Design of autonomous steering actuator for Formula Student Driverless car

Formula Student is a design competition for engineering students across the world where students design and manufacture a functional prototype of a single-seater formula-car. In 2017, Formula Student Germany (FSG) was the first to introduce a new competition class, Formula Student Driverless (FSD) where a Driverless Vehicle (DV) performs a series of events autonomously without any human control. The 2019 Formula Student car of Squadra Corse (SC19 – Desi) is a fully electric car and will be converted into a Driverless Vehicle which will be steered by an electro-mechanical steering actuator controlled autonomously by an on-board controller. The vehicle’s autonomous system shall ensure that the car is being steered autonomously to have manageable handling coupled with good acceleration and braking capabilities at any given point in the test circuit. The system must also comply with the Formula Student Driverless 2020 regulations and must enable the car to perform in the various static and dynamic events of Formula Student Driverless competition. The steering system in Desi is a custom-designed mechanical rack and pinion steering with a herringbone gear profile. The proposed autonomous steering system comprises a drive unit and a transfer unit. The drive unit comprises a BLDC motor coupled with a planetary gearbox rigidly coupled to a ball screw shaft over which a ball nut is engaged. The ball screw and nut mechanism converts the rotary motion from the gearbox to linear motion to the ball nut. The transfer unit comprises a block connecting the ball nut and actuator link which in turn connects the clevises on the rack ends. These clevises connect with the steering tie rods on both ends and turn the front wheels. A brief explanation about the steering controller logic and Failure Mode and Effect Analysis (FMEA) will also be covered in the thesis. The choice of actuator system and its design is governed by several parameters such as the space constraints inside the cockpit, actuation rate of the steering to replicate driver usage, duty cycle of actuator operation, existing powerpack available in the car to power the actuator and preliminary structural analysis of the configuration through experience to name a few. Also explained in this thesis are several other design ideas, the reasons why they were not considered and why this solution is the best of them all.