JP3435890B2 - Movable object position control device, variable optical axis prism device, and imaging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for application to a variable optical axis prism device mounted on an image pickup device such as a motor controller, especially a camera-integrated video tape recorder (hereinafter referred to as "camcorder"). It is about.

[0002]

2. Description of the Related Art As a camera shake correction device used in a camcorder, there is one called a variable optical axis prism. The variable optical axis prism, as shown in FIG.
The space formed by the pitch glass plate a, the yaw glass plate b, and the bellows c is filled with a special liquid d.

FIG. 6 is a diagram showing the principle of camera shake correction of a variable optical axis prism. When there is no camera shake as shown in (1) of this figure, the variable optical axis prism passes through the lens and C
The optical axis reaching the image pickup surface of the CD imager passes through the center of each element. On the other hand, at the time of camera shake correction as shown in (2) and (3) of this figure, the pitch glass plate and the yaw glass plate are rotated in accordance with the camera shake (only the pitch glass plate is shown in this figure). By rotating), the optical axis of the variable optical axis prism is changed according to camera shake, and the optical axis is moved from the position of the broken line to the position of the alternate long and short dash line. As a result, an image of the subject whose camera shake is corrected is formed on the imaging surface.

Conventionally, as a camera shake correction device using such a variable optical axis prism, there is one shown in FIG. The camera shake correction device shown in this figure includes an angular velocity sensor including a pitch sensor 41 and a yaw sensor 42 as an element for detecting camera shake of a camcorder. The pitch sensor 41 and the yaw sensor 42 are connected to the arithmetic processing circuit 43. The arithmetic processing circuit 43 generates a control signal for correcting camera shake based on the outputs of the pitch sensor 41 and the yaw sensor 42, and the actuator 44,
Supply to 45. The actuator 44 rotates the pitch glass plate 46a of the variable optical axis prism 46 around the pitch rotation center 46e according to the control signal, and the actuator 45 rotates the pitch glass plate 46a of the variable optical axis prism 46 according to the control signal. 46b is rotated around the yaw rotation center 46f. In this way, by changing the optical axis of the variable optical axis prism 46 according to the camera shake, the camera shake of the camcorder is corrected.

Next, the process of generating a control signal for correcting camera shake in the arithmetic processing circuit 43 will be described. As is clear from FIG. 7, this processing is performed in parallel with respect to pitching and yawing, and therefore, pitching correction will be described here.

The arithmetic processing circuit 43 is an A / D converter 51 for converting the output of the pitch sensor 41 into a digital value.
A digital integration circuit 53 that integrates the output of the A / D converter 51, a D / A converter 55 that converts the output of the digital integration circuit 53 into an analog value, and a rotational position sensor that will be described later based on the output of the D / A converter 55. An adder 57 for subtracting the output of 47 and an adder 59 for subtracting the output of a speed detection coil 49 described later from the output of the adder 57.
It has and. The rotational position sensor 47 detects the rotational position of the actuator 44. Also, the speed detection coil 4
Reference numeral 9 detects the rotation speed of the actuator 44.

The arithmetic processing circuit 43 operates as follows. The angular velocity detected by the pitch sensor 41 is converted into a digital value by the A / D converter 51 and integrated by the digital integration circuit 53. This integrated value is the target rotational position of the actuator 44. The actual rotational position of the actuator 44 is subtracted from the target rotational position by the adder 57, and the rotational speed of the actuator 44 is further subtracted by the adder 59. The reason for subtracting the rotation speed in the adder 59 is to increase the phase margin of the servo system by feeding back the speed.

FIG. 8 is a diagram showing a structure of a portion for driving the above-mentioned actuator. Although this circuit configuration is common to the actuators 44 and 45, it will be described as a circuit for driving the actuator 44 for convenience. Also, since the actuator is composed of a motor,
Hereinafter, this part will be referred to as a motor control device.

In FIG. 8, a signal corresponding to the target rotational position (hereinafter referred to as "reference signal") is input to the reference signal input terminal 1 from the D / A converter 55 in FIG. A resistor Rr that determines the gain of the reference signal is connected between the reference signal input terminal 1 and the inverting input terminal of the comparison circuit operational amplifier 2. Further, between the inverting input terminal and the output terminal of the operational amplifier 2 for comparison circuit, a resistor Rθ that determines the gain of this operational amplifier is connected. Further, a resistor Rp that determines the gain of the rotational position signal generated by the rotational position sensor 6 is connected to the inverting input terminal of the comparison circuit operational amplifier 2. The rotational position sensor 6 corresponds to the rotational position sensor 47 of FIG. 7, and detects the rotational position of the rotor 11 of the motor 5 that constitutes the actuator 44. That is, the operational amplifier 2 for the comparison circuit is the adder 5 of FIG.
Equivalent to 7.

