Information about Vibration Isolation
Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations. Despite construction distinctions the essence of all vibration isolation systems are similar. Passive vibration isolation systems consist essentially of a mass, spring and damper (dash-pot). Active vibration isolation systems contain along with the spring, a feedback circuit which consists of a piezoelectric accelerometer, a controller, and an electromagnetic transducer. The acceleration (vibration) signal is processed by a control circuit and amplifier. Then it feeds the electromagnetic actuator, which amplifies the signal. As a result of such a feedback system, a considerably stronger suppression of vibrations is achieved compared to ordinary damping.
Another technique used to increase isolation is to use an isolated subframe. This splits the system with an additional mass/spring/damper system. This doubles the high frequency attenuation rolloff, at the cost of introducing additional low frequency modes which may cause the low frequency behaviour to deteriorate. This is commonly used in the rear suspensions of cars with Independent Rear Suspension (IRS), and in the front subframes of some cars. The following graph shows the force into the body for a subframe that is rigidly bolted to the body compared with the red curve that shows a compliantly mounted subframe. Above 42 Hz the compliantly mounted subframe is superior, but below that frequency the bolted in subframe is better.
Another technique used to increase isolation is to use an isolated subframe. This splits the system with an additional mass/spring/damper system. This doubles the high frequency attenuation rolloff, at the cost of introducing additional low frequency modes which may cause the low frequency behaviour to deteriorate. This is commonly used in the rear suspensions of cars with Independent Rear Suspension (IRS), and in the front subframes of some cars. The following graph shows the force into the body for a subframe that is rigidly bolted to the body compared with the red curve that shows a compliantly mounted subframe. Above 42 Hz the compliantly mounted subframe is superior, but below that frequency the bolted in subframe is better.
References
- Harris, C., Piersol, A. , Harris Shock and Vibration Handbook, Fifth Edition, McGraw-Hill, (2002), ISBN 0-07-137081-1 .
See also
External links
- An online resource for engineers involved with machinery vibration isolation.
- http://www.lord.com/Portals/0/VibrationMotionNoise/selecting_a_vibration_shock_isolator.pdf Selecting a vibration/shock isolator, Lord Corporation]
- Vibration isolation is the key to accuracy article
Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.
Vibration is occasionally desirable.
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Vibration is occasionally desirable.
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spring is a flexible elastic object used to store mechanical energy. Springs are usually made out of hardened steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication.
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A dashpot is a mechanical device, a damper which resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy.
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Piezoelectricity is the ability of some materials (notably crystals and certain ceramics) to generate an electric potential[1] in response to applied mechanical stress. This may take the form of a separation of electric charge across the crystal lattice.
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accelerometer is a measuring device for specific external force. Specific external force is the sum total of external forces acting on an object divided by the mass. Accelerometers do not measure internal forces such as gravity.
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Controller can refer to several things:
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- Microcontroller, a computing device
- Memory controller, logic which manages the flow of data in a computer system
- Game controller, a device used for video games
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Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles.
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transducer is a device, usually electrical, electronic, electro-mechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy to another for various purposes including measurement or information transfer (for example, pressure sensors).
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A shock absorber in common parlance (or damper in technical use) is a mechanical device designed to smooth out or damp a sudden shock impulse and dissipate kinetic energy. It is analogous to a resistor in an electric RLC circuit.
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Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.
Vibration is occasionally desirable.
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Vibration is occasionally desirable.
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Noise, Vibration, and Harshness, also known as Noise and Vibration, abbreviated to NVH and N&V respectively, is the name given to the field of measuring, and modifying, the noise and vibration characteristics of vehicles, particularly cars and trucks.
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