Electric tool and control method thereof

Abstract

The invention discloses an electric tool and a control method thereof. The electric tool includes: a functional member; the motor drives the functional part to work; the power supply device at least supplies power to the motor; the driving circuit is connected between the power supply device and the motor and transmits the electric energy provided by the power supply device to the motor from the direct-current bus; the controller is used for controlling the operation of the motor; the detection device is connected with the motor and the controller and is configured to detect a load parameter of the motor; the controller is configured to determine a first voltage vector according to a first modulation degree under the condition that the load capacity parameter exceeds a corresponding threshold value, perform overmodulation on the first voltage vector to obtain a first modulation voltage vector, and output a first pulse width modulation signal corresponding to the first modulation voltage vector to the driving circuit; the first modulation degree is greater than or equal to 0.9069 and less than or equal to 1; the voltage utilization rate, the loading capacity and other related performance of the electric tool can be improved.

Description

Technical Field

[0001] This application relates to the technical field of power tools, and particularly to a power tool and its control method. Background Art

[0002] Currently, various tools such as cutting, fastening, and impact tools widely used in different scenarios such as construction and gardening mostly use electric energy supply for driving. There is a motor in the power tool that is controlled by a controller to operate. Conventionally, the controller can drive the motor to rotate in a six-step commutation manner, and the stator current can only provide six discrete and discontinuous torques. This traditional motor drive control scheme has gradually become difficult to meet the increasingly high performance requirements of users for power tools, and is more ineffective in problems such as the load-carrying capacity of the tool, temperature rise conditions, and service life.

[0003] This section provides background information related to this application, and this background information is not necessarily prior art. Summary of the Invention

[0004] One objective of this application is to solve or at least mitigate some or all of the above problems. To this end, one objective of this application is to provide a power tool and its control method.

[0005] To achieve the above objective, this application adopts the following technical solutions:

[0006] A power tool includes: a functional component; a motor for driving the functional component to work; a power supply device for at least supplying power to the motor; a drive circuit connected between the power supply device and the motor for delivering the electric energy provided by the power supply device from the DC bus to the motor; a controller for controlling the operation of the motor; wherein, the power tool further includes a detection device connected to the motor and the controller and configured to detect the load parameter of the motor; the controller is configured to, when the load parameter exceeds the corresponding threshold, determine a first voltage vector according to a first modulation degree, perform overmodulation on the first voltage vector to obtain a first modulated voltage vector, and output a first pulse width modulation signal corresponding to the first modulated voltage vector to the drive circuit; the first modulation degree is greater than or equal to 0.9069 and less than or equal to 1.

[0007] In some embodiments, the controller is configured to, when the load parameter does not exceed the corresponding threshold, determine a second voltage vector according to a second modulation degree, and output a second pulse width modulation signal corresponding to the second voltage vector to the drive circuit; the second modulation degree is greater than or equal to 0 and less than 0.9069.

[0008] In some embodiments, the controller is configured to determine a second voltage vector based on a second modulation index when a load parameter does not exceed a corresponding threshold, overmodulate the second voltage vector to obtain a second modulated voltage vector, and output a second pulse width modulation signal corresponding to the second modulated voltage vector to a drive circuit; the second modulation index is greater than or equal to 0.9069 and less than the first modulation index.

[0009] In some embodiments, the controller is configured to control the modulation index used to generate the pulse width modulation signal to smoothly transition from the second modulation index to the first modulation index when the load parameter changes from not exceeding the corresponding threshold to exceeding the corresponding threshold; and / or, control the modulation index to smoothly transition from the first modulation index to the second modulation index when the load parameter changes from exceeding the corresponding threshold to not exceeding the corresponding threshold.

[0010] In some embodiments, the controller is configured to control the modulation index to linearly increase from the second modulation index to the first modulation index within a first preset duration when the load parameter changes from not exceeding the corresponding threshold to exceeding the corresponding threshold; and / or, control the modulation index to linearly decrease from the first modulation index to the second modulation index within a second preset duration when the load parameter changes from exceeding the corresponding threshold to not exceeding the corresponding threshold.

[0011] In some embodiments, the controller is configured to directly switch the modulation index used to generate the pulse width modulation signal from the second modulation index to the first modulation index when the load parameter changes from not exceeding the corresponding threshold to exceeding the corresponding threshold; and / or, control the modulation index to directly switch from the first modulation index to the second modulation index when the load parameter changes from exceeding the corresponding threshold to not exceeding the corresponding threshold.

[0012] In some embodiments, the controller is configured to overmodulate a portion of the first voltage vector that exceeds the linear modulation region to obtain a first modulated voltage vector; and / or, overmodulate a portion of the second voltage vector that exceeds the linear modulation region to obtain a second modulated voltage vector.

[0013] In some embodiments, the load parameter of the motor includes one or more of the current, voltage, speed, torque, and freewheeling time of the motor.

