Sensored field oriented control in power tool

Abstract

To solve the problem with the prior art.SOLUTION: 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 output signals 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 the output signals from the one or more position sensors, determine a parameter of the brushless motor based on the output signals, determine drive parameters for the brushless motor based on the parameter of the brushless motor using FOC, generate drive commands based on the drive parameters, and drive the brushless motor based on the drive commands.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] (Technical field) SUMMARY OF THE DISCLOSURE The embodiments described herein relate to power tools that include brushless DC motors. 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 with the correct phase, a conventional brushless DC motor further includes a number of sensors, such as position sensors (e.g., magnetic sensors, Hall effect sensors, inductive sensors, magnetic or inductive sine / cosine encoders, etc.) configured to sense the angular position of the rotor with respect to the stator. To properly generate the magnetic field with the correct phase, one or more control algorithms are used to control the energization of the phases of the stator.

[0004] The embodiments described herein relate to power tools configured to implement sensored field-oriented control (sFOC). In sFOC, both the stator and the rotor generate magnetic flux. In particular, the stator flux current i d and the stator torque current i q is the stator current vector I sare the two component currents that make up the rotor flux. Thus, the stator flux can be determined as a function of the stator current. The goal of sFOC is to align the stator flux orthogonal to the rotor flux. Once the rotor position is known, the power tool controls the phasing of the stator to generate the appropriate magnetic field so that the stator flux remains orthogonal to the rotor flux. Controlling a motor via sFOC offers various advantages, such as independent control of motor speed and motor torque.

[0005] Unlike other control topologies, sFOC does not use one or three low-side shunts to measure DC bus or motor line currents. Instead, sFOC uses two in-line shunts that accurately measure inverter / motor line currents and allow any sampling within the PWM period with solid immunity to PWM noise. In addition, a high-side DC bus current sensor provides robust short-circuit and overcurrent protection for the inverter. As a result, sFOC allows true overcurrent detection on two of the three line currents.

[0006] Also, unlike other control techniques, sFOC estimates rotor speed and continuous rotor angle based on the logical values ​​of position sensor (e.g., digital Hall effect sensor) signals and their transition events (e.g., rising or falling edges) without using any interrupt routines on the microcontroller. As a result, inverter commutation with continuous angles results in sinusoidal stator currents with low harmonic content.

[0007] In addition, unlike the classical block commutation control topology often used in power tools and outdoor power equipment, sFOC exhibits better dynamic and steady-state performance and controllability.

[0008] A power tool as described herein includes a housing, a brushless motor, one or more position sensors, a power switching circuit, and an electronic controller. The brushless motor is disposed within the housing. The brushless motor includes a rotor and a stator. The rotor is coupled to a motor shaft and disposed to rotate about a longitudinal axis. The longitudinal axis extends through the motor shaft. The motor shaft is configured to provide a rotational output to a drive mechanism. The one or more position sensors are disposed proximate to the brushless motor. 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 connected to the one or more position sensors and the power switching circuit, the electronic controller 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, determine parameters of the brushless motor based on the output signals from the one or more position sensors, determine drive parameters of the brushless motor based on the parameters of the brushless motor using FOC, generate drive commands based on the drive parameters, and drive the brushless motor based on the drive commands.

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

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

[0011] In some embodiments, the electronic controller is further configured to generate a current command with output signals from the speed regulator and the 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 with a speed regulator, the current command being based on the rotor speed and the target speed.

[0013] In some aspects, the electronic controller is further configured to determine to operate in a torque mode based on a mode command received through the mode selection switch, receive a torque input command based on a user input, and generate a 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 a stator of the motor, and a mixed signal programmable logic device in communication with the battery pack current sensor and the stator current sensor, the mixed signal programmable logic device 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 signals from the stator current sensors and output signals from the one or more position sensors, the first feedforward term corresponding to motor speed and the second feedforward term corresponding to motor torque.

[0017] A method described herein 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 of the brushless motor based on the parameters of the brushless motor using field-oriented control, generating drive commands based on the drive parameters, and driving the brushless motor based on the drive commands.

