Flux braking in a power tool

Abstract

A power tool comprising a housing, a handle, and a brushless motor within the housing. The brushless motor includes a rotor and a stator. The power tool further includes a sensor that senses a parameter of the brushless motor, a power circuit configured to supply power to the brushless motor from a power source, and an electronic controller that controls the brushless motor using a field-oriented control ("FOC") technique. The electronic controller is configured to receive, via the sensor, a first signal indicative of a braking operation of the brushless motor, generate a second signal to control a first component of a brushless motor current to brake the brushless motor, and generate a third signal to control a second component of a brushless motor current to brake the brushless motor.

Description

Related applications

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 480,121, filed January 17, 2023, and U.S. Provisional Patent Application No. 63 / 381,858, filed November 1, 2022, the entire contents of which are hereby incorporated by reference. Area

[0002] The embodiments described here refer to power tools. Overview of the invention

[0003] Conventional brushless DC motors consist of a stator and a rotor configured to rotate relative to the stator by a magnetic field generated in one or more phases of the stator. Typically, the stator and rotor are separated by an air gap. To generate the magnetic field in the correct phase(s), conventional brushless DC motors also include a sensor, such as a Hall-effect sensor, configured to detect the angular position of the rotor relative to the stator. Some brushless DC motors do not include this sensor. These motors are called sensorless brushless DC motors (or simply "sensorless motors"). To generate the magnetic field in the correct phase(s), motors can use one or more control algorithms to estimate the rotor position and control the stator phases.One such control algorithm is field-oriented control (“FOC”).

[0004] In FOC, both the stator and rotor generate a flux. The stator flux current, i d , and the stator torque current, i q , are in particular two components of the current that determine the stator current vector, I s, in a rotating reference frame. Therefore, the stator flux can be determined as a function of the stator current. The goal of FOC is to align the stator flux so that it is orthogonal to the rotor flux. To achieve this, motors may incorporate devices for measuring the stator current, such as shunt resistors, to determine the position of the rotor. Once the position of the rotor is known, motors can control the phases of the stator so that the correct magnetic field is generated and the stator flux remains orthogonal to the rotor flux. Controlling a motor via FOC offers several advantages, such as independent control of motor speed and motor torque.

[0005] For motors with FOC, the motor can be actively braked by reducing the stator flux current, i d , separated from the stator torque current, i q, is controlled. This is referred to here as flux braking. Flux braking increases the magnetic flux of the motor by actively controlling the stator flux current, i d , and the stator torque current, i q For example, the energy from motor braking is absorbed in the motor itself in the form of heat from the magnetizing current. In some motor braking applications, the energy can be stored in a battery, a process commonly referred to as regenerative braking.

[0006] To prevent regenerative currents, dynamic braking techniques are used. Dynamic braking techniques utilize the motor control circuit breakers to absorb energy or incorporate separate resistive elements within the brushless motor to absorb energy. For brushless motors operating with batteries of widely varying capacities, the regenerative current to the battery may exceed the safe charging rate for lower-capacity batteries. Flux braking utilizes the brushless motor, which is designed for high currents, to absorb braking energy and prevent regenerative currents without the use of separate energy-absorbing elements. In some examples, this requires the brushless motor to decelerate slowly to keep the regenerative current at a low level.The implementation of flux braking enables tunable braking control through feedback mechanisms to control the stator flux current, i. d The flux braking control can be customized to achieve short braking times without regenerative currents, or the flux braking can be set to a longer duration for controlled deceleration for loads with greater inertia. Flux braking also does not require switches (e.g., FETs, drive switches, etc.) or other devices to protect the battery during braking.

[0007] The embodiments described herein provide a flux braking power tool. More specifically, the embodiments described herein provide a power tool comprising a housing, a handle, a brushless motor within the housing, the brushless motor including a rotor and a stator, the rotor coupled to a motor shaft arranged to rotate about a longitudinal axis, the longitudinal axis extending through the motor shaft, and the motor shaft arranged to provide a rotational output to a drive mechanism, a sensor configured to detect a parameter of the brushless motor, and a power circuit configured to supply power to the brushless motor from a power source.The power tool further includes an electronic control unit configured to control the brushless motor using a field-oriented control ("FOC") technique. The electronic control unit is configured to receive, via the sensor, a first signal indicative of a braking operation of the brushless motor, generate a second signal to control a first component of the brushless motor current to brake the brushless motor, and generate a third signal to control a second component of the brushless motor current to brake the brushless motor.

[0008] In some aspects, the electronic controller is further configured to, in response to the third signal, determine whether the third signal is sufficient to brake the brushless motor, and, in response to determining that the third signal is insufficient, generate a fourth signal to control the second component of the current, wherein the fourth signal is different from the third signal.

[0009] In some aspects, the first component of the current shows a torque-generating current (i q ).

[0010] In some aspects, the second component of the current shows a flux-generating current (i d ).

[0011] In some aspects, generating the third signal to control the second component of the current includes the electronic control unit being configured to control the second component of the current to have a positive magnitude.

[0012] In some aspects, generating the second signal to control the first component of the current includes the electronic control unit being configured to control the first component of the current to zero.

[0013] In some aspects, the electronic controller is further configured to determine the battery voltage when decelerating the brushless motor, determine the battery current when decelerating the brushless motor, determine the speed of the brushless motor when decelerating the brushless motor, and provide the fourth signal to the brushless motor based on at least one of the group consisting of the battery voltage, the battery current, and the speed.

[0014] The embodiments described herein provide a method for controlling a power tool. The method includes receiving a first signal indicative of a braking operation of a brushless motor via a sensor, generating a second signal for controlling a first component of a brushless motor current to brake the brushless motor, and generating a third signal for controlling a second component of the brushless motor current to brake the brushless motor.

[0015] In some aspects, the methods described herein further include, in response to the third signal, determining whether the third signal is sufficient to brake the brushless motor, and providing a fourth signal to the brushless motor in response to determining that the third signal is insufficient to control the second component of the current, wherein the fourth signal is different from the third signal.

[0016] In some aspects, the first component of the current shows a torque-generating current (i q ).

[0017] In some aspects, the second component of the current shows a flux-generating current (i d ).

[0018] In some aspects, applying the third signal controls the second component of the current to have a positive magnitude.

[0019] In some aspects, supplying the second signal to the brushless motor to control the first component of the current includes controlling the first component of the current to be zero.

