Introduction
When executing a 120-degree move in 1 second, two common motion profiles—trapezoidal and triangular—each offer different benefits depending on system constraints and motion priorities.
Motion Profile Breakdown
1️⃣ Trapezoidal Move (1/3 Accel, 1/3 Constant Velocity, 1/3 Decel)
- Smooth Transition: Includes a constant velocity phase, making movement more controlled.
- Lower Peak Acceleration: Reduces mechanical stress on the system.
- Ideal for Continuous Motion: If the system frequently moves, a trapezoidal profile minimizes wear.
2️⃣ Triangular Move (1/2 Accel, 1/2 Decel)
- No Constant Velocity Phase: Accelerates directly to peak speed and then decelerates.
- Higher Peak Acceleration: Moves aggressively, reaching peak velocity faster.
- Best for Minimizing Move Time: Ideal for high-speed applications where reducing time is crucial.
Peak RPM Calculation & Derivation
We determine peak angular velocity (degrees/sec) before converting to RPM:
🔹 Trapezoidal Move Peak RPM
- The total move is 120° in 1 sec.
- The profile consists of 1/3 accel, 1/3 constant velocity, and 1/3 decel.
- Since constant velocity occurs in the middle third, peak velocity is:
- Converting to RPM:
🔹 Triangular Move Peak RPM
- The total move is 120° in 1 sec.
- The profile consists of 1/2 accel, 1/2 decel with no constant velocity phase.
- Peak velocity occurs at midpoint of the move, so:
- Converting to RPM:
Final Comparison Table
| Motion Profile | Peak RPM |
|---|---|
| Trapezoidal | 30 RPM |
| Triangular | 40 RPM |
The Triangular Move reaches a higher peak RPM since it doesn’t include a constant velocity phase, requiring more aggressive acceleration.
Final Comparison Table
| Feature | Trapezoidal Move | Triangular Move |
|---|---|---|
| Constant Velocity Phase | Yes | No |
| Peak Acceleration | Lower | Higher |
| System Stress | Lower | Higher |
| Move Duration | Slightly Longer | Shorter |
| Best for | Smooth, controlled motion | Fastest move in shortest time |
Conclusion
- If you need smoother motion and less stress, go with trapezoidal.
- If minimizing move time is your priority and the system can handle higher acceleration forces, triangular is preferable.