A method for limiting the multi-stage current of a brushless DC motor

Abstract

This invention relates to the field of motor testing technology, and more specifically to a method for limiting multi-level current in a brushless DC motor. The method includes: when the brushless DC motor enters a braking and deceleration state, applying a given voltage to the motor terminals to obtain characteristic parameters of the motor; creating multiple braking current ranges based on these parameters; using a current detection module to monitor the reverse braking current of the brushless DC motor in real time; and executing a corresponding braking control strategy based on the braking current range in which the reverse braking current is detected. The multiple braking current ranges include braking current range a, braking current range b, and braking current range c. This invention, by creating multiple braking current ranges and executing corresponding control strategies for different ranges, can achieve refined hierarchical control of the motor's reverse braking current, effectively preventing damage to the motor and electronic control system caused by excessive current.

Description

Technical Field

[0001] This invention relates to the field of motor testing technology, and more specifically to a method for limiting the multi-stage current of a brushless DC motor. Background Art

[0002] Brushless DC motors are widely used in many fields due to their high efficiency and wide speed range. However, during motor braking and deceleration, excessive reverse braking current often occurs. Excessive braking current not only affects the motor's lifespan but can also damage the electronic control system, leading to equipment failure. Existing motor current control methods have certain limitations. Some methods require extremely high current detection accuracy, increasing R&D costs and system complexity. Other methods are susceptible to hardware interference when switching control strategies, resulting in unstable control. Furthermore, some existing methods have limited applicability and cannot meet the current control requirements of motors in different application scenarios.

[0003] A similar prior art patent application, 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 a 180-degree sine wave control mode; when the bus current is less than a first threshold, switching the controller from a dual-bridge-arm modulation mode to a single-bridge-arm modulation mode and adjusting the duty cycle of the drive signal. This scheme requires switching the drive mode according to different currents, and the switching process may be affected by hardware interference, leading to problems. Summary of the Invention

[0004] To better address the above problems, this invention provides a method for limiting the multi-stage current of a brushless DC motor, comprising the following steps:

[0005] Step 1: When the brushless DC motor enters the braking and deceleration mode, apply a given voltage to the brushless DC motor terminal;

[0006] Step 2: Obtain the characteristic parameters of the brushless DC motor, and create multiple braking current ranges based on the characteristic parameters;

[0007] Step 3: Use a current detection module to monitor the reverse braking current of the brushless DC motor in real time;

[0008] Step 4: When the reverse braking current is detected, execute the corresponding braking control strategy based on the braking current range in which the reverse braking current is located.

[0009] As a preferred technical solution of the present invention, in step 2, the braking current ranges respectively include: braking current range a, braking current range b and braking current range c, wherein braking current range a represents a low current range, braking current range b represents a medium current range and braking current range c represents a high current range.

[0010] As a preferred embodiment of the present invention, when the current detection module detects abnormal data, a fault protection mechanism is immediately triggered.

[0011] As a preferred technical solution of the present invention, in step 4, the braking control strategy includes: when the reverse braking current is detected to be in the braking current range a, the motor controller dynamically adjusts the output voltage based on the speed loop feedback control mechanism to brake the brushless DC motor.

[0012] As a preferred embodiment of the present invention, the speed loop is based on the closed-loop control principle and dynamically adjusts the output voltage of the motor controller.

[0013] As a preferred technical solution of the present invention, in step 4, the braking control strategy further includes: when the reverse braking current is detected to be in the braking current range b, assigning the output result of the speed loop to the integral control loop, pausing the output function of the speed loop, and gradually reducing the output voltage of the motor controller based on a preset step size.

[0014] As a preferred embodiment of the present invention, in step 4, the braking control strategy further includes: when the reverse braking current is detected to be within the braking current range c and less than or equal to a preset threshold, transmitting the output result of the speed loop to the integral control loop, stopping the speed loop output, and maintaining the current output state of the motor controller.

