A driving device and method of a voice coil motor of a camera

Abstract

The application provides a driving device and method of a voice coil motor of a camera, the driving device comprising: a control unit, which stores n / 2 time length parameters and n / 2 amplitude coefficients, and calculates n linear control signals according to a target value in an instruction from the camera, the n / 2 time length parameters and the n / 2 amplitude coefficients when driving the voice coil motor, the n linear control signals are connected to form a continuous control signal, and the control signal becomes the target value after the nth linear control signal, and n is an even number greater than or equal to 4; and a driving unit, which outputs a driving signal to drive the voice coil motor based on the control signal output by the control unit. By compensating and adjusting the control signal, the adjustment time (±5% error range) of the voice coil motor is greatly shortened.

Description

[Technical Field]

[0001] This invention relates to the field of voice coil motor (VCM) technology, and more particularly to a driving device and method for a voice coil motor in a camera. [Background Technology]

[0002] Cameras are widely used in mobile devices such as smartphones and tablets. The lens of these cameras is typically driven by a voice coil motor, which moves the lens to change its position, thereby performing autofocus on a specific subject. Achieving rapid stabilization of a mobile phone camera is a problem that the voice coil motor drive design needs to solve.

[0003] The voice coil motor typically operates by providing a driving current to the voice coil, causing the movement between the mover and stator to be proportional to the value of the driving current. When the driving current is removed, the spring force between the mover and stator causes them to return to their initial positions, and the lens is placed on the mover. Depending on the implementation, the voice coil can be used as the stator.

[0004] When driving the voice coil motor, if a target drive current is directly applied, the mover will produce a fixed-period, sinusoidal vibration (ringing phenomenon). With damping, the amplitude of the vibration will gradually decrease. However, this still results in an excessively long settling time. Figure 4 The figure shown is the position response curve of a voice coil motor when the control method without introducing the example shaping signal. The adjustment time of the voice coil motor before compensation (±5% error range) is about 43ms.

[0005] Theoretically, a reverse compensation signal could be added to the driving current to suppress this vibration. Therefore, a new technical solution is urgently needed to address the aforementioned problem. [Summary of the Invention]

[0006] One of the objectives of this invention is to provide a driving device and method for a voice coil motor in a camera, which significantly reduces the adjustment time (±5% error range) of the voice coil motor by compensating and shaping the control signal.

[0007] According to one aspect of the present invention, a driving device for a voice coil motor of a camera is provided. The driving device includes: a control unit that stores n / 2 duration parameters and n / 2 amplitude coefficients, which, when driving the voice coil motor, calculates n segments of linear control signals based on a target value from a command from the camera, the n / 2 duration parameters, and the n / 2 amplitude coefficients. The n segments of linear control signals are connected to form a continuous control signal. After the nth linear control signal, the control signal becomes the target value, where n is an even number greater than or equal to 4; and a driving unit that outputs a driving signal to drive the voice coil motor based on the control signal output by the control unit.

[0008] According to another aspect of the present invention, the present invention provides a method for driving a voice coil motor of a camera, comprising: when driving the voice coil motor, calculating n segments of linear control signals based on a target value, n / 2 duration parameters, and n / 2 amplitude coefficients from an instruction from the camera, the n segments of linear control signals being connected to form a continuous control signal, the control signal becoming the target value after the nth linear control signal, where n is an even number greater than or equal to 4; and outputting a drive signal to drive the voice coil motor based on the control signal output by the control unit.

[0009] Compared with the prior art, the present invention compensates and shapes the control signal, generates a drive signal based on the compensated and shaped control signal, and uses the drive signal to drive the voice coil motor, thus greatly reducing the adjustment time of the voice coil motor (±5% error range). [Attached Image Description]

[0010] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0011] Figure 1 This is a structural block diagram of the driving device for the voice coil motor of the camera in one embodiment of the present invention;

[0012] Figure 2 This is a waveform diagram of the first embodiment of the compensated and shaped control signal in this invention;

[0013] Figure 3 This is a waveform diagram of the second embodiment of the compensated and shaped control signal in this invention;

[0014] Figure 4 Here is an example of the position response curve of a voice coil motor when controlled by an uncompensated and shaped control signal:

[0015] Figure 5 This is an example of the position response curve of the voice coil motor when controlled using the compensated and shaped control signal in the first embodiment;

[0016] Figure 6 This is an example of the position response curve of the voice coil motor when controlled using the compensated and shaped control signal in the second embodiment.

