AGV distributed rudder wheel drive and electromagnetic brake closed-loop safety control method and system

Abstract

The application discloses an AGV distributed rudder wheel driving and electromagnetic brake closed-loop safety control method and system, relates to the field of general control or regulation systems, and comprises the following steps: receiving target motion parameters issued by an upper master control unit, setting a regulation target as a suction target current, and controlling a constant current driving circuit to output electric energy to an electromagnetic brake coil; collecting loop current of the electromagnetic brake coil, performing proportional integral differential regulation, and updating output duty cycle of the constant current driving circuit; after the loop current reaches a preset suction threshold value, generating motor driving duty cycle and outputting the same to a motor driving inverter, driving a rudder wheel motor node to enter a running working condition, and lowering the regulation target of the constant current driving circuit to a preset maintenance current; and when the loop current deviates from a preset maintenance threshold interval, blocking the motor driving duty cycle of the motor driving inverter, and cutting off the output of the constant current driving circuit, so as to perform emergency braking. The application can improve the safety of the coordinated control of the rudder wheel and the brake.

Description

Technical Field

[0001] This application relates to the general field of control or regulation systems, and more particularly to a method and system for closed-loop safety control of AGV distributed steering wheel drive and electromagnetic brake. Background Technology

[0002] With the rapid development of industrial automation and intelligent logistics, Automated Guided Vehicles (AGVs), as core equipment for realizing automated material handling, have been applied in many scenarios such as warehousing, manufacturing, and ports. Among various drive solutions for AGVs, the distributed steering wheel drive system has become the mainstream choice for improving AGV mobility and space utilization due to its advantages such as compact structure, flexible control, and ability to achieve zero-radius steering.

[0003] In related technologies, the control of the AGV steering wheel drive and electromagnetic brake employs an open-loop sequential logic control method. Specifically, when the host controller issues a motion command, the control system first sends an unlock command to the electromagnetic brake drive module, energizing its drive coil to release the mechanical brake. To ensure the brake is fully released, the system typically inserts a fixed time delay after this. After this delay, the system assumes the brake is reliably released and then sends a pulse-width modulation (PWM) signal to the steering wheel motor drive module, causing the motor to rotate and thus enabling the AGV's movement. When braking is required, the reverse logic is executed: first, the motor drive signal is stopped, and then the power supply to the electromagnetic brake is cut off, causing it to lock.

[0004] However, as an electromechanical component, the response time of an electromagnetic brake's engagement and release is affected by various factors such as fluctuations in operating voltage, changes in coil temperature, and wear and aging of mechanical parts, and is not a constant value. If the delay time is not set sufficiently, the motor may be forced to start before the brake pads are fully disengaged, which may cause safety hazards such as mechanical impact on the steering wheel, motor burnout, AGV deviation, or even overturning. Summary of the Invention

[0005] This application provides a method and system for closed-loop safety control of distributed steering wheel drive and electromagnetic brake in AGV, which is used to improve the safety of coordinated control of steering wheel and brake.

[0006] In a first aspect, this application provides a closed-loop safety control method for distributed steering wheel drive and electromagnetic brake in AGVs, applied to a dedicated controller for distributed steering wheels. The method includes: receiving target motion parameters from a host control unit; setting the adjustment target of the constant current drive circuit to a preset target current; and controlling the constant current drive circuit to output electrical energy to the electromagnetic brake coil; acquiring the loop current of the electromagnetic brake coil; performing proportional-integral-derivative (PID) adjustment on the loop current in conjunction with the target current to update the output duty cycle of the constant current drive circuit; after the loop current reaches a preset threshold, generating a motor drive duty cycle in conjunction with the target motion parameters and outputting it to the motor drive inverter to drive the steering wheel motor node into operating condition; during operating condition, lowering the adjustment target of the constant current drive circuit to a preset sustaining current; and when the loop current deviates from the preset sustaining threshold range, blocking the motor drive duty cycle of the motor drive inverter and cutting off the output of the constant current drive circuit to perform emergency braking.

[0007] In the above embodiments, the control system monitors the brake circuit current in real time and executes closed-loop control to ensure that the motor restarts only after the electromagnetic brake is fully released, thereby improving the safety of the coordinated control of drive and brake.

[0008] In conjunction with some embodiments of the first aspect, in some embodiments, the step of blocking the motor drive duty cycle of the motor drive inverter and cutting off the output of the constant current drive circuit to perform emergency braking when the loop current deviates from the preset maintenance threshold range specifically includes: acquiring preset open circuit fault thresholds and short circuit fault thresholds; controlling the underlying hardware logic gate circuit to output low-level trigger data when the loop current is less than the open circuit fault threshold or greater than the short circuit fault threshold; inputting the low-level trigger data to the enable pin of the pulse width modulation output channel to block the motor drive duty cycle; and cutting off the power supply circuit of the electromagnetic brake coil to complete the emergency braking.

[0009] In the above embodiments, the control system achieves rapid fault response through the underlying hardware logic gate circuit, directly blocking the motor drive and cutting off the brake power supply, thus ensuring the reliability and real-time performance of the emergency braking process.

[0010] In some embodiments of the first aspect, after cutting off the power supply circuit of the electromagnetic brake coil to complete the emergency braking step, the method further includes: generating a corresponding equipment fault code based on the deviation characteristics of the circuit current, and encapsulating the equipment fault code as bus alarm data and sending it to the upper master control unit; receiving node isolation data issued by the upper master control unit, and cutting off the bus communication response permission of the controller of the current distributed steering wheel based on the node isolation data; obtaining redundant motion control data reallocated by the upper master control unit based on the equipment fault code; and driving the remaining distributed steering wheels other than the current distributed steering wheel to perform compensating motion based on the redundant motion control data.

[0011] In the above embodiments, after a single steering wheel node fails, the control system achieves fault-tolerant control of the AGV system through a series of actions such as fault reporting, node isolation, and motion compensation, thereby improving the overall operational reliability.

[0012] In some embodiments of the first aspect, the step of acquiring the loop current of the electromagnetic brake coil and performing proportional-integral-derivative (PID) adjustment on the loop current in conjunction with the target pull-in current to update the output duty cycle of the constant current drive circuit specifically includes: acquiring the loop current, coil temperature, and supply voltage of the electromagnetic brake coil; determining the corresponding proportional coefficient, integral time constant, and derivative time constant in conjunction with the coil temperature and supply voltage; calculating the deviation between the loop current and the target pull-in current; performing PID adjustment in conjunction with the proportional coefficient, integral time constant, derivative time constant, and deviation value to output the duty cycle adjustment amount; and updating the output duty cycle of the constant current drive circuit in conjunction with the duty cycle adjustment amount to eliminate the influence of temperature and voltage fluctuations on the accuracy of brake current control.

[0013] In the above embodiments, the control system dynamically adjusts the PID control parameters according to the coil temperature and power supply voltage, thereby eliminating the influence of working environment fluctuations on the accuracy of brake current control and ensuring the stability of the brake release process.

[0014] In some embodiments of the first aspect, the steps of receiving the target motion parameters sent by the upper-level main control unit, setting the adjustment target of the constant current drive circuit to a preset target pull-in current, and controlling the constant current drive circuit to output electrical energy to the electromagnetic brake coil specifically include: receiving the target motion parameters sent by the upper-level main control unit, determining the initial starting torque in the target motion parameters; generating a zero-speed holding duty cycle based on the initial starting torque, and outputting the zero-speed holding duty cycle to the motor drive inverter to drive the steering wheel motor node to output the current torque; generating a hovering ready confirmation parameter when the current torque reaches the preset hovering holding torque; setting the adjustment target of the constant current drive circuit to the preset target pull-in current based on the hovering ready confirmation parameter, and controlling the constant current drive circuit to output electrical energy to the electromagnetic brake coil.

[0015] In the above embodiments, the control system applies a hovering holding torque in advance before the brake is released, which prevents the AGV from accidentally slipping due to the gravity component in working conditions such as slopes, thus improving the safety of the start-up process.

[0016] In some embodiments of the first aspect, after generating the motor drive duty cycle by combining the target motion parameters and outputting it to the motor drive inverter to drive the steering wheel motor node into the operating condition, the method further includes: obtaining the local actual speed and local actual steering angle of the current distributed steering wheel dedicated controller; receiving the coordinated speed and coordinated steering angle broadcast by other distributed steering wheel dedicated controllers through the industrial bus network; calculating the difference between the local actual speed and the coordinated speed to obtain the speed synchronization deviation, and calculating the difference between the local actual steering angle and the coordinated steering angle to obtain the steering synchronization deviation; substituting the speed synchronization deviation and the steering synchronization deviation into a preset fuzzy control algorithm model to perform correction, obtaining the compensated speed and the compensated steering angle; and correcting the motor drive duty cycle by combining the compensated speed and the compensated steering angle.

[0017] In the above embodiments, the control system uses a fuzzy control algorithm to correct the speed and steering synchronization deviations between multiple steering wheels in real time, thereby achieving precise coordination of the motion posture of each steering wheel and ensuring the driving stability of the AGV body.

[0018] In some embodiments of the first aspect, the step of correcting the motor drive duty cycle by combining the compensated speed and the compensated steering angle specifically includes: obtaining the current load weight and determining the corresponding load adjustment coefficient based on the current load weight; collecting the three-phase stator current and rotor position of the steering wheel motor node; performing field-oriented control calculations based on the load adjustment coefficient, three-phase stator current, rotor position, compensated speed, and compensated steering angle to obtain the target voltage vector; and performing space vector pulse width modulation operations based on the target voltage vector to correct the motor drive duty cycle.

[0019] In the above embodiments, the control system performs field-oriented control by combining multiple parameters such as load and synchronization compensation, thereby achieving precise adjustment of the output torque of the steering wheel motor and improving the dynamic response performance and motion control accuracy of the AGV.

[0020] In a second aspect, embodiments of this application provide a control system comprising: one or more processors and a memory; the memory being coupled to the one or more processors, the memory being used to store computer program code, the computer program code including computer instructions, the one or more processors invoking the computer instructions to cause the control system to perform the method described in the first aspect and any possible implementation thereof.

[0021] Thirdly, embodiments of this application provide a computer-readable storage medium including instructions that, when executed on a control system, cause the control system to perform the method described in the first aspect and any possible implementation thereof.

