FOC-based DC brushless motor limited power constant speed control method

Abstract

The invention discloses a motor constant speed control method capable of limiting maximum output power, which is based on a vector control FOC architecture, calculates a torque current required for running to the maximum power allowed by a system in real time, and compares the torque current with a torque current required for running to an instruction speed and output by a constant speed control module in real time, so as to limit the maximum output power. And the smaller value of the two is output through the current clamping logic, so that the torque current required by constant-speed control is met as far as possible on the premise that the maximum power is not exceeded, and the actual rotating speed of the motor is close to the instruction rotating speed.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a method for controlling a brushless DC motor with limited power and constant speed based on FOC. Background Art

[0002] When the motor is in constant speed mode, if the motor speed remains unchanged and the load increases, the output power of the motor will increase accordingly. In practical applications, due to the load capacity of the power supply, when the output power of the motor exceeds the maximum power that the power supply can bear, in order to protect the power supply, it is often necessary to limit the output power of the motor, that is, on the basis of constant speed control, the demand for limiting the maximum output power of the motor is superimposed. Specifically, if the power required to reach the target speed does not exceed the maximum power limit under the current load, the motor runs at the target speed. If the current load is heavy and the power required to reach the target speed exceeds the maximum power limit, the actual speed of the motor is lower than the target speed, and the actual output power is equal to the maximum power limited by the system.

[0003] In traditional constant speed control methods, the maximum output power of the motor is often approximately limited by limiting the maximum torque current of the motor. This is because there is a positive correlation between the torque current and the motor power. When the motor speed remains unchanged and the load increases, the torque current of the motor also increases accordingly. However, the torque current cannot accurately reflect the motor power, so this method is relatively rough and cannot achieve the motor running at the maximum power limited by the system under heavy load. Another method is to dynamically adjust the input command. When it is detected that the output power of the motor exceeds the specified threshold, the system gradually reduces the command speed so that the motor power drops to the maximum power allowed. However, this method essentially superimposes a power control loop on the speed control loop of the motor. To avoid oscillation, the bandwidth of the power control loop needs to be much lower than that of the speed control loop. Therefore, when the load fluctuates rapidly, due to the low bandwidth of the power control loop, this method is prone to power overshoot and cannot meet the maximum power limit.

[0004] It can be seen that a new power-limited constant speed control method for a brushless DC motor is needed in the art, which can provide a higher control bandwidth and achieve precise power limitation at the same time. Summary of the invention

[0005] The present invention proposes a new FOC-based DC brushless motor power limited constant speed control method. The method is based on a vector control (FOC) architecture, calculates in real time the torque current required for running to the maximum power allowed by the system, and compares it with the torque current required for running to the command speed output by a constant speed control module in real time, and outputs the smaller value of the two through current clamping logic, thereby achieving the torque current required for constant speed control as much as possible without exceeding the maximum power, so that the actual speed of the motor is close to the command speed.

[0006] Based on the above technical purpose, the present invention provides a power-limited constant speed control method for a brushless DC motor based on FOC, the method is used for a motor vector control system, the motor vector control system comprises: a Q-axis voltage generation unit, a D-axis voltage generation unit, a three-phase voltage generation unit, a three-phase current acquisition unit and a constant speed Q-axis target current calculation unit; the constant speed Q-axis target current calculation unit comprises: a constant speed PI control unit, a constant power control unit and a current clamping logic unit;

[0007] The power-limited constant-speed control method comprises:

[0008] The command speed Spd cmd And the actual speed of the motor Spd act Input the constant speed PI control unit to calculate and obtain the command speed Spd cmd The constant speed Q-axis target current I q_spd ;

[0009] According to the maximum power setting value Pwr max Calculate the constant speed Q-axis target current I required to obtain maximum power q_pwr_max ; The operation process is satisfied by: Where V d is the D-axis control voltage, V q is the Q-axis control voltage, I d_fb is the measured current of D axis;

[0010] The constant speed Q-axis target current I required for maximum power q_pwr_max Send it to the low-pass filter for low-pass filtering to avoid I q_pwr_max The high-frequency fluctuations of the system control cause oscillations, generating the constant speed Q-axis target current I required for the maximum power after filtering. q_pwr_max_filt ;

[0011] The constant speed Q-axis target current I required for the maximum power after filtering q_pwr_max_filt and constant speed Q axis target current I q_spd The current clamp logic unit outputs the constant speed Q-axis target current I required for maximum power. q_pwr_max_filt and constant speed Q axis target current I q_spd The smaller value of the current clamp logic unit outputs the result as the final constant speed Q axis target current I q_ref Input to the Q-axis voltage generation unit.

