampling frequency of 1kHz, triggers corresponding protection actions in fault conditions, and sends fault codes via the CAN bus.

[0027] On the other hand, a method for maintaining zero speed and preventing slippage on an electric four-wheeled vehicle on a slope is provided, based on the system described above, including the following steps:

[0028] Step 1: Power on the system for initialization and parameter calibration, complete the self-test of all modules and load the vehicle's inherent parameters and control parameters;

[0029] Step 2: Real-time acquisition of pedal status and determination of preparatory mode. Based on the pedal travel signal, the driver's operating intention is determined, and the anti-rollover preparatory state is entered when the conditions are met.

[0030] Step 3: Encoder signal calculation and anticipation of slope tendency identification. The actual displacement of the vehicle is calculated by the encoder pulse signal, and the zero speed holding control is triggered after identifying the slope tendency.

[0031] Step 4: Zero-speed position closed-loop control and FOC drive execution. The q-axis current setpoint is adaptively calculated through position closed-loop PI control, and the braking torque of the drive motor is output based on FOC vector control to achieve zero-speed hovering of the vehicle.

[0032] Step 5: Hovering state safety monitoring and status maintenance, real-time monitoring of system operating parameters, execution of graded protection strategies, and continuous monitoring of driver's operating intentions;

[0033] Step 6: Smoothly exit anti-slip mode and switch to normal drive. After detecting that the accelerator pedal is effectively pressed, the mode is smoothly switched through linear torque transition, and normal drive is restored.

[0034] Preferably, in step 3, the criterion for determining the slope tendency is: if the absolute value of the vehicle displacement is detected to be >0.8mm for three consecutive sampling cycles, and the displacement continues to increase, and the speed direction is opposite to the vehicle's forward direction, then when zero-speed holding control is triggered, the current position is locked as the target zero point.

[0035] Preferably, in step 4, during the zero-speed holding control process, the position loop control frequency is 10kHz and the current loop control frequency is 20kHz. The q-axis current is continuously adjusted through closed-loop control so that the actual displacement of the vehicle is always kept at the target zero point, adaptively adapting to 0-30° slopes and different load conditions.

[0036] Preferably, in step 6, the mode switching process adopts a 200ms linear gradient curve to smoothly transition the q-axis current setpoint of the anti-slip mode to the current setpoint of the drive mode. During the transition, the position loop closed-loop control remains effective to ensure that there is no slippage or swerving during the switching process.

[0037] On the other hand, an electronic device is provided, comprising: a processor; and a memory storing computer-readable instructions, which, when executed by the processor, implement the method described above.

[0038] On the other hand, a computer-readable storage medium is provided, wherein at least one instruction is stored therein, the at least one instruction being loaded and executed by a processor to implement the above method.

[0039] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0040] 1. No additional hardware such as slope sensors, acceleration sensors, and electronic handbrakes is required. Anti-slip control can be achieved using only the motor's built-in encoder and the original vehicle's FOC control system, reducing hardware costs by more than 60%. At the same time, it avoids failures caused by sensor drift and mechanical wear, and improves the system's mean time between failures by more than 80%.

[0041] 2. Advanced closed-loop control for true zero-speed hovering: This solution uses 0.8mm-level advanced slope tendency recognition instead of the traditional "post-slip correction" solution. The slip displacement is controlled within 1mm, which is far superior to the existing level in the industry. The position closed-loop PI control can adaptively adapt to different slopes and load changes, and supports stable zero-speed hovering on slopes up to 30°. The control accuracy and adaptability far exceed those of traditional open-loop solutions.

[0042] 3. High-efficiency FOC vector control for stable hovering over extended periods: This solution adopts... The FOC vector control strategy improves torque output efficiency by 30% when stalled at zero speed, significantly reduces motor heat generation, and enables stable zero-speed hovering for more than 5 minutes. It solves the pain points of traditional square wave control, such as severe heat generation and inability to maintain the position for a long time when stalled. At the same time, the zero-speed torque output is smooth, without vibration or noise, and the driving comfort is significantly improved.

[0043] 4. Fully automatic intelligent control, simplifying driving operation: This solution completes the entire process of triggering, holding, and exiting automatically without any additional operation by the driver. Releasing the brake automatically enters the ready state, and the control is automatically triggered when there is a tendency to roll backward. Pressing the accelerator automatically and smoothly exits the slope parking function, completely replacing the mechanical handbrake. It solves the problem of cumbersome operation when starting on a slope in traditional solutions, and is especially suitable for novice drivers and elderly mobility scooter users.