[0014] In some embodiments, the phase current waveform of the motor is substantially sinusoidal, and the phase voltages are substantially 120° out of phase with each other.

[0015] An electric tool, comprising: a functional component; a motor for driving the functional component to work; a power supply device for at least supplying power to the motor; a drive circuit connected between the power supply device and the motor for delivering the electric energy provided by the power supply device from a DC bus to the motor; a controller for controlling the operation of the motor; wherein, the controller is configured to adopt different modulation degrees under different load quantity parameters of the motor.

[0016] A control method for an electric tool, wherein the method comprises: a detection device of the electric tool detecting the load quantity parameter of the motor of the electric tool; when the load quantity parameter exceeds a corresponding threshold, the controller of the electric tool determining a first voltage vector according to a first modulation degree, and overmodulating the first voltage vector to obtain a first modulated voltage vector; the controller outputting a first pulse width modulation signal corresponding to the first modulated voltage vector to the drive circuit of the electric tool; and the first modulation degree being greater than or equal to 0.9069 and less than or equal to 1.

[0017] The advantages of the present application are as follows: the controller of the electric tool adjusts the motor control means according to the current actual load quantity, adopts an appropriate modulation degree to overmodulate the voltage vector under the heavy load condition where the load quantity exceeds the threshold, and outputs a corresponding pulse width modulation signal to the drive circuit, so as to improve the voltage utilization rate under the heavy load condition, reduce the current amplitude and the temperature rise of the drive circuit, and improve the related performances of the electric tool such as the load-carrying capacity, the working duration under heavy load, and the service life. Description of the Drawings

[0018] Figure 1 is a perspective view of an electric tool shown in an embodiment of the present application;

[0019] Figure 2 is Figure 1 the electrical control schematic diagram of the electric tool shown;

[0020] Figure 3a is Figure 2 a schematic diagram of the controller of the electric tool determining the voltage vector shown;

[0021] Figure 3b is Figure 2 a schematic diagram of the controller of the electric tool determining the modulated voltage vector shown;

[0022] Figure 4a is Figure 2 a schematic diagram of the phase voltage of the motor of the electric tool under a low modulation degree shown;

[0023] Figure 4b is Figure 2 a schematic diagram of the phase voltage of the motor of the electric tool under a high modulation degree shown;

[0024] Figure 5a is Figure 2Schematic diagram of the motor phase current under the low power mode in the electric tool shown;

[0025] Figure 5b is Figure 2 Schematic diagram of the motor phase current under the high power mode in the electric tool shown;

[0026] Figure 6 is Figure 2 Electrical control schematic diagram of the controller controlling the operation of the motor in the electric tool shown;

[0027] Figure 7 Is the control flow chart of the electric tool shown in an embodiment of the present application. Detailed implementation manners

[0028] Before explaining any embodiment of the present application in detail, it should be understood that the present application is not limited to the structural details and component arrangements described in the following description or shown in the above drawings.

[0029] In the present application, the terms "comprising", "including", "having" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or device comprising such element.

[0030] In the present application, the term "and / or" is a relationship describing associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present application generally represents an "and / or" relationship between the associated objects before and after.

[0031] In the present application, the terms "connect", "combine", "couple", "mount" may be direct connection, combination, coupling or mounting, or may be indirect connection, combination, coupling or mounting. Among them, by way of example, direct connection means that two parts or components are connected together without the need for an intermediate member, and indirect connection means that two parts or components are respectively connected to at least one intermediate member, and these two parts or components are connected through the intermediate member. In addition, "connect" and "couple" are not limited to physical or mechanical connection or coupling, and may include electrical connection or coupling.

[0032] In this application, those of ordinary skill in the art will understand that relative terms used in connection with quantities or conditions (such as "about", "approximately", "substantially", etc.) are intended to include the recited value and have the meaning indicated by the context. For example, such relative terms include at least the degree of error associated with the measurement of a particular value, tolerances resulting from manufacturing, assembly, use, etc. associated with a particular value. Such terms should also be considered to disclose a range defined by the absolute values of two endpoints. Relative terms may refer to plus or minus a certain percentage (such as 1%, 5%, 10% or more) of the indicated value. Numerical values without the use of relative terms should also be disclosed as specific values with tolerances. In addition, when expressing relative angular positional relationships (such as substantially parallel, substantially perpendicular), "substantially" may refer to plus or minus a certain number of degrees (such as 1 degree, 5 degrees, 10 degrees or more) based on the indicated angle.

[0033] In this application, those of ordinary skill in the art will understand that the functions performed by components can be performed by one component, multiple components, one part, or multiple parts. Similarly, the functions performed by parts can also be performed by one part, one component, or a combination of multiple parts.

