Power tool with soft to hard brake control

Abstract

A power tool includes a housing, a motor disposed within the housing, a power switch circuit configured to control power provided to the motor from a power source, and an electronic controller. The electronic controller is connected to a sensor and the power switch circuit. The electronic controller is configured to control the power switch circuit to apply a soft braking force, to enhance the soft braking force by controlling a conduction angle and a phase lead angle, and to control the power switch circuit to apply a hard braking force when the conduction angle reaches a maximum conduction angle and the phase lead angle reaches a maximum phase lead angle.

Description

[0001] Related applications This application claims priority to U.S. Provisional Patent Application No. 63 / 762,336, filed February 24, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The embodiments described in this invention relate to power tools including brushless DC motors. Summary of the Invention

[0003] During operation, power tools generate energy in the form of angular momentum due to the rotation of the tool or its attachments. Even after operation has stopped, this energy may continue to drive the tool. Therefore, the tool may attempt to brake the motor by switching on the drive motor. However, braking requires large or reinforced electrical components to withstand the stress during braking. Therefore, some power tools are equipped with braking systems that enable rapid braking without damaging electrical components.

[0004] The power tool of the present invention includes a housing, a motor disposed within the housing, a power switching circuit configured to control the power supplied from a power source to the motor, and an electronic controller. The electronic controller is connected to a sensor and the power switching circuit. The electronic controller is configured to: control the power switching circuit to apply soft braking force; control the conduction angle and phase lead angle to enhance the soft braking force; and control the power switching circuit to apply hard braking force when the conduction angle reaches its maximum and the phase lead angle reaches its maximum.

[0005] In some aspects, the power switch circuit includes: a first high-side switch, a second high-side switch, a third high-side switch, a first low-side switch, a second low-side switch, and a third low-side switch.

[0006] In some respects, to apply soft braking force, the electronic controller is configured to control two of the first low-side switch, the second low-side switch, and the third low-side switch to be in an active state.

[0007] In some respects, to apply soft braking force, the electronic controller is configured to control one of the first low-side switch, the second low-side switch, and the third low-side switch to be in an active state.

[0008] In some respects, the maximum conduction angle is 180 degrees.

[0009] In some respects, the maximum conduction angle is 180 to 240 degrees.

[0010] In some respects, the maximum phase lead angle is 60 degrees.

[0011] The power tool of this invention includes a housing, a motor disposed within the housing, a power switching circuit configured to control the power supplied from a power source to the motor, and an electronic controller. The electronic controller is connected to a sensor and the power switching circuit. The electronic controller is configured to control the power switching circuit to apply soft braking force, monitor the motor speed, enhance the soft braking force by controlling the conduction angle and phase lead angle, and control the power switching circuit to apply hard braking force when the motor speed drops to a speed threshold.

[0012] In some respects, the power switch circuit includes: a first high-side switch, a second high-side switch, a third high-side switch, a first low-side switch, a second low-side switch, and a third low-side switch.

[0013] In some respects, to apply soft braking force, the electronic controller is configured to control two of the first low-side switch, the second low-side switch, and the third low-side switch to be in an active state.

[0014] In some respects, to apply soft braking force, the electronic controller is configured to control one of the first low-side switch, the second low-side switch, and the third low-side switch to be in an active state.

[0015] In some respects, the speed threshold is 3,000 rpm to 5,000 rpm.

[0016] In some respects, to apply hard braking force, the electronic controller is configured to keep the first low-side switch, the second low-side switch, and the third low-side switch active.

[0017] In some respects, the power switching circuit applies hard braking force before the conduction angle reaches its maximum conduction angle and before the phase lead angle reaches its maximum phase lead angle.

[0018] The power tool of the present invention includes: a housing, a motor disposed within the housing, a power switch circuit configured to control the power supplied from a power source to the motor, a sensor for measuring the operating parameters of the power tool, and an electronic controller. The electronic controller is connected to the sensor and the power switch circuit. The electronic controller is configured to receive signals related to the operating parameters of the power tool transmitted by the sensor; determine the operating parameters of the power tool based on the sensor signals during the startup phase; calculate a braking adjustment value based on the operating parameters; and control the braking of the motor based on the calculated braking adjustment value during the braking phase.

[0019] In some respects, the electronic controller is also configured to: when it is determined that the operating parameters are below a predetermined threshold, control the power switch circuit to brake the motor according to a first braking configuration; and when it is determined that the operating parameters are greater than or equal to the predetermined threshold, control the power switch circuit to brake the motor according to a second braking configuration.

[0020] In some respects, the operating parameters include temperature, motor energy, or motor speed.

[0021] In some respects, the first braking configuration is a torque reduction mode, while the second braking configuration is a rapid braking mode.

[0022] In some respects, the operating parameters are the starting energy of the motor during the startup phase.

