Voice coil motor and method for measuring position of its mover

Abstract

The application relates to a voice coil motor and a method for measuring the position of a moving element of the voice coil motor. The voice coil motor comprises a stator, a moving element and two linear Hall sensors which are fixed on the two sides of the moving element axially symmetrically and have their device sensitive surfaces facing in opposite directions. When the moving element reciprocates in the stator, the magnetic field intensity of the linear Hall sensor sensitive surface changes, and the output of the linear Hall sensor has a one-to-one corresponding relationship with the position of the moving element. The position of the moving element can be calculated by measuring the output of the two linear Hall sensors. By measuring the change in the output of the linear Hall sensor caused by the coil current and compensating when calculating the position, the interference of the coil current on the measurement can be offset, and the position measurement precision is improved. In the case of changing the structure of the voice coil motor as little as possible, high-precision measurement of the position of the moving element of the voice coil motor is realized, and the linear Hall sensor occupies a small space, has high reliability and high integration.

Description

Technical Field

[0001] This invention relates to the field of voice coil motor technology, specifically to a voice coil motor and a method for measuring the position of its mover. Background Technology

[0002] Voice coil motors are named for their similarity to audio equipment. They have advantages such as simple structure, fast output, and convenient control, making them an ideal linear actuator that is widely used in optical equipment, semiconductor manufacturing equipment, precision machining equipment, high-precision positioning platforms, and other fields.

[0003] A voice coil motor typically consists of a housing, a stator fixed inside the housing, and a mover inserted inside the stator. It is a device that converts electrical energy into mechanical energy and enables the mover to perform linear motion within the stator.

[0004] Since the mover and stator of a voice coil motor are not connected in any direction of relative motion, the mover is susceptible to interference from external loads, friction, etc. Therefore, it is necessary to collect the position information of the mover and perform feedback closed-loop control in order to achieve high-precision positioning servo control.

[0005] In existing voice coil motor servo systems, the acquisition of mover position information usually uses grating rulers or laser displacement sensors, which are not only costly but also take up a lot of space, thus limiting the application scenarios of voice coil motors. Summary of the Invention

[0006] To address the problems existing in the prior art, one of the objectives of this invention is to provide a voice coil motor whose mover position is easy to measure and has high reliability and integration.

[0007] The second objective of this invention is to provide a method for measuring the position of the mover of a voice coil motor.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A voice coil motor includes a stator and a mover, and also includes two linear Hall sensors. The two linear Hall sensors are axially symmetrically fixed on both sides of the mover, and the sensitive surfaces of the two linear Hall sensors face opposite directions. When the mover reciprocates within the stator, the magnetic field strength through the sensitive surfaces of the linear Hall sensors changes, and the output of the linear Hall sensors has a one-to-one correspondence with the position of the mover.

[0010] Furthermore, the mover includes a mover coil frame and a voice coil motor output shaft, which are fixedly connected. Two linear Hall sensors are axially symmetrically fixed to the mover coil frame, and a coil is wound on the mover coil frame.

[0011] Furthermore, the stator includes a permanent magnet, a housing one, and a housing two. Housing one and housing two are snapped together. The permanent magnet is fixed to the inside of housing one. The mover coil frame is coaxially disposed inside the permanent magnet. The output shaft of the voice coil motor passes through the end face of housing one, and the cables of the linear Hall sensor and the coil pass through housing two.

[0012] Furthermore, the housing 2 is connected to a cable fixing block for fixing the linear Hall sensor cable and the coil cable.

[0013] A method for measuring the position of the mover of a voice coil motor includes the following steps:

[0014] When the mover moves to different positions within the stator, the position information of the mover and the corresponding outputs of the two linear Hall sensors are collected to obtain two sets of data about the position and the output.

[0015] By performing polynomial fitting on the two sets of data on position and output, the first functional relationship between the output of the two linear Hall sensors and the position information of the mover is obtained;

[0016] By measuring the outputs of two linear Hall sensors and substituting the measured values ​​into the first functional relationship, the position information of the mover can be calculated.

[0017] Furthermore, it also includes measuring the change in the output of the linear Hall sensor caused by the coil current and compensating for it when calculating the position of the mover.

[0018] Furthermore, the compensation method includes the following steps:

[0019] When the mover is in the same position within the stator, different currents are applied to the coil, and the coil current value is collected respectively, as well as the change in the output of the two linear Hall sensors relative to their output when the coil has zero current, to obtain two sets of data on the change in current and output.

[0020] By performing polynomial fitting on two sets of data on the change in current and output, a second functional relationship between the change in output of two linear Hall sensors and the coil current is obtained;

[0021] Since the two linear Hall sensors are fixed to the mover, the second functional relationship is independent of the position of the mover;

[0022] By measuring the coil current and substituting the measured value into the second functional relationship, the output change value of the linear Hall sensor caused by the coil current can be calculated. The output change value is then used for compensation in the first functional relationship, and more accurate mover position information can be calculated.

[0023] Furthermore, if the linear Hall sensor and the microcontroller used to acquire the output of the linear Hall sensor have the same power supply voltage, then no additional level conversion circuit is needed to convert the voltage of the output of the linear Hall sensor.