A resistor R1 for determining the gain of the driving operational amplifier 3 is connected between the output terminal of the comparison circuit operational amplifier 2 and the inverting input terminal of the driving operational amplifier 3. A resistor R2 that determines the gain of the operational amplifier 3 and a capacitor C2 for an active low pass filter are connected between the inverting input terminal and the output terminal of the drive operational amplifier 3.

The driving operational amplifier 4 is inverted between the output terminal of the driving operational amplifier 3 and the inverting input terminal of the driving operational amplifier 4 in the next stage and between the inverting input terminal and the output terminal of the driving operational amplifier 4. Are connected to resistors R5 and R6 (resistance value of R5 = resistance value of R6).

A motor 5 is provided between the output terminal of the driving operational amplifier 3 and the output terminal of the driving operational amplifier 4.
Drive coil 12 is connected. That is, the driving operational amplifiers 3 and 4 correspond to the adder 59 of FIG. 7.

A differential type positive feedback circuit 8 consisting of a series circuit of a capacitor C4 and a resistor R4 is connected between the output terminal of the driving operational amplifier 4 and the inverting input terminal of the driving operational amplifier 3. This positive feedback circuit 8 constitutes a differential type positive feedback loop with respect to the drive operational amplifier 3, and includes a drive coil 12 to a speed detection coil 13.
It has the function of compensating for the induction fogging.

Further, a resistor Rs that determines the negative feedback gain of the speed detection signal is connected between the speed detection coil 13 and the inverting input terminal of the drive operational amplifier 3. The speed detecting coil 13 is the speed detecting coil 4 shown in FIG.
Equivalent to 9.

The non-inverting input terminals of the comparator operational amplifier 2 and the drive operational amplifiers 3 and 4 are connected to the ground.

The circuit shown in FIG. 8 operates as follows.
The comparator operational amplifier 2 amplifies a difference signal between the reference signal input to the reference signal input terminal 1 and the rotational position signal output from the rotational position sensor 6, and sends the amplified signal to the drive operational amplifier 3. The drive operational amplifier 3 amplifies a difference signal between the output signal of the comparison circuit operational amplifier 2 and the signal from the speed detection coil 13, and the drive operational amplifier 4 and the drive coil 1 are amplified.
Send to 2. The drive operational amplifier 4 inverts the signal from the drive operational amplifier 3 and sends it to the drive coil 12.

When it is necessary to change the optical axis of the variable optical axis prism due to camera shake, the reference signal Er is applied to the reference signal input terminal 1 and the rotational position signal E0 is obtained at the rotational position signal output terminal 7. Then, the relational expression of E0 = −Er holds (provided that the resistance values of the resistor Rr and the resistor Rp are equal). If this relational expression holds over a wide frequency range of the reference signal Er, it means that the motor control device of FIG. 8 has excellent control characteristics.

[0018]

However, in the conventional motor control device described above, as shown in FIG.
A gain peak occurs at a frequency near Hz. Although the peak can be reduced by the positive feedback circuit composed of the series circuit of the capacitor C4 and the resistor R4,
The peak size changes due to temperature fluctuations and variations in the performance of the variable optical axis prism itself, which may cause oscillation.

The present invention has been made to solve such a problem, and an object thereof is to prevent the occurrence of a gain peak in a motor control device or the like.

[0020]

In order to solve the above problems, the present invention provides a movable object, a means for driving the movable object, and a differential acting as a minor loop with respect to the means for driving the movable object. Type negative feedback circuit and a differential type positive feedback circuit that acts as a minor loop for the means for driving the movable object, and are for applying the differential type positive feedback to the drive amplifier. The position control device for a movable object is characterized in that a transfer characteristic for applying a differential type negative feedback is formed together with the transfer characteristic, and a frequency characteristic for suppressing a peak of gain is obtained by the interaction thereof.

The present invention also acts as a minor loop for the variable optical axis prism, the motor for changing the optical axis of the variable optical prism, the means for driving the motor, and the means for driving the motor. A differential type negative feedback circuit and a differential type positive feedback circuit that acts as a minor loop for the means for driving the motor are provided, and for applying the differential type positive feedback to the drive amplifier. The variable optical axis prism device is characterized in that a transfer characteristic for applying a negative feedback of a differential type is formed together with the transfer characteristic, and a frequency characteristic for suppressing a gain peak is obtained by the interaction thereof.

