Field orientation control with sensor in power tool

Abstract

A power tool includes a housing, a brushless motor, one or more position sensors, a power switching circuit, and an electronic controller. The one or more position sensors are configured to generate an output signal corresponding to a rotational position of the brushless motor. The power switching circuit is configured to provide a supply of power from a power source to the brushless motor. The electronic controller is configured to implement field oriented control ("FOC") of the brushless motor. The electronic controller is configured to: receive output signals from the one or more position sensors; determining a parameter of the brushless motor based on the output signal; determining a driving parameter for the brushless motor based on the parameter of the brushless motor and using the FOC; generating a driving instruction based on the driving parameter; and driving the brushless motor based on the driving instruction.

Description

Related Applications

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 591,860 filed on October 20, 2023 and U.S. Provisional Patent Application No. 63 / 610,600 filed on December 15, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] Specific embodiments described herein relate to a power tool including a brushless DC motor. Summary of the invention

[0003] A conventional brushless direct current ("DC") motor includes a stator, and a rotor configured to rotate relative to the stator by a magnetic field generated by one or more phases of the stator. Typically, the stator and rotor are separated by an air gap. To properly generate the magnetic field at the correct phase, the conventional brushless DC motor further includes a plurality of sensors, such as position sensors (e.g., magnetic sensors, Hall effect sensors, inductive sensors, magnetic sine / cosine encoders or inductive sine / cosine encoders, etc.), configured to sense the angular position of the rotor relative to the stator. To properly generate the magnetic field at the correct phase, one or more control algorithms are used to control the energization of the phases of the stator.

[0004] The specific embodiments described in this application relate to a power tool configured to implement sensored field oriented control ("sFOC"). In sFOC, both the stator and the rotor generate magnetic flux. Specifically, the stator flux current i d and the stator torque current i q is the stator current vector I s The stator flux can therefore be determined as a function of the stator current. The purpose of sFOC is to align the stator flux to be orthogonal to the rotor flux. Once the position of the rotor is known, the power tool controls the phases of the stator to produce the appropriate magnetic field so that the stator flux remains orthogonal to the rotor flux. Controlling the motor with sFOC has several advantages, such as the ability to independently control motor speed and motor torque.

[0005] Unlike other control topologies, sFOC does not use one or three low-side shunts to measure the DC bus or motor line current. Instead, sFOC uses two inline shunts to accurately measure the inverter / motor line current and allow arbitrary sampling within the PWM cycle while being well resistant to PWM noise interference. Additionally, the high-side DC bus current sensor provides the inverter with robust short-circuit and overcurrent protection. In this way, sFOC can perform actual overcurrent detection on two of the three-line currents.

[0006] Furthermore, unlike other control techniques, sFOC estimates the rotor speed and continuous rotor angle based on the logic value of the position sensor (e.g., digital Hall effect sensor) signal and its transition events (e.g., rising or falling edge) without using any interrupt routines on the microcontroller. This results in a sinusoidal stator current with low harmonic content from the inverter commutation using a continuous angle.

[0007] Additionally, unlike the classic block commutation control topology commonly used in power tools and outdoor power equipment, sFOC exhibits better dynamic and steady-state performance and controllability.

[0008] The electric tool described in the present application includes a housing, a brushless motor, one or more position sensors, a power switching circuit and an electronic controller. The brushless motor is arranged in the housing. The brushless motor includes a rotor and a stator. The stator is coupled to the motor shaft and is arranged to rotate around the longitudinal axis. The longitudinal axis extends through the motor shaft. The motor shaft is arranged to generate a rotational output to the drive mechanism. One or more position sensors are arranged adjacent to the brushless motor. One or more position sensors are configured to generate an output signal corresponding to the rotational position of the brushless motor. The power switching circuit is configured to provide the brushless motor with a power supply from a power supply. The electronic controller is connected to the one or more position sensors and the power switching circuit, and the electronic controller is configured to implement field oriented control ("FOC") of the brushless motor. The electronic controller is configured to: receive output signals from one or more position sensors; determine parameters of the brushless motor based on the output signals from the one or more position sensors; determine drive parameters for the brushless motor based on the parameters of the brushless motor and using FOC; generate drive instructions based on the drive parameters; and drive the brushless motor based on the drive instructions.

[0009] In some aspects, the parameter of the brushless motor includes at least one of a rotational position, a speed, or an acceleration of the brushless motor.

[0010] In some aspects, the drive parameter of the brushless motor is a plurality of duty cycles for each phase of the motor.

[0011] In some aspects, the electronic controller is further configured to generate the current command via the speed regulator and output signals from one or more position sensors.

[0012] In some aspects, the electronic controller is further configured to determine a rotor speed based on output signals from the one or more position sensors and generate a current command using a speed regulator, wherein the current command is based on the rotor speed and the target speed.

[0013] In some aspects, the electronic controller is further configured to determine operation in the torque mode based on a mode command received via a mode select switch, receive a torque input command based on a user input, and generate the current command based on the torque input command.

[0014] In some aspects, the power tool further includes a battery pack current sensor electrically connected to the battery pack, a stator current sensor electrically connected to the motor stator, and a mixed signal programmable logic device that communicates with the battery pack current sensor and the stator current sensor, the mixed signal programmable logic device being configured to detect a fault condition.

[0015] In some aspects, the fault condition is a short circuit condition.

