Wheeled robot parking and starting control method

Abstract

A wheeled robot parking and starting control method includes the following steps that S1, a wheel motor of a driving wheel is controlled to decelerate to zero, the rotor position x of the wheel motor is obtained at the moment that the wheel motor decelerates to zero, and a parking mode is switched; s2, in the parking mode, the rotor position x1 of the wheel motor is obtained in real time, the position deviation delta x = x-x1 is calculated, and the size and direction of a stator magnetic field vector of the wheel motor are obtained according to the position deviation; and S3, dynamically adjusting the size and direction of the stator magnetic field vector so as to respond to the position deviation delta x, and enabling the rotor of the wheel motor to be maintained at the position x or the adjacent area of the position x to be kept stable. The system complexity and cost are greatly reduced, the parking mode and the moving mode can be rapidly switched, and the reliability and maneuverability are improved.

Description

Technical Field

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

[0002] Wheeled robots (usually including two-wheel, four-wheel, six-wheel and other configurations) generally work in speed control mode. When the given command is zero speed, the drive wheels will stop rotating. Since the wheeled robot is moving, the start-stop control will affect its reliability and maneuverability. Specifically, it needs to prevent slipping when starting and parking, and respond quickly to movement commands.

[0003] CN 117842896A discloses a method and device for automatically releasing parking control of a counterbalanced forklift AGV and a counterbalanced forklift, and the technical scheme thereof comprises: 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; when the pulling torque reaches a set value, controlling the push rod motor to stop and lock; when the push rod motor stops and locks, a brake device performs a braking action.

[0004] CN 118322194A discloses a robot parking control method, device, system and robot. The robot parking control method comprises: obtaining the parking state of the robot and the switch state of the robot's legs; if the parking state is that parking is allowed and the switch state meets the preset conditions, controlling the robot to park and controlling the parking time of the robot; 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 object 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 which has 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 according to 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] Further, in step S2, the method for obtaining the magnitude of the stator magnetic field vector of the wheel motor includes:

[0012] S2-1: The U, V, and W phases of the wheel motor 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, and calculates Δx as the motor position deviation during parking;

[0013] S2-2: After the position deviation Δx is obtained by proportional control to obtain Kp*Δx, it is limited by the limiter S, and the absolute value of the limited control signal Kp*Δx is taken as the first q-axis voltage given 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 synthetic vector of the two is the size of the stator magnetic field vector.

[0014] Further, 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 the limiter S1, and the limiting threshold is 90°; when Δx is in the range of -90° to 90°, the output value of the 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 the limiter S1 to obtain 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 offset of the rotor is ≤90°, the stator magnetic field vector points to x; if the offset of the rotor is greater than 90°, the stator magnetic field vector will point to a direction that maintains an angle of 90° with the rotor position x1, so as to resist the rotor offset with the maximum torque.

[0018] Further, 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 under the speed mode; superimpose the second q-axis voltage given value under the speed mode with the first q-axis voltage given value under 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 under 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] Further, in S2, the wheel driver takes the rotor position x obtained when the wheel motor decelerates to zero as a given parameter, obtains the rotor position x1 of the wheel motor in real time as feedback, 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 as follows: on the one hand, it can be realized with only the hardware of a 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 working flow chart of the parking control method according to an embodiment of the present invention;

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

[0027] Figure 3 It 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 1As shown: A parking and starting control method for 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 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 the parking mode. The main controller of the wheeled robot is referred to as 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 the 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, and 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 the parking mode is as follows: Figure 2 As shown in the figure (except for the wheel motor, all parts are implemented in the wheel driver). Specifically:

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

[0035] A. The U, V, and W phases of the wheel motor 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, and calculates Δx as the motor position deviation during parking.

