JPH03181631A - Control circuit for actuator for variable characteristic suspension - Google Patents

Abstract

PURPOSE:To speedily obtain a desired suspension property and to prolong a lifetime of an actuator by rotating a flat motor of the actuator forward and reversely, and using light or magnetism for detecting the stop position thereof. CONSTITUTION:For example, in the case of switching a suspension property from soft to hard, a hard switch 22 is turned on to set an FF2 so that a signal at an H level is sent to the terminal B of a multiplexer 31 through the OR circuit of a rotation command circuit 24. In the case of only the input of the terminal B, a motor drive circuit 2' is driven to rotate forward a flat motor 2, and a light reflecting plate or magnet 11 rotated together with the motor 2 reaches a position of a hard 1 position detection circuit 26 to come in a halt. In this state, light emitted from the hard 1 position detection circuit 26 is reflected by the light reflecting plate 11, or a magnetic field acts on a Hall effect element to generate the detection signal of the H level. Accordingly, the FF2 is reset so that the present position is stored in the hard 1 position storage circuit of a present position storage circuit 29. Therefore, an operation can be performed by a suspension property corresponding to the position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control circuit for an actuator for a variable characteristic suspension that can change the stiffness of a suspension in a traveling vehicle.

In particular, the present invention provides a control circuit for an actuator for a variable-characteristic suspension that allows quick manual switching of suspension characteristics depending on the driving conditions of the vehicle and the state of the road surface.

[Conventional technology]

Dual-mode suspensions have been proposed that change the stiffness of the suspension depending on the vehicle's driving conditions and road surface conditions. For example, a sports mode with high rigidity suitable for sports cars, and a touring mode with supple suspension suitable for high-end touring cars can be manually switched from the driver's seat. Suspensions have been devised to provide two types of ride comfort.

Such a variable characteristic suspension includes a cylinder that has an upper piston chamber and a lower piston chamber inside, and a piston rod that slides freely within the cylinder and has a communication passage that communicates the upper piston chamber and the lower piston chamber. and a rotary valve that changes the cross-sectional area of the communication passage by changing the rotation angle of a control rod inserted into the piston rod using an actuator.

Therefore, when the motor changeover switch is switched, the rotary valve rotates to change the amount of oil flowing through the communication passage in the cylinder, thereby changing the characteristics of the suspension.

A conventional actuator for changing the rotation angle of the control rod will be described with reference to the schematic diagram of FIG.

In FIG. 8, the actuator 75 includes a DC motor 80 that is controlled by instructions from a mode changeover switch 78 that can be manually instructed from the driver's seat of the vehicle, reduction gears 81 and 82 that reduce the rotation of the DC motor 8o, and 83
a reduction gear mechanism consisting of; a conductive brush 84 fixed to the reduction gear mechanism; a switch pattern 85 in sliding contact with the conductive brush 84; and a gear 8 of the reduction gear mechanism.
3 and the control rod 86 connected to the DC
It consists of a brake circuit 87 for a motor 80.

The mode changeover switch 78 includes, for example, a soft mode switch 76 that makes the suspension softer and a hard mode switch 77 that makes the suspension harder. Further, as shown in FIG. 8, the switch pattern 85 includes a right switch pattern 85-1, a left switch pattern 85-2, and an upper switch pattern 85-3.
, lower switch pattern 85-4 and center switch pattern
It is composed of pattern 85-5. Further, the conductive brush 84 is composed of three brushes connected to each of the switch patterns 85 described above.

In a variable characteristic suspension equipped with an actuator 75 having such a configuration, when the driver wishes to change the ride comfort, he or she can manually change the mode selector switch 78 from the driver's seat of the vehicle to a desired mode, for example, soft mode 76.
Or switch to hard mode 77. The actuator 75 is activated by a control switch inserted into a piston rod (not shown) in response to an instruction from the mode changeover switch 78.
The rod 86 is rotated to change the cross-sectional area of the communication passage that communicates the piston upper chamber and the piston lower chamber by means of a rotary valve (not shown) connected to the control rod 86.

When a load is applied to the suspension 16 (Fig. 4),
The oil pressure in the cylinder changes depending on the cross-sectional area of the communication passage that communicates the piston upper chamber and the piston lower chamber. This change in oil pressure changes the stiffness of the suspension 16.

