Limiting method for multi-stage current of brushless direct current motor

Abstract

The invention relates to the technical field of motor detection, in particular to a brushless DC motor multistage current limiting method, which comprises the following steps: when a brushless DC motor enters a braking deceleration working condition, applying a given voltage to a brushless DC motor end, obtaining characteristic parameters of the brushless DC motor, creating a plurality of braking current intervals based on the characteristic parameters, a current detection module is used for monitoring the reverse braking current of the direct current brushless motor in real time, when the reverse braking current is monitored, a corresponding braking control strategy is executed based on the braking current interval where the reverse braking current is located, and the multiple braking current intervals comprise the braking current interval a, the braking current interval b and the braking current interval c. According to the method, the multiple braking current intervals can be created, corresponding control strategies are executed for different intervals, refined hierarchical control over the reverse braking current of the motor can be achieved, and damage to the motor and an electric control system due to the fact that the current is too large is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of motor detection, and more particularly to a method for limiting multi-stage current of a brushless DC motor. Background Art

[0002] Brushless DC motors are widely used in many fields due to their advantages such as high efficiency and wide speed regulation range. However, during the braking and deceleration process of the motor, there is often a situation where the reverse braking current is too large. The excessive braking current not only affects the service life of the motor, but may also damage the electronic control system, resulting in equipment failures. Existing motor current control methods have certain limitations. Some methods require extremely high current detection accuracy, increasing the R & D cost and system complexity. Some other methods are prone to hardware interference when switching control strategies, resulting in unstable control. And some existing methods have limited application ranges and cannot meet the current control requirements of motors in different application scenarios.

[0003] A similar Chinese patent application with the publication number CN102237838A discloses a braking current control method and device for an electric bicycle controller. The braking current control method for the electric bicycle controller includes: detecting the bus current of the electric bicycle controller in the 180-degree sine wave control mode; when the bus current is less than the first threshold, switching the controller from the double-bridge-arm modulation mode to the single-bridge-arm modulation mode and adjusting the duty ratio of the drive signal; this solution needs to switch the drive mode according to different currents, and problems may occur during the switching process due to hardware interference. Summary of the Invention

[0004] In order to better solve the above problems, the present invention provides a method for limiting multi-stage current of a brushless DC motor, including the following steps: Step 1: When the brushless DC motor enters the braking and deceleration working condition, apply a given voltage to the brushless DC motor terminal; Step 2: Obtain the characteristic parameters of the brushless DC motor, and create multiple braking current intervals based on the characteristic parameters; Step 3: Use a current detection module to continuously monitor the reverse braking current of the brushless DC motor; Step 4: When the reverse braking current is detected, execute a corresponding braking control strategy based on the braking current interval where the reverse braking current is located.

[0005] As a preferred technical solution of the present invention, in step 2, the braking current intervals respectively include: braking current interval a, braking current interval b, and braking current interval c, where braking current interval a represents a low current interval, braking current interval b represents a medium current interval, and braking current interval c represents a high current interval.

[0006] As a preferred technical solution of the present invention, when the current detection module monitors abnormal data, a fault protection mechanism is immediately triggered.

[0007] As a preferred technical solution of the present invention, in step 4, the braking control strategy includes: when it is detected that the reverse braking current is in the braking current interval a, the motor controller dynamically adjusts the output voltage based on the speed loop feedback control mechanism to brake the DC brushless motor.

[0008] As a preferred technical solution of the present invention, the speed loop dynamically adjusts the output voltage of the motor controller based on a closed-loop control principle.

[0009] As a preferred technical solution of the present invention, in step 4, the braking control strategy also includes: when it is detected that the reverse braking current is in the braking current interval b, assigning a value to the integral control link based on the output result of the speed loop, suspending the output function of the speed loop, and gradually reducing the output voltage of the motor controller based on a preset step size.

[0010] As a preferred technical solution of the present invention, in step 4, the braking control strategy also includes: when it is detected that the reverse braking current is in the braking current interval c and is less than or equal to a preset threshold, the output result of the speed loop is transmitted to the integral control link, the speed loop output is stopped, and the current output state of the motor controller is maintained.

[0011] As a preferred technical solution of the present invention, in step 4, the braking control strategy also includes: when it is detected that the reverse braking current is in the braking current interval c and is greater than the preset threshold, increasing the output voltage of the motor controller based on a preset step size to suppress the reverse braking current.

[0012] As a preferred technical solution of the present invention, the preset step size is a predetermined adjustment parameter based on the power, rated current and torque characteristics of the brushless DC motor, and the adjustment parameter is dynamically adjusted based on an adaptive control algorithm.

