JP4067840B2 - Electromagnetic actuator drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drive device for an electromagnetically driven actuator.
[0002]
[Prior art]
A movable portion, a fixed portion, a connecting portion connecting them, a magnetic field generating member fixed to one of the fixed portion and the movable portion, and a drive coil fixed to the other of the fixed portion and the movable portion. An electromagnetically driven actuator is known. This type of electromagnetically driven actuator is driven, for example, by supplying a pulsed current to the drive coil, and the movable part is applied to the fixed part by utilizing the force acting between the drive coil and the magnetic field generating member. And oscillates in a resonance state.
[0003]
Some electromagnetically driven actuators have a swing detection sensor to detect the swing angle and swing angular velocity of the movable part for more accurate control. Some of them do not have such a fluctuation detection sensor.
[0004]
Some drive devices for electromagnetically driven actuators that do not have a swing detection sensor can detect the swing angle and swing angular velocity of the movable part based on the voltage across the drive coil. One conventional example of such a driving device is disclosed in Japanese Patent Application Laid-Open No. 10-209773 entitled “Vibrating Mirror Type Scanning Device Driving Circuit”.
[0005]
In this drive device, an actuator is resonantly driven by applying a pulsed drive signal to a vibrating mirror drive coil (VM coil). Further, this driving device detects the voltage at both ends of the oscillating mirror driving coil by a voltage sampler, and raises a pulsed driving signal at a timing when the detected voltage becomes zero. The pulse width is determined by comparing the peak value of the detection voltage of the voltage sampler with the target voltage.
[0006]
[Problems to be solved by the invention]
In order to drive the electromagnetically driven actuator efficiently, the rising of the pulsed drive current should be matched to the peak of the angular velocity. However, the above-described conventional driving device raises the pulsed driving signal at the timing when the detected voltage of the voltage sampler becomes zero. That is, the rise of the pulsed drive current is matched with the timing at which the angular velocity of the vibrating mirror becomes zero. For this reason, the conventional driving device cannot perform efficient driving.
[0007]
The drive device of the conventional example uses the peak value of the detected voltage as amplitude information. Since the peak value of the detection voltage is easily affected by disturbances such as noise, the validity of the amplitude information is questionable.
[0008]
The drive device of the conventional example adjusts the swing angle amplitude by changing the pulse width of the drive current. For this reason, the distortion of the signal when removing the drive signal superimposed on the detection voltage increases or decreases depending on the pulse width. Therefore, it is difficult for the conventional driving apparatus to accurately detect the amplitude. Further, in order to adjust the swing angle amplitude by changing the pulse width of the drive current, the pulse width must be less than a quarter of the swing period of the actuator. That is, the amplitude adjustment range is limited.
[0009]
The present invention has been made paying attention to these points, and its main object is to provide a drive device for an electromagnetically driven actuator with high drive efficiency.
[0010]
Another object of the present invention is to provide a drive device for an electromagnetically driven actuator capable of accurately adjusting a swing angle amplitude in a wide range.
[0011]
[Means for Solving the Problems]
The present invention provides a movable portion, a fixed portion, a connecting portion that connects the movable portion and the fixed portion, a magnetic field generating member fixed to one of the fixed portion and the movable portion, and the other of the fixed portion and the movable portion. A drive device for driving an electromagnetically driven actuator having a fixed drive coil, The same frequency as the resonance frequency of the moving part A coil driving device for applying a current only for a predetermined period, a voltage detecting device for detecting a voltage at both ends of the driving coil, and a specific time from immediately before the start of current application to the start of current application Start holding, Holds the detection voltage of the voltage detector at least during current application Keep doing Sample-and-hold device and the output of the sample-and-hold device To selectively transmit only the component in the vicinity of the resonance frequency of the movable part, change the phase of this component, binarize, and the phase of the binarized signal, and apply a current from the coil driving device. Within the period Peak swing angular velocity of moving parts Start applying current to include A peak detection device for detecting a specific phase, and the coil driving device starts applying a current in accordance with the detection timing of the specific phase detected by the peak detection device.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
FIG. 1 shows an electromagnetically driven actuator that is driven by the drive device of this embodiment. As shown in FIG. 1, the electromagnetically driven actuator is an electromagnetic optical scanner manufactured using micromachine technology.
[0016]
As shown in FIG. 1, the optical scanner 100 includes an oscillating body 110 having a movable part that can oscillate in one dimension, a magnetic circuit 150 for generating a magnetic field, and a base plate 160 that holds these. Yes.
[0017]
The oscillating body 110 includes a movable portion 112, support portions 114 and 116 for supporting the movable portion 112, and a pair of torsion bars 118 and 120 that are connecting portions connecting the movable portion 112 and the support portions 114 and 116. And have. The pair of torsion bars 118 and 120 support the movable part 112 with respect to the support parts 114 and 116 so as to be swingable around a single axis passing through the torsion bars 118 and 120.
