Reach-avoid problems involve driving a system to a set of desirable configurations while keeping it away from undesirable ones. Providing mathematical guarantees for such scenarios is challenging but have numerous potential practical applications. Due to the challenges, analysis of reach-avoid problems involves making trade-offs between generality of system dynamics, generality of problem setups, optimality of solutions, and computational complexity. In this paper, we combine sumof-squares optimization and dynamic programming to address the reach-avoid problem, and provide a conservative solution that maintains reaching and avoidance guarantees. Our method is applicable to polynomial system dynamics and to general problem setups, and is more computationally scalable than previous related methods. Through a numerical example involving two single integrators, we validate our proposed theory and compare our method to Hamilton-Jacobi reachability. Having validated our theory, we demonstrate the computational scalability of our method by computing the reach-avoid set of a system involving two kinematic cars.
I. IReach-avoid problems are prevalent in many engineering applications, especially those involving strategic or safetycritical systems. In these situations, one aims to find a control strategy that guarantees reaching a desired set of states while satisfying certain state constraints, all while accounting for unknown disturbances, which may be used to model adversarial agents. Reach-avoid sets capture the set of states from which the above task is guaranteed to be successful. Reach-avoid problems are challenging to analyze due to the asymmetric goals of the control and disturbance, leading to non-convex, max-min cost functions [1]- [3]. Due to the complexity of the cost function, dynamic programmingbased methods for computing reach-avoid sets on a grid representing a state space discretization, such as Hamilton-Jacobi (HJ) formulations, have been popular and successful [1], [2], [4].One specific class of reach-avoid problems is the reachavoid game, in which the system consists of two adversarial players or teams. The first player, the attacker, assumes the role of the controller, and aims to reach some goal. The other player, the defender, assumes the role of the disturbance, and tries to prevent the attacker from achieving its goal. In [5], [6], the authors analyzed the two-player game of capturethe-flag by formulating it as a reach-avoid game, and then