[0015] As a preferred embodiment of the present invention, in step 4, the braking control strategy further includes: when the reverse braking current is detected to be in the braking current range c and 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.

[0016] As a preferred technical solution of the present invention, the preset step size is an adjustment parameter predetermined 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.

[0017] As a preferred technical solution of the present invention, after transmitting the output result of the speed loop to the integral control loop, the change process of the DC brushless motor control signal is smoothed based on the integral control loop when the output of the speed loop is stopped.

[0018] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0019] The technical solution of this invention creates multiple braking current ranges and executes corresponding control strategies for different ranges, which enables refined hierarchical control of the reverse braking current of the motor. This effectively avoids damage to the motor and electronic control system caused by excessive current. It eliminates the need for high-precision current detection equipment and achieves current limitation through reasonable control strategies, thereby reducing R&D costs 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 different types and operating conditions of brushless DC motors, and possessing strong versatility and adaptability. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 This is a flowchart illustrating the steps of the multi-stage current limiting method for a brushless DC motor according to the present invention.

[0022] Figure 2 This is a schematic diagram showing the division of the braking current interval a, braking current interval b, and braking current interval c according to the present invention.

[0023] Figure 3 This is a flowchart of the braking control strategy corresponding to braking current range a, braking current range b and braking current range c of the present invention. Detailed Implementation

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] It is understood that the terms "first," "second," etc., used in this application may be used herein to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this application, a first script may be referred to as a second script, and similarly, a second script may be referred to as a first script.

[0026] To address the aforementioned technical problems, the present invention proposes the following... Figure 1The method shown is a method for limiting the multi-stage current of a brushless DC motor, which is implemented through the following steps:

[0027] Step 1: When the brushless DC motor enters the braking and deceleration condition, the brushless DC motor controller sends a given voltage signal to the motor drive circuit. The drive circuit applies the given voltage to the brushless DC motor terminal based on power electronic devices. The given voltage range is 0-300V. The motor controller calculates and applies a given voltage suitable for the operating condition to the motor terminal based on a comprehensive analysis of the real-time operating status of the brushless DC motor (such as current speed, torque output, etc.), load characteristics (including load size, inertia, and change patterns), and desired braking effect (such as braking time, braking smoothness, etc.) using a pre-designed intelligent algorithm or by querying a preset voltage-operating condition mapping table.

[0028] It should be noted that the motor controller sends the calculated or queried given voltage signal to the motor drive circuit. The drive circuit applies the voltage to the windings of the brushless DC motor through power electronic devices (such as MOSFETs, IGBTs, etc.), thereby realizing the braking control of the motor. By changing the electromagnetic torque of the brushless DC motor, the motor current is initially regulated to ensure that the brushless DC motor can smoothly and orderly transition from the running state to the braking state, avoiding damage to the motor and related electrical equipment caused by sudden changes in current during braking.

[0029] The motor controller continuously monitors the real-time operating status of the brushless DC motor, including the current speed and torque output. For example, in electric vehicle applications, the motor controller obtains the current speed information of the motor through sensors, such as 3000 rpm, and the magnitude of the torque output by the motor at this time, such as 50 N·m.

[0030] The motor controller uses a pre-designed intelligent algorithm, combined with collected information such as real-time operating status, load characteristics, and desired braking effect, to calculate a given voltage suitable for the current operating conditions. For example, based on the motor's dynamic model and control theory, a suitable voltage value is obtained through a series of mathematical calculations.

[0031] Another method is to consult a preset voltage-condition mapping table. The motor controller looks up the corresponding given voltage in the table based on the current actual situation.

[0032] Step 2: Obtain the characteristic parameters of the brushless DC motor. Based on these parameters, create multiple braking current ranges. These parameters include, but are not limited to, the motor's rated current, back EMF constant, winding resistance, inductance, moment of inertia, and torque-speed characteristic curve. Based on these parameters and the actual application scenario of the motor (such as load type, braking frequency, and requirements for braking smoothness and speed), use mathematical modeling and data analysis methods to create multiple braking current ranges, namely braking current range a, braking current range b, and braking current range c.