That is, in response to an instruction from the mode changeover switch 78 on the driver's seat, a control valve (not shown) fixed to a control rod 86 inserted into the piston rod is rotated by a DC motor 80, and the upper chamber of the piston and the piston are rotated. By changing the cross-sectional area of the communication path that communicates with the lower chamber,
The characteristics of the suspension 16 can be changed.

Next, the operations of the mode changeover switch 78 and the actuator 75 will be explained in detail.

The mode changeover switch 78 is set to soft mode 7 as shown in FIG.
When in position 6, the current from power supply 88 is
Motor 80, central switch pattern 85-5, conductive brush 84, lower switch pattern 85-4 (upper switch pattern 85-3), soft mode 76, ground 89
The DC motor 80 rotates as the current flows through the circuit. As shown in FIG. 8, the center brush of the conductive brush 84 is connected to the upper switch pattern 85-3 and the lower switch pattern 85-4.
When rotated to a position far away from the
The circuit is disconnected and the DC motor 80 stops rotating.

Next, if it is desired to change the mode of the suspension 16 to the hard mode, the mode changeover switch 78 is switched to the hard mode 77. In this case, current from power supply 88 flows through DC motor 80, center switch pattern 85-
5. Conductive brush 84, right switch pattern 85-1 (
Left switch pattern 85-2), hard mode 77,
The DC motor 80 rotates as the current flows through the ground 89 circuit.

Then, the center brush of the conductive brush 84 is connected to the left switch.
When the DC motor 80 rotates to a position between the pattern 85-2 and the right switch pattern 85-1 (separated position), the circuit is disconnected and the rotation of the DC motor 80 is stopped.

Similarly, each time the mode is switched, the control rod 86 rotates 90 degrees, so the area of the communication passage that communicates the upper and lower piston chambers changes, and the stiffness of the suspension changes.

Note that even after the power supply to the DC motor 80 is stopped, the DC motor 80 continues to rotate due to inertia, and at this time generates an electromotive force. The electromotive force generated at this time causes the brake circuit 87 of the DC motor 80 to operate. The brake circuit 87 short-circuits both ends of the DC motor 80.
apply sudden braking.

[Problem to be solved by the invention]

The control rod 86 is rotated in only one direction by the DC motor 80. Therefore, if you set the suspension stiffness to three types: soft, medium, and hard (assuming that there are two stopping positions for hard), there are four setting positions at 90-degree intervals, and the desired setting When selecting the position, set the motor to 240
The desired position may not be reached unless it is rotated once. In other words, it takes time to change the stiffness of the suspension.

Further, in the actuator 75, a switch pattern 85 for controlling the rotational position of the control rod 86 and the conductive brush 84 are in mechanical contact.

These mechanical contacts affect the life of the actuator depending on the state of wear of the contact portions.

The present invention is intended to solve the above problems.
When changing the stiffness of the suspension, use the control
The object of the present invention is to provide a control circuit for an actuator for a suspension with variable characteristics that enables forward and reverse rotation of a motor that changes a rod.

Another object of the present invention is to provide a control circuit for an actuator for a variable characteristic suspension, which has an actuator that is simple in structure and has a long life.

[Means to solve the problem]

FIG. 1 is a block diagram showing the principle of a control circuit for an actuator according to the present invention. In FIG. 1, a flat motor 2 is driven by a motor drive circuit 2' to rotate a control rod 17 shown in FIG. 4 in forward and reverse directions. The soft switch 21 and hard switch 22 (as described above) are selected to place the control rod 17 in the soft position, the hard position (both positions provide the same hard state), and the medium position. A medium switch 23 is provided (commonly used to select one of two hard positions), and a medium switch 23. Each of the switches is connected to FFI to FF3, which output an H level when each switch is turned on.

The rotation command circuit 24 gives a rotation command to the flat motor 2 to rotate the control rod 17 in the forward direction when the outputs of FFI to FF3 are at H level. The flat motor 2 includes a light reflecting plate 1 that rotates as the flat motor 2 rotates.
1 is provided.

A soft position detection circuit 25, a hard 11 position detection circuit 26, a medium position detection circuit 27, and a hard 12 position detection circuit are arranged at 90 degree intervals and correspond to the light emitting/receiving device 14 shown in FIGS. 2 and 3. The circuit 28 is located at a position facing the light reflection plate 11, receives the light emitted from each position detection circuit from the light reflection plate 11, and outputs an H level.

