Robot Vacuum Cleaner

Suppose you have a robot vacuum cleaner. After placing it on the floor, could it sweep the entire floor without map information? In other words, just by bumping the wall, could the robot accomplish the task?

Here is my demonstration video: Robot Vacuum Cleaner Simulation

Idea

The idea is simple. Just view the problem as solving a maze problem. We have to maintain going along with the wall and that left hand touches the wall. Meanwhile, we assume our right hand touches nothing. After sweeping a position, treat the position as a kind of virtual wall for termination condition.

Algorithm

1. Turn the direction to head to North.

2. Move forward until touch a wall.

   a. Assume robot's back is an empty position and record it as a possible empty position pos. For instance, if the robot's position is (x, y) and direction is North, the recorded position is (x+1, y).

   b. Turn right.

   c. Move forward. If the robot does not touch the wall, go to step (d). Otherwise, repeat step (b) and (c). Once, it makes turns 4 times, go to step (d).

   d. Turn left.

   e. Move forward. If the robot touches a wall, go to step 3. Otherwise, repeat step (d) and (e).

3. Sort all possible empty positions pos based on current position.

4. Pick a valid position from pos where it is not cleaned, not out of boundary and not a wall.

5. If there is no such valid position, in other words, the floor is fully sweeped.

6. If we can find a valid position, do a bfs to move current position to the valid position pos. The movements are on the recorded cleaned positions. Then, go to the first step.

• When it is a valid Move, we will record the position as a cleaned position.

Discussion

The behavior would look like circling the environment and the circle becomes smaller and smaller. However, it might produces several isolated sub-environment. This way, we perform step 3-6 to visit each possible isolated circles.

There is a trivial way to accomplish this task by dfs with backtracking. However, it might use more steps and turns!

How to run (MacOS)

g++ -std=c++11 Cleaner.cpp

./a.out ./map/map.txt

If you want to see a simple animation,

./a.out ./map/map.txt 1

I haven't tested in Linux and Windows, but I guess the code will work fine under Linux.

Question

1. If we accidentally replace the robot to other position, how do we deal with this situation?

   Initialize the cleaning process.

2. Could we extend the algorithm to 3D environment?

   We could view this problem as a multi-layered original problem. When a position is cleaned, record its top position as next level's dirty place. This way, after this floor is cleaned entirely, we can use the cleaned position of current floor and move toward next level's dirty position.

3. Suppose we have multiple robots. How can we modify the algorithm?

4. If the map has no boundary, how do we handle this problem?

   Set a virtual boundary.

5. What about there are moving obstacles in the environment?

6. What about there are "movable" obstacles in the environment?

   Since we only uses vacuum cleaner's bumper to accomplish the task, we cannot deal with movable obstacles after they are moved by the cleaner. The algorithm will treat the movable obstacles as empty spaces while moving the obstacles. Once, the cleaner cannot move the obstacle, the obstacle will be considered as a stuck space.