[0018] In some embodiments, the method further includes generating a current command at the output signals from the speed regulator and the 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 with a speed regulator, the current command 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 through the mode selection switch, receiving a torque input command based on a user input, and generating a 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 the stator current sensor and an output signal from the one or more position sensors, the first feedforward term corresponding to the motor speed and the second feedforward term corresponding to the motor torque.

[0022] A power tool as described herein 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 disposed within the housing. The brushless motor includes a rotor and a stator. The rotor is coupled to a motor shaft and disposed to rotate about a longitudinal axis. The longitudinal axis extends through the motor shaft. The motor shaft is configured to provide a rotational output to a drive mechanism. The one or more position sensors are disposed proximate to the brushless motor. The one or more position sensors are configured to generate an output signal corresponding to a rotational position of the brushless motor. The stator current sensor is configured to determine a current in at least one phase of the 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 connected to the one or more position sensors and the power switching circuit, the electronic controller 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, determine a speed of the brushless motor based on the output signals from the one or more position sensors, determine a 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 signals from the stator current sensors and the speed of the brushless motor, generate a drive command based on the first feedforward term and the second feedforward term, and drive the brushless motor based on the drive command.

[0023] In some aspects, the power tool further includes a battery pack current sensor electrically connected to the battery pack and a mixed signal programmable logic device in communication with the battery pack 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 embodiments, the electronic controller is further configured to generate a current command with output signals from the speed regulator and the 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 with a speed regulator, the current command being based on the rotor speed and the target speed.

[0027] In some aspects, the power tool is further configured to determine to operate in a torque mode based on a mode command received through the mode selection switch, receive a torque input command based on a user input, and generate a current command based on the torque input command.

[0028] Before describing any embodiment in detail, it should be understood that the embodiments are not limited in their application to the details of the arrangement and configuration of components set forth in the following description or illustrated in the accompanying drawings. The embodiments can be implemented or carried out in various ways. It should also be understood that the usage and terminology used herein is for descriptive purposes and should not be considered limiting. The use of "including," "comprising," or "having," and variations thereof, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless otherwise specified or limited in any other way, the terms "mounted," "connected," "supported," and "coupled," and variations thereof, are used broadly and encompass both direct and indirect mounting, connecting, supporting, and coupling.

[0029] Unless the context of usage clearly indicates otherwise, the articles "a," "an," and "the" should not be construed as meaning "one" or "only one." Rather, these articles should be construed as meaning "at least one" or "one or more." Similarly, unless the context of usage clearly indicates otherwise, when the terms "the" or "said" are used to refer to a noun previously introduced by the indefinite article "a" or "an," "the" and "said" mean "at least one" or "one or more."

[0030] In addition, it should be understood that the embodiments may include hardware, software, and electronic components or modules, which for purposes of discussion may be illustrated and described as if the majority of the components were implemented solely in hardware. However, those skilled in the art will recognize upon reading this detailed description that in at least one embodiment, electronic-based aspects may be implemented in software (e.g., stored in a non-transitory computer-readable medium) executable by one or more processing units, such as a microprocessor and / or an application-specific integrated circuit ("ASIC"). Thus, it should be noted that a number of hardware and software-based devices, as well as a number of different structural components, may be utilized to implement the embodiments. For example, a "server," "computing device," "controller," "processor," etc., as described herein may include one or more processing units, one or more computer-readable media modules, one or more input / output interfaces, and various connections (e.g., a system bus) connecting the components.

[0031] For example, relative terms, such as "about," "approximately," "substantially," and the like, used in connection with an amount or condition, are understood by those of skill in the art as including the stated value and have the meaning dictated by the context (e.g., the term includes at least the degree of error associated with the measurement precision, tolerances [e.g., manufacture, assembly, use, etc.] associated with the particular value). Such terms should also be considered as disclosing a range defined by the absolute values ​​of the two endpoints. For example, the phrase "about 2 to about 4" also discloses a range of "2 to 4." Relative terms may refer to plus or minus a percentage (e.g., 1%, 5%, 10%) of the indicated value.

