Added my design document for D* lite

documents/design/d_star_lite.md

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+# Project Title
+
+*Issue #567*
+(What GitHub issue is associated with this project)
+
+**Author:**
+- Christopher Lo
+
+## The Problem
+
+- The ROS package move_base_flex serves to allow the robot to utilize an enhanced version of 
+the planner, controller, and recovery plugin ROS interfaces:
+
+- There is a better path planner algorithm, D* lite which builds upon the Lifelong
+Planning A* (LPA) algorithm and D* algorithms. 
+
+- Thus, to resolve this issue, I will be replacing the currently used A* algorithm with the 
+better D* lite algorithm in order to improve Jessii's path planning on the obstacle course.
+
+## Proposed Solution
+
+- Read a research paper on D* lite by researchers Sven Koenig and
+Maxim Likhachev in order to understand the technical details behind Lifelong Planning A* and D* Lite for
+robot navigation in unknown terrain. 
+
+- Includes goal-directed navigation and the mapping of unknown terrain, concepts that will be useful to 
+understand when implementingthe D* lite algorithm. 
+
+- Read up on move_base_flex, a ROS package responsible for the planning, control, and recovery features
+for Jessii.
+
+- Read up on the parameters used by the method that will contain the D* lite algorithm implementation within
+the software base.
+
+- Create an implementation using the parameters and concepts learned from the D* lite research paper.
+
+- Run tests using a simulator and see if the planner works better than the A* algorithm currently in place.
+
+## Questions & Research
+
+- I do not know much about D* Lite (which is why I will be reading the research paper to extract
+information that will be essential for creating a working implementation of the algorithm). 
+
+- I will need to read up on A* and LPA (Lifelong Planning A*) in order to understand why D* Lite 
+is better than these algorithms and how I can seamlessly reap the benefits.
+
+Link to D* Lite paper: https://aaai.org/Papers/AAAI/2002/AAAI02-072.pdf
+
+## Overall Scope
+
+### Affected Packages
+
+- The parts of the software that I will have to change are the:
+
+- move_base_flex wrapper_global_planner.h file containing the makePlan() method that will ultimately be 
+responsible for holding my D* lite algorithm implementation.
+
+- Planner core file within the navigation folder in order to render a map of the unknown terrain that Jessii
+will be crossing and using to calculate a path with the D* lite algorithm.
+
+### Schedule
+
+Subtask 1 (11/24/2019): Read up on the D* Lite research paper. (11/24/2019)
+
+Subtask 2 (11/31/2019): Read up on move_base_flex package and methods used in the body of the method containing the 
+D* Lite algorithm. 
+
+Subtask 3 (01/01/2020): Create an implementation of the D* Lite algorithm in the method. (01/01/2020)
+
+Subtask 4 (01/10/2020): Run tests on the newly implemented D* Lite algorithm using a simulator or actual Jessii.
+
+Code Review (1/15/2020): Code/result will be ready to review
+