[0018]
The movable portion 112 has a flat plate shape, and has a substantially parallel front surface (surface visible in FIG. 1) and back surface (surface not visible in FIG. 1). The movable part 112 has, for example, a mirror formed on its front surface. Alternatively, the front surface of the movable portion 112 may function as a reflecting surface.
[0019]
The movable part 112 has a drive coil 132 formed on its back surface. The drive coil 132 goes around the periphery of the movable part 112. Both ends of the drive coil 132 are connected to a pair of electrode pads 138 and 140 provided on the support portion 114 via wires passing through the torsion bar 118, respectively.
[0020]
The magnetic circuit 150 includes a pair of permanent magnets 152 and 154 that are magnetic field generating members, and a yoke 156 that holds them.
[0021]
The oscillating body 110 is attached to the base plate 160 by fixing the support portions 114 and 116 to the base plate 160. The magnetic circuit 150 is attached to the base plate 160 by fixing the yoke 156 to the base plate 160. In this structure, a portion excluding the movable portion 112, the torsion bars 118 and 120, and the permanent magnets 152 and 154 constitutes a fixed portion.
[0022]
A light beam is applied to a mirror on the front surface of the movable portion 112 (or a front surface that functions as a reflecting surface), and the reflected light beam is scanned one-dimensionally according to the swing of the movable portion 112. .
[0023]
An alternating current drive signal is applied to the electrode pads 138 and 140 via a flexible printed circuit board (FPC) 142. In response to this, a current flows through the drive coil 132. The current flowing through the drive coil 132 receives a Lorentz force depending on its magnitude due to the interaction with the magnetic field component.
[0024]
A pair of opposite side portions parallel to the swing axis of the drive coil 132 receive a force in a direction substantially perpendicular to the surface (front surface or back surface) of the movable portion 112 due to the Lorentz force received by the current flowing therethrough. Further, since the currents flowing through the pair of opposite sides are opposite to each other, the movable portion 112 receives a couple of forces around the swing axis. For this reason, the movable part 112 rotates around the swing axis according to the magnitude of the current flowing through the drive coil 132.
[0025]
Since the drive signal applied to the electrode pads 138 and 140 is an alternating current, the current flowing through the drive coil 132 is an alternating current. Since the direction of the current is alternately switched, the direction of the couple received by the movable portion 112 is alternately switched, and the rotation direction of the movable portion 112 is also alternately switched accordingly. Therefore, the movable portion 112 repeatedly rotates (that is, swings) around the swing axis in both directions within a certain angle range. As a result, the light beam reflected by the movable portion 112 is scanned one-dimensionally.
[0026]
The movable portion 112 has a specific resonance frequency determined by the structure and material of the torsion bars 118 and 120, and vibrates at the maximum deflection angle when the frequency of the drive signal matches this resonance frequency.
[0027]
FIG. 2 shows the frequency characteristics of the driving frequency and the deflection angle when the optical scanner 100 is driven with a sine wave. The behavior of the optical scanner 100 will be described in three regions A, B, and C according to the frequency of the drive signal.
[0028]
Region A is a frequency band sufficiently lower than the resonance frequency fr. In this region, the swing angle of the movable portion 112 does not depend on the frequency, and there is no phase difference between the drive signal and the swing angle. That is, the behavior of the optical scanner 100 basically follows the drive signal.
[0029]
A region B is a frequency band near the resonance frequency fr. In this region, an increase in deflection angle and a phase delay occur, and the behavior of the optical scanner 100 does not necessarily follow the drive signal. The deflection angle is affected by the frequency and the attenuation rate.
[0030]
The region C is a frequency band sufficiently high with respect to the resonance frequency fr, and basically the influence of the torsion bars 118 and 120 can be ignored in this region. That is, if the driving force is constant, the response is made so that the angular acceleration of the movable portion 112 is constant.
[0031]
In summary, the swing angle of the movable portion 112 is constant regardless of the frequency of the drive signal in the low frequency region, the gain of the swing angle is very high at the resonance frequency, and the swing angle of the movable portion 112 is high in the high frequency region. Decreases rapidly with increasing frequency (since it responds to constant angular acceleration).
[0032]
At the resonance frequency of the region B, the phase of the deflection angle is delayed by 90 degrees with respect to the drive signal. When the frequency of the drive signal increases or decreases with respect to the resonance frequency, the phase relationship between the drive signal and the swing angle increases or decreases around 90 degrees, and the swing angle decreases with respect to the resonance time.
[0033]
Considering the relationship between the drive signal and the shake angular velocity based on this, the shake angular velocity is a differential value of the shake angle, and as shown in FIG. 3, the phase of the shake angular velocity is 90 degrees ahead of the shake angle. Therefore, the drive signal and the shake angular velocity have the same phase at the resonance frequency. FIG. 4 shows the frequency characteristics of the shake angular velocity with respect to the drive frequency.