[0032] While certain figures illustrate hardware and software located within certain devices, it should be understood that these depictions are for illustrative purposes only. Functionality described herein as being performed by one component may be performed by multiple components in a distributed manner. Similarly, functionality performed by multiple components may be integrated and performed by a single component. In some embodiments, the illustrated components may be combined or divided into separate software, firmware, and / or hardware. For example, instead of being located and performed within a single electronic processor, logic and processing may be distributed among multiple electronic processors. Regardless of how they are combined or divided, the hardware and software components may be located on the same computing device or distributed among different computing devices connected by one or more networks or other suitable communication links. Similarly, components described as performing certain functionality may also perform additional functionality not described herein. For example, a device or structure that is "configured" in a particular way may be configured in at least that way, but may also be configured in ways not explicitly recited.

[0033] Thus, in the claims, if an apparatus, method, or system is claimed to include, for example, a controller, control unit, electronic processor, computing device, logic element, module, memory module, communication channel or network, or other elements configured in a particular way, for example, to perform a plurality of functions, the claim or claimed subject matter should be construed to refer to one or more of such elements, in which case the one or more elements, in a set, collectively perform the plurality of functions, such that any one of the one or more elements is configured as claimed to perform any one or more of the recited functions, for example.

[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] 1 illustrates a power tool implementing sensing magnetic field oriented control according to some embodiments.

[0036] [Diagram 2] 1 illustrates a cross-sectional view of a power tool implementing sensing magnetic field oriented control according to some embodiments.

[0037] [Diagram 3] 1 illustrates a control system for a power tool implementing sensing magnetic field oriented control, according to some embodiments.

[0038] [Figure 4] FIG. 1 is a block diagram for a control system of a power tool implementing sensing field oriented control according to some embodiments.

[0039] [Diagram 5] 1 is a flow chart for implementing sensing magnetic field oriented control according to some embodiments.

[0040] [Figure 6] FIG. 1 is a block diagram of a control topology for a power tool implementing sensing magnetic field oriented control according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] The embodiments described herein relate to power tools, such as handheld power tools, that implement sensors direct-current motors ("sensored motors") and sensored field-oriented control ("sFOC").

[0042] FIG 1 illustrates a power tool 100 implementing sFOC. In the embodiment illustrated in FIG 1, the power tool 100 is a drill / driver. In other embodiments, the power tool 100 is a different type of power tool (e.g., impact wrench, ratchet, saw, hammer drill, impact driver, rotary hammer, grinder, blower, trimmer, 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 may be configured to connect the power tool 100 to another device.

[0043] FIG. 2 is a cross-sectional view of the power tool 100 of FIG. 1. 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 instead 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 a sensing motor. Also shown in FIG. 2 is a drive mechanism 215 for transmitting the rotational output of the motor 210 to an output unit 220, as well as a cooling fan 225 that is rotated by the motor 210 and used to provide a flow of cooling air over 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 embodiments, an amount of actuation of the trigger 230 may be used to determine the amount of power provided to the motor 210. The power tool 100 may further include a work light 235 configured to illuminate a work area of ​​the power tool 100. In some embodiments, the work light 235 may be mounted below the drive mechanism 215. In some embodiments, the work light 235 may be configured to be activated in response to actuation of the trigger 230.

[0044] 3 illustrates a control system 300 for a power tool (e.g., power tool 100 of FIG. 1) that implements sensing magnetic field oriented control. The control system 300 includes a controller 304. The controller 304 is electrically and / or communicatively connected to various modules or components of the power tool. For example, the illustrated controller 304 is electrically connected to a motor 308 (e.g., motor 210 of FIG. 2), a battery pack interface 312 (e.g., battery pack interface 110 of FIG. 1), a trigger switch 316 (connected to trigger 320, e.g., trigger 230 of FIG. 2), one or more sensors including at least a current sensor 324, a position sensor (e.g., a magnetic sensor, a Hall effect sensor, an inductive sensor, a magnetic or inductive sine / cosine encoder, etc.) 328, 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 operable to, among other things, control operation of the power tool, monitor operation of the power tool, and activate one or more indicators 332 (e.g., LEDs). The gate controller 344 is configured to control the inverter 348 to convert a DC power source into a three-phase signal for powering the phases of the motor 308. The current sensor 324 is configured to sense a current between the inverter 348 and the motor 308, for example. The temperature sensor is configured to sense a temperature of the inverter 348, for example. The MS-PLD 350 is configured to detect, for example, a short circuit or a line overcurrent event. In some embodiments, the line current (i a and i c ) and DC bus current (I dc ) is compared to a predetermined threshold inside the MS-PLD 444 to detect a short circuit or line overcurrent event.

