07 / Motion Profiling

Testing Profiles and Failure Modes

Tune profiled control safely and diagnose overshoot, lag, and saturation.

60 minAdvancedMotion Profiling

You will

01Identify overshoot, lag, and output saturation.
02Tune velocity and acceleration limits before aggressive PID.
03Add emergency stops and safe targets.

Why Testing Profiles and Failure Modes matters

This lesson is about planning motion before controlling it. A profile turns a sudden target jump into a time-based path of positions, velocities, and accelerations that a controller can follow more gently.

Starting point

Profile constraints are tuning constants too

If the requested profile is too aggressive, PID will saturate and the mechanism will lag. Sometimes the right fix is lower max velocity or acceleration, not more proportional gain.

Safety belongs in the test plan

A profiled arm or lift can still hit hard stops if constants or units are wrong. Test small moves first, clamp outputs, and keep a driver-controlled disable path.

Build path

Draw the motion first, then code it. Students should label acceleration, cruise, deceleration, total time, and target position before implementing a profiled mechanism. The code should regenerate the profile only when the target changes, then follow the current profile state each loop.

For this specific lesson, students should first restate the goal in robot terms, then identify the value or behavior they expect to observe, then run the smallest test that proves the idea. The lesson should feel like a guided lab: predict, run, observe, explain, and only then extend.

ProfileTelemetry.java · Java

telemetry.addData("profile x", state.x);
telemetry.addData("profile v", state.v);
telemetry.addData("actual", lift.getCurrentPosition());
telemetry.addData("error", state.x - lift.getCurrentPosition());
telemetry.addData("output", output);
telemetry.addData("saturated", Math.abs(output) >= 1.0);

Debugging and failure modes

Profiled systems fail when the requested motion is physically unrealistic or when the profile is restarted every loop. Saturated output, growing error, overshoot, and late arrival all point to different fixes. The lesson should make students name the failure mode before touching constants.

Checks

Small moves are tuned before full-range moves.
Saturation is visible in telemetry.
There is a tested emergency stop path.

Check your understanding

Module check

If output is saturated for most of the move, what should you consider first?

0 of 1 answered

References

Game Manual 0Community FTC programming, control, and robot design reference.FTC DashboardTelemetry, config variables, and tuning support.