[0016] In some aspects, the electronic controller is further configured to determine a first feedforward term and a second feedforward term based on a signal from a stator current sensor and output signals from one or more position sensors, wherein the first feedforward term corresponds to motor speed and the second feedforward term corresponds to motor torque.

[0017] The method described in the present application for controlling a brushless motor of a handheld power tool includes: receiving output signals from one or more position sensors; determining parameters of the brushless motor based on the output signals from the one or more position sensors; determining drive parameters for the brushless motor based on the parameters of the brushless motor and using field-oriented control; generating drive instructions based on the drive parameters; and, driving the brushless motor based on the drive instructions.

[0018] In some aspects, the method further includes generating a current command via a speed regulator and output signals from one or more position sensors.

[0019] In some aspects, the method further includes determining a rotor speed based on output signals from the one or more position sensors and generating a current command using a speed regulator, wherein the current command is based on the rotor speed and the target speed.

[0020] In some aspects, the method further includes determining to operate in a torque mode based on a mode command received via a mode select switch, receiving a torque input command based on a user input, and generating the current command based on the torque input command.

[0021] In some aspects, the method further includes determining a first feedforward term and a second feedforward term based on a signal from a stator current sensor and output signals from one or more position sensors, wherein the first feedforward term corresponds to motor speed and the second feedforward term corresponds to motor torque.

[0022] The electric tool described in the present application includes a housing, a brushless motor, one or more position sensors, a stator current sensor, a power switching circuit and an electronic controller. The brushless motor is arranged in the housing. The brushless motor includes a rotor and a stator. The stator is coupled to the motor shaft and is arranged to rotate around the longitudinal axis. The longitudinal axis extends through the motor shaft. The motor shaft is arranged to generate a rotational output to the drive mechanism. One or more position sensors are arranged adjacent to the brushless motor. One or more position sensors are configured to generate an output signal corresponding to the rotational position of the brushless motor. The stator current sensor is configured to determine the current in at least one phase of the motor. The power switching circuit is configured to provide the brushless motor with a power supply from a power supply. The electronic controller is connected to the one or more position sensors and the power switching circuit, and the electronic controller is configured to implement field oriented control ("FOC") of the brushless motor. The electronic controller is configured to: receive output signals from one or more position sensors; determine the speed of the brushless motor based on the output signals from the one or more position sensors; determine a first feedforward term and a second feedforward term based on a signal from a stator current sensor and the speed of the brushless motor; generate a drive instruction based on the first feedforward term and the second feedforward term; and, drive the brushless motor based on the drive instruction.

[0023] In some aspects, the power tool further includes a battery current sensor electrically connected to the battery pack, and a mixed signal programmable logic device in communication with the battery current sensor and the stator current sensor, the mixed signal programmable logic device configured to detect a fault condition.

[0024] In some aspects, the fault condition is a short circuit condition.

[0025] In some aspects, the electronic controller is further configured to generate the current command via the speed regulator and output signals from one or more position sensors.

[0026] In some aspects, the electronic controller is further configured to determine a rotor speed based on output signals from the one or more position sensors and generate a current command using a speed regulator, wherein the current command is based on the rotor speed and the target speed.

[0027] In some aspects, the power tool further includes an electronic controller further configured to determine operation in a torque mode based on a mode command received via a mode select switch, receive a torque input command based on a user input, and generate a current command based on the torque input command.

[0028] Before explaining any specific embodiment in detail, it should be understood that the specific embodiment is not limited to the application in the configuration details and component arrangements described in the following description or shown in the accompanying drawings. The specific embodiments can be implemented or realized in various ways. In addition, it should be understood that the words and terms used in this application are for illustrative purposes and should not be regarded as limiting. The use of "including", "comprising", "having" and their variations is meant to cover both the items listed thereafter and their equivalents and additional items. Unless otherwise specified or limited, the terms "install", "connect", "support", "couple" and their variations are used in a broad sense, covering both direct installation, connection, support and coupling, and indirect installation, connection, support and coupling.

[0029] The articles "a," "an," and "the" should not be construed as meaning "one" or "only one," unless the context clearly indicates otherwise. Instead, these articles should be construed as meaning "at least one" or "one or more than one." Similarly, when the term "the" or "said" is used to refer to a noun previously introduced by the indefinite article "a" or "an," "the" or "said" means "at least one" or "one or more than one," unless the context clearly indicates otherwise.

[0030] In addition, it should be understood that a specific embodiment may include hardware, software, and electronic components or modules, and for the purpose of discussion, these hardware, software, and electronic components or modules may be shown and described as if most of the components are implemented only in hardware. However, based on the reading of the specific embodiments of the present application, a person of ordinary skill in the art will recognize that in at least one specific embodiment, the electronic-based aspects can be implemented in software (e.g., stored on a non-transitory computer-readable medium), and the software can be executed by one or more processing units such as microprocessors and / or application-specific integrated circuits ("ASICs"). Therefore, it should be noted that a plurality of hardware- and software-based devices and a plurality of different structural components can be used to implement specific embodiments. For example, the "server", "computing device", "controller", and "processor" described in this specification may include one or more processing units, one or more computer-readable medium modules, one or more input / output interfaces, and various connectors (e.g., system buses) connecting these components.

