Wheel robot parking and starting control method

Abstract

A kind of wheeled robot parking and starting control method, the control method of parking includes the following steps: S1: control the wheel motor of driving wheel and reduce to zero, and the rotor position x of wheel motor is acquired in the moment of reducing to zero, and switch to parking mode;S2: in parking mode, the rotor position x1 of wheel motor is acquired in real time, calculate position deviation Δx=x-x1, the size and direction of stator magnetic field vector of wheel motor are acquired according to the position deviation;S3: the size and direction of stator magnetic field vector are dynamically adjusted to respond to position deviation Δx, so that the rotor of wheel motor is maintained at position x or maintained in the adjacent area of position x and keeps stable.The present application greatly reduces the complexity and cost of system, and can quickly switch parking and moving mode, improve reliability and maneuverability.

Description

Technical Field

[0001] The present invention relates to the technical field of wheeled robots, and in particular to a parking and starting control method for a wheeled robot. Background Art

[0002] Wheeled robots (typically available in two-, four-, or six-wheel configurations) typically operate with their drive wheels in speed control mode. When a given command is zero speed, the drive wheels stop rotating. Because wheeled robots are mobile, start-stop control can affect their reliability and maneuverability. This is particularly evident during starting and parking, when the robot must prevent slipping on slopes and respond quickly to movement commands.

[0003] CN 117842896A discloses a method and device for automatically releasing parking of a counterbalanced forklift AGV, and a counterbalanced forklift. The technical solution includes: receiving a parking control signal through a logic controller, controlling a push rod motor to reverse according to the parking control signal, and driving a wire pulling device to tighten when the push rod motor reverses; detecting the pulling torque of the wire pulling device through a pulling torque sensor; controlling the push rod motor to stop and lock when the pulling torque reaches a set value; and applying a brake device to brake when the push rod motor stops and locks.

[0004] CN 118322194A discloses a robot parking control method, device, system and robot. The robot parking control method includes: obtaining the parking state of the robot and the switch state of the robot's support legs; if the parking state is that parking is allowed and the switch state meets preset conditions, controlling the robot to park and controlling the robot's parking time; when the parking time reaches the target parking time, controlling the robot to stop parking.

[0005] However, the above two solutions have the following main defects: (1) the parking method is relatively complicated and requires auxiliary sensors or parking devices; (2) it is not possible to quickly switch between parking and moving modes. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a wheeled robot parking and starting control method with a simple design, high reliability and maneuverability, and fast mode switching.

[0007] The technical solution of the present invention is: a parking and starting control method for a wheeled robot, the parking control method comprising the following steps:

[0008] S1: Control the wheel motor of the driving wheel to decelerate to zero, obtain the rotor position x of the wheel motor at the moment of deceleration to zero, and switch to parking mode;

[0009] S2: In parking mode, the rotor position x1 of the wheel motor is obtained in real time, the position deviation Δx=x-x1 is calculated, and the magnitude and direction of the stator magnetic field vector of the wheel motor are obtained based on the position deviation;

[0010] S3: Dynamically adjust the magnitude and direction of the stator magnetic field vector in response to the position deviation Δx, so that the rotor of the wheel motor is maintained at position x or in an area adjacent to position x to remain stable.

[0011] Furthermore, in step S2, the method for obtaining the magnitude of the stator magnetic field vector of the wheel motor includes:

[0012] S2-1: The wheel motor's U, V, and W phases are used as input, and the rotor position x1 is used as output. The wheel driver uses the rotor position x as a given parameter and x1 as a feedback parameter to calculate Δx, which is the motor position deviation during parking.

[0013] S2-2: After the position deviation Δx is obtained by proportional control to Kp*Δx, it is limited by the limiter S. The absolute value of the limited control signal Kp*Δx is taken as the first q-axis voltage set value of SVPWM; the q-axis voltage of SVPWM is used to adjust the torque output by the wheel motor; the d-axis voltage of SVPWM is used to adjust the motor magnetic field. The q-axis voltage and d-axis voltage vectors are perpendicular to each other, and the resultant vector of the two is the magnitude of the stator magnetic field vector.

[0014] Furthermore, in step S2, the method for obtaining the direction of the stator magnetic field vector of the wheel motor includes:

[0015] S2-3: The position deviation Δx is directly limited by limiter S1, and the limiting threshold is 90°. When Δx is in the range of -90° to 90°, the output value of limiter S1 is Δx; when Δx<-90°, the output value of S1 is -90°; when Δx>90°, the output value of S1 is 90°. The rotor position x1 minus the output value of limiter S1 gives the SVPWM given value θ, where θ is the direction of the stator magnetic field vector.

