Agv precision positioning method and system based on motor electric angle control

Abstract

The application discloses an AGV precise positioning method and system based on motor electric angle control, inherent parameters such as real-time electric angle and pole pair number of a traction motor, a reduction ratio, and an effective rolling circumference of a driving wheel are collected; cross-week development processing is carried out, adjacent period electric angle difference values are compared, and week jump variation is determined, and periodic electric angle is converted into continuous cumulative electric angle displacement; a target cumulative electric angle displacement of a target parking point is read, and a remaining displacement is calculated; a braking distance threshold value is determined according to a current speed and a preset braking deceleration, and when the remaining displacement meets the threshold value, the speed loop is switched to the position loop control; in the position loop stage, the target cumulative electric angle displacement is taken as a control target, a motor torque instruction is directly output after being limited in amplitude by a torque amplitude and a change rate, and when a position error enters a preset window, an integral term is cleared to suppress overshoot, and precise parking is realized. The application realizes full-closed loop end positioning by using motor self angle feedback, does not need an additional position sensor, and has good parking consistency.

Description

Technical Field

[0001] This invention belongs to the field of motion control and parking positioning technology of automated guided vehicles (AGVs), specifically relating to a low-cost, precise parking positioning method and system based on drive motor angular displacement information, auxiliary measurement displacement information, and target angle correction mechanism. Background Technology

[0002] Automated Guided Vehicles (AGVs), as core equipment in intelligent logistics systems, are widely used in manufacturing production lines for material handling, warehousing and logistics for cargo sorting, and hospital drug delivery. The precise positioning capability of an AGV directly determines its docking accuracy with loading / unloading equipment, shelves, charging stations, and other target mechanisms, making it one of the core indicators for evaluating the performance of an AGV system.

[0003] However, existing automated guided vehicle (AGV) positioning technologies have the following problems.

[0004] 1. Laser reflector positioning: Reflectors are deployed along the path, and their positions are determined by laser triangulation, achieving an accuracy of ±1 to 3 mm. However, this method has significant drawbacks: 2 to 4 reflectors need to be deployed at each parking point, resulting in high costs for large projects; reflectors are susceptible to dust contamination or obstruction, leading to high maintenance costs; and they need to be redeployed when the route is adjusted, resulting in poor scalability. 2. Laser SLAM technology: This technology enables autonomous navigation by using an onboard LiDAR to scan the environment in real time, eliminating the need for pre-deployed reflectors. However, pure SLAM positioning accuracy is typically ±10–30 mm, with cumulative errors; high-precision LiDAR units cost between 15,000 and 50,000 RMB or more, resulting in high hardware costs; the algorithm is complex and prone to positioning drift in dynamic environments. 3. Magnetic strip / QR code assisted positioning: Magnetic strips are laid along the path, supplemented by RFID or QR code identification stations, which has a lower cost. However, the positioning accuracy is limited (±10~30mm), and auxiliary markers still need to be deployed at each parking point, resulting in poor scalability.

[0005] Since most existing high-precision AGV parking solutions rely on external fixed markers or high-cost sensors, they suffer from high deployment costs, heavy maintenance workload, and inconvenient path adjustment for fixed-path, repetitive parking conditions. Relying solely on drive wheel displacement for parking positioning is susceptible to factors such as tire wear, load variations, changes in ground adhesion conditions, and slippage, leading to decreased consistency in repeated parking. Therefore, designing a precise AGV positioning method that maintains low cost while achieving high accuracy and maintainability for fixed-path, repetitive parking conditions has become a pressing technical problem in this field. Summary of the Invention

[0006] The summary section of this application is intended to provide a brief overview of the concepts, which will be described in detail in the detailed description section below. This summary section is not intended to identify key or essential features of the claimed technical solutions, nor is it intended to limit the scope of the claimed technical solutions.

[0007] To address the problems and shortcomings of existing technologies, the present invention aims to provide a precise positioning method and system for AGVs based on motor electrical angle control. It uses cumulative electrical angular displacement to convert into vehicle displacement and combines dynamic switching control, auxiliary displacement consistency verification, and target parking parameter write-back correction mechanism. It can be applied to fixed path repeated parking scenarios and requires minimal modification to existing drive systems.

[0008] This invention addresses the problems of existing fixed-path AGVs, which rely heavily on external fixed markers such as laser reflectors, QR codes, and magnetic strips during the final stop process, resulting in high deployment and maintenance costs. Furthermore, relying solely on drive wheel displacement estimation can lead to insufficient stopping accuracy and repeatability due to factors such as slippage, wheel diameter changes, and load variations. Specifically, in material handling scenarios with fixed paths, repetitive stopping, and high docking accuracy requirements, a method is needed that eliminates the need for additional external positioning markers at each stopping point, utilizes existing drive system information for precise final stopping, and can maintain and correct stopping deviations during long-term operation.

[0009] To achieve the above objectives, the present invention provides the following technical solution: As a first aspect of this application, the present invention discloses a precise positioning method for AGVs based on motor electrical angle control, comprising the following steps: Step S1: After the AGV is powered on or receives a parking task, collect the real-time electrical angle information and inherent physical parameter information of the traction motor on the AGV. The inherent physical parameter information includes the number of pole pairs of the traction motor, the transmission reduction ratio, and the effective rolling circumference of the drive wheel. Step S2: Calculate the current cumulative electrical angle displacement based on the real-time electrical angle information through cross-cycle unfolding processing; Step S3: The main control unit reads the target cumulative electrical angular displacement corresponding to the target parking point in the current parking task, and calculates the remaining displacement from the current position of the AGV to the target parking point in combination with the current cumulative electrical angular displacement; Step S4: Calculate the braking distance threshold for switching from speed loop control to position loop control based on the current speed of the AGV and the preset maximum braking deceleration. When the remaining displacement or remaining angle meets the braking distance threshold, the speed loop control switches to the position loop control. Step S5: In the position loop control stage, the target cumulative electrical angular displacement is used as the control target. After amplitude and rate of change are limited, a motor torque command is output to perform end deceleration and stopping control on the AGV.