[0034] In this application, the directional terms such as "upper", "lower", "left", "right", "front", "rear", etc. are described based on the orientation and positional relationship shown in the drawings, and should not be construed as limiting the embodiments of this application. In addition, in the context, it should also be understood that when it is mentioned that one element is connected "above" or "below" another element, it can not only be directly connected "above" or "below" another element, but also be indirectly connected "above" or "below" another element through an intermediate element. It should also be understood that the directional terms such as the upper side, the lower side, the left side, the right side, the front side, the rear side, etc. not only represent the positive direction, but can also be understood as the side direction. For example, the lower side can include directly below, lower left, lower right, lower front, and lower rear, etc.

[0035] In this application, the terms "controller", "processor", "central processor", "CPU", "MCU" can be used interchangeably. When using the units "controller", "processor", "central processor", "CPU", or "MCU" to perform specific functions, unless otherwise specified, these functions can be performed by a single one of the above units or multiple of the above units.

[0036] In this application, the terms "device", "module", or "unit" can be implemented in the form of hardware or software in order to achieve a specific function.

[0037] In this application, the terms "calculate", "judge", "control", "determine", "identify", etc. refer to the operations and processes of a computer system or similar electronic computing device (such as a controller, a processor, etc.).

[0038] The technical solution proposed in this application will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0039] Figure 1 An electric tool 100 as an embodiment in this application is shown. Figure 1 The shown electric tool 100 is a circular saw 100a. The electric tool 100 in other embodiments can also be other types of handheld power tools such as a jigsaw, a reciprocating saw, an electric drill, an impact wrench, etc., or a table-type tool such as a miter saw, a table saw, etc., or an outdoor power equipment such as a lawn mower, a snow blower, etc. It can be understood that the electric tool 100 applying the technical solution of this application is not limited to the circular saw 100a, nor is it limited to the tool categories described above.

[0040] Referring to Figure 1 , the electric tool 100 includes a housing 10, an operating member 20, and a functional member 30. Among them, the housing 10 constitutes the main body of the electric tool 100, which connects or supports the above-mentioned various components and forms an accommodation space, capable of accommodating or partially accommodating the above-mentioned various components. The operating member 20 is for the user to operate to start or stop the motor 40 to be described later, or for the user to operate to adjust the speed of the motor 40 or achieve other multiple functions. The functional member 30 is a component in the electric tool 100 that actually performs operations such as cutting, fastening, grinding, and impact. Taking the circular saw 100a as an example, its functional member 30 is a circular saw blade, and the functional member 30 of other electric tools 100 can also be a chain, a drill bit, etc.

[0041] Referring to Figure 2 , in addition to the housing 10, the operating member 20, and the functional member 30, the electric tool 100 further includes a motor 40, a power supply device 50, a controller 60, a drive circuit 70, and a detection device 80. Among them, the motor 40 is the prime mover in the electric tool 100. When the motor shaft of the motor 40 rotates, it can directly or indirectly drive the functional member 30 to operate through a transmission component. In some examples, the motor 40 is a brushless motor; in other examples, the motor 40 is a sensored brushless motor. The power supply device 50 can at least supply electrical energy to the motor 40, and can also supply power to the controller 60, the detection device 70, or other related circuits. In some examples, the power supply device 50 is a battery pack, which is detachably connected to the electric tool 100; in other examples, the power supply of the electric tool 100 can also use mains electricity, an AC power supply and be realized in cooperation with related circuits such as a power adapter or voltage transformation, rectification, and voltage stabilization.

[0042] The controller 60 can be an MCU (Microcontroller Unit), an ARM (Advanced Reduced Instruction Set Computing Machine), a DSP (Digital Signal Processor), etc. It can run relevant control programs and output control signals such as Pulse-width modulation (PWM) signals to the drive circuit 70, so that the drive circuit 70 drives the motor 40 to operate in the intended manner. The drive circuit 70 is located between the power supply device 50 and the motor 40 and connects the two. At the same time, it is also connected to the controller 60 and receives control signals such as PWM signals from the controller 60. The drive circuit 70 can convert the above control signals into drive signals that finally drive the motor 40 to operate, and transmit the electrical energy provided by the power supply device 50 to the motor through the DC bus. In some examples, the drive circuit 70 can include a three-phase bridge circuit, which can be composed of three switching tubes as the upper half-bridge and three switching tubes as the lower half-bridge. The three switching tubes Q1, Q3, Q5 as the upper half-bridge are respectively connected between the power supply terminal of the power supply device 50 and each phase coil of the motor 40, and the three switching tubes Q2, Q4, Q6 as the lower half-bridge are respectively connected between each phase coil of the motor 40 and the ground wire. The above switching tubes can be field effect transistors or insulated gate bipolar transistors; in other examples, the drive circuit 70 can also be an integrated drive chip.

[0043] The detection device 80 is connected to the motor 40 and the controller 60. It can detect the current load of the motor 40 and transmit it to the controller 60. Specifically, the detection device 80 can detect at least one load parameter related to the load of the motor 40 and transmit it to the controller 60. In some embodiments, the load parameters of the motor 40 detected by the detection device 80 include but are not limited to: the current, voltage, speed, torque, freewheeling time, and temperature of the motor 40; among them, the current of the motor 40 can include its phase current, bus current, etc., the voltage of the motor 40 can include its phase voltage, bus voltage, etc., and the temperature of the motor 40 can include its MOS temperature, ambient temperature, etc.

