Apparatus and method for controlling BLDC motor

Abstract

A method and an apparatus for controlling a brushless direct current (BLDC) motor are provided that enable smooth transition between low-speed open-loop control and high-speed closed-loop control. The device integrates modules for driving, viewing and transitioning between open-loop and closed-loop IB (current and back electromotive force) angles. Weighted averaging of the IB angle ensures that the motor performance is stable during transition, and torque impact, current spikes and noise are reduced to the maximum extent. The device also has a current and voltage regulation function, and can maintain accurate motor speed under different conditions. The weighting factor is dynamically adjusted based on the motor speed and the signal-to-noise ratio, and the control stability is further enhanced. The system improves motor efficiency in motor drive, reduces the risk of stall, and optimizes performance across a wide range of operating speeds.

Description

Technical Field

[0001] This invention relates to the field of brushless direct current (BLDC) motors. More specifically, this invention relates to a driver and method for controlling such BLDC motors. Background Technology

[0002] Operating many BLDC motors sensorlessly at low speeds using closed-loop control (such as field-oriented control, FOC) remains a significant challenge. Therefore, open-loop control (with or without current regulation) is common practice at these low speeds. While slightly less efficient, open-loop control provides a more sinusoidal current waveform, resulting in better acoustic performance and a reduced risk of motor stall.

[0003] However, as motor speeds increase, closed-loop control algorithms such as FOC become preferred due to their enhanced efficiency and stability. This necessitates a transition from open-loop to closed-loop control at some point during operation.

[0004] Traditionally, this transition has been performed instantaneously. Voltage angle and amplitude, along with current usage and open-loop speed, are used to initialize the initial state of the closed-loop algorithm and the proportional-integral-derivative (PID) integral. Even with perfect initialization, significant errors often occur in the first iteration of the closed-loop algorithm, triggering an immediate and often aggressive response due to the controller's proportional gain. This response leads to torque spurs and current spikes, resulting in audible noise and increasing the risk of motor stall.

[0005] In existing controllers, these disturbances during transition can cause torque surges that are visible in the phase current and generate audible noise. Additionally, these disturbances can cause oscillations within the motor controller, leading to an increased risk of slower acceleration and stall.

[0006] The risk of stalling is even greater when transitioning from closed-loop control back to open-loop control. After the transition, the open-loop controller may not be able to effectively handle any instabilities introduced during the process.

[0007] Therefore, there is a need for methods and systems for controlling BLDC motors that allow for smooth transitions when increasing or decreasing the motor speed. Summary of the Invention

[0008] The purpose of embodiments of the present invention is to provide a good method and apparatus for controlling a BLDC motor.

[0009] The above objectives are achieved by the method and apparatus according to the present invention.

[0010] In a first aspect, embodiments of the present invention relate to an apparatus for controlling a BLDC motor, comprising: a drive module configured to apply a voltage to the motor to drive the motor; an observer module configured to obtain a closed-loop IB angle between a measured current angle and a closed-loop back electromotive force (BEMF) angle, wherein the BEMF angle is obtained based on the applied voltage; an open-loop angle module configured to obtain an open-loop IB angle between the measured current angle and the open-loop BEMF angle, wherein the open-loop BEMF angle is calculated based on a desired open-loop control curve; an angle transformation module configured to calculate a weighted average IB angle based on the closed-loop IB angle and the open-loop IB angle; and an angle control module configured to determine a voltage angle to be applied to the motor based on the weighted average IB angle.

[0011] In embodiments of the invention, the desired open-loop control curve may be an open-loop velocity curve defining a desired velocity that varies with time. However, the invention is not limited thereto. A desired angle or acceleration may also vary with time. In embodiments of the invention, the desired angle may increase or decrease with time, for example, linearly, quadratically, or in any desired manner.

[0012] When transitioning from open-loop to closed-loop, the open-loop IB angle is initialized based on the applied voltage and the measured current angle (I angle).

[0013] When transitioning from closed-loop to open-loop, the closed-loop IB angle is initialized based on the observer IB angle and I angle.

[0014] The advantage of embodiments of the present invention lies in facilitating a smooth transition between open-loop and closed-loop control modes. This minimizes torque surges, current spikes, and noise during the transition, thereby improving overall motor performance.

[0015] The advantage of embodiments of the present invention lies in the ability to switch between open-loop control at lower speeds and closed-loop control at higher speeds, enabling more efficient motor operation across a wide range of operating conditions. This dual-mode control optimizes energy use and enhances motor performance across various speed ranges.

[0016] The advantage of embodiments of the present invention is that, by mixing the IB angles from both the open-loop and closed-loop control systems in the angle conversion module, the device reduces the risk of motor stall, especially during critical transitions. This ensures a more stable control process and avoids sudden changes that could interrupt motor operation.