[0012] In one embodiment, the Q-axis voltage generating unit is used to generate a Q-axis control voltage V for controlling the operation of the motor. q The D-axis voltage generating unit is used to generate a D-axis control voltage V for controlling the operation of the motor. d .

[0013] In one embodiment, the three-phase voltage generating unit is used to convert the Q-axis control voltage V generated by the Q-axis voltage generating unit and the D-axis voltage generating unit into q and D-axis control voltage V d It is converted into a three-phase voltage value for controlling the operation of the motor and output to the motor to control the operation of the motor.

[0014] In one embodiment, the three-phase current acquisition unit is used to acquire the three-phase current value of the motor under the actual operation state, and convert the three-phase current value into the Q-axis measured current I q_fb And the D-axis measured current I d_fb .

[0015] In one embodiment, the PI control performed by the constant speed PI control unit includes:

[0016] Using the command speed Spd cmd and actual speed Spd act Calculate the difference err in real time;

[0017] The difference err is amplified by Kp times through the proportional multiplier and sent to the adder;

[0018] The difference err is amplified by Ki times through the integral term multiplier and sent to the integrator, and the result of the integrator is also sent to the adder;

[0019] The adder outputs the constant speed Q-axis target current I required to achieve the command speed Spd_cmd q_spd ; Among them, the proportional gain Kp is positively correlated with the load moment of inertia, negatively correlated with the motor pole pair number and back electromotive force constant, and the integral gain Ki is positively correlated with the constant speed PI control update cycle.

[0020] Compared with the prior art, one or more embodiments of the present invention may have the following advantages:

[0021] This method is based on the vector control (FOC) technology of the brushless DC motor. It can ensure that no matter how the load fluctuates, the actual speed of the motor is as close to the command speed as possible without exceeding the maximum output power allowed by the system.

[0022] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 1 is a schematic diagram of the structure of a vector control system of a motor according to an embodiment of the present invention;

[0025] Figure 2 2 is a schematic diagram of the structure of a constant speed Q-axis target current calculation unit according to an embodiment of the present invention;

[0026] Figure 3 It is a schematic diagram of a constant speed PI control process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings.

[0028] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present invention necessarily has the first element, component, region, layer or part.

[0029] Spatially relative terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used here for convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, then the elements or features described as "under other elements" or "under it" or "under it" will be oriented as "on" other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0030] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0031] Example 1

[0032] The motor power limiting constant speed control system based on the vector control (FOC) method of this embodiment is as follows Figure 1 As shown, the motor power-limited constant speed control system based on the vector control (FOC) method includes: a Q-axis voltage generation unit 100, a D-axis voltage generation unit 200, a three-phase voltage generation unit 300, a three-phase current acquisition unit 400 and a constant speed Q-axis target current calculation unit 500. The Q-axis voltage generation unit 100 is used to generate a Q-axis control voltage V for controlling the operation of the motor. q The D-axis voltage generating unit 200 is used to generate a D-axis control voltage V for controlling the operation of the motor. d The three-phase voltage generating unit 300 is used to generate the Q-axis control voltage V generated by the Q-axis voltage generating unit 100 and the D-axis voltage generating unit 200. q and D-axis control voltage V d The three-phase current acquisition unit 400 is used to collect the three-phase current value of the motor under the actual operation state, and convert the three-phase current value into the Q-axis measured current I q_fb And the D-axis measured current I d_fbThe constant speed Q-axis target current calculation unit 500 is used to generate a constant speed Q-axis target current I according to a preset system maximum power and an input command speed. q_ref The constant speed Q axis target current I q_ref Used to control the Q-axis voltage generating unit 100 to generate the Q-axis control voltage V q .

[0033] In the above system, the motor rotor is used as the reference to establish a DQ orthogonal coordinate system. Among them, the D axis is parallel to the magnetic field direction of the rotor, and the Q axis is perpendicular to the magnetic field direction of the rotor. Since only the current on the Q axis can provide effective torque to make the motor rotate, the Q axis target current Iq_ref is generated according to the input speed command and the maximum power allowed by the system during control. Then, according to the target D axis current I d_ref and Q axis current I q_ref Generate D-axis control voltage V through closed-loop control d and Q-axis control voltage V q Finally, the system converts the voltage V d and V q It is applied to the U, V, and W phases of the motor in the form of PWM.