[0010] Preferably, in step S2, the cross-cycle unfolding process first calculates the electrical angle difference between the current sampling cycle and the previous sampling cycle. When the electrical angle difference is greater than the preset cross-cycle threshold, a cycle jump is determined to have occurred. The cumulative number of cycles is incremented or decremented based on the current running direction of the AGV. Then, the current cumulative electrical angle displacement is calculated based on the cumulative number of cycles, the electrical angle of the current sampling cycle, and the initial electrical angle recorded when the parking task begins.

[0011] Preferably, in step S3, the remaining displacement can be obtained using global path coordinates or relative coordinates of the parking task; if global path coordinates are used to calculate the remaining displacement... Represented as: ; in, Indicates the cumulative electrical angular displacement of the target. This indicates the cumulative electrical angular displacement of the current task. and The starting position of the current parking task is used as the reference point. This is expressed as the transmission reduction ratio. This is expressed as the number of pole pairs of the traction motor. This represents the effective rolling circumference of the drive wheels; if the remaining displacement is calculated using the relative coordinate method for the parking task... Represented as: ; in, Indicates the cumulative electrical angular displacement of the target. This indicates the cumulative electrical angular displacement of the current task. and The cumulative electrical angular displacement at the start of the parking task is taken as the zero point; the current task's cumulative electrical angular displacement increment... Based on the current cumulative electric angular displacement Subtract the cumulative electrical angular displacement at the start of the parking task The target cumulative electrical angular displacement increment is obtained. It is obtained through teaching calibration or path distance conversion.

[0012] Preferably, in step S4, the switching rule for the speed loop control and position loop control is as follows: When the main control unit determines the remaining displacement Braking distance threshold If the AGV is still in the long-distance travel phase, then speed loop control will continue to be used; When the main control unit determines the remaining displacement ≤ Braking distance threshold When this occurs, it indicates that the AGV has entered the end braking stage, and the main control unit will switch the control mode from speed loop control to position loop control. The braking distance threshold It can be represented as, ; in, Represented as the current speed, This represents the preset maximum braking deceleration. This is expressed as a safety margin.

[0013] Preferably, in step S5, the cumulative electrical angular displacement error and its rate of change are first calculated based on the target cumulative electrical angular displacement and the current cumulative electrical angular displacement, and a target torque command is generated. Then, the target torque command is subjected to torque limiting and rate of change limitation to obtain the final target torque command. When the cumulative electrical angular displacement error is less than the preset window threshold, the position loop integral term is cleared to zero; When the cumulative electrical angular displacement error and its rate of change are both less than the parking position error threshold and parking allowable angular velocity threshold When the preset number of judgments is reached, the system determines that the parking is complete and outputs a zero torque command.

[0014] Preferably, the AGV operation and stopping process also includes slippage verification, specifically including the following steps: The encoder counts of the left and right driven measuring wheels in the auxiliary measuring unit are collected respectively. The cumulative displacement on the left and right ground sides is calculated, and the average value of the two is taken as the actual displacement on the ground side in the direction of the vehicle centerline. The cumulative displacement on the drive side is calculated based on the current cumulative electrical angular displacement, the effective rolling circumference of the drive wheel, the transmission reduction ratio, and the number of pole pairs of the traction motor. Calculate the consistency difference between the cumulative displacement on the drive side and the actual displacement on the ground side. When the consistency difference is greater than the preset slippage threshold, it is determined that the drive wheel has slipped or the displacement estimation is distorted.

[0015] Preferably, when slippage is detected, at least one of the following processing strategies can be executed. Output a slippage alarm signal to the host computer or vehicle display unit; This parking result is recorded as an abnormal sample; Automatic parameter learning or automatic updates based on the current parking results are prohibited. We request that maintenance personnel perform manual retesting and calibration.

[0016] Preferably, when the AGV has a stable parking deviation at a certain parking point, the main control unit receives the parking offset measured and input by an external measuring device. Calculate the target cumulative electric angular displacement compensation value The corrected cumulative electric angle displacement of the target is obtained by correcting the original cumulative electric angle displacement of the target based on the direction of the parking deviation. It is then written to non-volatile memory for subsequent tasks at that parking point to use.

[0017] As a second aspect of this application, the present invention discloses an AGV precision positioning system based on motor electrical angle control, comprising: The output shaft of the traction motor is connected to the drive wheel through a reduction mechanism, and the drive wheel contacts the ground to drive the AGV to move. The motor controller is connected to the input terminal of the traction motor and is used to receive control commands output by the main control unit to drive the traction motor; An angle acquisition unit is connected to the shaft end of the traction motor and is used to collect angle information corresponding to the rotation angle of the traction motor; The auxiliary measurement unit is installed at the bottom of the AGV body to obtain the actual displacement information of the AGV relative to the ground; The communication unit is used to receive parking point parameters, calibration instructions and parking deviation values ​​sent by external devices, and to return alarm status, slippage status and parameter update results to external devices. The non-volatile memory is used to store the target cumulative electrical angular displacement, target compensation value, switching threshold parameter, slippage threshold parameter and maintenance record corresponding to multiple parking points; The main control unit is connected to the angle acquisition unit, motor controller, auxiliary measurement unit, communication unit and non-volatile memory. It is used to receive the angle information, actual displacement information and calibration instructions, and to perform cumulative electrical angular displacement calculation, displacement conversion, remaining distance calculation, control mode switching, slippage judgment and target parking parameter update control. Then it outputs speed control instructions, position control instructions or torque control instructions to the motor controller.