[0020] In some aspects, the methods described herein further include determining a battery voltage while braking the brushless motor, determining a battery current while braking the brushless motor, determining a speed of the brushless motor while braking the brushless motor, and providing the fourth signal to the brushless motor based on at least one of the group consisting of the battery voltage, the battery current, and the speed.

[0021] The embodiments described herein provide a power tool that enables flux braking and subsequent driving action. In particular, the embodiments described herein provide a power tool comprising a housing, a handle, a brushless motor within the housing, the brushless motor including a rotor and a stator, the rotor coupled to a motor shaft arranged to rotate about a longitudinal axis, the longitudinal axis extending through the motor shaft, and the motor shaft arranged to provide a rotational output to a drive mechanism, a sensor configured to detect a parameter of the brushless motor, and a power circuit configured to supply power to the brushless motor from a power source.The power tool further includes an electronic control unit configured to control the brushless motor using a field-oriented control ("FOC") technique. The electronic control unit is configured to receive, following flux braking of the brushless motor and via the sensor, a first signal indicative of a drive operation of the brushless motor, generate a second signal to control a first component of a brushless motor current to drive the brushless motor, and generate a third signal to control a second component of the brushless motor current to drive the brushless motor.

[0022] In some aspects, the first component of the current shows a torque-generating current (i q ).

[0023] In some aspects, the second component of the current shows a flux-generating current (i d ).

[0024] In some aspects, generating the third signal includes the electronic control unit being configured to reduce the second component of the current to zero.

[0025] In some aspects, reducing the second component to zero maximizes the torque delivered by the brushless motor.

[0026] In some aspects, the electronic control unit is also configured to receive a user input and, in response to the user input, to decelerate the brushless motor.

[0027] Before any embodiments are explained in detail, it is to be understood that the embodiments are not limited in their application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The embodiments may be otherwise implemented and practiced. It is also to be understood that the phraseology and terminology used herein is for the purpose of description and should not be considered limiting. The use of "including," "comprising," or "having" and variations thereof is intended to encompass the elements listed below and their equivalents as well as additional elements.Unless otherwise specified or limited, the terms “attached,” “connected,” “held,” and “coupled,” and their variations, are used in their broadest sense and include both direct and indirect attachments, connections, supports, and couplings.

[0028] Unless the context of their use clearly indicates otherwise, the articles "ein," "eine," and "der" should not be interpreted to mean "one" or "only one." Rather, these articles should be interpreted to mean "at least one" or "one or more." When the terms "der" or "said" are used to refer to a noun previously introduced by the indefinite article "ein" or "eine," "der" and "said" also mean "at least one" or "one or more," unless the usage clearly indicates otherwise.

[0029] Furthermore, it is understood that embodiments may include hardware, software, and electronic components or modules, which for explanatory purposes may be illustrated and described as if the majority of the components were implemented solely in hardware. However, one of ordinary skill in the art will recognize upon reading this detailed description that, in at least one embodiment, the electronically based aspects may be implemented in software (e.g., stored on a non-transitory, computer-readable medium) that may be executed by one or more processing units, such as a microprocessor and / or application-specific integrated circuits ("ASICs").It should therefore be appreciated that a variety of hardware- and software-based devices, as well as a variety of different structural elements, may be used to implement the embodiments. For example, the "servers," "computing devices," "controllers," "processors," etc., discussed in the specification 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) that interconnect the components.

[0030] Relative terms such as "approximately," "approximately," "substantially," etc., used in connection with a quantity or condition, will be understood by those skilled in the art to include the stated value and to have the meaning given by the context (e.g., the term includes at least the degree of error associated with the accuracy of measurement, the tolerances associated with the particular value [e.g., manufacturing, application, use, etc.], etc.). Such terminology should also be considered to disclose the range defined by the absolute values ​​of the two endpoints. For example, the phrase "from about 2 to about 4" also indicates the range "from 2 to 4." Relative terminology may refer to plus or minus a percentage (e.g., 1%, 5%, 10%) of a stated value.

[0031] It should be understood that although certain drawings depict hardware and software in particular devices, these depictions are for illustrative purposes only. Functions described herein as being performed by one component may be performed by multiple components in a distributed manner. Likewise, functions performed by multiple components may be consolidated and performed by a single component. In some embodiments, the depicted components may be combined or separated into separate software, firmware, and / or hardware. For example, rather than being housed in and executed by a single electronic processor, logic and processing may be distributed among multiple electronic processors.Regardless of how they are combined or distributed, the hardware and software components may be located on the same computing device or distributed among different computing devices interconnected by one or more networks or other suitable communications links. Similarly, a component that performs a particular function may also perform additional functions not described herein. A device or structure that is "configured" in a particular manner is at least configured in that manner, but may also be configured in a manner not explicitly listed.

[0032] Where the claims claim that an apparatus, method or system comprises, for example, a controller, control unit, electronic processor, computing device, logic element, module, memory module, communication channel or network or other element arranged in a particular way, for example to perform multiple functions, the claim or claim element should be interpreted as designating one or more such elements, each of the one or more elements arranged as claimed, for example to perform one or more of the specified multiple functions, so that the one or more elements as a set jointly perform the multiple functions.

[0033] Further aspects of the embodiments will become apparent upon consideration of the detailed description and the accompanying drawings. Short description of the drawings Fig. 1 shows a power tool utilizing flux braking, according to some embodiments. Fig. 2 shows a cross-sectional view of a power tool with flux braking according to some embodiments. Fig. 3 shows a control system for a power tool with flux braking, according to some embodiments. Fig. 4 is a block diagram of the control system of a field-oriented control algorithm for use in a power tool according to some embodiments. Fig. 5 is a graph illustrating the relationship between stator flux current and stator torque current according to some embodiments. Fig. 6 is a diagram illustrating a negative stator flux current for use in field-oriented control determined by a maximum torque per ampere (MTPA) algorithm according to some embodiments. Fig. 7 is a graph illustrating the relationship between stator flux current and stator torque current according to some embodiments. Fig. 8 is a diagram illustrating the results of field-oriented control operation according to some embodiments. Fig. 9 is a graph illustrating the relationship between stator flux current and stator torque current when driving a motor according to some embodiments. Fig. 10 is a graph illustrating the relationship between stator flux current and stator torque current during flux braking of a motor according to some embodiments. Fig. 11A-11B are a flowchart of a method for implementing field-oriented control of a motor according to some embodiments. Fig. 12 is a flowchart of a method for implementing flux braking according to some embodiments. Detailed description

[0034] The embodiments described herein relate to power tools, such as handheld power tools, that employ a brushless DC motor ("brushless motor"), a field-oriented controller ("FOC"), and flux braking.