[0044] After receiving the load parameter transmitted by the detection device 80, the controller 60 can determine whether the load parameter exceeds the corresponding threshold value, so as to distinguish whether the motor 40 is currently in an empty / light load condition or a heavy load condition. Specifically, the controller 60 can compare the above load parameter or the calculated value of the above load parameter with its corresponding threshold value. If it exceeds the threshold value, it is determined that the motor 40 is currently in a heavy load condition, otherwise it is in an empty / light load condition. In some embodiments, the controller 60 can determine that the power tool 100 is overloaded when the current speed of the motor 40 is lower than the preset speed threshold, or the current of the motor 40 exceeds the preset current threshold, or the current voltage of the motor 40 exceeds the preset voltage threshold. In other embodiments, the controller 60 can determine that the power tool 100 is overloaded when the current speed of the motor 40 is lower than the speed threshold corresponding to the current temperature of the motor 40. In still other embodiments, the controller 60 can determine that the power tool 100 is overloaded when the product of the current bus voltage of the motor 40 and the freewheeling time exceeds the preset product threshold. It can be understood that the judgment of whether the above load parameter exceeds the corresponding threshold can also be executed by the detection device 80, and the detection device 80 can transmit the judgment result to the controller 60 so that it can know whether the current load of the motor 40 belongs to a heavy load condition or an empty / light load condition. In addition, the method of detecting the current load of the motor 40 is not limited to the above comparison scheme of the load parameter and the corresponding threshold value. The purpose here is to clarify whether the current load of the motor 40 belongs to the situation where subsequent solutions need to be adopted, that is, whether it belongs to a heavy load condition, and other load detection means can also be introduced adaptively.

[0045] When the load parameter of the motor 40 exceeds the corresponding threshold value, that is, when the motor 40 is in a heavy load condition, the controller 60 can determine the corresponding first voltage vector by using the first modulation degree, and perform overmodulation on the first voltage vector to obtain the first modulated voltage vector, and then output the first pulse width modulation signal corresponding to the first modulated voltage vector to the drive circuit 70, so that the drive circuit 70 drives the motor 40 to operate according to the first pulse width modulation signal, where the first modulation degree is greater than or equal to 0.9069 and less than or equal to 1.

[0046] First, the controller 60 determines the voltage vector based on the modulation degree and outputs the corresponding pulse width modulation signal, so that the drive circuit 70 drives the motor 40 to operate according to the pulse width modulation signal will be described. Refer to Figure 3a, which shows a regular hexagon in the two-phase stationary coordinate system (α-β coordinate system) of the motor. This regular hexagon is the limit voltage vector trajectory that the controller 60 can achieve. The side length value is related to the amplitude of the DC bus voltage Udc, specifically 2 / 3Udc. The center point of the hexagon and its six vertices can form six non-zero vectors, and the magnitude of each non-zero vector is also 2 / 3Udc. Continuing from the previous text, the conduction states of the six switching tubes in the three-phase bridge circuit are represented by three-bit binary numbers. "1" and "0" respectively represent the conduction of the upper bridge switch and the lower bridge switch in a half-bridge. "100" represents the conduction of switching tubes Q1, Q6, and Q2. Then, except for (000) and (111), there are six switching tube conduction states. The above six non-zero vectors correspond to these six conduction states respectively, while (000) and (111) correspond to the zero vectors V0 and V7, that is, the center point of the hexagon. Taking Figure 3a the voltage vector Ur0 in

[0047] as an example, the voltage vector Uro can be synthesized using two non-zero vectors V4 and V6 and two zero vectors V0 and V7. Based on the synthesis relationship between the voltage vector Ur0 and the non-zero vectors and zero vectors, the controller 60 can output corresponding pulse width modulation signals to the drive circuit 70, so that the drive circuit 70 adjusts the conduction sequence and conduction time of the above six switching tubes based on the pulse width modulation signals, thereby adjusting the energization state of each phase winding in the motor 40, so that the stator generates a magnetic field suitable for the current rotor speed and position. Taking the seven-segment pulse width modulation as an example, the pulse width modulation signal corresponding to the voltage vector Ur0 will successively achieve the following switching tube conduction states: V0(000) → V4(100) → V6(110) → V7(111) → V7(111) → V6(110) → V4(100) → V0(000). The action duration of each vector in each stage can be adaptively adjusted according to the angle θ between the voltage vector Ur and the α-axis.

