Drive a Path on Paper or in Simulation

A path is a sequence of poses, not just a list of motor commands.

A pose combines position and orientation.

For a flat floor, we often represent pose as:

x, y, heading

Path plan

Suppose the robot must:

1. start at (0, 0, 0°);
2. drive to (1, 0, 0°);
3. turn left;
4. drive to (1, 1, 90°).

A command list might achieve that, but the path specification tells us what success means.

Mark checkpoints

Create checkpoints that can be measured.

Now a simulation or physical trial can produce comparable evidence.

Failure case: correcting from the final point only

Suppose the robot finishes close to (1,1) but takes a huge arc through an obstacle zone.

Final position alone says "good." Path evidence says "unsafe."

A robotics test should measure what the mission actually constrains.

Run the mission

Use graph paper, a spreadsheet model, a simulator, or supervised robot data.

Create:

• planned path;
• at least four pose checkpoints;
• observed/simulated path;
• largest deviation;
• likely cause.

If using paper only, deliberately add one wheel-distance error and propagate it through the later checkpoints.

You will see an important robotics pattern: small motion errors accumulate into pose errors.

Predict the pose before running the path

A useful path test starts with a known pose.

start: x = 0 m, y = 0 m, heading = 0°

Now define three segments:

1. drive straight 1.0 m;
2. rotate 90° left;
3. drive straight 0.5 m.

The expected final pose is approximately:

x = 1.0 m
y = 0.5 m
heading = 90°

That answer gives you something concrete to compare with simulation or physical data.

Separate path error from control error

If the robot finishes at (0.90, 0.42), several causes are possible:

• wheel-distance conversion is wrong;
• a wheel slipped;
• turn control undershot;
• starting pose was not actually zero;
• the motion command was wrong;
• pose estimation accumulated error.

Do not immediately rewrite the path.

Record checkpoints after each segment. If segment 1 is already short, the turn is not the first problem. If position is correct before the rotation and wrong afterward, investigate the turn and heading estimate.

A path becomes diagnosable when you can locate where the error first appears.