Safe Control Synthesis for Multicopter via Control Barrier Function Backstepping

TL;DR

This paper introduces a novel safe control method for multicopters using control barrier functions, reformulating dynamics to handle complex behaviors and ensuring safety constraints are maintained through quadratic programming.

Contribution

It presents a time-varying safe backstepping controller that does not rely on cascade control, capable of handling multiple safety constraints simultaneously.

Findings

Controller maintains safety constraints in simulations

Handles mixed-relative-degree and non-strict-feedback dynamics

Does not require cascade control design

Abstract

A safe controller for multicopter is proposed using control barrier function. Multicopter dynamics are reformulated to deal with mixed-relative-degree and non-strict-feedback-form dynamics, and a time-varying safe backstepping controller is designed. Despite the time-varying variation, it is proven that the control input can be obtained by solving quadratic programming with affine inequality constraints. The proposed controller does not utilize a cascade control system design, unlike existing studies on the safe control of multicopter. Various safety constraints on angular velocity, total thrust direction, velocity, and position can be considered. Numerical simulation results support that the proposed safe controller does not violate all safety constraints including low- and high-level dynamics.