[0024] In summary, the present invention has the following advantages:

[0025] Two linear Hall sensors are symmetrically integrated inside the voice coil motor. When the mover reciprocates within the stator of the voice coil motor, the magnetic field strength across the sensitive surface of the linear Hall sensors changes, causing a corresponding change in the output voltage of the linear Hall sensors. There is a one-to-one correspondence between the output of the linear Hall sensors and the position of the mover in the voice coil motor. Therefore, the position information of the mover can be easily calculated by measuring the outputs of the two linear Hall sensors. This invention achieves convenient measurement of the mover position with minimal alteration to the voice coil motor structure, and also boasts high integration and reliability. Attached Figure Description

[0026] Figure 1 This is an exploded view of the voice coil motor in this embodiment.

[0027] Figure 2 This is a diagram showing the input-output characteristics of a linear Hall sensor.

[0028] In the picture:

[0029] 1-Voice coil motor output shaft; 2-House 1; 3-Permanent magnet; 4-Motor coil frame; 5-Coil; 6-Linear Hall sensor; 7-House 2; 8-Cable fixing block. Detailed Implementation

[0030] The present invention will now be described in further detail.

[0031] like Figure 1 As shown, a voice coil motor includes a stator and a mover, and also includes two linear Hall sensors 6. The two linear Hall sensors 6 are axially symmetrically fixed on both sides of the mover, and the sensitive surfaces of the two linear Hall sensors 6 face opposite directions. When the mover reciprocates within the stator, the magnetic field strength through the sensitive surface of the linear Hall sensor 6 changes, and the output of the linear Hall sensor 6 has a one-to-one correspondence with the position of the mover.

[0032] Specifically, the mover includes a mover coil frame 4 and a voice coil motor output shaft 1. The mover coil frame 4 and the voice coil motor output shaft 1 are fixedly connected. Two linear Hall sensors 6 are axially symmetrically fixed to the mover coil frame 4. A coil 5 is wound on the mover coil frame 4.

[0033] The stator includes a permanent magnet 3, a housing 1 2 and a housing 2 7. The housing 1 2 and the housing 2 7 are snapped together. The permanent magnet 3 is fixed to the inside of the housing 1 2. The mover coil frame 4 is coaxially arranged inside the permanent magnet 3. The voice coil motor output shaft 1 passes through the end face of the housing 1 2. The cables of the linear Hall sensor 6 and the coil 5 pass through the housing 2 7 and are fixed by the cable fixing block 8 outside the housing 2 7.

[0034] This embodiment utilizes the relative motion between the permanent magnet 3 and the coil 5 during the operation of the voice coil motor. A linear Hall sensor 6 is fixed to the coil 5. The relative motion between the permanent magnet 3 and the coil 5 generates a changing magnetic field, thus establishing a one-to-one correspondence between the relative positions of the permanent magnet 3 and the coil 5 and the output of the linear Hall sensor 6. Therefore, the position information of the mover can be easily calculated by measuring the outputs of the two linear Hall sensors 6. This invention achieves convenient measurement of the mover position without significantly altering the voice coil motor structure. While ensuring position measurement accuracy, it reduces the space occupied by the linear Hall sensor 6, lowers costs, and offers high integration and reliability, making it a feasible solution for a compact voice coil motor position servo control system.

[0035] A method for measuring the position of the mover of a voice coil motor includes the following steps:

[0036] When the mover moves to different positions within the stator, the position information of the mover and the corresponding outputs of the two linear Hall sensors 6 are collected to obtain two sets of data about the position and the output.

[0037] By performing polynomial fitting on the two sets of data on position and output, the first functional relationship between the output of the two linear Hall sensors 6 and the position information of the mover is obtained;

[0038] The position information of the mover can be calculated by measuring the output of the two linear Hall sensors 6 and substituting the measured values ​​into the first functional relationship.

[0039] During operation, the mover reciprocates linearly within the stator, causing the linear Hall sensor 6 to move relative to the voice coil motor stator in a linear motion. Therefore, the linear Hall sensor 6 is placed in a changing magnetic field. Utilizing this characteristic, the linear Hall sensor 6 is fixed at an appropriate position in the coil 5 to ensure that the magnetic field strength does not exceed the range of the linear Hall sensor 6 throughout the mover's entire stroke. When the mover moves to different positions, the magnetic field strength through the sensitive surface of the linear Hall sensor 6 changes, resulting in a corresponding change in the output voltage of the linear Hall sensor 6. By separately collecting the outputs of the two linear Hall sensors 6 at different positions of the voice coil motor mover, and performing polynomial fitting on the two sets of data, a first functional relationship between the outputs of the two linear Hall sensors 6 and the mover position information is obtained. When measuring the mover position information, it is only necessary to measure the outputs of the two linear Hall sensors 6, and then substitute the measured values ​​into the first functional relationship to calculate the mover position information from the output values ​​of the two linear Hall sensors 6.