[0048]

[0049] Combined with Figure 3a , an inscribed circle and a circumscribed circle are made for the above regular hexagon. The radius of the inscribed circle is The radius of the circumscribed circle is Udc. It can be seen that when the amplitude of the voltage vector does not exceed the radius of the inscribed circle, the voltage vector is always located within the above-mentioned regular hexagon. This voltage vector can be reproduced by synthesizing the above non-zero and zero vectors. The area inside the inscribed circle is denoted as the linear modulation region, and this inscribed circle is called the voltage limit circle. When the amplitude of the voltage vector exceeds the radius of the inscribed circle, the voltage vector may be located outside the above-mentioned regular hexagon, and there is a possibility that this voltage vector cannot be reproduced by synthesizing the above non-zero and zero vectors. The region between the above-mentioned inscribed circle and the circumscribed circle is denoted as the overmodulation region. The radius of the voltage limit circle, which is the boundary between the linear modulation region and the overmodulation region, is The modulation index m at the boundary is equal to That is, 0.9069. In other words, when the value range of the modulation index m is from 0 to 0.9069, the voltage vector Ur is located in the linear modulation region, and when the value range of the modulation index m is from 0.9069 to 1, the voltage vector Ur is located in the overmodulation region.

[0050] When the load parameter provided by the detection device 80 detected by the controller 60 exceeds the corresponding threshold value, that is, when the motor 40 is in a heavy load condition, the controller 60 will use a first modulation index m1 with a value range from 0.9069 to 1 to determine the corresponding first voltage vector Ur1. In some embodiments, the first modulation index m1 can be a preset fixed value. For example, it can be preset according to the actual scenario requirements during the performance test of the power tool. In other embodiments, the first modulation index m1 can also be a variable value that is dynamically adjusted within the value range from 0.9069 to 1. For example, the first modulation index m1 can be positively correlated with the current load of the motor 40.

[0051] The first voltage vector Ur1 obtained from the first modulation index m1 greater than or equal to 0.9069 and less than or equal to 1 will exceed the above-mentioned voltage limit circle. The controller 60 will perform overmodulation on the first voltage vector Ur1 to obtain a first modulated voltage vector Ur1'. The first modulated voltage vector Ur1' obtained by overmodulation will fall within the above-mentioned regular hexagon range. The controller 60 can output a corresponding first pulse width modulation signal based on the first modulated voltage vector Ur1' to enable the drive circuit 70 to drive the motor 40 to operate based on this first pulse width modulation signal. Refer to Figure 4b which shows the phase voltage waveform of the motor 40 when the controller 60 controls the operation of the motor 40 using the first modulation index m1 with a value range from 0.9069 to 1; and Figure 4a shows the phase voltage waveform of the motor 40 when the controller 60 controls the operation of the motor 40 using the modulation index m with a value range from 0 to 0.9069.

[0052] It should be noted here that under the overload condition, the rotational speed of the motor 40 of the power tool 100 will slow down, the current will increase, and the temperature will rise, so that its performance, feel, working duration, etc. cannot be maintained in a good state under the light load condition. Therefore, in this application, for the overload condition, the controller 60 in the power tool 100 will use a modulation degree in the numerical range of 0.9069 to 1 to over-modulate the voltage vector. As the magnitude of the voltage vector increases, the utilization rate of the DC bus voltage will increase, the maximum rotational speed that the motor 40 can reach will increase correspondingly, and when the power of the power supply device 50 is constant, the phase current amplitude of the motor 40 will decrease relatively, and the temperature rise of components such as field effect transistors in the drive circuit 70 will decrease, so that the load-carrying capacity of the motor 40 is improved, and the performance such as the temperature rise condition and service life is improved.

[0053] There are various optional implementation methods for the controller 60 to over-modulate the first voltage vector Ur1 to obtain the first modulated voltage vector Ur1'. In some embodiments, the controller 60 can over-modulate the part of the first voltage vector Ur1 that exceeds the above linear modulation region. In one example, referring to Figure 3b , if the first voltage vector Ur1 obtained based on the first modulation degree m1 exceeds the inscribed circle range and exceeds the regular hexagon range, the principle of compensating the angle while keeping the amplitude unchanged can be followed, and the first voltage vector Ur1 is rotated until it just falls within the hexagon, so that the corresponding first modulated voltage vector Ur1' is determined by the first voltage vector Ur1. The angle between the first voltage vector Ur1 and the α-axis in the two-phase stationary coordinate system is θ1, and the angle between the first voltage modulation vector Ur1' and the α-axis is θ2. (θ2 - θ1) is the compensation angle from the first voltage vector Ur1 to the first voltage modulation vector Ur1'.