[0031] For relative terms used in relation to quantities or conditions, such as "about", "approximately", "substantially", etc., those of ordinary skill in the art will understand that the values ​​are included, and the meaning of the terms is determined by the context (e.g., the terms include at least the degree of error associated with measurement precision, the tolerance associated with a particular value [e.g., manufacturing, assembly, use tolerance, etc.], etc.). Such terms should also be considered to disclose a range defined by the absolute values ​​of the two endpoints. For example, the expression "from about 2 to about 4" also discloses a range of "from 2 to 4". Relative terms can refer to positive and negative percentages (e.g., 1%, 5%, 10%) of the indicated value.

[0032] It should be understood that although some drawings show hardware and software located in a specific device, these depictions are for illustrative purposes only. The functions performed by a component described in this application can be performed in a distributed manner by multiple components. Similarly, the functions performed by multiple components can be merged and performed by a single component. In some specific embodiments, the components shown can be combined or divided into separate software, firmware and / or hardware. For example, logic and processing can be distributed between multiple electronic processors, rather than being located in a single electronic processor and performed by a single electronic processor. Regardless of how they are combined or divided, hardware components and software components can be located in the same computing device, or can be distributed between different computing devices connected by one or more than one network or other suitable communication links. Similarly, components described as performing specific functions can also perform additional functions not described in this application. For example, a device or structure that is "configured" in a certain way is configured at least in this way, but can also be configured in a way that is not explicitly listed.

[0033] Accordingly, in a claim, if an apparatus, method or system is described as, for example, comprising a controller, a control unit, an electronic processor, a computing device, a logic element, a module, a memory module, a communication channel or network, or other elements configured in some manner to, for example, perform multiple functions, this claim or an element of the claim should be interpreted as indicating one or more of such elements, such an element, i.e., any one of the one or more elements is configured as described in the claim to, for example, implement any one or more of the listed multiple functions, so that the one or more elements together as a group perform multiple functions.

[0034] Other aspects of the embodiments will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Power tools implementing field oriented control with sensors are presented according to some specific embodiments.

[0036] Figure 2 A cross-sectional view of a power tool implementing field oriented control with a sensor is shown according to some specific embodiments.

[0037] Figure 3 A control system for a power tool implementing field oriented control with a sensor is presented according to some specific embodiments.

[0038] Figure 4 is a block diagram of a control system for a power tool implementing field oriented control with a sensor according to some specific embodiments.

[0039] Figure 5 is a flow chart for implementing field oriented control with sensors according to some specific embodiments.

[0040] Figure 6 is a block diagram of a control topology for a power tool implementing field oriented control with a sensor, according to some specific embodiments. DETAILED DESCRIPTION

[0041] Specific embodiments described herein relate to power tools, such as handheld power tools, that implement sensored brushless DC motors (“sensored motors”) and sensored field oriented control (“sFOC”).

[0042] Figure 1 A power tool 100 implementing sFOC is shown. Figure 1 In the illustrated embodiment, the power tool 100 is a drill / drilling machine. In other embodiments, the power tool 100 is a different type of power tool (e.g., an impact wrench, a ratchet wrench, a saw, a hammer drill, a percussion drill, a rotary hammer, a grinder, a hair dryer, a trimmer, a chain saw, etc.). The power tool 100 includes a housing 105 and a battery pack interface 110 for connecting the power tool 100 to, for example, a battery pack. In some embodiments, the battery pack interface 110 can be configured to connect the power tool 100 to another device.

[0043] Figure 2 Shown Figure 1 A cross section of a power tool 100. The power tool 100 includes at least one printed circuit board ("PCB") 205 for various components of the power tool 100. In some embodiments, the PCB 205 is a control PCB. In addition to or in lieu of the control PCB, the power tool 100 may include a power PCB, a forward / reverse PCB, and / or a light emitting diode ("LED") PCB. The power tool 100 may further include a motor 210. In some embodiments, the motor 210 may be an inductive motor. Figure 2A drive mechanism 215 and a cooling fan 225 are also shown, wherein the drive mechanism 215 is used to transmit the rotational output of the motor 210 to the output unit 220, and the cooling fan 225 is rotated by the motor 210 and used to provide cooling airflow for the components of the power tool 100. The power tool 100 may further include a trigger 230 configured to be actuated by a user. In some specific embodiments, the amount of actuation of the trigger 230 can be used to determine the amount of power supplied to the motor 210. The power tool 100 may further include a work light 235 configured to illuminate the working area of ​​the power tool 100. In some specific embodiments, the work light 235 can be installed below the drive mechanism 215. In some specific embodiments, the work light 235 can be configured to actuate in response to the actuation of the trigger 230.

[0044] Figure 3 Demonstrated implementation of sensor-based field-oriented control for power tools (e.g. Figure 1 The control system 300 of the power tool 100 is shown. The control system 300 includes a controller 304. The controller 304 is electrically connected and / or communicatively connected to various modules or components of the power tool. For example, the controller 304 is electrically connected to a motor 308 (e.g. Figure 2 motor 210), battery pack interface 312 (eg Figure 1 The battery pack interface 110 of FIG. 1 ), the trigger switch 316 (connected to the trigger 320 , for example Figure 2 The motor 308 includes at least one of a current sensor 324, a sensor or position sensor 328 (e.g., a magnetic sensor, a Hall effect sensor, an inductive sensor, a magnetic sine / cosine encoder or an inductive sine / cosine encoder, etc.), a temperature sensor, one or more indicators 332, one or more user input modules 336, a power input module 340, a gate controller 344 (connected to an inverter 348), and a mixed signal programmable logic device ("MS-PLD") 350. The motor 308 includes a rotor, a stator, and a shaft that rotates about a longitudinal axis.