Detailed Implementation Methods

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments. Unless otherwise specified, the terms "connected," "linked," and "connected" used herein to indicate electrical connection refer to direct or indirect electrical connection.

[0019] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "And / or" in this document includes both "and" and "or," for example, A and / or B includes three cases: A, or B, or A and B.

[0020] In this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," "coupled," etc., should be interpreted broadly; for example, they can refer to direct connection or indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] To address the problems existing in the prior art, the present invention compensates and shapes the control signal, generates a drive signal based on the compensated and shaped control signal, and uses the drive signal to drive the voice coil motor, thereby significantly reducing the adjustment time of the voice coil motor (±5% error range).

[0022] In order to suppress the vibration mentioned in the prior art and achieve precise position control of the motor mover, according to the dynamic model of the spring voice coil motor, theoretically a positive electromagnetic force should be applied first. At this time, the mover accelerates. As the spring force increases, the mover decelerates. When the speed approaches 0, it just reaches the target position, and the applied force is exactly equal to the spring force. The entire acceleration and deceleration motion should be symmetrical about time and position.

[0023] However, considering practical realities, to achieve high speed, open-loop AF motors are generally underdamped systems. Given the characteristics of underdamped systems, such as overshoot and periodic vibration, the current should be divided into multiple shaped signals of different amplitudes for motor control. This considers overall control accuracy, algorithm complexity, and configuration flexibility. It should be noted that the current signal I is proportional to the electromagnetic force F = BL * I. When the input current is a shaped signal (or a compensated shaped control signal), the applied electromagnetic force is also a shaped signal. The general conditions to be followed are as follows:

[0024] 1. Average applied electromagnetic force Size:

[0025]

[0026]

[0027] Among them, due to the small damping, the work done by the damping force is The work done by electromagnetic force is negligible. Converted into elastic potential energy:

[0028]

[0029] The final result is the average electromagnetic force. It should be half of the electromagnetic force F at the target location.

[0030] 2. The magnitude and duration of the electromagnetic force applied in each stage.

[0031] Ideally, the acceleration and deceleration algorithms for the motor mover aim to achieve symmetry in the actual motion state about t / 2 in terms of operation time and about x / 2 in terms of position. After applying n segments of shaping signals (or n segments of control signals), the kinematic relationship between the i-th segment and the (n-i+1)-th segment is as follows:

[0032]

[0033] Where X is the position, F is the electromagnetic force corresponding to the final target position X, i = 1, 2, 3…n, where n is an even number greater than or equal to 4. Due to the average electromagnetic force… It should be half of the electromagnetic force F at the target position, and the sum of the electromagnetic force Fi of the i-th segment and the electromagnetic force Fn-i+1 of the (n-i+1)-th segment is F. It can be seen that the magnitude of the electromagnetic force at these two ends is also symmetrical about F / 2.

[0034] In practical engineering, based on theoretical derivation and the actual physical characteristics of voice coil motors, the following constraints are imposed on the first electromagnetic force F1 and the second electromagnetic force F2 when n≥2:

[0035]

[0036] Figure 1 This is a structural block diagram of the driving device 100 for the voice coil motor 200 of the camera in one embodiment of the present invention. Figure 1 The drive device 100 includes a control unit 110 and a drive unit 120.

[0037] The control unit 110 stores n / 2 duration parameters and n / 2 amplitude coefficients. When driving the voice coil motor 200, it calculates n segments of linear control signals based on the target value AT, n / 2 duration parameters, and n / 2 amplitude coefficients from the instructions from the camera. These n segments of linear control signals are connected to form a continuous control signal. After the nth linear control signal, the control signal becomes the target value, where n is an even number greater than or equal to 4. The drive unit 120 outputs a drive signal to drive the voice coil motor 200 based on the control signal output by the control unit 110.