[0046] The controller 304 includes a number of electrical and electronic components that provide power, operational control, and protection to the controller 304 and / or components and modules within the power tool 100. For example, the controller 304 includes, among other things, a processing unit 352 (e.g., a microprocessor, 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 number of registers 376 (shown as a group of registers in FIG. 3) 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, and output unit 364, as well as the various modules or circuits connected to the controller 304, are connected by one or more control buses and / or data buses (e.g., a common bus 380). The control buses and / or data buses are shown generally in FIG. 3 for illustrative purposes. The use of one or more control buses and / or data buses for interconnecting and communicating between the various modules, circuits, and components will be known to those of skill in the art in view of the invention described herein.

[0047] The memory 356 is a non-transitory computer-readable medium, including, 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, optical, physical, or electronic memory devices. 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., on a more or less permanent basis), or in another memory or another non-transitory computer-readable medium, such as a disk. Software included in the implementation 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 instructions from the memory 356, which are related to, among other things, the control processes and methods described herein. In other configurations, the controller 304 includes additional components, fewer components, or different components.

[0048] The battery pack interface 312 is The battery pack interface 312 includes a combination of mechanical (e.g., rails, grooves, latches, etc.) and electrical (e.g., one or more terminals) components configured and operable to interface (e.g., mechanically, electrically, and communicatively connect) the power tool 100 with the battery pack. For example, power provided to the power tool by the battery pack is provided to the power input module 340 through the battery pack interface 312. The power input module 340 includes a combination of active and passive components to regulate or control the power it receives from the battery pack before the power is provided to the controller 304. One such component may include a bidirectional Hall effect current sensor disposed at the positive terminal of the battery output and configured to convert the output battery current to an analog voltage that is input to the MS-PLD 350. The battery pack interface 312 also provides power to an inverter 348 to be switched by a switching FET to selectively provide power to the motor 308.

[0049] The MS-PLD 350 receives signals corresponding to the inverter / motor line currents, and the DC bus currents are compared to predetermined thresholds inside the MS-PLD 350 to detect, for example, a short circuit or a line overcurrent event. Upon detecting a fault, the MS-PLD 350 signals the fault to the controller 304. The MS-PLD 350 can be, for example, an EPROM, EEPROM, or Flash-based complex mixed-signal PLD or a simple mixed-signal PLD.

[0050] The indicators 332 may include, for example, one or more light emitting diodes ("LEDs"). The indicators 332 may be configured to display the status of the power tool or related information of the power tool. For example, the indicators 332 may be configured to indicate a measured electrical characteristic of the power tool, a device status, etc. One or more user input modules 336 may be operably coupled to the controller 304 to, for example, select a forward or 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 embodiments, the one or more user input modules 336 may include a combination of digital and analog input or output devices required to achieve a desired level of operation for the power tool, such as one or more knobs, one or more dials, one or more switches, one or more buttons, etc. In some embodiments, the one or more user input modules 336 may receive signals wirelessly from a device external to the power tool (e.g., the user's cell phone).

[0051] The controller 304 may be configured to determine whether a fault condition of the power tool exists and generate one or more control signals associated with the fault condition. For example, the controller 304 may calculate or include in the memory 356 predetermined operating thresholds and limits for operation of the power tool. For example, if a potential thermal fault (e.g., of the FET, motor 308, etc.) or abnormal battery voltage is detected or predicted by the controller 304 or the MS-PLD 350, power to the motor 308 may be limited or interrupted until the likelihood of a thermal fault is reduced. If the controller 304 detects one or more such fault conditions of the power tool or determines that a fault condition of the power tool no longer exists, the controller 304 may 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 signals may be configured to, for example, trip or open a fuse or reset a switch of the power tool.