Note that the reference numeral 11 can be replaced with a magnet and the reference numeral 14 can be replaced with a Hall effect element. In this case, when the magnet 11 faces each of the position detection circuits 25, 26, 27, and 28, an H level detection signal will be obtained from each of the position detection circuits.

The current position storage circuit 29 stores the hardware 1 and the hardware 12.
The hard position is memorized by the H level of the position detection circuits 26 and 28. Further, the reverse rotation command circuit 30 outputs an H level signal based on the H level signal of the FFI or FF3 and the H level signal of the current position storage circuit 29.

The multiplexer 31 rotates the flat motor 2 forward when only the signal from the rotation command circuit 24 is received, and rotates the flat motor 2 in the reverse direction when there are signals from the rotation command circuit 24 and the reverse command circuit 30. Switch to .

[For production]

A vehicle equipped with a variable characteristic suspension selects a desired suspension characteristic from a mode indicating device (not shown) in the driver's seat. For example, when changing the suspension characteristics from a soft state to a hard state, the hard switch 22 is set to ONL and FF2 is set. FF2's H
The level signal passes through the OR circuit of the rotation command circuit 24 and is input to the B terminal of the multiplexer 31. When only the input terminal B of the multiplexer 310 is input, the multiplexer 31 operates to drive the motor drive circuit 2' and rotate the flat motor 2 in the forward direction.

The light reflecting plate (or magnet) 11, which rotates with the rotation of the flat motor 2, reaches a position facing the hardware 11 position detection circuit 26. Then, the flat motor 2 stops at that position. At this time, the hardware 11 position detection circuit 26
The light emitted from is reflected by the light reflecting plate 11 and returns, and the hardware 11 position detection circuit 26 outputs an H level signal.

Alternatively, the magnetic field of the magnet acts on the Hall effect element, and the Hall effect element emits an H level detection signal. Hard 1
The H level signal of the 1 position detection circuit 26 resets the FF2 and stores the current position in the hardware 1 of the current position storage circuit 29.
It is stored by a 1-position storage circuit. Then, the vehicle is driven under suspension characteristics corresponding to the position.

After that, the suspension characteristics were changed from hard 1 to medium.
If you want to change from medium to hard 2 and from hard 2 to soft, change the switch 23.22 each time.
．． 21 are turned on in sequence, FFI to FF3 are turned on in the same manner as described above, and the control rod rotates forward by 90 degrees and then stops. That is, suspension characteristics can be changed.

When the light reflecting plate (or magnet) 11 is facing the hard 11 position detection circuit 26, the soft switch 21 is turned to O.
When N is pressed, normally it would rotate 270 degrees and stop, but in the present invention, it rotates 90 degrees in the opposite direction and stops. That is, when the soft switch 21 is turned on, the FFI is set and an H level signal is input to the rotation command circuit 24 and the reverse rotation command circuit 30. Since the hardware 11 position storage circuit remembers that the H level is high, the H level signal is the A of the reverse command circuit 30.
It passes through an ND circuit and is input to the A terminal of the multiplexer 31, and the output of the rotation command circuit 24 is input to the B terminal of the multiplexer 31.

In this state, the multiplexer 31 drives the motor drive circuit 2' to rotate the flat motor 2 in the reverse direction. When the light reflecting plate (or magnet) 11 faces the hard 12 position detection circuit 28, the flat motor 2 rotates in the reverse direction in the same manner as described above when the medium switch 23 is turned on.

As described above, the present invention rotates the flat motor 2 of the actuator 15 in the forward and reverse directions to control the control rod 17.
Since the rotation angle is rotated to the desired position in the shortest distance, desired suspension characteristics can be quickly obtained.

By eliminating this, we were able to extend the life of the actuator.

〔Example〕

First, the structure of the actuator of the present invention will be explained with reference to FIGS. 2 to 4. FIG. 2 is a longitudinal cross-sectional view of the actuator according to the present invention, FIG. 3 is a cross-sectional view of the actuator according to the present invention, and FIG. 4 is a schematic explanatory diagram of the actuator and variable characteristic suspension according to the present invention. Note that FIG. 2 shows a cross-sectional view taken along the line XX' shown in FIG. 3, and FIG. 3 is a cross-sectional view taken along the Y-Y' line shown in FIG.