[0044] 5. Automotive-grade multi-layered safety protection, safe and reliable under all operating conditions: This solution incorporates multi-level protection strategies such as overcurrent, overheating, overvoltage, and sensor fault protection, monitors the system's operating status throughout the process, and quickly triggers protection in the event of a fault; the dual closed-loop control architecture can quickly correct anomalies, meets the automotive-grade safety requirements for new energy vehicles, and can be widely used in multiple fields such as low-speed mobility vehicles, urban logistics vehicles, and new energy passenger vehicles. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of the system architecture provided in an embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of the layered real-time communication architecture of the system provided in the embodiments of the present invention;

[0048] Figure 3 This is a flowchart of a method provided in an embodiment of the present invention;

[0049] Figure 4 This is a schematic diagram of a 200ms linear gradient curve provided in an embodiment of the present invention. Detailed Implementation

[0050] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0051] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0052] In the embodiments of this invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning. Similarly, the terms "of," "corresponding (relevant)," and "corresponding" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning.

[0053] In this embodiment of the invention, sometimes a subscript such as W1 may be mistakenly written as a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0054] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0055] In this embodiment, the applicable new energy vehicle models for the system are determined based on their specific types.

[0056] In this embodiment, the conventional hardware facilities involved in the system, such as power supply, vehicle system, and display, can still use the existing tram architecture and control system.

[0057] The improvement plan for this system will be further described below.

[0058] This solution proposes an electric four-wheeled vehicle ramp zero-speed holding and anti-slippage system without additional sensors and using a pure algorithm closed loop. It relies solely on the motor's built-in encoder and field-oriented control (FOC) technology to achieve micron-level slope slippage trend recognition and zero-speed stable hovering by adaptively balancing the slope gravity component through a position closed loop.

[0059] Example 1: System Composition

[0060] The system adopts a layered, modular automotive-grade architecture. The core control is entirely based on the characteristics of the motor itself and the algorithm, with no redundant hardware. It is divided into four layers: signal acquisition layer, core control layer, drive execution layer, and safety monitoring layer.

[0061] like Figure 1 As shown, the principles of each module are as follows:

[0062] (a) Signal Acquisition Layer

[0063] The signal acquisition layer is the system's sensing input end, responsible for acquiring the driver's operating intentions and the motor rotor status, providing accurate input for the control logic, and includes two core acquisition modules:

[0064] 1. Pedal Status Acquisition Module

[0065] The module collects the travel signals of the brake pedal and accelerator pedal in real time, and transmits the filtered digital value of the pedal travel to the core controller at a fixed sampling frequency of 1kHz. After completing the logical judgment, the core controller outputs a mode switching command. By accurately identifying the driver's operating intention, it provides logical criteria for triggering, holding, and disengaging the anti-rollover control.

[0066] This module can use an automotive-grade Hall-effect linear displacement sensor to convert the pedal mechanical travel into a 0-5V differential analog voltage signal, which is transmitted to the 16-bit ADC interface of the core controller through a shielded twisted pair cable to avoid vehicle electromagnetic interference; it has a built-in travel threshold calibration unit to pre-calibrate the accelerator pedal release threshold and the accelerator pedal trigger threshold, filtering out pedal idle travel and vibration interference.

[0067] 2. Encoder signal acquisition module

[0068] The module collects the angular displacement and angular velocity signals of the motor rotor in real time and transmits pulse signals to the core controller at a sampling frequency of 10kHz. After the core controller completes the displacement and velocity calculation, it outputs the slope trend identification result and the position closed-loop control command.

[0069] After acquiring signals, this module can convert them into the vehicle's actual displacement and motion trend, making it the core sensing unit of this system that eliminates the need for a slope sensor. It employs an incremental quadrature encoder integrated into the motor (default 1024 lines or higher, automotive grade), outputting A and B phase quadrature pulses and a Z phase zero-point signal. The core controller captures pulses through an advanced timer, calculates the rotor angular displacement change through pulse counting, and solves for the rotor speed using the M / T method. Finally, it converts the rotor's rotational motion into the vehicle's linear displacement using the vehicle's inherent mechanical parameters, achieving a displacement detection accuracy of 0.1mm.

[0070] (II) Core Control Layer

[0071] The core control layer is the system's computational hub, employing an automotive-grade 32-bit MCU (STM32F103RCT6) as the main control chip. It integrates peripherals such as an ADC, advanced timers, and a CAN bus, and is responsible for the entire system's logic judgment, algorithm calculation, and instruction output. It includes the following units:

[0072] 1. Trigger logic judgment unit

[0073] This unit uses pedal status and rotor displacement signals to perform triggering, holding, and exit logic judgments for anti-rollover control, eliminating false triggering and control failure. It incorporates a multi-condition and logic judgment algorithm, triggering zero-speed holding control only when all three conditions are met simultaneously: "brake pedal fully released + accelerator pedal not depressed + vehicle exhibiting a continuous tendency to roll backward." When the accelerator pedal is detected to be effectively depressed, smooth exit logic is triggered.

