Electric tool and control method thereof

Abstract

The invention relates to an electric tool and a control method thereof. According to the technical scheme, the method comprises the steps that a motor is controlled to be started; acquiring a current sampling value and a voltage sampling value of the motor; acquiring the motion state variation of the electric tool; calculating the working power of the motor based on the current sampling value and the voltage sampling value; when the working power of the motor is lower than a first threshold value and the motion state variable quantity of the electric tool is higher than a second threshold value, the motor is controlled to stop; therefore, the effects that the electric tool is stopped in time, and possible damage is relieved are achieved.

Description

Technical Field

[0001] The present application relates to the technical field of electric tools, and in particular to electric tools and control methods thereof. Background Art

[0002] Angle grinder, also known as grinding machine or disc grinder, is a kind of grinding tool used for cutting and grinding. Angle grinder is a portable electric tool that uses a grinding disc to cut and grind, mainly used for cutting, grinding and brushing metal and stone.

[0003] In the related art, a Chinese patent with publication number CN107053094A discloses an electric tool. The rechargeable grinder includes: a spindle; a brushless motor that rotates the spindle; a main body shell; and a switch operating handle that is arranged on the lower side of the grip and can operate the switch, and the main body shell has: a cylindrical housing portion that houses the brushless motor; a cylindrical grip that houses the switch behind the brushless motor and is formed to have a smaller diameter than the housing portion; and a battery mounting portion that mounts a battery pack behind the grip.

[0004] However, current angle grinders will continue to work after an operator makes an error in operation or a collision, which may cause harm to the operator. Summary of the invention

[0005] Based on this, it is necessary to provide an electric tool and a control method thereof to address the safety issues that may be caused by the electric tool.

[0006] In order to solve the above technical problems, this application is implemented as follows: In a first aspect, in one embodiment, there is provided an electric tool, the electric tool comprising a control device and a motor, the control method being executed by the control device to control the motor to work; the control method comprising: Controlling the motor to start; Obtaining current sampling and voltage sampling of the motor; Obtaining a change in the motion state of the electric tool; Calculate the working power of the motor based on the current sampling value and the voltage sampling value; When the working power of the motor is lower than a first threshold and the change in the motion state of the electric tool is higher than a second threshold, the motor is controlled to stop.

[0007] Optionally, the calculating the working power of the motor based on the current sampling value and the voltage sampling value specifically includes: Performing delay processing on the current sampling value to obtain a current processing value; The operating power is obtained based on the current processing value and the voltage sampling value.

[0008] Optionally, the delay processing of the current sampling value to obtain the current processing value specifically includes: Get historical current processing values; The current processed value is obtained based on the current sampling value and the historical current processed value.

[0009] Optionally, the obtaining the current processed value based on the current sampling value and the historical current processed value specifically includes: Obtaining the current processing value according to the first value and a second value positively correlated with the first value; Among them, the first value is a current sampling value of a first set weight, and the second value is a historical current processing value of a second set weight; the first set weight is smaller than the second set weight.

[0010] Optionally, the controlling the motor to stop specifically includes: The power supply to the electric motor is cut off.

[0011] Optionally, after cutting off the power supply to the motor, the method further comprises: A reverse current is applied to the motor.

[0012] In a second aspect, the present application further provides an electric tool, comprising: shell; A motor, housed in the housing; A motion detection device, disposed on the housing and detecting a motion state of the housing to output a motion signal; A working detection device, used for detecting the working state of the motor and outputting a working signal; A control device, responsive to the motion signal and the working signal and outputting a control signal; a power supply device, responsive to the control signal to selectively provide electrical energy to the motor; The control device is used to execute the control method disclosed in any of the above embodiments.

[0013] Optionally, the control device includes a data processing module, and the data processing module is used to perform delay processing on the working signal.

[0014] Optionally, the data processing module includes a data storage unit and a weight calculation unit, the data storage unit is used to store the historical processing value of the working signal, and the weight calculation unit is used to multiply the current sampling value of the working signal by the corresponding weight and add it to the historical processing value multiplied by the corresponding weight.

