Electro-Hydraulic Motion Controllers Enable Breakthroughs in Machine Productivity and Reduce Lifecycle Costs

March 28, 2008
New electro-hydraulic control systems are available to empower new machines or give new life to old ones

Manufacturers are under ever-increasing pressure to improve the productivity of their machines while decreasing costs. Hydraulics remains the power of choice for heavy-duty machinery, but older hydraulic control systems often lack the precision to produce highly accurate and repeatable motion, and high maintenance costs for old machines can further put machine owners at a disadvantage. The picture is not as bleak as it may seem, however, because new electro-hydraulic control systems are available to empower new machines or give new life to old ones.

Position and pressure/force control

Certain hydraulic equipment, such as presses or injection molding machines, can benefit from controlling the pressure or force exerted by an actuator in addition to its position. The new generation of electro-hydraulic motion controllers, combined with precise position feedback devices such as magnetostrictive linear displacement transducers (MLDTs), can achieve precise positioning of hydraulic actuators that was not possible before. And methods for controlling position-to-pressure or position-to-force transitions have advanced significantly as well.


In the past, presses often used pressure relief valves to limit the pressure used to apply force, but there is a flaw in this technique due to net force considerations. Pistons have two sides and a pressure relief valve only reacts to the pressure on one side of the piston. Since there is pressure on both sides of the piston the applied force is not determined by the pressure on one side of the piston.