[0074] 2. Zero-speed position closed-loop control algorithm unit

[0075] This unit is the core innovative unit of this system. It automatically calculates the motor torque required to balance the gravity component of the ramp through position closed-loop PI control. It can adapt to different slopes and loads without the need for a slope sensor and output precise current control commands.

[0076] Technical principles and formula definitions:

[0077] ① Vehicle displacement calculation formula, achieving accurate conversion from rotor angular displacement to vehicle linear displacement:

[0078]

[0079] In the formula:

[0080] The actual linear displacement of the vehicle (unit: m);

[0081] The wheel rolling radius (unit: m, a vehicle inherent parameter).

[0082] The amount of pulse change captured by the encoder;

[0083] This refers to the reduction ratio of the motor reducer (an inherent parameter of the vehicle).

[0084] This refers to the number of pulses per encoder revolution (number of lines, inherent parameters of the motor).

[0085] This refers to the circumference of the wheel.

[0086] The formula mechanism is as follows:

[0087] The rotor rotation pulse change is obtained by counting encoder pulses. Combined with the vehicle's mechanical transmission parameters, the rotor rotation motion is accurately converted into the vehicle's linear displacement, achieving displacement detection at the 0.1mm level, and providing a data foundation for the advanced identification of slope slip trend.

[0088] ② Position closed-loop PI control algorithm, outputting the q-axis current setpoint:

[0089] ,

[0090] In the formula:

[0091] The given value for the quadrature axis (q-axis) current of the motor (unit: A); This is the position loop proportional coefficient, used to quickly respond to position errors and counteract the slope tendency; The position loop integral coefficient is used to eliminate static position error and ensure zero hovering accuracy. For positional error, ,in The target position is (locked at 0 when maintaining zero speed). This represents the actual vehicle displacement detected by the encoder. This is the time integral calculation for the position error from 0 to the current time t.

[0092] In zero-speed hold mode, the target position is fixed at the zero point of the trigger moment. When the vehicle shows a tendency to roll backward, the actual displacement... If the value is not zero, a positional error will occur. The proportional term rapidly outputs the corresponding current to counteract the sloping trend, while the integral term continuously eliminates static errors, ultimately resulting in automatic adjustment. The size of the slope allows the vehicle to return to the target zero point, and it can adaptively balance the gravity sliding component of different slopes without measuring the slope, completely eliminating the dependence on slope sensors.

[0093] 3. Field Oriented Control (FOC) Algorithm Unit

[0094] The function of FOC is to achieve decoupled control of the motor's dq axis current, converting the current command of the core controller into a stable and efficient motor drive signal, and ensuring accurate torque output at zero speed.

[0095] FOC principle: using The maximum torque / current ratio control strategy for surface-mounted permanent magnet synchronous motors (SPMSMs) ensures that the electromagnetic torque is completely linearly related to the q-axis current. The core electromagnetic torque formula is as follows:

[0096]

[0097] In the formula:

[0098] The electromagnetic torque of the motor (unit: N·m); This represents the number of pole pairs of the motor (an inherent parameter). The rotor permanent magnet flux linkage (unit: Wb, inherent parameter); 3 / 2 is the actual q-axis current of the motor (unit: A); 3 / 2 is the coordinate transformation coefficient.

[0099] In a surface-mount permanent magnet synchronous motor, the inductances of the direct axis (d-axis) and quadrature axis (q-axis) are equal, and the electromagnetic torque is only proportional to the q-axis current. The electromagnetic torque is determined by setting the d-axis current setpoint. This achieves complete decoupling of excitation current and torque current, with all stator current used to generate torque. The output efficiency is highest at zero speed stall, and the motor heat generation is minimal.

[0100] The algorithm execution flow is as follows: three-phase current acquisition → Clark transformation → Park transformation → current loop PI control → inverse Park transformation → SVPWM modulation → drive signal output.

[0101] (III) Driver Execution Layer

[0102] The drive execution layer is the system's execution terminal, responsible for converting control commands into motor mechanical torque to achieve zero-speed vehicle maintenance. It contains two core units:

[0103] 1. Three-phase full-bridge FOC drive module

[0104] This module receives the SVPWM signal from the core controller, outputs three-phase drive current to the motor, and simultaneously feeds back the phase current sampling value in real time, forming a current closed loop.

