Controlling vibrations
View Patent ↗In order to control vibrations of two parts of a piece of machinery, a variable force may be generated to oppose the vibrations, with the variable force being generated under control of a controller on the basis of an iterative relationship, the iterative relationship being such as to generate the force of one iteration using a controller output signal in frequency domain vector form derived from the controller output signal of the immediately previous iteration in frequency domain vector form plus a frequency domain vector quantity derived from the resultant vibration of more than one previous iteration. Where these two parts are connected by multiple (f) mounting devices, the controller output signals a previous iterations are taken into account, and the frequency domain vector quantity derived from the controller output signals and more than f previous iterations. The information corresponding to the vibration frequency may be derived from a rotating shaft, where the two parts are the engine and chassis of a vehicle. It is also possible generate a force between the two parts which is a harmonic of the frequency of vibration being suppressed.
1. A method of controlling vibrations between two parts of a structure interconnected by f active mounting devices, comprising damping vibrations between the two parts of the structure, detecting the vibrations between the two parts of the structure, generating variable forces to oppose the vibrations transmitted by each of the f mounting devices, and detecting any resultant vibrations due to the net effect of said vibrations and said variable forces; wherein
forces are generated under control of a controller on the basis of an iterative relationship, the iterative relationship being such as to generate the forces of one iteration using controller output signals in frequency domain vector form derived from the controller output signals to the f mounting devices of f immediately previous iterations in frequency domain vector form plus a frequency domain vector quantity derived from the controller output signals to the f mounting devices and the resultant vibrations of more than f previous iterations; and
wherein f=2 and the forces of said one iteration are derived by use of a control relationship:
u (n+1) =u (n) −A[R n ] −1 •y n +p n ;
where:
u n =[u i1 ,u o1 ,u i2 ,u o2 ] is the control output signal at an n th iteration;
y n =[y i1 ,y o1 ,y i2 ,y o2 ] is the measured vibration signal at the n th iteration;
p =[p i1 ,p o1 ,p i2 ,p o2 ] is an optional perturbation added to the control output of the n th iteration;
where:
[u i1 , u o1 ] forms the frequency domain vector representation of the sinusoidal signal sent to a first mounting device;
[u i2 , u o2 ] forms the frequency domain vector representation of the sinusoidal signal sent to a second mounting device;
[y i1 , y o1 ] forms the frequency domain vector representation of the sinusoidal signal measured at a first detection point;
[y i2 , y o2 ] forms the frequency domain vector representation of the sinusoidal signal measured at a second detection point;
[p i1 , p o1 ] forms the frequency domain vector representation of the optional perturbation added to the control signal sent to the first mounting device;
[p i2 , p o2 ] forms the frequency domain vector representation of the optional perturbation added to the control signal sent to the second mounting device;
A is a scalar value such that 0<A <1; and
[R n ] −1 is the inverse of the system gain matrix [R]calculated from u n , u n−1 , u n−2 , y n , y n−1 , y n−2 ;
such that:
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2. An apparatus for controlling vibrations between two parts of a structure comprising f active mounting devices interconnecting the two parts of the structure:
a controller for controlling the f active mounting devices to control the vibrations between the two parts;
at least one detector for detecting the vibrations between the two parts of the structure;
actuators for generating a variable forces to oppose the vibrations transmitted by the respective f mounting devices, the at least one detector being arranged to detect the resultant vibrations due to the net effect of said vibrations and said variable forces;
wherein the actuators for generating the variable forces are arranged to be controlled by the controller to generate the forces on the basis of an iterative relationship, the iterative relationship being such as to generate the forces of one iteration using controller output signals in frequency domain vector form derived from the controller output signals to the f mounting devices off immediately previous iterations in frequency domain vector form plus a frequency domain vector quantity derived from the controller output signals to the f mounting devices and the resultant vibrations of more than f previous iterations; and
wherein f=2 and the forces of said one iteration are derived by use of a control relationship:
u (n+1) =u (n) −A [R n ] −1 •y n +p n ;
where:
u n =[u i1 , u o1 , U i2 , u o2 ] is the control output signal at an n th iteration;
y n =[y i1 , y o1 , y i2 , y o2 ] is the measured vibration signal at the n th iteration;
p =[p i1 , p o1 ,p i2 , p o2 ] is an optional perturbation added to the control output of the n th iteration;
where
[u i1 , u o1 ] forms the frequency domain vector representation of the sinusoidal signal sent to a first mounting device;
[u i2 , u o2 ] forms the frequency domain vector representation of the sinusoidal signal sent to a second mounting device;
[y i1 , y o1 ] forms the frequency domain vector representation of the sinusoidal signal measured at a first detection point;
[y i2 , y o2 ] forms the frequency domain vector representation of the sinusoidal signal measured at a second detection point;
[p i1 , p o1 ] forms the frequency domain vector representation of the optional perturbation added to the control signal sent to the first mounting device;
[p i2 , p o2 ] forms the frequency domain vector representation of the optional perturbation added to the control signal sent to the second mounting device;
wherein A is a scalar value such that 0<A<1;
[R n ] −1 is the inverse of the system gain matrix [R]calculated from u n , u n−1 , u n−2 , y n , y n−1 , y n−2 ;
such that:
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3. An apparatus according to claim 2 , wherein each mounting device is a hydraulically damped mounting device between the two parts of the structure, having two anchor parts connected by a first deformable wall, a working chamber bounded by the first deformable wall and a rigid partition rigidly associated with a first one of the anchor parts, the working chamber containing hydraulic fluid, a compensation chamber for the hydraulic fluid, the compensation chamber being bounded by a second deformable wall, a passageway between the chambers to allow fluid communication therebetween, a flexible diaphragm in direct contact with the hydraulic fluid in the working chamber, the diaphragm acting as a barrier between the hydraulic fluid and a gas chamber and being fixed its periphery, and means for driving an intermediate part of the diaphragm to impart a vibration to the hydraulic fluid, wherein the means for driving the intermediate part of the diaphragm forms said means for generating the vibrations.