[0016] Furthermore, the limiting threshold of the limiter S is selected to be 10% to 20% of the rated voltage of the wheel motor; and the d-axis voltage value of the SVPWM is set to 0.

[0017] Further, in step S3, the method for dynamically adjusting the size and direction of the stator magnetic field vector includes: calculating the offset of the rotor from position x to position x1 based on the acquired rotor positions x and x1; if the rotor offset is ≤90°, the stator magnetic field vector points to x; if the rotor offset is greater than 90°, the stator magnetic field vector will point to a direction that maintains a 90° angle with the rotor position x1, so as to resist the rotor offset with the maximum torque.

[0018] Furthermore, in step S1, when the main controller in the wheeled robot chassis receives the stop signal, it sends a zero speed command to the wheel driver, and the wheel driver starts to drive the wheel motor to decelerate to zero; at the moment of deceleration to zero, the wheel driver obtains the rotor position x of the wheel motor and switches to parking mode.

[0019] Furthermore, the control method for starting the wheeled robot includes the following steps:

[0020] Before starting, obtaining the first q-axis voltage given value in the parking mode;

[0021] When starting, switch to the speed mode and obtain the second q-axis voltage given value in the speed mode; superimpose the second q-axis voltage given value in the speed mode with the first q-axis voltage given value in the parking mode, and then control the speed of the wheel motor through SVPWM; when the speed of the wheel motor reaches the target threshold, stop superimposing the first q-axis voltage given value in the parking mode, and the speed control loop will fully assume the control task of the wheel motor.

[0022] Furthermore, the target threshold is 4% to 8% of the rated value of the wheel motor speed.

[0023] Furthermore, in S2, the wheel driver uses the rotor position x obtained when the wheel motor decelerates to zero as a given parameter, and obtains the rotor position x1 of the wheel motor as feedback in real time, and obtains the magnitude and direction of the stator magnetic field vector of the wheel motor according to the position deviation Δx.

[0024] The beneficial effects of the present invention are: on the one hand, it can be realized with only the hardware of the wheeled robot, without the need for additional auxiliary sensors or parking devices, which greatly reduces the system complexity and cost and improves the system reliability and adaptability; on the other hand, it can quickly switch between parking and moving modes, improving reliability and maneuverability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flowchart of a parking control method according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the regulation principle of the stator magnetic field vector magnitude and direction in parking mode according to an embodiment of the present invention;

[0027] Figure 3 2 is a schematic diagram of the stator magnetic field vector pointing principle of an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1The following figure shows a method for controlling the parking and starting of a wheeled robot. The modules involved in the entire control process include a main controller, a wheel driver, and a wheel motor. The parking control method specifically includes the following steps:

[0030] S101: Control the wheel motor of the driving wheel to decelerate to zero, obtain the rotor position x of the wheel motor at the moment of deceleration to zero, and switch to parking mode.

[0031] Specifically, when the main controller in the wheeled robot chassis receives a stop signal, it sends a zero-speed command to the wheel driver, which then starts decelerating the wheel motor to zero. At the moment of deceleration, the wheel driver obtains the rotor position x of the wheel motor and switches to parking mode. The main controller of the wheeled robot is referred to as the VCU.

[0032] S102: In parking mode, the rotor position x1 of the wheel motor is obtained in real time, the position deviation Δx=x-x1 is calculated, and the magnitude and direction of the stator magnetic field vector of the wheel motor are obtained according to the position deviation.

[0033] Specifically, in parking mode, the wheel driver uses the rotor position x obtained when the wheel motor decelerates to zero as a given parameter, and obtains the rotor position x1 of the wheel motor in real time as feedback. It adjusts the magnitude and direction of the stator magnetic field vector of the wheel motor according to the position deviation to achieve parking control. The principle of adjusting the magnitude and direction of the magnetic field vector in parking mode is as follows: Figure 2 As shown (all parts except the wheel motor are implemented in the wheel driver).