[0017] Furthermore, in embodiments of the present invention, the device may include a current-speed control module configured to control the motor speed by generating a closed-loop target current amplitude based on a speed error; a current amplitude conversion module configured to calculate a weighted average between the closed-loop target current amplitude and the open-loop target current amplitude to obtain a target peak current; and a current amplitude control module configured to generate a peak voltage to be applied to the motor based on the target peak current and the measured current amplitude.

[0018] An advantage of embodiments of the invention is enhanced speed control through current regulation. This is particularly advantageous in systems where speed must be maintained precisely despite load variations. Another advantage of embodiments of the invention is the smooth transition between the open-loop and closed-loop target current amplitudes.

[0019] Furthermore, in an alternative embodiment of the invention, the device may include a voltage-speed control module configured to control the motor speed by generating a closed-loop target voltage amplitude based on a speed error; a voltage amplitude control module configured to generate an open-loop voltage amplitude from an open-loop current amplitude and from a measured current amplitude; and a voltage amplitude conversion module configured to calculate a weighted average between the open-loop voltage amplitude and the target voltage amplitude generated by the voltage-speed control module to obtain a peak voltage to be applied to the motor.

[0020] An advantage of embodiments of the present invention is that a smooth transition between open-loop and closed-loop voltage amplitudes is achieved.

[0021] In an embodiment of the invention, the angle conversion module is configured to calculate the weighted average IB angle using a weighting factor and to dynamically adjust the weighting factor based on the motor speed.

[0022] An advantage of embodiments of the present invention is that it enables a smooth transition between open-loop and closed-loop control.

[0023] In an embodiment of the invention, the angle transformation module is configured to linearly change the weighting factor such that the open-loop IB angle receives a lower weight when transitioning from closed-loop to open-loop and a higher weight when transitioning from open-loop to closed-loop.

[0024] In embodiments of the invention, the angle conversion module is configured to calculate weights based on motor speed or the signal-to-noise ratio of the measured back electromotive force.

[0025] In an embodiment of the present invention, the angle conversion module is configured to: initiate a transition from open-loop to closed-loop when the motor speed exceeds a first predefined speed threshold or when the signal-to-noise ratio of the measured back electromotive force exceeds a first predefined signal-to-noise ratio threshold, and initiate a transition from closed-loop to open-loop when the motor speed becomes less than a second predefined speed threshold or when the signal-to-noise ratio of the measured back electromotive force becomes less than a second predefined signal-to-noise ratio threshold.

[0026] In an embodiment of the present invention, when the angle transition module resets at the beginning of the transition from open loop to closed loop, the angle control module uses the open loop angle from the open loop angle module as the voltage angle.

[0027] In an embodiment of the invention, the current amplitude conversion module is configured to calculate the target peak current using a weighting factor and to dynamically adjust the weighting factor based on the motor speed.

[0028] In an embodiment of the invention, the voltage amplitude conversion module is configured to calculate the peak voltage using a weighting factor and to dynamically adjust the weighting factor based on the motor speed.

[0029] In a second aspect, embodiments of the present invention relate to a method for controlling a brushless DC motor. The method includes:

[0030] - Drive the motor by applying voltage to it;

[0031] - Obtain the closed-loop IB angle between the measured current angle and the closed-loop BEMF angle, which is based on the applied voltage;

[0032] - Obtain the open-loop IB angle between the measured current angle and the open-loop BEMF angle, where the open-loop BEMF angle is calculated based on the desired open-loop control curve;

[0033] - Calculate the weighted average IB angle based on the closed-loop IB angle and the open-loop IB angle;

[0034] - The voltage angle that must be applied to the motor is determined based on the weighted average IB angle.

[0035] In embodiments of the present invention, the method further includes

[0036] - Generate the closed-loop target current amplitude based on the velocity error and obtain the open-loop target current amplitude;

[0037] - Calculate the weighted average between the closed-loop target current amplitude and the open-loop target current amplitude to obtain the target peak current;

[0038] - Generate the peak voltage to be applied to the motor based on the target peak current and the measured current amplitude.

[0039] In embodiments of the present invention, the method further includes

[0040] - Generate closed-loop target voltage amplitude based on velocity error;

[0041] - Generate the open-loop voltage amplitude based on the open-loop current amplitude and the measured current amplitude;

[0042] - Calculate the weighted average between the open-loop voltage amplitude and the generated target voltage amplitude to obtain the peak voltage to be applied to the motor.

[0043] In an embodiment of the invention, the calculation of the weighted average IB angle includes using a weighting factor and dynamically adjusting the weighting factor based on the motor speed.

[0044] In an embodiment of the present invention, the calculation of the weighted average IB angle includes linearly changing the weighting factor so that the open-loop IB angle receives a lower weight when transitioning from closed-loop to open-loop and a higher weight when transitioning from open-loop to closed-loop.

[0045] Specific and preferred aspects of the invention are set forth in the appended independent and dependent claims. Features from the dependent claims may be suitably combined with features of the independent claims and other dependent claims, and not merely as expressly set forth in the claims.

