Viscous Damper Regulation Simplified

By Jim O Neal


The development of the so called clever fluids and viscous dampers founded upon them has enabled way more efficient and convenient vibration attenuation choices than previously. This sort of semi-active actuators are already used in quite a few industries: autos, washing machines, bridges, building structures to name a few. This is on account of the small size and especially to the fast regulation capability they present: they may be regulated in accordance with the exact specifications of your shaking system.

This article offers the central theoretical resolution associated with my viscous damper and certain considerations with regard to the assessment of shake. There are other possibilities to regulate the actuator, but I have discovered this particular one simple and beneficial enough. The strategy is not my invention and it applies to any viscous damper. I bow to Jeong-Hoi Koo, whose "Groundhook" algorithm or "velocity-based on-off groundhook control" (On-Off VBG) shown in his dissertation I applied.

Groundhook Law on Two-Degree-of-Freedom System

The context where the control law is offered is a two-degree-of-freedom mass-spring-damper system. The basic principle of a groundhook control is that the mass whose shake is attenuated, is hooked to the ground with a damping element. The semi-active part is the controlled, viscous damper which is positioned between the vibrating masses. The control law is simple: when the upper vibrating mass is moving upwards and the lower weight down, strain is applied to the viscous damper. This induces a drawing force to the structure weight to the equilibrium situation of the system.

Groundhook Law Made easy on Single-Degree-of-Freedom System

Nevertheless, as a direct consequence of a presupposition or an approximation, this law is often made simple. Should th velocity of the lower mass is estimated to be really small and at the same phase with the vibrating mass all the time, the system may be modelled with a single-degree-of-freedom vibration system. If your higher shaking mass is going right up and the lower weight stays put, strain is applied to the viscous damper. That triggers just as before a pulling force to the structure weight toward the stability position of the system.

Relevance of Understanding Your Shake

In order to acquire the most out of the attenuation possibilities of a viscous damper, it's essential to carefully understand your vibrating system. This means that, it's essential to measure the shake of the object accurately to find out the disturbing frequencies, their amplitudes and the time instant when the wavelengths occur (for instance three seconds from startup).

Solely once measuring these, it is possible to come up with exactly how a semi-active viscous damper would clear up the issue. Or maybe you will learn that a common passive damper is a more viable option. Yet, when integrating smart control methods on your solution, you need to definitely examine the vibration system to the bottom.




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