[0018] Preferably, the auxiliary measurement unit includes a left driven measuring wheel, a right driven measuring wheel, and a left encoder and a right encoder connected to the left and right driven measuring wheels. The left and right driven measuring wheels maintain rolling contact with the ground through elastic clamping mechanisms, causing them to rotate with the vehicle body during AGV operation. The angle acquisition unit consists of a rotary transformer and a decoding chip. The rotary transformer outputs sine and cosine analog signals, and the decoding chip converts the analog signals into digital angle signals, which are then sent to the main control unit.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a precise positioning method and system for AGVs based on motor electrical angle control. By expanding the periodic electrical angle of the drive motor across cycles, a conversion relationship is established between the cumulative electrical angular displacement and the vehicle's travel displacement, enabling AGV end-point parking control without relying on external fixed markers at the parking point. A braking distance threshold based on the current speed and a preset deceleration is used, allowing the switching timing between speed loop control and position loop control to adaptively adjust according to changes in operating conditions, thereby reducing efficiency loss due to premature switching and parking errors caused by late switching. By comparing the consistency between the cumulative displacement on the drive side and the actual displacement on the ground side, displacement estimation distortions caused by slippage, wheel diameter changes, or changes in adhesion conditions can be identified, thus improving parking reliability. By introducing a write-back correction mechanism for the target cumulative electrical angular displacement, parking deviations can be continuously corrected and saved during maintenance, thereby improving parking repeatability accuracy and consistency over long-term operation. This invention mainly utilizes the existing traction motor angle signal of the AGV for parking position calculation; the auxiliary measuring wheel is only used to verify the reliability of the drive side displacement. For scenarios involving repeated parking along a fixed path, there is no need to install additional reflectors, QR codes, or other fixed markers at the parking spots. When a stable deviation occurs at a parking spot after long-term use, maintenance can be completed by measuring the deviation value and writing back the target cumulative electrical angular displacement. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application.

[0021] In the attached diagram: Figure 1 This is a flowchart illustrating the steps of the AGV precise positioning method in an embodiment of the present invention. Figure 2 This is a structural connection diagram of the AGV precision positioning system in an embodiment of the present invention; Figure 3 This is a schematic diagram of the process for calculating the cumulative displacement on the drive side in the precise positioning method of AGV in an embodiment of the present invention; Figure 4 This is a schematic diagram of the process of switching between speed loop control and position loop control in the AGV precise positioning method of this invention. Figure 5 This is a schematic diagram of the parking control process at the end of the position control loop in the AGV precise positioning method of this invention. Figure 6 This is a schematic diagram illustrating the principle of the auxiliary measurement unit and slippage consistency verification within the AGV precise positioning method in this embodiment of the invention. Figure 7This is a schematic diagram of the target cumulative electrical angular displacement calibration and write-back process in the AGV precise positioning method of this invention. Detailed Implementation

[0022] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0023] It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other.

[0024] Example 1 In this embodiment, a precise positioning system for AGVs based on motor electrical angle control is disclosed, such as... Figure 2 As shown, it includes at least a traction motor, a reduction mechanism, a drive wheel, an angle acquisition unit, a main control unit, a motor controller, an auxiliary measurement unit, a communication unit, and a non-volatile memory.

[0025] The traction motor provides driving force for the AGV. Its input is connected to the motor controller, and the input of the reduction gear is connected to the output shaft of the traction motor. The output of the reduction gear is connected to the drive wheels, which contact the ground and drive the AGV along a predetermined path. The traction motor, reduction gear, and drive wheels are assembled into a powertrain, which is rigidly fixed to the bottom of the AGV frame via flanges on the reduction gear housing. The drive wheels are positioned symmetrically on either side of the vehicle's width, with the traction motor located slightly inside and above the drive wheels.

[0026] The angle acquisition unit is used to collect angle information corresponding to the rotation angle of the traction motor. The angle acquisition unit is located at the shaft end of the traction motor and can reflect the rotation state of the traction motor in real time. In this embodiment, the angle acquisition unit can be composed of a rotary transformer and a decoding chip. The rotary transformer outputs sine and cosine analog signals, which are then converted into digital angle signals by the decoding chip and sent to the main control unit. Alternatively, the angle acquisition unit can also employ other sensing structures capable of outputting absolute angle information or equivalent angular displacement information.

[0027] The main control unit is connected to the angle acquisition unit, motor controller, auxiliary measurement unit, communication unit, and non-volatile memory. The main control unit receives electrical angle information, auxiliary displacement measurement information, and external calibration information, and executes control logic such as cumulative electrical angular displacement calculation, displacement conversion, remaining distance calculation, control mode switching, slippage determination, and target parking parameter updates.

[0028] The motor controller is connected to the main control unit and is used to drive the traction motor according to the speed control command, position control command or torque control command output by the main control unit.

[0029] The auxiliary measurement unit is located at the bottom of the AGV body and is used to acquire the actual displacement information of the AGV relative to the ground. The auxiliary measurement unit includes a left driven measuring wheel, a right driven measuring wheel, and a left encoder and a right encoder connected to the left and right driven measuring wheels. The left and right driven measuring wheels maintain rolling contact with the ground through elastic clamping mechanisms, causing them to rotate with the movement of the AGV body during operation. The left and right driven measuring wheels are used to acquire the left and right ground displacements, respectively, to improve the ability to detect slippage and eccentric slippage.

[0030] The communication unit is used to receive parking point parameters, calibration instructions, and parking deviation values ​​sent by the host computer, industrial touch screen, handheld terminal, or other external devices, and can return alarm status, slippage status, and parameter update results to external devices.

[0031] The non-volatile memory is selected as Flash, EEPROM or other non-volatile storage unit, used to store the target cumulative electrical angular displacement, target compensation value, switching threshold parameter, slippage threshold parameter and maintenance record corresponding to multiple parking points.

[0032] The angle acquisition unit outputs sine and cosine analog signals via a rotary transformer, which are then converted into digital angle signals by a decoding chip and sent to the main control unit. The main control unit simultaneously receives actual ground displacement information from the auxiliary measurement unit, external calibration commands and parking parameters from the communication unit, and reads data such as the target cumulative electrical angular displacement and threshold values ​​stored in the non-volatile memory. Based on this, it executes logic such as cumulative electrical angular displacement calculation, displacement conversion, remaining distance calculation, slippage detection, and control mode switching, and outputs speed, position, or torque control commands to the motor controller, which then drives the traction motor.

