5a - Robot Navigation Flashcards
What is the definition of navigation?
The process of determining and maintaining a path or trajectory to a goal destination
What are 3 key questions in Robot Navigation?
Where am I?
Where do I go?
How do I go there?
What does a robot need to be able to be able to answer the 3 questions of Robot Navigation?
A model of the environment
To perceive and understand the environment
To find its position and situation in the environment
To plan and execute the movement
What are the 2 ways in which a model of the environment can be provided?
Given or autonomously built
Name 2 types of path planning and give an example
Global path planning (graph search) and local path planning (collision avoidance)
What is global navigation?
Where the robot is not told its initial position and the position should be estimated from scratch
What is position tracking, or continuous localisation?
Where the robot knows its initial position
Name 3 types of global navigation strategy
Recognition triggered response, topological route and survey
What is recognition triggered response?
Local navigation triggered by the last recognised place
What is topological route?
Based on topological maps (graphs where places are nodes and edges are routes connecting them, go geometric information
What is Survey?
All known places and spatial relations are embedded in the same frame of reference, the robot can discover new paths
Name 4 types of local navigation strategy
Search, direction following, aiming, guidance
What is Search?
The robot can move and recognise its arrival at the goal
What is Direction following?
Compass direction or trail following (find goal from one direction)
What is Aiming?
Taxis to source, using landmarks (can find a salient goal from a catchment area)
What is Guidance?
Information by surroundings
How can you use vision as a local navigation strategy?
Use a visual cue at the goal reactively, detect goal from a distance and maintain a course towards it, also called landmark navigation/beaconing
What are some problems with beaconing?
Cues must be visible, they may be temporarily obscured or have a short range
What is the Visual Homing Snapshot model?
Before leaving home take a visual snapshot, when homing move to reduce the mismatch between current views and the initial snapshot, repeat until the home is reached
What are 3 problems with the Snapshot Model?
How to define a landmark
How to match landmarks between current scene and memory
You must be aligned
What is loop closure?
The ability to recognise a location even if perceived from a different pose (also known as the kidnapped robot problem)
What is feature based place recognition?
Using visual features to describe a location
Matching the features and descriptors current visible with a list of those at previously visited locations
Also called bag of words
What is the ALV visual homing model?
Average Landmark Vector
Before leaving home take a snapshot, point a unit vector to each surrounding landmark, compute ALV and store
Then use vector subtraction to generate the home vector
home vector = current ALV - home ALV
Name 3 possible navigation strategies for robots
Navigation by vision and compass
Navigation using landmarks as beacons
Navigation by position tracking
Discuss the requirements of a general-purpose solution to the navigation problem in mobile robotics
A representation of the navigable space (as a graph or grid derived from global map of environment)
A path planner (A*/Dijkstra algorithms) to find best route to goal location
An autopilot to drive between waypoints taking into account the robot’s kinematics and dynamics
Avoid unexpected obstacles on the way