[0034]
Although the case where the drive signal is a sine wave has been described above, the same concept can be applied to a case of a rectangular pulse-like drive signal. That is, for example, the rectangular pulse-shaped drive signal shown in FIG. 5A has the sine wave shown in FIG. It is represented by a superposition of sine waves having frequency components of double. In other words, the rectangular pulsed drive signal is represented by superposition of an odd multiple of the fundamental frequency component by Fourier series expansion.
[0035]
The response of the optical scanner to this signal is large when the fundamental frequency matches the resonance frequency of the optical scanner. The frequency component is large, 3 times, 5 times, 7 times, etc., that is, other odd numbers. Since the response to the double frequency component belongs to the region C in FIG. 2, it can be ignored for the response deflection angle of the resonance frequency.
[0036]
For this reason, the deflection angle and the deflection angular velocity are both sine waves as shown in FIGS. 5C and 5D, respectively. The deflection angle and the deflection angular velocity are 90 degrees out of phase, and the peak of the deflection angular velocity is synchronized with the pulse of the drive current signal.
[0037]
As described above, when driven at the resonance frequency, the response of the optical scanner becomes a substantially sinusoidal response even if the drive waveform is a rectangular pulse.
[0038]
The same applies to the pulse-shaped drive signal having both polarities shown in FIG. 6A, and the sine wave of the fundamental frequency is as shown in FIG. 6B. Are as shown in FIG. 6C and FIG. 6D, respectively.
[0039]
FIG. 7 shows the configuration of the driving apparatus of this embodiment for driving the optical scanner 100. As shown in FIG. 7, the driving device 200 includes a coil driving device 210 for applying a driving current to the driving coil 132, a voltage detecting device 220 for detecting the voltage at both ends of the driving coil 132, and voltage detection. A sample and hold device 230 for holding the detection voltage of the device 220 and a peak detection device 240 for detecting a substantial peak of the swing angular velocity of the movable portion 112 are provided.
[0040]
The coil drive device 210 applies a constant current to the drive coil 132 only for a predetermined period. That is, the coil driving device 210 supplies a pulsed current to the driving coil 132. Of course, the predetermined period, that is, the pulse width is shorter than 1 / (2fr) [second] (fr: drive frequency [Hz]). The coil driving device 210 preferably supplies a pulsed current having a frequency equal to the resonance frequency fr of the optical scanner 100.
[0041]
The sample and hold device 230 starts holding at a specific time from immediately before the start of current application to the start of current application, and continues to hold at least during the current application. The sample and hold device 230 preferably releases the hold after the end of current application. That is, the sample and hold device 230 releases the hold after a predetermined time has elapsed after the current application is completed.
[0042]
The hold period is set longer than the current application period for the following reason. Since the bandwidth of the circuit used in the voltage detection device 220 or the like is limited, the pulse width of the drive signal that appears at the output of the voltage detection device 220 is usually wider than the pulse width of the drive current. In order to completely remove the drive signal appearing at the output of the voltage detector 220, the hold period may be set longer than the current application period, that is, the pulse width of the drive signal.
[0043]
The peak detection device 240 detects a specific phase near the peak of the swing angular velocity of the movable unit 112 based on the output of the sample and hold device 230. More specifically, the peak detection device 240 includes the oscillation period T [seconds] of the optical scanner 100 (which is equal to the reciprocal of the resonance frequency fr of the optical scanner 100) and the pulse width d [seconds] of the output of the coil driving device. ], A phase represented by the following equation (1) is detected using a real number k satisfying 0 ≦ k ≦ 1.
[0044]
90-k · d · 360 / T [degree] (1)
The peak detection device 240 outputs a peak detection signal indicating the detection of a specific phase to the coil driving device 210. The coil drive device 210 applies a current to the drive coil 132 in accordance with the input peak detection signal. More specifically, the coil drive device 210 supplies the drive coil 132 with a pulsed current that rises at the detection timing of a specific phase detected by the peak detection device 240.
[0045]
The drive current supplied to the drive coil 132 has the earliest phase when k = 1 in equation (1), the pulse drops at the peak of the angular velocity, and the phase when k = 0 in equation (1). Slow, the pulse rises at the peak angular velocity. In other words, the drive current overlaps the peak of the swing angular velocity of the pulse.
[0046]
Specifically, for example, as shown in FIG. 8, the peak detection device 240 is a band-pass filter circuit that selectively transmits only components near the resonance frequency of the optical scanner 100 in the output signal of the sample and hold device 230. 24, a phase change device 244 that changes the phase of the output signal of the bandpass filter circuit 242, and a comparison device 246 that compares the output signal of the phase change device 244 with a specific level.
