Unmanned Systems Technology Dec/Jan 2020 | Phoenix UAS | Sonar focus | Construction insight | InterGeo 2019 | Supacat ATMP | Adelan fuel cell | Oregon tour | DSEI 2019 | Copperstone Helix | Power management focus

84 In operation | Copperstone Helix amphibious vehicles operating range for a real-time perspective of the vehicle’s surroundings. “The rover will also use its embedded autopilot software to modulate the scrolls for the velocities required on different terrain softnesses and water viscosities, to get to the mission waypoint,” Olmedo adds. Samples for tailings engineers are typically collected across areas of mud just next to the discharge pipes, then brought back to them to be analysed the same day – a far quicker turnaround than is normal for this kind of work. From the launch point, be it from hard ground or the shore of a pond, the Helix therefore first makes its way to the point of discharge. The distance it has to cover varies between locations. Sometimes, the terrain allows a launch area just 200 m from the discharge pipe; at other times the operators and researchers must set up from an opposite shore, and the rover travels across 3-5 km of water before sampling. “The scroll geometry greatly affects how we move on different soils, so we’ve tailored the rovers to traverse multiple different soil types, and to predict the performance of the vehicle across varying deposits,” Olmedo explains. Lipsett adds, “It’s also useful for harder ground. With two screws on each side, it’s easier to achieve differential ‘four-wheeled’ type steering on any terrain type, and transitioning from one terrain type to another without losing traction performance.” The vehicle achieves four degrees of freedom by having each of the four screws controlled by an individual electric motor, with control similar to skid steering. For example, to turn to the left, the operator or autopilot can speed up the two right-hand screws and slow (or reverse) the left-hand screws. Also, the screws impart a slight side force when rotating, which further helps turning while in motion by adding an orthogonal movement. On harder ground, the screws can all be turned in the same direction, to enable it to ‘roll’ sideways (as if on wheels) towards the next waypoint. Samples and surveys Some tailings are very close to water or beneath a few feet of it, while some are embedded in thick mud. To account for the different kinds of places samples must be extracted from, the Helix rovers can be equipped with various sampler payloads. “There are standard geotechnical samplers for water and mud, and we’ve also developed our own, some of which are simple – essentially servo-actuated buckets for scooping up silts and soils,” Olmedo explains. “Others are slightly more complex though, such as tubes with one-way valves at the bottom to suck in samples without dropping them, or piston tubes to provide more cohesion for more fluidic samples and to keep the operating mechanism [the piston] at the top of the tube where it’s safer and will last longer.” Lipsett adds, “We also have a grab sampler, essentially a contact-activated claw that grabs a clump of soil upon touching it, before pulling back. And we have an auger attachment so that we can drill through hard crust or ice to get to samples.” Furthermore, the company has patented a soft-soil sampler that uses a pair of rotating blades to cut and retrieve samples from beaches or pond beds. The samplers are often integrated under or around the central tower on the vehicle, which mechanically lowers them into the water (or forces them into the wet soil) under the chassis. They are connected electronically to the rovers’ CPUs, so that the operator can use them to get feedback on the weight and resistance of the soil being worked with, or to be activated autonomously at pre- selected waypoints. Mechanised magazines or racks can be stored inside the vehicle to allow the payloads to keep samples separate from one another, to prevent cross- contamination. For more information on the waste ponds, various bathymetry survey payloads have been integrated to model and calculate the volumes of tailings in the water. The company prefers either highly ruggedised sidescan sonars or low-cost (almost single-use) systems owing to the damage the payloads can suffer from the pond waters. “Some clients need sub-bottom profiling, so for those we use larger bathymetric sonars and equip them on the Helix AR2 rather than the 25,” Lipsett notes. “We can also carry a range of other survey payloads, such as turbidity sensors to identify exactly where the mud-line is.” December/January 2020 | Unmanned Systems Technology The lateral rotation of the scroll tracks allows the vehicle to turn flexibly, while stationary and in motion, as well as strafe sideways