Design and implementation of an Emergency Brake System (EBS) for a Driverless Vehicle

Autonomous driving technology is gaining a lot of attention in the automotive industry. Since most of the accidents are caused by human related errors (94%), the widespread diffusion of autonomous vehicles is expected to reduce errors related to driver distraction, leading to less accidents and hence to an improved road safety. Nowadays, almost every vehicle is equipped with Advanced Driver Assistance Systems (ADAS) as adaptive cruise control, lane keeping, collision avoidance, parking assistance, and also includes Electronic Stability Program (ESP), Anti-locking Braking System (ABS) which are in charge of providing emergency assistance and reduce the workload of the driver. In this context, the Formula Student Driverless competition provides a very stimulating and instructive environment, that helps students to gain knowledge by designing and implementing new technologies on real vehicles. This thesis presents the design and implementation of an autonomous Emergency Brake System designed for a four-wheel drive electric vehicle to compete in the Formula Student Driverless competition. The EBS allows to bring the vehicle to a complete and safe stop within a space of 10 meters and with an actuation time less than 200ms. It can be actuated wirelessly using a Remote Emergency System (RES) or can be triggered whenever there is a fault in the vehicle by the opening of the Shut Down Circuit (SDC) from the Autonomous System. The EBS is designed, referring to the competition rules and starting from the characteristics of the already existing vehicle braking system, as a hydropneumatic system able to autonomously pressurize the brake lines when triggered. The system exploits a high-pressure canister filled with air in combination with a hydro-pneumatic intensifier, in order to obtain in the hydraulic lines enough pressure to actuate the brakes. Different solutions were evaluated basing on dynamic performances, overall weight and dimensions, and packaging. SOLIDWORKS is the main CAD software used for components design, while analysis using HYPERWORKS are carried out on the parts to simulate the forces and stresses expected to be act on the system, verifying its structural compliance. Later, EBS integration with other sub-systems part of the Autonomous System (Remote Emergency System, Low Voltage system, Shut Down Circuit) is considered to guarantee a correct and rule compliant system triggering. Finally, a bench-test is set-up in order to test and validate the performances of the system with the actual components and to study its compatibility in prevision of a future in-vehicle mounting.