[0023] In some respects, the braking force applied during the braking phase is set according to the operating parameters.

[0024] Before detailing any specific embodiments, it should be noted that the application scope of these embodiments is not limited to the component configuration and arrangement details described below or shown in the accompanying drawings. Embodiments of the present invention can be implemented or carried out in various ways. It should also be understood that the wording and terminology used in this invention are for descriptive purposes only and should not be considered as limiting the invention. The use of "comprising," "including," or "having," and variations thereof, is intended to cover the items listed thereafter and their equivalents, as well as additional items. Unless otherwise stated or limited, the terms "installation," "connection," "support," and "linkage," and variations thereof, are widely used and cover direct and indirect installation, connection, support, and linking.

[0025] Unless the context of their use explicitly indicates otherwise, the articles “a” and “the” should not be interpreted as meaning “one” or “only one.” Rather, these articles should be interpreted as meaning “at least one” or “one or more.” Similarly, when the terms “the” or “the” are used to refer to a noun previously introduced by the indefinite articles “a” or “one,” “the” and “the” mean “at least one” or “one or more” unless the usage explicitly indicates otherwise.

[0026] Furthermore, it should be understood that embodiments of the present invention may include hardware, software, and electronic components or modules. For ease of discussion, most components may be considered to be implemented solely in hardware in the illustrations and description. However, those skilled in the art will recognize upon reading this detailed specification that, in at least one embodiment, the electronic components may be implemented in software (e.g., stored on a non-transitory computer-readable medium), which may be executed by one or more processing units (such as microprocessors and / or application-specific integrated circuits (ASICs)). Therefore, it should be noted that the examples may be implemented using multiple hardware- and software-based devices and multiple different structural components. For example, "server," "computing device," "controller," "processor," etc., described in the specification may include one or more processing units, one or more computer-readable medium modules, one or more input / output interfaces, and various connections of connecting components (e.g., system buses).

[0027] Relative terms used in conjunction with quantities or conditions, such as “about,” “approximately,” “substantially,” etc., will be understood by one of ordinary skill in the art to include the value and have a meaning defined by the context (e.g., the term includes at least the degree of error associated with measurement accuracy, the tolerance associated with a particular value [e.g., manufacturing, assembly, use, etc.]). Such terms should also be considered to disclose a range defined by the absolute values ​​of the two endpoints. For example, the expression “about 2 to about 4” also discloses a range of “2 to 4.” Relative terms may refer to a percentage of the indicated value added to or subtracted (e.g., 1%, 5%, 10% or more).

[0028] It should be understood that although some figures illustrate hardware and software residing within a particular device, these descriptions are for illustrative purposes only. Functions described herein as being performed by a single component can be performed by multiple components in a distributed manner. Similarly, functions performed by multiple components can be combined and performed by a single component. In some examples, the illustrated components can be combined or divided into separate software, firmware, and / or hardware. For example, logic and processing can be distributed among multiple electronic processors, rather than residing within and being performed by a single electronic processor. Regardless of how the hardware and software components are combined or divided, they can reside on the same computing device or be distributed among different computing devices connected via one or more networks or other suitable communication links. Similarly, components described as performing specific functions can also perform additional functions not described herein. For example, a device or structure "configured" in a certain way is at least configured in that manner, but may also be configured in a manner not explicitly listed.

[0029] Therefore, in the claims, if the 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 certain way to perform, for example, multiple functions, then the claim or claim element should be interpreted as referring to one or more such elements, any one of which is configured, for example, to cause any one or more of the multiple functions, such that the one or more elements together perform multiple functions.

[0030] Other aspects of the embodiments will become apparent from the following detailed description and accompanying drawings. Attached Figure Description

[0031] Figure 1 is a perspective view of a power tool according to some embodiments.

[0032] Figure 2 is a perspective view of a power tool according to some embodiments.

[0033] Figure 3 is a control system for the power tool shown in Figure 1 and / or Figure 2 according to certain embodiments.

[0034] Figure 4 is a control system for the power tool shown in Figure 1 and / or Figure 2 according to certain embodiments, wherein a switching network is further shown.

[0035] Figures 5 and 6 illustrate various exemplary switch configurations for controlling power tool motors according to certain embodiments.

[0036] Figure 7 is a graph drawn according to certain embodiments, showing the relationship between braking command effect, conduction angle, phase lead angle and motor speed.

[0037] Figure 8 illustrates the process of switching between hard braking and soft braking according to certain embodiments.

[0038] Figure 9 is a graph drawn according to certain embodiments, showing the relationship between braking command effect, conduction angle, phase lead and motor speed.

[0039] Figure 10 is a block diagram of a power tool control system according to some embodiments, which can switch between different braking modes.

[0040] Figure 11A is a graph drawn according to certain embodiments, showing the relationship between tool speed, motor current and tool energy calculated when using lighting accessories.

