A brushless motor, a control method and an application method

Abstract

The present invention relates to the technical field of brushless motors, and in particular to a brushless motor, a control method and an application method, including: a motor housing; a rotor assembly is installed in the motor housing; a cylindrical outer shell, one end of which is provided with a closed end face; a magnet unit is evenly distributed on the inner wall of the cylindrical outer shell; an output shaft is coaxial with the cylindrical outer shell and passes through the closed end face; a stator assembly includes an iron core sleeved on the output shaft; the iron core has stator teeth, and the tooth width of the stator teeth becomes larger from the direction close to the axis to the direction far from the axis, and a limiting block is arranged at one end of the stator tooth close to the axis; the winding coils are arranged in a double-layer distribution to form three phases; one end of a bracket is fixedly connected to the iron core, and the other end is fixedly connected to the motor housing; a bearing assembly is sleeved on the output shaft to support the output shaft; a PCB board is arranged on the rear housing; a position sensor is used to detect the position of the magnet unit; an electronic commutator is used to control commutation; a PWM unit is used to adjust the input voltage and current. The present invention can improve the smoothness and stability of the brushless motor during operation.

Description

Technical Field

[0001] The present invention relates to the technical field of brushless motors, and particularly to a brushless motor, a control method and an application method. Background Art

[0002] Although the development time of brushless motors in China is short, with the increasing maturity and improvement of technology, they have developed rapidly. Due to their characteristics of high efficiency, reliability and easy maintenance, brushless motors have been widely used in industrial automation, household appliances and other fields.

[0003] However, there are still some deficiencies in the existing brushless motors and their control methods. When the motor is running, the heat generated inside itself is difficult to dissipate; during the starting and stopping processes of the motor, traditional control methods often adopt constant-speed motion, which is likely to cause mechanical shock and affect the service life of the motor; when using linear acceleration or deceleration to control the starting and stopping of the motor, it is easy to make the object exceed the place where the user wants to stop during the process of decelerating only when receiving the stop command. In the application in real life, people not only require the brushless motor to have high efficiency and long life, but also require good smoothness and accuracy during operation, and have good stability functions in the use of electric furniture.

[0004] The present invention aims to solve the problems existing in traditional brushless motors. Summary of the Invention

[0005] The present invention provides a brushless motor, a control method and an application method, which can effectively solve the problems in the background art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] It includes: a motor housing: including a front housing and a rear housing, the front housing and the rear housing are fixedly connected;

[0008] A rotor assembly: installed in the motor housing; including a cylindrical outer shell; a magnet unit, evenly distributed circumferentially along the axis on the inner wall of the cylindrical outer shell; an output shaft, the output shaft is coaxial with the cylindrical outer shell and passes through the front housing;

[0009] A stator assembly: including an iron core, the output shaft passes through the iron core; the iron core is provided with stator teeth that are circumferentially distributed along the axis and extend towards the axis direction, the tooth width of the stator teeth gradually increases from the direction close to the axis to the direction far from the axis, and a limiting block is arranged at one end of the stator teeth close to the axis; a winding coil, the winding coil is arranged in a double-layer distribution, one layer is wound around one end of the stator teeth close to the axis, and the other layer is wound around one end of the stator teeth far from the axis; the winding coils form three phases; a bracket, one end is fixedly connected to the iron core, and the other end is fixedly connected to the motor housing;

[0010] Bearing assembly: sleeved on the output shaft, including a first bearing and a second bearing, for supporting the output shaft;

[0011] PCB board: disposed on the rear case; including a plurality of position sensors, with the inner wall of the cylindrical housing corresponding to the edge of the circular area on the PCB board, and the position sensors are evenly spaced for detecting the position of the magnet unit; including an electronic commutator for controlling the commutation of the brushless motor; including a PWM unit for regulating the input voltage and current of the motor.

[0012] Further, the motor housing is provided with a heat dissipation port; wind plates are circumferentially arranged along the axis on the outer wall of the cylindrical housing, and there is a certain distance between the wind plates and the motor housing.