[0034] like Figure 2 As shown, the constant speed Q-axis target current calculation unit 500 of this embodiment includes a constant speed PI control unit 501, a power control unit 502 and a current clamping logic unit 503. The power-limited constant speed control method of the present invention includes:

[0035] First, the command speed Spd cmd And the actual speed of the motor Spd act The input constant speed PI control unit 501 calculates and obtains the command speed Spd cmd The constant speed Q-axis target current I q_spd Specifically: The PI control performed by the constant speed PI control unit is as follows: Figure 3 As shown, the command speed Spd cmd is the target value in PI control, the actual speed Spd act The constant speed PI control module uses adder 1 to calculate the difference err between the target value and the feedback value in real time. Then, on the one hand, the difference err is amplified by Kp times through the proportional multiplier and sent to one input of adder 2; on the other hand, the difference err is amplified by Ki times through the integral multiplier and sent to the integrator. The result of the integrator is sent to the other input of adder 2. The current finally generated by adder 2 is the speed command Spd. cmd Required constant speed constant speed Q axis target current I q_spdHere, the proportional gain Kp is positively correlated with the load moment of inertia, negatively correlated with the motor pole pair number and the back electromotive force constant, and the integral gain Ki is positively correlated with the constant speed PI control update cycle.

[0036] Then, according to the maximum power setting value Pwr max Calculate the constant speed Q-axis target current I required to obtain maximum power q_pwr_max ; The operation process is satisfied by: Where V d is the D-axis control voltage, V q is the Q-axis control voltage, I d_fb is the actual measured current of the D axis.

[0037] The constant speed Q-axis target current I required for maximum power q_pwr_max Send it to the low-pass filter for low-pass filtering to avoid I q_pwr_max The high-frequency fluctuations of the system control cause oscillations, generating the constant speed Q-axis target current I required for the maximum power after filtering. q_pwr_max_filt .

[0038] Finally, the constant speed Q-axis target current I required for the maximum power after filtering is q_pwr_max_filt and constant speed Q axis target current I q_spd The current clamp logic unit 503 outputs the constant speed Q-axis target current I required for maximum power. q_pwr_max_filt and constant speed Q axis target current I q_spd The smaller value of . And the result is output by the current clamp logic unit 503 as the final constant speed Q axis target current I q_ref Input to the Q-axis voltage generating unit 100 .

[0039] The method proposed in the present invention can realize that no matter how the load changes, the motor does not exceed the maximum allowable power Pwr max Under the premise, the actual running speed should be as close as possible to the input command speed Spd cmd This is because: when the motor load is low, the torque current I required to meet the command speed q_spd Lower than the torque current I required to achieve maximum power q_pwr_max_filt , at this time the current clamp logic output I q_ref Equal to I q_spd , this torque current can drive the motor to reach the command speed, and the motor works in the constant speed range. As the motor load increases, the torque current required to meet the command speed increases accordingly, and finally I q_spd More than I q_pwr_max_filt , at this time the current clamp logic output I q_ref Equal to I q_pwr_max_filt , this torque current drives the motor to operate at the maximum power allowed by the system.

[0040] The present invention may be a system, method and / or computer program product at any possible level of integrated technical detail. The computer program product may include a computer-readable storage medium (or multiple media) having computer-readable program instructions thereon for causing a processor to perform various aspects of the present invention.

[0041] A computer readable storage medium may be a tangible device that can retain and store instructions used by an instruction execution device. The computer readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of computer readable storage media includes the following: a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device such as a punch card or a raised structure in a groove on which instructions are recorded, and any suitable combination of the above. A computer readable storage medium, as used herein, should not be interpreted as a transient signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted by a wire.

[0042] The computer-readable program instructions described herein may be downloaded from a computer-readable storage medium to a corresponding computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network may include copper transmission cables, optical transmission fibers, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions to be stored in a computer-readable storage medium within the corresponding computing / processing device.

[0043] The computer-readable program instructions for performing the operation of the present invention may be assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, configuration data for integrated circuits, or source code or object code written in any combination of one or more programming languages ​​and process programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as an independent software package, partially on the user's computer, partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer may be connected to the user's computer by any type of network including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., by using the Internet of an Internet service provider). In certain embodiments, the electronic circuit including, for example, a programmable logic circuit, a field programmable gate array (FPGA) or a programmable logic array (PLA) may execute the computer-readable program instructions by utilizing the state information of the computer-readable program instructions to personalize the electronic circuit, thereby performing aspects of the present invention.

[0044] Various aspects of the present invention are described herein with reference to flowcharts and / or block diagrams of methods, devices (systems) and computer program products according to embodiments of the present invention. It is understood that each block of the flowchart illustration and / or block diagram, and the combination of blocks in the flowchart illustration and / or block diagram, can be implemented by computer-readable program instructions.

[0045] These computer-readable program instructions may be provided to a processor of a computer or other programmable data processing device to produce a machine so that the instructions executed by the processor of the computer or other programmable data processing device create instructions for implementing the flowcharts and / or block diagrams. Figure 1 These computer-readable program instructions may also be stored in a computer-readable storage medium capable of booting a computer, a programmable data processing device and / or other device that operates in a specific manner, so that the computer-readable storage medium having the instructions stored therein includes a manufactured product that includes instructions that implement aspects of the functions / actions specified in the flowchart and / or block diagram blocks.