[0047]
Returning to FIG. 7 again, the driving device 200 further includes an amplitude detection device 250 that detects the swing angle amplitude of the movable portion 112 based on the output signal of the sample and hold device 230, and an error in the swing angle amplitude of the movable portion 112 ( That is, an amplitude error detection device 260 that detects a deviation from the target value is provided.
[0048]
The amplitude error detection device 260 compares the output signal of the amplitude detection device 250 input thereto and the target amplitude signal, and causes the drive coil 132 to match the actual deflection angle amplitude of the movable portion 112 with the target value. A current control signal indicating the current to be supplied is output to the coil driving device 210.
[0049]
The coil drive device 210 changes the amplitude of the pulsed current supplied to the drive coil 132 based on the current control signal input from the amplitude error detection device 260. The coil driving device 210 preferably changes only the amplitude of the current without changing the current application time, that is, the pulse width.
[0050]
For example, the amplitude detector 250 outputs a signal corresponding to the area of one cycle of the AC waveform of the output signal of the sample and hold device 230. Alternatively, the amplitude detection device 250 outputs a signal corresponding to an area corresponding to a half cycle of the AC waveform of the output signal of the sample and hold device 230.
[0051]
Therefore, for example, as shown in FIG. 9, the amplitude detection device 250 smoothes the absolute value signal of the output of the sample and hold device 230 and the output of the rectification circuit 252 by smoothing the absolute value signal. And a low-pass filter 254 for outputting a signal corresponding to the average value.
[0052]
The cut-off frequency of the low-pass filter 254 is preferably selected to be sufficiently lower than the resonance frequency of the optical scanner 100 so that no ripple occurs in the output.
[0053]
The rectifier circuit 252 is composed of a full-wave rectifier circuit for the output of a signal corresponding to the area of one cycle of the output signal of the sample and hold device 230, and is equivalent to a half cycle of the output signal of the sample and hold device 230. For the output of the signal corresponding to the area, it is constituted by a half-wave rectifier circuit.
[0054]
First drive example
In the first driving example, the peak detection device 240 determines the peak of the angular velocity of the movable portion 112 based on the output of the sample and hold device 230, in other words, the phase of 90 degrees of the waveform of the angular velocity of the movable portion 112. The detection is performed, and the coil drive device 210 applies the current to the drive coil 132 in accordance with the rise of the pulsed drive current at the timing. This corresponds to the case of k = 0 in the above-described equation (1).
[0055]
Hereinafter, the operation of the driving device in such driving will be described.
[0056]
In the following description, it is assumed that the peak detection device 240 has correctly detected the peak of the swing angular velocity of the swing of the movable part 112 caused by the pulse-like current application to the drive coil 132 immediately before.
[0057]
The peak detection device 240 outputs a peak detection signal that informs detection of a peak of the shake angular velocity. Specifically, the output of the peak detector 240, that is, the peak detection signal, as will be described later, is a rectangular pulse waveform that rises in synchronization with the peak of the deflection angular velocity, as shown in FIG.
[0058]
The coil driving device 210 starts applying a constant current to the driving coil 132 in response to the rising edge of the peak detection signal. Thereafter, the coil driving device 210 stops applying a constant current to the driving coil 132 after a predetermined time has elapsed. As a result, as shown in FIG. 10A, the coil driving device 210 drives a current having a rectangular pulse waveform that has a frequency equal to the resonance frequency of the optical scanner 100 and rises at a timing that coincides with the peak of the angular velocity. The coil 132 is supplied.
[0059]
As described above, the movable portion 112 of the optical scanner 100 swings due to the Lorentz force generated between the drive coil 132 and the magnetic circuit 150 in response to the current application to the drive coil 132. Back electromotive force is generated in the drive coil 132 due to the swinging of the movable portion 112. This counter electromotive force is proportional to the deflection angular velocity of the movable portion 112.
[0060]
The voltage detection device 220 detects the voltage across the drive coil 132 of the optical scanner 100. When the optical scanner 100 is driven at the resonance frequency, as described above with reference to FIG. 5, the phase of the waveform of the deflection angular velocity matches the phase of the waveform of the fundamental frequency component of the drive current. Therefore, as shown in FIG. 10B, the output of the voltage detection device 220 is a waveform in which the pulse waveform of the drive current is superimposed on the sine waveform of the angular velocity.
[0061]
The sample and hold device 230 holds the output of the voltage detection device 220 in response to the rising edge of the peak detection signal. Thereafter, the sample and hold device 230 releases the hold after the end of the current application. As a result, as shown in FIG. 10C, the sample and hold device 230 outputs a signal obtained by removing the pulse-like waveform caused by the drive current from the output signal of the voltage detection device 220. In the output waveform of the sample and hold device 230, the fundamental frequency matches the frequency of the deflection angle, and the average absolute value is proportional to the amplitude of the deflection angle.
