How they work

The stepping motor based linear actuator for direct control of hydraulic valves without the requirement of a pilot valve is a very robust system as can be seen in the drawing below.
 
Inside the 37mm wide IP67 housing is fitted a stepping motor, electronic controller, gearing (for converting the rotary movement to a linear movement with the additional benefit of amplified torque output), rack and connector (with CAN+, CAN-, Ground & 12Vdc pins). The housing is designed such that two actuators can be fitted next to each other whilst keeping within the 37mm width requirement for valve blocks.

This stepping motor based system provides high system rigidity and immunity to shocks, vibrations and load changes especially when compared to a proportional magnet system normall incorporated in mobile hydraulic systems.

Stiffness of a proportional magnet	Stiffness of a stepping motor

As can be seen from the above two graphs, for a change in force for the proportional magnet system (equates to a change in torque for the stepping motor system) the stepping motor system provides a much higher degree of stiffness (smaller deviation) for the same comparable change in load.