[0035] Fig. 1 shows a power tool 100 with flux braking. In the Fig. In the embodiment illustrated in Figure 1, the power tool 100 is a drill / driver. In other embodiments, the power tool 100 is another type of power tool (e.g., a cordless impact driver, a ratchet, a saw, a hammer drill, an impact driver, a rotary hammer, a sander, a blower, a trimmer, etc.) or another type of device (e.g., a light, etc.). The power tool 100 includes a housing 105 and a battery interface 110 for connecting the power tool 100 to, for example, a battery pack. In some embodiments, the battery interface 110 may be configured to connect the power tool 100 to another device.

[0036] Fig. 2 shows a cross section through the power tool 100 from 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 printed circuit board 205 is a control board. In addition to the control board, or instead of the control board, the power tool 100 may also include a power board, a forward / reverse board, and / or a light-emitting diode (LED) board. The power tool 100 may also include a motor 210. In some embodiments, the motor 210 may be a sensorless motor. In other embodiments, the motor 210 may be a sensor-controlled motor. Fig. 2 also shows a drive mechanism 215 that transmits the rotational output of the motor 210 to an output unit 220, and a cooling fan 225 that is rotated by the motor 210 and directs a flow of cooling air over the components of the power tool 100. The power tool 100 may also include a trigger 230 configured to be pulled by a user. In some embodiments, an amount of pull of the trigger 230 may be used to determine the power supplied to the motor 210. The power tool 100 may also 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 upon pull of the trigger 230.

[0037] Fig. 3 shows a control system 300 for a power tool with flux braking (for example, the power tool 100 of Fig. 1). The control system 300 includes a controller 304. The controller 304 is electrically and / or communicatively connected to a variety of modules or components of the power tool 100. The controller 304 shown is, for example, connected to a motor 308 (e.g., the motor 210 in Fig. 2), a battery interface 312 (for example, the battery interface 110 in Fig. 1), a trigger switch 316 (connected to a trigger 320, for example the trigger 230 in Fig. 2), one or more sensors, including at least one current sensor 324 and one temperature sensor 328, one or more indicators 332, one or more user input modules 336, a power input module 340, and a gate controller 344 (connected to an inverter 348). The motor 308 includes a rotor, a stator, and a shaft that rotates about a longitudinal axis.

[0038] The controller 304 includes combinations of hardware and software that, among other things, control the operation of the power tool 100, monitor the operation of the power tool, activate one or more indicators 332 (e.g., an LED), etc. The controller 344 is configured to control the inverter 348 to convert a DC power supply into a three-phase signal that powers the phases of the motor 308. The current sensor 324 is configured, for example, to measure a current between the inverter 348 and the motor 308. The temperature sensor 328 is configured, for example, to measure the temperature of the inverter 348.

[0039] The control unit 304 includes a plurality of electrical and electronic components that power, control, and protect the components and modules of the control unit 304 and / or the power tool 100. For example, the control unit 304 includes, among other things, a processing unit 352 (e.g., a microprocessor, a microcontroller, or other suitable programmable device), a memory 356, input units 360, and output units 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 Fig. 3 as a register group) and is implemented using a known computer architecture (e.g., a modified Harvard architecture, a von Neumann architecture, etc.). The processing unit 352, the memory 356, the input units 360 and the output units 364, as well as the various modules or circuits connected to the control unit 304, are connected by one or more control and / or data buses (e.g., the common bus 380). The control and / or data buses are essentially shown in Fig. 3. The use of one or more control and / or data buses for the connection and communication between the various modules, circuits, and components is known to those skilled in the art within the scope of the invention described herein.

[0040] The memory 356 is a non-transferable 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 be combinations of various 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 storage devices. The processing unit 352 is connected to the memory 356 and executes software instructions that may be stored in a RAM of the memory 356 (e.g., during execution), a ROM of the memory 356 (e.g., permanently), or in another non-transferable computer-readable medium such as another memory or a floppy disk. The memory 356 of the controller 304 may store software associated with the implementation of the power tool.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 for the control operations and methods described herein from the memory 356, among other things. In other constructions, the controller 304 includes additional, fewer, or different components.

[0041] The battery interface 312 includes a combination of mechanical components (e.g., rails, grooves, detents, etc.) and electrical components (e.g., one or more connectors) configured to connect the power tool 100 to a battery (e.g., mechanically, electrically, and communicatively). For example, the power tool receives power from the battery via the battery interface 312 to the power input module 340. The power input module 340 includes a combination of active and passive components that regulate or control the power received from the battery before it is passed to the controller 304. The battery interface 312 also supplies power to the inverter 348, which is switched by the switching FETs to selectively power the motor 308.The battery interface 312 also includes, for example, a communication line 384 that establishes a connection between the control unit 304 and the battery.

[0042] The indicators 332 include, for example, one or more light-emitting diodes ("LEDs"). The indicators 332 may be configured to indicate the state of the power tool 100 or related information. For example, the indicators 332 are configured to indicate measured electrical characteristics of the power tool, the status of the device, etc. The one or more user input modules 336 may be coupled to the controller 304 to select, for example, forward or reverse operation, a torque and / or speed setting for the power tool (e.g., via torque and / or speed switches), etc.In some embodiments, the one or more user input modules 336 may include a combination of digital and analog input or output devices necessary to achieve the desired mode of operation 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 embodiments, the one or more user input modules 336 may wirelessly receive signals from a device external to the power tool (e.g., the user's mobile phone).

[0043] The controller 304 may be configured to determine whether a fault condition of the power tool exists and generate one or more control signals related to the fault condition. For example, the controller 304 may calculate or store in memory 356 predetermined thresholds and limits for the operation of the power tool. For example, if a potential thermal fault (e.g., in a FET, the motor 308, etc.) is detected or predicted by the controller 304, the power supply to the motor 308 may be limited or interrupted until the risk of a thermal fault is reduced.When the controller 304 detects one or more such power tool fault conditions or determines that a power tool fault condition no longer exists, the controller 304 may be configured to transmit information and / or control signals to another component of the power tool (e.g., the battery interface 312, the indicators 332, etc.). The signals may be configured, for example, to trip or open a power tool fuse, reset a switch, brake the motor 308 (e.g., with a flux brake), and the like.