[0062]
The peak detector 240 detects the peak of the swing angular velocity of the movable part 112, that is, the phase of 90 degrees. As described above, the peak detection device 240 includes the band-pass filter circuit 242, the phase change device 244, and the comparison device 246, as shown in FIG.
[0063]
In order to detect the phase of 90 degrees of the swing angular velocity of the movable part 112, for example, the phase change device 244 has the phase of the output signal from itself being −90 ° with respect to the phase of the output signal of the voltage detection device 220 As described above, the phase of the output signal of the bandpass filter circuit 242 is changed. In other words, at the resonance frequency of the optical scanner 100, the total phase change by the voltage detection device 220, the sample and hold device 230, the bandpass filter circuit 242, and the phase change device 244 is equal to -90 degrees.
[0064]
Further, the comparison device 246 compares the output of the phase change device 244 with 0 potential and outputs a binary signal indicating the comparison result. As a result, as shown in FIG. 10D, the output of the peak detector 240 becomes a rectangular pulse waveform that rises in synchronization with the peak of the deflection angular velocity.
[0065]
As shown in FIG. 10A, the coil driving device 210 supplies a current of a rectangular pulse waveform that rises in synchronization with the rising of the peak detection signal to the driving coil 132.
[0066]
In the first driving example, the driving device 200 according to the present embodiment supplies the driving coil 132 with a driving current signal having a pulse waveform that rises in synchronization with the peak of the angular velocity of vibration, so that the optical scanner 100 can be efficiently operated. Can be driven.
[0067]
As described above, the amplitude detection device 250 includes the rectifier circuit 252 and the low-pass filter 254. For example, as illustrated in FIG. 11, the amplitude detection device 250 corresponds to one cycle of the AC waveform of the output signal of the sample and hold device 230. A signal corresponding to the area is output. Here, the area of one cycle of the AC waveform is an area surrounded by the central axis of the amplitude and the waveform of the phase from 0 degrees to 360 degrees.
[0068]
The area for one cycle of the AC waveform represents the average value of the absolute value signals for one cycle of the AC waveform. In FIG. 11, the area of the hatched portion is proportional to the amplitude of the shake angular velocity, and the amplitude of the shake angular velocity is proportional to the amplitude of the shake angle. Therefore, the average value of the absolute value signal output from the amplitude detector 250 is proportional to the amplitude of the swing angle of the movable portion 112.
[0069]
The amplitude error detection device 260 compares the output signal of the amplitude detection device 250 with the target amplitude signal, and a constant current to be applied to the drive coil 132 in order to make the deflection angle amplitude of the movable portion 112 coincide with the target value. The value, that is, the amplitude of the pulsed current waveform is obtained, and a current control signal indicating the value is output to the coil driving device 210.
[0070]
The coil driving device 210 changes only the current value of a constant current applied to the driving coil 132, that is, the amplitude of the pulsed current waveform, according to the current control signal. That is, the coil driving device 210 changes the current value of the constant current, that is, the amplitude of the pulsed current waveform, while keeping the current application time, that is, the pulse width constant. Thereby, the swing angle amplitude of the movable part 112 is adjusted.
[0071]
FIG. 11 shows one cycle of the AC waveform of the output signal of the sample and hold device 230 for two types of pulsed drive current waveforms having different amplitudes. As can be seen from FIG. 11, the waveform, that is, the shape of the shaded portion, does not change in the horizontal direction and changes only in the vertical direction when the amplitude of the pulsed current waveform is changed. That is, the hatched portion is independently enlarged or reduced only in the vertical direction by changing the amplitude of the pulse-like current waveform. Therefore, the area for one period, that is, the area of the shaded area is proportional to the amplitude of the pulsed current waveform.
[0072]
Thus, since the drive device 200 of this embodiment adjusts the swing angle amplitude of the movable part 112 by changing the amplitude of the drive current signal, the amplitude adjustment range is not substantially limited.
[0073]
In the above description, the driving by the pulsed current having the waveform having only one polarity shown in FIG. 10A has been described. However, the same applies to the pulsed current having the waveform having both polarities shown in FIG. Can be driven.
[0074]
In this case, with respect to the supply of the current having the rectangular pulse waveform of the bipolar polarity shown in FIG. 12A to the drive coil 132, the voltage detection device 220 uses the sine waveform of the deflection angular velocity shown in FIG. Is output with the pulse waveform of the drive current superimposed thereon, and the sample and hold device 230 removes the pulse-like waveform caused by the drive current from the output signal of the voltage detection device 220 shown in FIG. The waveform is output, and the peak detector 240 outputs a rectangular pulse waveform that rises in synchronization with the peak of the deflection angular velocity shown in FIG.
