Maxon Epos Hardware Interface

ROS2 control hardware interface for Maxon Epos 2/4 motor controllers using the EPOS Command Library 6.8.1.0.

Adapted from https://github.com/yoshito-n-students/eposx_hardware and converted to ROS2.

Installation

1. Install UDEV rules:

ros2 run epos_hardware install_udev_rules

2. Get motor controllers serial id:

ros2 run epos_hardware list_available_devices

Usage

Add the plugin to the ros2_control tag in your URDF file:

<ros2_control name="epos_hardware" type="system">
    <hardware>
        <plugin>epos_hardware/EposHardware</plugin>

         <joint name="front_left_wheel_joint">
            <param name="device_name">EPOS2</param>
            <param name="protocol_stack_name">MAXON SERIAL V2</param>
            <param name="interface_name">USB</param>
            <param name="serial_number">0xxxxxxxxxxxxx</param>
            <param name="clear_faults">false</param>
            <param name="profile_position_velocity">30</param>
            <param name="profile_position_acceleration">50</param>
            <param name="profile_position_deceleration">50</param>
            <param name="profile_velocity_acceleration">50</param>
            <param name="profile_velocity_deceleration">50</param>

            <command_interface name="velocity"/>
            <state_interface name="position"/>
            <state_interface name="velocity"/>
        </joint>
        <transmission name="rear_right_wheel_joint_transmission">
            <plugin>transmission_interface/SimpleTransmission</plugin>
            <actuator name="rear_right_motor" role="rear_right_motor"/>
            <joint name="rear_right_wheel_joint" role="rear_right_wheel_joint">
                <mechanical_reduction>53</mechanical_reduction>
            </joint>
        </transmission>
        
        <joint name="front_right_wheel_joint">
            <param name="device_name">EPOS2</param>
            <param name="protocol_stack_name">MAXON SERIAL V2</param>
            <param name="interface_name">USB</param>
            <param name="serial_number">0xxxxxxxxxxxxx</param>
            <param name="clear_faults">false</param>
            <param name="profile_position_velocity">30</param>
            <param name="profile_position_acceleration">50</param>
            <param name="profile_position_deceleration">50</param>
            <param name="profile_velocity_acceleration">50</param>
            <param name="profile_velocity_deceleration">50</param>

            <command_interface name="velocity"/>
            <state_interface name="position"/>
            <state_interface name="velocity"/>
        </joint>
         <transmission name="front_right_wheel_joint_transmission">
            <plugin>transmission_interface/SimpleTransmission</plugin>
            <actuator name="rear_right_motor" role="rear_right_motor"/>
            <joint name="front_right_wheel_joint" role="front_right_wheel_joint">
                <mechanical_reduction>-53</mechanical_reduction>
            </joint>
        </transmission>
</ros2_control>

In our setup, every controller is connected seperately to the computer using USB, however, all methods that work with the Epos Command Library should also work with this code. For each joint, an device_name, protocol_stack_name, interface_name, serial_number and encoder_resolution parameter should be set. Additionally, a clear_faults parameter can be set, which clears all device faults upon start.

The profile_position_velocity parameter sets the velocity in the position profile in rad/s before the reduction. profile_position_acceleration and profile_position_deceleration are setting the corresponding acceleration and deceleration values in rad/s² before the reduction. The profile_velocity_acceleration and profile_velocity_deceleration are setting these values for the profile velocity mode.

Supported command interfaces

Command interface position, velocity and current are supported.

Supported state interfaces

The following state interfaces are supported:

• position (Position)
• velocity (Velocity)
• current (Current [A])