Uncrewed Systems Technology 046

30 Dossier | IAC AV-21 fitted behind the engine shaft, and is the reason the car has been able to operate without a clutch pedal. It is similar to a torque converter and had previously been used in an IMSA (International Motor Sports Association) Series. Behind it is the stock gearbox. This clutch achieved multiple objectives for the vehicle. Not only did it greatly simplify the control of vehicle launches from the pit area, but its compact size allowed for the newly specified engine to be slightly longer than what the vehicle was initially designed around. That produced significant cost savings and made the vehicles easier to operate. Mitchell adds, “All these systems are proven in modern automotive vehicles, and it was all possible because industry stepped up to sponsor us – some of our suppliers have contributed six-to- seven figures’ worth of equipment to the programme.” Structure and materials Given the attributes of the Indy Light chassis in terms of strength, aerodynamics, downforce and so on, the AV-21 shares much in common structurally with it. The ‘safety cell’ (a misnomer given the absence of a driver) is a composite structure consisting of two carbon fibre layers sandwiching an aluminium honeycomb core, while additional aluminium bulkheads sit fore and aft of the tub shape. A pedal bulkhead sits at the front, while a dash bulkhead sits just inside the cockpit cover. The monocoque and nose are made with essentially the same materials and bulkheads, as is the rear attenuator where the rear wing mounts. The bodywork itself is carbon fibre with a cloth core material – Coffey comments that this is a system called TNT400, and likens it to a black cotton. It sits between the carbon fibres as they are cured, after being wicked with resin. Mitchell notes that on top of achieving the right structural strength, aerodynamics and NVH characteristics, integrating all the sensors inside the cockpit of a pre-existing racecar without having them come loose, become misaligned or break during autonomous operations at 190 mph was a challenge that no other team has undertaken. Especially important to tackling that was the cockpit cover, which represents the largest focal point of Dallara’s custom body work on the AV-21. This had to enclose the various sensors used for real- time navigation and path-planning without ruining the aerodynamics of the car. Of the cover, Coffey adds, “We worked very closely with Clemson University to make the cover both rugged and easily serviceable. Ideally, we, the suppliers and the teams would prefer to ‘set and forget’ the electronics, but that turned out to be impossible, so we had to do a lot of work between tests and races that required popping the top off. “To integrate the GNSS atop the roll hoop, we bought some carbon aero fairings and made a whole assembly out of that, which turned out as a very elegant solution to mounting all those parts securely and aesthetically. And once all the navigation systems were located, Clemson made an aero surface in CAD to go on top of them, with a lot of CFD work from our aero department in Italy going into optimising that for manufacture.” The structure also includes a support strut under the forwardmost Lidar to retain the cockpit cover at higher speeds. It is visually reminiscent of the FIA halo, but is positioned and designed carefully to avoid impacting the Lidar’s FoV. “All these modified structures that are unique to the AV-21 are made like the bodywork: carbon fibre sandwiching TNT400 as a core,” Coffey adds. In addition, the GNSS mounts on the sidepods and the front of the monocoque are multi-jet fusion-printed using PA12 Nylon, as are the mounts for the side radars beneath the cockpit cover. Navigation systems Of all the navigation sensors on board the AV-21, Lidars are generally the most important in terms of sensing critical data for decision-making. Mitchell says, “Right now, our use of cameras is limited at higher speeds. “Part of the reason for that is the computing time taken to communicate and interpret camera data, and hence make an optimal decision based on it. The efficiency of the Lidar at high speed is crucial to that. The radars meanwhile are especially useful for measuring the radial velocity of objects around the car.” The six cameras used are Mako G-319Cs with a maximum resolution of 2064 x 1544, a spectral range October/November 2022 | Uncrewed Systems Technology The cockpit cover was one of the biggest focal points of the composite bodywork on the AV-21 (Courtesy of Clemson University)