[0013] According to the second aspect of the present invention, a method for controlling a brushless motor is further provided, including the following steps:

[0014] S00: Install the brushless motor into an object, connect the output shaft to the lead screw, and the slider moves on the lead screw; it is set that when the slider is at the position closest to the motor on the lead screw, it is at the lowest position, and when the slider is at the position farthest from the motor on the lead screw, it is at the highest position;

[0015] S10: Initialize the brushless motor and configure the PWM unit; set several special positions of the slider on the lead screw as different gears of the application; set the minimum duty cycle Dmin and the maximum duty cycle Dmax;

[0016] S20: Receive the real-time distance Pc between the position where the slider is located and the lowest position sent by the object system, receive the target gear sent by the user, and calculate the target distance Pt between the position of the target gear and the lowest position; calculate the position difference e = Pt - Pc based on the real-time distance Pc and the target distance Pt; at the same time, determine the rotation direction of the output shaft;

[0017] S30: Determine the position of the magnet unit in the rotor assembly through the position sensor, so as to control the energization of the winding coil to drive the rotation of the rotor assembly; construct a smooth acceleration curve to calculate the duty cycle Dt1 and generate a PWM signal through the duty cycle Dt1;

[0018] S40: The brushless motor adjusts the input voltage and current of the motor according to the PWM signal, so that the motor enters the acceleration period to drive the output shaft to accelerate smoothly; at the same time, during the acceleration period, at a manually set phase angle before each commutation of the motor, a certain current is applied to the winding coil of the next phase; until the duty cycle Dt1 reaches the maximum duty cycle Dmax, the motor exits the acceleration period and generates a PWM signal with the duty cycle Dmax to drive the rotation of the output shaft;

[0019] S50: When the position difference e is less than a threshold set by humans, construct a smooth deceleration curve to calculate the duty cycle Dt2 and generate a PWM signal through the duty cycle Dt2; the brushless motor adjusts the input voltage and current of the motor according to the PWM signal, so that the motor enters the deceleration period to drive the output shaft to decelerate smoothly; at the same time, during the deceleration period, a certain current is applied to the winding coil of the next phase at a phase angle set by humans before each commutation of the motor; when the duty cycle Dt2 reaches the minimum duty cycle Dmin, the motor exits the deceleration period, and the brushless motor stops inputting voltage and current, so that the output shaft stops rotating.

[0020] Further, in step S30, the specific method of constructing a smooth acceleration curve to calculate the duty cycle Dt1 is as follows:

[0021] Dt1 = Dmax·(3t1 2 - 2t1 3 );

[0022] where t1 is the timing time starting from the start of startup, and t1 ≤ 1.

[0023] Further, in step S50, the specific method of constructing a smooth deceleration curve to calculate the duty cycle Dt2 is as follows:

[0024] Dt2 = Dmax - (Dmax - Dmin)·(3t2 2 - 2t2 3 );

[0025] where t2 is the timing time starting when the position difference e is less than the threshold set by humans, and t2 ≤ 1.

[0026] Further, when the brushless motor moves according to the PWM signal during the acceleration period or the deceleration period, use a high - resolution PWM signal; between the acceleration period and the deceleration period of the brushless motor, use a low - resolution PWM signal.

[0027] Further, when in step S20, the user does not issue a target gear, making it impossible to calculate the target distance Pt, then step S50 is changed to: after receiving a real - time stop instruction issued by the user, construct a smooth deceleration curve to calculate the duty cycle Dt2 and generate a PWM signal through the duty cycle Dt2; the brushless motor adjusts the input voltage and current of the motor according to the PWM signal, so that the motor enters the deceleration period to drive the output shaft to decelerate smoothly, and when the duty cycle Dt2 reaches the minimum duty cycle Dmin, the motor exits the deceleration period, and the brushless motor stops inputting voltage and current, so that the output shaft stops rotating.

[0028] Further, when the brushless motor adjusts the motor according to the PWM signal generated by the duty cycle Dt2, start recording the number of turns a of the rotor assembly rotating around the stator assembly; when the duty cycle Dt2 reaches the minimum duty cycle Dmin, stop recording the number of turns a; the brushless motor inputs voltage and current with the duty cycle Dmin, and uses the electronic commutator to reverse the rotation of the rotor assembly until the reverse rotation number of turns b = a, then the brushless motor stops inputting voltage and current, and the output shaft stops rotating.

[0029] Further, after the output shaft stops rotating, record the memory distance Pd between the current slider and the lowest position. The user can choose to set the memory distance Pd as the memory gear, and the user can select the memory gear as the target gear next time; there is one memory gear, and each time the memory gear is set, it will overwrite the previous memory gear.

