Positioning brake method for a lift-regulating induction motor and lift device

Abstract

This invention provides a positioning and braking method for a sensorless motor used in height adjustment and a height-adjustable table, relating to the field of motor control technology. The method includes: Step S1, before the sensorless motor reaches the target height, applying direct current to the stator winding of the sensorless motor to compensate the electrical angle of the sensorless motor to a preset value; Step S2, controlling the electrical angle of the sensorless motor to maintain the preset value until it finally stabilizes and stops at the target height. The beneficial effects are: by applying direct current to the stator winding, a static magnetic field is formed, achieving a braking and stopping effect, ensuring the elimination of the sensorless motor's sliding phenomenon during height adjustment; by first compensating the electrical angle of the sensorless motor and then maintaining it to achieve segmented braking, rapid and reliable braking is achieved; simultaneously, by compensating the electrical angle of the sensorless motor, static sliding caused by power outages due to structural clearances such as worm gears is effectively eliminated.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a positioning braking method and lifting device for a sensorless motor used for lifting and adjusting. Background Technology

[0002] Height adjustment devices, such as adjustable desks, are essential equipment in modern office and home environments, designed to provide users with flexible and comfortable height adjustment. However, in practical applications, especially under heavy loads, the stability of adjustable desks has become increasingly apparent. The most significant issue is the short-distance slippage caused by the worm gear clearance in the motor front cover after DC braking. In other words, under heavy loads, after the upward and downward movements, the system stops operating, and the worm gear has not reached its maximum self-locking force point, causing the overall desktop height to drop. This results in the system detecting a height greater than the actual height, thus creating a height error.

[0003] For lifting devices using sensorless motors, such as height-adjustable desks using sensorless permanent magnet synchronous motors, the static descent height of the desktop cannot be accurately detected because the motor is not in an active running state after braking and locking. This results in the descent height not being reliably recorded by the system. Consequently, under repeated heavy-load operation, the height difference gradually accumulates, not only affecting the user experience but also potentially causing serious safety issues, such as the risk of the user pressing the down button and crushing objects. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a positioning braking method for a sensorless motor used for lifting and lowering adjustment, comprising:

[0005] Step S1: Before the sensorless motor rises and falls to the target height, DC current is supplied to the stator winding of the sensorless motor to compensate the electrical angle of the sensorless motor to a preset value.

[0006] Step S2: Control the electrical angle of the sensorless motor to maintain the preset value until it finally stops stably at the target height.

[0007] Preferably, in step S1, before the sensorless motor rises and falls to the target height, the step of controlling the sensorless motor to rise and fall to a preset height includes:

[0008] Step A1: Continuously calculate the current travel height and minimum deceleration travel based on the real-time lifting speed and acceleration after the sensorless motor starts;

[0009] Step A2: Calculate the current remaining travel distance based on the current travel height and the target height, and determine whether the current remaining travel distance is less than the minimum deceleration travel distance.

[0010] If not, return to step A1;

[0011] If so, then the sensorless motor is actively decelerated to a preset minimum gliding speed, and then glides to the preset height at the minimum gliding speed.

[0012] Preferably, in step S1, the direct current has a first voltage range;

[0013] In step S2, the first voltage range is lowered to the second voltage range to control the electrical angle of the sensorless motor to maintain the preset value.

[0014] Preferably, in step S1, the DC voltage component on the d-axis of the stator winding is Vd1, and the DC voltage component on the q-axis is Vq1.

[0015]

[0016] Wherein, Vbus is the bus voltage of the sensorless motor, K1 is the upper limit of the first voltage range, K2 is the lower limit of the first voltage range, Δt is the preset time step, and T1 is the duration of the DC current applied in the first voltage range.

[0017] Preferably, in step S2, the DC voltage component on the d-axis of the stator winding is Vd2, and the DC voltage component on the q-axis is Vq2.

[0018]

[0019] Wherein, Vbus is the bus voltage of the sensorless motor, K3 is the upper limit of the second voltage range, K4 is the lower limit of the second voltage range, Δt is the preset time step, and T2 is the duration of DC power application within the second voltage range.

[0020] Preferably, in step S2, after controlling the electrical angle of the sensorless motor to maintain the preset value, the method further includes configuring the DC power supply to have a preset current range and maintaining it for a first duration, and then configuring the DC power supply to have a preset current value and maintaining it for a second duration, until it finally stabilizes and stops at the target height.

[0021] Preferably, the DC current component along the d-axis of the stator winding is Id, and the DC current component along the q-axis is Iq.

[0022]

[0023] Wherein, Imax is the rated current of the sensorless motor, K5 is the upper limit of the preset current range, K6 is the lower limit of the preset current range, Δt is the preset time step, T3 is the first duration, and T4 is the second duration.

