Delta RMC151 User Manual download pdf (Page 101)

3 Controller Features

Advanced:

Velocity I-PD

Pressure

Pressure/Force Limit

Force

Pressure/Force Limit

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:

• Open Loop Rate (10)

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.

• Direct Output (9)

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.

• Open Loop Halt (2)

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.

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