Using Drives with EtherCAT

The RMC200 EtherCAT MainDevice offers connectivity to many drives, with many options and flexibility. The RMC200 supports EtherCAT drives conforming to the CANopen over EtherCAT (CoE) CiA402 drive profile. The RMC200 does not support SoE. This topic provides an overview of the main features related to using EtherCAT drives.

Axis Definitions

When defining axes, the following options are available for EtherCAT and need to be considered.

Control Mode

On an RMC200 that includes an EtherCAT module, all control axes will be either Local Control or Remote Control:

Remote Control:

This is specifically for EtherCAT drives in CSP mode (see Modes of Operation below), where the drive performs the closed-loop position control and the RMC continuously sends the axis’ Target Position to the drive.

Local Control:

All other control axes (whether EtherCAT or not) are Local Control, where the RMC performs the closed-loop position control.

In the Axis Definitions dialog, in the Type column, Remote Control axes are listed as Remote Position Control. Local Control axes are listed as Servo Position Control.

Output

When defining an axis that uses an EtherCAT drive, the axis’ Output is always to a drive.

Feedback

For axes using EtherCAT drives, the following options are available:

Feedback (general):

From the EtherCAT drive
From an external feedback device (via EtherCAT, or via an RMC200 I/O module)

In some cases, this can provide greater measurement accuracy than using the drive, especially if gearing or linkage exists between the motor encoder and the point where the position accuracy is critical.

Secondary Feedback (dual-loop axes):

From the EtherCAT drive in the form of torque or current
From an external pressure or force sensor, or dual-input pressure (via EtherCAT, or via an RMC200 I/O module)

Modes of Operations

The RMC supports the following CiA402 modes of operation:

Cyclic Synchronous Position (CSP): The drive calculates the position control loop internally. The RMC continuously sends a target position to the drive.

This mode is very common in automation.
Cyclic Synchronous Velocity (CSV): The RMC continuously receives position data from the drive, calculates the position control loop, and sends a velocity command signal to the drive.

This mode provides the most flexibility in control, making use of the RMC200’s control capabilities. The position tuning in the RMC for this mode is very similar to tuning a hydraulic cylinder. This mode is especially useful for using the RMC’s dual-loop control such as position-force control.
Cyclic Synchronous Torque (CST): The RMC continuously receives position data from the drive, calculates the control loop, and sends a torque command signal to the drive. This mode is rarely used. In certain types of applications with torque control or limiting, this mode can be useful. However, many such applications can be done in CSV mode with dual-loop control.

For more details, see the Drive Modes of Operation topic.

Drive States

The RMC200 Drive State axis status register displays the state of the drive.

The drive states are:

Not Ready to Switch On
Switch on disabled
Ready to switch on
Switched on
Operation enabled (Oper. Enabled)
Quick stop active
Fault reaction active
Fault

The RMC200 handles changing the state of the drive when an axis is enabled and disabled. The drive must be in the Operation Enabled state to operate.

These drives states are separate from EtherCAT communication states. However, a drive will usually not allow operation if the drive’s EtherCAT state is not Op Mode.

For more details, see the Drive State axis status register.

Homing

The RMC200 EtherCAT supports CiA402 Touch Probe homing only. It does not support CiA402 homing modes that are built into the drive. Touch probes may be used for homing or registration. The touch probe operates in the drive itself and is not affected by any communications delays.

RMC User Programs can be used together with touch probe homing to create the desired motion profiles and logic for homing. For example, a user program can command the axis to move at a certain velocity, wait for an input from a prox sensor to turn on, arm the home using the touch probe, then move slowly in the other direction and wait for the homing to occur as the prox sensor turns on.

See Homing for details.

Setup Procedure for a Drive

To be added.

See Also

Modes of Operation | Drive States

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