[0015] Optionally, the control device also includes a first comparison module, a second comparison module and a first control module, the first comparison module is used to compare the working signal after delay processing with a first threshold; the second comparison module is used to compare the motion signal with a second threshold, and the first control module outputs a control signal when the working signal after delay processing is lower than the first threshold and the motion signal is higher than the second threshold.

[0016] In an embodiment of the present application, the working state and motion signal of the power tool are detected and the motor is controlled to stop when the two parameters simultaneously meet certain conditions, so that the power tool can be stopped in time after a collision, thereby reducing the probability of injury to the operator. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the control logic relationship of an electric tool in an embodiment of the present application; Figure 2 Schematic diagram of a control method flow of an electric tool in one embodiment of the present application.

[0018] Description of the drawings: 100, motor; 110, motion detection device; 120, work detection device; 130, control device; 131, data processing module; 1311, data storage unit; 1312, weight calculation unit. Implementation

[0019] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0020] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0021] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0022] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0023] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0024] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0025] See also Figure 1 FIG1 shows a schematic diagram of the control logic relationship of an electric tool in an embodiment of the present application. An electric tool provided in an embodiment of the present application is improved based on the situation that the electric tool may cause harm to the operator when it falls or is hit just after being turned on. The electric tool includes a housing, a motor 100, a motion detection device 110, a work detection device 120, a control device 130 and a power supply device, wherein the motor 100 is accommodated in the housing to provide the power required by the electric tool.

[0026] The motion detection device 110 can be installed in the housing or on the surface of the housing. The motion detection device 110 can be an acceleration device with more than two axes, a three-axis accelerometer, or other devices for detecting acceleration. The motion detection device 110 is used to detect the motion state of the housing and output a motion signal. The working detection device 120 is used to detect the working state of the motor 100 to output a working signal. The working signal can be a power value calculated by detecting the current and voltage. The working detection device 120 can be a device for detecting current and voltage, or a sampling pin of a built-in single-chip microcomputer, as long as it can detect the current and voltage of the motor 100.

[0027] The control device 130 can be a single chip microcomputer, a controller, or other equipment for processing and controlling, as long as it can process and respond to the signal. The control device 130 responds to the motion signal and the working signal and compares the motion signal with the working signal, and outputs a control signal according to the comparison result. The power supply device can be an AC power supply or a DC power supply. After receiving the control signal, the power supply device responds and selectively provides electrical energy to the motor 100.

[0028] Preferably, the control device 130 includes a data processing module 131, which can be an operator for performing delay processing on the working signal so that the current peak in the working signal appears with a delay relative to the sampling value, and clips the signal, thereby making the power tool run smoothly and reducing jitter; and / or improving the accuracy of the judgment of the control device 130.

[0029] Preferably, the data processing module 131 includes a data storage unit 1311 and a weight calculation unit 1312, the data storage unit 1311 is used to store the historical processing value of the working signal, and the weight calculation unit 1312 is used to calculate the working signal at the current moment based on the historical working signal and the current sampling value, and the specific operation is to multiply the current sampling value of the working signal by the corresponding weight and add it to the historical processing value multiplied by the corresponding weight to obtain the current working signal. The historical processing value here is the working signal processed at the previous sampling cycle time node, and can also be the working signal processed at multiple historical sampling cycle time nodes.

[0030] Preferably, the control device 130 includes a first comparison module, a second comparison module and a first control module, wherein the first comparison module is used to compare the working signal after delay processing with the first threshold value, and the second comparison module is used to compare the motion signal with the second threshold value. The first control module is used to output a control signal to control the motor 100 to stop only when the working signal after delay processing is lower than the first threshold value and the motion signal is higher than the second threshold value.