[0045] The controller 304 includes a combination of hardware and software that is operable to, among other things, control the operation of the power tool, monitor the operation of the power tool, actuate one or more indicators 332 (e.g., LEDs), etc. The gate controller 344 is configured to control the inverter 348 to convert the DC power into a three-phase signal for driving the phases of the motor 308. The current sensor 324 is configured to, for example, sense the current between the inverter 348 and the motor 308. The temperature sensor is configured to, for example, sense the temperature of the inverter 348. The MS-PLD 350 is configured to, for example, detect a short circuit or line overcurrent event. In some embodiments, the line current (i a and i c ) and DC bus current (I dc ) proportional voltage signal is compared with a predefined threshold to detect short circuit or line overcurrent events.

[0046] The controller 304 includes a plurality of electrical and electronic components that provide power, operational control, and protection for the components and modules within the controller 304 and / or the power tool 100. For example, the controller 304 includes, among other things, a processing unit 352 (e.g., a microprocessor, a microcontroller, or another suitable programmable device), a memory 356, an input unit 360, and an output unit 364. The processing unit 352 includes, among other things, a control unit 368, an arithmetic logic unit ("ALU") 372, and a plurality of registers 376 (in Figure 3 304 is shown as a group of registers) and is implemented using known computer architectures (e.g., modified Harvard architecture, von Neumann architecture, etc.). The processing unit 352, memory 356, input unit 360, output unit 364, and various modules or circuits connected to the controller 304 are connected via one or more control buses and / or data buses (e.g., common bus 380). Figure 3 A control bus and / or a data bus are generally shown for illustration. In view of the invention described in this application, it is known to those skilled in the art to use one or more control buses and / or data buses to achieve interconnection and communication between various modules, circuits and components.

[0047] The memory 356 is a non-transitory computer-readable medium and includes, for example, a program storage area and a data storage area. The program storage area and the data storage area may include a combination of different types of memory, such as ROM, RAM (e.g., DRAM, SDRAM, etc.), EEPROM, flash memory, hard disk, SD card or other suitable magnetic storage device, optical storage device, physical storage device or electronic storage device. The processing unit 352 is connected to the memory 356 and executes software instructions, which may be stored in the RAM of the memory 356 (e.g., during execution), in the ROM of the memory 356 (e.g., usually permanent storage) or in another non-transitory computer-readable medium (e.g., another memory or optical disk). The software included in the embodiment of the power tool may be stored in the memory 356 of the controller 304. The software includes, for example, firmware, one or more applications, program data, filters, rules, one or more program modules and other executable instructions. The controller 304 is configured to retrieve and execute (among other things) instructions related to the control process and method described in the present application from the memory 356. In other constructions, the controller 304 includes additional, fewer, or different components.

[0048] The battery pack interface 312 includes a combination of mechanical components (e.g., rails, slots, latches, etc.) and electrical components (e.g., one or more terminals) that are configured and operable to couple (e.g., mechanically, electrically, and communicatively connect) the power tool 100 to the battery pack. For example, power provided by the battery pack to the power tool is provided to the power input module 340 via the battery pack interface 312. The power input module 340 includes a combination of active and passive components to regulate or control the power received from the battery pack before supplying power to the controller 304. Such components may include a bidirectional Hall effect current sensor that is disposed at the positive terminal of the battery output and is configured to convert the output battery current into an analog voltage input to the MS-PLD 350. The battery pack interface 312 also supplies power to the inverter 348 to selectively supply power to the motor 308 by switching the switching FET.

[0049] The MS-PLD 350 receives a signal corresponding to the inverter / motor line current and compares the DC bus current to a predefined threshold within the MS-PLD 350 to detect, for example, a short circuit or line overcurrent event. Once a fault is detected, the MS-PLD 350 issues a fault signal to the controller 304. The MS-PLD 350 may be a simple or complex mixed-signal PLD, such as an EPROM-based, EEPROM-based, or flash-based mixed-signal PLD.

[0050] The indicator 332 includes, for example, one or more light emitting diodes ("LEDs"). The indicator 332 can be configured to display the status of the power tool or information associated with the power tool. For example, the indicator 332 is configured to indicate a measured electrical characteristic of the power tool, a device condition, etc. One or more user input modules 336 can be operatively coupled to the controller 304, for example, to select a forward operating mode or a reverse operating mode, a torque and / or speed setting for the power tool (e.g., using a torque and / or speed switch), etc. In some specific embodiments, the one or more user input modules 336 can include a combination of digital input or output devices and analog input or output devices required to achieve the desired operating level of the power tool, such as one or more knobs, one or more dials, one or more switches, one or more buttons, etc. In some specific embodiments, the one or more user input modules 336 can receive signals from a device external to the power tool (e.g., a user's mobile phone) wirelessly.

[0051] The controller 304 can be configured to determine whether a fault condition exists in the power tool and to generate one or more control signals associated with the fault condition. For example, the controller 304 can calculate or include in the memory 356 predetermined operating thresholds and limits for the operation of the power tool. For example, when the controller 304 or the MS-PLD 350 detects or predicts a potential thermal failure (e.g., thermal failure of a FET, motor 308, etc.) or an abnormal battery voltage, power to the motor 308 can be limited or interrupted until the possibility of thermal failure is reduced. If the controller 304 detects one or more such fault conditions of the power tool, or determines that the fault condition of the power tool no longer exists, the controller 304 can be configured to provide information and / or control signals to another component of the power tool (e.g., the battery pack interface 312, the indicator 332, etc.). The signal can be configured to, for example, trigger or open a fuse, a reset switch, etc. of the power tool.