Furthermore, the present invention comprises a variable optical axis prism,
A motor for changing the optical axis of the variable optical prism,
Means for driving the motor, differential type negative feedback circuit acting as a minor loop for the means for driving the motor, and differential positive feedback circuit acting as a minor loop for the means for driving the motor And a transfer characteristic for applying differential negative feedback to the drive amplifier and a transfer characteristic for applying negative differential feedback are formed, and the interaction suppresses the peak of the gain. And an image pickup device for converting an image of a subject passing through the variable optical axis prism into an electric signal.

[0023]

According to the present invention, due to the interaction between the differential type negative feedback circuit and the differential type positive feedback circuit, the phase is delayed even though it exhibits a drop characteristic with respect to the frequency because it is integral with the gain. The characteristic of not coming is realized. Therefore, the peak of the gain is suppressed.

[0024]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a motor control device according to an embodiment of the present invention. Here, FIG.
The same numbers are given to the portions corresponding to.

As shown in this figure, the motor control device according to the embodiment of the present invention has a capacitor C3 and a resistor R3 between the output terminal and the inverting input terminal of the drive operational amplifier 3.
A differential type negative feedback circuit 9 composed of a series circuit of is provided.

In FIG. 1, a reference signal is input to the reference signal input terminal 1 as in FIG. A resistor Rr that determines the gain of the reference signal is connected between the reference signal input terminal 1 and the inverting input terminal of the comparison circuit operational amplifier 2. Further, between the inverting input terminal and the output terminal of the comparator operational amplifier 2, a resistor R that determines the gain of this operational amplifier is provided.
θ is connected. Furthermore, operational amplifier 2 for comparison circuit
A resistor Rp that determines the gain of the rotational position signal generated by the rotational position sensor 6 is connected to the inverting input terminal of.

A resistor R1 for determining the gain of the driving operational amplifier 3 is connected between the output terminal of the comparison circuit operational amplifier 2 and the inverting input terminal of the driving operational amplifier 3. Further, between the inverting input terminal and the output terminal of the drive operational amplifier 3, a resistor R2 that determines the gain of the operational amplifier 3, a capacitor C2 for an active low pass filter, and the differential type negative feedback circuit 9 described above are provided. It is connected in parallel.

The driving operational amplifier 4 is inverted between the output terminal of the driving operational amplifier 3 and the inverting input terminal of the driving operational amplifier 4 in the next stage, and between the inverting input terminal and the output terminal of the driving operational amplifier 4. Are connected to resistors R5 and R6 (resistance value of R5 = resistance value of R6).

A motor 5 is provided between the output terminal of the driving operational amplifier 3 and the output terminal of the driving operational amplifier 4.
Drive coil 12 is connected.

A differential type positive feedback circuit 8 consisting of a series circuit of a capacitor C4 and a resistor R4 is connected between the output terminal of the driving operational amplifier 4 and the inverting input terminal of the driving operational amplifier 3.

A resistor Rs that determines the negative feedback gain of the speed detection signal is connected between the speed detection coil 13 and the inverting input terminal of the drive operational amplifier 3.

The circuit shown in FIG. 1 operates as follows.
The comparator operational amplifier 2 amplifies a difference signal between the reference signal input to the reference signal input terminal 1 and the rotational position signal output from the rotational position sensor 6, and sends the amplified signal to the drive operational amplifier 3. The drive operational amplifier 3 amplifies a difference signal between the output signal of the comparison circuit operational amplifier 2 and the signal from the speed detection coil 13, and the drive operational amplifier 4 and the drive coil 1 are amplified.
Send to 2. The drive operational amplifier 4 inverts the signal from the drive operational amplifier 3 and sends it to the drive coil 12.
At this time, the peak of the gain is suppressed by the interaction between the differential positive feedback circuit 8 and the differential negative feedback circuit 9.

FIG. 2 is a diagram showing a gain-frequency characteristic of the motor control device shown in FIG. As is clear from this figure, in this embodiment, the peak of the gain that has been conventionally generated at a frequency near 100 Hz is not generated at all. This is because the peak of the gain is suppressed by the interaction between the differential positive feedback circuit 8 and the differential negative feedback circuit 9 described above. The reason why the gain peak is suppressed will be described below.

