The SMACH High-Level Executive

A Python application programming interface (API) called SMACH, based on hierarchical concurrent state machines, allow executives to be controlled by a higher level task-planning system. SMACH is a ROS independent library that can be used to build hierarchical and concurrent state machines and any other task-state container that adheres to the provided interfaces. SMACH States represent states of execution, each with some set of potential outcomes, and implement a blocking execute function, which runs until it returns a given outcome. A simple execution policy the SMACH Concurrence executes one state at a time in series and executes more than one state simultaneously. Each SMACH container has a locally scoped dictionary of user data that can be accessed by each of its child states, allowing states to access data that was written by previously executed states.