[0022] Fourthly, embodiments of this application provide a computer program product containing instructions that, when the computer program product is run on a control system, cause the control system to perform the method described in the first aspect and any possible implementation thereof.

[0023] Understandably, the control system provided in the second aspect, the computer storage medium provided in the third aspect, and the computer program product provided in the fourth aspect are all used to execute the methods provided in the embodiments of this application. Therefore, the beneficial effects they can achieve can be referred to the beneficial effects in the corresponding methods, and will not be repeated here.

[0024] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0025] 1. Because a closed-loop control method is adopted, which collects the loop current of the electromagnetic brake coil and drives the steering wheel motor only after the loop current reaches the preset engagement threshold, the actual release state of the electromagnetic brake can be confirmed in real time. This effectively solves the problem that the fixed delay time used in the prior art cannot cope with the changes in the brake response time, which may lead to the motor starting with the brake. Thus, precise and safe coordinated control between the steering wheel drive and the electromagnetic brake is realized.

[0026] 2. Because it adopts an emergency braking method that directly blocks the motor drive duty cycle and cuts off the brake power supply through the underlying hardware logic gate circuit when an abnormal loop current is detected, it can bypass the software execution delay and realize fault protection at hardware speed. This effectively solves the problem of slow fault response at the software level in the existing technology, which may not be able to prevent the fault from spreading or avoid danger in time, and thus realizes a highly reliable and real-time emergency braking function.

[0027] 3. Because it adopts a design that drives the steering wheel motor to output a preset hovering holding torque before controlling the release of the electromagnetic brake, the motor torque can seamlessly take over the vehicle's holding force at the moment the brake pads separate from the brake disc. This effectively solves the problem in the existing technology where there is a time difference between brake release and motor start-up in scenarios such as slopes, which may cause the vehicle to roll away unexpectedly or shake. This achieves a smooth and safe start-up transition. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a topology of the control system in an embodiment of this application;

[0029] Figure 2 This is a flowchart illustrating the AGV distributed steering wheel drive and electromagnetic brake closed-loop safety control method in an embodiment of this application.

[0030] Figure 3This is another flowchart illustrating the AGV distributed steering wheel drive and electromagnetic brake closed-loop safety control method in the embodiments of this application;

[0031] Figure 4 This is a schematic diagram of the physical device structure of a control system in an embodiment of this application. Detailed Implementation

[0032] The terminology used in the following embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in the specification of this application, the singular expressions “a,” “an,” “the,” “the,” and “this” are intended to include the plural expressions as well, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this application refers to any or all possible combinations including one or more of the listed items.

[0033] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature, and in the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0034] The innovation of the AGV distributed steering wheel drive and electromagnetic brake closed-loop safety control method and system provided in this application lies in its ability to accurately determine the actual release state of the brake by real-time acquisition of the loop current of the electromagnetic brake coil and execution of closed-loop control. This ensures that the steering wheel motor is only started after the brake is confirmed to be fully released, avoiding the risk of motor starting with the brake engaged, which is common in existing technologies using fixed time delays. Furthermore, this application utilizes low-level hardware logic gate circuits to achieve rapid detection of abnormal brake loop current and emergency braking response, significantly improving the real-time performance and reliability of fault protection. In addition, this application designs a series of enhancement technologies for complex operating conditions such as ramp starts, multi-steering wheel synchronization, environmental parameter changes, and single-node failures, including pre-torque holding, fuzzy collaborative control, adaptive PID adjustment, and redundancy compensation, resulting in a highly safe, precise, and robust control system.

[0035] To make the present application clearer, the embodiments of the present application will be described in further detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present application can be combined with each other. In the following description, many specific details, such as specific system architectures, interfaces, and technologies, are provided to facilitate understanding of the embodiments of the present application; however, those skilled in the art should understand that the present application can be practiced without these specific details. In other cases, detailed descriptions of well-known devices, circuits, and methods have been omitted to avoid unnecessarily obscuring the present application. Furthermore, the accompanying drawings only show the parts relevant to the present application and not all of them; unless otherwise specified, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions.

[0036] The embodiments of this application firstly... Figure 1 This section explains the topology and hardware connections of the entire control system, enabling those skilled in the art to understand the collaboration between modules and the data flow. Then, through... Figure 2 and Figure 3 This paper elaborates on the execution flow and judgment logic of the control method under different operating conditions, and provides specific algorithm implementations and parameter configuration details for key technical aspects of the method. Finally, it demonstrates the application of this method. Figure 4 The hardware structure of the control system that carries this method is described to fully demonstrate the technical solution of this application.

[0037] Please see Figure 1 This is a schematic diagram of the topology of the control system in an embodiment of this application. Figure 1 The diagram illustrates the connection relationships and data flow between the host control unit, the industrial bus network, the distributed steering wheel dedicated controller, and the steering wheel motor nodes.

[0038] The host control unit, located at the top level of the system, is responsible for the global path planning and motion control scheduling of the AGV. It sends target motion parameters, including target linear velocity, target angular velocity, and initial starting torque, to each distributed steering wheel controller via the industrial bus network. Simultaneously, it receives status data and fault alarm data reported by each distributed steering wheel controller. The industrial bus network connects the host control unit and each distributed steering wheel controller, using CAN bus or EtherCAT bus protocols, and supports multi-master broadcasting and point-to-point communication.

[0039] Figure 1 The dashed box on the left shows the internal structure of a single distributed steering wheel controller, including a constant current drive circuit, a current acquisition module, a proportional-integral-derivative adjustment module, hardware logic gate circuits, and a motor drive inverter.

[0040] The constant current drive circuit receives the duty cycle signal from the proportional-integral-derivative (PID) control module and outputs pulse-width modulated (PWM) power to the electromagnetic brake coil. When energized, the electromagnetic brake coil generates an electromagnetic attraction that overcomes the spring force, separating the brake pads from the brake disc and releasing the brakes.

[0041] The current acquisition module measures the loop current of the electromagnetic brake coil in real time and outputs an analog voltage signal characterizing the loop current. This analog voltage signal is divided into two paths: the first path is converted into a digital signal by an analog-to-digital converter and then sent to the proportional-integral-derivative (PID) adjustment module; the second path is directly sent to the comparator of the hardware logic gate circuit. The PID adjustment module calculates the duty cycle adjustment based on the deviation between the loop current and the target pull-in current or holding current and outputs it to the constant current drive circuit.

[0042] The hardware logic gate circuit internally includes a first comparator and a second comparator. The non-inverting input of the first comparator receives the loop current acquisition signal, and the inverting input is connected to a reference voltage corresponding to the open-circuit fault threshold. When the loop current is less than the open-circuit fault threshold, the first comparator outputs a low level; otherwise, it outputs a high level. The non-inverting input of the second comparator is connected to a reference voltage corresponding to the short-circuit fault threshold, and the inverting input receives the loop current acquisition signal. When the loop current is greater than the short-circuit fault threshold, the second comparator outputs a low level; otherwise, it outputs a high level. The outputs of the first and second comparators are processed by an AND gate. When either comparator outputs a low level, the AND gate output is also low, thus generating low-level trigger data. This data is input to the pulse width modulation output channel enable pin of the motor drive inverter, blocking the motor drive duty cycle. Simultaneously, after the controller detects the low-level trigger data output by the hardware logic gate circuit, it controls the power supply switch of the constant current drive circuit to disconnect via the digital output pin, cutting off the power supply circuit to the electromagnetic brake coil.

[0043] The motor drive inverter receives the motor drive duty cycle output from the distributed steering wheel controller. When the enable pin is high, it converts the DC bus voltage into a three-phase AC voltage, which is then applied to the stator windings of the steering wheel motor node via a pulse-width modulation output channel. The steering wheel motor node includes a drive motor and a steering motor. The drive motor controls the linear velocity of the steering wheel, and the steering motor controls the steering angle. The rotor position of the steering wheel motor node is acquired by an encoder, and the three-phase stator current is acquired by a current sensor. The acquired data is fed back to the distributed steering wheel controller for field-oriented control calculations.

[0044] Figure 1 The dashed box on the right shows a simplified structure of other distributed steering wheel controllers, each with the same hardware components and control logic. Each distributed steering wheel controller broadcasts its local actual speed and local actual steering angle via an industrial bus network, while simultaneously receiving coordinated speed and coordinated steering angles broadcast by other controllers.

[0045] When a distributed steering wheel controller detects an abnormal circuit current in the electromagnetic brake coil, it generates a fault code, encapsulates it as bus alarm data, and sends it to the host control unit. The host control unit identifies the faulty steering wheel node based on the fault code, issues node isolation data to sever the node's bus communication response permission, recalculates the redundant motion control data for the remaining healthy steering wheels, and sends it to the other distributed steering wheel controllers via the industrial bus network, driving the remaining distributed steering wheels to perform compensating motions.

[0046] Based on the above system topology, the control method of this application is executed in the form of a periodic task in the distributed steering wheel dedicated controller. Its core logic can be divided into four continuous state transition processes: brake release stage, motor start stage, operation maintenance stage and fault protection stage.

[0047] During the brake release phase, the controller uses closed-loop regulation to ensure the electromagnetic brake coil current reaches the target current, guaranteeing reliable separation of the brake pads and brake disc. During the motor start-up phase, the controller outputs the motor drive signal only after determining that the brake has been fully released based on loop current feedback, avoiding starting with the brakes on. During the operation maintenance phase, the controller lowers the brake current to a maintenance level and continuously monitors its stability, while simultaneously implementing multi-steering wheel coordinated control to ensure motion accuracy. During the fault protection phase, if an abnormal deviation of the brake loop current from the normal range is detected, the controller can execute emergency braking and report fault information through both hardware and software mechanisms. The following section combines... Figure 2 Describe the basic execution flow of this method in detail.

[0048] The method provided in this embodiment is described in detail below. Please refer to [link / reference]. Figure 2 This is a flowchart illustrating the AGV distributed steering wheel drive and electromagnetic brake closed-loop safety control method in an embodiment of this application.

[0049] S201: Receive the target motion parameters sent by the upper main control unit, set the adjustment target of the constant current drive circuit to the preset target current for attracting, and control the constant current drive circuit to output electrical energy to the electromagnetic brake coil.

