Hardware and software design and integration of an electromechanical brake actuator for an autonomous vehicle

The rapid evolution of autonomous driving requires integrating brake automation into conventional hydraulic brakes: although reliable, they are limited by the dependence on driver brake pedal input, making them unsuitable for highly automated vehicles. In the long term, brake-by-wire technology could even eliminate the need for a physical brake pedal in the cabin, further supporting fully autonomous driving. This thesis faces the challenge of developing from scratch the hardware/software of a cost-effective electromechanical brake actuator for an autonomous vehicle (AV) demonstrator, owned by Bylogix srl, with the prospect of extending its application to other AVs. The proposed system enables direct pressure generation within the hydraulic circuit, allowing autonomous operation without major modifications to the existing braking system. The pressure is generated by another master cylinder connected to the brake line, actuated by a custom-built ball screw jack actuated by a 12 V-DC motor, controlled by a stand-alone control unit. The actuator is designed in compliance with European regulations of braking system for M1 passenger vehicles. Concerning vehicle safety, the brake actuator is positioned upstream of the ESP/ABS unit, leaving them unmodified and fully operational. Beyond normal braking tasks, this may also enable the implementation of advanced functions such as autonomous emergency braking, which enhances overall vehicle safety in critical scenarios. The work is structured as follows. 1)??Braking system characterization: analytical calculations and MATLAB/Simulink simulations define the actuator’s performance requirements, such as the time needed to reach the target pressure. 2)??Hardware design and hydraulic integration: using SolidWorks and CREO, the actuator is designed for optimal vehicle integration and packaging. Structural FEM analysis in ALTAIR HyperMesh verifies assembly strength, while the actuator housing and brake pump interface are modeled, coded, and manufactured via CNC machining. A hydraulic study determines the optimal position of the actuated master cylinder to minimize modifications to the existing braking system. Finally, a custom wiring harness provides power and ensures stable communication with the vehicle CAN-bus network and pressure sensor specifically installed on the brake hydraulic line. 3)??Controller design: the braking pressure is regulated by a controller designed using model-based programming in MATLAB Simulink. The system relies on a controller that adjusts the pressure in real time based on feedback from a pressure sensor. 4)??Software integration and validation: the control logic is translated into C code and embedded in the actuator’s dedicated control unit, ensuring modularity. The unit receives braking targets from the vehicle Body Control Module and provides feedback. The complete system is integrated into the vehicle’s electronic architecture and validated on a dedicated test bench replicating real operating conditions. Results show that the device achieves the required braking pressures with stable and accurate control, while ensuring compatibility with the hydraulic, electronic and software architecture of the AV, confirming the feasibility of integrating the electromechanical brake actuator: this represents a significant step toward low-cost braking automation and the eventual removal of the brake pedal in future fully autonomous vehicles.