Industrial robots have very complex motion and control requirements due to their increasingly advanced kinematics capabilities. In addition to a diverse array of drives, encoders, I/O modules, and internal networks, the robot control system must also integrate a wide variety of peripherals on the robot flange such as grippers or weld gun. This complete robotic package is then married to a higher level control system that issues coordinating control signals such as a program number to be executed or an emergency stop. Often multiple fieldbuses are used in a single robotic application. Amidst this diversity of fieldbuses and devices, a common configuration and management tool is required.
Strengths of FDT/DTM Technology
At KUKA, the unifying tool kit includes an FDT Frame Application. This tool saves all fieldbus-specific information that is generated during commissioning. The FDT DTMs work seamlessly with one another, even though they are supplied by many different manufacturers. The very complex bus scenarios can be configured across multiple gateways without any difficulty using the nested communications capability in the FDT standard.
Initial commissioning and customer changes
A robot is commissioned in multiple phases. The initial commissioning takes place in the KUKA factory during the cabinet assembly. Based on the customer order, an FDT project is automatically created with factory settings. This includes the bus configuration for the drive technology with properly-sized converters, various encoder units, special modules, and optional special accessories, such as I/O modules. After this configuration, the cabinet is fully ready to operate.
System integrators or end users often alter the robot configuration with additional field devices, particularly tools that they can buy from third-party suppliers or build themselves. In order to put these into operation, they use the generic, fieldbus-specific device DTM provided by KUKA. This DTM derives the corresponding representation in the FDT project from a device description file.
If errors like defective wires or peripheral components occur while the robot is working, users have to determine the cause of the errors quickly and reliably. The DTMs are provided with tools for this purpose. These range from monitoring I/Os and analyzing fault memories on the devices all the way to very detailed analyses, such as determining envelope delay times or damping reserves in fiber-optic cables.
All robot control systems from KUKA that are shipped with Firmware Version 8.0 and newer are commissioned using FDT Technology. The supported fieldbuses range from conventional DeviceNet, PROFIBUS, and INTERBUS protocols to newer Ethernet-based systems EtherCAT, PROFINET, and EtherNet/IP. Complex scenarios can be implemented via cascaded gateways and proxies using standard FDT Technology.
To date, implementation scenarios have shown that the main effort in developing DTMs lies in the interpretation of device description files. This is due to the company-specific focus of generic device DTMs. The newer XML- based formats such as GSDML, FDCML, and ESI offer noteworthy simplifications compared to the traditional text-based formats GSD and EDS. That’s because they can rely on tried-and-tested XML parsers. Consequently, the interpretation of syntax and grammar is no longer required.
For a control system manufacturer supporting many different bus systems, FDT Technology offers great strengths. The high interoperability between the DTMs provides interesting strategic considerations for make or buy decisions.