[0034] The wheel motors of this embodiment have position feedback. Here, a permanent magnet synchronous motor with an encoder is used as an example for illustration. The SVPWM modulation method commonly used in permanent magnet synchronous motors is adopted, specifically including the following steps:

[0035] A. The wheel motor's U, V, and W phases are used as input, and the rotor position x1 is used as the output signal, where x1 reflects the actual position of the motor rotor. The wheel driver uses the rotor position x as a given parameter and x1 as a feedback parameter to calculate Δx, the motor position deviation during parking.

[0036] B. The position deviation Δx is proportionally controlled (the proportional coefficient Kp needs to be adjusted based on the actual wheel motor and wheel driver; the adjustment method refers to conventional PID proportional coefficient tuning). After obtaining Kp*Δx, it is limited by limiter S, where the limiter threshold of limiter S is selected from 10% to 20% of the rated motor voltage. The absolute value of the limited control signal Kp*Δx is taken as the first q-axis voltage setpoint of the space vector pulse width modulation (SVPWM). The q-axis voltage is used to adjust the torque output by the wheel motor. The d-axis voltage of the SVPWM is used to adjust the motor magnetic field. Since magnetic field adjustment is not required here, it is directly set to 0. The q-axis voltage and d-axis voltage vectors are perpendicular to each other, and the resultant vector of the two is the magnitude of the stator magnetic field vector.

[0037] C. The position deviation Δx is also limited by limiter S1, with a threshold of 90°. When Δx is in the range of -90° to 90°, S1 outputs Δx. When Δx is less than -90°, S1 outputs -90°. When Δx is greater than 90°, S1 outputs 90°. The SVPWM given value θ is obtained by subtracting the output value of limiter S1 from the rotor position x1, where θ is the direction of the stator magnetic field vector.

[0038] In summary, the magnitude and direction of the stator magnetic field vector of the wheel motor can be obtained. The above method has the following advantages: (1) It simplifies the system design and does not require additional sensors or parking devices, thus reducing system complexity and cost; (2) Because external dependence is reduced, the reliability of the system is improved and the failure rate is reduced; (3) The adaptability of the system is enhanced, and it can adapt to different wheel motor and drive configurations, with better flexibility; (4) By precisely controlling the magnitude and direction of the stator magnetic field vector, the motor torque can be precisely adjusted, thereby improving the dynamic response performance and operating efficiency of the motor; (5) Due to the high voltage utilization and low harmonic characteristics of SVPWM technology, this method can also improve the energy efficiency of the motor and reduce electromagnetic interference.

[0039] S103: Dynamically adjust the magnitude and direction of the stator magnetic field vector in response to the position deviation Δx, so that the rotor of the wheel motor is maintained at position x or in an area adjacent to position x to remain stable.

[0040] Specifically, in this embodiment, the permanent magnet synchronous motor is characterized by the interaction between the stator magnetic field vector and the rotor magnetic field vector generating torque. For a given vector magnitude, a 90° angle between the two produces maximum torque. For a given angle, a greater vector magnitude results in greater torque.

[0041] In this embodiment, the wheel drive is realized by using Figure 2The modulation method in

[15] is used to obtain the stator magnetic field vector applied to the wheel motor. The magnitude and direction of this vector will change with the change of the position deviation Δx. The stator magnetic field vector interacts with the rotor magnetic field vector (the rotor magnetic field is generated by a permanent magnet), causing the wheel motor to generate torque to resist the change of Δx, and ultimately trying to keep the motor rotor near position x. The specific principle is as follows: Figure 3 As shown:

[0042] Figure 3 In (a), when the robot decelerates to zero, the rotor is at position x, and the wheel driver records this position. Starting from (b), the robot is in parking mode. During the rotation of the rotor, the rotor offset to x1 is recorded. If the rotor offset (the angular change from position x to position x1) is small, a smaller stator magnetic field vector will be generated, and the stator magnetic field vector points to x, as shown in Figure 3 As shown by the thick arrow in , as the offset increases, the amplitude of the stator magnetic field vector also increases, still pointing to the x direction, that is, Figure 3 As shown in (b), (c), (d), (g), (h) and (i) in Figure 1, when the rotor offset is ≤90°, the stator magnetic field vector points to x; when the rotor offset is greater than 90°, the stator magnetic field vector will maintain a 90° angle with the rotor position x1, thereby using the maximum torque to resist the rotor offset, as shown in Figure 1. Figure 3 As shown in (e) and (f).

