Cleanup root README

README.md

@@ -1,111 +1,75 @@
 # Asteroid Mining Simulation
 
-## Overview
-1. Excavator bot navigates (using a Nav2 plan) to mining site
+This is a proof of concept project that combines multiple technologies.
+
+The aim is to investigate the maturity of these technologies in the context of a simulated multi-robot asteroid mining scenario.
+
+Robot Types: (inspired by [Offworld](https://www.offworld.ai/products))
+  - Excavator
+  - Collector
+  - (Surveyor)
+  - (Dozer)
+  - (Hauler)
+  - (Fixer)
+
+## Mission Plan
+1. Excavator bot navigates to mining site using Nav2
 1. Excavator bot starts mining
    1. MoveIt2 + Gazebo simulation plans and executes mining motion
    1. Upon success, Gazebo triggers Bevy to start spawning resources
 1. Collector bot collects resources
 1. Collector bot brings resources back to refinery
+1. Rovers automatically goes to charging station when low battery.
 
 ## Technologies Used
-- Bevy (Rust)
-- `ros2-rust`
-- Space ROS
-- Gazebo
-- SMACC2
-- BehaviorTree.CPP
-
-## Macro Sim (Bevy)
-### Entities
-- Rovers
-  - Base
-  - Tool (inspired by [Offworld](https://www.offworld.ai/products))
-    - Excavator
-    - Collector
-    - (Surveyor)
-    - (Dozer)
-    - (Hauler)
-    - (Fixer)
-- Mining site
-- Refinery/Factory
-- Solar Panels
-- Command Center
-
-### Components
-- Health
-- Tool Slot
-- Capacity
-
-### Systems
-- Degradation
-- Pickup Tool
-- Drop Tool
-- Tool Operation
-- Natural Disaster
-- Collisions
-- Base motion
-- Gravity
-
-### UI
-- Select Rover
-  - Remote Control
-  - Switch Mode
-
-## Rovers (Space ROS)
-### Topics
-Publish:
-- Command Velocity
-- ~~Battery Level~~
-
-Subscribe:
-- ~~Costmap~~
-
-### Services
-- Set Nav Target (PoseStamped)
-- ~~Set battery level~~
-
-### Actions
-- ~~Go To Position~~
-- ~~Excavate / Operate Tool~~
-
-### Hierarchical Finite State Machine Behavior Tree Hybrid (HFSMBTH)
-<https://www.youtube.com/watch?v=Qq_xX1JCreI&t=1167s>
-
-SMACC2 + BehaviorTree.CPP
-
-States:
-- Autonomous
-  1. Go to worksite
-  1. Do work
-  1. Repeat
-- Low Battery
-  1. Go to charging station
-  1. Charge
-- Manual
-  1. Execute
-  1. Wait for X seconds
-  1. Go back to Autonomous
-
-## Micro Sim (Gazebo)
-Use MoveIt2, Nav2 and Gazebo to simulate certain robot behaviors
-- Drilling motion
+- [x] [Bevy](https://bevyengine.org/)
+- [x] [`ros2-rust`](https://github.com/ros2-rust/ros2_rust)
+- [x] [Space ROS](https://space.ros.org/)
+- [x] [Hierarchical Finite State Machine Behavior Tree Hybrid (HFSMBTH)](https://www.youtube.com/watch?v=Qq_xX1JCreI&t=1167s)
+  - [x] [BehaviorTree.CPP](https://github.com/BehaviorTree/BehaviorTree.CPP)
+  - [x] [HFSM2](https://github.com/andrew-gresyk/HFSM2)
+- [ ] Gazebo
+- [ ] Nav2
+- [ ] MoveIt2
 
 ## TODO
-- [] Set up CI/CD & linters
+- [ ] Set up CI/CD & linters
 - [x] Bare minimum macro sim
   - [x] Single excavator with manual controls
   - [x] Interface with ROS using `ros2-rust`
 - [x] Set up robot running Space ROS
-- [] Create HFSMBTH
-- [] Set up micro sim (Gazebo)
-- [] Set up MoveIt2
-- [] Set up Nav2
+- [ ] Create HFSMBTH
+  - [x] Create FSM
+  - [ ] Create BT
+- [ ] Macro Sim UI
+- [ ] Multiple rovers
+- [ ] Set up micro sim (Gazebo)
+- [ ] Set up MoveIt2
+- [ ] Set up Nav2
+
+## Macro Sim (Bevy + `ros2-rust`)
+The asteroid and rover kinematics is simulated using Bevy, a popular Rust game engine that uses an ECS architecture similar to Gazebo.
+
+The asteroid is treated as a sphere and the rover is assumed to be constrained to the surface of the asteroid.
+The rover velocity is forward integrated and reprojected onto the surface of the sphere via geodesic calculations.
+
+## Rovers (Space ROS + HFSMBTH)
+The rover is controlled using Space ROS to mimic what a real space rover would use.
+
+The behavior is coordinated using a HFSMBTH which aims to combine the benefits of hierarchical finite state machines (HFSM) and behavior trees (BT).
 
 ## FAQ
 Why Bevy and not Gazebo?
 1. I wanted an excuse to learn the Bevy engine.
 1. Radial (planetary) gravity
 1. I plan to scale this to large number of robots and didn't want to simulate the physics of every single one.
-   Note that Gazebo is still used when simulating the sensor and robot arm during arm motion planning.
-1. [Gazebo vs *\<insert game engine\>*](https://discourse.ros.org/t/why-do-we-use-gazebo-instead-of-unreal-or-unity/25890/15).
+   Note that Gazebo will still be used when simulating the sensor and robot arm during arm motion planning.
+
+Why HFSMBTH?
+- (Reiterating key points from talk linked above)
+
+  BTs are great at modelling sequences of fallible actions but awful at modelling cyclical behavior (BTs are directed acyclic graphs).
+
+  FSMs are great at modelling cyclical behavior but awful at modelling sequences of fallible actions (fallback/retry adds lots of unnecessary states).
+
+  Combine them both to get the best of both worlds.