[0030] According to the third aspect of the present invention, there is also provided a method for applying a brushless motor, including:

[0031] Install the brushless motor inside the column of the lifting table to drive the up and down movement of the lifting table;

[0032] Alternatively, install the brushless motor inside the sofa or the reclining chair seat to drive the movement of the footrest and the backrest of the seat to achieve a change in posture.

[0033] Through the technical solution of the present invention, the following technical effects can be achieved:

[0034] The present invention designs a brushless motor, a control method and an application method; the stator tooth width is gradually changed to optimize the magnetic field distribution and reduce the cogging effect, so as to achieve the purpose of improving the operation stability of the motor; through the rotation of the rotor assembly during operation, the air plate is driven for heat dissipation; through the construction of a smooth curve, the vibration brought to the object when the motor starts and stops is reduced, and the smoothness and stability during operation are improved; the targeted operation in two cases also accurately stops the object at the position desired by the user. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1 It is a schematic structural diagram of the brushless motor in the embodiment of the present invention;

[0037] Figure 2Schematic diagram of the iron core and stator teeth in the brushless motor according to the embodiment of the present invention;

[0038] Figure 3 Step diagram of the brushless motor control method according to the embodiment of the present invention;

[0039] Figure 4 Smooth acceleration curve function diagram in the brushless motor control method according to the embodiment of the present invention;

[0040] Figure 5 Smooth deceleration curve function diagram in the brushless motor control method according to the embodiment of the present invention;

[0041] Reference numerals: 11, front housing; 12, rear housing; 13, heat dissipation port; 21, cylindrical outer shell; 21a, wind plate; 22, magnet unit; 23, output shaft; 3, stator assembly; 31, iron core; 32, stator teeth; 32a, limiting block; 33, bracket; 41, first bearing; 42, second bearing; 5, PCB board. Detailed implementation manners

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0043] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0044] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" 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, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0045] A brushless motor, as Figures 1 - 2 shown, includes:

[0046] Motor housing: including a front housing 11 and a rear housing 12, and the front housing 11 is fixedly connected to the rear housing 12;

[0047] Rotor assembly: Installed in the motor housing; includes a cylindrical outer shell 21; a magnet unit 22, evenly distributed circumferentially along the axis on the inner wall of the cylindrical outer shell 21; an output shaft 23, the output shaft 23 is coaxial with the cylindrical outer shell 21 and passes through the front housing 11;

[0048] Stator assembly 3: Includes an iron core 31, and the output shaft 23 passes through the iron core 31; the iron core 31 is provided with stator teeth 32 that are distributed circumferentially along the axis and extend towards the axis direction. The tooth width of the stator teeth 32 gradually increases from the direction close to the axis to the direction away from the axis. The end with a larger tooth width enhances the heat dissipation of the area and can better optimize the magnetic field distribution, reduce the cogging effect, and improve the stability and smoothness of the brushless motor during operation; a limit block 32a is provided at one end of the stator tooth 32 close to the axis; a winding coil, the winding coil is arranged in a double-layer distribution, one layer is wound around one end of the stator tooth 32 close to the axis, and the other layer is wound around one end of the stator tooth 32 away from the axis; the double-layer winding can accommodate more wires, thereby increasing the electromagnetic force and output power of the motor, and can better disperse the current and reduce the eddy current loss; the winding coils form three phases; a bracket 33, one end is fixedly connected to the iron core 31, and one end is fixedly connected to the motor housing;

[0049] Bearing assembly: Sleeved on the output shaft 23, includes a first bearing 41 and a second bearing 42, used to support the output shaft 23;

[0050] PCB board 5: Installed on the rear housing 12, so that there is no need to set up additional wiring inside the motor to connect with external objects; includes several position sensors, and the position sensors can be Hall sensors or encoders; the position sensors are evenly spaced along the edge of the circular area corresponding to the inner wall of the cylindrical outer shell 21 on the PCB board 5, used to accurately detect the position of the magnet unit 22; includes an electronic commutator, used to control the commutation of the brushless motor; includes a PWM unit, used to adjust the input voltage and current of the motor.