[0046] These and other aspects of the invention will be apparent from the following description of one or more embodiments, and are illustrated by reference to the following description of one or more embodiments. Attached Figure Description

[0047] Figure 1 A schematic diagram of a device for controlling a BLDC motor and current amplitude control according to an embodiment of the present invention is shown.

[0048] Figure 2 A schematic diagram of a device for controlling a BLDC motor using DC voltage amplitude control according to an embodiment of the present invention is shown.

[0049] Figure 3 A detailed schematic diagram of an exemplary device for controlling a BLDC motor and controlling current amplitude according to an embodiment of the present invention is shown.

[0050] Figure 4 A detailed schematic diagram of an exemplary device for controlling a BLDC motor using DC voltage amplitude control according to an embodiment of the present invention is shown.

[0051] Figure 5Flowcharts illustrating different possible methods according to embodiments of the present invention are shown.

[0052] Figure 6 The phase current transition from open-loop to closed-loop is illustrated according to an embodiment of the present invention.

[0053] Figure 7 The phase current transition from closed-loop to open-loop is illustrated according to an embodiment of the present invention.

[0054] Figure 8 An oscilloscope screen image showing the open-loop to closed-loop transition PWM signal and phase current obtained when a fan with a non-sinusoidal BEMF is controlled using a device or method according to an embodiment of the present invention.

[0055] Figure 9 An oscilloscope screen image showing the closed-loop to open-loop transition of the PWM signal and current signal obtained when controlling a fan with a non-sinusoidal BEMF using a device or method according to an embodiment of the present invention.

[0056] Figure 10 An oscilloscope screen image showing the open-loop to closed-loop transition of PWM and current signals obtained when controlling an unloaded 3-phase gearbox motor using a device or method according to an embodiment of the present invention.

[0057] Figure 11 An oscilloscope screen image showing the open-loop to closed-loop transition PWM signal and current signal obtained when controlling a three-phase gearbox motor with a load using a device or method according to an embodiment of the present invention.

[0058] Figure 12 An oscilloscope screen image showing the closed-loop to open-loop transition of the PWM signal and current signal obtained when controlling an unloaded 3-phase gearbox motor using a device or method according to an embodiment of the present invention.

[0059] Figure 13 An oscilloscope screen image showing the closed-loop to open-loop transition of the PWM signal and current signal obtained when controlling a three-phase gearbox motor with a load using a device or method according to an embodiment of the present invention.

[0060] Figure 14 An oscilloscope screen image showing the open-loop to closed-loop transition of PWM and current signals obtained when a device or method according to an embodiment of the present invention is used to control a 4-phase bipolar stepper with a gearbox.

[0061] Figure 15 An oscilloscope screen image showing the closed-loop to open-loop transition of the PWM signal and current signal obtained when a device or method according to an embodiment of the present invention is used to control a 4-phase bipolar stepper with a gearbox.

[0062] Any reference numerals in the claims should not be construed as limiting the scope.

[0063] In different accompanying drawings, the same reference numerals refer to the same or similar elements. Detailed Implementation

[0064] The invention will be described with reference to specific embodiments and particular drawings, but the invention is not limited thereto but is defined only by the claims. The described drawings are merely illustrative and not restrictive. In the drawings, some elements may be enlarged and not drawn to scale for illustrative purposes. Dimensions and relative dimensions do not correspond to an actual reduction in scale for the practice of the invention.

[0065] The terms "first," "second," etc., used in the specification and claims are used to distinguish between similar elements and are not necessarily used to describe a temporal, spatial, hierarchical, or any other order. It should be understood that the terms thus used are interchangeable where appropriate, and the embodiments of the invention described herein can operate in an order different from that described or illustrated herein.

[0066] It should be noted that the term "comprising" as used in the claims should not be construed as limiting itself to the means listed thereafter; it does not exclude other elements or steps. Therefore, the term should be interpreted as specifying the presence of the features, integers, steps, or components stated as mentioned, but does not exclude the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the scope of the statement "an apparatus comprising means A and B" should not be limited to an apparatus consisting solely of components A and B. This means that for the present invention, the only relevant components of the apparatus are A and B.

[0067] Throughout this specification, the reference to "an embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the phrase "in one embodiment" or "in an embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, but may refer to the same embodiment. Furthermore, in one or more embodiments, as will be apparent to those skilled in the art from this disclosure, particular features, structures, or characteristics may be combined in any suitable manner.

[0068] Similarly, it should be understood that in the description of exemplary embodiments of the invention, for the purpose of simplification and aiding in the understanding of one or more of the various inventive aspects, features of the invention are sometimes grouped together in a single embodiment, drawing, or description thereof. However, this method of disclosure should not be construed as reflecting an intention to claim more features than are expressly recited in each claim. Rather, as reflected in the appended claims, the inventive aspect lies in fewer features than all the features of a single foregoing disclosed embodiment. Thus, the claims appended to the Detailed Description are thereby explicitly incorporated into this Detailed Description, wherein each claim itself represents a separate embodiment of the invention.