[0033] like Figure 2 As shown, braking current ranges a, b, and c are pre-defined, precisely defined reverse braking current ranges based on the motor's electrical and mechanical characteristics and actual application requirements. Braking current range a represents a low current range, braking current range b represents a medium current range, and braking current range c represents a high current range. The upper limit of braking current range a is less than the lower limit of braking current range b, and the upper limit of braking current range b is less than the lower limit of braking current range c, thereby achieving refined hierarchical control of the current.

[0034] It should be noted that electrical characteristics include winding resistance, inductance, and back electromotive force constant.

[0035] Among them, the winding resistance is the resistance value of the motor winding itself.

[0036] Inductance is an important electrical parameter of motor windings.

[0037] The back electromotive force constant represents the proportional relationship between the back electromotive force generated by a motor during rotation and its rotational speed. During braking, the back electromotive force of the motor decreases as the rotational speed decreases.

[0038] Mechanical characteristics include moment of inertia, torque-speed characteristics, and load characteristics.

[0039] Moment of inertia reflects the ability of a motor rotor to resist changes in its rotational state. The greater the moment of inertia, the greater the inertia the motor needs to overcome during braking, and the more time and energy are required for braking.

[0040] The torque-speed characteristic describes the relationship between the motor's output torque and its speed. During braking, the motor's torque changes as the speed decreases.

[0041] Load characteristics include load size, inertia, and variation patterns. The load size directly affects the braking torque required by the motor during braking, and thus the braking current.

[0042] Taking a certain type of brushless DC motor as an example, its rated current is 10A, back electromotive force is 0.5V / (rad / s), winding resistance is 0.2Ω, and inductance is 0.01H. First, the characteristic parameters of the brushless DC motor are obtained. Considering the actual scenario of the brushless DC motor being used in electric bicycles, and taking into account the requirements for smoothness and comfort when the electric bicycle is braking, mathematical modeling and data analysis methods are used to create braking current ranges. After calculation and experimental verification, it is determined that braking current range a is 1-3A, braking current range b is 3-6A, and braking current range c is above 6A.

[0043] Step 3: Use a current detection module to monitor the reverse braking current of the brushless DC motor in real time. When the data monitored by the current detection module is abnormal, the fault protection mechanism is immediately triggered.

[0044] The current detection module can quickly and accurately acquire the current signal of the brushless DC motor and convert it into an electrical signal that can be processed by the motor controller.

[0045] Meanwhile, the acquired current signal is filtered to remove noise interference and high-frequency harmonic components, thereby improving the reliability and stability of the detection results and ensuring that the current data obtained by the motor controller truly reflects the actual operating status of the motor.

[0046] It should be noted that the protection mechanism involves stopping the application of a given voltage to the brushless DC motor, simultaneously issuing a warning signal to the operator via an audible and visual alarm, and storing the fault information in a fault record database for subsequent fault analysis and troubleshooting.

[0047] Step 4: When a reverse braking current is detected, execute the corresponding braking control strategy based on the braking current range in which the reverse braking current is located.

[0048] like Figure 3 As shown, when the reverse braking current is detected to be within the braking current range 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. 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.

[0049] When the reverse braking current is within the braking current range b, the output data of the speed loop is transmitted to the integral control loop. At the same time, the output function of the speed loop is paused, and the output voltage of the motor controller is gradually reduced according to a preset step size. The preset step size is an adjustment parameter that is determined in advance by comprehensively considering 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 according to the real-time current changes through an adaptive control algorithm to achieve precise adjustment of the output voltage of the motor controller.

