Control type vibro-isolating support

A control type vibro-isolating support includes a pulse signal generator for generating reference signals x, which represent the state of the vibration being generated by an engine. An acceleration sensor detects residual vibration on the support member side, and generates a residual vibration signal e. A controller is supplied with the reference signals x and residual vibration signal e. On the basis of the reference signals x and residual vibration signal e and in accordance with, for example, synchronous filtered X LMS algorithm, the controller generates a drive signal y so as to lower the vibration level on the member side. An engine mount is interposed between the engine and the member, and has an electromagnetic actuator. The drive circuit for the actuator is supplied with the drive signal y. The controller judges that abnormality has occurred, if a maximum value of the residual vibration signal e exceeds a threshold, and if maximum values of the signal e have occurred at the same periodicity as the reference signals x.

FIELD AND BACKGROUND OF THE INVENTION 
This invention relates to apparatus for supporting a vibrator such as a car 
engine on a support body such as a car body. In particular, the invention 
relates to a control type vibro-isolating support, that can generate 
controlling force depending on the conditions in which vibration is 
generated by a vibrator and transmitted to a support body. Abnormality in 
the vibro-isolating support can be detected for use to make the system 
more reliable. 
A conventional vibro-isolating support of this type is disclosed in 
Japanese Patent Laid Open No. H.3-24,338, for example. This prior art 
includes a supporting elastic body interposed between a vibrator and a 
support body. The elastic body partially defines a fluid chamber, which is 
filled with fluid. An elastic body supports a movable plate so that the 
plate can change the volume of the chamber. An electromagnetic actuator 
includes a permanent magnet and an electromagnet. The actuator can 
properly displace the movable plate so as to change the volume of the 
chamber. The volume change elastically deform the elastic body in the 
expanding direction. This generates controlling force which can cancel the 
vibration transmitted to the vibro-isolating support. 
Specifically, the electromagnetic actuator attracts the movable plate to a 
specified neutral position, where the supporting force of the elastic 
body, which supports the plate, balances with the magnetic force of the 
permanent magnet. Proper adjustment of the magnetic force generated by the 
electromagnet increases or decreases the magnetic force applied to the 
plate. It is therefore possible to change the clearance between the plate 
and the actuator to any value within a possible range, thereby varying the 
volume of the fluid chamber. 
Conventional control type vibro-isolating supports such as mentioned above, 
however, include no means for detecting their own trouble, degradation or 
other abnormality. In order for the apparatus to be sufficiently reliable, 
there is a need to use highly durable members or parts, which make the 
trouble or degradation offer no problem, but are expensive. 
SUMMARY OF THE INVENTION 
In view of the problem in the prior art, it is the object of the present 
invention to provide a control type vibro-isolating support which can 
efficiently detect trouble, degradation or other abnormality without 
needing highly durable and expensive members. 
The first invention is a control type vibro-isolating support comprising: a 
source of control vibration which is interposed between a vibrator and a 
support body, and which can generate control vibration; reference signal 
generation means for detecting the state of the vibration being generated 
by the vibrator, and for outputting a reference signal; residual vibration 
detection means for detecting residual vibration on the support body side, 
and for outputting a residual vibration signal; control means for 
generating a drive signal for driving the source of control vibration on 
the basis of the reference signal and the residual vibration signal so as 
to damp the vibration on the support body side; state detection means for 
detecting the state of the vibro-isolating support; and abnormality 
judgment means for judging if there is abnormality on the basis of the 
detection result of the state detection means. 
The second invention is a control type vibro-isolating support according to 
the first invention, and further comprising: alarm raising means for 
raising an alarm if the abnormality judgment means judges abnormality 
occurring. 
The third invention is a control type vibro-isolating support according to 
each of the first invention and second invention, wherein: the vibrator 
generates periodic vibration. 
The 4th invention is a control type vibro-isolating support according to 
the third invention, wherein: the state detection means comprises 
maximum/minimum detection means for detecting the maximum or minimum value 
of the residual vibration signal for each cycle of the reference signal, 
and wherein: the abnormality judgment means judges if there is abnormality 
on the basis of the magnitude of the maximum or minimum value and the 
intervals at which the maximum or minimum values of the residual vibration 
signal have occurred for cycles of the reference signal. 
The 5th invention is a control type vibro-isolating support according to 
the 4th invention, wherein: the abnormality judgment means judges 
abnormality occurring if the modulus (absolute value) of the maximum or 
minimum value exceeds a specified threshold and if the maximum or minimum 
values have periodically occurred. 
The 6th invention is a control type vibro-isolating support according to 
the 4th invention, wherein: the abnormality judgment means judges 
abnormality occurring if the modulus of the maximum or minimum value 
exceeds a specified threshold and if the maximum or minimum values have 
occurred at the same cycle as the reference signal. 
The 7th invention is a control type vibro-isolating support according to 
each of the third invention through 6th invention, wherein: the state 
detection means comprises auto-correlation function operation means for 
finding the auto-correlation function of the residual vibration signal 
with a time lag which is an integral number of times as long as the period 
of the reference signal, and wherein: the abnormality judgment means 
judges if there is abnormality on the basis of the auto-correlation 
function. 
The 8th invention is a control type vibro-isolating support according to 
the 7th invention, wherein: the abnormality judgment means judges 
abnormality occurring if the auto-correlation function exceeds a specified 
threshold. 
The 9th invention is a control type vibro-isolating support according to 
each of the third invention through the 8th invention, wherein: the state 
detection means comprises cross-correlation function operation means for 
finding the cross-correlation function of the residual vibration signal 
and the drive signal, and wherein: the abnormality judgment means judges 
if there is abnormality on the basis of the cross-correlation function. 
The 10th invention is a control type vibro-isolating support according to 
the 9th invention, wherein: the abnormality judgment means judges 
abnormality occurring if the cross-correlation function exceeds a 
specified threshold. 
The 11th invention is a control type vibro-isolating support according to 
each of the 9th invention and 10th invention, wherein: the abnormality 
judgment means judges abnormality occurring, which is higher-order 
divergence, if the cross-correlation function exceeds a specified 
threshold at a plurality of points within a time lag of which the maximum 
value is the period of the reference signal. 
The 12th invention is a control type vibro-isolating support according to 
each of the first invention through the 11th invention, wherein: the 
source of control vibration comprises a supporting elastic body interposed 
between the vibrator and the support body, a diaphragm, a movable member 
which can be magnetized and is elastically supported so as to form part of 
the diaphragm, a fluid chamber defined at least partially by the elastic 
body and the diaphragm, fluid in the chamber, and an electromagnetic 
actuator for operation in response to the drive signal to displace the 
movable member so as to change the volume of the chamber. 
The 13th invention is a control type vibro-isolating support according to 
the 12th invention, wherein: the state detection means comprises clearance 
detection means for detecting the clearance between the movable member and 
the electromagnetic actuator, and wherein: the abnormality judgment means 
judges if the source of control vibration is abnormal on the basis of the 
clearance. 
The 14th invention is a control type vibro-isolating support according to 
the 13th invention, wherein: the electromagnetic actuator includes an 
exciting coil, and wherein: the clearance detection means comprises 
induced voltage detection means for detecting voltage induced under no 
control in the coil if the vibrator vibrates and if the actuator is not 
supplied with the drive signal. 
The 15th invention is a control type vibro-isolating support according to 
the 14th invention, wherein: the abnormality judgment means judges that 
abnormality has occurred, which is decrease in the clearance, in the 
source of control vibration if the maximum or minimum value of the voltage 
induced under no control exceeds a specified value. 
The 16th invention is a control type vibro-isolating support according to 
each of the 14th invention and 15th invention, wherein: the abnormality 
judgment means judges that abnormality has occurred, which is increase in 
the clearance, in the source of control vibration if the maximum or 
minimum value of the voltage induced under no control is less than a 
specified value. 
The 17th invention is a control type vibro-isolating support according to 
each of the 12th invention through the 16th invention, wherein: the 
electromagnetic actuator comprises an exciting coil, and wherein: the 
state detection means comprises induced voltage detection means for 
detecting voltage induced under no control in the coil if the vibrator 
vibrates and if the actuator is not supplied with the drive signal, the 
abnormality judgment means judging the source of control vibration 
abnormal if the voltage induced under no control is zero. 
The 18th invention is a control type vibro-isolating support according to 
each of the 12th invention through the 17th invention, wherein: the 
electromagnetic actuator includes an exciting coil, and wherein: the state 
detection means comprises maximum current value detection means for 
detecting the maximum value of the control current actually flowing 
through the coil, the abnormality judgment means judging the actuator in a 
high temperature state if the maximum value of the control current is less 
than a specified threshold. 
The 19th invention is a control type vibro-isolating support according to 
the 18th invention, and further comprising control current correction 
means for lowering the maximum value of the control current if the 
abnormality judgment means judges the electromagnetic actuator in a high 
temperature state. 
The 20th invention is a control type vibro-isolating support according to 
each of the 12th invention through the 19th invention, wherein: the source 
of control vibration has an orifice and an auxiliary fluid chamber of 
variable volume, which communicates through the orifice with the 
first-mentioned fluid chamber, and wherein: the chambers and the orifice 
are filled with the fluid. 