[0031] When the power tool is in an unloaded state, which may be when the accessories of the power tool are detached from the work surface, or when the motor 100 has just started, or when the operator has not yet applied the working accessories to the work surface, the working signal after the delay processing will be lower than the first threshold. If the power tool is subjected to a severe impact, such as falling from the work surface to the ground, the motion signal will be higher than the second threshold. The impact here may be caused by the operator's misoperation, or it may be that the power tool falls to the ground in free fall, causing the speed to drop to zero in a short time, or is accelerated in the reverse direction by the reverse acceleration applied by the ground. When the working signal after the delay processing is lower than the first threshold and the motion signal is higher than the second threshold, in order to reduce the damage to the surrounding operators after the power tool rebounds, the control device 130 is configured to shut down the motor 100 at this time so that the output shaft accessories driven by the motor 100 can stop rotating.

[0032] Combination Figure 2 As shown, FIG2 shows a schematic flow chart of a control method for an electric tool in an embodiment of the present application. The control method is based on the electric tool disclosed in any of the above embodiments, and the execution subject of the method is a control device in the electric tool disclosed in any of the above embodiments; in some embodiments, the control method specifically includes: Step 210, controlling the motor to start.

[0033] Specifically, the control device first controls the motor to start. At this time, the control device controls the motor to start through the motor control circuit, so that the motor enters the working state. It can be known that the motor will first enter a no-load state without load. After the power tool contacts the working surface, the motor will turn into a loaded state. At this time, the power of the motor will change compared to the no-load state.

[0034] Step 220, obtaining the current sampling value and the voltage sampling value of the motor.

[0035] Specifically, after the control device controls the motor to start, it obtains the current sampling value and the voltage sampling value of the motor. The current sampling value and the voltage sampling value of the motor are always being detected, but the control device obtains and processes the data in a timely manner. Therefore, step 220 can also be before step 210. Based on the consideration of resource conservation, the embodiment of the present application places the operation of obtaining the current sampling value and the voltage sampling value after the motor is started.

[0036] Step 230: Obtain the change in the motion state of the power tool.

[0037] Specifically, after obtaining the current sampling value and the voltage sampling value of the motor, the control device obtains the change in the motion state of the electric tool. The change in the motion state represents the force state of the electric tool, that is, the degree of influence of the force on the change in the motion state. It can be understood that step 230 here has no necessary timing relationship with step 220, and can be performed before step 220, after step 220, or synchronously with step 220.

[0038] Step 240: Calculate the working power of the motor based on the current sampling value and the voltage sampling value.

[0039] Specifically, after obtaining the current sampling value and the voltage sampling value of the motor, the control device calculates the working power of the motor based on the current sampling value and the voltage sampling value. In one embodiment, the control device multiplies the voltage sampling value by the current sampling value to obtain the working power of the motor.

[0040] Step 250: When the working power of the motor is lower than a first threshold and the change in the motion state of the power tool is higher than a second threshold, the motor is controlled to stop.

[0041] Specifically, after calculating the working power of the motor, the control device compares the working power of the motor with a first threshold value, and compares the motion state change with a second threshold value. When the working power of the motor is lower than the first threshold value and the motion state change of the power tool is higher than the second threshold value, the motor is controlled to stop.

[0042] In another embodiment, after calculating the working power of the motor, the control device first compares the working power of the motor with a first threshold value. When the working power of the motor is lower than the first threshold value, the control device compares the change in the motion state of the power tool with a second threshold value. When the working power of the motor is lower than the first threshold value and the change in the motion state of the power tool is higher than the second threshold value, the motor is controlled to stop.

[0043] In another embodiment, after calculating the working power of the motor, the control device compares the working power of the motor with a first threshold value, and when the working power of the motor is lower than the first threshold value, the control device obtains the change in the motion state of the power tool; then the control device compares the change in the motion state of the power tool with a second threshold value, and when the working power of the motor is lower than the first threshold value and the change in the motion state of the power tool is higher than the second threshold value, the motor is controlled to stop.

[0044] In another embodiment, the control device may first compare the change in motion state and then calculate or compare the working power. This is also conceivable by those skilled in the art and is of course also within the protection scope of the embodiments of the present application.