[0033] In this embodiment, a precise positioning method for AGVs based on motor electrical angle control is also disclosed, such as... Figure 1 As shown, the specific steps include: Step S1: After the AGV is powered on or receives a parking task, collect the real-time electrical angle information and inherent physical parameter information of the traction motor on the AGV. The inherent physical parameter information includes the number of pole pairs of the traction motor, the transmission reduction ratio, and the effective rolling circumference of the drive wheel. Step S2: Calculate the current cumulative electrical angular displacement based on the real-time electrical angle information through cross-cycle unfolding processing; Step S3: The main control unit reads the target cumulative electrical angular displacement corresponding to the target parking point in the current parking task, and calculates the remaining displacement from the current position of the AGV to the target parking point by combining the current cumulative electrical angular displacement and the inherent physical parameter information. Step S4: Calculate the braking distance threshold for switching from speed loop control to position loop control based on the current speed of the AGV and the preset braking deceleration. When the remaining displacement or remaining angle meets the braking distance threshold, switch from speed loop control to position loop control. Step S5: In the position loop control stage, the target cumulative electrical angular displacement is used as the control target. After amplitude and rate of change are limited, the motor torque command is output to perform end deceleration and stopping control on the AGV.

[0034] Regarding step S1, after the AGV is powered on or receives a parking task, the real-time electrical angle information and inherent physical parameter information of the traction motor on the AGV are collected. Specifically, after the AGV is powered on or receives a parking task, the main control unit reads the real-time electrical angle information and inherent physical parameter information of the traction motor. The inherent physical parameter information includes the transmission reduction ratio. Number of pole pairs of traction motor Effective rolling circumference of the drive wheel Maximum braking deceleration Safety margin Slippage threshold and the position loop error window threshold Parameters such as the number of pole pairs of the traction motor. These are inherent parameters of the motor, determined by the motor winding design. Transmission reduction ratio. It is the ratio of input speed to output speed, determined by gears or transmission mechanisms. Effective rolling circumference of the drive wheel. It is the actual distance a wheel travels in one revolution under actual load, and is determined by factors such as wheel diameter, material deformation, and ground conditions.

[0035] For step S2, the current cumulative electrical angle displacement is calculated based on the real-time electrical angle information through cross-cycle unfolding processing. Specifically, the cumulative electrical angle displacement is obtained by performing cross-cycle unfolding processing on the real-time electrical angle. Cross-cycle unfolding processing involves comparing the electrical angle difference between the current sampling period and the previous sampling period. When the electrical angle difference exceeds a preset cross-cycle threshold, a cycle jump is determined, and the cumulative number of revolutions is incremented or decremented based on the AGV's current running direction to obtain the current cumulative electrical angle displacement. If the parking point has previously undergone manual maintenance calibration, the main control unit reads the corrected target cumulative electrical angle displacement as the current parking control target.

[0036] Specifically, the electrical angle is acquired in real time by the system's acquisition unit and sent to the main control unit. Since the electrical angle is typically a periodic angular quantity, it may... The electrical angle may vary cyclically within an equivalent period, making it unsuitable for direct long-distance displacement accumulation. Therefore, the main control unit compares the difference between the electrical angles of two adjacent sampling periods. Let the range of the real-time electrical angle output by the angle acquisition unit be... The current sampling period electrical angle is The electrical angle of the previous sampling period was The original angle difference is The cross-cycle threshold is determined based on the maximum possible change in electrical angle within a single control cycle. Let the maximum change in electrical angle of the traction motor within a single control cycle at its maximum permissible speed be... Then the cross-cycle threshold Should meet In this embodiment, when the control cycle is short enough and the change in electrical angle per cycle is less than 90°, it can be taken as... =180°. Correspondingly, the positive cross-cycle threshold is The negative cross-cycle threshold is .when Greater than the preset When, it indicates that the real-time electrical angle jumps from near 0° to around 360°; when Less than preset When the time is reached, it indicates that the real-time electrical angle jumps from nearly 360° to around 0°.

[0037] The main control unit is set to accumulate electrical angle revolutions. At the start of the parking task, Initialize to the initial cumulative lap count corresponding to the current parking task or initialize to zero, and record the initial electrical angle. The cumulative lap count rules are as follows: when When the AGV is in the forward direction or the traction motor speed feedback is positive, the electrical angle is determined to have crossed from nearly 360° to near 0°, and the cumulative number of revolutions is executed as follows: ; when When the AGV is in the reverse direction or the traction motor speed feedback is negative, the electrical angle is determined to have crossed from near 0° to approximately 360°, and the cumulative number of revolutions is calculated as follows: ; when If no cycle has occurred, the cumulative number of laps remains unchanged. .

[0038] If the direction of the electrical angle across the cycle is inconsistent with the AGV's running direction, the main control unit can maintain the accumulated number of revolutions from the previous cycle and record the angle anomaly flag to avoid erroneous accumulation caused by interference pulses. Current accumulated electrical angular displacement. Obtained as follows: ; in, This is the initial electrical angle recorded at the start of the parking task. If the system uses global path coordinates, then... It can also be the global cumulative electrical angular displacement relative to the zero point of the path. Through the above processing, the originally periodic real-time electrical angle can be converted into a cumulative electrical angular displacement that can reflect the long-distance cumulative motion process.

[0039] Regarding step S3, the main control unit reads the target cumulative electrical angular displacement corresponding to the target parking point in the current parking task, and calculates the remaining displacement or remaining angle from the current position of the AGV to the target parking point based on the current cumulative electrical angular displacement. In this embodiment, the target cumulative electrical angular displacement and the current cumulative electrical angular displacement can be represented using global path coordinates or parking task relative coordinates. The global path coordinate method refers to continuously accumulating the electrical angular displacement during the AGV's operation using a preset path zero point as a reference; the parking task relative coordinate method refers to accumulating the change in electrical angular displacement during the parking process using the current parking task start position as a reference and the cumulative electrical angular displacement corresponding to the start time of the parking task as the zero point. Therefore, the two methods differ only in the reference point; essentially, both calculate the remaining distance based on the difference in cumulative electrical angular displacement between the target position and the current position.