[0052] Figure 4 A block diagram of an sFOC hardware topology 400 for a power tool (e.g., power tool 100) is shown. The sFOC hardware topology 400 is Figure 3The exemplary embodiments of the disclosed control system 300, and the introduction of additional filters or the specific embodiments of any further disclosed sensors, electrical components, controllers or power electronics devices do not exclude other embodiments of the control system 300 and electrical components described in this application. The hardware topology 400 includes a battery 404 that powers a microcontroller 408 and a motor 420. The microcontroller 408 is configured to communicate with a gate driver 412 to control a power switching circuit 416 (e.g., an inverter) to drive the motor 420. When the motor 420 rotates, the Hall effect sensor 424 communicates with the microcontroller 408 so that the microcontroller 408 can determine the rotational position of the motor 420. In some specific embodiments, a plurality of Hall effect sensors 424 (e.g., three Hall effect sensors) are used. In some specific embodiments, sensors other than Hall effect sensors can be used. For example, the sensor 424 can be a magnetic sensor, an inductive sensor, a magnetic sine / cosine encoder or an inductive sine / cosine encoder, or other position sensors. Any Hall effect sensor mentioned in this application can be replaced by any of these other types of sensors or position sensors.

[0053] The sFOC hardware topology 400 may also include a plurality of electrical and / or electronic components for sensing, filtering, and processing of electronic signals. For example, the hardware topology 400 includes a battery current sensor 428 (e.g., a bidirectional Hall effect current sensor), a resistive voltage divider 432, a DC bus filter 434, a stator current sensor 436 (e.g., a plurality of resistive current sensing shunts), a plurality of low-pass filters 440, and a mixed signal programmable logic device ("MS-PLD") 444. The DC bus filter 434 is connected in parallel with the battery output and is configured to minimize voltage ripple and power dissipation caused by thermal stress on the DC bus. Therefore, the DC bus filter 434 is configured to increase the operating life of the power tool. The DC bus filter 434 includes one or more of a solid polymer aluminum electrolytic capacitor, a connected solid hybrid aluminum electrolytic capacitor, or a non-solid (wet) aluminum electrolytic capacitor connected in parallel. The capacitors are selected based on their size, voltage rating, ripple current rating, and equivalent series resistance (ESR) to minimize voltage ripple and power dissipation on the DC bus and to maximize operating life under thermal stress.

[0054] The battery current sensor 428 is configured to convert the output battery current from the battery 404 into an analog voltage signal for the MS-PLD 444. The MS-PLD 444 also monitors the filtered current signal from the stator current sensor 436 and compares the signals from the battery current sensor 428 and the stator current sensor 436 to respective thresholds to detect a fault condition (e.g., based on a difference in the monitored values). In some embodiments, the gate driver 412 may also be configured to detect a fault in the power switch circuit 416 (e.g., a faulty transistor, a short circuit, etc.). In some embodiments, compared to Figure 4 As shown, the battery current sensor 428 is located at various locations within the current path of the power tool 100 .

[0055] Next, special attention is paid to the power switch circuit 416, which includes three half-bridges with a total of six power switches. In some embodiments, the power switches are field effect transistors ("FETs"), metal oxide semiconductor field effect transistors ("MOSFETs"). The power switch circuit 416 is configured to convert the DC voltage from the battery 404 into a three-phase voltage with variable amplitude and frequency to drive the motor 420. Each half-bridge includes two power switches (e.g., MOSFETs with anti-parallel [trench or body] diodes), where the two power switches are connected in series in the half-bridge and correspond to a specific phase of the motor 420. In some embodiments, if the power switch current rating is lower than the required application rating, the half-bridges can be connected in parallel (e.g., 6 in the inverter, 2 per phase), thereby forming an inverter with 12 switches. In some embodiments, the power switches can be based on silicon, silicon carbide ("SiC"), or gallium nitride ("GaN"). In some embodiments, the resistive shunt R of the stator current sensor 426 sha and R shc The circuit is placed between two non-adjacent phases of the motor 420 and is configured to dissipate heat equally to a third motor phase located between the two resistor shunts. The shunt is configured to convert the line current into a voltage signal. Thereafter, the two voltage signals proportional to the corresponding line currents are fed to, for example, a common mode low pass filter and a differential mode low pass filter LPF. 1 and LPF 2 After filtering, the signals are provided to the inputs of two differential amplifiers that are rated for high input common-mode voltages and have internal pulse width modulation ("PWM") noise suppression blocks. Once amplified, filtered, and offset by a bias voltage, the voltage signals proportional to the line current are routed to the ADC of the microcontroller 408. The microcontroller 408 then uses these signals to close the current control loop within the microcontroller 408.