[0045] When the working power is lower than the first threshold, it can be understood that the power tool is in a relatively unloaded state, which may be that the accessories of the power tool are detached from the working surface, or the operator has not yet applied the working accessories to the working surface, or the power of the motor cannot be transmitted to the working accessories, that is, the load of the working accessories cannot be transmitted to the motor. When the change in the motion state is higher than the second threshold, the power tool may have been subjected to a severe impact, such as falling from the working surface to the ground. When the working signal after delay processing is lower than the first threshold and the motion signal is higher than the second threshold, what may happen here is that the power tool is detached from the working surface and falls to the ground, and the motion state of the power tool changes suddenly. At this time, in order to reduce the damage to the surrounding operators after the power tool rebounds, the control device is configured to shut down the motor at this time so that the output shaft accessories driven by the motor can stop rotating.

[0046] In order to process the working power and eliminate the jitter of the working current generated during the process of the control device controlling the electric tool, step 240 may specifically include: Step 241, delay processing is performed on the current sampling value to obtain a current processing value.

[0047] Specifically, after obtaining the current sampling value and voltage sampling value of the motor, the control device performs delay processing on the current sampling value to obtain the current processing value. The current value after delay processing will have a certain preset time delay relative to the sampling value, and the peak value will also decrease. At this time, the processed working power will participate in the control of the control device again, which can reduce the jitter of the electric tool caused by the sudden increase and decrease of the working current. In the control process of the electric tool, there are constant speed and constant power processes. In the initial stage of starting, the motor is in a constant speed starting process; under load conditions, the motor is in a constant power process. When the motor is in the constant power process, if the load increases at this time, it is necessary to reduce the speed to increase the torque when it is necessary to maintain constant power. If the working current in the working power changes frequently, that is, it suddenly increases and decreases, the motor frequently switches the torque at this time, causing jitter. The sudden increase and decrease of the working current of the working power after processing is reduced, thereby reducing the jitter in the operation of the electric tool.

[0048] Step 242: Obtain operating power based on the current processing value and the voltage sampling value.

[0049] Specifically, after the control device performs delay processing on the current sampling value to obtain the current processing value, it calculates the working power based on the current processing value and the voltage sampling value. The control device multiplies the current processing value and the voltage sampling value to obtain the working power required as the control basis of the control device, so as to facilitate control according to the power and facilitate comparison with the first threshold.

[0050] The current sampling value is the current value at the current moment that can be detected by the working detection device. In order to introduce the historical factors of the working process of the power tool into the processing of the working power, step 241 specifically includes: Step 1: Obtain historical current processing values.

[0051] Specifically, before processing the current sampling value, the control device obtains the historical current processing value in advance. The historical current processing value is pre-stored in a data storage unit such as a storage device. The historical current processing value may be a current processing value before the current moment. Here, the historical current processing value may be a current processing value of the previous cycle adopted by the control device, or may be a current processing value of the previous multiple cycles adopted by the control device.

[0052] Step 2: Obtain the current processed value based on the current sampling value and the historical current processed value.

[0053] Specifically, after acquiring the historical current processing value, the control device processes the current processing value based on the current sampling value and the historical current processing value to obtain the current current processing value. At the current moment, the current sampling value and the historical current processing value are comprehensively processed to obtain the current current processing value, thereby fully introducing the historical factor into the processing process, thereby reducing the influence of the current sampling value at the current moment on the current processing value.

[0054] In order to adjust the influence of historical factors on the current value, step 2 may include the following processing: The present current processing value is obtained according to the first value and a second value positively correlated with the first value.

[0055] Specifically, the first value is the current sampling value of the first set weight, and the second value is the historical current processing value of the second set weight, where the first set weight and the second set weight can be a proportional coefficient less than 1. The sum of the first set weight and the second set weight is 1, and the positive correlation is an additive coefficient in the embodiment of the present application. In the embodiment of the present application, the current current processing value is affected by the current processing value of the previous cycle as an example for explanation. The formula for characterizing the current processing value can be I (N) = a * I (N-1) + b * ΔI (N). Among them, N is the sampling cycle timing point, which is a positive integer; I (N-1) can be the current processing value of the previous cycle, and ΔI (N) is the current sampling value. a is the weight corresponding to the current processing value of the previous cycle, that is, the second set weight, and b is the weight corresponding to the current sampling value, that is, the first set weight. When N=1, the value of I (N-1) is set to 0.