[0041] Figure 11B is a graph drawn according to certain embodiments, showing the relationship between tool speed, motor current and tool energy calculated when using heavy attachments.

[0042] Figures 12 and 13 illustrate the energy and braking operation of the tool during startup according to certain embodiments.

[0043] Figure 14 illustrates the process of controlling a power tool at different operational stages according to certain embodiments.

[0044] Figure 15 illustrates the relationship between motor output and tool speed during start-up and braking operations, according to certain embodiments.

[0045] Figure 16 is a flowchart of controlling a power tool during different operating and braking phases according to certain embodiments.

[0046] Figure 17 illustrates the energy of the tool during start-up and braking operations according to certain embodiments.

[0047] Figure 18 illustrates the process of controlling a power tool during start-up and braking operations according to certain embodiments.

[0048] Figure 19 illustrates the energy changes of the tool during start-up and braking operations according to certain embodiments. Detailed Implementation

[0049] Figures 1 and 2 illustrate exemplary power tools 100A and 100B, respectively. In the embodiment shown in Figure 1, power tool 100A is a drill / screwdriver. In the embodiment shown in Figure 2, power tool 100B is a grinder. In some embodiments, power tool 100 may be other types (e.g., impact wrench, ratchet wrench, saw, hammer drill, impact screwdriver, rotary hammer, circular saw, etc.). In other embodiments, power tool may be an outdoor tool (e.g., trimmer, peg saw, blower, chainsaw, etc.), a drum machine, etc. Each power tool 100A, 100B includes a housing 105 and a battery interface 110 for connecting power tool 100A, 100B to a battery pack or other device. In some embodiments, the battery interface 110 may be configured to connect power tool 100A, 100B to other devices. Each power tool 100A, 100B has a motor 115 housed within the housing 105. The motor includes a rotor, a stator, and a shaft that rotates about a longitudinal axis, driving an output shaft 120 by generating a rotational output. In some embodiments, the motor 115 is a three-phase permanent magnet synchronous motor (PMSM) or a brushless direct current motor (BLDC). The output shaft 120 powers a tool holder, which may be configured to receive attachments or other accessories. For example, the power tool 100A may include a chuck for mounting cutting tools or drill bits. In another embodiment, the power tool 100B may include an interface for connecting attachments such as cutting tools, grinding wheels, rotary files, polishing wheels, etc. Various attachments can be interchangeably mounted on the tool holder and may be designed with different characteristics to perform different types of operations. For example, attachments may be made of specific materials and have dimensions adapted to specific tasks. Attachment characteristics may affect the performance of the power tool 100 or impose limitations on tool operation. For example, different types of attachments may be configured to operate at different speeds or applied torques depending on their characteristics and the tasks performed. During operation of power tools 100A and 100B, the motor 115 and output shaft 120 can be controlled to rotate within a wide speed range.

[0050] Figure 3 illustrates a control system 300 for power tools 100A and 100B. The control system 300 includes a controller 304. The controller 304 is electrically and / or communicatively connected to one or more modules or components of the power tools 100A and 100B. For example, the controller 304 is electrically connected to a motor 308 (e.g., motor 115), a battery interface 312 (e.g., battery interface 110), a trigger switch 316 (connected to trigger 320), one or more sensors or sensing circuits (e.g., current sensor 324), one or more position sensors 328, one or more indicators 332, one or more temperature sensors 336, a power input module 340, and a gate controller 344. The gate controller is configured to operate multiple switches (e.g., field-effect transistors) within the switching circuit 348 to control the flow of power between the power source and the motor 308. The position sensor 328 may include a Hall effect position sensor, a magnetic sensor, an inductive sensor, a magnetic or inductive sine / cosine encoder, etc. The controller 304 includes a combination of hardware and software, and its functions include, but are not limited to: controlling the operation of power tools 100A and 100B, monitoring the operating status of power tools 100A and 100B, and activating one or more indicators 330 (e.g., LEDs).

[0051] Controller 304 includes multiple electrical and electronic components that provide power, operation control, and protection functions for components and modules within controller 304 and / or power tool 100. For example, controller 304 includes (but is not limited to) a processing unit 352 (such as a microprocessor, microcontroller, electronic processor, electronic controller, or other suitable programmable device), a memory 356, one or more input units 360, and one or more output units 364. Processing unit 352 includes a control unit 368, an arithmetic logic unit (ALU) 372, and multiple registers 376, implemented using a known computer architecture (such as a modified Harvard architecture, von Neumann architecture, etc.). Processing unit 352, memory 356, input units 360, output units 364, and various modules or circuits connected to controller 304 are interconnected, for example, via one or more control and / or data buses (e.g., common bus 380). For those skilled in the art, using one or more control and / or data buses to achieve interconnection and communication between modules, circuits, and components based on the embodiments described in this invention is a well-known technical solution.