[0046] Computer readable program instructions may also be loaded into a computer, other programmable data processing device, or other device to cause a series of operating steps to be performed on the computer, other programmable devices or other devices for producing a computer-implemented process, so that the instructions executed on the computer, other programmable device or other device implement the functions / actions specified in the flowchart and / or block diagram blocks.

[0047] The flowcharts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the system, method and computer program product according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagram may represent a module, segment or portion of an instruction, which includes one or more executable instructions for implementing a specified logical function. In some optional implementations, the functions indicated in the block may occur outside the order indicated in the figure. For example, in fact, two blocks shown in succession can be completed as a step, and depending on the functions involved, they can be executed concurrently, substantially concurrently, in a partially or fully time-overlapping manner, or sometimes these blocks can be executed in reverse order. It will also be noted that each block of the block diagram and / or flowchart illustration, as well as the combination of blocks in the block diagram and / or flowchart illustration, can be implemented by a dedicated hardware-based system that performs a specified function or action or performs a combination of dedicated hardware and computer instructions.

[0048] The embodiments of the present application are described with reference to the flowcharts and / or block diagrams of the methods, apparatuses (devices) and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0049] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0050] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

Claims

1. A method for controlling a brushless DC motor with limited power and constant speed based on FOC, the method being used in a motor vector control system, the motor vector control system comprising: Q-axis voltage generating unit, D-axis voltage generating unit, three-phase voltage generating unit, three-phase current collecting unit and constant speed Q-axis target current calculating unit; The constant speed Q-axis target current calculation unit includes: a constant speed PI control unit, a control unit and a current clamping logic unit; The method comprises: The command speed Spd cmd And the actual speed of the motor Spd act Input the constant speed PI control unit to calculate and obtain the command speed Spd cmd The constant speed Q-axis target current I q_spd ; According to the maximum power setting value Pwr max Calculate the constant speed Q-axis target current I required to obtain maximum power q_pwr_max ; The operation process satisfies: Where V d is the D-axis control voltage, V q is the Q-axis control voltage, I d_fb is the measured current of the D axis; The constant speed Q-axis target current I required for maximum power q_pwr_max Send it to the low-pass filter for low-pass filtering to avoid I q_pwr_max The high-frequency fluctuations of the system control cause oscillations, generating the constant speed Q-axis target current I required for the maximum power after filtering. q_pwr_max_filt ; The constant speed Q-axis target current I required for the maximum power after filtering q_pwr_max_filt and constant speed Q axis target current I q_spd The current clamp logic unit outputs the constant speed Q-axis target current I required for maximum power. q_pwr_max_filt and constant speed Q axis target current I q_spd The smaller value of the current clamp logic unit outputs the result as the final constant speed Q axis target current I q_ref Input to the Q-axis voltage generation unit.

2. The power-limited constant speed control method according to claim 1, characterized in that: The Q-axis voltage generating unit is used to generate a Q-axis control voltage V to control the operation of the motor. q The D-axis voltage generating unit is used to generate a D-axis control voltage V for controlling the operation of the motor. d .

3. The power-limited constant speed control method according to claim 1, characterized in that: The three-phase voltage generating unit is used to generate the Q-axis control voltage V generated by the Q-axis voltage generating unit and the D-axis voltage generating unit. q and D-axis control voltage V d It is converted into a three-phase voltage value for controlling the operation of the motor and output to the motor to control the operation of the motor.

4. The power-limited constant speed control method according to claim 1, characterized in that: The three-phase current acquisition unit is used to collect the three-phase current value of the motor under the actual operation state, and convert the three-phase current value into the Q-axis measured current I q_fb And the D-axis measured current I d_fb .

5. The power-limited constant speed control method according to claim 1, characterized in that: The PI control performed by the constant speed PI control unit includes: Using the command speed Spd cmd and actual speed Spd act Calculate the difference err in real time; The difference err is amplified by Kp times through the proportional multiplier and sent to the adder; The difference err is amplified by Ki times through the integral term multiplier and sent to the integrator, and the result of the integrator is also sent to the adder; The adder output reaches the command speed Spd _cmd Required constant speed Q-axis target current I q_spd ; Among them, the proportional gain Kp is positively correlated with the load moment of inertia, negatively correlated with the motor pole pair number and back electromotive force constant, and the integral gain Ki is positively correlated with the constant speed PI control update cycle.

6. A computer-readable storage medium having computer instructions stored thereon, wherein: When the computer instructions are executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

7. A motor vector control system, characterized in that: The motor vector control system executes the method described in any one of claims 1-5 to perform power-limited constant speed control on the motor operation.

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