In FIGS. 2 and 3, a flat motor 2 is fixed inside a case 1 with a rotation stopper pin 3. As shown in FIG. The output shaft 4 of the flat motor 2 is connected to a planetary gear reduction mechanism 5.
It is connected to the. The planetary gear reduction mechanism 5 includes an upper planetary gear 5-1 and a lower planetary gear 5-2, a fixed internal gear 6, and a rotating internal gear 9, which are connected to each other at a central axis. Further, the fixed internal gear 6 is fixed to the bonnet of the case 1 with a fixing screw 8. Therefore, the rotation of the motor output shaft 4 is caused by the rotation of the plurality of upper planetary gears 5-
1, the upper planetary gear 5-1 revolves along the fixed internal gear 6 while rotating on its own axis. The lower planetary gear 5-2 rotates with the rotation of the upper planetary gear 5-1.
The rotational movement of is transmitted to the rotating internal gear 9. In this way, the rotation of the flat motor 2 is decelerated by the rotation and revolution of the planetary gear, and is transmitted to the actuator output shaft 10 connected to the rotary internal gear 9.

Furthermore, a light reflecting plate 1 is provided on the side of the rotational circumference of the rotating internal gear 9, and a light projecting/receiving device 14 for detecting the rotational position is provided on the fixed side facing the light reflecting plate 11. are arranged at 90 degree intervals, for example. The light emitting and receiving device 14 includes a light emitting element and a light receiving element (not shown). Further, the light emitting/receiving device 14 is attached to a substrate 13 provided in a slit 12 between the case 1 and the fixed internal gear 6, as shown in FIG.

Output shaft 10 of actuator 15 configured in this way
is connected to a control rod 17 of the suspension 16, as shown in FIG.

Now, if it is desired to switch the stiffness mode of the suspension 16, the mode of a mode indicating device (not shown) is switched to the desired mode, for example, from hard mode to soft mode. As a result, the flat motor 2 rotates, and at a position where the rotating internal gear 9 provided with the light reflecting plate 11 has rotated 90 degrees, the light emitting/receiving device 14 and the light reflecting plate 11 face each other, so that the light emitting/receiving device Light emitted from the light reflecting plate 11 hits the light reflecting plate 11, and the light receiving element of the light projecting/receiving device 14 receives the reflected light. The detection signal detected by the light receiving element causes the flat motor 2 to stop at this position. The rotation of the flat motor 2 during this period is transmitted to the planetary gear reduction mechanism 5, and further transmitted from the actuator output shaft 10 to the control/rotator 17 (see FIG. 4). Accordingly, a rotary valve (not shown) fixed to control rod 17 is rotated through an angle of 90 degrees and stopped, changing the oil pressure within suspension 16 and changing the stiffness characteristics of suspension 16.

Next, referring to FIG. 5 through FIG. 7, a description will be given of the stopper control circuit according to the present invention.

FIG. 5 is an explanatory view of the rotational direction of the actuator according to the present invention, and is an example in which the suspension has three types of stiffness characteristics: soft, hard, and medium. Note that Hard 1 and Hard 2 have the same hardness.

Now, when the suspension characteristic is soft and you select hard, the control rod 17 is rotated clockwise by the flat motor 2, and the control rod 17 is rotated clockwise by the flat motor 2.
Stop at the position. Also, from hard 1 to medium,
When rotating from medium to hard 2 and from hard 2 to soft, each rotates clockwise and stops. In addition to the case where such positioning is performed by forward rotation, when the soft state is selected from the hard state 1, the control rod 17 is caused to rotate counterclockwise.

The control rod 17 is also rotated counterclockwise when selecting medium from the state of the flat motor 2. That is, even if the suspension characteristics are set to three types: soft, medium, and hard, and the settings for hard 1 and hard 2 are the same as shown in FIG. This eliminates the need for 270 degree rotation.

A control circuit for rotating the control rod 17 clockwise and counterclockwise by the flat motor 2 is shown in FIG. 6, and a time chart thereof is shown in FIG. 7.

