fcat

ROS2 Fastcat node for running EtherCAT Devices

fcat is a ROS2 wrapper around the C++ fastcat library. This module will published variable-sized arrays of state information and subscribe to ROS Topics to delegate commands down to the EtherCAT devices.

Some logic checking is performed on the EtherCAT bus topology to only create state topics and commands subscriptions for device types on the bus.

Cursory checking for device names is performed, if a command for non-existent device is issued, fcat will ignore the command and log a message to STDOUT - No indication the device name is not found will be sent to the application.

Configuration of fcat is delegated almost completely to the input fastcat configuration file.

An optional ROS2 node called fcat_srvs is provided in this package. The purpose of this node is to provide a light-weight blocking service interface to make it easier to script long-running behaviors with a sequencing tool like commander.

Quickstart

Due to a potential issue in the default RMW implementation, the cyclone vendor is recommended for use as of the Feb 2021 ROS2 Foxy release.

sudo apt install ros-${ROS_DISTRO}-rmw-cyclonedds-cpp

fcat

If fcat is used to interact with real EtherCAT devices, the permissions of the ROS2 node need to be elevated. The best way we have found to do this is to start a root session and source the workspace.

# start a root session
sudo -s
# load in the ld config to find the shared libraries
source /path/to/ws/install/setup.bash
# use cyclone
export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp

Finally, run the fcat process. Note: If fcat is going to be used to run without real EtherCAT devices, you can safely skip the preceding steps.

ros2 run fcat fcat --ros-args -p fastcat_config_path:=[FILE_PATH]/[CONFIG].yaml

Optionally, the default namespace "fcat" and default node name "fcat" can be remapped like so:

ros2 run fcat fcat --ros-args -p fastcat_config_path:=[FILE_PATH]/[CONFIG].yaml -r __ns:=/foo -r __node:=bar

fcat_srvs

This process does not need to be run with elevated permissions

ros2 run fcat fcat_srvs

The fcat Node

Parameters

Name	Description	Default
fastcat_config_path	The path of Fastcat input YAML bus configuration	""
create_joint_state_pub	Enables publishing of state/joint_states topic useful for RVIZ2 or Moveit2!	true

Topics

Publisher

Device publishers are only created if at least one device is found on the user-specified Fastcat configuration file. module_state is the only state topic guaranteed to be published so this signal is suitable for liveliness checks.

Type	Default Name	Description
fcat_msgs/ModuleState	/fcat/state/module_state	Module status of Fastcat Bus
fcat_msgs/ActuatorStates	/fcat/state/actuators	Variable-sized Array of ActuatorState telemetry
fcat_msgs/EgdStates	/fcat/state/egds	Variable-sized Array of EgdState Telemetry
fcat_msgs/El2124States	/fcat/state/el2124s	Variable-sized Array of El2124State Telemetry
fcat_msgs/El3208States	/fcat/state/el3208s	Variable-sized Array of El3208State Telemetry
fcat_msgs/El3602States	/fcat/state/el3602s	Variable-sized Array of El3602State Telemetry
fcat_msgs/JedStates	/fcat/state/jeds	Variable-sized Array of JedState Telemetry
fcat_msgs/CommanderStates	/fcat/state/commanders	Variable-sized Array of CommanderState Telemetry
fcat_msgs/ConditionalStates	/fcat/state/conditionals	Variable-sized Array of ConditionalState Telemetry
fcat_msgs/FaulterStates	/fcat/state/faulters	Variable-sized Array of FaulterState Telemetry
fcat_msgs/FilterStates	/fcat/state/filters	Variable-sized Array of FilterState Telemetry
fcat_msgs/FunctionStates	/fcat/state/functions	Variable-sized Array of FunctionState Telemetry
fcat_msgs/PidStates	/fcat/state/pids	Variable-sized Array of PidState Telemetry
fcat_msgs/SaturationStates	/fcat/state/saturations	Variable-sized Array of SaturationState Telemetry
fcat_msgs/SchmittTriggerStates	/fcat/state/schmitt_triggers	Variable-sized Array of SchmittTriggerState Telemetry
fcat_msgs/SignalGeneratorStates	/fcat/state/signal_generators	Variable-sized Array of SignalGeneratorState Telemetry

Subscribers

Device subscribers are only created if at least one device is found on the user-specified Fastcat configuration file. Reset and Fault are the only guaranteed command topics.