[0056] The microcontroller 408 receives signals from the various sensors to, among other things, control the operation of the power tool, monitor the power tool, and actuate one or more indicators 332 (e.g., LEDs) based on the condition of the power tool. For example, the voltage on the DC bus (V dc ) is divided by a high impedance resistor voltage divider. The attenuated signal is connected to one of the inputs of an analog-to-digital converter ("ADC") of the microcontroller 408. The microcontroller 408 is configured to compare the signal from the voltage divider 432 with a predefined threshold stored in the microcontroller to provide overvoltage and undervoltage protection (e.g., monitoring the voltage of the battery 404). The microcontroller 480 is also configured to consider the signal from the voltage divider 432 when controlling the motor 420 to minimize the effects of voltage ripple on the DC bus, and is configured to determine the current trajectory in the case of an MTPV implementation. The microcontroller 408 can also fuse the signals (generated by the Hall effect sensor 424 and the stator current sensor 436) to control the drive of the motor 420. For example, the digital Hall effect sensor signal H a , H b and H c After filtering, the signals are connected from the Hall effect sensor printed circuit board to a digital input (e.g., a general purpose input / output) of the microcontroller 408. These signals are used by the microcontroller 408 to estimate the position and speed of the rotor. Subsequently, the microcontroller 408 is configured to implement a closed-loop sensored field oriented control (sFOC) algorithm using the signals from the Hall effect sensor 424, the voltage divider 432, and the stator current sensor 436. For example, the sFOC algorithm can generate a switching signal (S a+ , S a- , S b+ , S b- , S c+ and S c- ) to drive the motor 420 at a specific speed or torque.

[0057] Figure 5A flow chart of a method 500 for implementing a sensored field oriented control (sFOC) algorithm for a power tool is shown. The sFOC algorithm can be executed by a controller, such as a microcontroller 408 or controller 304 of the power tool 100. At block 505, the method 500 begins, when the controller receives a signal or multiple signals from one or more Hall effect sensors (e.g., Hall effect sensor 424). Subsequently, at block 510, the method 500 uses the signal from the Hall effect sensor to determine a motor parameter. The motor parameter can be, for example, the rotational position of the motor, the speed of the motor, the acceleration of the motor, etc. The microcontroller 408 uses the determined motor parameters (e.g., the speed of the motor) to implement field oriented control. For example, as will be described in detail below, the microcontroller 408 uses the motor parameters determined based on the signal of the Hall effect sensor 424 to determine the drive parameters (e.g., PWM drive parameters) for each phase of the motor 420 using sFOC. In some specific embodiments, the method 500 also includes determining other parameters of the motor 420 or the power tool 100. For example, the method 500 may additionally or alternatively determine torque, temperature, operating time, or another parameter associated with the motor 420 or the power tool 100. At block 520, the microcontroller 408 uses the drive parameters to generate a drive signal for the motor 420. The motor 420 is then driven based on the drive signal (block 525).

[0058] Figure 6 A block diagram of a control system 600 for field oriented control ("sFOC") with sensors implemented by a power tool (e.g., power tool 100) is shown. The control system 600 may be implemented by a controller of the power tool (e.g., controller 304, microcontroller 408, etc.), and may include one or more additional controllers (e.g., dedicated controllers). The control system 600 may also include one or more sensors, and components for receiving signals from the sensors. For example, Figure 6 As shown, the control system 600 includes a battery voltage input block 604, a stator current input block 608, and a Hall effect sensor input block 612. At block 616, by measuring three Hall effect sensor signals (H a , H b , H c ) to determine the rotor speed (w r Then, at block 620, the rotor speed (w r ) is filtered through a low-pass filter to generate a filtered velocity value (w rf). The control system 600 may also receive one or more user inputs. For example, the control system 600 includes a speed command block 624 and a torque command block 628, which are configured to generate speed commands (w respectively) based on the position of the user input (e.g., the trigger 230). cmd ) and directional torque command (i dcmd and i qcmd ). The control system 600 further includes a speed ramp block 632 configured to determine a speed reference (ωrref) based on the speed command and a reference acceleration rate or deceleration rate. Additionally, the speed ramp block 632 determines an acceleration or deceleration torque (Tacc) that may be used by a speed regulator at block 636 to generate a speed control signal i ref In other words, the speed regulator at block 636 is configured to receive a first signal ω corresponding to the current angular velocity of the rotor of the motor (eg, motor 420). rf , and a second signal ωrref corresponding to the target angular velocity of the rotor. Subsequently, the speed regulator at block 636 is configured to be based on the current angular velocity ω rf And refer to the target angular velocity ωrref to generate the stator current signal i ref , to control the stator.

[0059] The control system 600 includes a flux weakening block 640 configured to implement a maximum torque per ampere ("MTPA") algorithm and a maximum torque per volt ("MTPV") algorithm. The flux weakening block 640 is configured to determine a reference direct axis stator current and a quadrature axis stator current (i dref and i qref ), and implements the MTPA algorithm or the MTPV algorithm simultaneously, regardless of whether there is flux weakening operation. The MTPA algorithm is configured to receive the stator current signal i ref , and generates a flux current signal i dref and torque current signal i qref In some embodiments, the MTPA algorithm is configured to determine the MPTA vector (i.e., the MPTA vector is composed of components i d and i q The MTPA algorithm can calculate the MTPA vector again if the MTPA vector is not the minimum current space vector or does not meet the predetermined constraints.

[0060] Additionally, the MTPV algorithm receives the filtered rotor speed (w rf ) and DC bus voltage (V dcf ) Both. Figure 6 As shown, the DC bus voltage (V dcf) passes through a filter 644 (e.g., a low-pass filter) before being input to the flux weakening block 640. The MTPV algorithm also receives, for example, a flux current signal i d , and generate a torque current signal i q . The MTPV algorithm determines a scaling factor based on the angle of the MTPA vector output by the MTPA algorithm. The scaling factor can be between 0 and 1. The algorithm also includes determining the MTPV vector as the product of the MTPA vector and the scaling factor. In some embodiments, the scaling factor is 1. In these embodiments, the MTPV vector is the same as the MTPA vector. The MTPV algorithm can also determine a negative current based on the MTPV vector. In some embodiments, the user can select an output mode of the power tool. Based on the user selection at block 646, the control system 600 can select a torque mode or a speed mode and adjust the reference current used to control the motor accordingly.

