Vibration isolation is one of the proven methods to disconnect the source from the recipient, usually at the interface, termed as the path.

The Source-Path-Receiver model is extensively used in any physical energy transfer system to characterize the strength of the vibration source, contributing frequencies and their causes, how it utilizes the available connections to transfer the energy and finally its depiction at the receiver position; be it automotive, structural or any system with dynamic composition, this rule and method can be effectively used.

The fundamental understanding from the above model is to determine the feasible interfaces where vibration isolation can be introduced effectively, hence the solution approach hovers around either the source to path or path to receiver or both.

Before one can really understand vibration isolation, they need to understand the causes of vibration. This can be attributed to multiple factors, including mechanical factors like uneven mass distribution in rotating components and external forces such as impacts.

Resonance is also a possible cause when external vibrations align with system's natural frequency thus amplifying the response effect. Operational forces from machinery, repetitive loading and material characteristics such as stiffness and damping play significant roles as well.

Vibration isolation is broadly grouped in to Passive and Active types.

Passive Vibration Isolation :

These do not require external energy or control systems to function. Instead, they rely on the properties of materials and the arrangement of mechanical components. Some of known components are rubber mounts (Visco-elastic), physical and membrane springs, tuned mass dampers and isolators that can absorb and dissipate vibrations based on their inherent properties.

 

Concept of passive isolation

 

While it is fair to assume any visco-elastic member as a vibration isolator, it shall be strictly seen from the perspective of which frequencies are in focus for isolation; after all, the entire physics of vibration isolation is based on the frequency considerations as a prerequisite.

The other key inputs to realise an effective passive vibration isolation is of static stiffness of the visco-elastic member, load over area considerations, mass and CG of the load etc. Also important is the boundary conditions in which the isolator is to operate, such as humidity, temperature range and conditions of alkaline and acidic contents in the air.

Based on the above matrix, calculations are made to arrive at the effective isolation frequencies, their insertion losses and the overall limits of isolation as can be achieved in practice.

Passive isolation - means and materials

 

Active Vibration Isolation:

Active isolation systems incorporate sensors and actuators to detect vibrations and respond in real-time. These systems actively counteract vibrations by applying forces opposite to those generated by the source and help maintain the stability of the system.

Concept of Active isolation

 

While the fundamental components of a spring and damper in some form exist in active damping, what makes it really "active" is the inclusion of a looped control to monitor, adapt and finally control the vibrations at the recipient location. A pre-configuration of the basis system is established upon which vibration sensor/s is configured to monitor vibrations in real time, feed it to a control circuit that adjusts the vibration amplitudes through an actuator to neutralise / minimise the responses; this is an iterative close loop that manages the effective vibrations at the target locations effectively.

Here again, like in the case of passive isolation, the frequencies to isolate and their amplitude do matter to put up an effective isolation system. Additionally, the controller system need to work in tandem with the input vibration data and out of phase cancellations have to happen almost in real time. Degrees of freedom and singularity of frequencies are also vital considerations to make in such setup.

Active vibration - system components

 

Overall, both passive and active isolation methods have their merits and limitations; while passive systems are economically viable vis-à-vis active systems, the effectiveness of isolation may be limited depending on application feasibility and practicality. However, the calculations to arrive at passive isolation are much simpler, materials are readily available and implementation methods are not too complicated unless it involves large mass structures and equipment being at very non-conducive environment.

Active systems on the other hand are highly effective and work with great credibility, once systems are tuned and put to use with appropriate configurations. Both the initial costs and costs of maintenance are higher given the complexity of any closed loop apparatus. Most systems are customised and thus the design becomes proprietary; OEM support and availability of parts is crucial to continued use of active dampers.

NV Dynamics has for over 15 years practiced implementing passive vibration solutions across multiple industries and equipment; from small industrial machinery to large gym and dance floors, we have worked extensively in offering credible solutions; Metro rail gave us a paradigm shift in the very way vibration isolation is thought and practiced. From recommending isolation to rail track to working on isolation for rolling stock, an entire bouquet of opportunities opened up and is progressing.

On the active isolation front, we have worked on few critical applications and the knowledge on its implementation is improving by the day.