[0075]
The coil drive device 210 outputs a pulse on the positive side of the drive waveform in synchronization with the rise of the output waveform of the peak detection device 240. For example, the rise of the signal waveform obtained by changing the phase of the output waveform of the peak detection device 240 by 180 degrees. Synchronously with this, a negative pulse of the drive waveform is output. Alternatively, the peak detection device 240 may further detect the minimum (bottom) of the angular velocity, and the coil driving device 210 may output a negative pulse of the driving waveform in synchronization with the rise of the output waveform.
[0076]
Further, the waveform of the current applied from the coil driving device to the coil may be a waveform obtained by cutting a sine waveform or the like with a driving pulse width instead of a rectangular pulse waveform. In this case, components other than the resonance frequency included in the drive signal can be reduced.
[0077]
In the above description, the phase change amount of the phase change device of the peak detection device is set to −90 degrees. However, even in the configuration in which the phase change amount of the phase change device is set to 90 degrees, the deflection angular velocity of 90−d · 180 / Driving can be performed in synchronization with the phase of T degrees. In this case, the drive pulse is output in synchronization with the fall of the output of the comparison device.
[0078]
Second drive example
The second driving example is a driving in which the center of the pulse of the driving current coincides with the peak of the swing angular velocity of the movable portion 112. More specifically, the peak detection device 240 detects the 90-d · 180 / T phase of the waveform of the swing angular velocity of the movable portion 112 based on the output of the sample and hold device 230, and the coil driving device 210 In this drive, a pulsed drive current that rises at that timing is supplied to the drive coil 132. This corresponds to the case of k = 1/2 in the above-described equation (1).
[0079]
Hereinafter, the operation of the driving device in such driving will be described.
[0080]
The coil driving device 210 starts applying a constant current to the driving coil 132 in response to the rising edge of the peak detection signal shown in FIG. Thereafter, the coil driving device 210 stops applying a constant current to the driving coil 132 after a predetermined time has elapsed. As a result, as shown in FIG. 13A, the coil driving device 210 generates a rectangular pulse waveform current that has a frequency equal to the resonance frequency of the optical scanner 100 and rises before the peak of the deflection angular velocity. To supply. The supply of pulsed current to the drive coil 132 causes the movable part 112 of the optical scanner 100 to swing. The swing of the movable portion 112 causes the drive coil 132 to generate a counter electromotive force depending on the swing angular velocity.
[0081]
The voltage detection device 220 detects the voltage across the drive coil 132 of the optical scanner 100. As shown in FIG. 13B, the output of the voltage detection device 220 has a waveform in which the pulse waveform of the drive current is superimposed on the sine waveform of the deflection angular velocity. More specifically, as shown in FIG. 14, the output of the voltage detection device 220 is a waveform in which a pulse having a time width d rising at T / 4−d / 2 is superimposed on a sine waveform of a swing angular velocity with a period T. is there. The center of the pulse coincides with the peak of the swing angular velocity of the movable portion 112. The rise of the pulse is 90-d · 180 / T degrees in terms of phase.
[0082]
The sample and hold device 230 holds the output of the voltage detection device 220 in response to the rising edge of the peak detection signal. Thereafter, the sample and hold device 230 releases the hold after the end of the current application. As a result, as shown in FIG. 13C, the output of the sample and hold device 230 becomes a waveform obtained by removing the pulse-like waveform caused by the drive current from the output signal of the voltage detection device 220.
[0083]
The peak detector 240 detects a phase of 90-d · 180 / T degrees of the swing angular velocity of the movable part 112. For this reason, the phase change device 244 has a band-pass filter circuit so that the phase of the output signal from itself is − (90−d · 180 / T) degrees with respect to the phase of the output signal of the voltage detection device 220. The phase of the output signal 242 is changed. Further, the comparison device 246 compares the output of the phase change device 244 with 0 potential and outputs a binary signal indicating the comparison result. As a result, as shown in FIG. 13D, the output of the peak detector 240 becomes a rectangular pulse waveform that rises in synchronization with the phase of the swing angular velocity of 90-d · 180 / T degrees.
[0084]
As shown in FIG. 13A, the coil driving device 210 supplies a current of a rectangular pulse waveform that rises in synchronization with the rising of the peak detection signal to the driving coil 132.
[0085]
In the second driving example, the driving device 200 according to the present embodiment supplies the driving coil 132 with a driving current signal having a pulse waveform in which the center of the time width coincides with the peak of the deflection angular velocity. 100 can be driven more efficiently.
[0086]
Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to these embodiments, and various modifications and changes can be made without departing from the scope of the present invention. May be.
[0087]
For example, the waveform of the current applied from the coil drive device to the coil may be a waveform obtained by cutting a sine wave or the like with the drive pulse width instead of the rectangular pulse waveform. In this case, components other than the resonance frequency included in the drive signal can be reduced.