[0024] Preferably, after the sensorless motor finally comes to a stable stop at the target height, the method further includes:

[0025] The DC power is configured to maintain the preset current value until power is cut off and the system enters sleep mode.

[0026] Alternatively, the three phase lines of the sensorless motor can be short-circuited to apply short-circuit braking to the sensorless motor until it is powered off and enters a sleep state.

[0027] Preferably, when the sensorless motor controls the upward movement, the preset value is...

[0028] When the sensorless motor is controlled to move downwards, the preset value is...

[0029] Where, θ e The electrical angle of the sensorless motor when direct current is applied to the stator windings of the sensorless motor.

[0030] The present invention also provides a lifting device, including a controller and a sensorless motor. The controller is configured with a lifting program, and when the lifting program is running, it controls the sensorless motor to perform the above-described positioning braking method for lifting and braking.

[0031] The above technical solution has the following advantages or beneficial effects:

[0032] 1) By passing DC current through the stator winding, a static magnetic field is formed, which has a braking and stopping effect, ensuring the elimination of the lifting and sliding phenomenon of the sensorless motor;

[0033] 2) By first compensating the electrical angle of the sensorless motor and then maintaining segmented braking, fast and reliable braking can be achieved. At the same time, by compensating the electrical angle of the sensorless motor, static slippage caused by power failure due to structural gaps such as worm gears can be effectively eliminated. Attached Figure Description

[0034] Figure 1 A flowchart illustrating a positioning and braking method for a sensorless motor used for lifting and lowering adjustment, as a preferred embodiment of the present invention.

[0035] Figure 2 This is a flowchart illustrating the process of controlling the sensorless motor to rise and fall to a preset height, which is a preferred embodiment of the present invention.

[0036] Figure 3In a preferred embodiment of the present invention, a schematic diagram of the input voltage curve of Vd1 using cosine fitting is shown.

[0037] Figure 4 In a preferred embodiment of the present invention, a schematic diagram of the input voltage curve of Vd2 is shown;

[0038] Figure 5 In a preferred embodiment of the present invention, a schematic diagram of using linear scaling to fit the Id reference current is shown.

[0039] Figure 6 In a preferred embodiment of the present invention, a schematic diagram of the current waveforms for three stages of DC braking is provided. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment; other embodiments that conform to the spirit of the present invention may also fall within the scope of the present invention.

[0041] In a preferred embodiment of the present invention, based on the above-mentioned problems existing in the prior art, a positioning braking method for a sensorless motor for lifting and lowering adjustment is provided, such as... Figure 1 As shown, it includes:

[0042] Step S1: Before the sensorless motor rises and falls to the target height, DC current is applied to the stator winding of the sensorless motor to compensate the electrical angle of the sensorless motor to a preset value.

[0043] Step S2: Control the electrical angle of the sensorless motor to maintain the preset value until it finally stops stably at the target height.

[0044] Specifically, taking the application of a sensorless motor to a height-adjustable desk as an example, the user triggers the up or down button on the desk to raise or lower it to the target height. The overall process of raising and lowering the desk typically involves acceleration followed by deceleration and finally stopping. The positioning braking method of this invention is applied during the deceleration phase, when the desk is about to reach the target height. Preferably, before the sensorless motor reaches the target height, it is controlled to rise to a preset height. Before this, speed planning is performed based on the current travel height and the target height. Specifically, as follows... Figure 2 As shown, it includes:

[0045] Step A1: Continuously calculate the current travel height and minimum deceleration travel based on the real-time lifting speed and acceleration after the sensorless motor starts;

[0046] Step A2: Calculate the remaining travel distance based on the current travel height and the target height, and determine whether the remaining travel distance is less than the minimum deceleration travel distance.

[0047] If not, return to step A1;

[0048] If so, the sensorless motor is actively decelerated to reduce its speed to the preset minimum gliding speed, and then glides to the preset height at the minimum gliding speed.

[0049] Specifically, in this embodiment, if the current speed is v and the acceleration is a, then the minimum deceleration distance required for it to finally stop is s_dec = v. 2 / 2a. If the remaining travel distance is less than the minimum deceleration travel distance, deceleration control needs to be actively engaged until the minimum coasting speed is reached, and then coasting at that minimum coasting speed to the preset height. The above speed planning and active deceleration control adopt speed loop control. When the preset height is reached, the speed loop control is removed, and active braking mode is entered.

[0050] In a preferred embodiment of the present invention, in step S1, the direct current has a first voltage range;

[0051] In step S2, the first voltage range is lowered to the second voltage range to control the electrical angle of the sensorless motor to maintain a preset value.

