A control axis outputs a signal to an actuator and controls either zero, one or two quantities, such as Position, Pressure, or Force. The controlled quantity is provided by a feedback input, whether from an RMC I/O module, or via EtherCAT, or via Custom Feedback. A control axis is capable of controlling a system because it outputs a signal such as a Control Output.
Local versus Remote Control
In RMCs with an EtherCAT MainDevice, all control axes are described as either Remote (Main PID in the drive) or Local (Main PID in RMC):
Local (Main PID in RMC):
The main PID is performed in the RMC, has a Control Output, and controls zero, one, or two quantities.
Remote (Main PID in the drive):
Supports only single-loop position control in an EtherCAT drive using the Cyclic Synchronous Position (CSP) mode of operation. The RMC axis does not have any gains and continuously sends the Target Position to the drive.
In RMCs without an EtherCAT MainDevice, all control axes are implicitly Local.
Control axes are defined by the number of quantities controlled. Each controlled quantity uses one PID loop.
1. Single-Loop Control Axis
A control axis that controls a single quantity, such as position or pressure, is called a one-input or single-loop control axis.
|
One-Input Control Axis Types |
Required Inputs |
Required Control Outputs |
Transducer Types |
|
Position |
1 |
1 |
MDT, SSI, Analog, Quadrature, Resolver, EtherCAT |
|
Velocity |
1 |
1 |
Analog Voltage or Current, EtherCAT |
|
Pressure |
1 |
1 |
Analog Voltage or Current, EtherCAT |
|
Force |
1 or 2 |
1 |
Analog Voltage, Current, Load Cell, EtherCAT |
Note:
A force input requires 1 analog or mV/V input if a load cell is used, or
2 analog inputs for differential force on a hydraulic cylinder. In the
differential case, it is still considered one input, since the calculated force is only
one quantity.
2. Dual-Loop Control Axis
A control axis that controls two quantities, such as position and pressure, is called a two-input or dual-loop control axis. Notice that the secondary inputs, if coming from an RMC I/O module, must always be analog or mV/V inputs. Secondary inputs can also come from EtheRCAT or via Custom Feedback.
|
Two-Input Control |
Required Primary Inputs |
Required Secondary Analog or mV/V Inputs |
Required Control Outputs |
|
Position-Pressure |
1 |
1 |
1 |
|
Position-Force |
1 |
1 or 2 |
1 |
|
Position-Acceleration |
1 |
1 or 2 |
1 |
|
Velocity-Pressure |
1 |
1 |
1 |
|
Velocity-Force |
1 |
1 or 2 |
1 |
|
Velocity-Acceleration |
1 |
1 or 2 |
1 |
Note:
A force input requires one EtheCAT, one analog or one mV/V input if a load cell is used, or
two EtherCAT or two analog inputs for differential force on a hydraulic cylinder. In the
differential case, it is still considered one input since it is only one
quantity, although it requires two physical analog inputs.
3. Output Only Axis (No Control Loops)
An Output Only axis has a Control Output and does not have any inputs. Control Outputs require a physical analog output or an output via EtherCAT.
Creating a Control Axis
For details on defining axes, see the following topics:
See Also
Axis Types: Overview | Axis Types: Reference
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