Skill-based Programming Framework for Composable Reactive Robot Behaviors

This paper introduces a constraint-based skill framework for programming robot applications. Existing skill frameworks allow application developers to reuse skills and compose them sequentially or in parallel. However, they typically assume that the skills are running independently and in a nominal condition. This limitation hinders their applications for more involved and realistic scenarios e.g. when the skills need to run synchronously and in the presence of disturbances. This paper addresses this problem in two steps. First, we revisit how constraint-based skills are modeled. We classify different skill types based on how their progress can be evaluated over time. Our skill model separates the constraints that impose task-consistency and the constraints that make the skills progress i.e. reaching their end conditions. Second, this paper introduces composition patterns that couple skills in parallel such that they are executed in a synchronized manner and reactive to disturbances. The effectiveness of our framework is evaluated on a dual-arm robotics setup that performs an industrial assembly task in the presence of disturbance.