In the first invention, the state detection means detects the states of 
means and signals of the control type vibro-isolating support. On the 
basis of the detection results, the abnormality judgment means judges if 
there is trouble, degradation or other abnormality. It is therefore 
possible to recognize the abnormality without needing to make the means of 
highly durable and expensive parts. For example, it is possible to 
positively stop the operation of the vibro-isolating support before the 
support completely fails. 
In the second invention, the alarm raising means raises an alarm in 
response to abnormality occurring. 
If the vibrator generates periodic vibration, as in the third invention, it 
is possible to judge if there is abnormality by detecting the states of 
the residual vibration signal and the drive signal, as in the 4th 
invention through 9th invention, which is described below in detail. In 
other words, it is possible to judge if there is abnormality by only 
monitoring the signals required for vibration damping control, without 
needing a new sensor. 
For example, in the 4th invention, the magnitude of each maximum or minimum 
value of the residual vibration signal detected by the maximum/minimum 
detection means as the state detection means, that is, the level of the 
residual vibration signal must be low if the vibration damping control is 
well executed so that the vibration is canceled by the control vibration 
generated by the source of control vibration. It can be considered that, 
if the residual vibration signal level is high, either vibration generated 
by something but the vibrator is inputted into the support body, or the 
source of control vibration, the control by the control means, or 
something is abnormal so that the vibration damping control is not well 
executed. 
In the former case, where nothing is abnormal, but the residual vibration 
signal level is high, the maximum or minimum values of the residual 
vibration signal are determined by the disturbance vibration transmitted 
from something but the vibrator. If the disturbance vibration is random 
vibration, its maximum or minimum values occur at random intervals. Even 
if the disturbance vibration is periodic vibration, the maximum/minimum 
value detection means finds the maximum or minimum value of the residual 
vibration signal in each cycle of the reference signal. Accordingly, if 
the cycle of the disturbance vibration does not coincide with that of the 
reference signal (that is, the cycle of the vibration generated by the 
vibrator), the maximum or minimum values cannot periodically occur. 
The abnormality judgment means can therefore judge if there is abnormality, 
on the basis of the magnitude of the maximum or minimum values of the 
residual vibration signal detected by the maximum/minimum value detection 
means and the intervals at which the values have occurred. 
In the 5th invention, the abnormality judgment means judges if the 
specified threshold is exceeded by each of the maximum or minimum values 
detected by the maximum/minimum value detection means, and if the values 
have periodically occurred. Therefore, if it is judged that the values 
exceed the threshold and they have periodically occurred, it can be 
considered that there is abnormality. 
In the 6th invention, the abnormality judgment means judges if the 
specified threshold is exceeded by each of the maximum or minimum values 
detected by the maximum/minimum value detection means, and if the values 
have occurred at the same cycle as the reference signal. This completely 
distinguishes the condition where most of the vibration of the vibrator is 
transmitted to the support body side without being damped, even though the 
vibration damping control is executed. 
In the 7th invention, the auto-correlation function of the residual 
vibration signal computed by the auto-correlation function operation means 
as the state detection means has the time lag .tau. as its variable which 
is an integral number of times as long as the period T of the reference 
signal (.tau.=T, 2T, 3T . . . ). Therefore, if the residual vibration 
signal is periodic in synchronism with the reference signal, the 
auto-correlation function increases. If not, the function decreases. The 
period of the reference signal is nothing but the period of the vibration 
generated by the vibrator. It can therefore be considered that, if the 
residual vibration signal is judged periodic synchronously with the 
reference signal, components of the vibration generated by the vibrator 
are transmitted to the support body. This is a case where the vibration is 
not damped even though the vibration damping control is executed. The 
abnormality judgment means can therefore judge if there is abnormality on 
the basis of the auto-correlation function of the residual vibration 
signal found by the auto-correlation function operation means. 
In the 8th invention, the abnormality judgment means judges if the 
specified threshold is exceeded by the auto-correlation function found by 
the auto-correlation function operation means. If the threshold is judged 
to be exceeded, it can be considered that there is abnormality. 
In the 9th invention, the cross-correlation function detected by the 
cross-correlation function detection means as the state detection means is 
the cross-correlation function of the residual vibration signal and the 
drive signal. The fact that the cross-correlation function is large means 
that the control vibration generated by the source of control vibration is 
detected as the residual vibration. This is a case where the vibration 
damping control is not normally executed. Besides, no vibration generated 
by something but the vibrator and inputted into the support body 
influences the cross-correlation function of the residual vibration signal 
and the drive signal. 
In the 10th invention, the abnormality judgment means judges if the 
specified threshold is exceeded by the cross-correlation function found by 
the cross-correlation function operation means. If the threshold is judged 
to be exceeded, it can be considered that there is abnormality. 
If the cross-correlation function of the residual vibration signal and the 
drive signal found by the cross-correlation function operation means has 
two or more peak values within a time lag of which the maximum value is 
the period of the reference signal, it can be considered that the drive 
signal contains (higher) harmonic components of the reference signal, 
which influence the residual vibration signal. 
Therefore, if, as in the 11th invention, the abnormality judgment means 
judges that the specified threshold is exceeded by the cross-correlation 
function of the residual vibration signal and the drive signal at a 
plurality of points within a time lag .tau. of which the maximum value is 
the period T of the reference signal (.tau.=0 to T), it can be considered 
that there is abnormality which is higher-order divergence. 
In the 12th invention, the source of control vibration of each of the first 
invention through 11th invention is a source of control vibration of the 
type filled with fluid. Specifically, the elastic body defines the fluid 
chamber, which is filled with the fluid. This is equivalent to two spring 
elements interposed in parallel between the vibrator and support body. One 
of the elements is the support spring by the elastic body. The other 
element is the expansion spring by the elastic deformation in the 
expanding direction of the elastic body due to the change in volume of the 
fluid chamber. 
If the movable member is displaced by the magnetic force generated by the 
electromagnetic actuator, the volume of the fluid chamber changes, 
elastically deforming the expansion spring. This generates controlling 
force of the magnitude which is the multiplication product of the spring 
constant and the amount of deformation of the expansion spring. 
Therefore, by properly controlling this magnetic force generated by the 
actuator, it is possible to apply active force between the vibrator and 
support body. The active force interferes with the vibration input from 
the vibrator side. Consequently, if the control means properly generates a 
drive signal, and if the signal is supplied to the actuator, the 
controlling force cancels the vibration transmitted from the vibrator side 
to the support body side, thereby damping the vibration level on the 
support body side. 
It is important for such a source of control vibration to keep the 
clearance between the movable member and electromagnetic actuator a proper 
value, in order to generate precise controlling force. The clearance may, 
however, be varied from the initial proper value by degradation of the 
member supporting the movable member, demagnetization of the permanent 
magnet, or the like. 
In the 13th invention, the clearance detection means detects the clearance 
between the movable member and electromagnetic actuator. On the basis of 
the detected clearance, the abnormality judgment means judges if there is 
abnormality. 
The clearance between the movable member and electromagnetic actuator may 
be detected from the output of a gap sensor. However, if the actuator 
includes a yoke, an exciting coil and a permanent magnet, and when the 
movable member of magnetizable material is displaced, voltage is induced 
between both terminals of the coil. The induced voltage changes in 
magnitude with the clearance. 
Therefore, if, as in the 14th invention, the apparatus has induced voltage 
detection means, the clearance between the movable member and 
electromagnetic actuator can be detected easily as the induced voltage of 
the exciting coil. The reason is that, if no vibration is generated by the 
vibrator, the movable member is vibrated by the change in volume of the 
fluid chamber due to the vibration input into the elastic body, and, if 
the actuator is supplied with no drive signal, the voltage between both 
ends of the coil remains the induced voltage (voltage induced under no 
control). 
The voltage induced under no control increases as the clearance between the 
movable member and electromagnetic actuator decreases, and vice versa. It 
is considered that the vibration amplitude of the movable member is 
constant if the vibrator vibrates in the same condition. Therefore, by 
properly selecting the timing of detection of the voltage induced under no 
control, it can be judged that abnormality has occurred. The abnormality 
is decrease in the clearance if the maximum or minimum value of the 
voltage exceeds a threshold, as in the 15th invention. The abnormality is 
increase in the clearance if the value is below the threshold, as in the 
16th invention. 
In the 17th invention, the induced voltage detection means as the state 
detection means must detect any value of the voltage induced under no 
control if the circuit including the exciting coil of the electromagnetic 
actuator is not disconnected, broken or otherwise abnormal. If no such 
voltage is detected, the abnormality judgment means can judge the source 
of control vibration abnormal. 
An eddy current flows in the movable member particularly at a higher 
frequency, so that the impedance of the exciting coil increases. 