[0044] Fig. 4 is a block diagram of a control system 400 of a field-oriented control algorithm for use in the power tool 100. The control system 400 may be implemented by the controller 304 and may include one or more additional controllers (e.g., dedicated controllers). For example, as shown in Fig. 4, the control system 400 includes a field weakening controller 405 and a field-oriented control ("FOC") controller 435. The field weakening controller 405 and the FOC controller 435 may include one or more mathematical operator blocks, such as multiplication blocks 425A-C that multiply two or more input values, linear scaling blocks 430A-B that linearly scale an input value based on a scaling factor, square root blocks 445 that determine the square root of an input value, and / or addition / subtraction blocks 455A-D that add or subtract two or more input values. In some embodiments, the mathematical operator blocks may perform various mathematical operations. For example, the linear scaling blocks 430A-B may scale a value up or down based on a non-linear function.The field weakening field weakening controller 405 and the FOC controller 435 may each include one or more components configured to send and receive signals between the field weakening field weakening controller 405 and the FOC controller 435.

[0045] The field weakening controller 405 includes a control block for controlling a maximum torque per ampere ("MTPA") algorithm ("MTPA block 410") and a control block for controlling a maximum torque per volt ("MTPV") algorithm ("MTPV block 415"). The MTPA block 410 receives one or more inputs, such as an input i q * from the FOC controller 435, which relates to a torque current. The MTPA block 410 may perform one or more mathematical operations to generate a signal I dq_MTPA* that relates to a flux current and a torque current. The MTPV block 415 receives one or more signals, for example, an input signal I dq_MTPA * from the MTPA block 410, which relates to a flux current and a torque current, an input signal V abc , which refers to the voltages applied to the phases of the motor 308, and / or an input signal V dc , which relates to the voltage of a battery connected to the power tool 100. The MTPV block 415 may also generate one or more output signals, for example, a signal i d *, which refers to a flow current determined by the MTPV block 415, and / or a signal i s_max *, which refers to a maximum current of the stator of the motor 308 determined by the MTPV block 415.

[0046] The field weakening controller 405 may also include a lookup table ("LUT") 420 that includes one or more output values ​​based on one or more input values. For example, the LUT 420 may receive a signal τ related to a current torque of the motor 308. The LUT 420 may determine and output a signal based on the received torque signal τ. In some embodiments, the LUT 420 is a speed map. The speed map receives an estimated load torque as input and outputs a speed reference value based on the estimated load torque. The speed map may be modified by a user to create tool-specific speed-torque curves.The field weakening controller 405 may further include a first multiplication block 425A that receives a first signal from the LUT 420 and a second signal from the trigger 320 of the power tool 100 and multiplies the first and second signals to generate an output signal. The field weakening controller 405 may further include a first linear scaling block 430A that receives a signal from the first multiplication block 425A and scales the signal using a linear function and outputs a signal corresponding to the result of the scaling. In some embodiments, the function is nonlinear. The signal output by the first linear scaling block 430A may be a target speed for the motor 308.

[0047] The FOC controller 435 includes a first addition / subtraction block 455A configured to add a first signal received from the first linear scaling block 430A, which corresponds to a target speed for the motor 308, and subtract a second signal ω, which corresponds to a current speed of the motor 308. The first addition / subtraction block 455A may also be configured to output a signal corresponding to the result of the first addition / subtraction block 455A. The signal output by the first addition / subtraction block 455A may be a speed error of the motor 308. The FOC controller 435 may also include a speed controller 440 configured to receive a signal from the first addition / subtraction block 455A corresponding to a speed error of the motor 308.The speed controller 440 may provide an output signal i based on the speed error. q * and the output signal i q * output to MTPA block 410.

[0048] The FOC controller 435 may also include a second multiplication block 425B configured to generate two signals i s_max * (ie twice the same signal) from the MTPV block 415 of the field weakening controller 405. The second multiplication block 425B can multiply the two signals i s_max * multiply together to get a squared value of i s_max * and produce an output signal equal to the squared value of i s_max*. The FOC controller 435 may also include a third multiplication block 425C configured to receive two signals i* (ie, twice the same signal) from the MTPV block 415 of the field weakening controller 405. The third multiplication block 425C may multiply the two signals i d * multiply together to get a squared value of i d * and produce an output signal equal to the squared value of i d *. The FOC controller 435 may further include a second addition / subtraction block 455B configured to receive and add a first signal from the second multiplication block 425B corresponding to the squared value of i s_max*. The second addition / subtraction block 455B may also be configured to receive and subtract a second signal from the third multiplication block 425C corresponding to the squared value of id*. The second addition / subtraction block 455B may also be configured to generate an output signal corresponding to the result of the second addition / subtraction block 455B. The FOC controller 435 may also include a square root block 445 configured to receive a signal from the second addition / subtraction block 455B corresponding to the result of the second addition / subtraction block 455B.

[0049] The square root block 445 may also be configured to generate a signal i q,maxto generate and output a current I corresponding to the square root value of the signal received from the second addition / subtraction block 455B. That is, the combination of the second multiplication block 425B, the third multiplication block 425C, the second addition / subtraction block 455B, and the square root block 445 may be configured to perform a Pythagorean operation on the outputs of the MTPV block 415 to determine the current I s of the stator of the motor 308 into its component vectors, the flux current i d and the torque current i q , to disassemble.

[0050] The FOC controller 435 may also include a third addition / subtraction block 455C configured to generate a first signal i d* from the MTPV block 415 and add it, which corresponds to the flux current determined by the MTPV block 415. The third addition / subtraction block 455C may also be configured to receive a second signal I d corresponding to the total flux current of the motor 308. The third addition / subtraction block 455C may be configured to receive and subtract a signal I d corresponding to the result of the third addition / subtraction block 455C. The FOC controller 435 may also include a flow controller 460 configured to receive an input signal I d from the third addition / subtraction block 455C and based on the input signal I d a forward voltage signal V d generates and outputs.