[0105] The module converts the SVPWM signal output from the core controller into three-phase drive current for the motor, achieving precise torque control. It employs a three-phase full-bridge inverter topology, consisting of six automotive-grade N-channel MOSFETs. These MOSFETs receive six complementary PWM signals from the core controller via a gate driver chip, controlling the switching of the power transistors and converting the DC bus voltage into a three-phase sinusoidal AC current with controllable amplitude, frequency, and phase. An integrated milliohm-level sampling resistor collects the three-phase current in real-time at a 20kHz frequency, feeding it back to the core controller for closed-loop current control.

[0106] 2. Permanent Magnet Synchronous Motor (PMSM) Actuation Unit

[0107] This module receives the three-phase drive current and outputs the corresponding electromagnetic torque. At the same time, it feeds back the rotor status to the core controller in real time through its built-in encoder, forming a position closed loop.

[0108] The module outputs braking torque in the opposite direction to the slope, balancing the gravitational component of the slope and achieving zero-speed hovering. Based on the principle of electromagnetic induction, a sinusoidal current is applied to the three-phase stator windings to generate a stationary stator magnetic field, which interacts with the magnetic field of the rotor permanent magnet to produce a constant zero-speed stall torque. The torque direction is opposite to the slope direction, counteracting the gravitational component and keeping the vehicle stably in a fixed position.

[0109] (iv) Security monitoring layer

[0110] The safety monitoring layer is the system's safety assurance unit, responsible for monitoring the entire operating condition and fault protection. It meets automotive-grade safety requirements, and its core is an automotive-grade safety protection module. It transmits monitoring parameters to the core controller at a frequency of 1kHz. In the event of a fault, it triggers protection actions through the interrupt interface and sends fault codes to the vehicle controller through the CAN bus, triggering light and sound alarms.

[0111] The module monitors system operating parameters in real time, identifies fault states, and triggers tiered protection to prevent motor overcurrent and overheating damage and safety accidents caused by control failure. It collects motor phase current, DC bus voltage, motor winding temperature, and controller PCB temperature in real time through sampling circuits; identifies sensor faults through encoder signal verification and identifies abnormal operating signals through pedal signal redundancy verification; and incorporates a three-level protection strategy: derating for warning level, limiting for fault level, and shutdown for danger level.

[0112] like Figure 2 As shown, this system adopts a layered real-time communication architecture to ensure the real-time performance and reliability of control. The specific rules are as follows:

[0113] 1. Communication Interface and Real-Time Requirements: The pedal status acquisition and safety monitoring module communicates with the core controller through the ADC interface, with a sampling frequency of 1kHz; the encoder signal acquisition module communicates through the timer capture interface, with a sampling frequency of 10kHz; the FOC drive module communicates through the advanced timer PWM interface, with a current loop control frequency of 20kHz and a position loop control frequency of 10kHz; the vehicle-level signals communicate through the CAN bus, with a baud rate of 500kbps.

[0114] 2. Three-level closed-loop control data flow: The system forms a complete closed-loop feedback logic, with the data flow as follows: signal acquisition layer → core control layer → drive execution layer → signal acquisition layer, comprising three levels of closed loop:

[0115] Inner current loop closed loop: The FOC drive module collects phase current and feeds it back to the core controller. The current loop PI control adjusts the output voltage to ensure that the actual current is consistent with the given value, which is the basis for precise torque control.

[0116] Mid-level position loop closed loop: The encoder collects rotor displacement feedback to the core controller, and the position loop PI control adjusts the q-axis current setpoint to ensure that the vehicle position is consistent with the target zero point, which is the core of zero speed maintenance;

[0117] Outer mode control logic: The pedal acquisition module feeds back the driver's intention, and the core controller completes the mode triggering and exit judgment to ensure that the control logic matches the driver's needs.

[0118] 3. Anti-interference design: Analog signals are transmitted using differential shielding, and digital signals are transmitted using opto-isolation. At the software level, moving average filtering and median filtering are used to eliminate electromagnetic interference and avoid signal distortion caused by vehicle vibration and motor interference.

[0119] The computational logic of this system revolves around "sensorless adaptive zero-speed closed-loop control," and is divided into three core stages:

[0120] 1. Pre-trigger prediction calculation: The core controller continuously collects pedal signals and rotor displacement signals, completes pedal state logic judgment and vehicle displacement trend calculation. When the displacement is continuously increasing and the direction is opposite to the forward direction after three consecutive sampling cycles, it is determined to be a slope trend and triggers control to achieve advanced prediction rather than delayed remedy.

[0121] 2. Zero-speed holding adaptive calculation: After zero-speed holding is triggered, the core controller uses the target zero point as a reference to calculate the position error in real time and outputs the q-axis current setpoint through the PI controller; the FOC algorithm completes the current loop closed-loop control, injects the corresponding current into the motor to generate balanced torque; continuously monitors the vehicle displacement and dynamically adjusts the current magnitude to ensure that the vehicle displacement is always 0, regardless of changes in slope or load.