Therefore, if the input voltage into the drive circuit for the coil is 
constant, the maximum value of the current flowing actually through the 
coil is determined. The maximum current value, however, tends to lower as 
well if the coil temperature rises and its impedance increases. In the 
18th invention, the maximum current value detection means as the state 
detection means detects the maximum value of the control current flowing 
actually through the coil. This enables the abnormality judgment means to 
judge the electromagnetic actuator, inclusive of the coil, to be hot if 
the maximum value is below the specified threshold. 
In the 19th invention, the control current correction means lowers the 
maximum value of the control current if the abnormality judgment means 
judges the electromagnetic actuator hot. The maximum value is lowered so 
as to either make the actuator out of its hot state, or prevent it from 
being even hotter. 
In the 20th invention, the orifice interconnects the fluid chamber and the 
auxiliary fluid chamber of variable volume. Therefore, in such a condition 
that vibration of a frequency at which the fluid can move through the 
orifice between the chambers is inputted, the apparatus operates as a 
vibro-isolating support of the type filled with fluid which generates 
passive supporting force. Then, for example, if the frequency at which the 
damping of the fluid resonance system with the fluid in the orifice as its 
mass and with the spring in the expanding direction of the elastic body 
and the diaphragm defining the auxiliary fluid chamber as its spring is 
maximum is made substantially equal to the frequency of a particular 
vibration (particularly of large amplitude) generated by the vibrator, 
either there is no need for the electromagnetic actuator to operate, or 
the actuator needs to generate only small controlling force, when the 
particular vibration is generated.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 shows the setup of the first embodiment, which is a control type 
vibro-isolating support applied to an active engine mount 1 for actively 
damping the vibration transmitted from an engine 30 to the car body 
supporting the engine. 
The engine mount 1 as a source of control vibration is generally 
cylindrical and has a vertical axis. The engine mount 1 includes a fitting 
member 2. Fixed to the top of fitting member 2 is a bolt 2a for fitting to 
the engine 30 as a vibrator, which generates periodic vibration. The 
fitting member 2 has a cylindrical wall, an open bottom and a bottom 
flange. Caulked to the periphery of the flange is the top of an inner tube 
3. The fitting member 2 and inner tube 3 define a cylindrical space inside 
them. 
The inner tube 3 surrounds the periphery of a circular diaphragm 4, which 
partitions the cylindrical space into an upper and a lower spaces. The 
periphery of diaphragm 4 is gripped or held under the caulked portions of 
parts 2 and 3. The upper space over the diaphragm 4 opens to the 
atmospheric pressure, while the lower space contains an orifice-defining 
body 5. 
The inner surface of a cylindrical supporting elastic body 6 is bonded by 
curing or vulcanization to the outer surface of inner tube 3. The inner 
surface of the elastic body 6 is positioned axially higher than the outer 
surface of it. The outer surface of the elastic body 6 is bonded by curing 
to the inner surface of an outer tube 7. 
The bottom of outer tube 7 is caulked to the top flange 8A of a cylindrical 
actuator case 8, which is open at the top and closed at the bottom. From 
this bottom projects a bolt 9 for fitting to a support member 35. The case 
8 has a bottom bore 8a, in which the bottom of a cylindrical cap 8b is 
fitted. The head 9a of bolt 9 is located in the bottom space of cap 8b. 
The actuator case 8 also contains an electromagnetic actuator 10 fitted 
coaxially with it. The actuator 10 includes a cylindrical yoke 10A, which 
is fixed to the top of cap 8b, and which has an open top space formed in 
it. An annular exciting coil 10B is fitted in this top space and wound 
with its axis directed vertically. A circular permanent magnet 10C is 
fixed to the top of the portion of yoke 10A which is surrounded by the 
coil 10B. The poles of permanent magnet 10C face upward and downward, 
respectively. An adapter 10a is interposed between the inner surface of 
case 8 and the outer surface of actuator 10 to fix the actuator 10. 
A circular flat spring 11 of metal is fitted over the open top of case 8. 
The periphery 11a of flat spring 11 is gripped together with the flange 8A 
by the caulked bottom of outer tube 7. A magnetic path member 12 in the 
form of a disc is fixed with rivets (not shown) or the like to the lower 
side of the center 11b of flat spring 11. The magnetic path member 11 is 
made of iron or other material which can be magnetized. The magnetic path 
member 12 is spaced with a specified clearance from the top of 
electromagnetic actuator 10. The flat spring center 11b and magnetic path 
member 12 constitute movable members of the invention. 
The lower surface of supporting elastic body 6 and the upper surface of 
flat spring 11 partially define a fluid chamber 15. The diaphragm 4 and 
orifice-defining body 5 define an auxiliary fluid chamber 16. The 
orifice-defining body 5 has orifices 5a formed in it, through which the 
chambers 15 and 16 communicate. The chambers 15 and 16 and orifices 5a are 
filled with oil or other fluid. 
The characteristics of the fluid mount, which depend on the flow passage 
shape etc. of orifices 5a, are adjusted so that the spring constant and 
the damping force are high when an engine shake occurs while the car is 
running, that is to say, when the engine mount 1 is vibrated at 5-15 Hz. 
The exciting coil 10B of electromagnetic actuator 10 is connected through a 
harness (not shown) to a drive circuit 19, which may include an H-type 
bridge circuit. The drive circuit 19 is connected through a harness (not 
shown) to a controller 20. The drive circuit 19 can supply the coil 10B 
with control current I in the direction and of the magnitude in accordance 
with the drive signal y from the controller 20. 
The controller 20 may include a microcomputer, an interface circuit, an A/D 
converter and a D/A converter. The controller 20 can generate a drive 
signal y and supply it to the drive circuit 19 so that, if a vibration is 
inputted which is in the frequency band at which the fluid cannot move 
between the chambers 15 and 16 through the orifices 5a, that is to say, if 
an idle vibration, an internal sound vibration, or an accelerating 
vibration is inputted, which is a vibration higher in frequency than the 
engine shake, a control vibration having the same cycle as that vibration 
is generated in the engine mount 1, and the force of transmitting 
vibration to the support member 35 is "0" (more specifically, the 
controlling force obtained by the electromagnetic force of actuator 10 
cancels the exciting force inputted into the engine mount 1 by the 
vibration on the engine 30 side). 
In a reciprocating 4-cylinder engine, for example, idle vibration, internal 
sound vibration, etc. are caused mainly by the transmission of the engine 
vibration, which is the secondary component of the engine rotation, 
through the engine mount 1 to the support member 35. It is therefore 
possible to reduce the transmissibility of vibration by generating and 
outputting a drive signal y in synchronism with the secondary component of 
the engine rotation. In this embodiment, a pulse signal generator 21 is 
used as a reference signal generation means. This means generates impulse 
signals in synchronism with the rotation of the crank shaft of engine 30 
(in a reciprocating 4-cylinder engine, for example, one impulse signal 
each time the crank shaft has rotated by 180 degrees), and outputs them as 
reference signals x. The controller 20 is supplied with the reference 
signals x as the signals representing the state of the vibration being 
generated by the engine 30. 
Fixed to the support member 35 is an acceleration sensor 22, as a means of 
detecting residual vibration, near where the engine mount 1 is mounted. 
This means detects the state of the vibration of support member 35 in the 
form of acceleration, and outputs it as a residual vibration signal e. The 
controller 20 is supplied with the residual vibration signal e as the 
signal representing the vibration after interference. 
The controller 20 generates and outputs a drive signal y based on the 
reference signals x and residual vibration signal e, in accordance with 
filtered X LMS algorithm, which is a kind of sequentially updated type 
adaptation algorithm, and more specifically, with synchronous filtered X 
LMS algorithm. 
The controller 20 has an adaptive digital filter W with variable filter 
factors W.sub.i (i=0, 1, 2, . . . , I-1, where I is the number of taps). 
The controller 20 outputs as a drive signal y the filter factors W.sub.i 
in order at intervals of specified sampling clock pulses from the point 
when the latest reference signal x is inputted. On the other hand, the 
controller 20 executes the process for properly updating the filter 
factors W.sub.i on the basis of the reference signals x and residual 
vibration signal e, so as to damp the vibration transmitted from the 
engine 30 through the engine mount 1 to the support member 35. 
The updating expression for the adaptive digital filter W is the following 
expression (1) in accordance with the filtered X LMS algorithm. 
EQU W.sub.i (n+1)=W.sub.i (n)-.mu.R.sup.T e(n) (1) 
where the terms with "(n)" represent values at the time n; .mu. is a 
convergence factor related to the stability and the speed of convergence 
of filter factors W.sub.i. Theoretically, R.sup.T is the value (reference 
signal or filtered X signal) of reference signals x filtered by a transfer 
function filter C , which is a model of transfer function C between the 
electromagnetic actuator 10 and acceleration sensor 22. In this 
embodiment, because the reference signals x are a series of impulses as a 
result of the application of synchronous filtered X LMS algorithm, R.sup.T 
equals the sum at the time n of the impulse response waveforms when 
impulse responses of transfer function filter C are generated in 
succession in synchronism with the reference signals x. 