[0052] Specifically, in this embodiment, the active braking mode employs a two-stage voltage braking to achieve rapid braking response. The first stage of voltage braking uses DC current with K1-K2 as a percentage of the rated voltage, preferably 70% for K1 and 50% for K2. The rated voltage is the bus voltage of the driver board of the sensorless motor, and the execution duration is T1. Further specifically, in step S1, the DC current component voltage on the d-axis of the stator winding is Vd1, and the component voltage on the q-axis is Vq1. The controller preferably uses a cosine fit to the Vd1 input voltage curve, such as... Figure 3 As shown, the specific expression is as follows:

[0053]

[0054] Wherein, Vbus is the bus voltage of the sensorless motor, K1 is the upper limit of the first voltage range, K2 is the lower limit of the first voltage range, Δt is the preset time step, and T1 is the duration of DC current application in the first voltage range.

[0055] The controller described above preferably uses a discrete method and a modulation period of Δt for drive control. Here, Δt is the preset time step, which can be 1ms, but is not limited to it.

[0056] Understandably, since sensorless motors lack position sensors for height detection, a position sensor can be added during the production stage to detect the rotor position and calibrate the application time. This allows determination of whether the electrical angle of the sensorless motor has been compensated to a preset value. If it has, the first voltage braking stage ends, and the duration of the first voltage braking stage is recorded as T1. T1 can then be stored in the controller for use during operation. When performing calibration during production, it is preferable to do so under the rated load of the sensorless motor, and more preferably under a larger load, such as 150% of the rated load, so that the sensorless motor does not slip under 150% of the rated load during operation.

[0057] More specifically, when DC current is applied to the stator windings of the sensorless motor, the electrical angle of the sensorless motor is the electrical angle θ at the initial braking moment. e When the sensorless motor controls the upward movement, the preset value is... When the sensorless motor is controlled to run downwards, the preset value is Furthermore, when using a discrete compensation method, the real-time braking electric angle during upward movement is: That is, the amount of compensation each time is When running downwards, the real-time braking electric angle is That is, the amount of compensation each time is

[0058] By providing additional compensation for the non-inductive angle, the static slippage caused by power failure due to structural clearances such as those in the worm gear can be eliminated.

[0059] The second stage of voltage braking uses DC current with K3-K4 accounting for a percentage of the rated voltage, preferably 50% for K3 and 30% for K4. The rated voltage is the bus voltage of the driver board of the sensorless motor, and the execution duration is T2. More specifically, in step S2, the DC current component voltage on the d-axis of the stator winding is Vd2, and the component voltage on the q-axis is Vq2. Preferably, the controller uses a sinusoidal fitting of the Vd2 input voltage curve, such as... Figure 4 As shown, the specific expression is as follows:

[0060]

[0061] Wherein, Vbus is the bus voltage of the sensorless motor, K3 is the upper limit of the second voltage range, K4 is the lower limit of the second voltage range, Δt is the preset time step, and T2 is the duration of DC current application in the second voltage range.

[0062] In a preferred embodiment of the present invention, after controlling the electrical angle of the sensorless motor to maintain a preset value in step S2, the method further includes configuring the DC power supply to have a preset current range and maintaining it for a first duration, and then configuring the DC power supply to have a preset current value and maintaining it for a second duration, until it finally stops stably at the target height.

[0063] Specifically, in this embodiment, the active braking mode includes a third stage of current braking, in addition to the first two voltage braking stages. This current braking stage uses DC current with K5-K6 as a percentage of the rated current, preferably 25% for K5 and 10% for K6, and the execution duration is T3. Further specifically, the DC current component on the d-axis of the stator winding is Id, and the component current on the q-axis is Iq. Preferably, the controller uses a linear proportional fitting to the Id reference current, such as... Figure 5 As shown, the specific expression is as follows:

[0064]

[0065] Where Imax is the rated current of the sensorless motor, K5 is the upper limit of the preset current range, K6 is the lower limit of the preset current range, Δt is the preset time step, T3 is the first duration, and T4 is the second duration.

[0066] The first and second durations can be customized as needed. During the first duration, linear proportional fitting of the Id reference current effectively suppresses intermittent rotor vibration. During the second duration, maintaining the current in a static mode reliably restores the structural self-locking force and allows for stable load bearing of larger loads. For example, when calibrated at 150% rated load, the static current mode can bear two to three times the rated load. The preferred current waveforms for the three stages of DC braking are as follows: Figure 6 As shown.

[0067] In a preferred embodiment of the present invention, after the sensorless motor has finally come to a stable stop at the target height, the method further includes:

[0068] Configure the DC power supply to maintain the preset current value until power is cut off and the system enters sleep mode.

[0069] Alternatively, short-circuit the three phases of the sensorless motor to short-circuit brake it until it is powered off and enters a sleep state.

