Simple Hydraulic Motion Control using Analog input

I suggest an RMC75E-MA1-A2. This will give you one +/-10 V output to go to a valve, one feedback input of type SSI or Start/Stop or PWM, and two analog inputs, of which you can use one for the 0-10 V signal.

I recommend the following system components:

  • A linear, high-performance valve. This will make the setup easy and give you great control. What kind of accuracy do you need? This would dictate whether you need a good valve or a very good valve. See Hydraulic Valves
  • SSI position feedback sensor. If you are purchasing a new hydraulic cylinder, get a cylinder designed for sensor that goes inside the cylinder. For sensor recommendations, see SSI Linear Displacement Transducers
  • Mount the valve on the cylinder. This will give the best control. If the valve is far from the cylinder, the compression of the oil (and hose, if it has that) will act as a spring, making control more difficult.
  • Use an accumulator. This will help provide constant system pressure, and will allow you to size the hydraulic power unit for the average load, not the peak load, saving you money and energy.
  • On the hydraulic power unit, a variable-flow pump will use the least energy. You should be able to buy a hydraulic power unit from any hydraulics distributor, and they should be able to recommend components.

Have you determined a cylinder diameter yet? If you are simply moving a mass of 2000 lbs, with not much friction, then I think you can use the smallest cylinder that allows an internal sensor, which is a 1.5" bore. The max speed of you motion is probably around 4.5"/sec. This will give you the 3 second total move time, including acceleration and deceleration. Just based on experience and gut feel, a 1.5" bore cylinder with 1500 psi system pressure should be able to handle it just fine.

For calculating pump flow needs, if you do use a 1.5" bore cylinder, then one extend stroke will use a volume of PI*(1.5/2)^2 * 12 = 21 cu. in. The retract will use less, of course, so back and forth would be max 40 cu. in. Therefore, if you do 6 strokes per minute, that would be 6 * 40 = 240 cu. in., which is about 4 liters. Therefore, the average pump flow should be at least 4 liters/minute.

For valve sizing, assuming a max speed of 4.5 "/sec, the flow would be PI*(1.5/2)^2 * 4.5 = 7.9 cu.in./sec., which is 477 cu.in./min, or about 7.8 L/min. So, get a valve around 10 L/min or so.

If you want a copy of Delta’s hydraulic design guide, go to deltamotion.com and click Free Design Guide.