[0040] Specifically, if a global path coordinate method is used, the cumulative electrical angular displacement corresponding to the target parking point is expressed as... The cumulative electric angular displacement of the current task is expressed as: Target cumulative electric angular displacement Cumulative electrical angular displacement with current mission Using the same coordinate reference. The remaining electrical angular displacement difference is determined by... We obtain that when the remaining electrical angular displacement difference is positive, it indicates that forward driving is required to reach the target; when the remaining electrical angular displacement difference is negative, it indicates that reverse driving is required to retreat. Therefore, the remaining displacement... Represented as: ; in, This is expressed as the transmission reduction ratio. This is expressed as the number of pole pairs of the traction motor. This represents the effective rolling circumference of the drive wheels. If a relative coordinate system is used for parking tasks, then... This represents the cumulative electrical angular displacement from the starting point of the parking task to the target parking point. This represents the cumulative electrical angular displacement from the starting point of the parking task to the current position, with both values ​​taking the starting point of the parking task as zero. At this point, the remaining electrical angular displacement difference is... If we obtain the remaining displacement, then... Represented as The two methods described above are essentially equivalent, and the choice can be made based on the user's task data management habits.

[0041] Furthermore, at the start of the parking task, the main control unit records the current cumulative electrical angular displacement as the cumulative electrical angular displacement at the start of the task. During AGV operation, the main control unit continuously updates the current cumulative electrical angular displacement according to the cross-cycle unfolding process in step S2. And calculate the cumulative electric angular displacement of the current task. : ; in, This represents the cumulative electrical angular displacement at the start of the parking task. The target cumulative electrical angular displacement... This can be obtained through two methods: teaching calibration and path distance conversion. For teaching calibration: During the AGV's teaching process at the target parking point, as it moves from the starting point of the parking task to the target parking position, the main control unit records the cumulative electrical angular displacement change generated during this process, which is then used as the target cumulative electrical angular displacement corresponding to that parking point, expressed as: ; in, This represents the cumulative electrical angular displacement recorded when the AGV reaches the target parking point. Regarding the path distance conversion method: when the path distance from the starting point of the parking task to the target parking point is known... At that time, it can be calculated based on the parameters of the drive system, and is expressed as: ; in, This indicates the path distance from the starting point of the parking task to the target parking point.

[0042] For step S4, the braking distance threshold for switching from speed loop control to position loop control is calculated based on the current speed of the AGV and the preset braking deceleration. When the remaining displacement or remaining angle meets the braking distance threshold, the speed loop control switches to position loop control.

[0043] like Figure 4 As shown, the control flow is divided into a speed loop stage and a position loop stage. Based on the current speed... Preset maximum braking deceleration and safety margin Calculate the braking distance threshold when switching from the speed loop to the position loop. , ; in, For safety margin; when ≤ At this time, the control switches from speed loop to position loop. The preset maximum braking deceleration... Safety margin can be obtained through no-load, rated load, or typical operating condition tests, or different values ​​can be preset according to different load conditions. Used to compensate for controller sampling delay, motor drive response delay, speed estimation error, braking deceleration calibration error, and parking distance fluctuations caused by changes in wheel-to-ground adhesion. Safety margin The safety margin can be determined through calibration tests; in one embodiment, it is... It can be set as follows: ; in, It is the sum of the main control unit's calculation delay, the motor drive response delay, and the actuator's response delay. This is the minimum distance margin, used to compensate for wheel diameter errors, changes in ground adhesion, and fluctuations in braking distance. During the system calibration phase, multiple braking tests can be conducted under no-load, rated load, and typical ground conditions, recording the deviation between the actual stopping distance and the theoretical braking distance, and determining the required braking distance accordingly. .

[0044] The switching decision between speed loop control and position loop control is as follows: When the main control unit makes a judgment > If the AGV is still in the long-distance travel phase, speed loop control should continue to be used to ensure operating efficiency. When the main control unit makes a judgment ≤ When this occurs, it indicates that the AGV has entered the end-of-life braking stage. The main control unit switches the control mode from speed loop to position loop, using the target cumulative electrical angular displacement as the control target to implement precise stopping.

[0045] To reduce repeated conversions between the distance and angle domains, the main control unit can also switch and make judgments within the angle domain. The braking distance threshold needs to be set. Converted to braking angle threshold , represented as: ; When satisfied At this time, the main control unit switches from speed loop control to position loop control. The angle domain judgment and distance domain judgment are based on the same drive chain conversion relationship, and are equivalent implementations under the same control concept.

[0046] Regarding step S5, in the position loop control stage, the target cumulative electrical angular displacement is used as the control target. After amplitude and rate of change limiting, a motor torque command is output to perform end-of-line deceleration and stopping control on the AGV. Specifically, in the position loop control stage, when the absolute value of the error between the target cumulative electrical angular displacement and the current cumulative electrical angular displacement is less than a preset error window threshold, the integral term of the position loop controller is cleared, or the integral gain is reduced to zero or to a preset small value to reduce end-of-line stopping overshoot and improve the stopping convergence process. Specifically, after entering the end-of-line stopping stage, the main control unit no longer converts the position error into a speed command first, but directly generates the target torque command or equivalent current reference for the traction motor based on the deviation between the target cumulative electrical angular displacement and the current cumulative electrical angular displacement. Let the target cumulative electrical angular displacement be... The current cumulative electric angular displacement is The cumulative electrical angular displacement error is: ; Assume the current cumulative electric angular displacement change rate is The difference in electrical angular displacement between adjacent sampling periods can be obtained from the cumulative difference in electrical angular displacement: ; in, To control the cycle, the main control unit generates the target torque command based on the cumulative electrical angular displacement error and the cumulative electrical angular displacement change rate. ; in, This is the position torque proportionality coefficient. The integral coefficient of position torque. The velocity damping coefficient, This is the integral term for the position error. The integral term for the position error can be updated as follows: ; in, For the amplitude limiting function, and These are the lower and upper limits of the integral term, respectively.