[0052] FIG. 4 illustrates a block diagram of an sFOC hardware topology 400 for a power tool (e.g., power tool 100). The sFOC hardware topology 400 is an exemplary implementation of the control system 300 disclosed in FIG. 3, and incorporating additional filters or specific implementations of any sensors, electrical components, controllers, or power electronics as further disclosed does not preclude other implementations of the control system 300 and electrical components disclosed herein. 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. As the motor 420 rotates, a 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 embodiments, multiple Hall effect sensors 424 (e.g., three Hall effect sensors) are implemented. In some embodiments, sensors other than Hall effect sensors can be used. For example, sensor 424 can be a magnetic sensor, an inductive sensor, a magnetic or inductive sine / cosine encoder, or other position sensor. Any references herein to the use of Hall effect sensors can be replaced with any of these other types of sensors or position sensors.

[0053] The sFOC hardware topology 400 may include multiple electric and / or electronic components for sensing, filtering, and processing electrical 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., multiple resistive current sensing shunts), multiple 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 configured to minimize voltage ripple and power dissipation across the DC bus due to thermal stress on the DC bus. Thus, the DC bus filter 434 is configured to improve 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 according to their size, voltage rating, ripple current rating, and equivalent series resistance to minimize voltage ripple and power dissipation across the DC bus and provide sufficient operating life given thermal stresses.

[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 (e.g., based on differences in the monitored values) to detect a fault condition. In some embodiments, the gate driver 412 may be configured to detect faults (e.g., failed transistors, short circuits, etc.) in the power switching circuit 416. In some embodiments, the battery current sensor 428 is located in a location in the current path of the power tool 100 different than the location shown in FIG. 4 .

[0055] Paying particular attention to the power switching circuitry 416, the power switching circuitry 416 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 FETs ("MOSFETs"). The power switching circuitry 416 is configured to convert the DC voltage from the battery 404 into a three-phase voltage of 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), with both power switches in a half bridge connected in series and corresponding to a particular phase of the motor 420. In some embodiments, if the power switch current rating is below the required application rating, the half bridges can be paralleled (e.g., two per phase, six in the inverter), resulting in a twelve switch inverter. In some embodiments, the power switches can be silicon-based, silicon carbide ("SiC")-based, or gallium nitride ("GaN")-based. In some embodiments, the resistive shunt R of the stator current sensor 436 sha and R shc are arranged between two non-adjacent phases of the motor 420 and are configured to dissipate heat equally to a third motor phase arranged between two resistive shunts. The shunts are configured to convert the line currents to voltage signals. Two voltage signals proportional to the corresponding line currents are then sent to, for example, common-mode and differential-mode low-pass filters LPF1 and LPF2. After being filtered, the signals are provided to the inputs of two differential amplifiers rated for high input common-mode voltages with an inner pulse-width modulation (PWM) noise rejection block. Once amplified, filtered, and shifted by an offset voltage, the voltage signals proportional to the line currents are routed to the ADC of the microcontroller 408. The microcontroller 408 then uses these signals to close its inner current control loop.

[0056] The microcontroller 408 receives signals from various sensors to, among other things, control the operation of the power tool, monitor the power tool, and activate one or more indicators 332 (e.g., LEDs) based on the status of the power tool. For example, the voltage across the DC bus (V dc ) is divided with a high impedance resistive 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 within the microcontroller to provide over-voltage and under-voltage protection (e.g., monitoring the voltage of the battery 404). The microcontroller 480 is configured to take into account the signal from the voltage divider 432 to determine the current trajectory in case of MTPV implementation when controlling the motor 420 to minimize the effect of voltage ripple across the DC bus. The microcontroller 408 may incorporate 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 are filtered and connected from the Hall effect sensor printed circuit board to digital inputs (e.g., general input / output) of the microcontroller 408. These signals are used by the microcontroller 408 to estimate the rotor position and speed. The microcontroller 408 is then configured to implement a closed-loop sensored field-oriented control (sFOC) algorithm using signals from the Hall effect sensors 424, the voltage divider 432, and the stator current sensor 436. For example, the sFOC algorithm may generate switching signals (S a+ , S a- , S b+ , S b- , S c+ , and S c-) may be generated to drive the motor 420 at a particular speed or torque.

