Open loop control, Open loop, Control – Delta RMC151 User Manual
Page 101
3 Controller Features
Advanced:
Pressure
Force
Dual-Loop Control
The RMC supports dual-loop control, for example position-pressure or position-force. This
allows controlling two quantities with a single actuator. For example, consider an injection
molding application. The system first moves in position control to inject the material, then
needs to maintain a certain force. Using dual-loop control, this can be done with a single
actuator (typically a hydraulic valve).
On the RMC, dual-loop control requires one Control Output, one position (or velocity)
feedback, and a pressure or force input (this is called the secondary feedback).
On the RMC70, dual-loop control requires that the secondary feedback is from an AP2
module. For the RMC150, dual-loop control requires a pressure-control enabled RMC150,
designated as an RMC151.
See the Position-Pressure and Position-Force Control topic for more details.
Closed Loop Commands
See the List of Commands topic for a list of closed-loop commands.
3.5.3. Open Loop Control
Open Loop Control is the simplest form of control. A signal is given to a system, for example,
2 volts of Control Output to a valve, causing a cylinder to extend at a speed determined by the
system characteristics (valve, cylinder and load, or drive, motor and load). In open loop
control, there is no way of commanding the system to go exactly at a specific speed or go to
an exact position.
Sometimes, improperly tuned closed loop control may cause a system to oscillate or exhibit
other erratic behavior. Usually, issuing an open loop command with 0 volts of Control Output
will stop the system safely. See Auto Stops for details on halting a system.
Some of the RMC open loop commands have a ramp rate parameter that specifies the rate at
which the Control Output ramps up to the Requested Output. The ramp avoids jerking the
system.
Open Loop Commands
The RMC has the following open-loop commands:
•
This is the basic open-loop command. It ramps the Control Output from the current
value to the Requested Output at the rate specified by the Ramp Rate parameter. Use
this command for normal open-loop moves.
•
This command is similar to the Open Loop Rate command, except it disables all the
safety features of the RMC. It is intended only for testing the Control Output. Use the
Open Loop Rate command for all other purposes.
•
This halt ramps the Control Output from its current value to zero. It also performs
other halt actions.
•
Open Loop Absolute (11) and Open Loop Relative (12)
These are specialty open loop commands. They specify the Control Output as a
function of distance. As such, they do require position feedback on the axis.
deltamotion.com
81