[0013] As a preferred technical solution of the present invention, after the output result of the speed loop is transmitted to the integral control link, the change process of the DC brushless motor control signal is smoothed based on the integral control link when the speed loop output is stopped.

[0014] Compared with the prior art, the beneficial effects of the present invention are at least as follows: The technical solution of the present invention can achieve refined hierarchical control of the reverse braking current of the motor by creating multiple braking current intervals and executing corresponding control strategies for different intervals, effectively avoiding damage to the motor and the electric control system caused by excessive current. Without high-precision current detection equipment, current limitation is achieved through a reasonable control strategy, reducing the R & D cost and system complexity. The preset step size can be dynamically adjusted according to the motor characteristics and actual application scenarios, making this method applicable to DC brushless motors of different types and operating conditions, with strong versatility and adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to the provided drawings.

[0016] Figure 1 is a flowchart of the steps of the multi-level current limiting method for the DC brushless motor of the present invention; Figure 2 is a schematic diagram of the division of braking current interval a, braking current interval b, and braking current interval c of the present invention; Figure 3 is a flowchart of the braking control strategy corresponding to braking current interval a, braking current interval b, and braking current interval c of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following will further describe the present invention in detail with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] It can be understood that the terms "first", "second", etc. used in the present application can be used in this article to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first xx script can be called the second xx script, and similarly, the second xx script can be called the first xx script.

[0019] In response to the above technical problems, the present invention proposes a method for limiting multi-level current of a DC brushless motor as shown in Figure 1 and the method is implemented through the following steps: Step 1: When the DC brushless motor enters the braking and decelerating working condition, based on the DC brushless motor controller sending a given voltage signal to the motor drive circuit, the drive circuit applies the given voltage to the DC brushless motor terminal based on the power electronic devices, where the given voltage range is 0 - 300V. The motor controller, based on the comprehensive analysis of the real-time operating state of the DC brushless motor (such as the current speed, torque output, etc.), load characteristics (including the size, inertia, change law, etc. of the load), and the desired braking effect (such as braking time, braking smoothness, etc.), uses a pre-designed intelligent algorithm or queries a preset voltage - working condition mapping table to calculate and apply a given voltage suitable for this working condition to the motor terminal.

[0020] It should be noted that the motor controller sends the calculated or queried given voltage signal to the drive circuit of the motor, and the drive circuit applies the voltage to the windings of the DC brushless motor through power electronic devices (such as MOSFET, IGBT, etc.), thereby realizing the braking control of the motor. By changing the electromagnetic torque of the DC brushless motor, the initial regulation of the motor current is realized, ensuring that the DC brushless motor can smoothly and orderly transition from the operating state to the braking state, and avoiding damage to the motor and related electrical equipment caused by the sudden change of current during the braking process.

[0021] The motor controller continuously monitors the real-time operating state of the DC brushless motor, including the current speed, torque output, etc. For example, in the application scenario of an electric vehicle, the motor controller obtains the current speed information of the motor through sensors, such as 3000 revolutions per minute, and the torque magnitude output by the motor at this time, such as 50 N·m.

[0022] The motor controller uses a pre-designed intelligent algorithm, combines the collected real-time operating state, load characteristics, and desired braking effect and other information, and calculates a given voltage suitable for the current working condition. For example, according to the dynamic model and control theory of the motor, a suitable voltage value is obtained through a series of mathematical operations.

[0023] Another way is to query a preset voltage - working condition mapping table. The motor controller looks up the corresponding given voltage in the table according to the current actual situation.

[0024] Step 2: Obtain the characteristic parameters of the DC brushless motor. Based on the characteristic parameters, create multiple braking current intervals. These characteristic parameters include but are not limited to the rated current of the motor, back electromotive force constant, winding resistance, inductance, moment of inertia, and torque - speed characteristic curve, etc. Based on these characteristic parameters, combined with the actual application scenario of the motor (such as load type, braking frequency, requirements for braking smoothness and speed, etc.), use mathematical modeling and data analysis methods to create multiple braking current intervals, where the braking current intervals are braking current interval a, braking current interval b, and braking current interval c.

[0025] As Figure 2 shown, braking current range a, braking current range b, and braking current range c are different reverse braking current ranges precisely defined in advance according to the electrical characteristics, mechanical characteristics of the motor, and actual application requirements. Among them, the braking current range a represents a low current range, the braking current range b represents a medium current range, the braking current range c represents a high current range, and the upper limit value of the braking current range a is less than the lower limit value of the braking current range b, and the upper limit value of the braking current range b is less than the lower limit value of the braking current range c, so as to achieve refined hierarchical control of the current.