[0051] The FOC controller 435 also includes a second linear scaling block 430B configured to generate a first signal i q* from the speed control unit 440 and a second signal i q,max from the square root block 445. The second linear scaling block 430B may be configured to receive the first signal i q * based on the second signal i q,max linearly scaled and outputs a signal corresponding to the result of the second linear scaling block 430B. The FOC controller 435 further includes a fourth addition / subtraction block 455D configured to receive and add a first signal corresponding to the result of the second linear scaling block 430B. The fourth addition / subtraction block 455D may also be configured to output a second signal I q corresponding to the total torque current of the motor 308. The fourth addition / subtraction block 455D may be configured to receive and subtract a signal I qcorresponding to the result of the fourth addition / subtraction block 455D. The FOC controller 435 may also include a torque controller 465 configured to receive an input signal I q from the fourth addition / subtraction block 455D and a torque voltage signal V q based on the input signal I q generates and outputs.

[0052] The FOC controller 435 may also include an inverse parking transformation block 475 configured to provide a first signal V d from the flow control device, which corresponds to a flow voltage, a second signal V q from the torque control unit corresponding to a torque voltage, and a third signal θ corresponding to a current angular position of a rotor of the motor 308. The inverse Park transformation block 475 may be configured to receive the first signal V dand the second signal V q based on the third signal θ into orthogonal stationary reference frame quantities V α and V β The inverse parking transform block 475 may also be configured to output a signal corresponding to the orthogonal stationary reference frame quantities V α and V β The FOC controller 435 may also include a PWM generator 480 with an inverse Clarke transform block, a PWM modulator, or both. The PWM generator 480 may be configured to generate the signal corresponding to the orthogonal stationary reference frame quantities V α and V β from the inverse parking transform block 475 and a plurality of pulse width modulated (“PWM”) control signals V PWMX 3, which are configured to control the inverter 348. The inverter 348 may be configured to generate the plurality of PWM control signals V PWMX3 and converts a DC power supply into a three-phase signal V abc to control the motor 308. The three-phase signal V abc can also be received by the MTPV block 415.

[0053] The FOC controller 435 also includes a three-phase to two-phase reference frame converter 485 configured to convert the three-phase signal V abc from the inverter and receives a two-phase current signal I α , I β based on the three-phase signal V abc The FOC controller 435 also includes a position and speed estimator 470 configured to generate and output the two-phase current signal I α , I β from the three-phase to two-phase reference frame converter 485 and determines a position and speed of the motor 308 based on the two-phase current signal I α , I βThe position and speed estimator 470 may also be configured to output a first signal θ relating to the current angular position of the rotor of the motor 308 and a second signal ω relating to the current rotational speed of the rotor of the motor 308. The first signal θ is received by the inverse Park transformation block 475. The second signal ω is also received by the first addition / subtraction block 455A. The FOC controller 435 further includes a Park transformation block 490 configured to output the two-phase current signal I α I β from the three-phase to two-phase reference frame converter 485 and the first signal θ, which relates to the current angular position of the rotor of the motor 308, from the position and speed estimator 470. The Park transformation block 490 is also configured to receive a first signal I q, which corresponds to a total torque current of the motor 308, and a second signal I d , which corresponds to a total flux current of the motor 308, based on the two-phase current signal I α I β and the first signal θ. The first signal I q can be received by the torque observer 450 and the fourth addition / subtraction block 455D. The second signal I d can be received by the third addition / subtraction block 455C.

[0054] Fig. Figure 5 is a diagram 500 illustrating a relationship between the stator flux current and the stator torque current in a qd coordinate plane. The diagram 500 shows that the stator flux current i d 510 and the stator torque current i q 515 both partial vectors of the stator current I s 505. As can be seen from diagram 500, i d 510 especially as a function of I s505 and the angle between I s 505 and the d-axis, θ 520, can be calculated according to equation (1). id=Is cosθ

[0055] In a similar way, i q 515 as a function of I s 505 and θ 520 according to equation (2), as shown in diagram 500. iq=Is sinθ

[0056] A brushless motor (for example the 308 motor in Fig. 3) has a rotor with a permanent magnet. This permanent magnet generates a magnetic field, which in turn generates a reluctance torque from the difference between an inductance on the d-axis and an inductance on the q-axis. The reluctance torque, T e , can be determined by equation (3), where P is the number of pole pairs of the motor, φ f the stator flux, L d a direct inductance on the d-axis and L q is a quadrature inductance on the q-axis. Te=1.5P(φfiq+(Ld−Lq)idiq)

[0057] From equation (3) it can be seen that a negative value of i d 510 ensures that T e remains positive, which is advantageous. Furthermore, the above equations (1), (2), and (3) can be combined to form equation (4). Te=1.5P(ΦfIs sinθ+0.5(Ld−Lq)Is2sin 2θ)

[0058] Fig. 6 is a diagram 600 illustrating a negative stator flux current for use in field weakening determined by a maximum torque per ampere ("MTPA") algorithm. Specifically, the diagram 600 illustrates an MTPA vector 625 generated by an MTPA block (e.g., MTPA block 410) based on a crossover between a constant current 605 and a constant torque 610 of the motor 308. In some embodiments, the MTPA vector 625 is a minimum current space vector that satisfies at least one constraint of the MTPA algorithm. The MTPA vector 625 also includes a beta angle 630. In some embodiments, the beta angle 630 is optimized between 0° and 45° to the q-axis. In some embodiments, the beta angle 630 being between 0° and 45° is a constraint of the MTPA algorithm. The point at which the MTPA vector 625 crosses the constant current 605 and the constant torque 610 can be determined by a flux current id 615 and a torque current i q 620. As defined in Fig. 6, the river current i d 615 at the point where the MTPA vector 625 is optimized, negative with respect to the d-axis. In some embodiments, the MTPA vector 625 may have a different beta angle 630 that is still between 0° and 45° to the q-axis. However, in these embodiments, the MTPA vector 625 may not be a minimum current space vector and therefore not optimized.

[0059] Fig. Figure 7 is a diagram 700 illustrating a relationship between the stator flux current and the stator torque current. The diagram 700 includes a current limit 705 as a circle with an amplitude centered at the origin and a voltage limit 710 as a family of nested ellipses centered at the point where the MTPA vector is optimized (i.e., the value of i d acts on the reluctance torque Te according to equation [3]). The radii of the ellipses of the voltage limit 710 may vary inversely with the speed of the rotor of the motor 308. In some embodiments, the ellipses of the voltage limit 710 are distorted along the vertical q-axis due to a saturation effect, and the diameters of the ellipses of the voltage limit 710 have a counterclockwise tilt along the horizontal d-axis due to stator resistance effects. At a given speed, the motor 308 may operate with any combination of i q - and i d -values ​​that fall within the overlap range of the current limit 705 and the voltage limit 710 associated with this speed. The value of negative I d , at which it completely opposes and cancels out the permanent magnet flux of the motor 308, is indicated at 715.