[0069] Furthermore, while some embodiments described herein include features that are included in other embodiments but not others, it will be understood by those skilled in the art that combinations of features from different embodiments are intended to fall within the scope of the invention and form different embodiments. For example, any embodiment of the claimed embodiments in the appended claims may be used in any combination.

[0070] Numerous specific details are set forth in the description provided herein. However, it should be understood that embodiments of the invention can be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0071] In embodiments of the invention, when referring to the open-loop IB angle, it means the angle between the measured current angle and the BEMF angle, where the BEMF angle is calculated based on a desired open-loop control curve (such as an open-loop velocity curve). Other open-loop control curves, such as desired angles or accelerations varying over time, may also be used.

[0072] In embodiments of the present invention, when referring to the closed-loop IB angle, it refers to the angle between the measured current angle and the closed-loop BEMF angle, wherein the closed-loop BEMF angle is based on the applied voltage.

[0073] This invention discloses an apparatus and method for smoothly driving a BLDC motor. Open-loop control is proposed for low speeds, while closed-loop control is proposed for high speeds (compared to the low speeds of open-loop control). This disclosure describes a method for smoothly transitioning a BLDC motor between open-loop and closed-loop control, or between closed-loop and open-loop control. The closed-loop control algorithm can be, for example, an FOC algorithm. Therefore, an advantage of embodiments of the invention is that current spikes are avoided during transitions, resulting in smooth transitions with good stability and no additional acoustics.

[0074] In the method or apparatus according to embodiments of the present invention, the open-loop algorithm and the closed-loop algorithm operate in parallel during the transition, and a weighted average of the open-loop IB angle and the closed-loop IB angle is taken. The transition from open-loop to closed-loop can begin after a first predefined speed threshold has been reached or the measurement noise has become sufficiently small (e.g., a sufficiently high BEMF is obtained) and therefore a first predefined signal-to-noise ratio has been reached. The transition from closed-loop to open-loop can begin when the motor speed becomes less than a second predefined speed threshold or when the measurement noise becomes less than the second predefined signal-to-noise ratio that has been reached.

[0075] In a first aspect, embodiments of the present invention relate to a device 100 for controlling a brushless DC motor 200. A schematic diagram of such a device is shown in… Figures 1 to 4 The BLDC motor 200 is a multiphase motor that includes two or more phases or three or more phases.

[0076] The device 100 includes a drive module 150 configured to apply voltage to the motor 200 to drive the motor 200.

[0077] Furthermore, the device includes an observer module 110 configured to obtain a closed-loop IB angle between the measured current angle and the closed-loop BEMF angle based on the applied voltage. In an embodiment of the invention, the observer module is configured to obtain the closed-loop IB angle between the measured current angle and the closed-loop BEMF angle based on the applied voltage and the measured current.

[0078] Furthermore, the device includes an open-loop angle module 120 configured to obtain the open-loop IB angle between the measured current angle and the open-loop BEMF angle. The open-loop BEMF angle is calculated based on the desired open-loop control curve.

[0079] In addition, the device includes an angle transformation module 130, which is configured to calculate a weighted average IB angle based on the closed-loop IB angle and the open-loop IB angle.

[0080] In addition, the device includes an angle control module 140, which is configured to determine the voltage angle to be applied to the motor based on the weighted average IB angle.

[0081] By running both algorithms (open-loop and closed-loop) in parallel and taking a weighted average of their outputs, it is ensured that no abrupt transition effects are introduced, resulting in a smoother transition than the abrupt transition effects in existing technologies.

[0082] In embodiments of the invention, IB control is used to control the motor, which means (e.g., using a FOC controller) controlling the closed-loop angle between the current and the BEMF vector. Compared to using I... d / I q Compared to control algorithms, this has the advantage of requiring far less CPU computing power because the observer is much simpler and does not require forward / inverse Park transformations.

[0083] In embodiments of the present invention (examples thereof are given below) Figure 1 and Figure 3 (As shown in the figure), the control of the BLDC motor includes current amplitude control. Therefore, the device includes a current speed control module 161, which is configured to control the motor speed by generating a closed-loop target current amplitude based on the speed error.

[0084] In an embodiment of the present invention, the device includes a current amplitude conversion module 171 configured to calculate a weighted average between the closed-loop target current amplitude and the open-loop target current amplitude to obtain a target peak current.

[0085] In an embodiment of the invention, the device includes a current amplitude control module 181 configured to generate a peak voltage from a target peak current and from a measured current amplitude to be applied to a motor.

[0086] Figure 3 The detailed block diagram of the controller according to an embodiment of the present invention illustrated herein includes the following building blocks.