[0057] FIG. 5 illustrates a flow chart of a method 500 for implementing a sensing field oriented control (sFOC) algorithm for a power tool. The sFOC algorithm may be executed by a controller, such as the microcontroller 408 or the controller 304 of the power tool 100. The method 500 begins when the controller receives a signal or signals from one or more Hall effect sensors (e.g., the Hall effect sensors 424) at block 505. The method 500 then determines a motor parameter at block 510 using the signal from the Hall effect sensor. The motor parameter may be, for example, a rotational position of the motor, a speed of the motor, an acceleration of the motor, etc. The microcontroller 408 uses the determined parameter of the motor (e.g., the speed of the motor) to implement the field oriented control. For example, as described in more detail below, the microcontroller 408 uses the parameter of the motor determined based on the signal from the Hall effect sensor 424 to determine a drive parameter (e.g., a PWM drive parameter) using sFOC for each phase of the motor 420. In some embodiments, the method 500 may also include determining other parameters of the motor 420 or the power tool 100. For example, the method 500 may additionally or alternatively determine a 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] FIG. 6 illustrates a block diagram of a control system 600 of a sensing field oriented control ("sFOC") algorithm implemented by a power tool (e.g., power tool 100). The control system 600 can be implemented by a controller (e.g., controller 304, microcontroller 408, etc.) of the power tool and may include one or more additional controllers (e.g., dedicated controllers). The control system 600 also includes one or more sensors and components for receiving signals from the sensors. For example, as shown in FIG. 6, 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. The period of the signal from the Hall effect sensor is related to the rotor speed (w r ) to determine the three Hall effect sensor signals (H a , H b , H c ) is measured in block 616. The rotor speed (w r ) is filtered through a low pass filter in block 620 to obtain the filtered velocity value (w rf The control system 600 may also receive one or more user inputs. For example, the control system 600 may generate a velocity command (w cmd ) and the directional torque command (i dcmd and i qcmd ), respectively. 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 or deceleration rate. In addition, the speed ramp block 632 determines a speed control signal i ref In other words, the speed regulator in block 636 determines an acceleration or deceleration torque (Tacc) that can be used by the speed regulator in block 636 to generate a first signal ω rfand a second signal ωrref corresponding to a target angular velocity for the rotor. Next, the speed regulator in block 636 is configured to receive the stator current signal i ref and calculate the current angular velocity ω by referencing the target angular velocity ωrref. rf The stator is configured to control the stator based on the

[0059] The control system 600 includes a flux weakening block 640 configured to implement a max-torque-per-amps (MTPA) algorithm and a max-torque-per-volts (MTPV) algorithm. The flux weakening block 640 adjusts the reference direct and quadrature axis stator currents (i dref and i qref The MTPA algorithm is configured to receive the stator current signal iref and determine the flux current signal i dref and the torque current signal i qref In some embodiments, the MTPA algorithm is configured to generate an MPTA vector (i.e., components i d and i q The MTPA algorithm may be configured to determine whether the MPTA vector (the resulting vector produced by the MTPA vector) is a minimum current space vector. In addition, the MTPA algorithm may recalculate the MPTA vector if the MTPA vector is not a minimum current space vector or does not otherwise satisfy certain constraints.

[0060] The MTPV algorithm also uses the filtered rotor speed (w rf ) and DC bus voltage (V dcf ) as shown in Figure 6. dcf) is passed through a filter 644 (e.g., a low pass filter) before being input to the flux weakening block 640. The MTPV algorithm also uses, for example, d Receive the 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 may 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 may also determine a negative current based on the MTPV vector. In some embodiments, the user may select a power mode for the power tool. Based on the user selection at block 646, the control system 600 may select a torque mode or a speed mode and may 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 a cross-decoupling block 648. The cross-decoupling block 648 includes feed-forward terms (FF d and F.F. q ) calculated in block 652. d and F.F. q Using the current regulator, the motor flux and torque current signals i d and i q The respective reference currents i dref and i qref , thereby adjusting the reference d-axis and q-axis voltages Vd ref and Vqref In other words, the control system 600 may be configured to adjust the injected stator flux current based on the feedforward term.