Type	Default Name	Description
std_msgs/Empty	fcat/cmd/reset	Global reset for all devices on bus. Always available.
std_msgs/Empty	fcat/cmd/fault	Global fault for all devices on bus. Always available.
fcat_msgs/ActuatorCspCmd	fcat/cmd/actuator_csp	Cyclic Synchronous Position Command, should be sent every loop period
fcat_msgs/ActuatorCsvCmd	fcat/cmd/actuator_csv	Cyclic Synchronous Velocity Command, should be sent every loop period
fcat_msgs/ActuatorCstCmd	fcat/cmd/actuator_cst	Cyclic Synchronous Torque Command, should be sent every loop period
fcat_msgs/ActuatorProfPosCmd	fcat/cmd/actuator_prof_pos	Trap Profiled Position Command
fcat_msgs/ActuatorProfVelCmd	fcat/cmd/actuator_prof_vel	Trap Profiled Velocity Command
fcat_msgs/ActuatorProfTorqueCmd	fcat/cmd/actuator_prof_torque	Trap Profiled Torque Command
fcat_msgs/ActuatorSetOutputPositionCmd	fcat/cmd/actuator_set_output_position	Sets the Current Actuator Output Position
fcat_msgs/ActuatorCalibrate	fcat/cmd/actuator_calibrate	Performs Hardstop calibration
fcat_msgs/CommanderEnableCmd	fcat/cmd/commander_enable	Enables a commander for Fastcat internal functions
fcat_msgs/CommanderDisableCmd	fcat/cmd/commander_disable	Disables an active Commander
fcat_msgs/El2124WriteAllChannelsCmd	fcat/cmd/el2124_write_all_channels	Writes All Digital Outputs
fcat_msgs/El2124WriteChannelCmd	fcat/cmd/el2124_write_channel	Writes Single Digital output Channel
fcat_msgs/FaulterEnableCmd	fcat/cmd/faulter_enable	Enables or Disables Faulter device, typically used for monitoring testbed-specific fault conditions
fcat_msgs/FtsTareCmd	fcat/cmd/fts_tare	Tares a FTS
fcat_msgs/JedSetCmdValueCmd	fcat/cmd/jed_set_cmd_value	Sets the JED cmd value
fcat_msgs/PidActivateCmd	fcat/cmd/pid_activate	Activates a Fastcat internal PID Controller

The fcat_srvs Node

Parameters

Name	Description	Default
loop_rate_hz	Loop rate of services	100
position_tolerance	Used to determine completion of service/actuator_prof_pos commands	0.01
velocity_tolerance	Used to determine completion of service/actuator_prof_vel commands	0.01
current_tolerance	Used to determine completion of service/actuator_prof_vel commands	0.01

Services

Services are only created if at least one device is found on the user-specified Fastcat configuration file. Currently, if the bus topology lacks actuator or pid devices, the fcat_srvs will not offer any services and need not be started at all.

Type	Default Name	Description
fcat_msgs/srv/ActuatorCalibrateCmd	fcat/service/actuator_calibrate	Executes blocking service to perform Actuator hardstop calibration
fcat_msgs/srv/ActuatorProfPosCmd	fcat/service/actuator_prof_pos	Executes blocking service to execute a profile position command to target position
fcat_msgs/srv/ActuatorProfVelCmd	root shell and run the fcat node from your user account.fcat/service/actuator_prof_vel	Executes blocking service to execute a profiled velocity command to target velocity. Returns once target velocity is attained.
fcat_msgs/srv/ActuatorProfTorqueCmd	fcat/service/actuator_prof_torque	Executes blocking service to execute a profiled torque command to target current. Returns once target velocity is attained.
fcat_msgs/srv/PidActivateCmd	fcat/service/pid_activate	Executed blocking service to execute a PID controller. The will return once a timeout is reached or if the input error signal is within the deadband argument for persistence_duration seconds