[0050] Among them, the target motion parameters refer to the set of data issued by the upper-level main control unit to define the desired motion state of the AGV, such as target linear velocity, angular velocity, or pose; the constant current drive circuit refers to a power electronic circuit that can output a stable current to power the electromagnetic brake coil; the preset target pull-in current refers to a specific current value that is sufficient to make the electromagnetic brake completely overcome its internal spring force and reliably release, and this value is usually much greater than the current required to maintain the brake release state; the electromagnetic brake coil refers to the inductive element inside the electromagnetic brake, which generates a magnetic field when energized to drive the brake mechanical structure to move.

[0051] Specifically, when the AGV is stationary and receives a start or move command, the distributed steering wheel controller first parses the target motion parameters from the upper-level main control unit via the industrial bus network. To prepare for driving the steering wheel motor, the control system must first release the normally closed electromagnetic brake. The control system sets the internal current control loop's setpoint, i.e., the adjustment target, to a preset target current for engagement. Subsequently, the control system enables the constant current drive circuit, which begins outputting pulse-width modulation (PWM) power to the electromagnetic brake coil, causing the coil current to rise rapidly to generate sufficient electromagnetic force to open the brake.

[0052] It should be noted that the constant current drive circuit adopts a single-transistor asynchronous buck converter topology. Its main power circuit consists of an N-channel power MOSFET as the high-side switch, a freewheeling diode, and the inductance of the electromagnetic brake coil itself, along with a series sampling resistor. The controller's PWM output pin is connected to the gate of the power MOSFET via a gate driver. When the PWM is high, the MOSFET is turned on, and the DC bus voltage is applied to the series circuit between the coil and the sampling resistor, causing the circuit current to rise. When the PWM is low, the MOSFET is turned off, and the current in the coil continues to flow through the freewheeling diode, causing the circuit current to decrease. Under the condition that the PWM switching frequency is much higher than the reciprocal of the coil's electrical time constant (typical PWM frequencies are 20kHz to 50kHz, while the time constant L / R of the electromagnetic brake coil is typically tens of milliseconds), the current ripple in the coil is very small. The average value of the circuit current is approximately equal to the bus voltage multiplied by the duty cycle and then divided by the total circuit resistance. ,in Where D is the DC bus voltage, and D is the PWM duty cycle. The DC resistance of the coil, This is the resistance value of the sampling resistor. The output of the PID controller is the adjustment amount of the duty cycle D. By increasing or decreasing D, the actual loop current tracks the set target current value. Sampling resistor The typical value is 0.1Ω to 0.5Ω, and the voltage across it is amplified by a differential operational amplifier before being fed into an analog-to-digital converter and a hardware comparator. A fast recovery Schottky diode is used for the freewheeling diode to reduce switching losses, and the on-resistance of the power MOSFET is selected to be in the 10mΩ range to reduce conduction losses. The entire circuit operates at a voltage range of 24V to 48V DC, covering the common battery power levels of AGVs.

[0053] The gate driver employs a bootstrap high-side drive scheme, specifically: when the PWM output is low, the lower-arm MOSFET is turned on, charging the bootstrap capacitor through the bootstrap diode to the bus voltage minus the diode voltage drop. When the PWM flips to high, the lower arm is turned off. At this time, the negative potential of the bootstrap capacitor is raised to near the bus voltage, while the positive potential is raised to approximately twice the bus voltage. This potential difference is sufficient to drive the gate of the high-side N-channel MOSFET, enabling it to reliably turn on. The bootstrap capacitor value must meet the following requirements. Design principles, among which N is the total gate charge of the MOSFET, and N is the ratio of the high-level duration during the PWM cycle to the gate driver power consumption time constant (typically 10 to 20). This is the allowable bootstrap voltage drop (set to 5% to 10% of the bus voltage). Taking a 24V bus system as an example, if the gate charge is selected... A MOSFET with a voltage rating of 50nC and N = 15. If a 1.2V input is selected, the bootstrap capacitor should be no less than 625nF. In practice, a 1μF / 50V surface-mount ceramic capacitor is chosen. The freewheeling diode should be a Schottky type, with a reverse recovery time of less than 50ns and a forward voltage drop of less than 0.5V to reduce conduction losses. The rated current should be selected with a margin of 1.5 times the coil pull-in current. The inductance of the entire Buck converter is provided by the coil itself and does not require an external connection. The sampling resistor... Arranged between the coil and ground to form a low-side current sampling topology, the power dissipation of this resistor is as follows: The calculation involves I, representing the maximum value of the target pull-in current. In actual selection, the power rating should have at least a 2x margin to handle transient overloads and ambient temperature rise. When the battery voltage drops below 18V, the duty cycle adjustment range of the constant current drive circuit is insufficient to maintain the target pull-in current. At this point, the controller detects duty cycle saturation (D≥95% for more than 100ms), generates a power supply undervoltage fault code, and performs emergency braking. When the coil temperature exceeds 85℃, the controller forcibly reduces the holding current to 70% of the nominal value and limits the duration of the target pull-in current to no more than 5 seconds to prevent coil overheating and damage.

[0054] S202. Collect the loop current of the electromagnetic brake coil, and combine it with the target current to perform proportional-integral-derivative adjustment on the loop current in order to update the output duty cycle of the constant current drive circuit.

[0055] Among them, the loop current refers to the actual current value flowing through the electromagnetic brake coil; the output duty cycle refers to the proportion of the high-level time of the PWM signal in one cycle, which determines the average voltage applied to the coil, and thus controls the magnitude of the loop current.

[0056] Specifically, after power is supplied to the electromagnetic brake coil in step S201, the control system enters a high-speed real-time control loop. In this loop, the control system measures the instantaneous current flowing through the electromagnetic brake coil using a built-in current acquisition module (e.g., a sampling resistor and amplifier circuit connected in series in the loop). Then, the control system compares this acquired actual loop current value with the target pull-in current value set in step S201, calculating the deviation between the two. This deviation is then input into the PID control algorithm. The PID controller calculates an adjustment amount based on the current deviation (P), the cumulative historical deviation (I), and the rate of change of the deviation (D). This adjustment amount is used to correct the PWM output duty cycle of the constant current drive circuit, thereby precisely controlling the coil current to approach and stabilize at the target pull-in current value.

[0057] S203. After the circuit current reaches the preset pull-in threshold, the motor drive duty cycle is generated by combining the target motion parameters and output to the motor drive inverter to drive the steering wheel motor node into the operating condition.

[0058] Among them, the motor drive duty cycle refers to the PWM signal used to control the on and off of the power switching tubes in the motor drive inverter. Its waveform and phase determine the voltage and frequency of the motor stator winding; the motor drive inverter is a power electronic device that converts DC power into three-phase AC power; the steering wheel motor node refers to the execution unit that includes the drive motor and related sensors; the operating condition refers to the state in which the steering wheel motor starts to rotate according to the command, driving the AGV to move.

[0059] Specifically, while executing the closed-loop current control in step S202, the control system continuously compares the collected loop current with a preset pull-in threshold. If the control system detects that the loop current has reached or exceeded the threshold and remains stable for a short confirmation time (e.g., a few milliseconds), the control system determines that the electromagnetic brake has been fully released and the mechanical brake has been released. At this point, the control system considers the conditions for starting the motor to be met. The control system then calculates the initial voltage vector required to drive the motor based on the target motion parameters (such as target speed and acceleration) sent by the upper-level main control unit, through its internal motion controllers (such as speed loop and current loop), and converts it into a specific motor drive duty cycle through algorithms such as space vector pulse width modulation (SVPWM), and outputs it to the motor drive inverter, thereby driving the steering wheel motor to start rotating and putting the AGV into operating condition.

[0060] The determination methods for the preset engagement threshold and preset holding threshold include: during the factory calibration phase, the control system applies a step-incremental current to the electromagnetic brake coil while simultaneously monitoring the output signal of the mechanical clearance sensor or force sensor between the brake disc and brake pads. The current value corresponding to when the mechanical clearance reaches the design value or the clamping force drops to zero is recorded as the complete release current. Considering the temperature coefficient of the coil resistance and fluctuations in the supply voltage, the pull-in threshold is set to... The current is increased to 90% to 95% to ensure reliable brake release under various operating conditions; then, while maintaining the brake release state, the supply current is gradually reduced until the critical current at which the brake pads begin to contact the brake disc is detected. The lower limit of the threshold range is set to 120% to 150% to provide sufficient safety margin, with the upper limit set at [value missing]. The current is set at 70% to 80% to balance energy consumption and reliability; the open circuit fault threshold is set at 30% to 50% of the preset nominal holding current, and the short circuit fault threshold is set at 150% to 200% of the target current. The specific values ​​are determined experimentally based on the electrical parameters and mechanical characteristics of the electromagnetic brake model and stored in the controller's non-volatile memory.

[0061] In the firmware of the distributed steering wheel controller, the loop current pull-in threshold is determined using a sliding window filter combined with continuous counting confirmation. The controller acquires the loop current value via an analog-to-digital converter at a fixed sampling period (typically 50μs to 100μs, synchronized with the PWM switching frequency of the constant current drive circuit). Each acquired raw value is first processed by a sliding average filter with a depth of 8 to 16 points to eliminate PWM switching ripple and high-frequency noise introduced by the analog front end. The filtered current value is then sent to the threshold comparison stage. This comparison stage maintains an unsigned integer continuous pass counter, initially set to zero. In each sampling period, if the filtered current value is greater than or equal to the preset pull-in threshold, the counter is incremented; otherwise, the counter is forcibly reset and restarted. When the accumulated value of the counter reaches the preset number of confirmation periods (this number of periods equals the confirmation time divided by the sampling period; for example, if the confirmation time is set to 3ms and the sampling period is 100μs, the number of confirmation periods is 30), the controller determines that the electromagnetic brake has been reliably released, sets the internal brake release confirmation flag, and allows the subsequent motor start-up process to execute. If, at any sampling point during the counting process, the filtered current value drops below the pull-in threshold (e.g., due to a temporary drop in current caused by a sudden decrease in supply voltage), the counter is reset and begins accumulating again. This means the confirmation time is reset, and the system must wait for the current to stabilize continuously above the threshold before passing the judgment. This design ensures that false release judgments will not occur in real-world environments where the current signal has transient disturbances. At the same time, the 3ms-level confirmation time introduces almost no additional startup delay compared to the tens of milliseconds of mechanical action time of the electromagnetic brake.

