Poulpe ethercat grpc server and client

This crate provides a grpc server and client for controlling the poulpe boards over ethercat.

The server creates the ethercat master and creates the gprc api that allows the connection of multiple clients corresponding to the number of poulpe boards connected to the ehtercat master.

Real-time communication

Client server communication in gprc is not real-time and given that we are controlling a real-time system, all the messages exchanged between the server and the client are timestamped and security checks are performed to ensure that the messages are not too old.

• If server reads the clients message that has a timestamp older than 5ms, it will ignore it
• If client reads the server messages that are older than 1second (defined in the configuration file), it will consider that the server is down and will kill the program
  • If the feature stop_client_on_server_timeout is set the clients will stop their operation if the server is down

Safety features

This crate implements the following safety features:

• Make sure tha the real-time communication is established between the server and the client
  • If the server is not responding, the client will stop the operation (if the feature stop_client_on_server_timeout is enabled)
  • All client messages that are older than 5ms are ignored by the server
• Make sure that all the slaves are in the operational state
  • If the slave is not operational, the server will not respond to the client messages
• Make sure that no actuators are in the error state
  • If the actuator is in the error state, the server will display the error message
  • It will send an emergency stop to all the actuators, if the feature qucik_stop_on_slave_fault is enabled
  • It will stop the operation of the server, if the feature stop_server_on_actuator_error is enabled

feature	description	enabled by default
stop_client_on_server_timeout	Stop the client if the server is not responding	yes
qucik_stop_on_slave_fault	Send the emergency stop to all the actuators if one of them is in the error state	yes
stop_server_on_actuator_error	Stop the server if one of the actuators is in the error state	no

See the and configure the features in the Cargo.toml file.

Client-server communication

The server communicates with the ethercat master reading and writing the data to the poulpe boards.

The client sends the PoulpeCommand message to the server and receives the PoulpeState message from the server. PoulpeCommand message contains

• id : id of the poulpe board
• emergency_stop : emergency stop flag (true for emergency stop)
• compliancy : activate the board (true for active)
• mode_of_operation : mode of operation
• target_position : target position
• target_velocity : target velocity
• target_torque : target torque
• velocity_limit : velocity limit
• torque_limit : torque limit
• published_timestamp : timestamp of the message (timestamp when the message was sent)

PoulpeState message contains:

• id : id of the poulpe board
• mode_of_operation : mode of operation
• actual_position : actual position
• actual_velocity : actual velocity
• actual_torque : actual torque
• axis_sensors : axis sensors
• axis_sensor_zeros : axis sensor zeros
• board_temperatures : board temperatures
• motor_temperatures : motor temperatures
• requested_target_position : requested target position
• requested_velocity_limit : requested velocity limit
• requested_torque_limit : requested torque limit
• state : state of the board
• error_codes : error codes
• compliant : compliant flag
• published_timestamp : timestamp of the message (timestamp when the message was sent)