Autonomous Bus Docking for Optimal Ride Comfort of Standing Passengers

This paper studies the optimization of ride comfort during the maneuver of bus docking at a stop station. We propose an analytical comfort model that considers the coupled and nonlinear effect of acceleration and jerk levels on the comfort perceived by standing bus passengers. This is studied through offline path planning by formulating the docking problem as a Nonlinear Program while implementing the comfort model to minimize discomfort. Geometry constraints are imposed on several points on the vehicle contour to ensure that the bus stays within the road bounds and docking is performed safely. The offline solution is then used as a reference in a real-time control event using a Volvo 7900 autonomous bus. To gain perspective, the measurements from the field test were compared to those of a human-driven trajectory. The results indicate that only around $\mathbf{\SI{1.7}{\%}}$ of bus occupants will experience discomfort with the proposed model, in comparison to $\mathbf{\SI{60}{\%}}$ in a human-driven bus, while respecting road and vehicle constraints and accurately docking within an acceptable predefined distance from the curb. We also show through simulations that in comparison to our proposed model, the traditional method of quadratic penalties for comfort modeling produces higher discomfort levels and prevents some trajectories characterized by high acceleration and jerk. Such trajectories can be permitted and comfortable using our approach.