  The contribution of this paper is the application of compound state-triggered
constraints (STCs) to real-time quad-rotor path planning. Originally developed
for rocket landing applications, STCs are made up of a trigger condition and a
constraint condition that are arranged such that satisfaction of the former
implies satisfaction of the latter. Compound STCs go a step further by allowing
multiple trigger and constraint conditions to be combined via Boolean "and" or
"or" operations. The logical implications embodied by STCs can be formulated
using continuous variables, and thus enable the incorporation of discrete
decision making into a continuous optimization framework. In this paper,
compound STCs are used to solve quad-rotor path planning problems that would
typically require the use of computationally expensive mixed-integer
programming techniques. Two scenarios are considered: (1) a quad-rotor flying
through a hoop, and (2) a pair of quad-rotors carrying a beam-like payload
through an obstacle course. Successive convexification is used to solve the
resulting non-convex optimization problem. Monte-Carlo simulation results show
that our approach can reliably generate trajectories at rates upwards of 3 and
1.5 Hz for the first and second scenarios, respectively.
