Delta RMC151 - Manual (Page 206)

RMC70/150 and RMCTools User Manual
PID with Acceleration Control with accelerometers
This gives the tightest control. However, it really works the valve and will always
overshoot slightly. Tuning hot tends to cause small high-speed vibrations and pushes
stability limits.
This will generally require the use of a filter on the acceleration. Either the Low Pass filter
or the Model based filter can be used, but Delta recommends trying the Low Pass filter
first because it is easier to set up and does not require that an accurate model be
generated by the Tuning Wizard. See the Acceleration Filter Type and Actual Acceleration
Filter topics for more details.
PID with Acceleration Control without accelerometers
Much lower performance, may be good for some applications, especially for low-friction
cylinders with small load. Does not require extra feedback devices or inputs on the
controller. Least expensive option.
Required Modules
Active Damping and Acceleration Control require an AP2 module for the secondary
acceleration or force feedback. Using Acceleration Control without accelerometers does
not require any additional modules other than the axis module.
See the Active Damping or Acceleration Control topics for details on required hardware
and how to define the axes.
Suggested Components
Pressure Transducers
Choose pressure transducers with a power supply range that includes 24V, and a voltage
output range of 0 to 5 volts or more. The pressure transducers should be mounted on the
ends of the cylinder so that they measure the pressure inside the cylinder, not the
pressure in the A or B port lines.
Accelerometers
For pneumatic control, choose 1-axis accelerometers that cover approximately -2g to
+2g, depending on the accelerations in your application. To simplify the wiring, choose
one with an internal voltage regulator, a power supply range that includes 24V, and a
voltage output range of 0 to 5 volts or more.
Delta recommends using two accelerometers, one on the stationary frame and one on the
moving load. This is because the stationary frame is not usually truly stationary – its
vibrations will impact the motion of the load.
Delta has successfully used accelerometers from Crossbow Technology Inc.
(www.xbow.com). The model used was the LP series - General Purpose, part number
CXL04LP1-R, which is a ± 4g, 1-axis accelerometer with an internal voltage regulator. It
can be powered with a 24V power supply.
Pneumatic Servo Valves
Choose a zero-lap servo valve.
Pneumatic Cylinder
For best results, choose a low-friction cylinder.
3.12. Transducers Basics
3.12.1. MDT Transducer Fundamentals
186 Delta Computer Systems, Inc.