Unmanned Systems Technology 014 | Quantum Tron | Radio links and telemetry | Unmanned Aerial Vehicles | Protonex fuel cell | Ancillary systems | AUVSI 2017 Show report

8 Platform one June/July 2017 | Unmanned Systems Technology Inspired by technology used in outlandish single-wheel vehicles, Paha Designs is developing a way to give multi-wheel UGVs more stability in certain conditions (writes Peter Donaldson). Most ground vehicles face a trade- off between high-speed cornering capabilities on roads and good offroad attributes such as high ground clearance and the ability to climb over large obstacles. The company’s Benjamin Meager, however, has invented a means of combining all these abilities in multi- axle vehicles with propulsion systems inside the wheels below the axle line to provide a very low centre of gravity. Granted a US patent in October last year, the concept improves on earlier designs for similar vehicles with just a single wheel, as the use of two or more axles eliminates the risk of a power unit Novatel has unveiled a system to improve navigation performance for UGVs experiencing GNSS outage (writes Rory Jackson from the AUVSI show). The system, called SPAN, has three elements. The first is dead reckoning that uses a low-cost MEMS IMU. SPAN- compatible IMUs include the Epson G320-N, ADIS-16488 and STIM300, as well as fibre optic gyros and MEMS IMUs from Novatel itself, according to Sheena Dixon, the company’s SPAN technical lead. “High-end tactical-grade IMUs don’t require much effort to model the errors, because those sensors are quite powerful to begin with, but as you move down in price there’s a lot more work to make cheaper MEMS IMUs more rotating around the inner circumference of the wheel instead of driving the wheel along the ground. Meager’s hybrid propulsion systems include a motor and an internal combustion engine packaged into the useable in navigation systems,” she said. “The Epson G320-N is the newest. We measured down to a 0.15% error over distance travelled in a one-hour complete GNSS outage scenario.” The second element is an enhanced routine implemented to detect and correct kinematic alignments in reverse, and to achieve them at lower velocities than previously required. Also, historically the kinematic alignment routine has relied on an assumption of a level vehicle, as in zero roll/pitch. Adding a small, approximately 10 s, static detection period now enables a roll/pitch estimate and removes such a restriction, allowing robust kinematic alignments on slopes even with lower- cost MEMS devices. The third element, Novatel’s patented wheel with a battery and fuel tank, along with a control unit consisting of an electronic speed controller for the motor and an electronic throttle for the engine. Wheel speeds and directions can be controlled individually, eliminating the need for a separate steering mechanism and enabling greater manoeuvrability – turning on the spot for example. Other designs can steer by changing the length of a linear actuator, some with a combination of both methods. The technology applies to manned, unmanned, remotely operated and autonomous vehicles for a wide range of applications, including amphibious. Because these vehicles have no natural top or bottom they can flip over and continue on their way; some can climb stairs at high speeds and some can even drive on water owing to the buoyancy and tread pattern of the tyres. ‘phase windup’ technology, constrains azimuth error growth in low dynamic conditions that are unfavourable to inertial navigation, without requiring additional hardware integrations. “We can extract the phase changes from our existing navigation equipment and issue a heading update into our inertial filter. We have our signal- tracking algorithm and inertial algorithm running on the same receiver,” Dixon explained. “The SPAN technology helps in two situations: if you’re in a completely GNSS-denied environment or an environment where you’re going in long, straight lines, very slowly and with little movement observable to the inertial filter,” she said. “That’s where you tend to see drifts in your positioning system.” Improved stability for UGVs New position on GNSS loss Ground vehicles Ground vehicles Benjamin Meager’s designs were inspired by peculiar monowheel vehicles such as this Purves Dynasphere of the early 1930s