[0054] It should be noted here that the definition of the above modulation degree m is not unique. In some examples, the modulation degree m is defined as the amplitude ratio of the voltage vector Ur to 2 / 3Udc; as shown in the following formula (2). In other examples, the modulation degree m is defined as the amplitude ratio of the voltage vector Ur to ; as shown in the following formula (3). Continuing from the previous text, Ur is equal to As the demarcation point between the linear modulation region and the over-modulation region, it is denoted as the over-modulation point. Under the definition formula (2), m is equal to is the overmodulation point. When m is in the range of [0, 0.866], linear modulation is performed. When m is in the range of [0.866, 1], overmodulation is performed. m equal to 1 is the maximum modulation point. At the maximum modulation point, the controller 60 actually adopts a six-step commutation method to achieve the operation control of the motor 40. Under the definition formula (3), m equal to 1 is the overmodulation point. When m is in the range of [0, 1], linear modulation is performed. When m is in the range of [1, 1.15], overmodulation is performed. m equal to 1.15 is the maximum modulation point, as shown in Table 1 below. Therefore, when the definition of the modulation degree or modulation coefficient m is different, the numerical range of the first modulation degree m used by the controller 60 in the power tool 100 for heavy load conditions can also be from 0.866 to 1, or from 1 to 1.15. Similar situations should be included in the protection scope of the above solution.

[0055]

[0056]

[0057]

[0058] Table 1

[0059] In some embodiments, when the load parameter transmitted by the detection device 80 detected by the controller 60 of the power tool 100 does not exceed the corresponding threshold, that is, in the no-load / low-load condition, the second modulation degree m2 with a value between 0 and the above first modulation degree m1 can be used to determine the corresponding second voltage vector Ur2 for subsequent generation and output of the second pulse width modulation signal. Considering that the larger the modulation degree m used by the controller 60, the larger the size of the voltage vector and the higher the utilization rate of the DC bus voltage. However, at the same time, the increase in the modulation degree m will also cause an increase in the phase current harmonics and interference of the motor 40 and may cause mutations. Refer to Figure 5a , which shows the phase current waveform of the motor 40 in the ideal state. When the value of the modulation degree m is small, the phase current of the motor 40 basically presents the waveform shown in Figure 5a . When the value of the modulation degree m increases and approaches 1, for example, when m is equal to 0.98, refer to Figure 5b, the phase current waveform of the motor 40 will generate a large number of spikes or oscillations. Under no-load / light-load conditions, the amplitude of the phase current of the motor 40 is relatively small. If a modulation index m with a relatively large value is used, the harmonic components will cause more significant interference to the phase current of the motor 40. This problem is particularly serious when the motor 40 is a sensorless brushless motor that relies on its current / voltage to achieve operation control. Therefore, in this application, the controller 60 in the power tool 100 will use a second modulation index m2 with a value range of 0 to a first modulation index m1 to determine a second voltage vector for no-load / light-load conditions, which is different from heavy-load conditions, to reduce harmonic components and ensure the stability of the phase current, so that the power tool 100 can maintain a good working state under no-load / light-load conditions and avoid problems such as speed fluctuations.

[0060] In some embodiments, the value range of the second modulation index m2 is 0 to 0.9069, then the controller 60 can output a second pulse width modulation signal corresponding to the second voltage vector Ur2 to the drive circuit 70. In other examples, the value range of the second modulation index m2 is 0.9069 to the first modulation index m1, then the controller 60 will over-modulate the second voltage vector Ur2 obtained from the second modulation index m2 to obtain a second modulated voltage vector Ur2', and output a second pulse width modulation signal corresponding to the second modulated voltage vector Ur2' to the drive circuit 70. The over-modulation of the second voltage vector Ur2 to obtain the second modulated voltage vector Ur2' can refer to the relevant description of the over-modulation of the first voltage vector Ur1 to obtain the first modulated voltage vector Ur1' in the previous text.

[0061] In some embodiments, in order to ensure smooth operation and stable performance of the motor 40, when the load parameter of the motor 40 changes from no-load / light-load conditions where it does not exceed the corresponding threshold to heavy-load conditions where it exceeds the corresponding threshold, the controller 60 of the power tool 100 can control the modulation index used to generate the pulse width modulation signal to smoothly transition from the second modulation index m2 to the first modulation index m1. During this process, the determination of the voltage vector and the output of the pulse modulation signal are implemented based on the modulation index during the smooth transition; observing the phase voltage of the motor 40, it will Figure 4a gradually change from the waveform shown to Figure 4bThe waveforms shown. Correspondingly, when changing from a heavy load condition to an empty / light load condition, the controller 60 can also control the modulation degree to smoothly transition from the first modulation degree m1 to the second modulation degree m2. In some embodiments, when the electric tool 100 changes from an empty / light load condition to a heavy load condition, the controller 60 will control the modulation degree m to linearly increase from the second modulation degree m2 to the first modulation degree m1 within the first preset duration T1; in other embodiments, when the electric tool 100 changes from a heavy load condition to an empty / light load condition, the controller 60 will control the modulation degree m to linearly decrease from the first modulation degree m1 to the second modulation degree m2 within the second preset duration T2. Among them, the first preset duration T1 and the second preset duration T2 can be equal or unequal. In one example, the first preset duration T1 and the second preset duration T2 are 80 ms. In addition, the transition between the first modulation degree m1 and the second modulation degree m2 can also be non-linear, and the transition duration between the first modulation degree m1 and the second modulation degree m2 can also be a non-fixed value.