FIG. 3 is a block diagram showing the motor control device of FIG. In this figure, e is the voltage,
i is current, τ is torque, ω is rotational speed, and θ is angle. The correspondence between FIG. 3 and FIG. 1 will be described below.

Ratio Rθ of resistance values of the resistor Rθ and the resistor Rr
The transfer characteristic Gr represented by / Rr determines the comparison gain of the reference signal. The gain Kp of the rotational position sensor 6 converts the rotational position θ of the rotor 11 of the motor 5 into a voltage e. The transfer characteristic Gp represented by the ratio Rθ / Rp of the resistance values of the resistor Rθ and the resistor Rp determines the comparison gain of the rotational position signal. G1 (s), which is the total transfer characteristic of the drive operational amplifiers 3 and 4, can be expressed by the following equation [1].

G1 (s) = (R2 / R1) · 1 / (1 + sC2R2) ... [1] In this formula [1], R1, R2, and C2 are the resistance value of the resistor R1 and the resistance value of the resistor R2, respectively. , Capacitor C
The capacitance is 2 (the same applies to the following equations).

The transfer characteristic G2 (s) of the differential type negative feedback circuit 9 consisting of the series circuit of the capacitor C3 and the resistor R3 can be expressed by the following equation [2]. G2 (s) = sC3R1 / (1 + sC3R3) ... [2]

The transfer characteristic G3 (s) of the differential type positive feedback circuit 8 consisting of the series circuit of the capacitor C4 and the resistor R4 can be expressed by the following equation [3]. G3 (s) = sC4R1 / (1 + sC4R4) ... [3]

Ratio R1 of resistance values of the resistor R1 and the resistor Rs
The transfer characteristic Gs represented by / Rs determines the addition gain of the speed signal. The transfer characteristic 1 / R corresponding to the winding resistance of the drive coil 12 of the motor 5 converts the voltage e into the current i. The torque constant Kt of the motor 5 converts the current i into the torque τ. The transfer characteristic 1 / (J · s + D) determined by the inertia J of the rotation system of the motor 5 and the viscous resistance D converts the torque τ into the rotation speed ω. Spring constant K of bellows 46c
y converts the rotational position θ into torque τ. The gain Ks of the speed detection coil 13 converts the rotation speed ω into the voltage e. The transfer characteristic Kid, which is determined by the gain Kid of the induction fog from the drive coil 12 to the speed detection coil 13,
s converts current i into voltage e.

As described above, in the present embodiment, the transfer characteristic G3 (s) for applying differential positive feedback to the drive amplifier and the transfer characteristic G2 (s for applying differential negative feedback are provided. ) Has been formed. Then, the frequency characteristic that suppresses the above-described gain peak is obtained by the interaction.

FIG. 4 is a signal flow diagram showing the control loop characteristics of the motor control device shown in FIG. Next, referring to this figure, transfer characteristics G2 (s) and G3
The interaction of (s) will be described in detail.

In this figure, Gd (s) is the transfer characteristic of the nodes n2 to n4.
(S) can be represented by the following formula [4].

[0043]

[Equation 1]

Here, T0 = C2R2, T3 = C3R
When the equation [4] is arranged with T3 = T4 = C4R4, the following equation [5] is obtained.

[0045]

[Equation 2]

Further, when T0 << 1 is set and the formula [5] is summarized, the following formula [6] is obtained.

[0047]

[Equation 3]

The denominator of the equation [6] is a quadratic characteristic equation with respect to s, and the root of the characteristic equation can be obtained by appropriately selecting R2, C3, R3, C4 and R4.
Therefore, the denominator of the equation [6] can be factorized and expressed by the following equation [7].

[0049]

[Equation 4]

Here, since T1 and T2 are obtained by factoring the denominator of the equation [6], the following equation [8],

The relationship of [9] is satisfied. T1-T2 = T3 + T4 + C3R2-C4R2 ... [8] T1 * T2 = C4R2T3-C3R2T4-T3T4 ...

[9]

T1 and T2 are time constants formed by the interaction of the differential positive feedback loop and the differential negative feedback loop. The relationship between the time constants T3 and T4 is expressed by the following equation [10]. It is important to set.

T1>T3>T2> T4 ... [10] The relation with T0 omitted in the calculation may be T4> T0 or T2>T0> T4, but the important thing is the formula [10]. is there.

Regarding the transfer characteristics in the parentheses in the equation [7], the gain in the numerator is the differential characteristic and the gain in the denominator is the integral characteristic. Regarding the phase, what is in the numerator is a phase lead and what is in the denominator is a phase delay, but even if there is a minus sign in front of s even in the denominator, it is a phase lead.

