Unmanned aerial systems (UASs) combine a drone with a sensor payload and analytics to deliver a remote monitoring and diagnostic service. To date, UASs have been used primarily for collecting images over an area, often geo-rectified so that the images are accurately tied to a location on a digital map. Examples include agricultural crop quality, environmental monitoring of industrial facilities, and surveillance of possible encroachment or third-party activity on a site.
But there are many opportunities for a UAS beyond making visual observations from a distance, and some of these will be of great potential value to machinery condition monitoring and diagnostics.
Drones have become inexpensive and popular, due to economies of scale for small microcontrollers that allow rotorcraft drones and fixed wing drones to remain stable in flight without extensive operator training. Most such drones are small, and can only carry a small payload. Flight times are short, on the order of ten to twenty minutes, depending on mission profile and payload. Communication distances are also short. This is an advantage for safe operation, as there is less chance that the operator will lose situational awareness and crash the drone. Small drones flying slowly are much less of a hazard than large, fast drones; however, for a UAS to be a cost-effective method for condition monitoring of remote, distributed assets, the drone must be large enough to carry a reliable payload, withstand wind gusts, and have sufficient battery power or fuel for a reasonable mission duration, both for flying as well as powering payload and communications systems. Some types of measurements employ contact sensors, and so the UAS must be capable of deploying a sensor to bring it into contact with a surface before collecting data. Hybrid drones are coming to market, which are able to take off and land vertically on a charging station using rotors and then use wings for flying a route.
Along with technical issues with using a UAS, there are regulatory issues. A typical UAS is a remote-controlled drone that must remain within line-of-sight of the operator. Regulations in most jurisdictions prohibit flying over inhabited areas and close to airports and helicopter landing pads.
Despite these limitations, there are many opportunities for a UAS for machinery failure prevention, such as:
Vibration (contact, passive)
Ultrasonic structural integrity (contact, active)
Optical thermography & spectroscopy
Chemical analysis (noncontact)
Surface sampling (contact)
Photogrammetry (gauge reading)
A UAS can also be used to deploy permanent sensor packages, or to act as a communication network by flying past a sensor that delivers a burst of time-stamped data that the UAS archives and then delivers to a ground station for analysis.
Active areas of development include: sensor payloads, contact sensor deployment & connection management, autonomous hovering with gusts and contact dynamics, data collection & management, power management, and mission planning. None of these challenges entails basic research. The technical issues are mostly subsystem development and system integration.
More importantly, methods are needed to integrate UASs into regular inspection programs in such a way as to not add risk to the overall operation. Once demonstrated in controlled industrial situations, then a case can be made to regulators that a particular technology suite and mission can be safe. Transport Canada’s Special Flight Operating Certificate follows this principle. While beyond-line-of-sight operations are not yet generally possible in Canada, demonstration systems are already being tested in specific sparsely populated airspace with strict controls on potential risks to the public.
Given this combination of technology development and regulator engagement, it is likely that unmanned aerial systems will become a viable option for reducing the risk to inspectors and lowering costs of condition-based maintenance programs.