[0051] The operating principle of the brushless motor is to detect the position of the rotor assembly through the position sensor, and then commutate the current of the winding coils on the stator assembly 3 in a certain order (that is, detect the position of the magnetic poles of the magnet unit 22 on the rotor assembly relative to the winding coils of the stator assembly, and generate a position sensing signal at the determined position, which is processed by the signal conversion circuit and then used to control the power switch circuit to switch the winding current according to a certain logical relationship), so that the rotor assembly rotates around the stator assembly 3, driving the rotation of the output shaft 23.

[0052] Preferably, the motor housing is provided with a heat dissipation opening 13; wind plates 21a are circumferentially arranged along the axis on the outer wall of the cylindrical outer shell 21, and the wind plates 21a are at a certain distance from the motor housing; when the motor is running, the rotor assembly rotates around the stator assembly 3, thereby driving the wind plates 21a on the cylindrical outer shell 21 to also rotate around the stator assembly 3, so that the air inside the motor moves faster, and then exchanges through the heat dissipation opening 13 opened in the middle section of the motor housing, timely dissipating the heat generated during the operation of the motor, preventing the inside of the motor from overheating and damaging the components, and also avoiding the influence of heat on the operation of the motor; a circulation hole can also be opened on the rear shell 12 of the motor housing to make the air exchange inside the motor more smooth.

[0053] According to the second aspect of the present invention, there is also provided a brushless motor control method, as Figure 3 shown in, including the following steps:

[0054] S00: Install the brushless motor into an object, connect the output shaft 23 to the lead screw, and the slider moves on the lead screw, so that the slider can drive the morphological change of the object system (such as the lifting of a lifting table, the movement of the footrest and backrest of a sofa recliner); it is set that when the slider is at the position closest to the motor on the lead screw, it is at the lowest position, and when the slider is at the position farthest from the motor on the lead screw, it is at the highest position.

[0055] S10: Initialize the brushless motor and configure the PWM unit; set several special positions of the slider on the lead screw as different gears applied, and different gears correspond to different morphologies of the object system (such as the gears at different height positions of a lifting table); set the minimum duty cycle Dmin and the maximum duty cycle Dmax.

[0056] S20: Receive the real-time distance Pc between the position where the slider is located and the lowest position sent by the object system, receive the target gear sent by the user, and calculate the target distance Pt between the position where the target gear is located and the lowest position; calculate the position difference e = Pt - Pc according to the real-time distance Pc and the target distance Pt; at the same time, the positive and negative of the structure can be judged by calculating the position difference e to determine the rotation direction of the output shaft 23. For example, if it is set that when the motor rotates forward, the slider will move from the lowest position to the highest position, then when e > 0, it means that the target position is farther from the motor, and the motor needs to rotate forward to drive the slider to reach the target position.

[0057] S30: Determine the position of the magnet unit 22 in the rotor assembly through a position sensor, thereby controlling the energization of the winding coil to drive the rotation of the rotor assembly, realizing the forward and reverse rotation of the motor; construct a smooth acceleration curve to calculate the duty cycle Dt1 and generate a PWM signal through the duty cycle Dt1;

[0058] By smoothing the acceleration curve, the motor does not immediately reach its maximum speed or maximum torque when starting up, but increases gradually. This can significantly reduce the impact on mechanical components within the object at the moment of startup. Moreover, smooth acceleration reduces the instantaneous acceleration during startup, thereby reducing vibration and noise caused by rapid acceleration. Such a startup effectively reduces the vibration of the object caused by the motor at the beginning of startup, making the user feel more stable and comfortable when using the object.

[0059] S40: The brushless motor adjusts the input voltage and current of the motor according to the PWM signal, causing the motor to enter the acceleration period to drive the output shaft 23 to accelerate smoothly. At the same time, within the acceleration period, at a manually set phase angle before each commutation of the motor, a certain current is applied to the winding coil of the next phase. The current value is usually a fixed value set manually. When the duty cycle Dt1 reaches the maximum duty cycle Dmax, the motor exits the acceleration period and generates a PWM signal with the duty cycle Dmax to drive the rotation of the output shaft 23, enabling the object to move to the target gear faster.