[0060] The diagram 700 also includes a first MTPA vector 720 without the effects of magnetic saturation and a second MTPA vector 725 with the effects of magnetic saturation. The first MTPA vector 720 forms an angle with the negative d-axis that exceeds 45°, while the second MTPA vector 725 forms an angle with the negative q-axis that does not exceed 45°. The diagram 700 also includes a point of maximum output power 730 that follows the edge of the current limit 705 toward the negative d-axis. This movement may be forced by the increasing speed, which progressively shrinks the voltage limit 710 and prevents the machine from operating according to the MTPA algorithm (dashed line 735).

[0061] The maximum output point 730 for speeds above the corner point may be an optimistic outer limit for the current vector location, which can only be approximated but never quite reached for a truly current-controlled drive. This is because the outer limit of the voltage limit 710 at any speed corresponds to six-step voltage operation, which represents a condition where the current controller loops are fully saturated. Since a current controller loses control of the phase currents under such conditions, the current vector command can be continuously adjusted so that it is always safely within the voltage limit 710. However, it is desirable to approach the voltage limit 710 as closely as possible under heavy load conditions to achieve the maximum performance of the motor 308 and to fully utilize the power delivered by the inverter 348.Therefore, the angle between the commanded current vector and the negative d-axis is decreased as the shrinking voltage boundary 710 gradually penetrates the current boundary 705 at speeds above the corner point.

[0062] Fig. 8 is a diagram 800 showing the results of a field weakening process. Fig. 8 shows in particular how the angle θ S between the commanded current vector I S reduced when the shrinking voltage limit 710 (see Fig. 7) gradually penetrates the current limit 705 at speeds above the corner point.

[0063] Fig. 9 is a diagram 900 showing a relationship between the stator flux current, id, 905 (i.e., a flux-generating current) and the stator torque current, i q , 910 (ie, a torque-generating current) when driving a motor (for example, motor 308). Fig. 9 shows in particular that the stator torque current i q 910 is controlled by the FOC control unit 435 so that it is greater than the stator flux current i during the drive of the motor 308 d 905. Because the stator torque current, i q , 910 is greater than the stator flux current i d 905, the motor 308 generates greater torque during drive operation.

[0064] Fig. 10 is a diagram 1000 showing a relationship between the stator flux current i d 1005 and the stator torque current i q 1010 during braking (ie, flux braking) of a motor (e.g., motor 308). In some embodiments, the stator flux current i d 1005 and the stator torque current i q 1010 the same current vectors as the stator flux current, i d , 905 and the stator flux current i q 910 in Fig. 9, but are shown with different amounts. Fig. Figure 10 shows in particular that the stator flux current i d 1005 is controlled by the FOC control unit 435 so that it has a greater value than the stator torque current i when braking the motor 308 q 1010. By maintaining a larger stator torque current i d 1005, the magnetic flux of motor 308 is increased so that motor 308 can brake (i.e., flux braking) without flowing regenerative current or requiring separate energy-absorbing components. In some embodiments, position sensing is maintained during flux braking.

[0065] Fig. 11A-11B depict a flowchart of a method 1100 for implementing the FOC control of motor 308 described above. Method 1100 begins with controller 304 (e.g., including FOC controller 435) controlling motor 308 based on the FOC control algorithm (block 1105). Method 1100 includes controller 304 receiving a first signal from a sensor (e.g., current sensor 324, temperature sensor 328, trigger switch 316, a sensor connected to user inputs 336, etc.) indicative of a braking event of motor 308 (block 1110). For example, the first signal is generated based on a detected fault condition of the motor 308, a detected fault condition of a FET, the triggering of the trigger 230, an overtemperature measurement by the temperature sensor 328, or another indication that a braking operation should be initiated.Method 1100 also includes controller 304 generating or providing a command to decelerate motor 308 using the FOC (i.e., flux braking) control algorithm (block 1115). Method 1100 further includes controller 304 determining whether the braking command provided to control motor 308 during the braking event is sufficient to decelerate motor 308 (e.g., decelerate the motor to a stop, decelerate to a stop in a specified amount of time, etc.) (block 1120). If the brake command is not sufficient to complete the desired braking event, method 1100 returns to block 1115, and controller 304 may modify the brake control to ensure that the brake command is sufficient to complete the desired braking event (e.g., brake the motor to a stop, brake to a stop in a certain time, etc.). For example, the flux current i. dto a larger positive value. Method 1100 may perform blocks 1115 and 1120 as many times as necessary to adjust the brake command signal so that the braking action is sufficient to brake motor 308 according to the desired braking parameters (e.g., brake the motor to a stop, brake within a certain time period, etc.).

[0066] If, with reference to Fig. 11 the braking command is sufficient to complete the desired braking action (e.g., to brake the motor to a stop, to brake within a certain period of time, etc.), the controller 304 continues to control the motor 308 using flux braking until the desired braking action is completed (block 1125). The method 1100 also includes the controller 304 receiving a second signal indicative of a subsequent drive action of the motor 308 (block 1130). For example, the second signal is generated based on a further pull or cycle of the trigger 230 indicating that the user is requesting the motor 308 to perform another drive action. The method 1100 also includes the controller 304 issuing a drive command to drive the motor 308 using the FOC control algorithm (block 1135).In some embodiments, controller 304 drives motor 308 using the FOC control algorithm until the drive operation is completed. In other embodiments, controller 304 receives a third signal indicating a subsequent braking operation of motor 308. If controller 304 receives the third signal, method 1100 returns to block 1105 to repeat method 1100.