[0038] In one embodiment, when 1 ≤ i ≤ n / 2, the duration Ti of the i-th linear control signal Fi is equal to the i-th duration parameter, the amplitude coefficient of the i-th linear control signal Fi is equal to the i-th amplitude coefficient Ai, and the amplitude of the i-th linear control signal Fi is equal to AT * Ai, where AT equals the target value in the command from the camera. At this time, Ti and Ai are both stored in the control unit 110. When n / 2 < i ≤ n, the duration Ti of the i-th linear control signal Fi is equal to the duration T(n+1-i) of the (n+1-i)-th linear control signal, the amplitude coefficient Ai of the i-th linear control signal Fi is equal to 1 minus the amplitude coefficient A(n+1-i) of the (n+1-i)-th linear control signal, i.e., 1 - A(n+1-i), and the amplitude of the i-th linear control signal Fi is equal to AT * (1 - A(n+1-i)). At t = 2 * (T1 + T2 + ..., Tn / 2), the value of the control signal becomes the target value AT in the command from the camera, where t is time. Preferably, A1∈[0.5, 1], A2∈[0, 0.5], and A1>A2.

[0039] In one embodiment, a set of parameters can be obtained by testing a voice coil motor, the set of parameters including n / 2 duration parameters and n / 2 amplitude coefficients. Preferably, the parameters may differ between different voice coil motors.

[0040] Figure 2 This is a waveform diagram of the first embodiment of the compensated and shaped control signal (or shaping signal) in this invention. In this example, n = 4. Figure 2 In the diagram, the vertical axis ranges from 0 to 1, and the actual amplitude of the control signal is equal to the vertical axis value (amplitude coefficient) multiplied by the target value AT.

[0041] In this embodiment, based on the two conditions 1 and 2 analyzed above, the following duration parameter Ti and amplitude coefficient Ai can be used:

[0042] A1=0.6, A2=0.1, A3=1-A2=0.9, A4=1-A1=0.4, T1=T4=1.6ms, T2=T3=4.3ms, n=4.

[0043] Figure 5 This is an example of the position response curve of the voice coil motor when controlled by the compensated and shaped control signal in the first embodiment; the adjustment time of the voice coil motor after compensation and shaping (±5% error range) is about 11ms, which is a significant reduction in adjustment time.

[0044] Figure 3 This is a waveform diagram of the second embodiment of the compensated and shaped control signal in this invention. In this example, n = 6. In this embodiment, based on the two conditions 1 and 2 analyzed above, the following duration parameter Ti and amplitude coefficient Ai can be used:

[0045] A1=0.6, A2=0.1, A3=0.4, A4=1-A3=0.6, A5=1-A2=0.9, A6=1-A1=0.4. T1=T6=1.5ms, T2=T5=3.5ms, T3=T4=1.0ms.

[0046] Figure 6 This is an example of the position response curve of the voice coil motor when controlled by the compensated and shaped control signal in the second embodiment; the adjustment time of the voice coil motor after compensation and shaping (±5% error range) is about 11.0ms, and the adjustment time has been greatly reduced.

[0047] According to another aspect of the present invention, the present invention provides a method for driving a voice coil motor of a camera, comprising: when driving the voice coil motor, calculating n segments of linear control signals based on a target value, n / 2 duration parameters, and n / 2 amplitude coefficients from an instruction from the camera, the n segments of linear control signals being connected to form a continuous control signal, the control signal becoming the target value after the nth linear control signal, where n is an even number greater than or equal to 4; and outputting a drive signal to drive the voice coil motor based on the control signal output by the control unit.