[0060] In the traditional commutation process, the motor operates on the first-phase winding. When the motor reaches the commutation point, the current of the first phase is cut off, and the current of the second phase is turned on. After commutation, the current of the second phase rises from zero, while the current of the first phase rapidly drops from its original value to zero. The rapid change in current causes the torque generated by the motor to change rapidly, resulting in torque ripple. Torque ripple causes vibration and noise in the motor during commutation, affecting the smooth operation of the motor. By applying a certain current to the winding of the next phase in advance at a phase angle before each commutation, the current of the next phase does not start rising from zero, making the change in current smoother and reducing the torque ripple caused by the current jump, thereby making the motor operation more stable.

[0061] S50: When the position difference e is less than a manually set threshold, a smooth deceleration curve is constructed to calculate the duty cycle Dt2 and generate a PWM signal through the duty cycle Dt2. The brushless motor adjusts the input voltage and current of the motor according to the PWM signal, causing the motor to enter the deceleration period to drive the output shaft 23 to decelerate smoothly. The remaining position difference e is zeroed through the deceleration period to reach the position of the target gear, without exceeding the position of the target gear because it enters the deceleration period only when reaching the target gear. At the same time, within the deceleration period, at a manually set phase angle before each commutation of the motor, a certain current is applied to the winding coil of the next phase. When the duty cycle Dt2 reaches the minimum duty cycle Dmin, the motor exits the deceleration period. At this time, since the movement amplitude of the object driven by the motor is already very small, the brushless motor stops inputting voltage and current, causing the output shaft 23 to stop rotating, and will not bring a sudden sense of vibration to the user.

[0062] Such as Figure 4As shown, in step S30, constructing a smooth acceleration curve to calculate the duty cycle Dt1 is specifically as follows:

[0063] Dt1 = Dmax·(3t1 2 - 2t1 3 );

[0064] Wherein, t1 is the timing time starting from the start of startup, and t1 ≤ 1;

[0065] The constructed smooth acceleration curve will not generate a strong sense of vibration similar to linear acceleration when starting up and reaching the maximum duty cycle Dmax, so as to ensure that there is no mutation in the duty cycle Dt1 during the entire acceleration period; as t1 changes from 0 to 1, through the smooth acceleration curve, the duty cycle Dt1 can smoothly increase from 0 to Dmax within 1 second, reaching the maximum duty cycle.

[0066] As Figure 5 shown, in step S50, constructing a smooth deceleration curve to calculate the duty cycle Dt2 is specifically as follows:

[0067] Dt2 = Dmax - (Dmax - Dmin)·(3t2 2 - 2t2 3 );

[0068] Wherein, t2 is the timing time starting when the position difference e is less than the artificially set threshold, and t2 ≤ 1;

[0069] Similarly, the constructed smooth deceleration curve also ensures that there is no mutation in the duty cycle Dt2 during the entire deceleration period; and by the way of (Dmax - Dmin), the duty cycle Dt2 in the deceleration period is only reduced to the minimum duty cycle Dmin, which also avoids the vibration caused by the motor directly decaying to 0 after high-speed operation; moreover, by decaying to the minimum duty cycle Dmin, it can also well solve the influence brought about when the user does not issue the target gear at the beginning.

[0070] Preferably, when the brushless motor moves according to the PWM signal during the acceleration period or the deceleration period, a high-resolution PWM signal is used; between the acceleration period and the deceleration period of the brushless motor, a low-resolution PWM signal is used; during the acceleration period or the deceleration period, the motor speed is relatively low, and at this time, very fine speed control is required; using a high-resolution PWM signal can achieve more detailed current adjustment, thereby improving the control accuracy and smooth operation of the motor speed; in the high-speed range, the motor speed is relatively high, and at this time, the accuracy requirement for speed control is relatively low; using a lower-resolution PWM signal can simplify the control algorithm, reduce the calculation burden, and still maintain sufficient control accuracy.

[0071] In some embodiments, when in step S20, the user does not issue a target gear position, making it impossible to calculate the target distance Pt, step S50 is changed to: after receiving the real-time stop instruction issued by the user, construct a smooth deceleration curve to calculate the duty ratio Dt2 and generate a PWM signal through the duty ratio Dt2; the brushless motor adjusts the input voltage and current of the motor according to the PWM signal, so that the motor enters the deceleration period, driving the output shaft 23 to decelerate smoothly. When the duty ratio Dt2 reaches the minimum duty ratio Dmin, the motor exits the deceleration period, and the brushless motor stops inputting voltage and current, causing the output shaft 23 to stop rotating; in life, when the user uses an object, they do not know what position is more suitable for their own usage requirements, so they do not select a gear position but instead control the movement themselves until they move to a position they think is appropriate and then issue a stop instruction. For example, when raising and lowering a lifting table, the user will first choose to raise the table and issue a stop instruction when it reaches the appropriate position; at this time, we need to change the premise of constructing the smooth deceleration curve to calculate the duty ratio Dt2 in order to make the motor enter the deceleration period.

