MPCC++: Model Predictive Contouring Control for Time-Optimal Flight with Safety Constraints (RSS'24)

Quadrotor flight is an extremely challenging problem due to the limited control authority encountered at the limit of handling. Model Predictive Contouring Control (MPCC) has emerged as a promising model-based approach for time optimization problems such as drone racing. However, the standard MPCC formulation used in quadrotor racing introduces the notion of the gates directly in the cost function, creating a multi-objective optimization that continuously trades off between maximizing progress and tracking the path accurately. This paper introduces three key components that enhance the state-of-the-art MPCC approach for drone racing. First and foremost, we provide safety guarantees in the form of a track constraint and terminal set. The track constraint is designed as a spatial constraint which prevents gate collisions while allowing for time optimization only in the cost function. Second, we augment the existing first principles dynamics with a residual term that captures complex aerodynamic effects and thrust forces learned directly from real-world data. Third, we use Trust Region Bayesian Optimization (TuRBO), a state-of-the-art global Bayesian Optimization algorithm, to tune the hyperparameters of the MPCC controller given a sparse reward based on lap time minimization. The proposed approach achieves similar lap times to the best-performing RL policy and outperforms the best model-based controller while satisfying constraints. In both simulation and real world, our approach consistently prevents gate crashes with 100% success rate, while pushing the quadrotor to its physical limits reaching speeds of more than 80km/h.

Reference:
M. Krinner, A. Romero, L. Bauersfeld, M. Zeilinger, A. Carron, D. Scaramuzza,
"MPCC++: Model Predictive Contouring Control for
Time-Optimal Flight with Safety Constraints",
Robotics, Science and Systems, 2024
PDF: https://rpg.ifi.uzh.ch/docs/RSS24_Kri...

For more info about our research on:
Agile Drone Flight: https://rpg.ifi.uzh.ch/aggressive_fli...
Drone Racing: https://rpg.ifi.uzh.ch/research_drone...

Affiliations:
A. Romero, L. Bauersfeld, and D. Scaramuzza are with the Robotics and Perception Group, Dep. of Informatics, University of Zurich, and Dep. of Neuroinformatics, University of Zurich and ETH Zurich, Switzerland
http://rpg.ifi.uzh.ch/

M. Krinner, M. Zeilinger, A. Carron are with the Institute for Dynamics Systems and Control, ETH Zurich, Switzerland
https://idsc.ethz.ch/