[0048] In one embodiment, when 1≤i≤n / 2, the duration Ti of the i-th linear control signal Fi is equal to the i-th duration parameter, the amplitude coefficient of the i-th linear control signal Fi is equal to the i-th amplitude coefficient A, and the amplitude of the i-th linear control signal Fi is equal to AT*Ai, where AT is equal to the target value in the instruction from the camera; when n / 2<i≤n, the duration Ti of the i-th linear control signal Fi is equal to the duration T(n+1-i) of the (n+1-i)-th linear control signal, the amplitude coefficient Ai of the i-th linear control signal Fi is equal to 1 minus the amplitude coefficient A(n+1-i) of the (n+1-i)-th linear control signal, i.e., 1-A(n+1-i), and the amplitude of the i-th linear control signal Fi is equal to AT*(1-A(n+1-i)). When t≥2*(T1+T2+……+Tn / 2), the value of the control signal becomes the target value AT in the instruction from the camera, where t is time, A1∈[0.5,1], A2∈[0,0.5], and A1>A2.

[0049] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0050] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications and variations to the above embodiments within the scope of the present invention.

Claims

1. A driving device for a voice coil motor in a camera, characterized in that, It includes: The control unit stores n / 2 duration parameters and n / 2 amplitude coefficients. When driving the voice coil motor, it calculates n segments of linear control signals based on the target value, n / 2 duration parameters, and n / 2 amplitude coefficients from the instructions from the camera. The n segments of linear control signals are connected to form a continuous control signal. After the nth linear control signal, the control signal becomes the target value, where n is an even number greater than or equal to 4. and The drive unit, based on the control signal output by the control unit, outputs a drive signal to drive the voice coil motor. exist i When n / 2, the duration Ti of the i-th linear control signal Fi is equal to the i-th duration parameter, the amplitude coefficient of the i-th linear control signal Fi is equal to the i-th amplitude coefficient Ai, the amplitude of the i-th linear control signal Fi is equal to AT*Ai, and AT is equal to the target value in the instruction from the camera. In n / 2 i When n, the time length Ti of the i-th linear control signal Fi is equal to the time length T(n+1-i) of the (n+1-i)-th linear control signal. The amplitude coefficient Ai of the i-th linear control signal Fi is equal to 1 minus the amplitude coefficient A(n+1-i) of the (n+1-i)-th linear control signal, i.e., 1-A(n+1-i). The amplitude of the i-th linear control signal Fi is equal to AT*(1-A(n+1-i)). A1 [0.5,1],A2 [0,0.5],A1>A2.

2. The driving device according to claim 1, characterized in that, In t When 2*(T1+T2+……+Tn / 2), the value of the control signal becomes the target value AT in the instruction from the camera, where t is time.

3. The driving device according to claim 1, characterized in that, A set of parameters was obtained by testing a voice coil motor, which includes n / 2 duration parameters and n / 2 amplitude coefficients.

4. A method for driving the voice coil motor of a camera, characterized in that, It includes: When driving the voice coil motor, n segments of linear control signals are calculated based on the target value, n / 2 duration parameters, and n / 2 amplitude coefficients from the instructions from the camera. The n segments of linear control signals are connected to form a continuous control signal. After the nth linear control signal, the control signal becomes the target value, where n is an even number greater than or equal to 4. and The voice coil motor is driven by a drive signal output from the control unit. exist i When n / 2, the duration Ti of the i-th linear control signal Fi is equal to the i-th duration parameter, the amplitude coefficient of the i-th linear control signal Fi is equal to the i-th amplitude coefficient Ai, the amplitude of the i-th linear control signal Fi is equal to AT*Ai, and AT is equal to the target value in the instruction from the camera. In n / 2 i When n, the time length Ti of the i-th linear control signal Fi is equal to the time length T(n+1-i) of the (n+1-i)-th linear control signal. The amplitude coefficient Ai of the i-th linear control signal Fi is equal to 1 minus the amplitude coefficient A(n+1-i) of the (n+1-i)-th linear control signal, i.e., 1-A(n+1-i). The amplitude of the i-th linear control signal Fi is equal to AT*(1-A(n+1-i)). A1 [0.5,1],A2 [0,0.5],A1>A2.

5. The driving method according to claim 4, characterized in that, In t When 2*(T1+T2+……+Tn / 2), the value of the control signal becomes the target value AT in the instruction from the camera, where t is time.

6. The driving method according to claim 4, characterized in that, A set of parameters was obtained by testing a voice coil motor, which includes n / 2 duration parameters and n / 2 amplitude coefficients.

Images