[0122] 3. Mode switching smoothness calculation: When the accelerator pedal is detected to be pressed, the core controller calculates the torque required by the driver and linearly transitions the q-axis current setpoint of the anti-rollover mode to the current setpoint of the drive mode in 200ms to avoid sudden torque changes that may cause jerking or rolling back, thus achieving a smooth switching.

[0123] The calculation process of this system will be further explained below.

[0124] Example 2: Method for maintaining zero speed and preventing slippage on an electric four-wheeled vehicle on a slope

[0125] like Figure 3 As shown, based on the control application principle of the system in Example 1, the application method of this solution requires no additional operation from the driver and automatically completes the anti-slippage control throughout the entire process. The steps are as follows:

[0126] Step 1: System power-on initialization and parameter calibration

[0127] After the vehicle is powered on, it completes a full module self-test and inherent parameter calibration to ensure that the control parameters match the vehicle hardware, eliminate control errors caused by hardware differences, and provide a stable foundation for subsequent control.

[0128] The implementation process is as follows:

[0129] After the vehicle is powered on, the core controller MCU resets and initializes peripherals such as the ADC, timer, and CAN bus; the pedal acquisition module completes the travel threshold calibration, setting brake pedal travel <5% as fully released and accelerator pedal travel <3% as not depressed; the encoder acquisition module completes zero-point calibration and line count verification; the core controller loads the vehicle's inherent parameters (wheel radius R, reduction ratio i, number of motor pole pairs). ) and control parameters (position loop) Current loop (Protection threshold); the safety monitoring module completes the loading of fault thresholds; after all modules have performed a self-test without faults, the system enters normal standby mode. This ensures normal communication between all system modules, 1:1 matching of control parameters with vehicle hardware, completion of fault self-tests, avoidance of operation with faults, and provides a stable foundation for anti-slip control.

[0130] Step 2: Real-time acquisition of pedal status and determination of ready mode

[0131] By collecting pedal signals at high frequency, the system accurately identifies the driver's operating intentions and enters the ready state only when the driver releases the brake and does not press the accelerator, thus avoiding accidental triggering while driving on flat roads and ensuring smooth driving.

[0132] In standby mode, the pedal acquisition module collects brake and accelerator pedal travel signals at a frequency of 1kHz, and eliminates interference through a 5th-order moving average filter. The core controller executes a logical judgment: the system enters the anti-rollover preparation state only when the brake pedal travel is <5% and the accelerator pedal travel is <3%; otherwise, it maintains normal driving mode. This accurately identifies the driver's intention, filters out pedal free travel and vibration interference, prevents false triggering on flat roads, and prepares for rollover trend detection.

[0133] Step 3: Encoder signal processing and slope trend advance identification

[0134] After entering the preparatory state, the encoder acquisition module acquires orthogonal pulse signals at a frequency of 10kHz; the core controller calculates the actual vehicle displacement using the displacement calculation formula, and simultaneously calculates the vehicle speed; it continuously monitors the displacement data for 3 sampling cycles, and when it detects... When the displacement continues to increase and the velocity direction is opposite to the forward direction, it is immediately determined that there is a tendency to slide downhill, the current position is locked as the target zero point, and the zero speed holding control mode is triggered.

[0135] By using an encoder to achieve micron-level displacement detection, it can identify and trigger control when the vehicle shows a slight tendency to roll backward, which is invisible to the naked eye. This completely eliminates the need for a slope sensor and prevents the vehicle from rolling backward at its source. It achieves 0.8mm-level slope tendency recognition, triggering control before the driver perceives the rollback, thus completely preventing the rollback phenomenon. It eliminates the need for a slope sensor, reducing system costs and adapting to any slope and load conditions.

[0136] Step 4: Zero-speed position closed-loop control and FOC drive execution

[0137] The q-axis current required to balance gravity is automatically calculated through position loop PI closed-loop control, and this is achieved based on FOC vector control. The maximum torque output injects precise stall current into the motor, generating constant zero-speed torque to balance the gravity component of the slope and achieve zero-speed hovering.

[0138] The specific steps are as follows:

[0139] After zero-speed hold is triggered, the core controller acquires the actual displacement of the encoder in real time and calculates the position error. The q-axis current setpoint was calculated using the position loop PI formula. Set the d-axis current setpoint The FOC drive module acquires three-phase current at a frequency of 20kHz and obtains the actual current through Clark and Park transformations. The current loop PI controller compares the actual current with the given value, outputs the given voltage value, and outputs a PWM signal after inverse Park transformation and SVPWM modulation. This signal injects three-phase current into the motor, generating reverse braking torque. The q-axis current is continuously adjusted through closed-loop control until the actual displacement of the vehicle is 0, allowing it to hover stably on the slope.