[0056] Among them, the first set weight is less than the second set weight, so that the historical current processing value has a greater influence on the current processing value than the current sampling value. In the one calculation process of the current current processing value of the embodiment of the present application, a historical value of the current processing value is used for calculation. Of course, it can be understood that two or more historical values ​​of the current processing value can also be used for calculation in the one calculation process of the current current processing value. At this time, when the historical current processing value has no corresponding numerical value, the historical current processing value is taken as 0.

[0057] In order to stop the motor, the above step 250 specifically includes: Step A, cut off the power supply to the motor.

[0058] Specifically, when the working power of the motor is lower than a first threshold and the change in the motion state of the power tool is higher than a second threshold, the control device cuts off the power supply circuit of the motor. At this time, the motor is powered off and can gradually stop under free resistance.

[0059] In order to facilitate rapid shutdown of the motor, the above step A may further include: Step B, applying reverse current to the motor.

[0060] Specifically, after cutting off the power supply to the motor, the control device can apply a current in a direction to the motor. By applying a current in a direction to the motor, the control device can promote the rapid shutdown of the motor, thereby causing the motor to stop quickly.

[0061] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A control method for an electric tool, based on the electric tool, the electric tool comprises a control device and a motor, the control method is executed by the control device and is used to control the motor to work; characterized in that: The control method comprises: Controlling the motor to start; Obtaining a current sampling value and a voltage sampling value of the motor; Obtaining a change in the motion state of the electric tool; Calculate the working power of the motor based on the current sampling value and the voltage sampling value; When the working power of the motor is lower than a first threshold and the change in the motion state of the electric tool is higher than a second threshold, the motor is controlled to stop.

2. The control method of the electric tool according to claim 1, characterized in that: The calculating of the working power of the motor based on the current sampling value and the voltage sampling value specifically includes: Performing delay processing on the current sampling value to obtain a current processing value; The operating power is obtained based on the current processing value and the voltage sampling value.

3. The control method of the electric tool according to claim 2, characterized in that: The delay processing of the current sampling value to obtain the current processing value specifically includes: Get historical current processing values; The current processed value is obtained based on the current sampling value and the historical current processed value.

4. The control method of the electric tool according to claim 3, characterized in that: The step of obtaining the current processed value based on the current sampling value and the historical current processed value specifically includes: Obtaining the current processing value according to the first value and a second value positively correlated with the first value; Among them, the first value is a current sampling value of a first set weight, and the second value is a historical current processing value of a second set weight; the first set weight is smaller than the second set weight.

5. The control method of the electric tool according to claim 1, characterized in that: The controlling the motor to stop specifically includes: The power supply to the electric motor is cut off.

6. The control method of the electric tool according to claim 5, characterized in that: After cutting off the power supply to the motor, the method further comprises: A reverse current is applied to the motor.

7. An electric tool, characterized in that: include: shell; A motor, housed in the housing; A motion detection device, disposed on the housing and detecting a motion state of the housing to output a motion signal; A working detection device, used for detecting the working state of the motor and outputting a working signal; A control device, responsive to the motion signal and the working signal and outputting a control signal; a power supply device, responsive to the control signal to selectively provide electrical energy to the motor; The control device is used to execute the control method as described in any one of claims 1-6.

8. The electric tool according to claim 7, characterized in that: The control device comprises a data processing module, and the data processing module is used for performing delay processing on the working signal.

9. The electric tool according to claim 8, characterized in that: The data processing module includes a data storage unit and a weight calculation unit. The data storage unit is used to store the historical processing value of the working signal. The weight calculation unit is used to multiply the current sampling value of the working signal by the corresponding weight and add it to the historical processing value multiplied by the corresponding weight.

10. The electric tool according to claim 8, characterized in that: The control device also includes a first comparison module, a second comparison module and a first control module. The first comparison module is used to compare the working signal after delay processing with a first threshold; the second comparison module is used to compare the motion signal with a second threshold. The first control module outputs a control signal when the working signal after delay processing is lower than the first threshold and the motion signal is higher than the second threshold.

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