[0088]
In the above description, the phase change amount of the phase change device of the peak detection device is − (90−d · 180 / T) degrees, but the phase change amount of the phase change device is (90 + d · 180 / T) degrees. Even in this configuration, driving can be performed in synchronization with the phase of the angular velocity of 90-d · 180 / T degrees. In this case, the drive pulse is output in synchronization with the fall of the output of the comparison device.
[0089]
In the above description, the amplitude detection device 250 obtains the swing angle amplitude of the movable unit 112 based on the output of the sample and hold device 230. However, the amplitude detection device 250 of the bandpass filter circuit 242 in the peak detection device 240 has You may obtain | require based on an output.
[0090]
Further, the peak detection device 240 detects the phase of the swing angular velocity of the movable portion 112 at 90 degrees, so that in the phase change device 244, the phase of the output signal is − with respect to the phase of the output signal of the voltage detection device 220 The phase of the output signal of the bandpass filter circuit 242 is changed so as to be (90−k · d · 360 / T) degrees, and the comparator 246 compares the output of the phase change device 244 with 0 potential. However, the phase amount to be changed and the potential to be compared are not limited to these values, and may be changed as appropriate.
[0091]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the drive device of an electromagnetic drive type actuator with sufficient drive efficiency is provided. In addition, a drive device for an electromagnetically driven actuator capable of accurately adjusting the deflection angle amplitude in a wide range is provided.
[Brief description of the drawings]
FIG. 1 shows an electromagnetically driven actuator that is driven by a drive device of the present embodiment.
FIG. 2 shows a frequency characteristic of a driving frequency and a deflection angle when the electromagnetically driven actuator of FIG. 1, that is, the optical scanner is driven with a sine wave.
3 shows a deflection angle and a deflection angular velocity when the optical scanner of FIG. 1 is driven by a sine wave. FIG.
4 shows frequency characteristics of a shake angular velocity with respect to a driving frequency when the optical scanner of FIG. 1 is driven by a sine wave. FIG.
5 shows a drive current signal, a sine wave of a fundamental frequency component, a shake angle, and a shake angular velocity when the optical scanner of FIG. 1 is driven by a unipolar rectangular wave.
6 shows a drive current signal, a sine wave of a fundamental frequency component, a shake angle, and a shake angular velocity when the optical scanner of FIG. 1 is driven by a bipolar rectangular wave.
7 shows a configuration of an embodiment of a driving device of the present invention for driving the optical scanner of FIG. 1. FIG.
8 shows the configuration of the peak detection apparatus shown in FIG.
FIG. 9 shows a configuration of the amplitude detection apparatus shown in FIG. 7;
10 shows the output (driving) of the coil driving device of the driving device of FIG. 7 when the optical scanner of FIG. 1 is driven by a unipolar rectangular wave according to the first driving example (phase detection of 90 degrees of the shake angular velocity waveform). Waveform), the output of the voltage detector, the output of the sample and hold device, and the output of the peak detector.
FIG. 11 shows one cycle of the AC waveform of the output signal of the sample and hold device for two types of pulsed drive current waveforms with different amplitudes.
12 shows the output (driving waveform) of the coil driving device, the output of the voltage detection device, the output of the voltage detector when the optical scanner of FIG. 1 is driven by a bipolar rectangular wave according to the first driving example, It shows the output of the hold device and the output of the peak detector.
13 shows a coil of the driving device shown in FIG. 7 when the optical scanner shown in FIG. 1 is driven with a unipolar rectangular wave in accordance with a second driving example (phase detection of 90-d · 180 / T degrees of the shake angular velocity waveform). The output (drive waveform) of the drive device, the output of the voltage detection device, the output of the sample and hold device, and the output of the peak detection device are shown.
14 shows an enlarged output of the voltage detection device shown in FIG.