[0043] In other words, this embodiment counteracts changes in position deviation Δx through the interaction between the stator magnetic field vector and the rotor magnetic field vector generated by the permanent magnets, maintaining the motor rotor close to position x. When the rotor offset is small, a smaller stator magnetic field vector is generated, pointing toward the initial position x. As the offset increases, the magnitude of the stator magnetic field vector increases, but it still points in the x direction. When the offset exceeds 90°, the stator magnetic field vector maintains a 90° angle with x1, providing maximum torque to counteract rotor offset. This solution has the following advantages:

[0044] (1) Precise control: By dynamically adjusting the magnitude and direction of the stator magnetic field vector, the motor rotor position can be precisely controlled to ensure the stability and accuracy of the rotor position;

[0045] (2) Adaptive adjustment: The magnitude and direction of the stator magnetic field vector can be adaptively adjusted according to the actual offset of the rotor, allowing the system to flexibly respond to different deviation conditions;

[0046] (3) Optimizing torque output: When the rotor offset is small, the system generates only the necessary small magnetic field vector, which helps save energy and reduce unnecessary torque output; as the offset increases, the system can increase the amplitude of the magnetic field vector to provide sufficient torque to correct the offset;

[0047] (4) Maximum torque utilization: When the offset exceeds 90°, the stator magnetic field vector maintains a 90° angle with the rotor position, so that the maximum torque can be used to resist the offset of the rotor, improving the response speed and stability of the system;

[0048] (5) Enhanced robustness: This method can maintain efficient operation under different offsets, indicating that the system has strong robustness and can maintain a stable position of the rotor under various conditions. By precisely controlling the magnetic field vector, the system can provide appropriate torque when needed, avoiding excessive energy consumption, thereby improving overall efficiency.

[0049] (6) Reduce wear and extend life: By reducing unnecessary torque output and precise control, the mechanical stress of the motor can be reduced, thereby reducing wear and extending the service life of the motor and related components;

[0050] (7) Improved dynamic response: The system can quickly respond to changes in rotor position and provide timely adjustments, thereby improving the dynamic response performance of the motor.

[0051] In this embodiment, the control method for starting a wheeled robot specifically includes the following steps:

[0052] S201: Before starting, the wheel driver records the first q-axis voltage given value in the parking mode;

[0053] S202: When starting, the wheel driver switches to the speed mode and obtains the second q-axis voltage given value in the speed mode;

[0054] S203: superimposing the second q-axis voltage given value in the speed mode and the first q-axis voltage given value in the parking mode, and then controlling the speed of the wheel motor through SVPWM;

[0055] S204: When the rotation speed of the wheel motor reaches the target threshold (5% of the rated value), the superposition of the first q-axis voltage given value in the parking mode is stopped, and the speed control loop fully assumes the control task of the wheel motor.

[0056] In the above-mentioned entire starting control method, the design principle of this embodiment is as follows:

[0057] When starting, if the first q-axis voltage set value in parking mode is directly ignored, the wheeled robot will slide down the slope for a moment because the speed control loop that controls the wheel motor speed has not had time to respond in a short period of time. Therefore, the first q-axis voltage set value needs to be retained as an initial value during the starting phase to prevent sliding down the slope.

[0058] When the robot switches from parking mode to starting mode, that is, speed mode, the wheel driver will calculate a new second q-axis voltage given value based on the current speed requirement; when starting, the wheel driver will add the first q-axis voltage given value recorded in the parking mode and the newly calculated second q-axis voltage given value in the speed mode to combine the state of the wheel motor when parking and the demand for the wheel motor speed when starting, thereby obtaining a comprehensive q-axis voltage given value. The superimposed comprehensive q-axis voltage given value will be used to control the wheel motor through SVPWM technology to ensure that the wheel motor can smoothly transition from the parking state to the required speed state when starting.

[0059] When the wheel motor speed reaches the target threshold, it indicates that the wheel motor has successfully started from standstill and is transitioning to normal operation. After the addition of the first q-axis voltage setpoint ceases, control of the wheel motor is fully taken over by the speed control loop; this closed-loop control system adjusts the wheel motor input based on the difference between the actual speed and the set speed to ensure that the motor speed remains stable at the desired setpoint.

[0060] In summary, the parking and starting control method of the present invention, on the one hand, can be implemented only with the hardware of the wheeled robot, without the need for additional auxiliary sensors or parking devices, which greatly reduces the system complexity and cost and improves the system reliability and adaptability; on the other hand, it can quickly switch between parking and moving modes, improving reliability and maneuverability.