Theoretically, the adaptive digital filter W filters the reference signals 
x to generate a drive signal y. Filtration corresponds to convolution 
operation as digital operation. The reference signals x are a series of 
impulses. Therefore, even if the filter factors W.sub.i of adaptive 
digital filter W are outputted in order as a drive signal y, at intervals 
of specified sampling clock pulses from the point when the latest 
reference signal x is inputted, as stated above, the result is the same 
with the case where the result of filtration is the drive signal y. 
As explained later in detail with flowcharts, the controller 20 processes 
abnormality detection, which judges if the active engine mount is normal 
on the basis of residual vibration signal e. Specifically, in the 
abnormality detection process, the controller 20 stores in each cycle of 
reference signals x, that is to say, when each reference signal x is 
inputted, the maximum value E.sub.max of residual vibration signal e and 
the sampling time i when the maximum value E.sub.max has occurred. Then, 
the controller 20 compares the maximum value E.sub.max with the threshold 
E.sub.th by which the level of residual vibration signal e can be judged 
higher than when the vibration damping control is well executed. If the 
maximum value E.sub.max is larger, the vibration is not damped even though 
the vibration damping control is executed, so that it is judged that the 
engine mount 1 or something may have trouble, degradation or other 
abnormality. If it is judged that there may be such abnormality, then it 
is judged if the maximum values E.sub.max have periodically occurred on 
the basis of the sampling time, which is the time when the maximum values 
E.sub.max have occurred. If periodicity is found, then it is judged that 
something is abnormal. 
If the controller 20 judges that abnormality is occurring, it inhibits the 
execution of the vibration damping control by means of the engine mount 1 
(system down). At the same time, the controller 20 warns the operator of 
the occurrence of trouble, for example, at periodic inspection by turning 
on an alarm lamp 20B (FIG. 2) as alarm raising means. The alarm lamp 20B 
is an LED lamp, which is fitted on a side wall of case 20A of controller 
20. 
The operation of this embodiment is explained below. 
When an engine shake occurs, the engine mount 1 functions as a support of a 
high dynamic spring constant and high damping force, as a result of the 
proper selection of the flow passage shape etc. of orifices 5a. Therefore, 
the engine mount 1 damps the engine shake generated at the engine 30, 
thereby lowering the vibration level on the support member 35 side. In 
such a case, it is not particularly necessary to displace the magnetic 
path member 12. 
If a vibration is inputted which has a frequency higher than the idle 
vibration frequency, at which the fluid in the orifices 5a is in a stick 
state and no fluid can move between the chambers 15 and 16, the controller 
20 processes a specified operation, outputs a drive signal y to the 
electromagnetic actuator 10, and makes the engine mount 1 generate an 
active controlling force, which can damp the vibration. 
This is explained below in detail with reference to FIG. 3, which is a 
flowchart schematically showing the process executed in the controller 20 
when an idle vibration or an internal sound vibration is inputted. 
At step 101, specified initialization is made. Thereafter, the process goes 
to step 102, where the reference signal R.sup.T for one cycle is computed 
in a lump on the basis of transfer function filter C . 
Then, the process goes to step 103, where the count i of a counter is 
zeroed or cleared, and thereafter to step 104, where the ith filter factor 
W.sub.i of adaptive digital filter W is outputted as a drive signal y. 
After the drive signal y is outputted at step 104, the process goes to step 
105, where the residual vibration signal e is read and stored together 
with the present value of count i. 
Next, the process goes to step 106, where the count j of a counter is 
zeroed, and then to step 107, where the jth filter factor W.sub.j is 
updated in accordance with the expression (1). 
After completing the updating at step 107, the process goes to step 108, 
where it is judged if the next reference signal x has been inputted. If 
not, the process goes to step 109 for updating the next filter factor of 
adaptive digital filter W or outputting a drive signal y. 
At step 109, it is judged if the count j exceeds the number of output times 
T.sub.y (precisely, T.sub.y minus 1 because the count j starts with 0). 
This judgment is for judging if the required number of filter factors 
W.sub.i of adaptive digital filter W have been updated as the drive signal 
y after the filter factor W.sub.i was outputted as the drive signal y at 
step 104. If the judgment at step 109 results in no, the count j is 
incremented at step 110. Then, the process returns to step 107 for 
repetition of steps. 
If the judgment at step 109 results in yes, it can be judged that the 
required number of filter factors of adaptive digital filter W as the 
drive signal y have been updated. Then, the process goes to step 111, 
where the count i is incremented. Thereafter, the process waits until the 
time has passed which corresponds to the interval of the specified 
sampling clock pulses after the last processing at step 104. If the time 
has passed, the process returns to step 104 for repetition of steps. 
If it is judged at step 108 that the reference signal x has been inputted, 
the process goes to step 112, where the count i (precisely, i plus 1 
because the count i starts with 0) is stored as the latest number of 
output times T.sub.y. Thereafter, the process returns to step 102 for 
repetition of steps. 
As a result of the repetition of steps in FIG. 3, the controller 20 
supplies the drive circuit 19 with the filter factors W.sub.i of adaptive 
digital filter W in order as the drive signal y at intervals of the 
sampling clock pulses from the point when the reference signal x is 
inputted, as shown in FIG. 4, which shows the relations between the 
reference signals x, drive signal y and transfer function filter C . 
As a result, the drive circuit 19 makes the exciting coil 10B generate a 
magnetic force in proportion to the drive signal y. Because a constant 
magnetic force is already applied by the permanent magnet 10C to the 
magnetic path member 12, it can be considered that the magnetic force of 
the coil 10B acts to strengthen or weaken the magnetic force of permanent 
magnet 10C. In other words, when no drive signal y is supplied to the coil 
10B, the magnetic path member 12 is displaced to the neutral position, 
where the supporting force of flat spring 11 and the magnetic force of 
permanent magnet 10C balance with each other. When the coil 10B is 
supplied with a drive signal y in the neutral condition, and if this 
signal makes the coil 10B generate a magnetic force in the opposite 
direction to that of permanent magnet 10C, the magnetic path member 12 is 
displaced so as to enlarge the clearance between it and the 
electromagnetic actuator 10. Contrariwise, if the magnetic forces of the 
coil 10B and permanent magnet 10C are in the same direction, the magnetic 
path member 12 is displaced so as to reduce the clearance between it and 
the actuator 10. 
Thus, the magnetic path member 12 can be displaced in opposite directions. 
The displacement changes the volume of main fluid chamber 15. The change 
of volume deforms the expansion spring of the elastic body 6. This makes 
the engine mount 1 generate active supporting force in either direction. 
Each filter factor W.sub.i of adaptive digital filter W as a drive signal 
y is sequentially updated with the expression (1) in accordance with the 
synchronous filtered X LMS algorithm. Therefore, after the filter factors 
W.sub.i converge at the optimum value when some time has passed, the 
supply of drive signal y to the engine mount 1 damps the idle vibration, 
the internal sound vibration or the like transmitted from the engine 30 
through the engine mount 1 to the support member 35. 
The abnormality detection process is explained below with reference to the 
flowchart of FIG. 5. The process of FIG. 5 is executed as an interrupt 
process each time the step 112 of the vibration damping process of FIG. 3 
is completed. 
First at step 201, the maximum value E.sub.max is selected from the 
residual vibration signal e in one cycle of reference signals x, which is 
stored in the process of FIG. 3, and then the maximum value E.sub.max and 
the sampling time i at which it has occurred are stored as E.sub.max (k) 
and i(k), respectively, corresponding to the variable k which represents 
the number of the times when the process of FIG. 5 is executed. 
Next, the process goes to step 202, where it is judged if the threshold 
E.sub.th is exceeded by the maximum value E.sub.max (k) obtained at step 
201. If the judgment results in no, the level of residual vibration signal 
e is low. It is therefore considered that, as a result of the vibration 
damping process of FIG. 3 sufficiently damping the vibration transmitted 
from the engine 30 to the support member 35, a residual vibration signal e 
as shown in FIG. 6 is obtained. It is therefore judged that no abnormality 
is occurring. Then, the process goes to step 203, where the count of a 
counter FALE is zeroed, which shows if there is abnormality. Thereafter, 
the abnormality detection process for this time ends. 
If the judgment at step 202 results in yes, the level of residual vibration 
signal e is high. It can therefore be judged that, because the vibration 
on the support member 35 side is not sufficiently damped, the vibration 
damping control may not be normally working, that is to say, abnormality 
may be occurring. 
Then, the process goes to step 204, where it is judged if the count of 
counter FALE is 0. If the count is 0, the maximum value E.sub.max exceeds 
the threshold E.sub.th for the first time. Because it is therefore not 
possible at this stage to judge if there is abnormality, the process goes 
to step 205, where the count of counter FALE is made 1. Thereafter, the 
abnormality detection process for this time ends. 
In the subsequent abnormality detection processes, if the judgment at step 
202 still results in yes, the judgment at step 204 results in no. Then, 
the process goes to step 206, where it is judged if the maximum values 
E.sub.max have periodically occurred. Particularly in this embodiment, it 
is judged if the maximum values E.sub.max have occurred at the same cycle 
as the reference signals x. 