[0072] When the brushless motor adjusts the motor according to the PWM signal generated by the duty ratio Dt2, start recording the number of turns a of the rotor assembly rotating around the stator assembly 3; when the duty ratio Dt2 reaches the minimum duty ratio Dmin, stop recording the number of turns a; the brushless motor inputs voltage and current with the duty ratio Dmin and uses an electronic commutator to make the rotor assembly rotate in the reverse direction until the reverse rotation number of turns b = a, then the brushless motor stops inputting voltage and current, causing the output shaft 23 to stop rotating. In the case where the user does not issue a target gear position but issues a stop instruction, the motor enters the deceleration period. At this time, the movement of the slider on the lead screw during the deceleration period, which brings the movement of the object, has exceeded the position where the user wants the object to stop; therefore, record the number of turns a of the rotor assembly rotating around the stator assembly 3 during the deceleration period, and then through the slow callback position of the minimum duty ratio Dmin, finally stop at the position where the user issues the stop instruction, avoiding the vibration caused by sudden stop and improving the stability and accuracy during the operation.

[0073] Preferably, after the output shaft 23 stops rotating, record the memory distance Pd between the current slider and the lowest position. The user can choose to set the memory distance Pd as a memory gear position, and the user can select the memory gear position as the target gear position next time; only one memory gear position is set, and each time the memory gear position is set, it will overwrite the previous memory gear position. In the above situation of the user, the object stops at a position that the user feels is appropriate and wants to stop. The user can choose to set the memory distance Pd between the slider on the lead screw and the lowest position at this time as the memory gear position, so that the object can reach this position faster and more conveniently the next time it is used, improving the flexibility of use.

[0074] According to the third aspect of the present invention, there is also provided a method for applying a brushless motor, including:

[0075] Install the brushless motor inside the column of the lifting table, which is used to drive the telescopic movement of the column of the lifting table, so as to drive the up and down movement of the lifting table;

[0076] Alternatively, install the brushless motor inside seats such as sofas and reclining chairs, and connect it to the screw rod slider structure, which is used to drive the movement of the footrest and backrest of the seat, realize the switching and change of the sitting posture, TV posture and lying posture of the seat, and meet the needs of users.

[0077] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A brushless motor control method, characterized in that, Use the following brushless motor, including: Motor housing: including a front housing and a rear housing, the front housing is fixedly connected to the rear housing; Rotor assembly: installed in the motor housing; including a cylindrical outer shell; a magnet unit evenly distributed circumferentially along the axis on the inner wall of the cylindrical outer shell; an output shaft, the output shaft is coaxial with the cylindrical outer shell and passes through the front housing; Stator assembly: including an iron core, the output shaft passes through the iron core; the iron core is provided with stator teeth distributed circumferentially along the axis and extending towards the axis direction, the tooth width of the stator teeth gradually increases from the direction close to the axis to the direction far from the axis, and a limiting block is arranged at one end of the stator teeth close to the axis; winding coils, the winding coils are arranged in a double layer, one layer is wound around one end of the stator teeth close to the axis, and the other layer is wound around one end of the stator teeth far from the axis; the winding coils form three phases; a bracket, one end is fixedly connected to the iron core, and one end is fixedly connected to the motor housing; Bearing assembly: sleeved on the output shaft, including a first bearing and a second bearing for supporting the output shaft; PCB board: arranged on the rear housing; including a plurality of position sensors, the position sensors are evenly spaced along the edge of the circular area corresponding to the inner wall of the cylindrical outer shell on the PCB board for detecting the position of the magnet unit; including an electronic commutator for controlling the commutation of the brushless motor; including a PWM unit for adjusting the input voltage and current of the motor; The method includes the following steps: S00: Install the brushless motor into an object, connect the output shaft to a lead screw, and the slider moves on the lead screw; set the position of the slider closest to the motor on the lead screw to be the lowest, and the position of the slider farthest from the motor on the lead screw to be the highest; S10: Initialize the brushless motor and configure the PWM unit; set several special positions of the slider on the lead screw as different gears of the application; set the minimum duty cycle Dmin and the maximum duty cycle Dmax; S20: Receive the real-time distance Pc between the position of the slider and the lowest position sent by the object system, receive the target gear sent by the user, and calculate the target distance Pt between the position of the target gear and the lowest position; calculate the position difference e = Pt - Pc according to the real-time distance Pc and the target distance Pt; at the same time, judge the rotation direction of the output shaft; S30: Determine the position of the magnet unit in the rotor assembly through the position sensor, so as to control the energization of the winding coils to drive the rotation of the rotor assembly; construct a smooth acceleration curve to calculate the duty cycle Dt1 and generate a PWM signal through the duty cycle Dt1; The specific method of constructing a smooth acceleration curve to calculate the duty cycle Dt1 is: Dt1 = Dmax·(3t1 2 - 2t1 3 ); where t1 is the timing time starting from the start, and t1 ≤ 1.