[0052] Memory 356 is a non-transitory computer-readable medium containing, for example, a program storage area and a data storage area. The program storage area and data storage area may contain combinations 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 storage devices. Processing unit 352 is connected to memory 356 and executes software instructions that can be stored in RAM of memory 356 (e.g., during execution), ROM of memory 356 (e.g., in a generally permanent manner), or other non-volatile computer-readable media (e.g., another memory or disk). Software included in the implementation of power tool 100 may be stored in memory 356 of controller 304. This software includes, for example, firmware, one or more application programs, program data, filters, rules, one or more program modules, and other executable instructions. Controller 304 is configured to retrieve and execute instructions and other content related to the control flow and methods described in this invention from memory 356. In other configurations, controller 304 may contain more, fewer, or different components.

[0053] The battery pack interface 312 comprises a combination of mechanical components (such as rails, recesses, latches, etc.) and electrical components (such as one or more terminals) configured to enable interface connections (e.g., mechanical, electrical, and communication connections) between the power tool 100 and the battery pack. For example, power supplied by the battery pack to the power tool 100 is transmitted through the battery pack interface 312 to the power input module 340. The power input module 340 comprises a combination of active and passive components for regulating or controlling the power from the battery pack before supplying power to the controller 304. The battery pack interface 312 also supplies power to a switching circuit, which in turn drives the motor 308.

[0054] Indicator 330 includes, for example, one or more light-emitting diodes (“LEDs”). Indicator 330 may be configured to display the status or related information of power tool 100. For example, indicator 330 may be configured to indicate measured electrical characteristics of power tool 100, operating status of power tool 100, etc. In some embodiments, control system 300 may include a user input module operatedly coupled to controller 304 for selecting forward or reverse operating modes, setting torque and / or speed of power tool 100 (e.g., via torque and / or speed switches), etc. In some embodiments, the user input module includes a combination of digital and analog input / output devices required to achieve the desired operating level of power tool 100, such as one or more knobs, one or more dials, one or more switches, one or more buttons, etc.

[0055] Figure 4 illustrates a more detailed motor control system 400 for power tools 100A and 100B. This control system 400 is a schematic diagram of control system 300 and therefore may include elements described in control system 300 but not shown. In the example shown in Figure 4, motor 308 is a three-phase motor comprising U, V, and W phases. Switching circuit 348 includes multiple electronic switches (e.g., MOSFETs, with their drains forming a body diode) 410, 415, 420, 425, 430, and 435, which are connected to each phase of motor 308. In the illustrated embodiment, switching circuit 348 includes multiple high-side switches 410, 415, and 420 and multiple low-side switches 425, 430, and 435. Multiple high-side switches 410, 415, and 420 are disposed on the positive side of the current path between the U, V, and W phases of the motor 308 and the power supply 405 (e.g., a battery pack connected via battery pack interface 312). Multiple low-side switches 425, 430, and 435 are disposed on the negative side of the current path between the U, V, and W phases of the motor 308 and the power supply 405.

[0056] The control system 400 also includes one or more current sensors 445 for measuring the current supplied to the motor 308. In the embodiment shown in FIG. 4, the current sensor 445 is connected to two shunt resistors 455A and 455B, which are arranged along two phases of the motor 308. In other embodiments, more or fewer resistors (e.g., one or three) may be used to measure the current consumption of the motor 308. In other embodiments, other current sensors may be used, including Hall effect sensors, fluxgate sensors, and / or current transformers.

[0057] Multiple switches within the switching circuit 348 can be operated via the gate controller 344 to control the power flowing to each phase of the motor 308. Furthermore, the timing of the switching circuit 348 can be adjusted by modifying the motor's conduction angle and / or phase lead angle, thereby achieving greater power output and / or faster rotational speed. Typically, the conduction angle applied to brushless DC motors (such as motors 115 and 308) is set to a default value (e.g., approximately 105°, approximately 120°, between 90° and 120°, etc.). However, the conduction angle for specific phases can be increased to a maximum value, such as 180°, 235°, 240°, or any value between 180° and 240°. Increasing the conduction angle allows more current to flow through the motor windings for a longer period, resulting in higher torque. Typically, applying phase lead to a brushless DC motor (e.g., motors 115 and 308) aligns the current waveform with the motor's back electromotive force, which may weaken the motor's magnetic field. Therefore, applying phase lead to the brushless DC motor 500 may reduce its torque output and enable the motor 500 to operate at higher speeds with reduced torque output.

