Industrial Engineer · phase 11 of 16 · noun
Closed-Loop Control
Motor control that uses encoder or resolver feedback to regulate shaft speed, torque, or position.
The Explain card
- Plain English
- Closed loop means the drive measures the shaft with an encoder or resolver and corrects its output until the measurement matches the command. The feedback closes the loop.
- Example
- A winder must hold speed within a tenth of a percent as the roll builds. An encoder on the motor reports actual speed thousands of times a second and the drive trims its output to match.
- Why it matters
- Feedback buys accuracy, full torque at zero speed, and the ability to hold a load still, which is what hoists and positioning need. It also adds a cable, a device that can fail, and a fault the drive raises the moment the feedback disagrees with the model.
- Hook
- Measure, compare, correct, repeat.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
During commissioning, the engineer selects closed-loop control and verifies that the encoder pulse train reaches the VFD feedback terminals.
Why these words
- closed Old French clos, shut marks the loop as complete rather than interrupted
- loop Middle English loupe, a bend or loop names the returning path within the compound
- control Anglo-French contrerolle, a counter-register used for checking serves as the head noun and identifies the engineering function
Where it came from
- Origin
- English engineering compound formed from closed, loop, and control
- Entered the language
- 1930s
- What changed
- Loop broadened from a physical bend or circuit to an abstract signal path, while closed marked that path as complete in control-engineering terminology.
How it is spelled
- Pattern
- Closed-loop is hyphenated because the two words jointly modify the following noun.
- Pattern
- Closed retains the regular past-participle suffix -ed.
Spelled like
- open-loop control
- closed-circuit television
- real-time control
Broken into chunks
-
closed
- close
- closure
-
loop
- loopback
- loophole
-
control
- controller
- controllable
What it sits beside
Same subject
- PID controller
- encoder feedback
- resolver
- variable frequency drive
Same shape
- open-loop control
- closed-loop system
- closed-loop transfer function
feedback devices
- encoder
- resolver
control architectures
- open-loop control
- closed-loop control
Where it sits in the deck
Phase 11: VFD Control Modes and Tuning
How a drive decides what to send the motor, from plain volts per hertz up to closed loop vector control, and how each mode is tuned.
