For my second season on DUT I as working on the Innerwheel of the car. The custom sized tires the team uses enables this to be an extremely interesting subsystem, as the Innerwheel consists of a transmission, an upright, a hub, and motor mounting all within one system. The challenge is made more exciting due to a rules change for the 2020 season of Formula Student. This season's cars are allowed to run powered under-body aerodynamic devices. This change drastically increases the downforce that the car is able to generate, increasing lateral acceleration but wheel loads along with it.

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This challenge is being addressed through the implementation of cutting edge technology. The upright portion of the Innerwheel is being analyzed via Topological Optimization for additive manufacturing. Motor cooling is being handled by an A.I. designed cooling sleeve, and the hub is leveraging a new aluminum alloy to reduce its mass.

 

• Design Goals:         5% reduction in system mass and less than 0.7 degrees of camber change per                                  kN of normal load

• Design Methods:    Mass is being saved by leveraging cutting edge technologies and                                                       materials, the integration of features, and the optimization of load paths.

• Achievements:        

This section will be updated as the season progresses and the design is finalized. Drawings and images are available upon request.

My first year on DUT Racing had a steep learning curve for me. Placed into the Powertrain department, I was initially tasked with motor selection and rotor design. I had very limited experience in electrical motors, having done my undergrad design team experience with internal combustion engines. By reaching out to previous team members I determined that the team takes the approach that we want to be motor limited as little as possible. In DUT that is a challenge, as we run custom, very small tires made out of a special compound with an exceptionally high mu. Working with the Aerodynamics, VD, and Controls departments of the team I generated an envelope of grip the tires have in lateral, longitudinal and combined loading. This, in conjunction with our lap simulation program, LapSim, allowed me to put together a representative curve of the tractive force the tires could tolerate. I then took the steepest of those curves and had a profile I could select my motors off of. Utilizing this I worked with a company, Fischer, to design electric motors that meet our specifications. Once the motors were selected I designed the Rotor and the housing for the electric motor. These parts were designed to hold the permanent magnets for the motors, house and cool the motor, and mount the transmission within the Innerwheel.

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After I had selected the motors I was tasked with designing the manufacturing the wiring system for the car after the original wiring engineer was asked to leave the team. I then spent the remainder of the season developing a wiring system to communicate between 4 electric motors and 13 PCB's and distribute 80kW of power. The wiring system is heavily regulated by the Formula Student Germany rules and must be reliable throughout a wide array of environmental conditions while also being durable enough to withstand inertial forces, contact with the driver during ingress and egress, and vibrations. 

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• Design Goals:         Design motors that are capable of utilizing the full potential of the custom tires                                  for accelerating and decelerating, through regenerative braking, the car.                                            Develop and manufacture a wiring system capable of reliably carrying high                                        power and data without being heavier that 4.3 kg as set by the cars top level                                      concept.

• Design Methods:     Development of a comprehensive model for the tires tractive envelope and                                        design motors that are just outside of that until they require field weakening to                                  continue accelerating. Develop a full power study for the wiring system to                                          minimize the wiring size used while fully waterproofing and sheathing the                                          wiring.

• Achievements:         Motors, in conjunction with the tires and control systems, secured trophy                                          acceleration results at two of the three competitions. The wiring system was                                      robust enough to do hundreds of km of testing in the rainy Netherlands as well                                  as a full competition in the rain without a failure and had a final system mass                                    of 4.18 kg. Awarded a Siemens Award for Excellence in Electrical System and                                  Harness Design at Formula Student Austria.

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Drawings for the Rotor, Motor Housing and Wiring Looms are available upon request. I can not post them, at the request of the team, due to the motor designs being utilized again for the DUT20.