[0062] S204. Under operating conditions, the adjustment target of the constant current drive circuit is lowered to the preset holding current.

[0063] The preset holding current refers to a current value that is much smaller than the target pull-in current, but still sufficient to keep the electromagnetic brake in the released state. Lowering the adjustment target is to reduce system energy consumption and the heat generated by the electromagnetic brake coil while ensuring functionality.

[0064] Specifically, once the steering wheel motor node successfully enters the operating condition in step S203, it means that the electromagnetic brake has completed its opening action. At this point, maintaining the separation of the brake pads and brake disc only requires overcoming the static pressure of the spring; it no longer needs to overcome the initial friction and inertia, thus reducing the required electromagnetic force. To save energy and reduce Joule heating of the coil due to prolonged high current flow, extending its service life, the control system switches the closed-loop regulation target of the constant current drive circuit from a higher preset pull-in target current to a lower preset holding current. The PID control loop automatically adjusts the PWM duty cycle based on this new, lower target value, causing the loop current to smoothly decrease from the pull-in current and stabilize at the holding current level.

[0065] Subsequently, the control system enters a long-term operation and maintenance phase. During this phase, the constant current drive circuit continuously performs closed-loop control with the goal of maintaining the current, ensuring that the brake is always in a reliable release state. Meanwhile, the steering wheel motor continuously outputs driving torque according to the upper-level instructions and the cooperative algorithm. Throughout the entire operation and maintenance phase, the control system continuously monitors the loop current of the electromagnetic brake coil in real time. If the current is found to deviate abnormally from the preset maintenance threshold range, the emergency protection procedure is activated.

[0066] S205. When the circuit current deviates from the preset maintenance threshold range, the motor drive duty cycle of the motor drive inverter is blocked, and the output of the constant current drive circuit is cut off to perform emergency braking.

[0067] Among them, blocking the motor drive duty cycle means stopping the output of PWM signals to the motor drive inverter, or disabling its output through the enable pin, so that the motor enters a free coasting or braking state; cutting off the output of the constant current drive circuit means stopping the power supply to the electromagnetic brake coil, so that it loses power and locks up.

[0068] Specifically, during normal AGV operation, the control system continuously monitors the loop current of the electromagnetic brake coil and determines whether it falls within the preset maintenance threshold range. If the control system detects an abnormal deviation in the loop current, such as excessively low current (which may indicate poor wiring contact or a broken wire) or excessively high current (which may indicate an internal short circuit in the coil), this indicates that the conditions for reliably releasing the brake are no longer met, posing a risk of the brake unexpectedly locking up, or that the brake drive circuit itself has malfunctioned. To ensure safety, the control system executes an emergency braking procedure. This procedure includes two parallel key actions: first, immediately blocking all control signals to the motor drive inverter, causing the steering wheel motor to stop outputting drive torque; second, almost simultaneously, completely cutting off the power supply to the electromagnetic brake coil from the constant current drive circuit. After the coil loses power, its internal spring mechanism activates, causing the brake pads to press against the brake disc, achieving mechanical locking braking.

[0069] The aforementioned basic control process has achieved closed-loop safety coordination between braking and driving. However, in practical engineering applications, AGVs often face more complex operating challenges, such as how to prevent slippage when starting on a slope, how to eliminate motion asynchrony between steering wheels in a multi-steering wheel distributed drive system, how to maintain stable control accuracy when load and environmental parameters change, and how to achieve system-level fault-tolerant operation after a single steering wheel node failure. To address these advanced requirements, this application introduces enhancement technologies such as a pre-torque holding mechanism, multi-steering wheel fuzzy synchronization control, adaptive PID parameter adjustment, and redundant motion compensation on the basis of the basic process.

[0070] These enhancement technologies are organically integrated with the basic processes, together forming a complete and highly robust and safe AGV distributed steering wheel drive and electromagnetic braking closed-loop safety control scheme. The following section combines... Figure 3 A detailed description of the complete control flow incorporating these enhancement technologies is provided. Please refer to [link / reference]. Figure 3 This is another flowchart illustrating the AGV distributed steering wheel drive and electromagnetic brake closed-loop safety control method in the embodiments of this application.

[0071] S301: Receive the target motion parameters sent by the host control unit and determine the initial starting torque in the target motion parameters.

[0072] The initial starting torque refers to a specific torque command calculated and issued by the upper-level main control unit based on the current load status of the AGV and its environment (such as whether it is on a slope). Its purpose is to allow the motor to generate a force sufficient to balance the gravitational component or other external disturbance torque before the brake is released.

[0073] Specifically, when the control system receives motion commands from the host control unit, it first parses the various parameters in the data frame. Unlike the basic process, the control system here pays particular attention to a parameter called initial starting torque. This parameter is not constant but dynamically determined by the host control unit. For example, if the AGV's attitude sensor detects that the vehicle is tilted, the host control unit calculates the component of gravity along the slope direction based on the tilt angle and the AGV's total mass, and then deduces the required starting torque to prevent the vehicle from rolling back. The control system uses this torque value as the direct target for the next step of motor control.

[0074] S302, Combine the initial starting torque to generate a zero-speed holding duty cycle, and output the zero-speed holding duty cycle to the motor drive inverter to drive the steering wheel motor node to output the current torque.

[0075] Zero-speed holding duty cycle refers to a specific set of PWM duty cycles that, when applied to a motor, enable the motor to output a precise, non-zero torque even when the speed is zero.

[0076] Specifically, after determining the target initial starting torque, but before releasing the electromagnetic brake, the control system enters the pre-torque application phase. The control system utilizes its internal motor control algorithm (typically Field-Oriented Control, FOC) with the target torque value as input. The FOC algorithm calculates the required stator current vector (i.e., the Iq component) based on the current rotor position (provided by the encoder) and the target torque. Then, through inverse Park transform and the SVPWM module, it ultimately generates a set of three-phase PWM duty cycle signals that produce the target torque but do not cause the motor to rotate (i.e., the target speed is zero), i.e., zero-speed holding duty cycle. This set of duty cycle signals is output to the motor drive inverter, driving the motor to generate a static torque that matches the target initial starting torque.

[0077] It is important to note that although the controller has output the corresponding duty cycle signal, the motor needs to undergo a brief dynamic response process from zero torque to the target torque value. The duration of this process depends on the motor's electromagnetic time constant and the response speed of the current loop. During this period, if the control system releases the electromagnetic brake, there may be a time window where the motor torque has not been fully established before the brake is released, thus still posing a risk of rollback on inclines. Therefore, after outputting the zero-speed holding duty cycle, the control system cannot directly enter the brake release step to avoid the risk of rollback on inclines. Instead, it must first confirm through real-time monitoring that the motor output torque has truly reached the preset hovering holding torque level. Only after this confirmation condition is met can the brake release process be safely initiated.

[0078] S303. When the current torque reaches the preset hovering holding torque, generate hovering ready confirmation parameters.

[0079] Specifically, after outputting the zero-speed holding duty cycle in step S302, the actual output torque of the motor does not instantly reach the target value, but rather undergoes a brief dynamic process. The control system indirectly estimates the current output torque by monitoring the feedback value of the motor current loop. The control system continuously compares this estimated current torque value with a preset hovering holding torque threshold. If the current torque reaches or exceeds the threshold and can be stably maintained for a very short confirmation time (to filter out noise and transient fluctuations), the control system determines that the motor has successfully taken over the holding task previously handled by the brake. At this time, the control system internally generates a hovering ready confirmation parameter. In step S303, while monitoring the establishment of the motor pre-torque, the control system starts an overtime protection timer, with the overtime duration set to 500ms to 1000ms. If the hovering ready confirmation parameter is not generated within the overtime period, the control system determines that the brake release is abnormal or the motor torque establishment has failed, terminates the startup process, and reports a fault.

[0080] The value of the preset hovering holding torque is determined based on the static balance analysis of the AGV under the maximum design slope. Specifically, it is calculated by multiplying the total mass of the AGV fully loaded by the gravitational acceleration, then by the sine of the maximum design slope angle, and then dividing by the number of drive wheels and the transmission ratio. The result is then converted to the equivalent torque value on the output shaft of a single steering wheel motor. On this basis, a safety factor of 1.2-1.5 is multiplied to cover the changes in rolling resistance between the tires and the ground and the fluctuations in the efficiency of the transmission system.

[0081] For example, for an AGV with a full load capacity of 1000kg, a maximum design slope of 5 degrees, four steering wheels, and a transmission ratio of 10, the required hovering torque for a single wheel motor is calculated as (1000*9.8*sin5°) / (4*10)*1.3≈27.7N·m. This value is stored in the controller's parameter table after being determined during the system debugging phase.

[0082] Regarding torque arrival determination, the controller indirectly estimates the current output torque using the linear relationship between the electromagnetic torque and q-axis current of the permanent magnet synchronous motor (Te=1.5*p*ψf*Iq, where p is the number of pole pairs, ψf is the flux linkage of the permanent magnet, and Iq is the q-axis current). In each current loop control cycle (typically 50μs), the controller transforms the acquired three-phase stator current into Id and Iq components in the dq coordinate system using Clark and Park transformations. Substituting Iq into the aforementioned torque equation yields the estimated value of the current electromagnetic torque. When this estimated value remains above 95% of the preset hovering holding torque for several consecutive control cycles (typically 20 to 50 cycles, i.e., 1 to 2.5 milliseconds), the controller determines that the torque has been stably established and generates hovering readiness confirmation parameters. The motor parameters p and ψf are known motor nameplate parameters, loaded from the parameter table during controller initialization.