[0140] It adapts to slope conditions of 0-30° without requiring manual adjustment; The control strategy improves zero-speed stall efficiency by 30%, minimizes motor heat generation, and enables continuous zero-speed hovering for more than 5 minutes; FOC control achieves smooth zero-speed torque output without vibration or noise, and controls the slippage displacement to within 1mm.

[0141] Step 5: Hovering Status Safety Monitoring and Status Maintenance

[0142] During zero-speed holding, the safety monitoring module collects motor phase current, temperature, and bus voltage at a frequency of 1kHz; the core controller performs graded protection: when the phase current exceeds 120% of the rated stall current or the motor temperature exceeds 120℃, derating protection and alarm are triggered; when abnormal encoder or pedal signals are detected, emergency stop protection is triggered; at the same time, the pedal status is continuously monitored, and when the accelerator pedal travel is detected to be >3%, the mode switching process is entered.

[0143] During zero-speed holding, the system monitors operating parameters in real time and employs a tiered protection strategy to prevent motor damage. Simultaneously, it continuously monitors the driver's operational intentions to ensure safe and stable operation under all conditions. This prevents motor overheating and overcurrent damage caused by zero-speed stall, extending motor lifespan. Multiple fault protections prevent vehicle loss of control, meeting automotive-grade safety requirements. Continuous monitoring of driver operation ensures timely mode switching.

[0144] Step 6: Smoothly exit anti-slip mode and switch to normal drive.

[0145] When the driver presses the accelerator pedal, the linear torque transition strategy smoothly switches from zero-speed hold mode to normal drive mode, avoiding sudden torque changes that could cause jerking or rolling back, thus achieving a smooth start on an incline.

[0146] After the core controller detects that the accelerator pedal travel is greater than 3%, it calculates the driver's required torque and the corresponding q-axis current setpoint based on the pedal travel and the motor's external characteristics; it then transitions the q-axis current setpoint from the anti-rollover mode to the drive mode current setpoint using a 200ms linear gradient curve (e.g., ...). Figure 4 (As shown in the diagram) During the transition, the position loop remains active to ensure no vehicle slippage; after the transition is complete, the system completely exits the anti-slippage mode and enters normal driving mode. This achieves a smooth, shock-free transition without any jerking or slippage, completely simplifying hill start operations. The driver only needs to press the accelerator to start, without the need for handbrake or brake operation, significantly lowering the driving threshold.

[0147] Figure 4 In the diagram: the horizontal axis represents time (0-200ms), and the vertical axis represents the q-axis current setpoint, such as 6 before and 4 after zero speed (unit: A, positive values ​​indicate forward movement). The curve linearly transitions from the initial current value (I_hold, which may be negative, corresponding to braking torque) in anti-rollover mode to the target current value (I_drive, positive, corresponding to driving torque) in drive mode, with a constant slope. Parameter definitions:

[0148] I_hold: q-axis current when holding at zero speed (calculated by position closed-loop PI algorithm, used to balance the gravity of the ramp).

[0149] I_drive: q-axis current in drive mode (calculated based on accelerator pedal travel and motor external characteristics).

[0150] A 200ms linear gradient is used to avoid sudden current changes, ensuring a smooth torque transition and preventing vehicle jerking or slippage. The position loop remains active throughout the transition, ensuring vehicle position stability during the switchover.

[0151] The following is an application example of this system.

[0152] Application Example 1: Low-speed civilian electric four-wheeled vehicle

[0153] Basic parameters: The vehicle has a rated voltage of 48V, is equipped with a 3kW surface-mount permanent magnet synchronous motor, the motor has a built-in 1024-line incremental quadrature encoder, a wheel rolling radius of 0.25m, a reducer reduction ratio of 10:1, a rated passenger capacity of 4 people, a curb weight of 350kg, and a fully loaded gross weight of 650kg.

[0154] Test conditions: 15° standard slope, fully loaded with 4 people, brake pedal fully released, accelerator pedal not pressed, to test anti-roll-off performance, hovering stability, and starting smoothness.

[0155] Implementation process:

[0156] After the vehicle is powered on and completes initialization and parameter calibration, it drives to the middle of a 15° slope. The driver completely releases the brake pedal and does not press the accelerator pedal.

[0157] The system enters the standby state. After three consecutive sampling cycles, it detects that the vehicle displacement reaches 0.7mm, which is determined to be a tendency to roll backwards. Zero speed holding control is immediately triggered.

