Introduction to SMACH

SMACH (pronounced as smash) is a Python-based library that helps us handle complex robot behaviors. It is a standalone Python tool that can be used to build hierarchical or concurrent state machines. While its core is ROS-independent, wrappers are written in the smach_ros package (http://wiki.ros.org/smach_ros?distro=melodic) to support integration with ROS systems via actions, services, and topics. SMACH is best useful when you're able to describe robot behaviors and actions more explicitly (like in our waiter robot analogy-state machine diagram). SMACH is a simple and wonderful tool to use and define state machines and is quite powerful when used in combination with ROS actions. The resultant combination can help us build more sophisticated systems. Let's look at some of its concepts in detail to help understand SMACH in more detail.

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