[Explanation of symbols]
200 Drive unit
210 Coil driving device
220 Voltage detection device
230 Sample and hold device
240 Peak detector
242 Bandpass filter circuit
244 Phase change device
246 Comparison device
250 Amplitude detector
252 Rectifier circuit
254 Low-pass filter
260 Amplitude error detection device

Claims (21)

A movable portion, a fixed portion, a connecting portion connecting the movable portion and the fixed portion, a magnetic field generating member fixed to one of the fixed portion and the movable portion, and a drive fixed to the other of the fixed portion and the movable portion A driving device for driving an electromagnetically driven actuator having a coil, and supplying a pulsed current having the same frequency as the resonance frequency of the movable part to the driving coil, A driving device that swings the movable part in a resonance state with respect to the fixed part using a force acting between
A coil driving device for applying a current to the driving coil for a predetermined period;
A voltage detection device for detecting the voltage across the drive coil;
A sample-and-hold device that starts holding at a specific time from immediately before the start of current application to the start of current application, and continues to hold the detection voltage of the voltage detection device at least during the current application;
Only the component near the resonance frequency of the movable part is selectively transmitted from the output of the sample-and-hold device, the phase of this component is changed, binarized, and the phase of this binarized signal, which is a coil driving device A peak detection device for detecting a specific phase for starting the application of current so that the peak of the swing angular velocity of the movable part is included within a predetermined period of applying the current from
The coil drive device is a drive device for an electromagnetically driven actuator that starts applying current in accordance with the detection timing of a specific phase detected by the peak detection device.   2. The drive device for an electromagnetically driven actuator according to claim 1, wherein the coil drive device applies a constant current to the drive coil for a predetermined period.   2. The peak detection device according to claim 1, wherein the peak angular velocity of the movable portion is 90−k · d · 360 / T degrees (where T is a period [second] corresponding to the reciprocal of the resonance frequency of the actuator, and d is a coil drive). A drive device for an electromagnetically driven actuator that detects a phase of a pulse width [second] of an output of the device, k being a real number satisfying 0 ≦ k ≦ 1.   4. The drive device for an electromagnetically driven actuator according to claim 3, wherein the peak detection device detects a phase of 90 degrees of the swing angular velocity of the movable part.   4. The drive device for an electromagnetically driven actuator according to claim 3, wherein the peak detection device detects a phase of 90-d · 180 / T degrees of the swing angular velocity of the movable part.   The peak detection device of the deflection angular velocity according to claim 1, wherein the output signal of the sample and hold device selectively transmits only a component near the resonance frequency of the actuator, and the output signal of the bandpass filter circuit. A drive device for an electromagnetically driven actuator, comprising: a phase change device that changes a phase; and a comparison device that compares an output signal of the phase change device with a specific level.   7. The phase change device according to claim 6, wherein the phase of the output signal from the bandpass filter circuit is such that the phase of the output signal from itself is +90 degrees or −90 degrees with respect to the phase of the output signal of the voltage detection device. The drive device of the electromagnetic drive actuator that changes   6. The phase change device according to claim 6, wherein the phase of the output signal from itself is +90 (T + 2d) / T degrees or −90 (T−2d) / T degrees (here, The phase of the output signal of the band-pass filter circuit is changed so that T is a period [second] corresponding to the reciprocal of the resonance frequency of the actuator, and d is a pulse width [second] of the output of the coil drive device). A drive device for an electromagnetically driven actuator.   2. The drive device for an electromagnetically driven actuator according to claim 1, wherein the sample and hold device releases the hold after the end of current application of the coil drive device.   2. The amplitude detection device for detecting a swing angle amplitude of the movable portion based on an output signal of the sample and hold device, and an amplitude error detection device for detecting an error of the swing angle amplitude of the movable portion with respect to a target value. A drive device for an electromagnetically driven actuator, the coil drive device changing the amplitude of a pulsed current supplied to the drive coil based on an output signal of the amplitude error detection device.   11. The drive device for an electromagnetic drive actuator according to claim 10, wherein the coil drive device changes only the amplitude of the current without changing the current application time.   11. The drive device for an electromagnetically driven actuator according to claim 10, wherein the amplitude detection device outputs a signal corresponding to the area of one cycle of the AC waveform of the output signal of the sample and hold device.   13. The drive device for an electromagnetic drive actuator according to claim 12, wherein the amplitude detection device includes a full-wave rectifier circuit and a low-pass filter.   11. The drive device for an electromagnetically driven actuator according to claim 10, wherein the amplitude detection device outputs a signal corresponding to an area corresponding to a half cycle of the AC waveform of the output signal of the sample and hold device.   15. The drive device for an electromagnetically driven actuator according to claim 14, wherein the amplitude detection device includes a half-wave rectifier circuit and a low-pass filter.   7. An amplitude detection device for detecting a swing angle amplitude of a movable portion based on an output signal of a sample and hold device or an output signal of a bandpass filter circuit, and detecting an error with respect to a target value of the swing angle amplitude of the movable portion. And an amplitude error detection device that changes the amplitude of the pulsed current supplied to the drive coil based on the output signal of the amplitude error detection device.   17. The electromagnetic drive actuator drive device according to claim 16, wherein the coil drive device changes only the current amplitude without changing the current application time.   17. The drive device for an electromagnetically driven actuator according to claim 16, wherein the amplitude detection device outputs a signal corresponding to an area of one cycle of an AC waveform of the output signal of the sample and hold device or the output signal of the bandpass filter circuit.   19. The drive device for an electromagnetic drive actuator according to claim 18, wherein the amplitude detection device includes a full-wave rectifier circuit and a low-pass filter.   17. The drive device for an electromagnetically driven actuator according to claim 16, wherein the amplitude detection device outputs a signal corresponding to an area corresponding to a half cycle of the AC waveform of the output signal of the sample and hold device or the output signal of the bandpass filter circuit.   21. The drive device for an electromagnetically driven actuator according to claim 20, wherein the amplitude detection device includes a half-wave rectifier circuit and a low-pass filter.

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