[0083] To ensure the reliability of the judgment, after the torque estimation value enters the 95% threshold range, the controller also needs to perform auxiliary verification of the rotor position stability. Specifically, this includes: the controller recording the rotor electrical angle fed back by the encoder in each control cycle. Calculate the angular change between two adjacent cycles. When within N consecutive control cycles The absolute values ​​of all values ​​are less than the preset static determination threshold. Only when this condition is met is the rotor considered to be truly stationary and hovering, rather than about to start or in a state of slight oscillation. Stationary determination threshold. The value needs to take into account both the encoder resolution and the inherent backlash of the mechanical system. For an incremental encoder with 2500 lines, its electrical angular resolution is 360° / (2500*4*number of pole pairs). Taking a 4-pole pair motor as an example, it is approximately 0.009° per count. The value is typically set to 3 to 5 times the encoder resolution, i.e., 0.03° to 0.05°, to filter out the influence of encoder quantization noise. The setting of the number of consecutive decision cycles N is related to the current loop control cycle. When the current loop cycle is 50μs, N values ​​of 20 to 50 correspond to an observation window of 1 to 2.5ms. This time window needs to be long enough to ensure that the torque has been fully established and transient oscillations have been eliminated, but short enough to avoid significantly prolonging the start-up response time. The controller generates hover readiness confirmation parameters only when both the q-axis current-estimated torque and the rotor being stationary are simultaneously satisfied, thus logically forming a dual confirmation mechanism for torque amplitude and position stability.

[0084] S304. Combined with the hovering readiness confirmation parameter, the adjustment target of the constant current drive circuit is set to the preset pull-in target current, and the constant current drive circuit is controlled to output electrical energy to the electromagnetic brake coil.

[0085] Specifically, this step is the connection point between the pre-torque control and brake release processes. The logic state machine inside the control system is waiting for the hovering ready confirmation parameter generated in step S303. When this parameter becomes valid (e.g., the flag is set), the control system confirms that the motor is ready and the mechanical brake can be safely released. Upon receiving this internal trigger signal, the control system performs the exact same action as in step S201: setting the adjustment target of the constant current drive circuit to the preset target pull-in current and turning on the circuit to supply power to the electromagnetic brake coil, initiating the brake release process. Since the motor has already output sufficient holding torque at this time, the AGV will not move due to gravity or external forces at the moment the brake pads separate from the brake disc.

[0086] In some embodiments, extreme scenarios may occur, such as motor failure, preventing the establishment of sufficient pre-torque. To address this, the control system implements a timeout monitoring mechanism. Upon entering the pre-torque application phase (step S302), the control system simultaneously starts a timeout timer (e.g., 500ms). If the hovering readiness confirmation parameter is not generated before the timer expires, the control system determines that pre-torque establishment has failed. In this case, the control system not only avoids the brake release step but also terminates the entire startup process, resets the motor drive duty cycle to zero, and reports a startup failure - pre-torque timeout fault code to the upper-level main control unit, awaiting further instructions or manual intervention. This prevents the danger of releasing the brake when the motor is unable to maintain its position.

[0087] S305: Collect the loop current of the electromagnetic brake coil, and combine it with the target pull-in current to perform proportional-integral-derivative adjustment on the loop current in order to update the output duty cycle of the constant current drive circuit.

[0088] Refer to step S202, which will not be repeated here.

[0089] The aforementioned closed-loop current control ensures that the electromagnetic brake can quickly and reliably reach the release state during the engagement phase. When the brake circuit current reaches the preset engagement threshold, the control system determines that the brake has been fully opened and then proceeds to step S306 to start the steering wheel motor and enter the operating condition.

[0090] To improve the stability of braking control under different operating environments, in some embodiments, the control system performs adaptive PID parameter adjustment that takes into account environmental changes. Specifically, the control system: collects the loop current, coil temperature, and supply voltage of the electromagnetic brake coil; determines the corresponding proportional gain, integral time constant, and derivative time constant based on the coil temperature and supply voltage; calculates the deviation between the loop current and the target pull-in current; performs proportional-integral-derivative (PID) adjustment based on the proportional gain, integral time constant, derivative time constant, and deviation value, and outputs the duty cycle adjustment; and updates the output duty cycle of the constant current drive circuit based on the duty cycle adjustment to eliminate the impact of temperature and voltage fluctuations on the accuracy of brake current control.

[0091] Among them, coil temperature refers to the real-time temperature of the electromagnetic brake coil, which affects the coil's resistance value; supply voltage refers to the input DC voltage of the constant current drive circuit, and its fluctuations will affect the output capability under the same duty cycle; proportional coefficient (Kp), integral time constant (Ti), and derivative time constant (Td) are three key parameters of the PID controller, which determine the controller's response characteristics.

[0092] Specifically, the control system recognizes that the resistance of the electromagnetic brake coil increases with temperature (positive temperature coefficient effect), and fluctuations in the supply voltage also affect the dynamic response of the current control. To address these changes, the control system acquires real-time coil temperature and supply voltage via temperature sensors and voltage sampling circuits before executing PID regulation. The control system internally stores a two-dimensional look-up table (LUT), whose index is the quantization range of temperature and voltage. The table stores the optimal PID parameter set (Kp, Ti, Td) for different operating conditions. Based on the acquired temperature and voltage values, the control system obtains the most suitable PID parameters by looking up the table and possibly performing interpolation. Then, it uses this dynamically adjusted set of parameters to execute the PID calculation, thereby ensuring that the closed-loop control system of the braking current maintains stable, fast, and overshoot-free performance regardless of changes in the external environment.

[0093] In some embodiments, this parameter adaptive adjustment can be achieved in several ways: Optionally, the gain scheduling method, i.e., the lookup table method mentioned above, can be used. This is the most commonly used and effective method, and the parameter table can be obtained through offline simulation and experimental tuning. Optionally, Model Reference Adaptive Control (MRAC) can be used. The control system has an ideal braking current response reference model built in. The system adjusts the PID parameters online by comparing the difference between the actual current response and the output of the reference model, so that the behavior of the actual system approximates the ideal model infinitely. This method is more complex, but more adaptable. It is understood that other intelligent algorithms such as fuzzy control and neural networks can also be used to achieve online PID parameter self-tuning, which is not limited here.

[0094] S306. After the circuit current reaches the preset pull-in threshold, the motor drive duty cycle is generated by combining the target motion parameters and output to the motor drive inverter to drive the steering wheel motor node into the operating condition.

[0095] Refer to step S203, which will not be repeated here.

[0096] To ensure the smoothness and accuracy of the trajectory of multi-wheeled AGVs, in some embodiments, the control system performs multi-steering wheel synchronous cooperative control. This involves: acquiring the local actual speed and local actual steering angle of the current distributed steering wheel controller; receiving the cooperative speed and cooperative steering angle broadcast by other distributed steering wheel controllers via the industrial bus network; calculating the difference between the local actual speed and the cooperative speed to obtain the speed synchronization deviation, and calculating the difference between the local actual steering angle and the cooperative steering angle to obtain the steering synchronization deviation; substituting the speed synchronization deviation and steering synchronization deviation into a preset fuzzy control algorithm model for correction to obtain the compensated speed and compensated steering angle; and combining the compensated speed and compensated steering angle to correct the motor drive duty cycle.

[0097] Among them, the local actual speed / steering angle refers to the motion state of its own steering wheel as measured by the current controller through sensors such as encoders; the cooperative speed / steering angle refers to the motion state received from other steering wheel controllers as a synchronization reference; the synchronization deviation is the difference in the actual motion state between each steering wheel; and the compensation speed / steering angle is the adjustment amount output by the fuzzy controller to correct the motion of the local steering wheel.

[0098] Specifically, during AGV operation, each distributed steering wheel controller not only independently controls its own motor but also periodically broadcasts its actual speed and steering angle to all other controllers via the industrial bus. Simultaneously, it receives broadcast data from all other controllers. The controller compares the received motion states of other steering wheels (or the reference states specified by the host computer) with its own local state, calculating the synchronization deviations in speed and steering. These deviation values ​​are input into a preset fuzzy controller. The fuzzy controller internally defines a set of language rules. Through steps such as fuzzification, rule reasoning, and defuzzification, the fuzzy controller outputs a precise compensated speed and compensated steering angle. This compensation is then superimposed on the original target speed and angle of the steering wheel to correct its motor drive duty cycle, thereby actively eliminating motion deviations with other steering wheels and achieving high synchronization of all steering wheels in the entire vehicle.

[0099] The construction of the preset fuzzy control algorithm model specifically includes: first, defining the input variable as the speed synchronization deviation. and steering synchronization deviation The output variable is the compensation speed. and compensated steering angle ; Fuzzyen the input variables, The universe of discourse is divided into the range [-500, +500] rpm, and five fuzzy subsets are defined: negative large (NB), negative small (NS), zero (ZE), positive small (PS), and positive large (PB). Quantization is performed using triangular or trapezoidal membership functions; similarly, The universe of discourse is set to [-30°, +30°] and the same fuzzy subset partitioning is used; the output variable and The universes of discourse are set to [-200, +200] rpm and [-15°, +15°], respectively, and five fuzzy subsets are defined accordingly;

[0100] A fuzzy rule base was established, containing 25 rules (5*5). The complete fuzzy rules are shown in the table below:

[0101] The format of each cell in the table is as follows: Fuzzy set Fuzzy sets, for example, PB / PB in the first row and first column represent when For NB and When it is NB, The output is PB. The output is PB. The physical meaning followed by the rule design is: when the local steering wheel's speed or steering angle is significantly greater than the cooperative reference (positive deviation), negative compensation is applied to slow it down or make it turn back; when the deviation is negative, positive compensation is applied to accelerate it or make it turn forward; when the deviation is close to zero, the compensation amount is also close to zero to avoid over-adjustment. Rules on the diagonal ( and The case where the same sign and similar amplitude correspond to the case where the steering wheel deviates synchronously in both the speed and steering dimensions, in which case both outputs are subject to large compensation in the same direction; while the case where the opposite diagonal rule corresponds to the case where the speed and steering deviations are in opposite directions, requiring compensation in opposite directions in both dimensions to achieve decoupling control.

[0102] The rule design follows the principles of error inverse compensation and proportional response; the Mamdani inference method is adopted, using the minimum method for fuzzy implication calculation and the maximum method for rule synthesis; defuzzification employs the centroid method (COG), with the calculation formula as follows: ,in The output membership function is synthesized; the entire fuzzy controller operates in a period of 1 to 5 ms, calculates the compensation amount based on the real-time collected synchronization deviation and superimposes it on the original motion command to realize continuous dynamic correction of the motion state of each steering wheel.