In FIG. 6, the same reference numerals as those shown in FIG. 1 indicate the same blocks. Each switch 2 to select suspension characteristics
1 to 23 are one-shot/multi 41 to 43
When the switches 21 to 23 are turned on, the one-shot multis 41 to 43 output an H level output for a certain period of time.

The AND circuit 51 sets the output to the H level based on the H level signal from the soft position detection circuit 25 and the H level signal from the FFI when the soft switch 21 is turned on. This H level signal not only resets the FFI, but also resets the current position memory circuit 2.
The hardware 11 position storage FF 44 and the hardware 12 position storage FF 45 of No. 9 are reset. The AND circuit 52 is
The output is set to H level by the H level signal of the hardware 2 position detection circuit 28 and the H level signal of FF2 caused by turning on the hardware switch 22. This H level output is the hard 12
The position memory FF 45 is set, and the position memory FF 44 and FF2 of the hardware 11 are reset. AND
The circuit 53 sets the output to the H level based on the H level signal of the hardware 1 position detection circuit 26 and the H level signal of the FF2 when the hardware switch 22 is turned on. This H level output sets the hardware 11 position memory FF44 and
FF2 is reset by the hard 12 position memory FF45. Further, the AND circuit 54 outputs the H level signal of the medium position detection circuit 27 and the ON state of the medium switch 23.
The output is set to H level by the H level signal of FF3. This H level signal not only resets the FF3, but also resets the FF4 for hard 11 position storage in the current position storage circuit 29.
1 and hard 12 position memory FF45 are reset.

The rotation command circuit 24 is composed of OR circuits 60 and 61, and sets the B terminal of the multiplexer 31 to the H level through the H level output of any one of FFI to FF3.

The reverse command circuit 30 is ORed with AND circuits 55 and 56.
It is composed of a circuit 62. The H level output of FFI and the H level output of FF44 for storing the hard 11 position are ANDed.
The circuit 56 is turned on, and the H level output of FF3 and the H level output of the hard 12 position memory FF45 are turned ON to the AND circuit 55, and in each case, the A terminal of the multiplexer 31 is set to the H level through the OR circuit 62. do.

In such a control circuit, the operation of the control circuit will be explained with reference to the time chart shown in FIG.

Now suppose that the suspension characteristics are in the soft position.

In this state, the hard switch 22 is turned on (see FIG. 7). One shot by turning on the hard switch 22
The output of the multi 42 is H level as shown in FIG. 7, and FF2 is set to make the output H level (■).

This H level signal passes through the OR circuits 61 and 60 of the rotation command circuit 24 and is input to the B terminal of the multiplexer 31. The multiplexer 31 drives the motor drive circuit 2' to rotate the flat motor 2 clockwise.O0 The light reflecting plate 11 rotates as the flat motor 2 rotates, and the light reflecting plate 11 is provided at the hard 1 position. The hardware 11 reaches the position of the position detection circuit 26. After the light emitted from the hardware 11 position detection circuit 26 is reflected by the light reflecting plate 11,
The light is received by the hardware 11 position detection circuit 26 and outputs an H level signal (■).

The H level signal from the hardware 11 position detection circuit 26 and the H level signal from the FF2 make the output of the AND circuit 53 go to H level (■). This H level resets the FF2 and stops the rotation of the flat motor 2. At the same time, the FF 44 for storing the hard 1 position is set to an H level output ■, and the hard 1 position is stored. Below, the fifth
1! A similar operation is performed when the suspension characteristics are selected sequentially from medium to medium, from medium to hard, and from hard to soft in the clockwise direction as shown in the figure.

Next, turn the soft switch 21 ○N to select the software in order to transition from the hard to the soft in the hard 1 position.
■Assuming that, the output of one-shot multi 41 is
Set the FFI to H level ■ and set the output to H level ■. This H level signal is input to the B terminal of the multiplexer 31 through the OR circuit 60, and is also input to the B terminal of the multiplexer 31.
input to one terminal of circuit 56. Also, the AND circuit 5
The H level output of the FF 44, which stores the previous hard 1 position, is applied to the other terminal of the switch 6. Therefore, the output of the AND circuit 56 becomes H level and the output of the AND circuit 56 becomes H level.
The output of the circuit 62 also becomes H level ■ and is applied to the A terminal of the multiplexer 31. When the H level is applied to both terminals A1B of the multiplexer 31, the multiplexer 31 operates the motor drive circuit 2' to rotate the flat motor 2 in the reverse direction.