[0040] Linear Hall sensor 6 can typically measure bipolar magnetic fields; please refer to [reference needed]. Figure 2 The characteristic diagram shows that in the North Pole magnetic field, the output voltage of the linear Hall sensor 6 is between 0 volts and VDD / 2 volts, and in the South Pole magnetic field, the output voltage is between VDD / 2 volts and VDD volts. It is evident that using only one linear Hall sensor 6 to measure the mover position only utilizes half of its range, and when using a microcontroller to acquire the sensor output, an additional level conversion circuit is required to convert the output voltage range of the linear Hall sensor 6 to the voltage range of the microcontroller pins. This invention uses two linear Hall sensors 6 to measure the mover position. The two linear Hall sensors 6 are axially symmetrical, and their sensitive surfaces face opposite directions, allowing full utilization of the entire range of the linear Hall sensors 6. This fixation ensures that the output voltage of one linear Hall sensor 6 is between 0 volts and VDD / 2 volts, and the output voltage of the other linear Hall sensor 6 is between VDD / 2 volts and VDD volts. Therefore, by measuring the potential difference between the output pins of the two linear Hall sensors 6, the entire range of the sensors can be utilized. Furthermore, as long as the supply voltage of the linear Hall sensor 6 is the same as the supply voltage of the microcontroller, no additional level conversion circuit is needed for voltage conversion, making the measurement more convenient.

[0041] The method for measuring the position of the mover of a voice coil motor also includes measuring the change in the output of the linear Hall sensor 6 caused by the current of the coil 5, and compensating for it when calculating the position of the mover.

[0042] When coil 5 is energized, it generates a magnetic field, interfering with the measurement of linear Hall sensor 6. Since the interference is independent of the position of the mover, the change in the output of linear Hall sensor 6 reflected by this interference is only a univariate function of the current in coil 5. Therefore, the compensation method of this invention includes the following steps:

[0043] When the mover is in the same position within the stator, different currents are applied to coil 5, and the current values ​​of coil 5 and the corresponding outputs of the two linear Hall sensors 6 are collected respectively to obtain two sets of data on current and output.

[0044] By performing polynomial fitting on the two sets of data on current and output, a second functional relationship between the output of the two linear Hall sensor 6 and the current of the coil 5 is obtained;

[0045] When measuring the position information of the mover, the current of the measuring coil 5 and the outputs of the two linear Hall sensors 6 are measured. The measured values ​​are then substituted into the second functional relationship to calculate the position information of the mover.

[0046] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for measuring the position of the mover of a voice coil motor, characterized in that: The voice coil motor includes a stator, a mover, and two linear Hall sensors. The two linear Hall sensors are axially symmetrically fixed on both sides of the mover, and the sensitive surfaces of the two linear Hall sensors face opposite directions. When the mover reciprocates within the stator, the magnetic field strength through the sensitive surfaces of the linear Hall sensors changes, and the output of the linear Hall sensors has a one-to-one correspondence with the position of the mover. The method for measuring the position of a moving part includes the following steps: When the mover moves to different positions within the stator, the position information of the mover and the corresponding outputs of the two linear Hall sensors are collected to obtain two sets of data about the position and the output. By performing polynomial fitting on the two sets of data on position and output, the first functional relationship between the output of the two linear Hall sensors and the position information of the mover is obtained; By measuring the outputs of two linear Hall sensors and substituting the measured values ​​into the first functional relationship, the position information of the mover can be calculated. It also includes measuring the change in the output of the linear Hall sensor caused by the coil current and compensating for it when calculating the position of the mover; The compensation method includes the following steps: When the mover is in the same position within the stator, different currents are applied to the coil, and the coil current value is collected respectively, as well as the change in the output of the two linear Hall sensors relative to their output when the coil has zero current, to obtain two sets of data on the change in current and output. By performing polynomial fitting on two sets of data on the change in current and output, a second functional relationship between the change in output of two linear Hall sensors and the coil current is obtained; By measuring the coil current and substituting the measured value into the second functional relationship, the output change value of the linear Hall sensor caused by the coil current can be calculated. The output change value is then used for compensation in the first functional relationship, and more accurate mover position information can be calculated.

2. The method for measuring the position of a moving part according to claim 1, characterized in that: The mover includes a mover coil frame and a voice coil motor output shaft, which are fixedly connected. Two linear Hall sensors are axially symmetrically fixed to the mover coil frame, and a coil is wound on the mover coil frame.

3. The method for measuring the position of a moving part according to claim 2, characterized in that: The stator includes a permanent magnet, a housing 1 and a housing 2. Housing 1 and housing 2 are snapped together. The permanent magnet is fixed to the inside of housing 1. The mover coil frame is coaxially installed inside the permanent magnet. The output shaft of the voice coil motor passes through the end face of housing 1. The cables of the linear Hall sensor and the coil pass through housing 2.

4. The method for measuring the position of a moving part according to claim 3, characterized in that: The housing is connected to a cable fixing block for fixing the linear Hall sensor cable and the coil cable.

5. The method for measuring the position of a moving part according to claim 1, characterized in that: The linear Hall sensor is powered by the same voltage as the microcontroller used to acquire its output.

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