[0103] To achieve ultimate precise control of the steering wheel torque to cope with load changes and synchronization requirements, in some embodiments, the control system performs precise torque control based on load and synchronization compensation. That is, the control system will: obtain the current load weight and determine the corresponding load adjustment coefficient based on the current load weight; collect the three-phase stator current and rotor position of the steering wheel motor node; perform field-oriented control calculations based on the load adjustment coefficient, three-phase stator current, rotor position, compensation speed and compensation steering angle to obtain the target voltage vector; and perform space vector pulse width modulation operation based on the target voltage vector to correct the motor drive duty cycle.

[0104] Among them, the load capacity refers to the weight of the goods currently being transported by the AGV, which can be measured by sensors or provided by the host system; the target voltage vector is the output of the FOC calculation, representing the voltage space vector that needs to be applied to the motor stator in the next PWM cycle.

[0105] Specifically, this is a sophisticated, integrated control process. The control system first acquires the current load information of the AGV and determines a load adjustment coefficient accordingly. Simultaneously, it receives the compensated speed and compensated steering angle output from the fuzzy synchronous controller. This information, along with the rotor position from the encoder and the three-phase stator current from the current sensor, serves as the input to the FOC algorithm. Within the FOC calculation, the compensated speed / angle is superimposed on the original speed / position command to form the final motion target. The load adjustment coefficient is used to dynamically adjust the PI parameters of the current loop in the FOC or directly feedforward compensation of the torque command to address the impact of load changes on system inertia. After this series of comprehensive calculations, the FOC finally outputs a precise target voltage vector, which is then converted into the final motor drive duty cycle by the SVPWM module. This achieves high dynamic response and high precision torque control that takes into account load changes and multi-wheel synchronization requirements.

[0106] S307. Under operating conditions, the adjustment target of the constant current drive circuit is lowered to the preset holding current.

[0107] Refer to step S204, which will not be repeated here.

[0108] During normal operation of the AGV, the electromagnetic brake is in the energized release state and the circuit current is maintained at the preset holding current level. At this time, the steering wheel motor drives the entire AGV to run smoothly according to the instructions of the upper main control unit and the correction output of the multi-steering wheel cooperative algorithm.

[0109] However, because electromagnetic brake coils operate in environments of vibration and temperature fluctuations for extended periods, their circuits may experience open circuits or short circuits due to factors such as wire aging, loose connectors, or insulation damage between coil turns. If such faults occur, the brakes will lose controllability and may unexpectedly lock up or completely fail, posing a serious threat to the operational safety of the AGV. To respond immediately to faults, a rapid fault detection and emergency braking mechanism based on hardware logic gates is needed. This mechanism does not rely on software loop scanning and judgment but instead uses pure hardware comparators and logic gates to complete fault identification and protection action triggering on a nanosecond timescale, thereby minimizing fault response delays and maximizing the safety of personnel and equipment. The specific implementation steps of this fault protection mechanism are described below.

[0110] S308. Obtain the preset open circuit fault threshold and short circuit fault threshold.

[0111] The open circuit fault threshold is a low current value used to determine whether the brake coil circuit is open or has poor contact; the short circuit fault threshold is a high current value used to determine whether the coil has an inter-turn short circuit or whether the drive circuit has a fault shoot-through.

[0112] Specifically, before the control system initializes or enters operating mode, it loads a series of pre-configured parameters from its non-volatile memory (such as Flash or EEPROM), including open-circuit fault thresholds and short-circuit fault thresholds. These thresholds are set based on the electrical characteristics of the electromagnetic brake coil (such as the holding current range during normal operation) and the protection requirements of the drive circuit. For example, if the normal holding current is 0.5A, the open-circuit fault threshold might be set to 0.1A, while the short-circuit fault threshold might be set to 2.0A. After acquiring these thresholds, the control system configures them into the corresponding hardware comparators or software comparison logic as a benchmark for subsequent real-time fault diagnosis.

[0113] S309. When the loop current is less than the open circuit fault threshold or greater than the short circuit fault threshold, control the underlying hardware logic gate circuit to output low-level trigger data.

[0114] Among them, the underlying hardware logic gate circuits refer to fast logic judgment circuits composed of discrete hardware components such as comparators, AND gates, and OR gates, which operate independently of the main processor (CPU). Low-level trigger data refers to a voltage signal that changes from a high level to a low level, used to trigger subsequent hardware protection actions.

[0115] It should be noted that the specific implementation of the underlying hardware logic gate circuits includes: the analog voltage signal output by the current acquisition module. (This voltage is proportional to the loop current, and the conversion relationship is as follows) =I* *G, where (where G is the sampling resistor value and G is the operational amplifier gain) After filtering, the samples are fed into the non-inverting inputs of the first and second comparators, respectively; the inverting input of the first comparator is connected to the reference voltage corresponding to the open-circuit fault threshold. (Right now Figure 1 The open-circuit threshold voltage (Vref1) is generated from a reference voltage source (such as TL431) by a precision resistor divider network and set to a specific voltage value. This voltage value is designed based on converting the open-circuit fault threshold current to the equivalent voltage at the comparator input, using the following conversion formula: ,in The fault threshold current is used for open circuit faults; the second comparator is configured in reverse, and its inverting input receives... The signal, with its non-inverting input connected to a reference voltage corresponding to the short-circuit fault threshold. (Right now Figure 1 The circuit breaker threshold Vref2 in the reference voltage is designed similarly, and the conversion formula is as follows: ;when When the first comparator outputs a low level, When the second comparator outputs a low level, the outputs of the two comparators are processed by a dual-input AND gate (such as 74HC08). As long as either comparator outputs a low level, the output of the AND gate will also be low. This low-level signal is directly connected to the TZ (Trip-Zone) fault input pin of the motor drive PWM module (such as the ePWM module in TI's TMS320F28335), and the hardware automatically blocks all PWM outputs. The other path is connected to the external interrupt pin of the main control MCU (configured to be triggered by the falling edge), which triggers the interrupt service routine to perform software-level fault handling. The response delay of the entire hardware logic link is no more than 100 nanoseconds, which is much faster than the software scan cycle (usually 100μs to 1ms).

[0116] Specifically, during AGV operation, the analog voltage signal representing the brake circuit current output from the current acquisition module is not only sent to the ADC for digitization processing for software use, but also directly to the inputs of two hardware comparators. The reference voltage of the first comparator is set to the voltage corresponding to the open-circuit fault threshold, and the reference voltage of the second comparator is set to the voltage corresponding to the short-circuit fault threshold. When the circuit current is normal, the outputs of both comparators are high. If the circuit current is less than the open-circuit threshold or greater than the short-circuit threshold, the corresponding comparator output will flip to low. The outputs of these two comparators are combined through a logic gate (e.g., an AND gate, if the comparator's output is active low) to ultimately generate a single fault trigger signal. As long as either fault condition is met, this signal will change from high to low, i.e., output low-level trigger data.

[0117] It should be noted that the input signal of the hardware comparator comes from the output of the operational amplifier in the current acquisition module. The bandwidth of this operational amplifier is designed to be one-half to one-fifth of the PWM switching frequency (for example, when the PWM frequency is 20kHz, the op-amp bandwidth is set to 4kHz to 10kHz). A first-order low-pass filter is implemented by connecting a capacitor in parallel in the op-amp feedback loop. The cutoff frequency of this filter is selected to ensure that the residual amplitude of the PWM ripple current at the op-amp output is attenuated to less than one-tenth of the difference between the open-circuit fault threshold and the normal holding current, thereby ensuring that the PWM ripple will not reach the comparator's fault threshold region during normal operation. In addition, an RC debouncing network is connected in series between the comparator output and the logic gate input, with a time constant set to 1μs to 5μs. The function of this debouncing network is to filter out narrow pulse interference with a width smaller than the time constant, ensuring that only real fault signals with a duration exceeding the debouncing time constant can pass through the logic gate to reach the Trip-Zone pin of the PWM module. This 1 to 5 μs debouncing time is still one to two orders of magnitude faster than the 100 μs to 1 ms period of software response, without weakening the real-time advantage of hardware protection, while effectively preventing false triggering caused by EMI spikes or switching noise. The setting of the open circuit fault threshold and short circuit fault threshold also takes into account the above-mentioned signal swing characteristics after filtering: the open circuit threshold is set to 30% to 50% of the nominal value of the holding current (far lower than the downward amplitude of normal ripple), and the short circuit threshold is set to 150% to 200% of the target current (far higher than the peak value that normal overshoot may reach). Sufficient margin is left between both thresholds and the normal operating range.

[0118] The RC debouncing network may specifically include: a comparator output pin connected to a series resistor. Connect the input pin of the logic gate, and simultaneously connect a capacitor in parallel between the logic gate input pin and ground. Series resistor Its function is to limit the impact on the capacitor when the comparator output flips. The peak charging and discharging current is controlled to prevent damage to the comparator output stage due to transient overload, while also... Together, they form a low-pass filter to suppress high-frequency spike interference. Resistor value and capacitance value The selection must satisfy the time constant. The constraint is within the range of 1 to 5 μs, while ensuring that the voltage at the logic gate input can be reliably maintained within the effective logic level range in steady state. This is based on the CMOS logic gate input threshold voltage. =1.5V, comparator output high level Taking 3.3V as an example, when a fault occurs, the comparator output jumps from 3.3V to 0V, and the capacitor... pass Discharge, the voltage at the logic gate input follows an exponential law. Attenuation, when decay to The following logic gates only flip when the flip delay time is specified. Substituting the values ​​into the equations... ≈0.79τ. If the target debouncing time is set to 3μs, then the time constant τ should be approximately 3.8μs, which can be selected. (Actual time constant 3.8μs) or This combination (actual time constant 3.96μs) is suitable. 1 / 8W or 1 / 10W surface-mount resistors are sufficient; NPO or X7R dielectric surface-mount ceramic capacitors should be used to ensure temperature stability. Note... The resistance value should not be too large; otherwise, the voltage drop at the logic gate input may deviate from the effective level range due to leakage current in steady state. Not exceeding 10kΩ, corresponding to the minimum It takes approximately 100 pF to achieve a time constant of 1 μs.