[0158] The position loop PI control outputs a q-axis current setpoint of 18A, and the FOC drive module injects the corresponding current into the motor, generating a braking torque of 45N·m to balance the gravitational downward component, allowing the vehicle to hover stably on the slope.

[0159] The hovering process lasted for 10 minutes, during which the motor winding temperature rose from 25°C to 38°C, without any overheating.

[0160] When the driver presses the accelerator pedal, the system completes the mode switch in a linear transition of 200ms, and the vehicle starts smoothly without jerking or rolling back.

[0161] In this way, the slope displacement can be controlled within 0.7mm, achieving true zero-speed hovering; there is no overheating or vibration during long-term hovering; the slope start operation is simplified to a single-pedal operation, completely avoiding the risk of rolling away, and adapting to the operating needs of elderly mobility scooter users.

[0162] Application Example 2: Electric Four-Wheeled Vehicle for Urban Logistics

[0163] Basic parameters: The vehicle has a rated voltage of 72V, is equipped with a 5kW surface-mount permanent magnet synchronous motor, the motor has a built-in 2048-line incremental quadrature encoder, a wheel rolling radius of 0.3m, a reducer reduction ratio of 12:1, a rated load of 1.5 tons, a curb weight of 800kg, and a fully loaded gross weight of 2300kg.

[0164] Test conditions: 20° underground parking garage ramp, fully loaded with 1.5 tons of cargo. Testing performance under heavy load conditions included anti-slip performance, hovering stability, and adaptability to frequent starts and stops. Details are as follows:

[0165] When the vehicle is fully loaded and reaches the middle of a 20° slope, the driver releases the brake pedal, the system enters a ready state, and triggers zero-speed holding control after detecting a displacement of 0.5mm.

[0166] The position loop adaptively outputs a q-axis current setpoint of 25A, generating 80N·m of braking torque to balance the heavy-load slip component and keep the vehicle hovering stably.

[0167] The ramp started and stopped 20 times in a row, with a hovering time of 30 seconds each time. The slope displacement was controlled within 0.6 mm, the motor temperature rose by no more than 12℃, and there was no overheating or control failure.

[0168] During the frequent starts and stops of the underground parking garage ramp, the system did not trigger erroneously once, and the start was smooth and without any impact.

[0169] Therefore, it was found that micron-level slope control can still be achieved under heavy load conditions, adapting to large load changes, and starting and stopping without failure for a long time and at high frequency. It fully meets the high-frequency slope use requirements of urban logistics vehicles, replaces traditional mechanical handbrakes and electronic handbrakes, and reduces vehicle operation and maintenance costs.

[0170] The above embodiments can be implemented, in whole or in part, by software, hardware (such as circuits), firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, all or part of the processes or functions described in the embodiments of the present invention are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more sets of available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium. A semiconductor medium can be a solid-state drive.

[0171] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0172] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0173] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0174] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0175] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the devices, apparatuses, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0176] In the several embodiments provided by this invention, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0177] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0178] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0179] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0180] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A slope zero-speed holding and anti-slippage system for an electric four-wheeled vehicle, characterized in that, It includes a signal acquisition layer, a core control layer, a drive execution layer, and a safety monitoring layer, among which: The signal acquisition layer is used to acquire the travel signals of the brake pedal and accelerator pedal, as well as the rotor pulse signal of the motor's built-in incremental quadrature encoder, to provide the system with driver operation intentions and vehicle displacement data. The core control layer includes a built-in trigger logic judgment unit, a zero-speed position closed-loop control algorithm unit, and a field-oriented control (FOC) algorithm unit. The trigger logic judgment unit is used to complete the trigger and exit logic judgment of the anti-slip control based on the input signal. The zero-speed position closed-loop control algorithm unit is used to adaptively calculate the motor q-axis current setpoint to balance the gravity component of the slope through position closed-loop PI control. The field-oriented control (FOC) algorithm unit is used to realize the decoupled control of the motor dq-axis current and output the SVPWM drive signal. The drive execution layer is used to convert the drive signal of the core control layer into a three-phase drive current of the motor, and output a zero-speed braking torque opposite to the direction of the slope through the permanent magnet synchronous motor to achieve zero-speed hovering of the vehicle. The security monitoring layer is used to monitor system operating parameters in real time and execute graded fault protection strategies. The system does not rely on additional slope sensors, acceleration sensors, or mechanical parking lock mechanisms throughout the entire process. It achieves zero-speed maintenance and anti-slippage on the slope solely through closed-loop position control based on encoder displacement feedback.