[0050] When the reverse braking current is within the braking current range c and is less than or equal to the preset threshold, the output result of the speed loop is also transmitted to the integral control loop, the speed loop output is stopped, the current output state of the motor controller is maintained, and the motor is prompted to reduce the current naturally through its own energy consumption.

[0051] When the reverse braking current is within the braking current range c and exceeds the preset threshold, the drive output of the motor controller is increased according to the preset step size, thereby effectively suppressing the excessive current. The preset step size can be dynamically adjusted according to the actual situation, thus enabling precise control of the motor current.

[0052] For example, when the DC brushless motor of an electric bicycle enters the braking and deceleration mode, the motor controller applies a specific given voltage, such as 12V, to the motor terminal by looking up a preset voltage-condition mapping table based on the current operating status and load conditions, and begins to brake the motor.

[0053] During braking, the current detection module monitors the reverse braking current of the motor in real time.

[0054] If a reverse braking current is detected within the braking current range a (1-3A), the motor controller, based on the speed loop feedback control mechanism and using a PID control algorithm, dynamically adjusts the output voltage according to the deviation between the motor's real-time speed and the preset braking target speed. For example, if the motor's real-time speed is significantly higher than the target speed, the output voltage is appropriately increased to accelerate the braking speed; if the speed is close to the target speed, the output voltage is decreased to achieve smooth braking.

[0055] When the reverse braking current is in the braking current range b (3-6A), the output data of the speed loop is transmitted to the integral control loop, the speed loop output is paused, and the output voltage of the motor controller is gradually reduced according to a preset step size (such as 0.5V) to control the current to increase further.

[0056] If the reverse braking current is within the braking current range c (above 6A), the speed loop output result is transmitted to the integral control loop, the speed loop output is stopped, the current output state is maintained, and the motor consumes energy to reduce the current.

[0057] If the current exceeds the set threshold (e.g., 8A), the drive output of the motor controller will be increased by a preset step size (e.g., 1V) to suppress excessive current.

[0058] It should be understood that although the steps in the flowcharts of the various embodiments of the present invention are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the various embodiments may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least a portion of the sub-steps or stages of other steps.

[0059] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may 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), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0060] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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, they should be considered to be within the scope of this specification.

[0061] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for limiting the multi-stage current of a brushless DC motor, characterized in that, The method includes the following steps: Step 1: When the brushless DC motor enters the braking and deceleration mode, 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 ranges based on the characteristic parameters; The braking current ranges include braking current range a, braking current range b, and braking current range c, wherein braking current range a represents a low current range, braking current range b represents a medium current range, and braking current range c represents a high current range. Step 3: Use 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 detected, execute the corresponding braking control strategy based on the braking current range in which the reverse braking current is located; The braking control strategy includes: when the reverse braking current is detected to be in the braking current range a, the motor controller dynamically adjusts the output voltage based on the speed loop feedback control mechanism to brake the brushless DC motor. When the reverse braking current is detected to be within the braking current range b, the output result of the speed loop is assigned to the integral control loop, the output function of the speed loop is paused, and the output voltage of the motor controller is gradually reduced based on a preset step size. The braking control strategy further includes: when the reverse braking current is detected to be within the braking current range c and less than or equal to a preset threshold, the output result of the speed loop is transmitted to the integral control loop, the speed loop output is stopped, and the current output state of the motor controller is maintained; The braking control strategy further includes: when the reverse braking current is detected to be in the braking current range c and 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.

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

3. The method according to claim 1, characterized in that, The speed loop is based on the closed-loop control principle and dynamically adjusts the output voltage of the motor controller.

4. The method according to claim 1, characterized in that, The preset step size is an adjustment parameter determined in advance based on the power, rated current and torque characteristics of the brushless DC motor. The adjustment parameter is adjusted based on an adaptive control algorithm.

5. The method according to claim 1, characterized in that, After transmitting the output of the speed loop to the integral control loop, the change process of the DC brushless motor control signal is smoothed based on the integral control loop when the speed loop output is stopped.

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