[0061] Reference stator current (i dref and i qref ) and the filtered rotor speed (w rf ) is fed to the cross decoupling block 648. The cross decoupling block 648 is configured to calculate the feed forward term (FF d and FF q ), the current regulator can reduce the inherent cross-coupling between the direct axis and the orthogonal axis and achieve independent regulation of the two currents. Using the calculated feedforward term FF d and FF q , the current regulator approaches the respective reference current i at block 652 dref and i qref Adjust the motor's flux current signal and torque current signal i d and i q , and then generate the reference d-axis voltage and reference q-axis voltage V dref and V qref In other words, control system 600 may be configured to adjust the injected stator flux current based on the feed-forward term.

[0062] The current symmetry block 656 is based on two measured currents (i a and i c ) to calculate the third phase current. The current of the third phase of the motor is calculated by using the first motor phase current and the second motor phase current (i a and i c ) is calculated as the negative sum of the currents. Then, at block 660, the control system 600 transforms the motor currents using a direct Clarke transform to decouple and simplify the symmetrical three-phase system into only two currents (i α and iβ ) of a two-phase system. The control system 600 includes a direct Park transform block 664, which is configured to receive a two-phase current signal (i α and i β ) and receiving a signal θ related to the current angular position of the motor rotor from a Hall effect sensor (e.g., Hall effect sensor 328) hall The direct Clarke transformation block 660 is configured to transform a stationary reference frame into a synchronously rotating reference frame. The direct Park transformation block 664 is further configured to transform the stationary reference frame into a synchronously rotating reference frame based on the two-phase current signal i α 、i β and signal θ hall Generate a first current signal i corresponding to the total torque current of the motor q , and a second current signal i corresponding to the total flux current of the motor d .

[0063] In the illustrated embodiment, the control system 600 includes a Hall angle lookup table block 668 and a Hall angular velocity tracking observer block 672. The Hall angle lookup table block 668 is used to calculate the Hall angle based on all three Hall effect sensor signals (H a , H b , H c ) determines the Hall angle (θ DHall ), the Hall angular velocity tracking observer block 672 is configured to determine the angular position signal θ hall In some embodiments, the Hall angular velocity tracking observer block 672 is a phased-locked loop that generates a phase-locked loop based on a discrete Hall angle input (θ DHall ) and directional rotor speed (ω r ) to determine the continuous Hall angle (θ Hall ). In other embodiments, control system 600 may include another method for determining the angular position of the rotor.

[0064] The control system 600 further includes an inverse Park transformation block 676 configured to receive a first signal V corresponding to the flux voltage from the flux controller. d , receiving a second signal V corresponding to the torque voltage from the torque controller q , and receives a signal θ corresponding to the current angular position of the motor rotor from the Hall sensor hall The inverse Park transform block 676 may be configured to generate a hall The first signal V dand the second signal V q Convert to orthogonal stationary reference frame parameter V α and V β Subsequently, the inverse Park transform block 475 is configured to output the orthogonal stationary reference frame parameter V for driving the motor 420 α and V β .

[0065] The control system 600 includes a modulation index calculation block 680 configured to determine the stationary reference frame axis (m α and m β ) and the reverse value (1 / V max ) to determine the reference modulation index (m ref ). In some embodiments, the scaling factor of the MTPV algorithm can be determined by the modulation index calculation block 680. In some embodiments, the modulation index can be adjusted based on other tool parameters (e.g., temperature, battery life, etc.).

[0066] The control system 600 includes a pulse width modulation (“PWM”) block 688 configured to calculate drive parameters or duty cycles (PWM) for each phase of the motor by implementing or combining various PWM strategies (e.g., third harmonic injection, min-max PWM, space vector PWM, discontinuous PWM, etc.). a 、PWM b 、PWM c In some embodiments, the PWM strategy or the combination of PWM strategies is determined by a reference modulation index (m ref ) and the stator frequency. For example, if the reference modulation index requires overmodulation (nonlinear mode) operation, the control system 600 is configured to perform linearization of the overall gain. Once the duty cycle for each phase of the motor is determined, the duty cycle is converted to a register value at block 692 and compared to a continuous up-down counter. At block 692, the control system 600 is configured to generate a drive command or switching signal (S a+ , S a- , S b+ , S b- , S c+ and S c- ) to control a gate driver (eg, gate driver 412 ), which then drives a power switch circuit 416 to drive a motor 420 .

[0067] Thus, the specific embodiments described herein provide systems, devices, and methods for implementing sensored field oriented control in a power tool including a brushless DC motor.The following claims claim various features and advantages.