2. The system according to claim 1, characterized in that, The signal acquisition layer includes a pedal status acquisition module and an encoder signal acquisition module. The pedal status acquisition module uses an automotive-grade Hall linear displacement sensor to acquire pedal travel signals at a sampling frequency of 1kHz. The encoder signal acquisition module acquires pulse signals from the motor quadrature encoder at a sampling frequency of 10kHz, and converts the rotor angular displacement into the actual linear displacement of the vehicle through a displacement calculation formula. The displacement detection accuracy can reach 0.1mm.

3. The system according to claim 1, characterized in that, The zero-speed position closed-loop control algorithm unit incorporates a vehicle displacement calculation formula: In the formula: This represents the actual linear displacement of the vehicle. The radius of the wheel's rolling motion. The amount of pulse change captured by the encoder. The reduction ratio of the motor reducer. This refers to the number of pulses per encoder revolution. Simultaneously, it incorporates the position closed-loop PI control algorithm formula: In the formula: The given value for the q-axis current of the motor. This is the position ring proportionality coefficient. These are the integral coefficients of the position loop. For positional error, , The target position zero point is locked when maintaining zero speed. This represents the actual displacement of the vehicle. This is the time integral operation for the position error.

4. The system according to claim 1, characterized in that, The magnetic field orientation control (FOC) algorithm unit adopts... Maximum torque / current ratio control strategy, with built-in electromagnetic torque formula: In the formula: For the electromagnetic torque of the motor, This represents the number of pole pairs of the motor. For rotor permanent magnet flux linkage, This refers to the actual q-axis current of the motor; the d-axis current is set by... This achieves complete decoupling of excitation current and torque current, maximizing torque output efficiency during zero-speed stall.

5. The system according to claim 1, characterized in that, The drive execution layer includes a three-phase full-bridge FOC drive module and a permanent magnet synchronous motor execution unit. The three-phase full-bridge FOC drive module adopts a three-phase full-bridge inverter topology, executes SVPWM modulation at a control frequency of 20kHz, and collects three-phase current in real time to feed it back to the core controller to form a current closed loop. The permanent magnet synchronous motor execution unit outputs a constant zero-speed stall torque based on the interaction between the stator magnetic field and the rotor permanent magnet, balancing the gravity downhill component.

6. The system according to claim 1, characterized in that, The safety monitoring layer incorporates a three-level protection strategy: early warning level derating protection, fault level limiting protection, and danger level emergency shutdown protection. It collects motor phase current, winding temperature, DC bus voltage, and encoder signal status in real time at a sampling frequency of 1kHz. In the event of a fault, it triggers the corresponding protection action and sends a fault code via the CAN bus.

7. A method for maintaining zero speed and preventing slippage on an electric four-wheeled vehicle on a slope, characterized in that, The system implementation based on any one of claims 1-6 includes the following steps: Step 1: Power on the system for initialization and parameter calibration, complete the self-test of all modules and load the vehicle's inherent parameters and control parameters; Step 2: Real-time acquisition of pedal status and determination of preparatory mode. Based on the pedal travel signal, the driver's operating intention is determined, and the anti-rollover preparatory state is entered when the conditions are met. Step 3: Encoder signal calculation and anticipation of slope tendency identification. The actual displacement of the vehicle is calculated by the encoder pulse signal, and the zero speed holding control is triggered after identifying the slope tendency. Step 4: Zero-speed position closed-loop control and FOC drive execution. The q-axis current setpoint is adaptively calculated through position closed-loop PI control, and the braking torque of the drive motor is output based on FOC vector control to achieve zero-speed hovering of the vehicle. Step 5: Hovering state safety monitoring and status maintenance, real-time monitoring of system operating parameters, execution of graded protection strategies, and continuous monitoring of driver's operating intentions; Step 6: Smoothly exit anti-slip mode and switch to normal drive. After detecting that the accelerator pedal is effectively pressed, the mode is smoothly switched through linear torque transition, and normal drive is restored.

8. The method according to claim 7, characterized in that, In step 3, the criteria for determining the slope tendency are: if the absolute value of the vehicle displacement is detected to be >0.8mm for three consecutive sampling cycles, and the displacement continues to increase, and the speed direction is opposite to the vehicle's forward direction, the current position is locked as the target zero point when zero-speed holding control is triggered.

9. The method according to claim 7, characterized in that, In step 4, during the zero-speed holding control process, the position loop control frequency is 10kHz and the current loop control frequency is 20kHz. The q-axis current is continuously adjusted through closed-loop control to keep the actual displacement of the vehicle at the target zero point, thus adapting to 0-30° slopes and different load conditions.

10. The method according to claim 7, characterized in that, In step 6, the mode switching process uses a 200ms linear gradient curve to smoothly transition the q-axis current setpoint of the anti-slip mode to the current setpoint of the drive mode. During the transition, the position loop closed-loop control remains effective to ensure that there is no slippage or swerving during the switching process.

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