UT_RAMP — Rate-limited setpoint

Moves an output toward a target at a set rate: soft speed changes, gentle valve
moves, setpoint ramps for heating.

Pins

	Pin	Type	Default	What to wire
in	`In`	REAL	0.0	Target
in	`RateUp`	REAL	10.0	Units per `RateUnit` rising (0 = jump)
in	`RateDown`	REAL	10.0	Units per `RateUnit` falling (0 = jump)
in	`RateUnit`	UT_RATE_UNIT	UT_PER_SEC	The rates are per second (`UT_PER_SEC`), minute, hour or day, e.g. a temperature setpoint ramped in °C per minute
in	`Track`	BOOL	FALSE	Output follows `In` immediately (e.g. while stopped)
out	`Out`	REAL		The ramped value
out	`Ramping`	BOOL		`Out` ≠ `In`: still moving
out	`BadInput`	BOOL		`In` or a rate is not a number: `Out` is held

Out moves toward In at RateUp or RateDown and stops exactly on In. It
never overshoots, and a target reversed mid-ramp turns straight round.
A rate of 0 (or infinity) means no limit: Out jumps. The sign of a rate is
ignored, so −5 acts as 5.
After a restart Out starts at 0 and ramps up to In. Wire Track to start
from In instead; when Track goes FALSE the ramp carries on from there.
Timing uses real elapsed time, so the rate is the same at any task interval,
and very slow rates (0.001 per second) still add up exactly.
A NaN or infinite In, or a NaN rate, holds Out where it is and sets
BadInput (Ramping is FALSE meanwhile). The time it lasted does not count,
so Out does not jump to catch up afterwards. Track does not follow a bad In.

SpeedRamp(In := SpeedSP, RateUp := 5.0, RateDown := 10.0, Track := NOT Running);
DriveSpeed := SpeedRamp.Out;   (* Hz, 5 Hz/s up, 10 Hz/s down *)