[0026] It should be noted that the electrical characteristics include winding resistance, inductance, and back electromotive force constant.

[0027] Among them, the winding resistance is the resistance value of the motor winding itself.

[0028] Inductance is an important electrical parameter of the motor winding.

[0029] The back electromotive force constant represents the proportional relationship between the back electromotive force generated by the motor during rotation and the rotational speed. During the braking process, the back electromotive force of the motor will decrease as the rotational speed decreases.

[0030] The mechanical characteristics include moment of inertia, torque-speed characteristic, and load characteristic.

[0031] Among them, the moment of inertia reflects the ability of the motor rotor to resist changes in the rotational state. The larger the moment of inertia, the greater the inertia that the motor needs to overcome during braking, and the more time and energy required for braking.

[0032] The torque-speed characteristic describes the relationship between the output torque of the motor and the rotational speed. During the braking process, the torque of the motor will change as the rotational speed decreases.

[0033] The load characteristics include the size, inertia, change law, etc. of the load. The size of the load will directly affect the braking torque required by the motor during braking, and thus affect the braking current.

[0034] Taking a certain type of DC brushless motor as an example, its rated current is 10A, the back electromotive force is 0.5V / (rad / s), the winding resistance is 0.2Ω, and the inductance is 0.01H. First, obtain the characteristic parameters of this DC brushless motor, combine the actual scenario of this DC brushless motor applied to an electric bicycle, and considering the requirements for smoothness and comfort during braking of the electric bicycle, use mathematical modeling and data analysis methods to create braking current ranges. After calculation and experimental verification, it is determined that the braking current range a is 1 - 3A, the braking current range b is 3 - 6A, and the braking current range c is above 6A.

[0035] Step 3: Use the current detection module to monitor the reverse braking current of the DC brushless motor in real time. When the monitoring data of the current detection module is abnormal, immediately trigger the fault protection mechanism.

[0036] The current detection module can quickly and accurately collect the current signal of the DC brushless motor and convert it into an electrical signal that can be processed by the motor controller.

[0037] At the same time, filter the collected current signal to remove noise interference and high-frequency harmonic components, thereby improving the reliability and stability of the detection result and ensuring that the current data obtained by the motor controller truly reflects the actual operating state of the motor.

[0038] It should be noted that the protection mechanism stops applying the given voltage to the DC brushless motor terminal, simultaneously sends a warning signal to the operator through the sound and light alarm device, and stores the fault information in the fault record database for subsequent fault analysis and troubleshooting. Step 4: When the reverse braking current is detected, based on the braking current interval where the reverse braking current is located, execute the corresponding braking control strategy.

[0039] As Figure 3 shown, when it is detected that the reverse braking current is in the braking current interval a, the motor controller, based on the speed loop feedback control mechanism, uses the proportional-integral-derivative (PID) control algorithm to dynamically adjust the output voltage according to the deviation between the real-time actual speed of the motor and the preset target speed, so as to achieve smooth and efficient braking of the motor. The speed loop adjustment is based on the closed-loop control principle, and the output voltage of the motor controller is dynamically adjusted through this algorithm to ensure that the motor can quickly and stably reach the braking target.

[0040] When the reverse braking current is in the braking current interval b, transmit the output data of the speed loop to the integral control link, and at the same time pause the output function of the speed loop, and gradually reduce the output voltage of the motor controller in accordance with the preset step size. The preset step size is an adjustment parameter determined in advance by comprehensively considering factors such as the power, rated current and torque characteristics of the motor, as well as the load characteristics and environmental conditions in the actual application scenario. This parameter can be a fixed value or can be dynamically adjusted through an adaptive control algorithm according to the real-time current change situation to achieve precise adjustment of the output voltage of the motor controller.

[0041] When the reverse braking current is in the braking current interval c and less than or equal to the preset threshold, similarly transmit the output result of the speed loop to the integral control link, stop the speed loop output, and maintain the current output state of the motor controller, so as to promote the motor to realize the natural reduction of the current through its own energy consumption.

[0042] When the reverse braking current is within the braking current range c and greater than the preset threshold, increase the drive output of the motor controller in accordance with a preset step size, thereby effectively suppressing the situation of excessive current. The preset step size can be dynamically adjusted according to the actual situation, so as to accurately control the motor current.