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

[0037] C. The position deviation Δx is also limited by the limiter S1, and the limiting threshold is 90°; when Δx is in the range of -90° to 90°, the output value of 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 the limiter S1 to obtain the SVPWM given value θ, 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) The system design is simplified, no additional sensors or parking devices are required, and the system complexity and cost are reduced; (2) Because the 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 motors and drive configurations, with better flexibility; (4) By accurately controlling the magnitude and direction of the stator magnetic field vector, the motor torque is accurately 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 has the following characteristics: the action of the stator magnetic field vector and the rotor magnetic field vector will generate torque. When the vector amplitude is constant, the maximum torque will be obtained when the angle between the two is 90°; when the angle is constant, the greater the vector amplitude, the greater the torque.

[0041] In this embodiment, the wheel drive is realized by using Figure 2The modulation method in the figure obtains the stator magnetic field vector applied to the wheel motor. The magnitude and direction of the 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), so that the wheel motor generates a torque to resist the change of Δx, and finally tries to keep the motor rotor near the 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 magnitude of the stator magnetic field vector also increases, still pointing in the x direction, that is, Figure 3 As shown in (b), (c), (d), (g), (h) and (i) in FIG, 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 FIG. Figure 3 As shown in (e) and (f).

[0043] It can be said that in this embodiment, the stator magnetic field vector interacts with the rotor magnetic field vector generated by the permanent magnet to resist the change of the position deviation Δx, so that the motor rotor is maintained in a state close to the position x. When the rotor offset is small, a smaller stator magnetic field vector is generated, pointing to the initial position x; as the offset increases, the amplitude of the stator magnetic field vector increases, still pointing to the x direction; and when the offset exceeds 90°, the stator magnetic field vector maintains a 90° angle with x1 to provide maximum torque to resist the 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 is able to 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 the stable position of the rotor under various conditions. By precisely controlling the magnetic field vector, the system can provide appropriate torque when needed and avoid 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 a speed mode and obtains a second q-axis voltage given value in the speed mode;

[0054] S203: superimposing 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 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:

[0057] When starting, if the first q-axis voltage given value in the 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 in a short period of time has no time to respond. Therefore, the first q-axis voltage given value needs to be retained as an initial value during the starting stage 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 adds the first q-axis voltage given value recorded in the parking mode to the second q-axis voltage given value newly calculated in the speed mode, so as 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 means that the wheel motor has started successfully from a stationary state and is transitioning to a normal operating state. After stopping superimposing the first q-axis voltage set value, the control of the wheel motor will be completely taken over by the speed control loop; the speed control loop is a closed-loop control system that adjusts the input of the wheel motor according to the difference between the actual speed and the set speed to ensure that the motor speed can be stabilized at the required set value.

[0060] To sum up, the parking and starting control method of the present invention, on the one hand, only requires the hardware of the wheeled robot to be implemented, and does not require the additional setting of 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 to improve 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, 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; 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 method for obtaining the magnitude of the stator magnetic field vector of the wheel motor includes: S2-1: The U, V, and W phases of the wheel motor 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, and calculates Δx as the motor position deviation during parking; S2-2: After the position deviation Δx is obtained by proportional control to obtain Kp*Δx, it is limited by the limiter S, and the absolute value of the limited control signal Kp*Δx is taken as the first q-axis voltage given 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 synthetic vector of the two is the size of the stator magnetic field vector.

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

4. The wheeled robot parking and starting control method according to claim 2, characterized in that: The limiting threshold of the limiter S is selected to be 10% to 20% of the rated voltage of the wheel motor; the d-axis voltage value of the SVPWM is set to 0.

5. The wheeled robot parking and starting control method according to any one of claims 1 to 4, characterized in that: 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 >90°, the stator magnetic field vector will point to a direction that maintains an angle of 90° with the rotor position x1, so as to resist the rotor offset with the maximum torque.

6. The wheeled robot parking and starting control method according to any one of claims 1 to 4, characterized in that: 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.

7. The wheeled robot parking and starting control method according to any one of claims 2 to 4, characterized in that: The control method for starting a wheeled robot comprises 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 under the speed mode; superimpose the second q-axis voltage given value under the speed mode with the first q-axis voltage given value under 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 under the parking mode, and the speed control loop will fully assume the control task of the wheel motor.

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

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

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