[0070] Specifically, in this embodiment, if the product (such as a height-adjustable table) has requirements for load-bearing capacity under stable conditions, the current can be maintained in a static mode for as long as possible, that is, the DC power is configured to maintain a preset current value until power is cut off and the device goes into sleep mode.

[0071] Although the static current maintenance mode can stably support a larger load, there will be static power consumption and the sensorless motor will also heat up. For products with requirements on power consumption or motor heat generation (such as height-adjustable desks), it is necessary to shorten the duration of the static current maintenance mode as much as possible. After the third stage, the DC power input should be cut off and the three-phase motor line should be short-circuited to actively switch to the short-circuit braking mode. The short-circuit braking and structural self-locking force are used to keep the desktop stationary, reducing system power consumption and motor heat generation. After no operation is performed within the time limit, the system will be powered off and enter sleep mode.

[0072] The present invention also provides a lifting device, including a controller and a sensorless motor. The controller is configured with a lifting program. When the lifting program is running, it controls the sensorless motor to perform the above-mentioned positioning braking method for lifting and braking.

[0073] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included within the protection scope of the present invention.

Claims

1. A positioning and braking method for a sensorless motor used for lifting and lowering adjustment, characterized in that, include: Step S1: Before the sensorless motor rises and falls to the target height, DC current is supplied to the stator winding of the sensorless motor to compensate the electrical angle of the sensorless motor to a preset value. Step S2: Control the electrical angle of the sensorless motor to maintain the preset value until it finally stops stably at the target height.

2. The positioning and braking method according to claim 1, characterized in that, In step S1, before the sensorless motor rises and falls to the target height, the control of the sensorless motor to rise and fall to the preset height includes: Step A1: Continuously calculate the current travel height and minimum deceleration travel based on the real-time lifting speed and acceleration after the sensorless motor starts; Step A2: Calculate the current remaining travel distance based on the current travel height and the target height, and determine whether the current remaining travel distance is less than the minimum deceleration travel distance. If not, return to step A1; If so, then the sensorless motor is actively decelerated to a preset minimum gliding speed, and then glides to the preset height at the minimum gliding speed.

3. The positioning and braking method according to claim 1, characterized in that, In step S1, the DC power has a first voltage range; In step S2, the first voltage range is lowered to the second voltage range to control the electrical angle of the sensorless motor to maintain the preset value.

4. The positioning and braking method according to claim 3, characterized in that, In step S1, the DC voltage component on the d-axis of the stator winding is Vd1, and the DC voltage component on the q-axis is Vq1. Wherein, Vbus is the bus voltage of the sensorless motor, K1 is the upper limit of the first voltage range, K2 is the lower limit of the first voltage range, Δt is the preset time step, and T1 is the duration of the DC current applied in the first voltage range.

5. The positioning and braking method according to claim 3, characterized in that, In step S2, the DC voltage component on the d-axis of the stator winding is Vd2, and the DC voltage component on the q-axis is Vq2. Wherein, Vbus is the bus voltage of the sensorless motor, K3 is the upper limit of the second voltage range, K4 is the lower limit of the second voltage range, Δt is the preset time step, and T2 is the duration of DC power application within the second voltage range.

6. The positioning and braking method according to claim 1, characterized in that, In step S2, after controlling the electrical angle of the sensorless motor to maintain the preset value, the method further includes configuring the DC power supply to have a preset current range and maintaining it for a first duration, and then configuring the DC power supply to have a preset current value and maintaining it for a second duration, until it finally stabilizes and stops at the target height.

7. The positioning and braking method according to claim 6, characterized in that, The DC current component along the d-axis of the stator winding is Id, and the DC current component along the q-axis is Iq. Wherein, Imax is the rated current of the sensorless motor, K5 is the upper limit of the preset current range, K6 is the lower limit of the preset current range, Δt is the preset time step, T3 is the first duration, and T4 is the second duration.

8. The positioning and braking method according to claim 6, characterized in that, After the sensorless motor finally comes to a stable stop at the target height, it also includes: The DC power is configured to maintain the preset current value until power is cut off and the system enters sleep mode. Alternatively, the three phase lines of the sensorless motor can be short-circuited to apply short-circuit braking to the sensorless motor until it is powered off and enters a sleep state.

9. The positioning and braking method according to claim 1, characterized in that, When the sensorless motor controls the upward movement, the preset value is... When the sensorless motor is controlled to move downwards, the preset value is... Where, θ e The electrical angle of the sensorless motor when direct current is applied to the stator windings of the sensorless motor.

10. A lifting device, characterized in that, It includes a controller and a sensorless motor. The controller is configured with a lifting program. When the lifting program is running, it controls the sensorless motor to perform lifting and braking by the positioning braking method as described in any one of claims 1-9.

Images