Then, the soft position detection circuit 25 detects the flat motor 2.
It is detected that the light reflecting plate 11 has reached the soft position due to the reversal of 0, and the H level becomes 0. The output of the AND circuit 51 is set to H level by this H level signal and the H level signal of the FFI. And this H level is FF1.
1 and hard 1 or hard 2 position memory FF44.4
Reset 5.

When the light reflector 11 is in the hard 2 position and the medium switch 23 is turned on, the control circuit similarly operates as described above.
Reverse the flat motor 2.

In addition, in the description of the above embodiment, the reference numeral 11 is a light reflecting plate and the reference numeral 14 is a light projecting/receiving device, but the reference numeral 11 can be replaced with a magnet and the reference numeral 14 can be replaced with a Hall effect element. In this case, when the magnet 11 reaches the position where the position detection circuit constituted by the Hall effect element 14 exists, the Hall effect element 14 becomes H
Other operations are the same as described above, except that a level detection signal is generated.

〔Effect of the invention〕

According to the invention, it is possible to reverse the rotation of the control rod, which changes the characteristics of the suspension, so that
The desired suspension characteristics can be changed more quickly than by rotation in only one direction.

Further, according to the present invention, by using a light emitting/receiving device (or Hall effect element) to detect the rotational position of the motor, mechanical contact parts such as conductive brushes are eliminated, and the rotational position of the motor is detected by optical (or magnetic) detection. Since we used a combination that
We were able to extend the life of the actuator.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing the basic structure of the actuator control circuit according to the present invention, FIG. 2 is a vertical sectional view of the actuator according to the present invention, and FIG. FIG. 4 is a schematic explanatory diagram of the actuator and variable characteristic suspension according to the present invention, FIG. 5 is an explanatory diagram of the rotation direction of the actuator according to the present invention, FIG. 6 is an explanatory diagram of the control circuit according to the present invention, and FIG. A time chart of one embodiment, FIG. 8, is a schematic explanatory diagram of an acticoator in a conventional example. 1... Case 2... Flat motor 3... Rotating pin 4... Motor output shaft 5... Planetary gear reduction mechanism 6... Fixed internal gear 9... Rotating internal gear 10...・Actuator output shaft 11...Light reflecting plate (or magnet) 4 5 6 7 1 2 3 4 5 6 7 8 9 0 1 ・Light projecting/receiving bag! (or Hall effect element), actuator, suspension, control rod, soft switch, hard switch, medium switch, rotation command circuit, soft position detection circuit, hard 11 position detection circuit, medium position detection circuit, hard 12 position detection circuit, Current position memory circuit, reverse command circuit, multiplexer

Claims (1)

[Claims] A control device inserted into the suspension of a traveling vehicle.
In a control circuit for a variable characteristic suspension actuator that can change the stiffness of the suspension by rotating a rod, a motor is driven by a motor drive circuit to rotate the control rod in forward and reverse directions, and a motor is driven by a motor drive circuit to rotate the control rod in forward and reverse directions. A soft switch for making the suspension soft, a hard switch for making the suspension characteristics hard, a medium switch for making the suspension characteristics medium, and a first flip switch that outputs H level when the soft switch is turned on. a second flip-flop that outputs an H level when a hard switch is turned on; a third flip-flop that outputs an H level when a medium switch is turned on; a rotation command circuit that gives a rotation command to rotate the control rod in the forward direction when the output is at H level; a rotation position indicating means that rotates according to the rotation of the motor; a soft position detection circuit, a hard 1 position detection circuit, a medium position detection circuit, and a hard 2 position detection circuit that detect that the two have reached opposing positions and output an H level; and the hard 1 or hard 2 position detection circuit. A current position memory circuit that stores a hard position by the H level of the flip-flop, and an inversion circuit that outputs an H level signal based on the H level signal of the first flip-flop or the third flip-flop and the H level signal of the current position memory circuit. The motor is characterized by comprising: a command circuit; and a multiplexer that rotates the motor in the forward direction when there is only a signal from the rotation command circuit, and rotates the motor in the reverse direction when there is a signal from the reverse command circuit. Control circuit for actuator for variable characteristic suspension.