[0087] Drive module 150 is configured to apply voltage to motor 200. In this example, the drive module includes a lookup table (LUT). The lookup table uses voltage angles to receive three-phase equivalent values ​​of the voltage angles. These equivalent values ​​are scaled based on voltage amplitude values ​​(also known as voltage peaks). The resulting three voltages are applied (typically as PWM signals on the motor phases). In this exemplary embodiment of the invention, phase currents are measured simultaneously with the application of phase currents (typically only two currents are measured and one current is calculated).

[0088] In this exemplary embodiment of the invention, device 100 includes a Clarke transformation module 190 for applying a Clarke transformation to the obtained phase current to convert the three-phase system into a two-phase orthogonal coordinate system.

[0089] Device 100 also includes an observer module 110 for calculating and / or estimating the current amplitude I. pk IB angle, current angle, and motor speed.

[0090] The device 100 also includes a current-speed control module 161, which uses the speed error between the target speed and the measured speed to control the motor speed. The speed control module returns the target current amplitude. In this exemplary embodiment of the invention, the speed control module is a PID controller.

[0091] In this exemplary embodiment of the invention, the angle control module 140 is a PID controller. It controls the angle between the motor current and the BEMF vector, and returns the voltage angle Θ that must be applied to the motor. v .

[0092] In this exemplary embodiment of the invention, the amplitude control module 181 is a PID controller. It controls the current amplitude of the motor and adjusts the current based on the measured current amplitude I. pk With the target current amplitude "target I" pk The difference between the values ​​must be returned to the voltage amplitude Vpk applied to the motor.

[0093] In an embodiment of the present invention, the open-loop angle module 120 includes a B-angle module 120A and an open-loop IB-angle calculator 120B.

[0094] The B-angle module 120A returns the open-loop BEMF angle based on the desired open-loop control curve (e.g., based on the open-loop velocity). Depending on the application, the open-loop velocity can remain constant, increase linearly, or even increase quadratically. In embodiments of the invention, the block is initialized in a manner that makes the initial IB angle equal to or very close to zero (resulting in no or very small jumps in the voltage angle output).

[0095] The Open-Loop IB Angle Calculator 120B calculates the difference between the OL (open-loop) BEMF angle and the observed I angle.

[0096] Angle transition module 130 calculates a weighted average between the open-loop IB angle and the observed IB angle to obtain a weighted average IB angle. In embodiments of the invention, the weights are changed during the transition to obtain a smooth result. In embodiments of the invention, the transition is triggered when the observed velocity exceeds a first predefined velocity threshold or when the observed data becomes sufficiently reliable (when the measurement noise becomes sufficiently small, e.g., when a sufficiently high BEMF is obtained).

[0097] In an embodiment of the invention, device 100 includes a current amplitude conversion module 171 configured to calculate a weighted average between a closed-loop target current amplitude and an open-loop target current amplitude during a transition to obtain a target peak current. In an embodiment of the invention, the closed-loop target current is obtained from a speed controller 161. In an embodiment, the weighting factor used for the weighted average is dynamically adjusted based on the motor speed. In an embodiment of the invention, the transition and the angle conversion module are triggered simultaneously.

[0098] In embodiments of the present invention (examples thereof are given below) Figure 2 and Figure 4 (As shown in the diagram), the control of the BLDC motor includes DC voltage amplitude control (without I...) pk (Control). Therefore, the device includes a voltage speed control module 162, which is configured to control the motor speed by generating a closed-loop target voltage amplitude based on the speed error.

[0099] In an embodiment of the invention, the device includes a voltage amplitude control module 182 configured to generate an open-loop voltage amplitude from an open-loop voltage amplitude and from a measured current amplitude.

[0100] In an embodiment of the invention, the device includes a voltage amplitude conversion module 172 configured to calculate a weighted average between the open-loop voltage amplitude generated by the voltage speed control module 162 and a target voltage amplitude to obtain a peak voltage to be applied to the motor.

[0101] Similar to Figure 3 , Figure 4 The detailed block diagram of the controller shown includes a drive module 150, a Clarke transform module 190, and an observer module 110. These modules can have... Figure 3 It has the same functionality as the modules in [the original text].

[0102] The voltage speed control module 162 uses the speed error and returns the voltage amplitude to be applied to the motor to control the motor speed.

[0103] The angle control module 140 controls the angle between the motor current and the BEMF vector, and returns the voltage angle that must be applied to the motor.

[0104] The open-loop angle module 120 includes the B angle module 120A and the open-loop IB angle calculator 120B.

[0105] The B-angle module 120A returns the open-loop BEMF angle based on the desired open-loop control curve (e.g., based on the open-loop velocity). Depending on the application, the open-loop velocity can remain constant, increase linearly, or even increase quadratically. In embodiments of the invention, the block is initialized in a manner that makes the initial IB angle equal to or very close to zero (resulting in no or very small jumps in the voltage angle output).

[0106] The Open-Loop IB Angle Calculator 120B calculates the difference between the OL BEMF angle and the observed I angle.