Specifically at step 206, it is judged if the sampling time i(k) stored at 
step 201 is identical with the sampling time i(k-1) also stored in the 
process for the last time. If the judgment at step 206 results in yes, it 
can be judged that a residual vibration signal e of a certain level has 
the same periodicity as the reference signals x, as shown in FIG. 7, for 
example. 
Contrariwise, if the judgment at step 206 results in no, it is certain that 
the level of residual vibration signal e is high, but it can be judged 
that there is no relation between the residual vibration signal e and 
reference signals x. This is true of such a case that, although the active 
engine mount is normal, the vibration inputted from the road surface to 
the support member 35 is detected by the acceleration sensor 22, and 
superimposed on the residual vibration signal e because, for example, the 
vehicle is running on a bad road or the like. In this case, the residual 
vibration signal e is such as shown in FIG. 8. 
If the judgment at step 206 results in no, the process goes to step 203, 
where the counter FALE is zeroed. Thereafter, the abnormality detection 
process for this time ends. 
If the judgment at step 206 results in yes, however, the residual vibration 
signal e and reference signals x probably have relation to each other. 
Then, the process goes to step 207, where the counter FALE is incremented. 
Next, the process goes to step 208, where it is judged if the count of 
counter FALE exceeds a specified number .beta., which may be 10, for 
example. If not, the abnormality detection process for this time ends as 
it is. 
As stated above, it is not judged that abnormality is occurring immediately 
if the judgment at step 206 results in yes, because the abnormality 
detection process is made more reliable by avoiding the misjudgment that 
there is abnormality in such a case that the cycles of residual vibration 
signal e and reference signals x coincide accidentally. 
Therefore, if the judgment at step 208 results in yes, it can be judged 
that the residual vibration signal e is periodic, and yet that its cycle 
coincides with the cycle of reference signals x. In such a case, although 
the vibration damping process of FIG. 3 is in execution, the vibration 
transmitted from the engine 30 through the engine mount 1 to the support 
member 35 is not sufficiently damped. It can therefore be judged that the 
engine mount 1 or something is abnormal. Then, the process goes to step 
209, where the execution of the vibration damping process of FIG. 3 is 
inhibited to make the system down, and the alarm lamp 20B is turned on. 
As a result, the operation of an active engine mount which is abnormal is 
avoided. This can avoid wrong operation which may cause worse vibration 
etc., so that the influence of the abnormality is minimum. With the 
function for thus judging if abnormality is occurring, it is possible to 
raise the reliability of the apparatus when the apparatus is actually 
used, without needing to use very durable and/or very expensive members or 
parts for avoiding possible abnormality. 
If it is judged that abnormality is occurring, the alarm lamp 20B is turned 
on. If the controller 20 is located where the operator can see the alarm 
lamp 20B, he/she can immediately be warned of the abnormality. Even if the 
controller 20 is located where the operator cannot see the alarm lamp 20B, 
he/she can easily and certainly be informed at regular inspection etc. 
that the active engine mount is abnormal. It is thus possible to minimize 
the possibility that the abnormality is overlooked. 
In this embodiment, it is possible to judge if there is abnormality on the 
basis of the state of residual vibration signal e. Therefore, there is no 
need of a new sensor other than the sensor necessary for damping 
vibration. This means that the costs are not greatly increase and the 
apparatus is not enlarged. The apparatus not enlarged is very desirable 
for a vehicle with a very limited mounting space. 
The abnormality judgment process basically requires only the steps of 
finding a maximum value E.sub.max of residual vibration signal e by means 
such as simple subtraction, comparing the maximum value E.sub.max with the 
threshold E.sub.th, comparing the sampling time i(k) with the sampling 
time i(k-1), incrementing the count of counter E and comparing it with 
the specified value .beta.. This does not largely increase the operation 
load on the controller 20. Therefore, there is no need to use a 
microprocessor or the like for high speed operation, which is expensive, 
in order to realize the functions of this embodiment. 
In this embodiment, it is judged if the maximum value E.sub.max exceeds the 
threshold E.sub.th. If so, it is judged if the newest sampling time i(k) 
is identical with the last sampling time i(k-1). If it keeps judged for a 
certain time that i(k) and i(k-1) are identical, it is judged that 
abnormality is occurring. It is therefore possible to precisely judge how 
the engine vibration is transmitted to the support member 35 side, even 
though the vibration damping process is executed. In short, the 
possibility of false or wrong detection of abnormality is very low. 
In this embodiment, it is judged if there is abnormality on the basis of 
maximum values E.sub.max of residual vibration signal e. As shown in FIG. 
7, however, if the residual vibration signal e alternates in opposite 
directions, the judgment may be based on the minimum values instead of the 
maximum values. 
In this embodiment, the process shown in FIG. 3 constitutes control means. 
The process of storing the residual vibration signal e and the sampling 
time i at step 105 and the processing at step 201 constitute 
maximum/minimum value detection means as state detection means. The 
processing at steps 202-208 constitutes abnormality detection means. 
FIG. 9 is a flowchart of an abnormality detection process similar to FIG. 5 
of the first embodiment, but showing the second embodiment. Similarly to 
the first embodiment, this embodiment is a control type vibro-isolating 
support applied to an active engine mount. Because this embodiment has 
substantially the same setup except for the abnormality detection process 
as the first embodiment, the illustration and explanation of same are 
omitted. 
Similarly to the first embodiment, it is judged if there is abnormality on 
the basis of residual vibration signal e. This embodiment differs, 
however, in that it is judged if abnormality is occurring on the basis of 
the auto-correlation function of residual vibration signal e. 
If the abnormality detection process of this embodiment is started, it goes 
to the first step 301. At step 301, the auto-correlation function 
.gamma.(.tau.) of residual vibration signal e stored at step 105 of the 
vibration damping process shown in FIG. 3 is computed. In computing the 
auto-correlation function .gamma.(.tau.), the time lag .tau. is the period 
of reference signals x. Specifically, because the number of output times 
T.sub.y stored at step 112 of FIG. 3 represents the number of sampling 
times in one cycle of reference signals x, the time lag t may be T.sub.y 
(.tau.=T.sub.y). 
Accordingly, the operation expression for the auto-correlation function 
.gamma.(.tau.) is the following expression (2) 
##EQU1## 
Step 301 for finding the auto-correlation function .gamma. (.tau.) is 
followed by step 302. At step 302, it is judged if the auto-correlation 
function .gamma.(.tau.) exceeds the threshold .gamma..sub.th by which the 
level of residual vibration signal e can be judged higher than a value 
when the vibration damping control is well executed. That is to say, in 
this embodiment, because the time lag .tau. of auto-correlation function 
.gamma.(.tau.) equals the number of output times T.sub.y, which is the 
period of reference signals x, the auto-correlation function 
.gamma.(.tau.) computed with the expression (2) is large if the residual 
vibration signal e is periodic in synchronism with the reference signals 
x, and if the level of residual vibration signal e is high. 
The cycle of reference signals x is nothing but the cycle of the engine 
vibration. If the auto-correlation function .gamma.(.tau.) is large, the 
engine vibration is transmitted to the support member 35 side even though 
the vibration damping control is executed. In such a case, the engine 
mount 1 or something may probably be abnormal. 
If the judgment at step 302 results in no, the process goes to step 303, 
where the counter FALE is zeroed. Thereafter, the abnormality detection 
process for this time ends. If the judgment at step 302 results in yes, 
the process goes to step 304, where the counter FALE is incremented. Next 
at step 305, it is judged if the count of counter FALE exceeds the 
specified value .beta.. 
If the judgment at step 305 results in no, the abnormality detection 
process ends as it is. If yes, the process goes to step 306, where the 
execution of the vibration damping process of FIG. 3 is inhibited to make 
the system down, and the alarm lamp 20B is turned on. If the judgment at 
step 302 results in yes, the process does not immediately go to step 306, 
in order to avoid falsely judging that abnormality is occurring when the 
auto-correlation function .gamma.(.tau.) accidentally increases. This 
makes the abnormality detection process more reliable. 
Thus, in this embodiment as well as the first embodiment, it can be judged 
if there is abnormality on the basis of residual vibration signal e. It is 
therefore possible, similarly to the first embodiment, to avoid the 
operation of an active engine mount which is abnormal. It is also possible 
to avoid false operation which may cause worse vibration or the like. It 
is thus possible to minimize the influence of abnormality. 
With the setup of this embodiment, there is no need to find maximum values 
of residual vibration signal e. As apparent by comparing FIGS. 5 and 9, 
the process of this embodiment is simple as a whole. It is therefore 
possible to make the operation load less than in the first embodiment. 
This embodiment has other advantages similar to those of the first 
embodiment. 
In computing the auto-correlation function .gamma.(.tau.) in this 
embodiment, the time lag .tau. equals the number of output times T.sub.y. 
Because the vibration generated by the engine 30 is periodic, however, the 
time lag .tau. may be an integral number of times (as large as) the number 
of output times T.sub.y (.tau.=2T.sub.y, 3T.sub.y, . . . ). 
In this embodiment, the processing at step 301 constitutes auto-correlation 
function operation means, while the processing at steps 302-305 
constitutes abnormality judgment means. 
