Formula Launch Control

Ground Vehicle Dynamics

Overview

This project focuses on developing a launch control system to optimize straight-line acceleration performance for an electric Formula SAE vehicle. The existing vehicle lacks torque control during the acceleration event, often resulting in excessive wheel slip and reduced traction efficiency. A longitudinal vehicle dynamics model was built in Simulink for both rear-wheel drive (RWD) and four-wheel drive (AWD) configurations

Using Pacejka’s Magic Tire Formula, tire forces were modeled as a function of slip ratio. A PID controller was implemented to regulate motor torque and maintain a target slip ratio of 0.2, maximizing tractive force while improving vehicle stability. The goal is fully automated torque control with minimal driver input

 Figure 1. 4WD Simulink control model

Methodology

A longitudinal vehicle dynamics model was developed in Simulink for both rear-wheel drive (RWD) and four-wheel drive (FWD + RWD) configurations of a Formula SAE electric vehicle. The model includes vehicle mass (280 kg), weight distribution (50/50), aerodynamic drag and lift, combined rotational inertia, and fixed drivetrain ratios. Lateral effects, tire deformation, camber, and suspension kinematics were neglected to isolate straight-line acceleration behavior

 Figure 2. RWD Simulink control model

Tire forces were modeled using Pacejka’s Magic Formula, with friction defined as a function of slip ratio. A PID controller regulated motor torque by comparing actual slip ratio to a 0.2 target value, adjusting torque to optimize tractive force

 Figure 3. Tuned Pacejka's magic formula

Results

The launch control system reduced excessive wheel slip compared to an open-loop torque request, improving traction utilization and longitudinal acceleration. The PID controller maintained slip near the 0.2 target, increasing stability and smoothing torque delivery

The AWD configuration demonstrated improved traction control flexibility due to independent front motor torque inputs, while RWD performance was more sensitive to load transfer and motor limits

 Figure 4. 4WD distance, velocity, and acceleration results

 Figure 5. 4WD friction results

 Figure 6. 4WD force results

Next Steps

Refine the motor model to reflect realistic torque–power curves and non-ideal behavior. Incorporate pitch and heave into the longitudinal load transfer model. Integrate measured vehicle data, rolling resistance, and drivetrain losses to improve simulation accuracy and better predict real-world performance