[0067] Fig.12 shows a flowchart of a method 1200 for performing flux braking of motor 308 based on the FOC control algorithm described above. Method 1200 begins with controller 304 (e.g., including FOC controller 435) controlling motor 308 based on the FOC control algorithm (block 1205). Method 1200 includes controller 304 receiving a first signal indicative of a flux braking operation of motor 308 (block 1210). The first signal is generated, for example, due to a detected fault condition of motor 308, a detected fault condition of a FET, the trigger 230 being triggered, an overtemperature measurement by temperature sensor 328, or another indication that braking should be initiated.To brake the motor 308, the method 1200 also includes generating or providing a second signal to control the motor 308 to decrease or decrease a first component of the current (e.g., the stator torque current i. q 1010) of the motor 308 (block 1215). In some embodiments, the controller 304 generates or provides the second signal to reduce the first component of the current to zero. The method 1200 also includes generating or providing a third signal to control the motor 308 to reduce the second component of the current (e.g., the stator flux current, i d , 1005) of the motor 308 (block 1220). In some embodiments, the controller 304 generates or provides the third signal to control the second component of the current to have a zero or positive value.

[0068] Method 1200 also includes controller 304 determining whether the third signal provided to control motor 308 during the braking event is sufficient to brake motor 308 (e.g., brake the motor to a stop, brake to a stop in a certain amount of time, etc.) (block 1225). If the third signal is not sufficient to complete the desired braking event (e.g., brake the motor to a stop, brake to a stop in a certain amount of time, etc.), method 1200 returns to block 1220, and controller 304 may modify the braking control such that the braking command is sufficient to complete the desired braking event (e.g., brake the motor to a stop, brake to a stop in a certain amount of time, etc.). For example, the flux current i dincreased to a larger positive value. Controller 304 provides a fourth signal to control motor 308 to control the second component and ensure that the braking action is sufficient to complete the braking action (e.g., brake the motor to a stop, brake to a stop in a certain amount of time, etc.). In some embodiments, controller 304 determines that the third signal is insufficient by determining the battery voltage via communication line 384, determining the battery current via communication line 384, or determining the speed of motor 308. Controller 304 provides the fourth signal based on the determined battery voltage and / or current and / or rotational speed, etc. In some embodiments, the fourth signal differs (e.g., in magnitude) from the third signal.Method 1200 performs BLOCK 1225 as many times as necessary to ensure that the braking action is sufficient to brake the motor 308 (e.g., brake the motor 308 to a stop, brake to a stop within a specified time period, etc.). If the braking command is sufficient to complete the desired braking action, the controller 304 continues to brake the motor 308 via the FOC control algorithm, including the third signal or the fourth signal, until the braking action is complete (BLOCK 1230).

[0069] In some embodiments, method 1200 includes controller 304 receiving a fifth signal indicative of subsequent drive action of motor 308. For example, the fifth signal is generated based on a cycling or renewed actuation of trigger 230, indicating that the user is requesting further drive action of motor 308. In some embodiments, method 1200 also includes controller 304 generating or providing a sixth signal to control motor 308 to drive the first component (e.g., stator torque current, i q, 1010) of the current of the motor 308 for the drive operation. In some embodiments, the sixth signal corresponds to the second signal that the controller 304 provides for the braking operation. In some embodiments, the method 1200 further includes generating or providing a seventh signal for controlling the motor 308 to control the second component (e.g., the stator flux current, i d, 1005) of the current of the motor 308 for the drive operation. In some embodiments, the seventh signal is similar to the third signal provided by the controller 304 for the braking operation. In some embodiments, the controller 304 provides the seventh signal to reduce the second component of the current, for example, to zero. When the controller 304 reduces the second component of the current to zero, it can maximize the torque provided by the motor 308. In some embodiments, the method 1200 returns to BLOCK 1205 after a drive operation if the controller 304 receives a user input. The user input could be, for example, releasing the trigger 230 during the drive operation. Representative characteristics

[0070] Representative features are described in the following sections, which may stand alone or be combined in any combination with one or more features disclosed in the text and / or drawings of the specification. 1. Power tool comprising: a housing; a handle; a brushless motor within 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, the longitudinal axis passing through the motor shaft, and the motor shaft arranged to produce a rotary output for a drive mechanism; a sensor configured to detect a parameter of the brushless motor; a power circuit configured to supply the brushless motor with power from a power source; and an electronic control unit configured to control the brushless motor using a field-oriented control (“FOC”) technique, the electronic control unit being configured to: to receive a first signal via the sensor indicating a braking process of the brushless motor, generate a second signal to control a first component of a current of the brushless motor to brake the brushless motor, and generate a third signal to control a second component of the brushless motor current to brake the brushless motor. 2. Power tools as defined in Section 1, in which the electronic control unit is furthermore designed to: in response to the third signal, determine whether the third signal is sufficient to brake the brushless motor; and in response to determining that the third signal is insufficient, generating a fourth signal to control the second component of the current, the fourth signal being different from the third signal. 3. Power tool according to one of the sections 1-2, in which the first component of the current is a torque-generating current (i q ) displays. 4. Power tool according to one of the sections 1-3, in which the second component of the current is a flux-generating current (i d ) displays. 5. Power tool according to one of clauses 1-2, wherein the generation of the third signal for controlling the second component of the current includes the electronic control device being arranged to control the second component of the current to have a positive magnitude. 6. A power tool according to clause 1, wherein generating the second signal for controlling the first component of the current includes the electronic control device being arranged to control the first component of the current to zero. 7. Power tool according to any of sections 1-6, in which the electronic control unit is furthermore designed to: to determine a battery voltage while braking the brushless motor; to determine a battery current while braking the brushless motor; to determine a speed of the brushless motor while braking the brushless motor; and provide a fourth signal to the brushless motor based on at least one of the quantities selected from a group comprising battery voltage, battery current, and speed. 8. A method for controlling a power tool with an electronic control unit, the method comprising: Receiving a first signal indicating a braking operation of a brushless motor via a sensor; Generating a second signal for controlling a first component of a current of the brushless motor to brake the brushless motor; and Generating a third signal to control a second component of the brushless motor current to brake the brushless motor. 9. Procedures under Section 8, further comprising: in response to the third signal, determining whether the third signal is sufficient to brake the brushless motor; and in response to determining that the third signal is insufficient, supplying a fourth signal to the brushless motor to control the second component of the current, the fourth signal being different from the third signal. 10. A method according to any one of clauses 8-9, wherein the first component of the current is a torque-generating current (i q ) displays. 11. A method according to any one of paragraphs 8-10, wherein the second component of the current is a flux-generating current (i d ) displays. 12. The method of any one of clauses 8-11, wherein applying the third signal controls the second component of the current to have a positive magnitude. 13. The method of any one of clauses 8-11, wherein supplying the second signal to the brushless motor to control the first component of the current comprises: Controlling the first component of the current to zero. 14. Procedures under any of Sections 8-13, further comprising: Determining a battery voltage during braking of the brushless motor; Determining a battery current during braking of the brushless motor; Determining a speed of the brushless motor during braking of the brushless motor; and Supplying the fourth signal to the brushless motor based on at least one of the quantities selected from the group consisting of battery voltage, battery current, and speed. 15. Power tool comprising: a housing; a handle; a brushless motor within 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, the longitudinal axis passing through the motor shaft, and the motor shaft arranged to produce a rotary output for a drive mechanism; a sensor configured to detect a parameter of the brushless motor; a power circuit configured to supply the brushless motor with power from a power source; and an electronic control unit configured to control the brushless motor using a field-oriented control (“FOC”) technique, the electronic control unit being configured to: after a flux braking process of the brushless motor, to receive a first signal via the sensor indicating a drive process of the brushless motor, generate a second signal to control a first component of a current of the brushless motor to drive the brushless motor, and generate a third signal to control a second component of the brushless motor current to drive the brushless motor. 16. Power tool according to section 15, in which the first component of the current is a torque-generating current (i q ) displays. 17. Power tool according to any one of clauses 15-16, wherein the second component of the current is a flux-generating current (i d ) displays. 18. The power tool according to clause 15, wherein generating the third signal includes the electronic control device being configured to reduce the second component of the current to zero. 19. A power tool according to any one of clauses 15 and 18, wherein reducing the second component to zero maximizes the torque delivered by the brushless motor. 20. Power tool according to any of the sections 15-19, in which the electronic control unit is furthermore designed to to receive user input; and to brake the brushless motor in response to user input.