FIG. 10 is a flowchart of an abnormality detection process similar to FIG. 
5 of the first embodiment, but showing the third embodiment. Similarly to 
the first embodiment, this embodiment is a control type vibro-isolating 
support applied to an active engine mount. Because this embodiment has 
substantially the same setup except for the abnormality detection process 
as the first embodiment, the illustration and explanation of same are 
omitted. 
This embodiment is characterized in that it is judged if there is 
abnormality on the basis of the cross-correlation function of drive signal 
y and residual vibration signal e. In other words, if the vibration 
damping control is well executed, a periodic drive signal y is outputted 
in synchronism with the reference signals x, while a residual vibration 
signal e of a low level must be detected, as shown in FIG. 11, for 
example. The reason is that the vibration on the engine 30 side in 
synchronism with the reference signals x is canceled by the control 
vibration generated by the engine mount 1 in accordance with the drive 
signal y. Accordingly, the component of residual vibration signal e which 
is synchronous with the reference signal x must be small. In this case, as 
shown in FIG. 12, the cross-correlation function .epsilon.(.tau.) of drive 
signal y and residual vibration signal e must be sufficiently small. 
By contrast, if the vibration on the engine 30 side is transmitted to the 
support member 35 side because of trouble, degradation or other 
abnormality, even though the vibration damping control is executed, a 
drive signal y is outputted in synchronism with the reference signals x, 
while a residual vibration signal e must be detected, as shown in FIG. 13. 
The component of residual vibration signal e which is synchronous with the 
reference signals x has not been reduced. Therefore in this case, as shown 
in FIG. 14, the cross-correlation function .epsilon.(.tau.) of drive 
signal y and residual vibration signal e has a peak value larger than the 
threshold .epsilon..sub.th by which the level of residual vibration signal 
e can be judged higher than a value when the vibration damping control is 
well executed. 
From the above, it can be judged if there is abnormality on the basis of 
cross-correlation function .epsilon.(.tau.). 
If the abnormality detection process of this embodiment is started, it goes 
to the first step 401. At step 401, the cross-correlation function 
.epsilon.(.tau.) of drive signal y outputted at step 104 of the vibration 
damping process of FIG. 3 and residual vibration signal e stored at step 
105 is computed. The time lag .tau. ranges between zero and the number of 
output times T.sub.y, which is the period of reference signals x(.tau.=0 
to T.sub.y). The operation expression for the cross-correlation function 
.epsilon.(.tau.) is the following expression (3). 
##EQU2## 
Step 401 for finding the cross-correlation function .epsilon.(.tau.) is 
followed by step 402. At step 402, it is counted how many peak values of 
cross-correlation function .epsilon.(.tau.) which exceed the threshold 
.epsilon..sub.th exist within the range of .tau.=0 to T.sub.y, and where 
the result of count is stored as a number CF. 
Next, the process goes to step 403, where it is judged if the number CF is 
1 or more, that is to say, whether or not there is at least one peak value 
of cross-correlation function .epsilon.(.tau.) which exceeds the threshold 
.epsilon..sub.th. If not, the process goes to step 404, where the counter 
FALE is cleared. Thereafter, the abnormality detection process for this 
time ends. If yes, the process goes to step 405, where the counter FALE is 
incremented. Next at step 406, it is judged if the count of counter FALE 
exceeds the specified value .beta.. 
If the judgment at step 406 results in no, the abnormality detection 
process for this time ends as it is. If yes, the process goes to step 407, 
where it is judged if the number CF is 1. 
If it is judged at step 407 that CF is one (CF=1), as shown in FIG. 13, 
there exists a residual vibration signal e having a strong component in 
synchronism with the reference signals x. It can therefore be judged that 
there is abnormality. Then, the process goes to step 408, where the 
execution of the vibration damping process of FIG. 3 is inhibited to make 
the system down, and the alarm lamp 20B is turned on. 
If the judgment at step 407 results in no, higher-order 
(multiple-frequency) divergence is occurring, where higher-order 
components of reference signals x exist in the drive signal y and residual 
vibration signal e, as shown in FIG. 15, for example. In such a case, the 
cross-correlation function .epsilon.(.tau.) of drive signal y and residual 
vibration signal e has a plurality of (two in this case) peak values, as 
shown in FIG. 16. 
The higher-order divergence is the divergence resulting from gradual growth 
of the higher-order components of reference signals x which exist in the 
adaptive digital filter W by the influence of the vibration or the like 
inputted from something but the engine 30. It can be considered that the 
higher-order divergence is not yet an essentially abnormal state. 
In this embodiment, if the judgment at step 407 results in no, the process 
goes to step 409, where the filter factor W.sub.j of adaptive digital 
filter W is reset. Next at step 404, the counter FALE is cleared. 
Thereafter, the process returns to the process of FIG. 3. As a result, the 
vibration damping control is executed again with the higher-order 
divergence securely eliminated. 
If the judgment at step 403 results in yes, the process does not 
immediately go to step 407, in order to avoid falsely judging that there 
is abnormality when the cross-correlation function .epsilon.(.tau.) is 
accidentally large. This makes the abnormality detection process more 
reliable. 
Thus, with the setup of this embodiment, it can be judged if there is 
abnormality on the basis of cross-correlation function .epsilon.(.tau.). 
It is therefore possible to avoid the operation of an active engine mount 
which is abnormal similarly to the first embodiment. It is also possible 
to avoid false operation which may cause worse vibration or the like. It 
is thus possible to minimize the influence of abnormality. 
With the setup of this embodiment, it is possible to judge higher-order 
divergence, which is slight abnormality. If there is such divergence, it 
is possible to eliminate the abnormality and execute the vibration damping 
control without needing to make the system down. It is therefore possible 
to continue the vibration damping control longer. 
Even if the disturbance vibration generated by something but the engine 30 
(for example, inputted from the road surface side) is transmitted to the 
support member 35, the cross-correlation function itself does not change. 
It is therefore easy to detect only abnormality. Other advantages are 
similar to those in the first embodiment. 
In this embodiment, the processing at step 401 constitutes 
cross-correlation function operation means as state detection means. The 
processing at steps 402-407 constitute abnormality judgment means. 
FIGS. 17-21 show the fourth embodiment, which is a control type 
vibro-isolating support applied to an active engine mount similarly to the 
first embodiment. 
FIG. 17 is a circuit diagram showing the connection between the controller 
20 and the drive circuit 19 for the exciting coil 10B. The drive circuit 
19 and the coil 10B are interconnected through a resistor 25 for current 
detection, which is interposed between one terminal of the coil 10B and 
the drive circuit 19. The controller 20 is supplied with the voltage 
V.sub.1 at the other terminal of the coil 10B and the voltages V.sub.2 and 
V.sub.3 at both terminals of resistor 25. The controller 20 reads the 
voltages V.sub.1, V.sub.2 and V.sub.3 through an A/D converter (not shown) 
etc. 
The abnormality detection process of this embodiment includes the first 
abnormality detection process immediately after the vehicle ignition 
switch is turned on, but before the vibration damping process of FIG. 3, 
and the second abnormality detection process as an interrupt process 
during the vibration damping process similarly to the first and other 
embodiments. The first abnormality detection process is for detection of 
trouble and degradation of engine mount 1. The second abnormality 
detection process is for detection of a hot state of electromagnetic 
actuator 10. 
First, the first abnormality detection process is explained below. 
Immediately after the ignition switch is turned on, though vibration is 
inputted from the engine 30 into the engine mount 1, the vibration damping 
control is not executed. Therefore, the magnetic path member 12 is not 
positively displaced by the output of electromagnetic actuator 10. If the 
vibration is inputted from the engine 30 into the engine mount 1, however, 
the elastic body 6 elastically deforms, changing the volume of fluid 
chamber 15. The volume change is transmitted through the flat spring 11 
and displaces the magnetic path member 12. 
The displacement of magnetic path member 12, which is made of magnetizable 
material, induces a voltage between both terminals of exciting coil 10B. 
If the induced voltage (voltage induced under no control) is found, it can 
be judged that there is no disconnection or the like in at least the coil 
10B. Contrariwise, if the voltage induced under no control is not found, 
it can be judged that the coil 10B is disconnected or otherwise abnormal. 
If the clearance between the electromagnetic actuator 10 and magnetic path 
member 12 varies in size, the magnitude of the voltage induced under no 
control changes. Therefore, on the basis of this voltage, it is possible 
to acknowledge the clearance between the actuator 10 and the member 12. 
Specifically, as shown in FIG. 18, where the abscissa represents the 
clearance between the electromagnetic actuator 10 and magnetic path member 
12, while the ordinate represents the voltage induced in the exciting coil 
10B, the induced voltage tends to be more steeply high as the clearance 
becomes smaller. For example, at its position where the clearance is 
comparatively large, the member 12 is displaced within a range C1, 
inducing voltage within a range D1. At its other position where the 
clearance is comparatively small, it is displaced within a range C2, 
inducing voltage within a range D2. If the displacement ranges C1 and C2 
are the same, the voltage range D1 is smaller than D2. Therefore, on the 
basis of the maximum or minimum values, the amplitude ranges or the like 
of the induced voltages, it is possible to detect the state of the 
clearance between the actuator 10 and the member 12. 