Claims

1. A wheeled robot parking and starting control method, characterized in that: The parking control method includes the following steps: S1: Control the wheel motor of the driving wheel to decelerate to zero, obtain the rotor position x of the wheel motor at the moment of deceleration to zero, and switch to parking mode; S2: In parking mode, obtain the rotor position x1 of the wheel motor in real time, calculate the position deviation Δx=x-x1, and obtain the magnitude and direction of the stator magnetic field vector of the wheel motor based on the position deviation; wherein the method for obtaining the magnitude of the stator magnetic field vector of the wheel motor includes: S2-1: The wheel motor's U, V, and W phases are used as input, and the rotor position x1 is used as output. The wheel driver uses the rotor position x as a given parameter and x1 as a feedback parameter to calculate Δx, which is the motor position deviation during parking. S2-2: After the position deviation Δx is proportionally controlled to obtain Kp*Δx, it is limited by limiter S. The absolute value of the limited control signal Kp*Δx is taken as the first q-axis voltage setpoint of the SVPWM. The SVPWM q-axis voltage is used to adjust the torque output by the wheel motor. The SVPWM d-axis voltage is used to adjust the motor magnetic field. The q-axis voltage and d-axis voltage vectors are perpendicular to each other, and the resultant vector of the two is the magnitude of the stator magnetic field vector. S3: Dynamically adjust the magnitude and direction of the stator magnetic field vector in response to the position deviation Δx, so that the rotor of the wheel motor is maintained at position x or in an area adjacent to position x to remain stable.

2. The wheeled robot parking and starting control method according to claim 1, characterized in that: In step S2, the The method for obtaining the stator magnetic field vector direction of the wheel motor includes: S2-3: The position deviation Δx is directly limited by limiter S1, and the limiting threshold is 90°. When Δx is in the range of -90° to 90°, the output value of limiter S1 is Δx. When Δx<-90°, the output value of S1 is -90°. When Δx>90°, the output value of S1 is 90°. The rotor position x1 minus the output value of limiter S1 gives the SVPWM given value θ, where θ is the direction of the stator magnetic field vector.

3. The wheeled robot parking and starting control method according to claim 1, characterized in that: The limiter S The limiting threshold is selected to be 10% to 20% of the rated voltage of the wheel motor; and the d-axis voltage value of the SVPWM is set to 0.

4. The wheeled robot parking and starting control method according to any one of claims 1 to 3, characterized in that: step In S3, the method for dynamically adjusting the size and direction of the stator magnetic field vector includes: calculating the offset of the rotor from position x to position x1 based on the acquired rotor positions x and x1; if the rotor offset is ≤90°, the stator magnetic field vector points to x; if the rotor offset is greater than 90°, the stator magnetic field vector will point to a direction that maintains a 90° angle with the rotor position x1, so as to resist the rotor offset with the maximum torque.

5. The wheeled robot parking and starting control method according to any one of claims 1 to 3, characterized in that: step In S1, when the main controller in the wheeled robot chassis receives the stop signal, it sends a zero-speed command to the wheel driver, and the wheel driver starts to drive the wheel motor to decelerate to zero; at the moment of deceleration to zero, the wheel driver obtains the rotor position x of the wheel motor and switches to parking mode.

6. The wheeled robot parking and starting control method according to any one of claims 1 to 3, characterized in that: Wheeled Machine The control method for the robot start-up includes the following steps: Before starting, obtaining the first q-axis voltage given value in the parking mode; When starting, switch to the speed mode and obtain the second q-axis voltage given value in the speed mode; superimpose the second q-axis voltage given value in the speed mode with the first q-axis voltage given value in the parking mode, and then control the speed of the wheel motor through SVPWM; when the speed of the wheel motor reaches the target threshold, stop superimposing the first q-axis voltage given value in the parking mode, and the speed control loop will fully assume the control task of the wheel motor.

7. The wheeled robot parking and starting control method according to claim 6, characterized in that: The target threshold is 4%~8% of the rated wheel motor speed.

8. The wheeled robot parking and starting control method according to claim 1, characterized in that: In S2, the wheels The driver uses the rotor position x obtained when the wheel motor decelerates to zero as a given parameter, and obtains the rotor position x1 of the wheel motor as feedback in real time. The magnitude and direction of the stator magnetic field vector of the wheel motor are obtained according to the position deviation Δx.

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