[0058] Figures 5 and 6 illustrate various exemplary switch configurations (or motor commutation methods) for driving and braking power tools, enabling motors (such as motors 115 and 308) to generate different ranges of braking force. Typically, braking occurs when the motor generates a force opposite to its own rotation direction. Figures 5 and 6 show an example of short-circuit braking, achieved by controlling the direction of the motor rotation-induced current to be opposite to the motor's rotation direction. Short-circuit braking can be achieved with any number of low-side switches; activating more switches will generate greater braking force. However, it should be noted that excessive braking force may not be ideal—current spikes caused by a high-speed motor may damage drive circuit components, such as sensors configured on the power bus or fuses used to prevent power surges. Hereafter, the invention refers to shorting three low-side switches as "hard braking" and shorting one or two low-side switches as "soft braking."

[0059] Figure 5 illustrates an example motor switch configuration when power tools 100A and 100B begin braking after the trigger is released. As shown in Table 505, the motors are turned on by commutation control of the high-side switches (e.g., high-side switches 410, 415, 420) (i.e., PWM duty cycle is 100%), allowing current to flow sequentially through each motor phase to drive the motor rotation. When the trigger is released or another stop signal is received, the motor enters a coasting state and applies minimum braking force. As shown in Table 510, when the motor enters the coasting state, the high-side switches are turned off (i.e., PWM duty cycle is 0%), while commutation control is applied to individual low-side switches: the conduction angle is set to 120 degrees and the phase lead angle is set to 0 degrees. Furthermore, only a single motor phase is short-circuited at a time. After coasting for a period of time, the braking force can be gradually increased. To increase braking force, the conduction angle and phase lead angle of the brake motor phase will periodically increase until they reach a maximum conduction angle of 240 degrees and a maximum phase lead angle of 60 degrees. Figure 515 shows the motor commutation state with a conduction angle of 235 degrees and a phase lead angle of 60 degrees. Due to the large values ​​of the conduction angle and phase lead angle, the two phases of the motor in Figure 515 are in a short-circuit state. It should be noted that other systems will use different maximum conduction angle and phase lead angle values. In some embodiments, a phase lead angle greater than 60 degrees can be used to achieve re-braking. In such embodiments, the conduction angle can be kept fixed (e.g., maintained at the maximum conduction angle).

[0060] Figure 6 illustrates another embodiment of braking achieved by adjusting motor commutation. Similar to Figure 5, upon receiving a stop signal, the motor enters a coasting state according to Table 510. After coasting ends, the braking force is enhanced by increasing the phase lead from 0 degrees to 60 degrees (while keeping the conduction angle constant). Before reaching a 60-degree phase lead, the conduction angle increases independently to 240 degrees. As shown in Table 600, there is an intermediate braking force point during commutation, controlled by a 60-degree phase lead and a 180-degree conduction angle. It should be noted that because the phase lead increases before the conduction angle, the motor's torque output decreases before the braking force applied to the motor increases during braking. Therefore, the braking process is gentler on the components of the drive circuit. In some embodiments, the conduction angle and lead angle increase simultaneously.

[0061] Figure 7 is a graph 700 showing the change of braking control over time. Figure 8 is a flowchart 800 for implementing the transition from soft braking to hard braking corresponding to graph 700. In step 805 (corresponding to point 710), the user releases the trigger, and the controller (e.g., controller 304) receives a signal to enter braking mode. In step 810, controller 304 is configured to control switch circuit 348 to coast the motor. As shown in Figure 7, to achieve motor coasting, switch circuit 348 closes the high-side switch and applies soft braking to the motor with minimum conduction angle and phase lead through a single low-side switch. In some embodiments, motor coasting is not performed after the trigger is released; soft braking is initiated directly. In step 810, after motor coasting ends, controller 304 controls switch circuit 348 to periodically increase the motor braking force (i.e., during soft braking). For example, controller 304 can send a braking signal to switching circuit 348, causing the conduction angle and / or phase lead to gradually increase by a certain percentage (e.g., 2%, 5%, 10%, etc.) of the maximum conduction angle and / or phase lead. As shown in Figure 7, the tool speed decreases parabolically as the braking force increases linearly. In step 820, controller 304 determines whether the braking force has reached a preset threshold. In the example shown in Table 700, this threshold is set based on the maximum conduction angle and phase lead. In other words, controller 304 is configured to continuously increase the conduction angle and phase lead of the signal used to brake the motor until the conduction angle reaches its maximum value. In other embodiments, other criteria may be used to determine the threshold. For example, as shown in Figure 9, the motor stops before the braking signal reaches the maximum conduction angle or phase lead. In the embodiment of Figure 9, a speed threshold is used to trigger the switching from soft braking to hard braking. When the motor speed decreases or drops to a speed threshold (e.g., 3000 rpm, 5000 RPM, 3000 RPM to 5000 RPM, etc.), hard braking will be initiated even if the conduction angle and / or phase lead angle have not yet reached their respective maximum values. Therefore, this threshold may additionally or alternatively include the motor speed. Finally, when the threshold is reached (corresponding to point 720), in step 825, the controller 304 operates the switching circuit 348 according to the hard braking method, thereby activating each low-side switch, resulting in a short circuit in the motor's U, V, and W phases.

