Industrial Engineer · phase 12 of 16 · noun
S-Curve
Ramp profile that rounds acceleration changes to reduce mechanical shock and jerk.
The Explain card
- Plain English
- An S curve rounds the corners of a ramp. Instead of jumping straight to full acceleration and straight off it again, the drive eases in and eases out, so the rate of change of acceleration is limited.
- Example
- A conveyor of stacked cartons starts with an S curve. The stacks stay upright, where a straight ramp would tip them at the moment the belt jerked into motion.
- Why it matters
- The jerk at the start and end of a linear ramp is what breaks gearboxes, spills liquid and shakes elevators. An S curve trades a little ramp time for a smooth start, and on anything carrying people or delicate product it is worth every second.
- Hook
- Smooth on, smooth off.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
The drive engineer selected an S-curve for the conveyor speed reference before tuning acceleration time and testing the loaded motor.
How it is built
- S letter element indicates resemblance to the letter's shape
- curve base a continuously bending line or plotted path
Where it came from
- Origin
- English descriptive compound formed from the letter name S and curve
- Entered the language
- 19th century
- What changed
- First used for S-shaped lines and paths, then adopted for similarly shaped plotted transitions in technical fields.
How it is spelled
- Pattern
- The capital letter S is joined to curve with a hyphen.
- Pattern
- The second element remains lowercase.
Spelled like
- S-bend
- S-shaped
Broken into chunks
-
S
- S-bend
- S-shaped
-
curve
- curved
- curvature
What it sits beside
Same subject
- acceleration time
- deceleration time
- jerk limit
- speed reference
Same shape
- J-curve
- U-curve
VFD motion profiles
- linear ramp
- S-curve
letter-shaped curves
- S-curve
- J-curve
- U-curve
Where it sits in the deck
Phase 12: VFD Commands, References, and Stopping
Starting, referencing and stopping, including the several very different things a drive can mean by the word stop.