[0062] In other embodiments, in order to make the operation control of the motor 40 quickly respond to the change of the load amount of the electric tool 100, when the load amount parameter of the motor 40 changes from an empty / light load condition where it does not exceed the corresponding threshold to a heavy load condition where it exceeds the corresponding threshold, the controller 60 of the electric tool 100 can control the modulation degree used to generate the pulse width modulation signal to directly switch from the second modulation degree m2 to the first modulation degree m1; observing the phase voltage of the motor 40, it will change from Figure 4a the waveform shown to Figure 4b the waveform shown immediately. Correspondingly, when changing from a heavy load condition to an empty / light load condition, the controller 60 can also control the modulation degree to directly switch from the first modulation degree m1 to the second modulation degree m2.

[0063] In some embodiments, referring to Figure 6 , the controller 60 can include a speed loop, a current distribution unit, a first current loop, a second current loop, a current conversion unit, a voltage conversion unit, and a vector modulation unit; the detection device 80 can include a current detection module and a position / speed detection module. Among them, the speed loop is set with a target speed n0 and is connected to the speed detection module to obtain the actual speed n of the motor 40 detected by it. The speed loop will determine the current target current Is0 of the motor 40 based on the target speed n0 and the actual speed n.

[0064] The current distribution unit is connected to the above speed loop and will distribute the direct-axis target current Id0 and the quadrature-axis target current Iq0 based on the target current Iso. The above target current Iso, direct-axis target current Id0, and quadrature-axis target current Iq0 are all vectors with magnitude and direction. The direct-axis target current Id0 and the quadrature-axis target current Iq0 are perpendicular to each other and the target current Is0 can be synthesized by the two.

[0065] The current conversion unit is connected to the current detection module, and can obtain the phase currents Iu, Iv, and Iw of the three-phase winding and convert them from the three-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the direct-axis actual current Id and the quadrature-axis actual current Iq. The first current loop is connected to the current distribution unit and the current conversion unit, and can obtain and determine the first regulated voltage Ud based on the above-mentioned direct-axis target current Id0 and the direct-axis actual current Id. The second current loop is connected to the current distribution unit and the current conversion unit, and can obtain and determine the second regulated voltage Uq based on the above-mentioned quadrature-axis target current Iq0 and the quadrature-axis actual current Iq.

[0066] The voltage conversion unit is connected to the first current loop and the second current loop, and can obtain the first regulated voltage Ud and the second regulated voltage Uq and convert them from the two-phase rotating coordinate system to the two-phase stationary coordinate system to obtain the first voltage control quantity Ua and the second voltage control quantity Ub. The vector modulation unit is connected to the voltage conversion unit, and can obtain the first voltage control quantity Ua and the second voltage control quantity Ub, and perform linear modulation or overmodulation on the first voltage control quantity Ua and the second voltage control quantity Ub based on the current modulation degree, and then generate the corresponding pulse width modulation signal and output it to the drive circuit 70.

[0067] In some embodiments, adopting the above control scheme, the waveforms of the three-phase phase currents of the motor 40 in the power tool 100 can be kept substantially sinusoidal, and the three-phase phase voltages can be kept substantially 120° out of phase with each other.

[0068] In summary, in the present application, the controller 60 of the power tool 100 adapts to the current load of the motor 40, determines the voltage vector using different modulation degrees, and outputs the corresponding pulse modulation signal. The drive circuit 70 adjusts the energized state of the stator windings in the motor 40 to be suitable for the load based on different pulse width modulation signals. Thus, in some embodiments, the controller 60 of the power tool 100 uses different modulation degrees when the load parameter of the motor 40 is different. In some embodiments, in order to achieve a rapid increase in the speed of the motor 40 under no-load / light-load conditions, the controller 60 of the power tool 100 may also, when the load parameter of the motor 40 does not exceed the corresponding threshold, use a second modulation degree to determine a second voltage vector and over-modulate the second voltage vector to obtain a second voltage vector, and then output a second pulse width modulation signal corresponding to the second modulated voltage vector to the drive circuit 70, so that the drive circuit 70 drives the motor 40 to operate according to the second pulse width modulation signal, where the second modulation degree is greater than or equal to 0.9069 and less than or equal to 1; and in order to ensure the stable operation of the motor 40 under heavy-load conditions, the controller 60 may, when the load parameter exceeds the corresponding threshold, use a first modulation degree to determine a first voltage vector and generate and output a subsequent first pulse width modulation signal according to the first voltage vector, where the first modulation degree is greater than or equal to 0 and less than the above second modulation degree.