[0062] Process 800 enables power tools 100A and 100B to brake rapidly while reducing the risk of overload on drive circuit components. As described below, in other embodiments, the increase in braking force may be non-linear, and the soft braking commutation curve adjustment interval may not be fixed. Furthermore, the criteria for switching from soft braking to hard braking may include additional or alternative thresholds, such as motor speed or energy value.

[0063] Figure 10 illustrates a state machine or flowchart for implementing process 800 in power tools (such as power tools 100A, 100B). In operating state 1005, controller 304 is configured to operate switch circuit 348 to drive a motor (e.g., motors 115, 308). When a trigger (e.g., trigger 320) is released, controller 304 is configured to control switch circuit 348 to coast the motor. In coasting state 1010, controller 304 can control the motor with reference to operating state 1005 when trigger pull is detected. In some embodiments, coasting state 1010 can be removed from the state diagram. In operating state 1005, controller 304 can adjust motor speed and power output based on user input (such as trigger operation). When power tools 100A, 100B are detected to be idle and motor power consumption is extremely low, controller 304 will control the motor to enter braking state 1015. After entering braking state 1015, the controller will begin operating in modulated braking state 1020, unless the trigger is pulled or other events occur. It should be noted that braking state 1015 can be a transitional state.

[0064] In the modulated braking state 1020, the controller 304 controls the switching circuit 348 to disable the high-side switch, and the low-side switch initially uses a 120-degree conduction angle and a 0-degree phase lead angle during commutation. The commutation method of the low-side switch ensures that no more than two low-side switches are in a short-circuit state at any given time (i.e., soft braking). In the modulated braking state 1020, the controller 304 can gradually increase (e.g., periodically, progressively, linearly, etc.) the conduction angle and / or phase lead angle used for braking until one of the following conditions is met: reaching the maximum conduction angle and / or the maximum phase lead angle; until the motor back EMF is below a threshold; until the motor speed reaches a speed threshold; or until the motor speed is too low to commutate, etc. In some embodiments, the speed threshold can be set, for example, between 2000 and 5000 revolutions per minute.

[0065] When the soft braking termination condition is met, the controller can enter the full braking state 1025. In this state, the controller 304 controls the switching circuit 348 via hard braking—that is, all three low-side switches are short-circuited. When a motor stop is detected (e.g., by a position sensor), the controller 304 can enter the stop state 1030. In this state, the controller 304 remains in standby or idle mode until the trigger is pulled. In some embodiments, the controller 304 can maintain hard braking in the stop state 1030. In other embodiments, multiple switches are disabled in the stop state 1030. When the trigger is detected to be pulled, the controller 304 can switch from the stop state 1030 to the coasting state 1010, at which point all hard braking is released.

[0066] Table 1 below shows the operating characteristics used by state machine 1000.

[0067]

[0068] Figures 11A and 11B are graphs 1100A and 1100B, respectively, illustrating the relationship between tool energy, tool speed, and motor current consumption during the startup phase. The rotational energy of the tool can be approximated by multiplying the sum of the measured current or power (i.e., voltage multiplied by current) by the total time required for startup. In some cases, rotational speed can also be used to approximate the rotational energy of the tool. However, as shown by comparing the rotational speed and rotational energy in graphs 1100A and 1100B, the rotational speed fails to account for the inertial torque generated by the weight of the attachments connected to the power tools 100A and 100B. Although the speed curves are similar, the kinetic energy calculated in graph 1100B, based on measurements of heavy attachments, is significantly greater than the kinetic energy in graph 1100A, based on measurements of light attachments. Therefore, in some embodiments, controller 304 can control the braking force applied to motors 115 and 308 based on the kinetic energy value measured during the tool startup phase. By controlling the motor braking force, the time required for attachment braking can be flexibly adjusted.

[0069] Figures 12 and 13 are graphs 1200 and 1300, respectively, illustrating the kinetic energy changes of a power tool during operation. Typically, when a tool starts, the motor (e.g., motors 115 and 308) accelerates and draws energy from the power source during the startup phase. After operation, the braking force output by the tool is adjusted based on the startup energy calculated during the startup phase. As shown in Figure 12, based on the measured startup energy, the tool can adjust its braking force so that the heavy-duty tool 1205 and the light-duty tool 1210 stop rotating in approximately the same amount of time. In the embodiment shown in Figure 12, braking is corrected for by a percentage difference in the baseline braking function. In other words, since the heavy-duty tool 1205 provides twice the kinetic energy, its braking force is correspondingly increased. In some embodiments, the applied braking intensity can correspond to a value in a lookup table. For example, the controller 304 can calculate a braking function value between 0 and 10 based on the measured startup energy. Each value calculated by the controller 304 can correspond to different commutation curves (such as coasting, hard braking, soft braking with a 140-degree conduction angle, etc.) and different timing sequences.