[0119] In addition, the low-level trigger signal of the hardware logic gate circuit is divided into two parallel paths on the circuit board. The first path is directly physically connected to the Trip-Zone fault input pin of the ePWM module inside the MCU (this connection does not pass through any programmable logic and is a pure hardware copper foil trace). Within one PWM clock cycle after receiving a valid trigger signal (for a 150MHz DSP, one clock cycle is approximately 6.67 nanoseconds), the Trip-Zone module completes the forced pull-low action of all PWM output channels. At this time, the gate drive signals of all power switches of the motor drive inverter are removed, and the motor immediately stops receiving valid drive. The second path is connected to the external interrupt pin of the MCU and configured as falling edge trigger. The priority of this interrupt is set to the highest level of the system (corresponding to INT1.x of PIE interrupt group 1 in the TI C2000 series DSP). The interrupt response delay includes the interrupt recognition time (approximately 5 to 8 CPU clock cycles) and the interrupt vector jump time (approximately 8 clock cycles), totaling approximately 100 nanoseconds to enter the first instruction of the interrupt service routine. The first action of the interrupt service routine is to set the GPIO pin of the gate of the MOSFET controlling the constant current drive circuit to the off level (writing to the GPIO register takes one clock cycle), thereby cutting off the power supply circuit to the electromagnetic brake coil. The delay from the occurrence of the fault to the hardware blocking of the PWM does not exceed 100 nanoseconds, and the delay from the occurrence of the fault to the software cutting off of the brake power supply does not exceed 200 nanoseconds, with a time difference of approximately 100 nanoseconds. During this 100-nanosecond interval, although the brake coil is still energized, the motor will not output any abnormal torque because the motor drive has been blocked, and the current in the brake coil will not undergo any perceptible change in such a short time (the coil time constant is on the order of milliseconds), so there is no safety hazard. In addition, after cutting off the power supply, the interrupt service routine will also check the status register of the Trip-Zone module to confirm that the hardware blocking has taken effect. If it is found that it has not taken effect (extreme abnormal situation), it will directly write to the PWM output register in software to force it to be cleared as a redundancy protection.

[0120] S310: Input low-level trigger data to the enable pin of the pulse width modulation output channel to block the motor drive duty cycle.

[0121] The enable pin of the pulse width modulation output channel is a dedicated hardware control pin on the motor drive PWM module. When this pin is at a specific level (e.g., low level), it will force and unconditionally put all PWM output channels into a safe state (e.g., high impedance or low level), thereby stopping the motor drive.

[0122] Specifically, the low-level trigger data generated in step S309 is physically connected directly to the enable pin of the motor drive PWM module (which may be called TRIP, FAULT, ENA, or BREAK in different chips). This is a purely hardware-level connection, without any software processing by the CPU. When a fault occurs, the moment the low-level trigger data reaches this pin, the internal logic of the PWM module reacts, bypassing all currently executing software instructions, and directly shuts down all PWM signal outputs to the motor drive inverter at a nanosecond speed. This achieves hardware-level blocking of the motor drive, with a response speed far faster than software detecting an anomaly and then shutting down the PWM by writing to registers.

[0123] In some embodiments, after the motor drive is blocked, the motor may continue to rotate due to inertia, generating a high back electromotive force in the permanent magnet synchronous motor, which may endanger the inverter. To address this, the control system configures the PWM module to perform dynamic braking during blocking, rather than simply a high-impedance state. The PWM module can be configured to, upon receiving a fault trigger signal, not turn off all switches (high-impedance state), but simultaneously turn on all switches in the lower arm (or all switches in the upper arm) of the inverter. This short-circuits the motor stator windings, and the rotating motor acts like a generator, generating a large braking current in the short-circuited windings, forming a strong electromagnetic braking force that rapidly decelerates and stops the motor.

[0124] S311. Disconnect the power supply circuit of the electromagnetic brake coil to complete emergency braking.

[0125] The power supply circuit refers to the complete current path from the constant current drive circuit to the electromagnetic brake coil. Cutting off this circuit means reducing the current to zero, thereby triggering the mechanical locking of the normally closed brake.

[0126] Specifically, while the motor drive is quickly locked down by hardware in step S310, the control system software also responds. The low-level trigger data generated in step S309, besides being sent to the PWM enable pin, is typically also connected to an interrupt input pin of the CPU. This hardware fault signal triggers a high-priority interrupt. In the interrupt service routine, the first action executed by the CPU is to control a digital output (GPIO) pin to operate an external switching element (such as a power MOSFET or relay) to physically disconnect the power supply circuit to the electromagnetic brake coil. The motor drive is locked down, and the brakes lose power and lock; these two actions together constitute a complete emergency braking system.

[0127] In some embodiments, the power supply cutoff for this step can be achieved in several ways: Optionally, a P-channel MOSFET can be connected in series at the power input of the constant current drive circuit as a main switch. Its gate is controlled by a GPIO pin. During normal operation, the GPIO output is low, turning on the MOSFET; during emergency braking, the interrupt service routine sets the GPIO to high, turning off the MOSFET and cutting off the power supply to the entire brake drive circuit. Optionally, a normally open relay can be connected in series in the brake coil circuit. During normal operation, a GPIO output from the controller is high, driving the relay coil to close its contacts; during emergency braking, the GPIO output is low, de-energizing the relay coil, opening the contacts, and disconnecting the circuit. The relay provides better electrical isolation. It is understood that other types of solid-state or mechanical switches can also be used to cut off the power supply circuit, and this is not limited here.

[0128] When a single distributed steering wheel node triggers emergency braking due to a brake circuit failure, the node has already completed two core protective actions locally: motor drive blocking and brake mechanical lock-up. This prevents the uncontrolled movement of the faulty steering wheel from directly threatening the overall safety of the AGV. However, at this point, the overall movement capability of the AGV is affected by the failure of one steering wheel. If the host control unit and other normal steering wheel nodes are unaware of this fault and continue to issue commands according to the original multi-steering wheel coordinated control strategy, it will cause the AGV's movement trajectory to deviate significantly from the expected trajectory and may even lead to secondary accidents such as overturning.

[0129] Therefore, simple local node protection is insufficient; a comprehensive system-level fault management mechanism is also needed to ensure that fault information is reported to the upper-level master control unit in a timely and accurate manner. The master control unit then coordinates with other healthy nodes to perform redundancy compensation actions or guides the AGV to a safe stop. Simultaneously, to prevent faulty nodes from sending erroneous motion status data to the bus due to internal anomalies, thus interfering with the coordinated control of other nodes, communication isolation of the faulty nodes is also required. The specific implementation steps of this system-level fault-tolerant control process are described in detail below.

[0130] After emergency braking, in order to achieve system-level fault management and fault-tolerant operation, in some embodiments, the control system will execute a fault reporting and redundancy control process. That is, the control system will: generate a corresponding equipment fault code based on the deviation characteristics of the loop current, and encapsulate the equipment fault code as bus alarm data and send it to the upper master control unit; receive node isolation data issued by the upper master control unit, and cut off the bus communication response permission of the controller of the current distributed steering wheel based on the node isolation data; obtain redundant motion control data reallocated by the upper master control unit based on the equipment fault code; and drive the other distributed steering wheels other than the current distributed steering wheel to perform compensating motion based on the redundant motion control data.

[0131] Among them, the equipment fault code is a code used to uniquely identify a specific fault type. For example, 0x01 indicates a broken brake coil wire, and 0x02 indicates a short circuit. Node isolation data is a command issued by the host control unit to instruct a specific node to stop responding to bus messages. Redundant motion control data is the motion parameters replanned by the host control unit for the remaining normal steering wheels after a steering wheel fails. Compensation motion refers to the remaining steering wheels adjusting their respective linear speeds and steering angles to make up for the driving force and steering force lost by the failed steering wheel, so as to maintain the stability of the overall motion trajectory of the AGV.

[0132] Specifically, when a distributed steering wheel controller performs emergency braking due to abnormal brake circuit current, it generates a corresponding equipment fault code based on the deviation characteristics of the circuit current. These deviation characteristics refer to the direction and magnitude of the circuit current exceeding a preset maintenance threshold range. Specifically, this includes the deviation characteristics corresponding to a circuit current below the open circuit fault threshold and the deviation characteristics corresponding to a circuit current above the short circuit fault threshold. The controller generates different fault codes accordingly (e.g., 0x01 for an open circuit fault and 0x02 for a short circuit fault). Subsequently, the controller packages its node ID and this fault code into a high-priority alarm message and broadcasts it to the upper-level master control unit via the industrial bus network. Upon receiving the alarm, the upper-level master control unit marks the steering wheel node as faulty and sends it a node isolation command, preventing it from responding to regular motion control commands and avoiding its abnormal behavior from interfering with the system. Next, the motion planning layer of the upper-level master control unit, based on the AGV's redundant drive model, deducts the contribution of the faulty steering wheel and recalculates a set of motion parameters (redundant motion control data) for the remaining healthy steering wheels, and then distributes these new parameters. Upon receiving new instructions, the other steering wheel controllers will adjust their own movements to work together to complete the compensating motion, in order to maintain the normal operation of the AGV or guide it to a safe stop as much as possible.

[0133] The redistribution of redundant motion control data is achieved based on the AGV's dynamic model and constraint optimization algorithm. First, the AGV's overall vehicle dynamic equations are established. In the vehicle coordinate system, the AGV's motion state is determined by the linear velocity of the vehicle's centerline. lateral velocity and angular velocity The three degrees of freedom describe the force and torque exerted by the i-th steering wheel on the vehicle body by the driving force of that steering wheel. Steering angle and the position vector of the steering wheel relative to the center of the vehicle body This is a joint decision. When all N steering wheels are functioning normally, the vehicle's dynamics equations can be expressed as: , Where M is the total vehicle mass. Let be the moment of inertia about the vertical axis of the vehicle body. Steering angle The corresponding rotation matrix, and These are the linear acceleration and angular acceleration vectors, respectively. When the j-th steering wheel fails, the driving force of that steering wheel... Forced to zero and steering angle The angle is locked at the instant of the failure, at which point the j-th term in the summation term on the right side of the above equation becomes invalid. To ensure that the remaining N-1 healthy steering wheels can still achieve the desired vehicle motion state, a constrained optimization problem needs to be solved: [The problem requires] satisfying the driving forces of each steering wheel... Not exceeding its maximum output capacity Steering angle The rate of change does not exceed the maximum angular velocity of the steering motor. Under the premise of kinematic coupling constraints between each steering wheel, find a new set of driving force distribution { } and steering angle allocation { The goal is to minimize the deviation between the actual and desired motion states of the vehicle. This optimization problem is solved online using a quadratic programming solver. The objective function is set as the weighted L2 norm of the difference between the desired and actual resultant forces. The constraints include: , | And the coupling inequality constraint between steering angle and driving force derived from the tire slip angle limitation. The host control unit solves this optimization problem in each control cycle (typically 10ms to 50ms), and obtains the optimal solution { , This refers to redundant motion control data, which is transmitted to each healthy steering wheel node via the industrial bus. Taking a four-steering wheel AGV as an example, if the left front steering wheel fails, the right front, left rear, and right rear steering wheels need to increase their respective driving forces and fine-tune their steering angles to compensate for the missing thrust and torque components of the left front steering wheel. The specific compensation allocation depends on the position of each steering wheel and the current steering angle, and the optimization algorithm automatically calculates the optimal allocation scheme.