[0069] Correspondingly, Figure 7 A control flowchart of a power tool is shown, and the process may include:

[0070] 710, the detection device 80 of the power tool 100 detects the load parameter of the motor 40 of the power tool 100;

[0071] 720, when the above load parameter exceeds the corresponding threshold, the controller 60 of the power tool 100 determines a first voltage vector from the first modulation degree and over-modulates the first voltage vector to obtain a first modulated voltage vector;

[0072] 730, the controller 60 outputs a first pulse width modulation signal corresponding to the first modulated voltage vector to the drive circuit 70 of the power tool 100; the first modulation degree is greater than or equal to 0.9069 and less than or equal to 1.

[0073] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the above embodiments do not limit the present application in any form. Any technical solutions obtained by using equivalent replacements or equivalent transformations fall within the protection scope of the present application.

Claims

1. An electric tool, comprising: Functional component; A motor for driving the functional component to operate; A power supply device for at least supplying power to the motor; A drive circuit connected between the power supply device and the motor for delivering the electric energy provided by the power supply device from the DC bus to the motor; A controller for controlling the operation of the motor; Wherein, the power tool further includes a detection device connected to the motor and the controller and configured to detect the load parameter of the motor; The controller is configured to, when the load parameter exceeds the corresponding threshold, determine a first voltage vector according to a first modulation degree, perform overmodulation on the first voltage vector to obtain a first modulated voltage vector, and output a first pulse width modulation signal corresponding to the first modulated voltage vector to the drive circuit; the first modulation degree is greater than or equal to 0.9069 and less than or equal to 1.

2. The electric tool according to claim 1, wherein, The controller is configured to, when the load parameter does not exceed the corresponding threshold, determine a second voltage vector according to a second modulation degree and output a second pulse width modulation signal corresponding to the second voltage vector to the drive circuit; the second modulation degree is greater than or equal to 0 and less than 0.9069.

3. The electric tool according to claim 1, wherein, The controller is configured to, when the load parameter does not exceed the corresponding threshold, determine a second voltage vector according to a second modulation degree, perform overmodulation on the second voltage vector to obtain a second modulated voltage vector, and output a second pulse width modulation signal corresponding to the second modulated voltage vector to the drive circuit; the second modulation degree is greater than or equal to 0.9069 and less than the first modulation degree.

4. The electric tool according to claim 2 or 3, wherein, The controller is configured to, when the load parameter changes from not exceeding the corresponding threshold to exceeding the corresponding threshold, control the modulation degree used for generating the pulse width modulation signal to smoothly transition from the second modulation degree to the first modulation degree; and / or, when the load parameter changes from exceeding the corresponding threshold to not exceeding the corresponding threshold, control the modulation degree to smoothly transition from the first modulation degree to the second modulation degree.

5. The electric tool according to claim 4, wherein, The controller is configured to, when the load parameter changes from not exceeding the corresponding threshold to exceeding the corresponding threshold, control the modulation degree to linearly rise from the second modulation degree to the first modulation degree within a first preset duration; and / or, when the load parameter changes from exceeding the corresponding threshold to not exceeding the corresponding threshold, control the modulation degree to linearly drop from the first modulation degree to the second modulation degree within a second preset duration.

6. The electric tool according to claim 2 or 3, wherein, The controller is configured to, when the load parameter changes from not exceeding the corresponding threshold to exceeding the corresponding threshold, control the modulation degree used for generating the pulse width modulation signal to directly switch from the second modulation degree to the first modulation degree; and / or, when the load parameter changes from exceeding the corresponding threshold to not exceeding the corresponding threshold, control the modulation degree to directly switch from the first modulation degree to the second modulation degree.

7. The electric tool according to any one of claims 1 to 3, wherein, The controller is configured to over-modulate the part of the first voltage vector that exceeds the linear modulation region to obtain the first modulated voltage vector; and / or over-modulate the part of the second voltage vector that exceeds the linear modulation region to obtain the second modulated voltage vector.

8. The electric tool according to claim 1, wherein, The load parameter of the motor includes one or more of the current, voltage, speed, torque, and freewheeling time of the motor.

9. The electric tool according to claim 1, wherein, The phase current waveform of the motor is substantially sinusoidal, and the phase voltages are substantially 120° out of phase with each other.

10. An electric tool, comprising: Functional component; A motor for driving the functional component to operate; A power supply device for at least supplying power to the motor; A drive circuit connected between the power supply device and the motor for delivering the electric energy provided by the power supply device from the DC bus to the motor; A controller for controlling the operation of the motor; Wherein, the controller is configured to adopt different modulation degrees under different load parameters of the motor.

11. A control method for an electric tool, wherein, The method includes: The detection device of the power tool detects the load parameter of the motor of the power tool; When the load parameter exceeds the corresponding threshold, the controller of the power tool determines a first voltage vector according to a first modulation degree, and over-modulates the first voltage vector to obtain a first modulated voltage vector; The controller outputs a first pulse width modulation signal corresponding to the first modulated voltage vector to the drive circuit of the power tool; the first modulation degree is greater than or equal to 0.9069 and less than or equal to 1.

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