Engineers and scientists are constantly pushing the envelope to deploy embedded equipment in extreme environments. The recent Deepwater Horizon oil rig disaster Ė and subsequent failures to cap the well thatís leaking oil into the Gulf of Mexico Ė illustrate all too clearly the consequences of such equipment failing. The challenges engineers face in capping the well and in tracking oil dispersion stem largely from the extreme environment they are working in. Remote monitoring, control systems, autonomous robotics, and all embedded systems become much harder to implement in extreme environments like the deep ocean.
This article explores the challenges system designers face in providing power to and designing control systems for equipment deployed in extreme environments.
One of the challenges in any embedded system deployed to an extreme environment is providing power. Whether itís because of deployment in a remote location or because it must be self-contained, most embedded equipment for extreme environments uses battery power. Introducing batteries into a system also introduces additional weight and requires additional space, both of which are usually at a premium in embedded systems. The space and weight costs associated with the introduction of an adequate power source often affect the design (or redesign) of the entire system.
In the case of an autonomous robot, engineers need to power a controller, communication equipment and circuitry, motors, and drives, as well as provide sensor excitation, just to cover the basics. The power allocated for each of these subsystems determines the number of sensors allowable, motor and actuator power level, and the rate and range of communication. Trying to balance total power consumption between all the systems and still maintain all the desired functionality while meeting size and weight restrictions can drive most of the design decisions, and almost always involves trade-offs, with designers prioritizing certain characteristics of their systems over others.
Engineers are now trying to address the power challenge in embedded remote systems from both sides of the problem. One approach is to use some source of renewable energy to recharge the batteries and generate sustained power. The other is to alter the structure and operation of subsystems themselves to be smarter with the power that is available. Often both approaches are applied to the same design, as in the case of a solar-powered, programmable wireless sensor node installation.
Figure 1. This programmable wireless sensor node for voltage measurements is encased in an IP (ingress protection) enclosure for protection from the environment. Engineers can program it to perform selective sampling and sample averaging.
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Renewable energy for embedded systems
Renewable energy still has its challenges, including variability in power output depending on environmental conditions and, again, size and weight restrictions. Equipping installations with renewable energy generation equipment also requires specialized engineering expertise to integrate the power source with the embedded system hardware. As renewable energy generation and storage technology continues to mature, however, so will the possibility to use it in a wider variety of remote applications.