The article introduces a new driver for Trinamic Motor Controller (TMC) and describes the integration of the components into a Robot Operating System (ROS) ecosystem. The TMC-ROS1 driver enables seamless communication between the driver layer of the TMC and the application layer within the ROS framework. This applies to the entire range of TMC boards supported by the driver. The capabilities of the TMC-ROS1 driver are described in detail below, namely motor control, information readout, command execution, parameter readout and support for different configurations. In addition, an overview is given of how the motor controllers can be integrated into embedded systems and applications using the advantages offered by the ROS framework.

The TMC-ROS1 driver

ROS is a robotics middleware containing a set of software libraries and powerful developer tools from drivers to state-of-the-art algorithms—upon which robotic systems or applications can be developed. ADI Trinamic motor controllers enable a new class of intelligent actuators and as ROS became more and more prevalent, especially in robotics, additional module support such as ROS drivers were developed to extend usability for manufacturing and industrial automation applications. Analog Devices’ TMC ROS1 driver provides a functionality similar to the company’s Triaminic Motor Control Language Integrated Development Environment (TMCL-IDE), but with a key distinction: it allows nodes within a ROS-capable system to use TMCs without the need for additional driver installations. Moreover, adi_tmcl incorporates its own TMCL protocol interpreter, enabling it to interpret user-requested commands that comply with the TMCL standard. The final layer, tmcl_ros_node, establishes a direct interface with the ROS system, offering features like publishers, subscribers, and services. Each of these functionalities can be customized using a set of parameters, which will be discussed in detail in the following sections.

Support for different TMC boards

Figure 1: Code section for executing the TMC-ROS driver with the TMCM-1636. © Analog Devices

TMC ROS driver or adi_tmcl was designed to support all commercially available TMCs that adhere to the TMCL protocol. As of the publication of this article, it currently supports the CAN interface (specifically SocketCAN). However, there are ongoing developments to include support for other interfaces in the near future. These TMCs encompass the ADI Trinamic PANdriveTM smart motors and modules, which can further be categorized for stepper motors and brushless DC (BLDC) motors. The use of ROS parameters enables adi_tmcl to seamlessly support different TMC boards. This allows the configuration of the tmcl_ros_node without the need to rebuild the entire package(Figure 1).

Within the adi_tmcl/config directory, each ADI Trinamic motor controller module (TMCM) is associated with two YAML files. These files, written in a human-readable data serialization language, contain ROS parameters and should be loaded during execution:

• adi_tmcl/config/autogenerated/TMCM-XXXX.yaml - This YAML file is autogenerated and contains module-specific parameters and is not recommended to be modified as it may cause the node to performdifferently.
• adi_tmcl/config/TMCM-XXXX_Ext.yaml - This YAML file contains all parameters that users can modify to (1) communcate with the board (for example, interface name), (2) enable control of motors, and (3) change ROS topic names

Figure 2: Illustration of the hardware connections to the TMCM-1636 (top) and view of the actual configuration (bottom). © Analog Devices

For example, to use the 'TMCM-1636'(Fig. 2), all you have to do is start adi_tmcl tmcm_1636.launch using $ roslaunch. The YAML files for the TMCM-1636 are loaded with adi_tmcl/launch/tmcm_1636.launch.

One-time configuration of TMC modules using the TMCL IDE

Before using the TMC board via ROS, the board needs to be calibrated with the motors being used. All calibration should be done using the TMCL-IDE and should be stored in the EEPROM (otherwise the motors may not be controlled correctly).

• For a run-through/tutorial of how the motor calibration is done in the TMCL-IDE via its Wizard Pool feature,
  • For BLDC motor modules like TMCM-1636, check this tutorial.
  • For stepper motor modules like TMCM-1260, check this tutorial.
•  For a run-through/tutorial of how the proportional-integral (PI) tuning is done in the TMCL-IDE via its PI tuning feature, check this tutorial.

Once calibration and tuning have been completed, all parameters must be saved in the board's EEPROM. This can be done either with the store parameter, the STAP command and/or creating and uploading a TMCL program and activating the autostart mode. Some boards do not support all of these three options.

After the configuration/tuning of the TMC and motor, the design of the TMC ROS driver was simplified to control the motors based on the one-time configuration using TMCL-IDE.

Moving and stopping the motor

The TMC ROS driver moves or stops the motor by publishing in one of the following topics:

• /cmd_vel (geometry_msgs/Twist) - Sets the motor’s velocity
• /cmd_abspos (std_msgs/Int32) - Sets the motor’s absolute position
• /cmd_relpos (std_msgs/Int32) - Sets the motor’s relative position
• /cmd_trq (std_msgs/Int32) - Sets the motor’s torque

It should be noted that in a TMC configuration with multiple axes, there are separate topics for the different motors.

Users can connect their ROS systems to publish in these specific topics to control the movement of the motors. The choice of topics depends on the application, the TMC settings and the motor types used. For a mobile robot, for example, the user can choose to set the speed, whereas for a gripper it would make more sense to specify the position.

Figure 3: Commands for testing the speed setting of the TMC ROS driver. © Analog Devices

Users can connect their ROS systems to publish to these specific topics, enabling them to control the movement of the motors. The choice of topic depends on the particular application, TMC settings, and the type of motors being used. For instance, in the case of a wheeled robot, the user might choose to set the velocity, while for a gripper, setting the position would be more appropriate.
As an illustrative example, consider the script adi_tmcl/scripts/fake_cmd_vel.sh. This straightforward script orchestrates the rotation of a motor in both clockwise and counter-clockwise directions, progressively increasing the velocity. The commands shown in Figure 3 are used for execution.

Reading information from TMC and engine

The system can read information from the TMC ROS driver by subscribing to the /tmc_info (adi_tmcl/TmcInfo) topic. This provides data on voltage, TMC status, actual speed, actual position and actual torque.