As a result, characteristic characteristics appear as a whole. That is, since the gain is integral, a characteristic appears that the phase does not delay even though it exhibits a drop characteristic with respect to the frequency. By providing this characteristic between the nodes n2 and n4, the closed loop characteristic at the total rotational position can be improved. Then, the gain peak can be suppressed by selectively setting the characteristic improving means with respect to the frequency range that originally has the peak. Then, by suppressing the peak of the gain, it becomes possible to give a margin to oscillation.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention. For example, a circuit equivalent to that in FIG. 1 can be configured using a microcomputer. In this case, the D / A converters 55 and 56 in FIG. 7 are arranged in the subsequent stage of the adders 59 and 60, and the digital integrating circuits 53 and 54 and the adders 59 and 60 are configured by a microcomputer. Further, the present invention not only controls the rotational position of the motor, but also controls the position of the movable object by the drive coil.
The same can be applied to a position control device generally configured such that the speed of the movable object is returned to the drive unit by the speed detection coil.

[0056]

As described in detail above, according to the present invention, the following effects (1) to (3) are exhibited. (1) Since the peak of the gain of the closed loop of the position control device can be strongly suppressed, it becomes difficult for oscillation to occur.

(2) Since the peak of the gain can be suppressed,
The servo band restricted by it can be expanded, and the control characteristics can be improved. (3) Since there is a margin for manufacturing variation of the controlled object, manufacturing of parts and the like becomes easy, and as a result, cost reduction can be realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a motor control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a gain-frequency characteristic of the motor control device according to the embodiment of the present invention.

FIG. 3 is a block diagram of a motor control device according to an embodiment of the present invention.

FIG. 4 is a signal flow diagram of control loop characteristics of a motor control device according to an embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a variable optical axis prism.

FIG. 6 is a diagram showing the principle of camera shake correction of a variable optical axis prism.

FIG. 7 is a diagram showing a configuration of a conventional camera shake correction device.

FIG. 8 is a circuit diagram showing a configuration of a conventional motor control device.

FIG. 9 is a diagram showing a gain-frequency characteristic of a conventional motor control device.

[Explanation of symbols]

5 ... Motor, 8 ... Differential type positive feedback circuit, 9 ... Differential type negative feedback circuit, 44, 45 ... Actuator, 46 ... Variable optical axis prism,

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G05B 3/00-3/20 G05B 11/00-13/04 G02B 7/18 H04N 5/232 H02P 5/00

Claims (5)

(57) [Claims] 1. A movable object, means for driving the movable object, differential type negative feedback circuit acting as a minor loop for the means for driving the movable object, and means for driving the movable object. And a differential positive feedback circuit that acts as a minor loop, and applies the differential positive feedback to the drive amplifier.
In order to apply differential type negative feedback together with the transfer characteristic for
The transfer characteristic of
A position control device for a movable object, which is characterized by obtaining a frequency characteristic for suppressing a peak . 2. The position control device for a movable object according to claim 1, wherein the time constant T4 of the differential positive feedback circuit is made longer than the time constant T3 of the differential negative feedback circuit. 3. Among the time constants formed by the interaction of the differential type positive feedback circuit and the differential type negative feedback circuit, when the time constant which is a phase delay is T1 and the time constant which is a phase lead is T2, The position control device for a movable object according to claim 2, wherein T1>T3>T2> T4 is selected. 4. A variable optical axis prism, a motor for changing the optical axis of the variable optical prism, a means for driving the motor, and a differential negative type acting as a minor loop for the means for driving the motor. A feedback circuit and a differential positive feedback circuit that acts as a minor loop for the means for driving the motor are provided, and the differential positive feedback is applied to the drive amplifier.
In order to apply differential type negative feedback together with the transfer characteristic for
The transfer characteristic of
A variable optical axis prism device, which obtains a frequency characteristic that suppresses peaks. 5. A variable optical axis prism, a motor for changing an optical axis of the variable optical prism, a means for driving the motor, and a differential negative type acting as a minor loop for the means for driving the motor. A feedback circuit and a differential positive feedback circuit that acts as a minor loop for the means for driving the motor are provided, and the differential positive feedback is applied to the drive amplifier.
In order to apply differential type negative feedback together with the transfer characteristic for
The transfer characteristic of
An image pickup device comprising: an image pickup element for converting an image of a subject that has passed through the variable optical axis prism into an electric signal, which is characterized by obtaining a frequency characteristic for suppressing a peak.