2. The brushless motor control method according to claim 1, wherein, It also includes the following steps: S40: The brushless motor adjusts the input voltage and current of the motor according to the PWM signal, so that the motor enters the acceleration period to drive the output shaft to accelerate smoothly; at the same time, during the acceleration period, a certain current is applied to the winding coils of the next phase at a manually set phase angle before each commutation of the motor; When the duty cycle Dt1 reaches the maximum duty cycle Dmax, the motor exits the acceleration period and generates a PWM signal with the duty cycle Dmax to drive the rotation of the output shaft; S50: When the position difference e is less than the artificially set threshold, construct a smooth deceleration curve to calculate the duty cycle Dt2 and generate a PWM signal through the duty cycle Dt2; The brushless motor adjusts the input voltage and current of the motor according to the PWM signal, so that the motor enters the deceleration period to drive the output shaft to decelerate smoothly; at the same time, during the deceleration period, at a phase angle set artificially before each commutation of the motor, apply a certain current to the winding coil of the next phase; When the duty cycle Dt2 reaches the minimum duty cycle Dmin, the motor exits the deceleration period, and the brushless motor stops inputting voltage and current, so that the output shaft stops rotating; Specifically, constructing a smooth deceleration curve to calculate the duty cycle Dt2 is as follows: Dt2 = Dmax - (Dmax - Dmin)·(3t2 2 - 2t2 3 ); Wherein, t2 is the timing time starting when the position difference e is less than the artificially set threshold, and t2 ≤ 1.

3. The brushless motor control method according to claim 1, wherein, When the brushless motor moves according to the PWM signal during the acceleration period or the deceleration period, use a high-resolution PWM signal; between the acceleration period and the deceleration period of the brushless motor, use a low-resolution PWM signal.

4. The brushless motor control method according to claim 1, characterized in that, When in step S20, the user does not issue a target gear, making it impossible to calculate the target distance Pt, then change step S50 to: after receiving the real-time stop instruction issued by the user, construct a smooth deceleration curve to calculate the duty cycle Dt2 and generate a PWM signal through the duty cycle Dt2; The brushless motor adjusts the input voltage and current of the motor according to the PWM signal, so that the motor enters the deceleration period to drive the output shaft to decelerate smoothly. When the duty cycle Dt2 reaches the minimum duty cycle Dmin, the motor exits the deceleration period, and the brushless motor stops inputting voltage and current, so that the output shaft stops rotating.

5. The brushless motor control method according to claim 4, wherein When the brushless motor adjusts the motor according to the PWM signal generated by the duty cycle Dt2, start recording the number of turns a of the rotor assembly rotating around the stator assembly; when the duty cycle Dt2 reaches the minimum duty cycle Dmin, stop recording the number of turns a; the brushless motor inputs voltage and current with the duty cycle Dmin, and uses an electronic commutator to make the rotor assembly rotate in the reverse direction until the reverse rotation number of turns b = a, then the brushless motor stops inputting voltage and current, so that the output shaft stops rotating.

6. The brushless motor control method according to claim 5, characterized in that, After the output shaft stops rotating, record the memory distance Pd between the current slider and the lowest position. The user can choose to set the memory distance Pd as the memory gear. The user can select the memory gear as the target gear next time; only one memory gear is set, and each time the memory gear is set, it will overwrite the previous memory gear.

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