[0047] To avoid sudden torque changes during the final stopping phase, the main control unit limits the torque amplitude and torque change rate of the target torque command to obtain the final target torque command: ; in, For a limited step function, and These are the minimum and maximum allowable torques, respectively. This represents the maximum allowable torque variation within a single control cycle. To reduce overshoot during the final stop process, in this embodiment, as... Figure 5 As shown, when the absolute value of the position error satisfies At this time, the main control unit clears the integral term of the position loop controller to zero, so that the target torque is mainly determined by the proportional term and the velocity damping term: ; in, The preset error window threshold can be obtained through calibration. When both the cumulative electrical angular displacement error and the cumulative electrical angular displacement change rate simultaneously meet the parking judgment condition: ; ; in, This is the permissible parking position error threshold. The allowed angular velocity threshold for parking has been exceeded for an extended period of time. When the main control unit determines that the AGV has reached the target parking position, the main control unit outputs a zero torque command.

[0048] Example 2 Based on Embodiment 1, in this embodiment, the main control unit synchronously receives ground-side displacement information output by the auxiliary measurement unit during AGV operation and parking. The left and right driven measurement wheels do not participate in AGV traction drive; they are only used to measure the actual driving displacement of the AGV relative to the ground. Since they do not bear traction output, under normal contact conditions, their encoder counts can reflect the actual displacement of the vehicle body relative to the ground, used to verify the reliability of the cumulative drive-side displacement calculated from the cumulative electrical angular displacement of the drive motor. Figure 3 As shown.

[0049] Based on the cumulative electrical angular displacement, the number of pole pairs of the traction motor, the transmission reduction ratio, and the effective rolling circumference of the drive wheels, the cumulative electrical angular displacement is converted into the cumulative displacement of the AGV along the target path. Specifically, since the transmission relationship between the drive wheels and the motor shaft is fixed, there is a definite conversion ratio between the cumulative electrical angular displacement and the vehicle's travel distance. The main control unit calculates the cumulative electrical angular displacement... Effective rolling circumference of the drive wheel Transmission reduction ratio and the number of pole pairs of the traction motor Calculate the cumulative displacement on the driving side, if For the global cumulative electrical angular displacement relative to the path zero, the drive-side path coordinates can be expressed as: ; in, For cumulative electric angular displacement, For the effective rolling circumference of the drive wheel, This is the transmission reduction ratio. This represents the number of pole pairs of the traction motor. The effective rolling circumference of the drive wheel. The reduction ratio can be obtained by calibrating based on the nominal diameter of the drive wheels. The total transmission ratio between the traction motor and the drive wheel, and the number of pole pairs. These are inherent parameters of the traction motor.

[0050] The above conversion relationship reflects the correspondence between cumulative electrical angular displacement and AGV longitudinal travel displacement. In fixed-path applications, the position of the AGV along the path direction is represented as one-dimensional path coordinates. When the parking task begins, the main control unit records the path coordinates corresponding to the task's starting point. and initial cumulative electric angular displacement During AGV operation, the incremental displacement on the drive side relative to the starting point of the task is calculated based on the cumulative incremental electrical angular displacement. : ; The current path coordinates of the AGV are: ; If relative coordinates of the parking point are used, it can also be... Set to zero, directly with This is the current location.

[0051] like Figure 6 As shown, the count values ​​of the encoders of the left and right driven measuring wheels in the auxiliary measurement unit are collected respectively, and the cumulative displacement on the left and right ground sides is calculated respectively. The actual displacement on the ground side in the direction of the AGV body centerline is obtained based on the cumulative displacement on the left and right ground sides. The consistency of the actual displacement on the ground side is compared with the cumulative displacement on the drive side obtained by converting the cumulative electrical angular displacement to determine whether the AGV has experienced drive wheel slippage or displacement estimation distortion.

[0052] Let the effective rolling circumference of the left driven measuring wheel be... The effective rolling circumference of the right driven measuring wheel is The number of pulses corresponding to one revolution of the left encoder is... The number of pulses corresponding to one revolution of the right encoder is Let the cumulative count of the left encoder in the current sampling period be... The cumulative count of the left encoder in the previous sampling period was The current sampling period's cumulative count for the right encoder is... The cumulative count of the right encoder in the previous sampling period was Therefore, within the current sampling period, the incremental displacement on the ground side corresponding to the left driven measuring wheel is: ; The ground-side incremental displacement corresponding to the right driven measuring wheel is: ; in, This represents the incremental displacement on the left side of the ground. This represents the incremental displacement on the right side of the ground. If the AGV has both forward and backward movement directions, the encoder count difference carries a positive and negative direction. The main control unit determines the sign of the incremental displacement based on the encoder counting direction or the vehicle's running direction. The cumulative displacement on the left and right sides of the ground are updated as follows: ; ; in, This represents the cumulative displacement on the ground side corresponding to the left driven measuring wheel. This represents the cumulative displacement on the ground side corresponding to the right driven measuring wheel.

[0053] In the straight-line parking condition, the main control unit uses the average of the cumulative displacement on the left and right sides of the ground as the actual displacement on the ground side in the direction of the AGV's centerline: ; in, This represents the actual displacement on the ground side. Using the left-right average can reduce the impact of single-sided measuring wheel bounce, local ground unevenness, or encoder pulse fluctuations on displacement judgment. Simultaneously, the main control unit calculates the cumulative displacement on the drive side based on the cumulative electrical angular displacement of the drive motor. To determine whether the estimated drive-side displacement is affected by drive wheel slippage, wheel diameter mismatch, or changes in ground adhesion, the main control unit compares the cumulative drive-side displacement with the actual ground-side displacement. The consistency difference is calculated. : ; when ≤ At that time, it was considered that the estimated displacement on the driving side was in good agreement with the actual ground displacement; when > When the main control unit determines that the AGV is slipping, has mismatched wheel diameter parameters, abnormal adhesion conditions, or other situations that cause distortion in displacement estimation.

