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Robot Navigation Basics
Line following, obstacle avoidance, waypoints, and mapping
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Robot navigation is the process a robot uses to decide where it is, where it should go, and how to move safely. In a robotics classroom or competition, navigation helps a wheeled robot follow lines, avoid obstacles, reach targets, and explore an unknown field. Good navigation combines sensors, software, and motion control. These basics are important because even a simple robot must constantly turn sensor data into driving decisions.
A robot usually navigates in a loop: sense the environment, decide on an action, move, then sense again. Line following uses light or color sensors to stay near a marked path, while obstacle avoidance uses distance sensors to stop or turn when something is too close. Waypoint navigation sends the robot between planned points using distance, direction, or position estimates. Mapping is more advanced because the robot builds a model of the space and then plans a path through it.
Key Facts
- Navigation loop: sense, decide, move, repeat.
- Speed equation: v = d/t, where v is speed, d is distance, and t is time.
- Turn rate equation: omega = theta/t, where omega is angular speed, theta is turn angle, and t is time.
- Distance from wheel rotations: d = pi D N, where D is wheel diameter and N is wheel rotations.
- Obstacle rule example: if measured distance < safety distance, stop or turn.
- Waypoint path distance on a grid: d = sqrt((x2 - x1)^2 + (y2 - y1)^2).
Vocabulary
- Sensor
- A device that measures something about the robot or its environment, such as light, distance, color, or rotation.
- Line following
- A navigation method where a robot uses a light or color sensor to stay on or near a marked line.
- Waypoint
- A marked target position that a robot drives toward as one step in a larger route.
- Obstacle avoidance
- A behavior in which a robot detects objects in its path and changes motion to avoid hitting them.
- Map
- A stored model of the robot's surroundings that can show walls, open spaces, obstacles, and possible paths.
Common Mistakes to Avoid
- Ignoring sensor placement, because a line sensor too far from the ground or off center may read the path late or miss it completely.
- Driving too fast for the sensor update rate, because the robot may move past a line, wall, or waypoint before the program can react.
- Treating wheel rotations as perfect distance, because slipping wheels, uneven floors, and battery changes can make odometry inaccurate.
- Using only one navigation rule for every situation, because line following, obstacle avoidance, waypoint driving, and mapping solve different problems.
Practice Questions
- 1 A robot drives 2.4 m in 6 s while following a line. What is its average speed in m/s?
- 2 A robot wheel has a diameter of 6 cm. If the wheel turns 5 full rotations, about how far does the robot travel in centimeters? Use d = pi D N and pi = 3.14.
- 3 A robot must cross a practice field with a line path, two obstacles, three marked waypoints, and one unknown blocked area. Explain which navigation strategies it should use and in what order.