You might take a look at the hobby RC suppliers - that field has come a
long way. Try www.spektrumrc.com for an advanced controller ($160) and a
"speed control" (what I would call a motor driver) ($170) to run a
brushless servomotor controlling the position of the spool valve. Not a
solenoid valve - sorry.

All bolt/plug together - no custom hardware or software. There are also
dead-man modules that will take the motor to a defined position in case
the radio link is lost.
--
Fred R
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