[0070] In the embodiment shown in Figure 13, the operating force and braking force are regulated according to a closed-loop PI (proportional-integral) control algorithm. In this embodiment, the setpoint is determined based on the energy value calculated through acceleration measurement. For example, during normal operation, the controller is configured to maintain the energy of tools 100A and 100B at the operating speed (e.g., 10,000 RPM) and adjust the motor power supply to maintain the setpoint speed. In embodiments with modulated braking functionality, the PI controller can also achieve speed control through variable braking. For example, when the setpoint speed is set to 0, the controller can apply additional braking to the motor according to one of the aforementioned methods.

[0071] Figure 14 is a flowchart illustrating the process 1400 of controlling a power tool at different operating phases. In step 1405, controller 304 is configured to determine the operating parameters of the power tool during the startup phase. In some embodiments, the controller may determine the energy level by measuring startup energy or initial speed. After determining the operating parameters, in step 1410, the controller is configured to calculate a brake adjustment value based on the operating parameters. In some embodiments, controller 304 reduces the applied braking force by adjusting the motor commutation during braking. Alternatively, controller 304 may not increase the applied braking force over time, or may extend the time interval between increases in braking force. An example of calculating the brake adjustment value is to configure a lookup table to provide a commutation curve (e.g., conduction angle and phase lead angle) corresponding to the desired braking force output. In step 1415, electronic controller 304 controls switching circuit 348 according to the calculated commutation curve, thereby controlling the motor commutation according to the calculated brake adjustment value during the braking phase. In some embodiments, as the required braking force increases, the commutation parameters of the motor (such as conduction angle and phase lead angle) increase accordingly. In some embodiments, the controller 304 may also additionally or alternatively apply hard braking to the motor.

[0072] Figure 15 shows graph 1500, which illustrates the energy levels of power tools 100A and 100B and the known thermal limits of the motors. Graph 1500 is similar to Figures 12 and 13, but in addition to the determined starting energy level and corresponding braking force (step 1605), it also includes a thermal cutoff point—which the controller 304 can use to disable the braking function to extend tool life. Therefore, in the corresponding flowchart of method 1600 shown in Figure 16, in step 1610, the controller 304 receives a signal from a thermistor or other temperature sensor (e.g., temperature sensor 336) and determines the motor temperature based on this sensor signal. After receiving the temperature signal, in step 1615, the controller 304 compares the temperature signal with a preset threshold temperature to determine whether the motor is overheated and cannot continue braking. As shown in Figure 15, the threshold temperature can be set to a temperature value below the motor's thermal limit. The threshold temperature can also be set according to the operating parameters of the power tool (such as starting energy), setting different limits for low-energy starting and high-energy starting tools. When the motor temperature is determined to be greater than or equal to a threshold temperature, the controller 304 prevents the power switch circuit 348 from performing a braking operation in step 1620. In some embodiments, the controller 304 controls the power switch circuit to enter a coasting state. When the motor temperature is determined to be lower than the threshold temperature, the controller 304 may control the power switch circuit 348 to brake the motor in step 1625. In some embodiments, the motor may be braked using the soft-to-hard braking transition method according to the present invention. In other embodiments, the motor may brake based on a determined braking force corresponding to the motor starting energy, motor rotational energy, etc.

[0073] Figure 17 shows a diagram 1700 illustrating another embodiment of braking controlled based on the rotational energy measured by the motor. As shown in diagram 1700, at the start of braking, the slope of heavy-energy braking is lower than that of light-energy braking. The slope of heavy-energy tools has been reduced to slowly decrease the torque on the attachments. For the braking cycle of light-energy attachments, the motor can brake quickly with a lower risk of damage. Therefore, grouping different starting energy levels based on a threshold and adjusting the braking curve according to the grouping may be advantageous.

[0074] Figure 18 is a flowchart of process 1800 for braking a power tool based on high-energy and low-energy groupings. During operation, in step 1805, controller 304 is configured to determine the tool's operating parameters. These operating parameters may include temperature, motor energy (e.g., starting energy), etc. Based on the operating parameters, in step 1810, controller 304 is configured to determine the tool's grouping. For example, in some embodiments, the operating parameter is motor energy (e.g., motor starting energy). If the motor energy exceeds a preset threshold, controller 304 may use a reduced torque mode or a first braking configuration for braking; conversely, if the motor energy is below the threshold, controller 304 uses a rapid braking mode or a second braking configuration. In rapid braking mode (step 1815), electronic controller 304 achieves rapid braking by controlling the power switching circuit. For example, controller 304 may adjust the motor commutation during braking as described above to enhance braking force. In the reduced torque mode of step 1820, electronic controller 304 is configured to control power switching circuit 348 to slowly reduce motor torque. In some embodiments, controller 304 may adjust the commutation of the motor during braking to reduce the applied braking force. Alternatively, controller 304 may not increase the applied braking force over time, or may extend the interval period for increasing the braking force over time.