If the first abnormality detection process shown in FIG. 19 is started 
immediately after the ignition switch is turned on, but before the 
vibration damping control shown in FIG. 3 is executed, it goes to the 
first step 501. At step 501, the voltages V.sub.1 and V.sub.3 induced at 
both terminals of exciting coil 10B are read. Next at step 502, the 
voltage V.sub.0 induced under no control is found. The voltage V.sub.0 is 
the finite difference between the read voltages V.sub.1 and V.sub.3 
(V.sub.0 =.vertline.V.sub.1 -V.sub.3 .vertline.). Next at step 503, it is 
judged if a specified time, which may be 1 second, for example, has passed 
after the process of FIG. 19 was started. Until the specified time has 
passed, steps 501 and 502 are repeated. 
If the judgment at step 503 results in yes, the process goes to step 504, 
where the maximum value of the voltages V.sub.0 found at step 502 is 
selected and stored as V.sub.max. Otherwise, the maximum value V.sub.max 
may be selected by adding to step 502 a process for leaving the latest 
maximum voltage V.sub.0. 
Step 504 for finding the maximum value V.sub.max is followed by step 505, 
where it is judged if this value is zero (V.sub.max =0). If it is judged 
that the value is zero, voltage has not been induced at the exciting coil 
10B, even though it should have been, or any voltage induced there has not 
been detected or found as terminal voltage. It can therefore be judged 
that there is occurring such abnormality that the fluid in the fluid 
chamber 15 is leaking out, so that the volume of the chamber 15 does not 
change even though the elastic body 6 deforms, or such trouble that the 
coil 10B is disconnected. 
If the judgment at step 505 results in yes, the process goes to step 506, 
where the execution of the vibration damping process of FIG. 3 is 
inhibited to make the system down, and the alarm lamp 20B is turned on. 
If the judgment at step 505 results in no, it can be judged that at least 
such abnormality as mentioned above is not occurring. Then, the process 
goes to step 507 for judging if other abnormality or degradation is not 
occurring. 
At step 507, it is judged if a specified value .delta..sub.1 is exceeded by 
the finite difference .DELTA..sub.1 between the maximum value V.sub.max 
and a specified value V.sub.th (.DELTA..sub.1 =.vertline.V.sub.max 
-V.sub.th .vertline.). The value V.sub.th is the maximum value of the 
voltages induced under no control when the clearance between the 
electromagnetic actuator 10 and magnetic path member 12 is a proper value. 
The specified value .delta..sub.1 is a value by which it can be judged if 
the clearance between the actuator 10 and the member 12 greatly differs 
from a proper value. The value .delta..sub.1 can be found experimentally 
with an actual engine mount. 
Therefore, if the judgment at step 507 results in yes, it may be considered 
that the magnetic path member 12 has greatly approached the 
electromagnetic actuator 10 away from its initial position, because the 
flat spring 11 supporting the member 12 has stretched due to its repeated 
deformation, or that the neutral position of the member 12 has moved far 
away from the actuator 10, because the permanent magnet 10C has been 
demagnetized by something. In any case, this is an abnormal condition, 
where the engine mount 1 cannot operate normally. If the judgment at step 
507 results in yes, the process proceeds toward step 506. Before step 506, 
however, the process goes to step 508, where it is judged if the maximum 
value V.sub.max exceeds the specified value V.sub.th. 
Step 508 is a process for confirming whether the abnormality is decrease or 
increase in the clearance between the electromagnetic actuator 10 and 
magnetic path member 12, and storing the confirmed direction of 
abnormality in the storage region of controller 20 from which read can be 
made, for later analysis of trouble. As already explained with reference 
to FIG. 18, the induced voltage becomes higher as the clearance becomes 
narrower. Therefore, if the judgment at step 508 results in yes, it can be 
judged that the clearance is narrower. Then, the process goes to step 509, 
where it is stored that the abnormality is decrease in the clearance. If 
the judgment at step 508 results in no, it can be judged that the 
clearance is wider. Then, the process goes to step 510, where it is stored 
that the abnormality is increase in the clearance. Steps 509 and 510 are 
followed by step 506, where the execution of the vibration damping process 
of FIG. 3 is inhibited to make the system down, and the alarm lamp 20B is 
turned on. 
If the judgment at step 507 results in no, there is no such abnormality 
that the clearance has extremely varied, but there may be such degradation 
that the clearance has varied. Then, the process goes to step 511, where 
it is judged if the finite difference .DELTA..sub.1 exceeds a specified 
value .delta..sub.2, which is smaller than the specified value 
.delta..sub.1. .delta..sub.2 is a value by which it can be judged if the 
clearance between the electromagnetic actuator 10 and magnetic path member 
12 is so different from a proper value as to somewhat affect the vibration 
damping control. Similarly to .delta..sub.1, .delta..sub.2 can be found 
experimentally with an actual engine mount. 
If the judgment at step 511 results in no, it can be judged that the 
clearance is kept a proper value. This means that no particular 
degradation could be acknowledged. Then, the first abnormality detection 
process ends as it is, and is followed by the vibration damping process of 
FIG. 3. 
If the judgment at step 511 results in yes, it can be judged that the 
clearance has not reached an abnormal level, but has varied to such a 
degree as to somewhat affect the vibration damping control. Then, the 
process proceeds through steps 512 and 513 or 514 to step 515. The process 
of steps 512-514 is similar to that of steps 508-510. At step 515, the 
alarm lamp is turned on (or blinked for distinction from abnormality) 
without making the system down. The driver or the operator making periodic 
inspection can thus be warned that there is degradation. Thereafter, the 
first abnormality detection process ends, and is followed by the vibration 
damping process of FIG. 3. 
The second abnormality detection process is explained below. When high 
frequency current drives the exciting coil 10B of electromagnetic actuator 
10, which is used as a driving source in the engine mount 1, an eddy 
current flows in the magnetic path member 12, so that the impedance of the 
coil 10B becomes high. The frequency of the current flowing through the 
coil 10B depends on the rotating speed of engine 30. Accordingly, if the 
input voltage is constant, the maximum value of the current flowing 
through the coil 10B is definite. Also, if the temperature of the coil 10B 
rises, increasing its impedance, the maximum value of the current flowing 
through the coil 10B tends to lower. 
It is therefore possible to judge if the electromagnetic actuator 10 
including the exciting coil 10B is hot, by detecting the maximum value of 
the current flowing actually through the coil 10B, and comparing this 
value with a threshold, which is the theoretically maximum current value 
determined by the engine speed. 
The second abnormality detection process shown in FIG. 20 is executed as an 
interrupt process immediately after step 112 of the vibration damping 
control shown in FIG. 3. First at step 601, the engine speed N (rpm) is 
found on the basis of the number of output times T.sub.y, which is the 
period of reference signals x, and the sampling time. Next at step 602, it 
is judged if the engine speed N exceeds a specified value N.sub.0, which 
may be 3,000 (rpm), for example. The value N.sub.0 is used to judge if the 
engine speed N is so high that the eddy current flowing in the magnetic 
path member 12 affects the impedance of exciting coil 10B. 
If the judgment at step 602 results in no, it can be judged that the 
electromagnetic actuator 10 is not made particularly hot. Then, the 
process goes to step 603, where the limit value I.sub.L which is the 
maximum value of the control current I used in the vibration damping 
process explained later is adjusted to a normal value. Thereafter, the 
second abnormality detection process for this time ends. 
If the judgment at step 602 results in yes, the process goes to step 604, 
where the voltages V.sub.2 and V.sub.3 at both terminals of the resistor 
25 shown in FIG. 17 are read. Next at step 605, the control current 
I.sub.0 actually flowing through the exciting coil 10B is computed on the 
basis of the voltages V.sub.2 and V.sub.3 and the resistance R.sub.1 of 
resistor 25 (I.sub.0 =.vertline.V.sub.2 -V.sub.3 .vertline./R.sub.1), and 
then the maximum value I.sub.max of control current I.sub.0 is found. 
Actually, the control current I.sub.0 varies sinusoidally like the drive 
signal y. Accordingly, in order to find the maximum value I.sub.max, there 
is a need to detect the control current I.sub.0 for the time corresponding 
to at least half the period of drive signal y. It is therefore desirable 
to execute steps 604 and 605 constantly following the step 111 of FIG. 3, 
for example. 
Step 605 for finding the maximum value I.sub.max is followed by step 606, 
where it is judged if this value I.sub.max exceeds a threshold I.sub.th. 
I.sub.th is a value somewhat (about 10%, for example) smaller than the 
maximum value of the current which can flow when the electromagnetic 
actuator 10 is not hot. The threshold I.sub.th depends on the engine speed 
N as shown below in Table 1, for example. 
