Motion Profile (Accel/Decel) Calculator
Compute accel/decel time and peak velocity for trapezoidal/S-curve moves.
Move Parameters
Total Move Time
Motion Profiles in Automation
Motion profile calculators are essential tools for planning the trajectory of mechanical systems. By defining velocity, acceleration, and position over time, engineers can optimize movement for speed, smoothness, or both. The two most common profiles are Trapezoidal and S-Curve.
Trapezoidal vs. S-Curve Profiles
Trapezoidal Profile
A trapezoidal motion profile consists of three distinct phases: constant acceleration, constant velocity, and constant deceleration. Because the transition between these phases is instantaneous, the acceleration changes abruptly.
- Pros: Provides the fastest possible move time for a given maximum velocity and acceleration.
- Cons: The abrupt change in acceleration (theoretically infinite “jerk”) can excite high-frequency mechanical resonances, causing vibrations.
- Best For: Simple, fast, and non-critical movements where vibration is not a primary concern.
S-Curve (Jerk-Limited) Profile
An S-curve profile smooths out the acceleration and deceleration phases by introducing a limit on Jerk (the rate of change of acceleration). A full S-curve typically involves seven phases, ramping the acceleration up and down gradually.
- Pros: Minimizes mechanical wear, vibration, and noise by providing smooth transitions.
- Cons: Results in slightly longer move times and requires more complex computations.
- Best For: High-precision applications, delicate payloads, and systems with high inertia.
Key Motion Parameters
To calculate a motion profile, you must define the following limits:
- Target Distance: The total distance the load needs to move.
- Maximum Velocity (vmax): The top speed allowed during the constant velocity phase.
- Maximum Acceleration (amax): The highest allowable rate of speed increase or decrease.
- Maximum Jerk (j): For S-curves, the maximum rate at which acceleration can change.
Modern motion controllers (like PLCs or servo drives) typically handle the complex polynomial equations required for S-curves internally. You simply provide the target distance, vmax, amax, and jerk limits, and the controller generates the smooth trajectory.