[0054] When slippage is detected, the main control unit can execute at least one of the following processing strategies: 1) Output a slippage alarm signal to the host computer or vehicle display unit; 2) Record this parking result as an abnormal sample; 3) Automatic parameter learning or automatic updates based on the current parking results are prohibited; 4) Request maintenance personnel to perform manual retesting and calibration.

[0055] The main control unit can also adjust the displacement based on the left and right ground sides. and Calculate the slippage criterion: ; when When the error exceeds the preset threshold, it can be determined that there is a difference in lateral attachment, inconsistent slippage of the left and right wheels, or posture deviation during the AGV end-of-line parking process, which facilitates maintenance personnel to further analyze the source of parking error.

[0056] Example 3 like Figure 7 As shown, during long-term operation of the AGV, factors such as tire wear, changes in road surface adhesion conditions, load variations, and changes in drive mechanism clearance can cause the parking position to gradually deviate due to relying solely on initial calibration parameters. To improve the consistency of repeated parking over long periods, this embodiment introduces a parking deviation write-back correction mechanism based on Example 1. When maintenance personnel discover a stable deviation of the AGV at a certain parking point, they can use a laser rangefinder, mechanical gauge, steel ruler, or other suitable devices to measure the parking deviation to determine the parking offset. The offset can be input into the main control unit via a host computer, handheld terminal, or debugging tool.

[0057] The main control unit receives the offset. Then, the corresponding target cumulative electric angular displacement compensation value is calculated according to the following relationship: ; in, This is the parking offset. For the effective rolling circumference of the drive wheel, This is the transmission reduction ratio. This represents the number of pole pairs of the traction motor. Then, based on the parking deviation direction, the cumulative electrical angular displacement of the original target is calculated. Perform incremental correction to obtain the corrected target cumulative electrical angular displacement. : ; The choice between plus or minus signs is determined based on the actual parking deviation direction. If the AGV's parking position is slightly ahead of the target position, the target cumulative electrical angular displacement should be increased or decreased along the compensation direction; if the parking position is slightly behind, the correction should be performed in the opposite direction. Specific sign rules can be uniformly determined by the main control unit based on the forward / backward direction and the parking deviation definition. After correction, the main control unit writes the corrected target cumulative electrical angular displacement into non-volatile memory so that the corrected parameters can be directly retrieved in the next task.

[0058] Example 4 Initial calibration can be performed when the AGV is first deployed, or when the drive wheels, reduction gear, or ground conditions are significantly changed due to replacement. Specifically, maintenance personnel drive the AGV into the target parking area at low speed in test mode, and guide the AGV to stop at the ideal docking position through manual observation or with the help of external measuring tools; the main control unit records the cumulative electrical angular displacement at this time as the initial target cumulative electrical angular displacement of that parking point. This data is then written to non-volatile memory. Subsequently, maintenance personnel can perform several repeated stop tests to calibrate the system, including at least the following parameters: the effective rolling circumference of the drive wheels based on the test results. Switching safety margin Error window threshold and slip threshold Parameters such as these are tuned to ensure that the AGV achieves better parking consistency under typical working conditions.

[0059] Example 5 Without departing from the concept of the present invention, this embodiment is based on the above embodiments and modified in the following ways: The angle acquisition unit is not limited to a rotary transformer; other sensors or detection structures capable of outputting equivalent absolute angular displacement information can also be used. The auxiliary measurement unit is not limited to two driven measuring wheels; it can also use one driven measuring wheel or other measurement structures that can acquire the actual displacement of the vehicle body relative to the ground. The position loop controller can be a PI controller, a weak integral controller, or other closed-loop controllers suitable for end-stage deceleration and stopping; The target cumulative electrical angular displacement compensation value can be generated by manually inputting the parking deviation, or it can be generated by the system based on historical parking error statistics when the credibility condition is met. However, automatic updates are not performed when slippage or abnormal samples are detected.

[0060] All technologies not described in detail in this invention are existing technologies. The above descriptions are merely some preferred embodiments of this disclosure and explanations of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalent features without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.

[0061] The above are merely preferred embodiments of the present invention, and the present invention may have other embodiments. Those skilled in the art can still modify the technical solutions described in the above embodiments, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A precise positioning method for AGVs based on motor electrical angle control, characterized in that, Includes the following steps: Step S1: After the AGV is powered on or receives a parking task, collect the real-time electrical angle information and inherent physical parameter information of the traction motor on the AGV. The inherent physical parameter information includes the number of pole pairs of the traction motor, the transmission reduction ratio, and the effective rolling circumference of the drive wheel. Step S2: Calculate the current cumulative electrical angle displacement based on the real-time electrical angle information through cross-cycle unfolding processing; Step S3: The main control unit reads the target cumulative electrical angular displacement corresponding to the target parking point in the current parking task, and calculates the remaining displacement from the current position of the AGV to the target parking point by combining the current cumulative electrical angular displacement and the inherent physical parameter information. Step S4: Calculate the braking distance threshold for switching from speed loop control to position loop control based on the current speed of the AGV and the preset maximum braking deceleration. When the remaining displacement or remaining angle meets the braking distance threshold, the speed loop control switches to the position loop control. Step S5: In the position loop control stage, the target cumulative electrical angular displacement is used as the control target. After amplitude and rate of change are limited, a motor torque command is output to perform end deceleration and stopping control on the AGV.

2. The AGV precise positioning method based on motor electrical angle control according to claim 1, characterized in that: In step S2, the cross-cycle unfolding process first calculates the electrical angle difference between the current sampling cycle and the previous sampling cycle. When the electrical angle difference is greater than the preset cross-cycle threshold, a cycle jump is determined. The cumulative number of cycles is incremented or decremented based on the current running direction of the AGV. Then, the current cumulative electrical angle displacement is calculated based on the cumulative number of cycles, the electrical angle of the current sampling cycle, and the initial electrical angle recorded when the parking task starts.

