MARTY: Rollcage and Interior Modifications
Rollcage, Seats, and Harnesses
To bring the DeLorean up to modern track vehicle safety standards, a rollcage, race seats, and six-point harnesses were added. The rollcage is designed to also add some much-needed torsional stiffness to the chassis, and thus also ties to the front and rear strut towers, and the transmission tunnel of the frame. While we led the unique MARTY-specific design process, the final rollcage was verified and fabricated by the experienced team at TC Design.
The gullwing doors, highly raked windscreen, and low roofline make this an unusual packaging problem. The upper longitudinal tubes need to run along the center to clear the doors, and the front hoop needs to tuck up into the windscreen pocket to avoid further obscuring the already-limited view of the driver. Removing the thick door trim made it possible to comfortably package the side tubes.
The racing bucket seats are mounted to a billet bracket that allows for tilt adjustment, which is needed for taller people to sit comfortably in the vehicle. The top two points of the harnesses tie to the rollcage, while the bottom four bolt through areas of the fibreglass tub that we reinforced with aluminum doubler plates.
Interior and Human-Machine Interface
Since much of the original trim was removed to make room for the rollcage and new equipment, there was an opportunity to design a new interior. The primary goal was to enable the operators to safely oversee autonomous testing. This is manifest in the design and placement of the physical control interface, as well as the clean aesthetic that minimizes distraction.
The center console design is modular, so panels can be quickly moved around, added, and replaced. Two machined aluminum rails run on either side, to which instrument panels can be bolted. The wiring runs underneath these panels towards the back of the car, and can be easily accessed of maintainence/modification by lifting up the panels.
The primary operational controls are split into two panels. The first contains the two safety-stop buttons, and two autonomy toggle switches. The left safety-stop button triggers a 'soft' stop of the Renovo drivetrain management system, which immediately zeroes the requested torque from the motors and disables the power electronics modules. The right safety-stop button directly releases the relays that energize the battery pack, and are only to be used in the case that the 'soft' stop fails; this has never been needed. The safety driver uses the toggle switches to select between manual and computer control of the steering and throttle. The safety-stop buttons and toggle switches are deliberately placed within easy, immediate reach of the driver.
The second panel contains the drive mode selector. The safety driver uses this to choose between Reverse, Neutral, Drive, and Autonomous mode. A pull-to-release mechanical interlock, implemented with a spring plunger, prevents accidental switching from Drive to Autonomous. This interlock feature has proven to be very valuable in practice, both to prevent unintended activation and to ease the mental workload of the safety driver. The rotary and toggle switches were chosen with an emphasis on high mechanical detent force, in order to provide robustness to accidental swtiching as well as good tactile feedback. Their functionality is implemented in the software running on the hard-real-time control computer.
The two tablets in the upper portion of the center console display vital information about the status of the drivetrain; this software was developed by Renovo. The interior trim was also designed and fabricated by Renovo, with Stanford's collaboration. It is made from bent and welded sheet steel that has been powder coated matte black to minimize reflections from the sun; this is especially relevant in California, where experiments are conducted.
Design, Development, and Fabrication Insights
Early in the rollcage design process, we used PVC tubes to quickly mock-up and test designs. This rapidly illuminated the challenges unique to the DeLorean, namely driver visibility and the difficulty of fitting taller people in the car. Much better to catch this weird stuff early, than waiting till the cage is welded up in the car!
A few work-in-progress images of the dash, control panel, and center console are also included below.
Contributors
The rollcage and seat placement was design and installed in the summer of 2014, during the big initial electrification. Jon Goh and Phill Giliver were the Stanford team on this project, with final verification and fabrication by TC Designs.
The interior was revamped in the summer of 2015, and was a collaboration between Renovo, who were reponsible for the interior trim and system monitoring software, and Stanford, who developed the center console, and door + misc. trim. The Stanford team at this time consisted of Jon Goh, Tushar Goel, Phill Giliver, and Mike Carter.