[0107] Angle transition module 130 calculates a weighted average between the open-loop IB angle and the observed IB angle to obtain a weighted average IB angle. In embodiments of the invention, the weights are changed during the transition to obtain a smooth result. In embodiments of the invention, the transition is triggered when the observed velocity exceeds a first predefined velocity threshold or when the observed data becomes sufficiently reliable (when the measurement noise becomes sufficiently small, e.g., when a sufficiently high BEMF is obtained).

[0108] In an embodiment of the invention, the device includes a voltage amplitude control module 182 configured to generate an open-loop voltage amplitude from an open-loop voltage amplitude and a measured current amplitude. In this exemplary embodiment of the invention, the voltage amplitude control module is a PID controller. The voltage amplitude control module returns the voltage amplitude required to control the current.

[0109] In this exemplary embodiment of the invention, the device includes a voltage amplitude conversion module 172. This module provides an optional conversion between a voltage amplitude obtained by an open-loop algorithm and a voltage amplitude obtained by a speed controller. This conversion can also be a weighted average of the two, with the weights changing during the conversion. In the presence of a conversion, it can be triggered simultaneously with an IB OL-CL (closed-loop) conversion.

[0110] In an embodiment of the present invention, the transition from open-loop to closed-loop can be achieved as follows: Before the transition begins, the angle control module 140 can be reset with the open-loop angle as the voltage angle, thereby causing the angle control module to have the same voltage angle output.

[0111] In embodiments of the invention, the device is also initialized using open-loop velocity. When closed-loop control (e.g., an FOC algorithm) includes current control (e.g., speed control 161), the same current controller can remain active before, after, and during the transition, or there can be a transition between two different current controllers. When closed-loop control (e.g., an FOC algorithm) does not include a current controller, there must be a transition between the voltage speed control module 162 and the voltage amplitude transition module 172. This transition can be instantaneous or gradual, as in the angle transition module 130.

[0112] In an embodiment of the invention, the controller that will become active can be initialized based on the current and voltage output at the start of the transition.

[0113] The weighted average IB angle used by the angle control module 140 (e.g., a PID controller) is a weighted average of the closed-loop IB angle and the open-loop IB angle, which is based on measurement and calculated in an open-loop manner.

[0114] The closed-loop IB angle calculated based on measurements contains measurement noise, which is typically greater as the speed decreases. This is why, in embodiments of the present invention, the motor is driven in an open-loop manner at lower speeds.

[0115] The open-loop IB angle is calculated by subtracting the open-loop B angle from the measured current angle. The open-loop B angle is typically based on a linear increase in the speed of the open-loop control, but in different situations, it may be more beneficial to increase the angle quadratically or keep it constant.

[0116] At the start of the transition from open-loop to closed-loop, the open-loop B angle can be set equal to the applied voltage angle. Alternatively, the initial open-loop B angle can be set such that the first IB angle is calculated to be zero (open-loop B angle = observed I angle). The result is that there is no IB error at the start of the transition. When the angle control module 140 is a PID controller and there is no IB error at the start of the transition, this means that the proportional portion of the controller does not react immediately.

[0117] In embodiments of the invention, the transition period can be time-based. In such embodiments, the angle transition module is configured such that the open-loop IB angle receives a linearly lower weight until the transition period has elapsed and the open-loop weight equals zero. In alternative embodiments, the weights can be calculated based on the amount of measurement noise or based on the current rotor speed. This can be advantageous in certain situations because it allows for a more optimized selection of weights. For example, if the motor is operating under low load and therefore low current and typically has higher measurement noise, or if the motor is operating under high load and therefore high current and typically has lower measurement noise, then the selection of weights based on measurement noise can be more optimized. However, this can result in a less smooth transition.

[0118] In a second aspect, embodiments of the present invention relate to a method for controlling a BLDC motor. Figure 5 The figure illustrates an exemplary method 300 for controlling a brushless direct current (BLDC) motor 200, highlighting the main control process and optional components (shown in dashed lines). The structure of the process is as follows.

[0119] Drive motor 310: Drives the motor by applying voltage to motor 200.

[0120] Obtaining the 321-degree closed-loop IB angle: The system measures the current angle and calculates the closed-loop IB angle by comparing it with the closed-loop BEMF angle based on the applied voltage. In embodiments of the invention, the method includes obtaining a 321-degree closed-loop IB angle based on the applied voltage and the measured current, the 321-degree closed-loop IB angle being between the measured current angle and the closed-loop BEMF angle.

[0121] Obtaining the 322 open-loop IB angle: The system also includes obtaining the open-loop IB by calculating the angle between the measured current angle and the open-loop BEMF angle, which is determined based on the desired open-loop control curve. This can be done simultaneously with obtaining the closed-loop IB angle.

[0122] Calculate the 323 weighted average IB angle: Calculate the weighted average of the closed-loop IB angle and the open-loop IB angle to ensure a smooth transition between open-loop and closed-loop control.