[0062] The current symmetry block 656 is a block for measuring two currents (i a and i c ) The current in the third phase of the motor is calculated based on the value of the first motor phase current and the second motor phase current (i a and i c ) in the motor currents. Next, in block 660, the control system 600 transforms the motor currents using a direct Clarke transformation to decouple the symmetrical three-phase system and to obtain two currents (i α and i β ) from the direct Clarke transform block 660. α and i β ) and a signal θ from a Hall effect sensor (e.g., Hall effect sensor 328) regarding the current angular position of the rotor of the motor. hall The direct Clarke transform block 660 is configured to transform the fixed reference frame into a synchronous rotating reference frame. The direct Park transform block 664 includes a direct Park transform block 664 configured to receive the two-phase current signal i α , i β and signal θ hall A first current signal i corresponding to the total torque current of the motor is generated based on q and a second current signal i corresponding to the total flux current of the motor. d The device is further configured to generate:

[0063] In the illustrated embodiment, the control system 600 controls all three Hall effect sensor signals (H a , H b , H c ) based on the logical value of the hole angle (θ DHall ) and a Hall angle lookup table block 668 that is used to determine discrete (e.g., step-changed) values ​​of the angular position signal θhall In some embodiments, the Hall angular rate tracking observer block 672 includes a Hall angular rate tracking observer block 672 configured to determine a discrete Hall angle input (θ DHall ) and directional rotor speed (ω r ) based on the continuous hole angle (θ Hall ) In other embodiments, the control system 600 may include other methods for determining the angular position of the rotor.

[0064] The control system 600 receives a first signal V from the flux controller, which corresponds to the flux voltage. d , a second signal V from the torque controller corresponding to the torque voltage q , and a signal θ corresponding to the current angular position of the motor's rotor from the Hall sensor. hall The inverse Park transform block 676 further includes an inverse Park transform block 676 configured to receive the first signal V d and a second signal V q Let the signal θ hall Based on the orthogonal fixed reference frame quantity V α and V β Next, the inverse Park transform block 475 converts the orthogonal fixed reference frame quantities V α and V β The apparatus is configured to output:

[0065] The control system 600 includes a modulation index calculation block 680 configured to determine a reference modulation index (mref) based on the modulation index on the fixed reference frame axes (mα and mβ) and the inverse of the maximum fundamental stator voltage (1 / Vmax) determined by a maximum reverse voltage block 684. In some embodiments, a scaling factor for the MTPV algorithm may be determined by the modulation index calculation block 680. In some embodiments, the modulation index may be adjustable according to other tool parameters (e.g., temperature, battery life, etc.).

[0066] The control system 600 controls the drive parameters or duty cycle (PWM) for each phase of the motor through the implementation or mixture of various PWM strategies (e.g., third harmonic injection, min-max, space-vector pulse width modulation, discontinuous pulse width modulation, etc.). a , PWM b , PWM c The control system 600 includes a pulse width modulation ("PWM") block 688 configured to calculate a duty cycle (S) that is used to control a gate driver (e.g., gate driver 412) to drive a gate driver (e.g., gate driver 412) using the comparison register values ​​and counters. In some embodiments, the PWM strategy or combination of PWM strategies is determined by a reference modulation index (mref) and a stator frequency. For example, if the reference modulation index requires overmodulation (nonlinear mode) operation, the control system 600 is configured to perform an overall gain linearization. After determining the duty cycle for each phase of the motor, the duty cycle is converted to a register value in block 692 and compared to a continuous up-down counter. The control system 600 in block 692 uses the comparison register values ​​and counters to generate drive commands or switching signals (S) that are used to control a gate driver (e.g., gate driver 412). a+ , S a- , S b+ , S b- , S c+ , and S c- ), and the gate driver is configured to in turn drive the power switching circuit 416 to drive the motor 420. do.

[0067] Thus, the embodiments described herein provide systems, devices, and methods for implementing sensing field oriented control in a power tool including a brushless DC motor. Various configurations and advantages are set forth in the following claims.

Claims

1. Housing and a brushless motor disposed within the housing, the brushless motor including a rotor and a stator, the rotor coupled to a motor shaft disposed to rotate about a longitudinal axis, the longitudinal axis extending through the motor shaft, the motor shaft disposed to provide a rotational output to a drive mechanism; one or more position sensors disposed proximate to the brushless motor and configured to generate an output signal corresponding to a rotational position of the brushless motor; a power switching circuit configured to provide a supply of power from a battery pack to the brushless motor; an electronic controller coupled to the one or more position sensors and the power switching circuitry and configured to implement field oriented control (FOC) of the brushless motor; The electronic controller includes: receiving the output signals from the 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 using the FOC; generating a drive command based on the drive parameters; and driving the brushless motor based on the drive command. Power tools.

