Model-based proportional pressure regulation
Model-based proportional pressure regulation
Festo Motion Terminal

Model-based proportional pressure regulation

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With model-based regulation, there is no need for external sensors. By storing fewer boundary parameters for the system, such as tube length, tube diameter and cylinder size, the anticipatory control system ensures maximum accuracy, as the app can compensate for a drop in pressure and volume using the control technology.

With the Motion App „Model-based proportional pressure regulation“ there are two pressure regulators per valve slice at the two valve outlets, which you can use to regulate pressures independently of each other. The integrated sensors precisely monitor the pressure. Along with the internal pressure sensors (connections 1, 2, 3, 4) a status controller/observer structure is used. The volume and the tubing are taken into account based on the model.

As a user, you need to specify the volume, the tube diameter and the tube length. This way, you do not need an externally attached sensor – which is particularly interesting for clean design. Additionally, with model-based pressure regulation, differential pressures – which are the result of different tube lengths and diameters – can be compensated. This means that you can achieve precise and dynamic pressure regulation, even with long tubing lines.

The pressure regulator is also suitable for vacuum applications. For vacuum applications, a vacuum is connected to duct 3. You can connect pressure at duct 1 at the same time, for example for an ejector pulse. Possible applications are pressure control for volume, force control for the known effective area, activating process valves, vacuum control with regulated ejector pulse and special, highly dynamic pressure regulation profiles (pressure sequence control).

When using the Motion Apps at the same time, you have to order exactly the right number of Motion Apps that you need on the Festo Motion Terminal VTEM.

Characteristic pressure curve of simple pressure regulators

Setpoint pressure Pressure at the valve Pressure in the system
Slow pressure rise in the system

Pressure curve of the Motion Terminal with „Model-based proportional pressure regulation“

Setpoint pressure Pressure at the valve Pressure in the system
Fast rise in pressure in the system due to intermittently increased pressure at the valve.
Technical Details

-       Pressure:

  • -0.9 … +8 bar

-       Minimum volume:

  • 50 ml

-       Maximum volume:

  • 2 l (larger volumes can also be regulated, however the valve does restrict the flow rate)

-       Specifications in the Motion App and via the PLC:

  • Setpoint pressure at duct 2
  • Setpoint pressure at duct 4

-       Feedback to the controller:

  • Actual pressure at duct 2
  • Actual pressure at duct 4

-       Recommended tube lengths and volumes:

  • 1 m … 5 m
  • Currently, only a tube length greater than one meter is supported (>1 m)
  • Only for volumes with minor changes ±10%

-       Notes:

  • A filter must be installed upstream of valves operated in vacuum mode. This prevents any foreign matter in the intake air getting into the valve, e.g. when operating a suction cup.
  • When using internal pilot air supply, the necessary minimum pressure (3 bar) in duct 1 must be maintained.
  • The sensors are designed so they are protected against contamination.
  • Both the supply pressure at port 1 and the exhaust pressure at port 3 are detected. If a vacuum is connected to port 3, the current low pressure value will be determined.
  • When using tubing PUN4, the control characteristic C1 should be selected.
  • Zero volume (clogged-up valve outlet): best with CS setting, with control characteristic C1 a stable control behavior with overshoot can be achieved.
  • If the pressure setpoint specification for the valve outlet is greater than the supply pressure determined internally, the setpoint value of the internal pressure will be restricted to the supply pressure determined internally.
  • If the pressure setpoint specification for a valve outlet is less than the exhaust pressure of +0.1 bar, this outlet will be regulated and fully exhausted.

-       Static characteristic values (according to FN 942030) valid from -0.9 … 7 bar:

  • Linearity error in the range of 5% ... 95% setpoint value under nominal conditions, based on the ideal characteristic curve: 170 mbar
  • Repetition accuracy in the range of 5% ... 95% setpoint value under nominal conditions: 80 mbar
  • Max. hysteresis in the range of 5% ... 95% setpoint value under nominal conditions: 80 mbar
  • Overall accuracy in the range of 5% ... 95% setpoint value under nominal conditions: 210 mbar
  • Response sensitivity in the range of 5% ... 95% setpoint value under nominal conditions: 80 mbar
  • Max. temperature error over the entire T-range in addition to overall accuracy: ± 50 mbar
  • Zero point suppression:
    • Setpoint value less than 100 mbar over exhaust pressure--> exhaust
    • Setpoint value 120 mbar or more over exhaust pressure--> control active

-       Dynamic characteristic values (according to FN 942030) valid from 0 … 7 bar:

  • Recovery time (tube PUN 8, 2 m, volume 0.1 l Setpoint value jump 25%  75%  25%):
    • <0.5 s
  • Permitted overshoot with suddenly changing setpoint values (volume 0.1 l):
    • <5% FS
Technical Requirements
Available as from firmware version 4.6