3. The AGV precise positioning method based on motor electrical angle control according to claim 2, characterized in that: In step S3, the remaining displacement can be obtained using global path coordinates or relative coordinates of the parking task; if global path coordinates are used to calculate the remaining displacement... Represented as: ； in, Indicates the cumulative electrical angular displacement of the target. This indicates the cumulative electrical angular displacement of the current task. and The starting position of the current parking task is used as the reference point. This is expressed as the transmission reduction ratio. This is expressed as the number of pole pairs of the traction motor. This represents the effective rolling circumference of the drive wheels; if the remaining displacement is calculated using the relative coordinate method for the parking task... Represented as: ； in, This represents the cumulative electrical angular displacement increment of the target. This indicates the cumulative electrical angular displacement increment for the current task. and The cumulative electrical angular displacement at the start of the parking task is taken as the zero point; the current task's cumulative electrical angular displacement increment... Based on the current cumulative electric angular displacement Subtract the cumulative electrical angular displacement at the start of the parking task The target cumulative electrical angular displacement increment is obtained. Through demonstration and standardization The path distance was calculated.

4. The AGV precise positioning method based on motor electrical angle control according to claim 3, characterized in that, In step S4, the switching rule for the speed loop control and position loop control is as follows: When the main control unit determines the remaining displacement Braking distance threshold If the AGV is still in the long-distance travel phase, then speed loop control will continue to be used; When the main control unit determines the remaining displacement ≤ Braking distance threshold When this occurs, it indicates that the AGV has entered the end braking stage, and the main control unit will switch the control mode from speed loop control to position loop control. The braking distance threshold It can be represented as, ； in, Represented as the current speed, This represents the preset maximum braking deceleration. This is expressed as a safety margin.

5. The AGV precise positioning method based on motor electrical angle control according to claim 4, characterized in that: In step S5, the cumulative electrical angular displacement error and its rate of change are first calculated based on the target cumulative electrical angular displacement and the current cumulative electrical angular displacement, and a target torque command is generated. Then, the target torque command is subjected to torque limiting and rate of change limitation to obtain the final target torque command. When the cumulative electrical angular displacement error is less than the preset window threshold, the position loop integral term is cleared to zero; When the cumulative electrical angular displacement error and its rate of change are both less than their respective preset thresholds and the preset number of judgments is continued, the parking is determined to be complete and a zero torque command is output.

6. The AGV precise positioning method based on motor electrical angle control according to claim 5, characterized in that, The AGV operation and stopping process also includes slippage verification, which specifically includes the following steps: The encoder counts of the left and right driven measuring wheels in the auxiliary measuring unit are collected respectively. The cumulative displacement on the left and right ground sides is calculated, and the average value of the two is taken as the actual displacement on the ground side in the direction of the vehicle centerline. The cumulative displacement on the drive side is calculated based on the current cumulative electrical angular displacement, the effective rolling circumference of the drive wheel, the transmission reduction ratio, and the number of pole pairs of the traction motor. Calculate the consistency difference between the cumulative displacement on the drive side and the actual displacement on the ground side; When the consistency difference is greater than the preset slippage threshold, it is determined that the drive wheel has slipped or the displacement estimation is distorted.

7. The AGV precise positioning method based on motor electrical angle control according to claim 6, characterized in that, When slippage is detected, at least one of the following processing strategies can be executed: Output a slippage alarm signal to the host computer or vehicle display unit; This parking result is recorded as an abnormal sample; Automatic parameter learning or automatic updates based on the current parking results are prohibited. We request that maintenance personnel perform manual retesting and calibration.

8. The precise positioning method for AGV based on motor electrical angle control according to claim 6, characterized in that: When the AGV exhibits a stable parking deviation at a certain parking point, the main control unit receives the parking offset measured and input by an external measuring device. Calculate the target cumulative electric angular displacement compensation value The corrected cumulative electric angle displacement of the target is obtained by correcting the original cumulative electric angle displacement of the target based on the direction of the parking deviation. It is then written to non-volatile memory for subsequent tasks at that parking point to use.

9. A precise positioning system for AGVs based on electric motor angle control, characterized in that, include: The output shaft of the traction motor is connected to the drive wheel through a reduction mechanism, and the drive wheel contacts the ground to drive the AGV to move. The motor controller is connected to the input terminal of the traction motor and is used to receive control commands output by the main control unit to drive the traction motor; An angle acquisition unit is connected to the shaft end of the traction motor and is used to collect angle information corresponding to the rotation angle of the traction motor; The auxiliary measurement unit is installed at the bottom of the AGV body to obtain the actual displacement information of the AGV relative to the ground; The communication unit is used to receive parking point parameters, calibration instructions and parking deviation values ​​sent by external devices, and to return alarm status, slippage status and parameter update results to external devices. The non-volatile memory is used to store the target cumulative electrical angular displacement, target compensation value, switching threshold parameter, slippage threshold parameter and maintenance record corresponding to multiple parking points; The main control unit is connected to the angle acquisition unit, motor controller, auxiliary measurement unit, communication unit and non-volatile memory. It is used to receive the angle information, actual displacement information and calibration instructions, and to perform cumulative electrical angular displacement calculation, displacement conversion, remaining distance calculation, control mode switching, slippage judgment and target parking parameter update control. Then it outputs speed control instructions, position control instructions or torque control instructions to the motor controller.

10. The AGV precision positioning system based on motor electrical angle control according to claim 9, characterized in that: The auxiliary measurement unit includes a left driven measuring wheel, a right driven measuring wheel, and a left encoder and a right encoder connected to the left and right driven measuring wheels. The left and right driven measuring wheels maintain rolling contact with the ground through elastic clamping mechanisms, causing them to rotate with the vehicle body during AGV operation. The angle acquisition unit consists of a rotary transformer and a decoding chip. The rotary transformer outputs sine and cosine analog signals, which are then converted into digital angle signals by the decoding chip and sent to the main control unit.

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