[0123] Determine the 324 voltage angle: Based on the weighted average IB angle, determine the voltage angle and apply it to the motor to drive the motor operation efficiently.

[0124] In embodiments of the present invention, the method may optionally generate a closed-loop target current amplitude (331a) and an open-loop target current amplitude (331b) based on the speed error, and calculate a weighted average of these amplitudes (332) to generate a target peak current. Furthermore, the method may generate a peak voltage (333) based on the target peak current and the measured current amplitude, and apply this peak voltage to the motor.

[0125] Alternatively, the method can generate a closed-loop target voltage amplitude (341) based on the speed error and an open-loop voltage amplitude (342) based on the open-loop current and the measured current amplitude. These are used to calculate a weighted average voltage amplitude (343) that determines the peak voltage applied to the motor.

[0126] In embodiments of the present invention, the weighting factors for IB angle, current amplitude, or voltage amplitude are dynamically adjusted based on motor speed or predefined conditions, thereby ensuring a smooth and efficient transition between open-loop control and closed-loop control.

[0127] This method enhances motor control performance and reduces the risk of interference such as torque surges and current spikes during transitions between control modes.

[0128] Figure 6 The diagram illustrates the change of phase current over time in a BLDC motor controlled using a device or method according to an embodiment of the invention. The left portion of the graph shows the open-loop phase current, the middle portion shows the transition period, and the right portion shows the closed-loop control period implemented by the FOC during that period.

[0129] In embodiments of the invention, the closed-loop to open-loop transition is implemented as an open-loop to closed-loop transition, but in the opposite direction. The transition can be triggered when the motor speed becomes less than a second predefined speed threshold. The second predefined speed threshold can be less than a first predefined speed threshold. In other embodiments, the transition can be triggered when the current and / or BEMF amplitude becomes too small (too much measurement noise).

[0130] Figure 7 The diagram illustrates the change of phase current over time in a BLDC motor controlled using an apparatus or method according to an embodiment of the present invention, where the transition is from closed-loop control to open-loop control. The left portion of the graph shows the closed-loop phase current (using FOC control), the middle portion shows the transition period, and the right portion shows the open-loop control period.

[0131] Figures 8 to 15An oscilloscope screen image shows the PWM drive signal and phase current obtained when driving a BLDC motor using a device or method according to an embodiment of the present invention. For all these tests, worst-case conditions were applied to ensure that the actual transition in practice is always better, as shown in the oscilloscope screen image. The following worst-case conditions have been set:

[0132] - Current amplitude transitions or voltage amplitude transitions are always instantaneous. On the other hand, in practice, the target peak current can be obtained by calculating a weighted average between the closed-loop target current amplitude and the open-loop target current amplitude, or the peak voltage can be obtained by calculating a weighted average between the open-loop voltage amplitude and the target voltage amplitude.

[0133] - Use motors and / or geared motors with a non-sinusoidal BEMF shape. This results in low inertia, especially when combined with a gearbox, making any shocks visible in the current shape.

[0134] - The second predefined signal-to-noise ratio threshold for the closed-loop to open-loop transition is set to a reduced signal-to-noise ratio.

[0135] An advantage of embodiments of the present invention is that, despite these conditions, the apparatus or method according to embodiments of the present invention can perform the transition without any speed changes or current spikes.

[0136] Figure 8 An image of an oscilloscope screen is shown, plotting the open-loop to closed-loop transition with a fan having a non-sinusoidal BEMF.

[0137] Figure 9 An image of an oscilloscope screen is shown, plotting the closed-loop to open-loop transition with a fan having a non-sinusoidal BEMF.

[0138] Figure 10 An oscilloscope screen image is shown, plotting the open-loop to closed-loop transition of a three-phase gearbox motor under no-load conditions.

[0139] Figure 11 An oscilloscope screen image is shown, depicting the open-loop to closed-loop transition of a three-phase gearbox motor with a load.

[0140] Figure 12 An oscilloscope screen image is shown, plotting the closed-loop to open-loop transition of a three-phase gearbox motor under no-load conditions.

[0141] Figure 13 An oscilloscope screen image is shown, depicting a plot of the closed-loop to open-loop transition of a three-phase gearbox motor under load.

[0142] Figure 14An image of an oscilloscope screen is shown, depicting the open-loop to closed-loop transition of a 4-phase bipolar stepper motor with a gearbox.

[0143] Figure 15 An image of an oscilloscope screen is shown, depicting a closed-loop to open-loop transition of a 4-phase bipolar stepper motor with a gearbox.

Claims

1. A device (100) for controlling a brushless DC motor (200), said device (100) comprising: A drive module (150) configured to apply voltage to the motor (200) to drive the motor (200); Observer module (110) is configured to obtain the closed-loop IB angle between the measured current angle and the closed-loop BEMF angle based on the applied voltage. An open-loop angle module (120) is configured to obtain an open-loop IB angle between a measured current angle and an open-loop BEMF angle, wherein the open-loop BEMF angle is calculated based on a desired open-loop control curve. An angle transformation module (130) is configured to calculate a weighted average IB angle based on the closed-loop IB angle and the open-loop IB angle; An angle control module (140) is configured to determine the voltage angle to be applied to the motor based on the weighted average IB angle.

