Drives and Controls Magazine
Multi-axis system has response times of less than 1µs
Published:  23 February, 2015

The German controls manufacturer Beckhoff has developed a compact, multi-axis servo system that allows precision positioning and machining with extremely short control cycles, thus boosting production output. The AX8000 system combines FPGA technology with multi-core ARM processors to produce sample and response times of less than 1µs for current control, and velocity control cycle times as low as 16µs, depending on the switching frequency. Position control cycle times are 31.25µs, and the minimum EtherCat cycle time is 62.5µs.

The modular system consists of power supply modules, single- and double-axis modules, and capacitor modules, all 223mm high, 192mm deep, and either 60mm or 90mm wide. Systems can be commissioned rapidly by plugging together the required modules. A spring-based quick-connect system, called AX-Bridge, links the AX8000 modules in a failsafe manner, without needing tools. It bridges the DC link, and makes 24V DC and EtherCat connections.

The power supply modules are available in 60mm-wide 20A or 90mm-wide 40A versions, for 100–230V AC or 400–480V AC applications. Brake resistors, choppers and mains filters are built in, avoiding the need for external components, and simplifying inventory management.

The 60mm-wide motion modules include single-axis versions with a rated current of 8A, and double-axis versions rated at 2 x 6A. A 90mm-wide single-axis module is available with a rated current of 18A. Scalable motor current measurement allows the 8A and 18A modules to cover a wide range of applications.

Beckhoff’s multi-axis servo system consists of compact modules that can be plugged together rapidly

The AX8000 system supports single-cable connections with motors and provides four digital inputs per axis – two of them preconfigured for onboard safety functions. Beckhoff’s TwinSafe system provides 17 SafeMotion functions.

An integrated TwinCat runtime system includes software modules for, among other things, precise control of speed and position. Users can program motion control projects using the IEC 61131-3 languages, C++ or Matlab/Simulink. Diagnostic tools are provided in the form of a software oscilloscope, while axis optimisation is provided by TwinCat BodePlot.