2. The power tool of claim 1 , wherein the parameters of the brushless motor include at least one of a rotational position, a speed, or an acceleration of the brushless motor.

3. The power tool of claim 1 , wherein the operating parameters of the brushless motor are a number of duty cycles for each phase of the brushless motor.

4. The electronic controller includes: generating a current command with the output signals from a speed regulator and the one or more position sensors.

2. The power tool of claim 1.

5. The electronic controller includes: determining a rotor speed based on the output signals from the one or more position sensors; generating a current command using a speed regulator; The current command is based on the rotor speed and a target speed.

2. The power tool of claim 1.

6. The electronic controller includes: determining to operate in a torque mode based on a mode command received through a mode selection switch; receiving a torque input command based on a user input; generating a current command based on the torque input command.

6. The power tool of claim 5.

7. a battery pack current sensor electrically connected to the battery pack; a stator current sensor electrically connected to the stator of the brushless motor; a mixed signal programmable logic device in communication with the battery pack current sensor and the stator current sensor; the mixed signal programmable logic device is configured to detect a fault condition; 2. The power tool of claim 1.

8. The power tool of claim 7 , wherein the fault condition is a short circuit condition.

9. The electronic controller includes: determining a first feedforward term and a second feedforward term based on a signal from a stator current sensor and the output signal from the one or more position sensors; the first feedforward term corresponds to motor speed and the second feedforward term corresponds to motor torque; 2. The power tool of claim 1.

10. 1. A method for controlling a brushless motor of a handheld power tool, comprising: 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 using field-oriented control (FOC); generating a drive command based on the drive parameters; Driving the brushless motor based on the drive command. method.

11. The method of claim 10 further comprising generating a current command with the output signals from a speed regulator and the one or more position sensors.

12. determining a rotor speed based on the output signals from the one or more position sensors; generating a current command with a speed regulator; the current command is based on the rotor speed and a target speed; The method of claim 10.

13. determining to operate in a torque mode based on a mode command received through a mode selection switch; receiving a torque input command based on a user input; generating a current command based on the torque input command. The method of claim 12.

14. 11. The method of claim 10, further comprising determining a first feedforward term and a second feedforward term based on a signal from a stator current sensor and the output signal from the one or more position sensors, the first feedforward term corresponding to motor speed and the second feedforward term corresponding to motor torque.

15. Housing and a brushless motor disposed within the housing, the brushless motor including a rotor and a stator, the rotor coupled to a motor shaft disposed to rotate about a longitudinal axis, the longitudinal axis extending through the motor shaft, the motor shaft disposed to provide a rotational output to a drive mechanism; one or more position sensors disposed proximate to the brushless motor and configured to generate an output signal corresponding to a rotational position of the brushless motor; a stator current sensor electrically coupled to the stator of the brushless motor and configured to determine a current in at least one phase of the brushless motor; a power switching circuit configured to provide a supply of power from a battery pack to the brushless motor; an electronic controller configured to implement field-oriented control (FOC) of the brushless motor; The electronic controller includes: receiving the output signals from the 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; generating a drive command based on the first feedforward term and the second feedforward term; driving the brushless motor based on the drive command; It is configured as follows: the first feedforward term corresponds to motor speed and the second feedforward term corresponds to motor torque; Power tools.

16. a battery pack current sensor electrically connected to the battery pack; a mixed signal programmable logic device in communication with the battery pack current sensor and the stator current sensor; the mixed signal programmable logic device is configured to detect a fault condition; 16. The power tool of claim 15.

17. The power tool of claim 16, wherein the fault condition is a short circuit condition.

18. The electronic controller includes: generating a current command with the output signals from a speed regulator and the one or more position sensors.

16. The power tool of claim 15.

19. The electronic controller includes: determining a rotor speed based on the output signals from the one or more position sensors; generating a current command using a speed regulator; the current command is based on the rotor speed and a target speed; 16. The power tool of claim 15.

20. The electronic controller includes: determining to operate in a torque mode based on a mode command received through a mode selection switch; receiving a torque input command based on a user input; generating a current command based on the torque input command.

20. The power tool of claim 19.

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