Claims

1. An electric tool, characterized in that: include: case; a brushless motor disposed in the housing, the brushless motor comprising a rotor and a stator, the rotor coupled to a motor shaft arranged to rotate about a longitudinal axis extending through the motor shaft, the motor shaft arranged to generate a rotational output to a drive mechanism; one or more position sensors disposed adjacent to the brushless motor, the one or more position sensors configured to generate an output signal corresponding to a rotational position of the brushless motor; a power switching circuit configured to provide a power supply from a battery pack to the brushless motor; as well as an electronic controller connected to the one or more position sensors and the power switching circuit, the electronic controller being configured to implement field oriented control ("FOC") of the brushless motor, the electronic controller being configured to: receiving said output signals from said one or more position sensors, determining parameters of the brushless motor based on the output signals from the one or more position sensors, determining drive parameters for the brushless motor based on the parameters of the brushless motor and using FOC, Based on the driving parameters, generating driving instructions, and Based on the driving instruction, the brushless motor is driven.

2. The electric tool according to claim 1, characterized in that: The parameter of the brushless motor includes at least one of a rotational position, a speed, or an acceleration of the brushless motor.

3. The electric tool according to claim 1, characterized in that: The driving parameters of the brushless motor are a plurality of duty cycles for each phase of the motor.

4. The electric tool according to claim 1, characterized in that: The electronic controller is further configured to: A current command is generated by a speed regulator and the output signal from the one or more position sensors.

5. The electric tool according to claim 1, characterized in that: The electronic controller is further configured to: determining a rotor speed based on the output signals from the one or more position sensors; and A speed regulator is used to generate a current command based on the rotor speed and a target speed.

6. The electric tool according to claim 5, characterized in that: The electronic controller is further configured to: determining to operate in a torque mode based on a mode command received via a mode select switch; receiving a torque input command based on a user input; as well as Based on the torque input command, a current command is generated.

7. The electric tool according to claim 1, characterized in that: Further including: a battery pack current sensor, the battery pack current sensor being electrically connected to the battery pack; a stator current sensor electrically connected to the stator of the motor; as well as A mixed signal programmable logic device is in communication with the battery pack current sensor and the stator current sensor, the mixed signal programmable logic device being configured to detect a fault condition.

8. The electric tool according to claim 7, characterized in that: The fault condition is a short circuit condition.

9. The electric tool according to claim 1, characterized in that: The electronic controller is further configured to: determining a first feedforward term and a second feedforward term based on a signal from a stator current sensor and said output signal from said one or more position sensors, The first feedforward term corresponds to the motor speed, and the second feedforward term corresponds to the motor torque.

10. A method for controlling a brushless motor of a handheld power tool, the method comprising: receiving output signals from one or more position sensors; determining a parameter of the brushless motor based on the output signals from the one or more position sensors; determining drive parameters for the brushless motor based on the parameters of the brushless motor and using field oriented control ("FOC"); Based on the driving parameters, generating a driving instruction; as well as Based on the driving instruction, the brushless motor is driven.

11. The method according to claim 10, characterized in that Further including: A current command is generated by a speed regulator and the output signal from the one or more position sensors.

12. The method according to claim 10, characterized in that Further including: determining a rotor speed based on said output signals from said one or more position sensors; as well as A speed regulator is used to generate a current command based on the rotor speed and a target speed.

13. The method according to claim 12, characterized in that Further including: determining to operate in a torque mode based on a mode command received via a mode select switch; receiving a torque input command based on a user input; as well as Based on the torque input command, a current command is generated.

14. The method according to claim 10, characterized in that Further including: determining a first feedforward term and a second feedforward term based on a signal from a stator current sensor and said output signal from said one or more position sensors, The first feedforward term corresponds to the motor speed, and the second feedforward term corresponds to the motor torque.

15. An electric tool, characterized in that: include: case; a brushless motor disposed in the housing, the brushless motor comprising a rotor and a stator, the rotor coupled to a motor shaft arranged to rotate about a longitudinal axis extending through the motor shaft, the motor shaft arranged to generate a rotational output to a drive mechanism; one or more position sensors disposed adjacent to the brushless motor, the one or more position sensors configured to generate an output signal corresponding to a rotational position of the brushless motor; a stator current sensor electrically connected to the stator of the motor and configured to determine a current within at least one phase of the motor; a power switching circuit configured to provide a power supply from a battery pack to the brushless motor; as well as an electronic controller configured to implement field oriented control ("FOC") of the brushless motor, the electronic controller being configured to: receiving said output signals from said one or more position sensors, determining a speed of the brushless motor based on the output signals from the one or more position sensors, determining a first feedforward term and a second feedforward term based on a signal from the stator current sensor and the speed of the brushless motor, wherein the first feedforward term corresponds to the motor speed and the second feedforward term corresponds to the motor torque, generating a driving instruction based on the first feedforward term and the second feedforward term, and Based on the driving instruction, the brushless motor is driven.

16. The electric tool according to claim 15, characterized in that: Further including: a battery pack current sensor, the battery pack current sensor being electrically connected to the battery pack; as well as A mixed signal programmable logic device is in communication with the battery pack current sensor and the stator current sensor, the mixed signal programmable logic device being configured to detect a fault condition.

17. The electric tool according to claim 16, characterized in that: The fault condition is a short circuit condition.

18. The electric tool according to claim 15, characterized in that: The electronic controller is further configured to: A current command is generated by a speed regulator and the output signal from the one or more position sensors.

19. The electric tool according to claim 15, characterized in that: The electronic controller is further configured to: determining a rotor speed based on the output signals from the one or more position sensors; and A speed regulator is used to generate a current command based on the rotor speed and a target speed.

20. The electric tool according to claim 19, characterized in that The electronic controller is further configured to: determining to operate in a torque mode based on a mode command received via a mode select switch; receiving a torque input command based on a user input; as well as Based on the torque input command, a current command is generated.

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