[0075] Figure 19 shows another schematic diagram 1900 illustrating a specific implementation of the braking control. In the illustrated embodiment, the controller 304 operates the motor to set a static braking torque, rather than continuously braking for a specific period of time. It should be noted that a minimum torque value below the attachment mounting torque ensures that tools 100A and 100B firmly hold the attachments. When controlling the motor according to the static torque embodiment, the entire braking cycle maintains only a single commutation curve (e.g., static braking torque) until the motor comes to a complete stop.

[0076] Therefore, the embodiments described herein provide various methods and implementations for commutation braking. Various features and advantages are detailed in the appended claims.

Claims

1. A power tool, comprising: case; The motor is installed inside the housing; A power switch circuit configured to control the power supplied from a power source to the motor; as well as An electronic controller connected to the power switch circuit is configured as follows: Control the power switching circuit to apply soft braking force. Controlling the conduction angle and phase lead angle to increase soft braking force, and When the conduction angle reaches the maximum conduction angle and the phase lead angle reaches the maximum phase lead angle, the power switch circuit is controlled to apply a hard braking force.

2. The power tool as claimed in claim 1, wherein the power switch circuit includes a first high-side switch, a second high-side switch, a third high-side switch, a first low-side switch, a second low-side switch, and a third low-side switch.

3. The power tool as described in claim 2, wherein, To apply soft braking force, the electronic controller is configured to control two of the first low-side switch, the second low-side switch, and the third low-side switch to be in an active state.

4. The power tool as described in claim 2, wherein, To apply soft braking force, the electronic controller is configured to control one of the first low-side switch, the second low-side switch, and the third low-side switch to be in an active state.

5. The power tool of claim 1, wherein the maximum conduction angle is 180 degrees.

6. The power tool of claim 1, wherein the maximum conduction angle is 180 degrees to 240 degrees.

7. The power tool of claim 1, wherein the maximum phase lead angle is 60 degrees.

8. A power tool, comprising: case; The motor is installed inside the housing; A power switch circuit configured to control the power supplied from a power source to the motor; as well as An electronic controller connected to the power switch circuit is configured as follows: Control the power switching circuit to apply soft braking force. Monitor the speed of the motor. Controlling the conduction angle and phase lead angle to increase soft braking force, and When the motor speed drops to a speed threshold, the power switch circuit is controlled to apply a hard braking force.

9. The power tool of claim 8, wherein the power switch circuit comprises: First high-side switch, second high-side switch, third high-side switch, first low-side switch, second low-side switch and third low-side switch.

10. The power tool as claimed in claim 9, wherein, To apply soft braking force, the electronic controller is configured to control two of the first low-side switch, the second low-side switch, and the third low-side switch to be in an active state.

11. The power tool as claimed in claim 9, wherein, To apply soft braking force, the electronic controller is configured to control one of the first low-side switch, the second low-side switch, and the third low-side switch to be in an active state.

12. The power tool of claim 8, wherein the speed threshold is 3,000 rpm to 5,000 rpm.

13. The power tool as claimed in claim 9, wherein, To apply hard braking, the electronic controller is configured to keep the first low-side switch, the second low-side switch, and the third low-side switch active.

14. The power tool of claim 8, wherein the power switch circuit applies hard braking force before the conduction angle reaches the maximum conduction angle and before the phase lead angle reaches the maximum phase lead angle.

15. A power tool, comprising: case; The motor is installed inside the housing; A power switch circuit configured to control the power supplied from a power source to the motor; as well as A sensor configured to measure the operating parameters of the power tool; as well as An electronic controller, connected to the sensor and the power switch circuit, is configured to: The system receives signals from the sensor, the signals being correlated with the operating parameters of the power tool. During the startup phase, the operating parameters of the power tool are determined based on the signals from the sensors. Calculate the braking adjustment value based on the operating parameters, and During the braking phase, the braking of the motor is controlled according to the braking adjustment value.

16. The power tool of claim 15, wherein the electronic controller is further configured to: When the operating parameters are determined to be below a predetermined threshold, the power switch circuit is controlled to brake the motor according to a first braking configuration; and When the operating parameter is determined to be greater than or equal to the predetermined threshold, the power switch circuit is controlled to brake the motor according to the second braking configuration.

17. The power tool as claimed in claim 16, wherein: The first braking configuration is a torque reduction mode; The second braking configuration is a rapid braking mode.

18. The power tool of claim 15, wherein the operating parameter is one of temperature, motor energy, or motor speed.

19. The power tool of claim 18, wherein the operating parameter is the starting energy of the motor during the starting phase.

20. The power tool of claim 15, wherein the braking force applied during the braking phase is set according to the operating parameters.

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