[0071] The embodiments described herein thus provide systems and methods for implementing flux braking of a power tool with a brushless DC motor controlled by a field-oriented controller. Various features and advantages are set forth in the following claims. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 480,121

[0001] US 63 / 381,858

[0001]

Claims

[1] Power tool comprising: a housing; a handle; a brushless motor within 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, the longitudinal axis passing through the motor shaft, and the motor shaft arranged to produce a rotary output for a drive mechanism; a sensor configured to detect a parameter of the brushless motor; a power circuit configured to supply the brushless motor with power from a power source; and an electronic control unit configured to control the brushless motor using a field-oriented control (“FOC”) technique, the electronic control unit being configured to: to receive a first signal via the sensor indicating a braking process of the brushless motor, generate a second signal to control a first component of a current of the brushless motor to brake the brushless motor, and generate a third signal to control a second component of the brushless motor current to brake the brushless motor. [2] Power tool according to claim 1, wherein the electronic control unit is further configured to: in response to the third signal, determine whether the third signal is sufficient to brake the brushless motor; and in response to determining that the third signal is insufficient, generating a fourth signal to control the second component of the current, the fourth signal being different from the third signal. [3] Power tool according to claim 2, wherein the first component of the current is a torque-generating current (i q ) displays. [4] Power tool according to claim 2, wherein the second component of the current is a flux-generating current (i d ) displays. [5] A power tool according to claim 1, wherein generating the third signal for controlling the second component of the current includes the electronic control unit being arranged to control the second component of the current to have a positive magnitude. [6] A power tool according to claim 1, wherein generating the second signal for controlling the first component of the current includes the electronic control device being arranged to control the first component of the current to zero. [7] Power tool according to claim 1, wherein the electronic control unit is further arranged to: to determine a battery voltage while braking the brushless motor; to determine a battery current while braking the brushless motor; to determine a speed of the brushless motor while braking the brushless motor; and provide a fourth signal to the brushless motor based on at least one of the quantities selected from a group comprising battery voltage, battery current, and speed. [8] A method for controlling a power tool with an electronic control device, the method comprising: Receiving a first signal indicating a braking operation of a brushless motor via a sensor; Generating a second signal for controlling a first component of a current of the brushless motor to brake the brushless motor; and Generating a third signal to control a second component of the brushless motor current to brake the brushless motor. [9] The method of claim 8, further comprising: in response to the third signal, determining whether the third signal is sufficient to brake the brushless motor; and in response to determining that the third signal is insufficient, supplying a fourth signal to the brushless motor to control the second component of the current, the fourth signal being different from the third signal. [10] A method according to claim 9, wherein the first component of the current is a torque-generating current (i q ) displays. [11] A method according to claim 9, wherein the second component of the current is a flux-generating current (i d ) displays. [12] A method according to claim 11, wherein applying the third signal controls the second component of the current to have a positive magnitude. [13] The method of claim 11, wherein supplying the second signal to the brushless motor to control the first component of the current comprises: Controlling the first component of the current to zero. [14] The method of claim 11, further comprising: Determining a battery voltage during braking of the brushless motor; Determining a battery current during braking of the brushless motor; Determining a speed of the brushless motor during braking of the brushless motor; and Supplying the fourth signal to the brushless motor based on at least one of the quantities selected from the group consisting of battery voltage, battery current, and speed. [15] Power tool comprising: a housing; a handle; a brushless motor within 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, the longitudinal axis passing through the motor shaft, and the motor shaft arranged to produce a rotary output for a drive mechanism; a sensor configured to detect a parameter of the brushless motor; a power circuit configured to supply the brushless motor with power from a power source; and an electronic control unit configured to control the brushless motor using a field-oriented control (“FOC”) technique, the electronic control unit being configured to: after a flux braking process of the brushless motor, to receive a first signal via the sensor indicating a drive process of the brushless motor, generate a second signal to control a first component of a current of the brushless motor to drive the brushless motor, and generate a third signal to control a second component of the brushless motor current to drive the brushless motor. [16] Power tool according to claim 15, wherein the first component of the current is a torque-generating current (i q ) displays. [17] Power tool according to claim 15, wherein the second component of the current is a flux-generating current (i d ) displays. [18] The power tool of claim 15, wherein generating the third signal includes the electronic control unit being configured to reduce the second component of the current to zero. [19] A power tool according to claim 18, wherein reducing the second component to zero maximizes the torque delivered by the brushless motor. [20] Power tool according to claim 15, wherein the electronic control unit is further configured to to receive user input; and to brake the brushless motor in response to user input.

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