[0134] In addition, for a four-steering wheel AGV, when a single steering wheel fails, the remaining three steering wheels can still achieve omnidirectional motion control; when two steering wheels fail, if the failed steering wheel is located diagonally, the remaining two steering wheels can achieve limited straight-line and steering movements; if the failed steering wheels are located on the same side, the AGV will only execute the safety stop procedure and will not attempt to continue moving.

[0135] In this embodiment, a closed-loop control method based on electromagnetic brake coil loop current feedback is employed, enabling precise determination of the brake release state. Furthermore, a fast fault response mechanism based on underlying hardware logic gate circuits is designed, achieving high real-time emergency braking. Additionally, the introduction of a motor pre-torque holding function before brake release prevents rollback on inclines. This method effectively solves the problems of motor starting with brakes, slow software fault response, and unsafe starting on inclines caused by fixed delays in existing technologies, thereby achieving high-safety, high-reliability, and high-precision coordinated control between AGV drive and braking.

[0136] The above embodiments elaborate on the AGV distributed steering wheel drive and electromagnetic brake closed-loop safety control scheme of this application from the aspects of method flow and algorithm logic. In order to enable those skilled in the art to understand the implementation mode and implementation mechanism of this scheme on the actual hardware platform, the following is combined with Figure 4 The control system in the embodiments of this application is described from the perspective of hardware processing. It should be noted that... Figure 4 The control system shown can be Figure 1 The internal processing architecture of a single distributed steering wheel controller can be a higher-level master control unit, or a distributed processing system combining both. Regardless of the deployment method, the core function of the control system is to implement the steps described in the above process flow by having the processor execute the computer program stored in memory.

[0137] Please see Figure 4 This is a schematic diagram of the physical device structure of a control system in an embodiment of this application. Figure 4 As shown, the control system includes a CPU 401, which can perform various appropriate actions and processes according to a program stored in ROM 402 or a program loaded into RAM 403 from storage section 408, such as executing the methods described in the above embodiments. RAM 403 also stores various programs and data required for system operation. The CPU 401, ROM 402, and RAM 403 are interconnected via bus 404. I / O interface 405 is also connected to bus 404.

[0138] The following components are connected to I / O interface 405: input section 406 including audio input devices, push-button switches, etc.; output section 407 including a liquid crystal display (LCD) and audio output devices, indicator lights, etc.; storage section 408 including a hard disk, etc.; and communication section 409 including a network interface card such as a LAN (Local Area Network) card, modem, etc. Communication section 409 performs communication processing via a network such as the Internet. Drive 410 is also connected to I / O interface 405 as needed. Removable media 411, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., are installed on drive 410 as needed so that computer programs read from them can be installed into storage section 408 as needed.

[0139] Specifically, according to embodiments of this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of this application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program including a computer program for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication section 409, and / or installed from removable medium 411. When the computer program is executed by CPU 401, it performs the various functions defined in this application.

[0140] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. Each block in a flowchart or block diagram may represent a module, segment, or portion of code, which contains one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those shown in the drawings.

[0141] Specifically, the control system of this embodiment includes a processor and a memory. The memory stores a computer program. When the computer program is executed by the processor, it implements the AGV distributed steering wheel drive and electromagnetic brake closed-loop safety control method provided in the above embodiment.

[0142] In another aspect, this application also provides a computer-readable storage medium, which may be included in the control system described in the above embodiments; or it may exist independently and not assembled into the control system. The storage medium carries one or more computer programs, which, when executed by a processor of the control system, cause the control system to implement the AGV distributed steering wheel drive and electromagnetic brake closed-loop safety control method provided in the above embodiments.

[0143] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0144] As used in the above embodiments, depending on the context, the term "when..." can be interpreted as meaning "if...", "after...", "in response to determining...", or "in response to detecting...". Similarly, depending on the context, the phrase "when determining..." or "if (the stated condition or event) is interpreted as meaning "if determining...", "in response to determining...", "when (the stated condition or event) is detected", or "in response to detecting (the stated condition or event)".

Claims

1. A closed-loop safety control method for distributed steering wheel drive and electromagnetic brake in AGVs, characterized in that, The method, applied to a distributed steering wheel controller, includes: Receive the target motion parameters sent by the upper master control unit, set the adjustment target of the constant current drive circuit to the preset target current for attracting, and control the constant current drive circuit to output electrical energy to the electromagnetic brake coil. The loop current of the electromagnetic brake coil is collected, and proportional-integral-derivative adjustment is performed on the loop current in combination with the target pull-in current to update the output duty cycle of the constant current drive circuit. After the circuit current reaches the preset pull-in threshold, the motor drive duty cycle is generated by combining the target motion parameters and output to the motor drive inverter to drive the steering wheel motor node into the operating condition. Under the aforementioned operating conditions, the adjustment target of the constant current drive circuit is lowered to the preset holding current; When the circuit current deviates from the preset maintenance threshold range, the motor drive duty cycle of the motor drive inverter is blocked, and the output of the constant current drive circuit is cut off to perform emergency braking, specifically including: Obtain the preset open circuit fault threshold and short circuit fault threshold; When the loop current is less than the open circuit fault threshold or greater than the short circuit fault threshold, the underlying hardware logic gate circuit is controlled to output low-level trigger data. The low-level trigger data is input to the enable pin of the pulse width modulation output channel to block the motor drive duty cycle; The power supply circuit of the electromagnetic brake coil is cut off to complete the emergency braking; Based on the deviation characteristics of the loop current, a corresponding equipment fault code is generated, and the equipment fault code is encapsulated as bus alarm data and sent to the upper master control unit; Receive node isolation data sent by the host control unit, and combine the node isolation data to cut off the bus communication response permission of the current distributed steering wheel controller; Obtain redundant motion control data reallocated by the host control unit in conjunction with the equipment fault code; Based on the redundant motion control data, the remaining distributed steering wheels other than the current distributed steering wheel are driven to perform compensating motion.

2. The method according to claim 1, characterized in that, The step of acquiring the loop current of the electromagnetic brake coil and performing proportional-integral-derivative (PID) adjustment on the loop current in conjunction with the target pull-in current to update the output duty cycle of the constant current drive circuit specifically includes: The loop current, coil temperature, and power supply voltage of the electromagnetic brake coil are collected. The corresponding proportional coefficient, integral time constant, and derivative time constant are determined by combining the coil temperature and the supply voltage; Calculate the deviation between the loop current and the target pull-in current; The proportional-integral-derivative (PID) adjustment operation is performed by combining the proportional coefficient, the integral time constant, the derivative time constant, and the deviation value, and the duty cycle adjustment amount is output. The output duty cycle of the constant current drive circuit is updated in conjunction with the duty cycle adjustment to eliminate the influence of temperature and voltage fluctuations on the accuracy of brake current control.

3. The method according to claim 1, characterized in that, The steps of receiving the target motion parameters sent by the upper-level main control unit, setting the adjustment target of the constant current drive circuit to a preset target current for attracting, and controlling the constant current drive circuit to output electrical energy to the electromagnetic brake coil specifically include: Receive the target motion parameters sent by the host control unit and determine the initial starting torque in the target motion parameters; The initial starting torque is combined to generate a zero-speed holding duty cycle, and the zero-speed holding duty cycle is output to the motor drive inverter to drive the steering wheel motor node to output the current torque; When the current torque reaches the preset hovering holding torque, a hovering ready confirmation parameter is generated; Based on the hovering readiness confirmation parameter, the adjustment target of the constant current drive circuit is set to the preset pull-in target current, and the constant current drive circuit is controlled to output electrical energy to the electromagnetic brake coil.

4. The method according to claim 1, characterized in that, After the step of generating the motor drive duty cycle by combining the target motion parameters and outputting it to the motor drive inverter to drive the steering wheel motor node into the operating condition, the method further includes: Obtain the local actual rotation speed and local actual steering angle of the current distributed steering wheel dedicated controller; Receive coordinated speed and coordinated steering angle broadcast by other distributed steering wheel dedicated controllers via industrial bus network; The difference between the local actual speed and the cooperative speed is calculated to obtain the speed synchronization deviation, and the difference between the local actual steering angle and the cooperative steering angle is calculated to obtain the steering synchronization deviation; The speed synchronization deviation and the steering synchronization deviation are substituted into a preset fuzzy control algorithm model for correction to obtain the compensated speed and the compensated steering angle. The motor drive duty cycle is corrected by combining the compensated speed and the compensated steering angle.

5. The method according to claim 4, characterized in that, The step of correcting the motor drive duty cycle by combining the compensated speed and the compensated steering angle specifically includes: Obtain the current load weight and determine the corresponding load adjustment coefficient based on the current load weight; Collect the three-phase stator current and rotor position of the steering wheel motor node; By combining the load regulation coefficient, the three-phase stator current, the rotor position, the compensated speed, and the compensated steering angle, a field-oriented control calculation is performed to obtain the target voltage vector; The space vector pulse width modulation operation is performed in conjunction with the target voltage vector to correct the motor drive duty cycle.

6. A control system, characterized in that, The control system includes: one or more processors and a memory; the memory is coupled to the one or more processors, the memory is used to store computer program code, the computer program code including computer instructions, and the one or more processors call the computer instructions to cause the control system to perform the method as described in any one of claims 1-5.

7. A computer-readable storage medium comprising instructions, characterized in that, When the instructions are executed on the control system, the control system performs the method as described in any one of claims 1-5.

8. A computer program product, characterized in that, When the computer program product is run on the control system, the control system performs the method as described in any one of claims 1-5.

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