Abstract :
Environmental conditions so severe as to pose exceptional design risk, sometimes called extreme or hostile environments, must be addressed by special design solutions. These solutions are often constrained by power, geometry, cost, and other factors, making it particularly difficult for the designer to obtain a solution that simultaneously satisfies performance and cost targets. This tutorial illustrates the design process for extreme environments using an example taken from the HDD industry. In this example, a small battery-operated instrumentation package - the HDD sonde - must accurately determine pitch and roll orientation in an operating environment characterized by continual, often violent, and essentially unconstrained shock and vibration loads. As the tutorial example illustrates, a satisfactory design solution requires careful component selection; multiple levels of shock and vibration isolation; careful pitch and roll calibrations over the entire anticipated operating temperature range; and time-varying signal processing to adjust the pitch and roll presentation dynamics according to task requirements at different times during the bore. The sonde´s battery pack must be selected and designed to meet the same design constraints if operating requirements are to be satisfied at the system level. A commercial HDD sonde is capable of providing sub-degree pitch and roll accuracy despite the temperature changes and continuous shock and vibration typical of the underground construction environment.
