Setpoint signal

Reference signal is a signal that will be used as target value in control systems. Typical occurrencies of reference signals in GD products are:

• Position reference
• Velocity reference
• Torque reference

I.e. position reference value may be "1234" which could mean a target position of 1234 mm in some linear actuator. Or torque reference of 5.0 could mean that motor is asked to produce 5 Nm torque.

Physical reference signal types

Reference signals may have several representations in real world such as:

• Analog reference signal
• Pulse and direction signals
• PWM signal
• Serial communication command

In these cases there will be a conversion between input and output units. For example when using +/-10V reference as velocity reference, the relation betveen input to output types could be 1 Volt per 100 rpm (or any other scale).

Reference signal characteristics

	Analog	Pulse & dir or Quadrature	PWM	Network
Scale & range	Absolute (limited)	Incremental (infinite)	Absolute (limited)	Absolute (near infinite) Incremental (infinite)
Reference uses in motion control	Torque, velocity	Position, velocity	Torque, velocity	Position, torque, velocity
Pros	Widely used Easy to measure	Widely used Exact Noise robust	EMI noise robust Precise	High resolution & accuracy Reduce wiring More functions than just reference
Cons	EMI noise sensitive Offset & gain errors	Limited resolution at low frequency Need reference zeroing because incremental	Various "standards", sometimes incompatible	Many standards Usually incompatible with other standards

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