TABLE 1 
______________________________________ 
(rpm) 
.about.3200 
.about.3400 
.about.3600 
.about.3800 
.about.4000 
.about.4200 
.about.4400 
______________________________________ 
V.sub.th 
3.2 3.1 3.0 2.9 2.9 3.0 2.9 
______________________________________ 
If the judgment at step 606 results in yes, sufficiently large control 
current I is flowing. It can therefore be judged that the impedance of 
exciting coil 10B is not very high, that is to say, the electromagnetic 
actuator 10 is not hot. Then, after going through step 603, the second 
abnormality detection process for this time ends. 
If the judgment at step 606 results in no, it is not possible for the 
control current I to increase. It can therefore be judged that the 
impedance of the coil 10B is high, that is to say, the actuator 10 is hot. 
Then, the process goes to step 607, where the limit value I.sub.L is 
adjusted to a value at high temperature, which is smaller than the normal 
value set at step 603. Thereafter, the second abnormality detection 
process for this time ends. 
The vibration damping process in this embodiment is basically that shown in 
FIG. 3 similarly to the first and other embodiments. As shown in FIG. 21, 
however, this process includes, between steps 109 and 111, another step 
113 for correcting the filter factor W.sub.j of adaptive digital filter W. 
Specifically, at step 113, each filter factor W.sub.j outputted as a drive 
signal y is corrected so as to decrease at a constant rate, in order for 
the maximum value of control current I not to exceed the limit value 
I.sub.L, on the basis of the relation between the drive signal y and 
control current I. 
Thus, immediately after the engine 30 is started, the first abnormality 
detection process shown in FIG. 19 is executed. During the vibration 
damping process, the second abnormality detection process shown in FIG. 20 
is executed. 
By executing the first abnormality detection process, it is possible to 
detect disconnection in the engine mount 1 and abnormal or degraded 
clearance between the electromagnetic actuator 10 and magnetic path member 
12. Thereagainst, proper steps are taken. Therefore, similarly to the 
first and other embodiments, it is possible to avoid the operation of an 
active engine mount which is abnormal. It is also possible to avoid false 
operation which may cause worse vibration or the like. It is thus possible 
to minimize the influence of abnormality. 
In accordance with the first abnormality detection process, it can be 
detected or judged, without needing a new sensor etc., whether there is 
disconnection or not, whether the clearance between the electromagnetic 
actuator 10 and magnetic path member 12 has varied or not, and whether 
such variation, if any, is large or small. Because the operation process 
is not particularly complex, the costs will not greatly increase and the 
apparatus will not be enlarged. This is, similarly to the first 
embodiment, very desirable for a vehicle with a greatly limited mounting 
space. 
In accordance with the second abnormality detection process, it can be 
detected if the electromagnetic actuator 10 is hot. If a high temperature 
condition is detected, the limit value I.sub.L is adjusted at step 607 so 
as to be smaller than normal. This positively lowers the maximum value of 
control current I when the vibration damping process is executed. 
Accordingly, the high temperature condition of the actuator 10 is 
prevented from being worse or is normalized. It is therefore possible to 
avoid abnormality occurring in the actuator 10 due to high temperature. If 
the high temperature condition of the actuator 10 is eliminated, and the 
judgment at step 606 results in yes again, the process of step 603 is 
executed to restore the normal control condition. Therefore, the maximum 
value of control current I is limited during the minimum time required. In 
other words, it is possible to minimize the drop in vibration damping 
effect due to the limitation of the maximum value of control current I. 
When the first abnormality detection process is executed, the clearance 
variation is judged on the basis of the maximum value V.sub.max of voltage 
V.sub.0 induced under no control and the specified value V.sub.th, which 
is the maximum value of the voltage induced under no control when the 
clearance is a proper value. Otherwise, the clearance variation may be 
judged on the basis of the minimum value of the voltage V.sub.0 and the 
minimum value of the voltage induced under no control when the clearance 
is a proper value. 
In this embodiment, the processing at steps 501-504 constitutes clearance 
detection means and induced voltage detection means as state detection 
means. The processing at steps 604 and 605 constitutes maximum current 
value detection means. The processing at steps 607 and 113 constitutes 
control current correction means. The processing at step 505, the 
processing at steps 507-514 and the processing at step 606 constitute 
abnormality judgment means. 
In each of the embodiments, the control type vibro-isolating support is 
applied to the engine mount 1 supporting the engine 30. However, a control 
type vibro-isolating support according to the present invention is not 
limitedly applied to an engine mount, but may otherwise be a 
vibro-isolating support for a vibratory machine tool. 
The setups of the embodiments may be used either independently or in 
combination. A combination of setups results in a complex or synthetic 
advantage, which is a combination of advantages of embodiments. 
In each embodiment, a drive signal y is generated in accordance with 
synchronous filtered X LMS algorithm. The applicable algorithm, however, 
is not limited to this algorithm, but may be normal filtered X LMS 
algorithm or frequency-domain LMS algorithm, for example. If the system 
characteristics are stable, a drive signal y may be generated by a digital 
filter with a fixed factor or an analog filter, and only its phase may be 
varied to make the residual vibration signal e smaller, without using LMS 
algorithm or other adaptive algorithm. 
In each embodiment, a vibro-isolating support of the type filled with fluid 
is used as a source of control vibration. The type of the source of 
control vibration, however, is not limited to this, but may be that with a 
piezoelectric actuator or the like. 
In each embodiment, while low frequency vibration is inputted, vibration 
isolation is effected by the fluid resonance generated when the fluid 
flows through the orifices 5a. For a vibro-isolating support supporting a 
vibrator into which no such low frequency vibration is inputted, there is 
no need of orifice-defining body 5, diaphragm 4, etc. As a result, the 
number of parts is reduced, so that the costs are low. 
In each embodiment, the alarm lamp 20B which is an LED lamp as shown in 
FIG. 2 is used as the alarm raising means. The alarm raising means, 
however is not limited to this lamp, but may be an alarm lamp fitted on a 
dash panel, an alarm device sounding like a buzzer, or a combination of 
them. 
In the fourth embodiment, it is based on the voltage V.sub.0 induced under 
no control to judge variation of the clearance between the electromagnetic 
actuator 10 and magnetic path member 12. Otherwise, however, the clearance 
may be measured directly by means such as a gap sensor, which is fitted 
between the actuator 10 and the member 12. 
According to the first invention, as explained above, it is possible to 
recognize trouble, degradation or other abnormality, if any, in a control 
type vibro-isolating support being used. For example, the apparatus can be 
positively stopped before it is completely out of order. It is therefore 
possible to make the apparatus more reliable when the apparatus is 
actually used, without greatly raising the costs. 
According to the second invention, it is possible to warn that abnormality 
has occurred. The operator or the like making periodic inspection, for 
example, can therefore securely recognize that abnormality has occurred. 
According to the third invention through the 11th invention, it is possible 
to judge if there is abnormality by detecting the state/s of the residual 
vibration signal and/or the drive signal. It is therefore avoidable that 
the apparatus is enlarged and that the costs greatly increase. 
In particular, according to the 6th invention, it is possible to securely 
distinguish the condition where most of the vibration of the vibrator is 
not damped, but transmitted to the support body side, even though the 
vibration damping control is executed. It is therefore possible to more 
precisely judge if there is abnormality. 
According to the 9th invention, the abnormality judgment means can easily 
judge if there is abnormality, because the vibration generated by 
something but the vibrator and inputted into the support body does not 
influence the cross-correlation function of the residual vibration signal 
and the drive signal. 
According to the 11th invention, the abnormality judgment means can judge 
if there is higher-order divergence. It is therefore possible to take 
proper measures depending on the degree of abnormality. 
According to the 12th invention, it is possible to recognize abnormality, 
if any, in the source of control vibration of the type filled with fluid 
when the source is used. For example, the apparatus can be positively 
stopped before it is completely out of order. It is therefore possible to 
make the apparatus more reliable when the apparatus is actually used, 
without largely increasing the costs. 
According to the 13th invention, it is possible to recognize change, if 
any, in the clearance between the movable member and electromagnetic 
actuator while the apparatus is used. It is therefore avoidable to execute 
the vibration damping control in the condition where the clearance has 
largely changed from its proper value. 
According to the 14th invention, the clearance between the movable member 
and electromagnetic actuator is detected with the induced voltage of the 
exciting coil. It is therefore avoidable to enlarge the apparatus and 
largely increase the costs. 
According to the 15th invention and 16th invention, it is possible to 
distinguish the direction of the change in the clearance between the 
movable member and electromagnetic actuator. This can provide useful 
information for later analysis of trouble, etc. 
According to the 17th invention, it is easy to judge if there is 
disconnection or other abnormality in the circuit including the exciting 
coil of the electromagnetic actuator. 
According to the 18th invention, it is easy to judge if the electromagnetic 
actuator, inclusive of the exciting coil, is hot. 
In particular, according to the 19th invention, either it is avoidable that 
the electromagnetic actuator becomes even hotter, or it is possible to 
make the actuator out of its hot state. It is therefore avoidable that the 
actuator becomes abnormal due to its high temperature. 
According to the 20th invention, the apparatus may also operate as an 
ordinary vibro-isolating support of the type filled with fluid, which 
generates passive supporting force. It is therefore possible to 
effectively damp various vibrations.