2. The device (100) according to claim 1, further comprising: - Current speed control module (161), the current speed control module (161) is configured to control the motor speed by generating a closed-loop target current amplitude based on the speed error; - Current amplitude conversion module (171), which is configured to calculate a weighted average between the closed-loop target current amplitude and the open-loop target current amplitude to obtain a target peak current; - Current amplitude control module (181), which is configured to generate a peak voltage to be applied to the motor from the target peak current and from the measured current amplitude.

3. The device (100) according to claim 1, further comprising: - Voltage speed control module (162), the voltage speed control module (162) being configured to control the motor speed by generating a closed-loop target voltage amplitude based on speed error; - Voltage amplitude control module (182), the voltage amplitude control module (182) being configured to generate an open-loop voltage amplitude from the open-loop current amplitude and from the measured current amplitude; - Voltage amplitude conversion module (172), which is configured to calculate a weighted average between the open-loop voltage amplitude and the target voltage amplitude generated by the voltage speed control module (162) to obtain the peak voltage to be applied to the motor.

4. The device (100) according to claim 1, characterized in that, The angle transformation module (130) is configured to calculate the weighted average IB angle using a weighting factor and to dynamically adjust the weighting factor based on the motor speed.

5. The device (100) according to claim 4, characterized in that, The angle transformation module (130) is configured to linearly change the weighting factor such that the open-loop IB angle receives a lower weight when transitioning from closed-loop to open-loop and a higher weight when transitioning from open-loop to closed-loop.

6. The device (100) according to claim 4, characterized in that, The angle transformation module (130) is configured to calculate weights based on the motor speed or the signal-to-noise ratio of the measured back electromotive force.

7. The device (100) according to claim 1, characterized in that, The angle conversion module (130) is configured to: initiate the transition from open loop to closed loop when the motor speed exceeds a first predefined speed threshold or when the signal-to-noise ratio of the measured back electromotive force exceeds a first predefined signal-to-noise ratio threshold, and initiate the transition from closed loop to open loop when the motor speed becomes less than a second predefined speed threshold or when the signal-to-noise ratio of the measured back electromotive force becomes less than a second predefined signal-to-noise ratio threshold.

8. The device (100) according to claim 1, characterized in that, When the angle transition module (130) resets at the beginning of the transition from open loop to closed loop, the angle control module (140) takes the open loop angle from the open loop angle module (120) as the voltage angle.

9. The device (100) according to claim 2, characterized in that, The current amplitude conversion module (171) is configured to calculate the target peak current using a weighting factor and dynamically adjust the weighting factor based on the motor speed.

10. The device (100) according to claim 3, characterized in that, The voltage amplitude conversion module (172) is configured to calculate the peak voltage using a weighting factor and dynamically adjust the weighting factor based on the motor speed.

11. A method (300) for controlling a brushless DC motor (200), the method (300) comprising: - The motor is driven (310) by applying voltage to the motor; - Obtain (321) the closed-loop IB angle between the measured current angle and the closed-loop BEMF angle based on the applied voltage; - Obtain (322) the open-loop IB angle between the measured current angle and the open-loop BEMF angle, wherein the open-loop BEMF angle is calculated based on the desired open-loop control curve; - Calculate the (323) weighted average IB angle based on the closed-loop IB angle and the open-loop IB angle; - The voltage angle that must be applied to the motor is determined based on the weighted average IB angle (324).

12. The method (300) according to claim 11, further comprising: - Generate (331a) closed-loop target current amplitude based on velocity error and obtain (331b) open-loop target current amplitude; - Calculate the weighted average between the closed-loop target current amplitude and the open-loop target current amplitude (332) to obtain the target peak current; - Generate (333) the peak voltage to be applied to the motor from the target peak current and from the measured current amplitude.

13. The method (300) according to claim 11, further comprising: - Generate closed-loop target voltage amplitude based on velocity error; - Generate the (342) open-loop voltage amplitude from the open-loop current amplitude and from the measured current amplitude; - Calculate (343) the weighted average between the open-loop voltage amplitude and the generated target voltage amplitude to obtain the peak voltage to be applied to the motor.

14. The method (300) according to claim 11, characterized in that, The calculation (323) of the weighted average IB angle includes using a weighting factor and dynamically adjusting the weighting factor based on the motor speed.

15. The method (300) according to claim 14, characterized in that, The calculation (323) of the weighted average IB angle includes linearly changing the weighting factor so that the open-loop IB angle receives a lower weight when transitioning from closed-loop to open-loop and a higher weight when transitioning from open-loop to closed-loop.

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