[0043] For example, when the DC brushless motor of an electric bicycle enters the braking and decelerating working condition, the motor controller, according to the current operating state and load condition, applies a specific given voltage, such as 12V, to the motor terminal by looking up a preset voltage - working condition mapping table, and starts to brake the motor.

[0044] During the braking process, the current detection module monitors the reverse braking current of the motor in real time.

[0045] If it is detected that the reverse braking current is within the braking current range a (1 - 3A), the motor controller, based on the speed loop feedback control mechanism, uses the PID control algorithm to dynamically adjust the output voltage according to the deviation between the real-time speed of the motor and the preset braking target speed. For example, if the real-time speed of the motor is much higher than the target speed, appropriately increase the output voltage to accelerate the braking speed; if the speed is close to the target speed, then decrease the output voltage to achieve smooth braking.

[0046] When the reverse braking current is within the braking current range b (3 - 6A), transmit the output data of the speed loop to the integral control link, suspend the output of the speed loop, and gradually reduce the output voltage of the motor controller in accordance with a preset step size (such as 0.5V) to control the further increase of the current.

[0047] If the reverse braking current is within the braking current range c (above 6A), transmit the output result of the speed loop to the integral control link, stop the output of the speed loop, maintain the current output state, and let the motor consume energy by itself to reduce the current.

[0048] If the current exceeds the set threshold (such as 8A), then increase the drive output of the motor controller in accordance with a preset step size (such as 1V) to suppress excessive current.

[0049] It should be understood that although the steps in the flowcharts of the embodiments of the present invention are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear indication in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, at least a part of the steps in each embodiment may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same moment, but can be executed at different moments. The execution order of these sub-steps or stages is not necessarily sequential either, but can be executed alternately or in turn with at least a part of other steps or sub-steps or stages of other steps.

[0050] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The above program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, storage, database, or other medium used in the embodiments provided in the present application can include non-volatile and / or volatile memories. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and Rambus dynamic RAM (RDRAM), etc.

[0051] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0052] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for limiting multi - level current of a DC brushless motor, characterized in that, The method comprises the following steps: Step 1: When the brushless DC motor enters a braking and deceleration condition, a given voltage is applied to the brushless DC motor terminal; Step 2: Acquire characteristic parameters of the brushless DC motor, and create multiple braking current intervals based on the characteristic parameters; Step 3: Using a current detection module to monitor the reverse braking current of the brushless DC motor in real time; Step 4: When the reverse braking current is monitored, a corresponding braking control strategy is executed based on the braking current interval in which the reverse braking current is located.

2. The method according to claim 1, characterized in that In step 2, the braking current intervals include: braking current interval a, braking current interval b and braking current interval c, wherein the braking current interval a represents a low current interval, the braking current interval b represents a medium current interval, and the braking current interval c represents a low current interval.

3. The method according to claim 1, characterized in that, When the current detection module monitors abnormal data, a fault protection mechanism is immediately triggered.

4. The method according to claim 2, characterized in that, In step 4, the braking control strategy includes: when it is detected that the reverse braking current is in the braking current interval a, the motor controller dynamically adjusts the output voltage based on a speed loop feedback control mechanism to brake the brushless DC motor.

5. The method according to claim 4, wherein The speed loop dynamically adjusts the output voltage of the motor controller based on a closed-loop control principle.

6. The method according to claim 4, characterized in that, In step 4, the braking control strategy also includes: when it is detected that the reverse braking current is in the braking current interval b, assigning a value to the integral control link based on the output result of the speed loop, suspending the output function of the speed loop, and gradually reducing the output voltage of the motor controller based on a preset step size.

7. The method according to claim 6, wherein In step 4, the braking control strategy also includes: when it is detected that the reverse braking current is in the braking current interval c and is less than or equal to a preset threshold, the output result of the speed loop is transmitted to the integral control link, the speed loop output is stopped, and the current output state of the motor controller is maintained.

8. The method according to claim 7, wherein In step 4, the braking control strategy further includes: when it is detected that the reverse braking current is in the braking current interval c and is greater than the preset threshold, increasing the output voltage of the motor controller based on a preset step size to suppress the reverse braking current.

9. The method according to claim 6, wherein The preset step size is a predetermined adjustment parameter based on the power, rated current and torque characteristics of the brushless DC motor, and the adjustment parameter is adjusted based on an adaptive control algorithm.

10. The method according to claim 6, wherein After the output result of the speed loop is transmitted to the integral control link, the change process of the brushless DC motor control signal is smoothed based on the integral control link when the output of the speed loop is stopped.

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