With an integrated Profibus interface, Beckhoff's AH2000 hydraulic controllers contain a powerful PC-based kernel. A 266 MHz Pentium I processor provides the necessary computing power, and the control functions are realised via the TwinCAT automation software under the Windows NT Embedded operating system. Their extremely short cycle time of 250 µs enables them to also provide speed control for very fast control valves. Depending on the application, either a central controller or the hydraulic controller itself deals with position control.

Open communication facilities mean that users can access the parameters from either the central controller or from an HMI device. The key is the ADS communication protocol from Beckhoff, which is also available via Profibus. The controller, therefore, offers remote diagnostic functionality, without additional expense.

Designed for harsh environments
The use of fans or other moving parts was avoided in AH2000 controllers, to cater for harsh industrial environments. A flash file system serves as data backup, and replaces the hard disk. The enclosed design and suitable connectors ensure protection class IP 65. The controller is located in a compact aluminium housing measuring 174 x 200 x 80 mm, and weighing approximately 3.5 kg. AH2000 hydraulic controllers offer comprehensive peripheral connection options. Hydraulic valves with 12-pin connectors from Rexroth or Bosch, or a variety of valves from other manufacturers, with appropriate cable sets, can be connected. The controller handles the power supply and monitoring functions for the valve. Incremental encoders with sine/cosine signals (1 Vss) or TTL signals, e.g., from Heidenhain, may be used as position sensors, and analog displacement sensors with 4 - 20 mA signals, e. g., from Balluff, may be used.

Application in hydraulic multi-spindle automatic lathes
Beckhoff's AH2000 hydraulic controllers are already being put to practical use at Alfred H. Schütte GmbH & Co KG in Germany, a specialist manufacturer of multi-spindle automatic lathes. The company's A36 eight-spindle unit, which was launched this year, uses a total of 15 AH2003 hydraulic controllers. The highlevel control offered by Beckhoff's C6250 Industrial PC provides overall machine coordination, and full software-based axis interpolation is implemented via TwinCAT NC I with an integrated camshaft module. Interfacing of the drives is achieved using six Profibus MC fieldbus branches, and up to eight drive controllers can be connected via the two-channel FC3102 PC fieldbus cards from Beckhoff. The AH2003 hydraulic controller handles position control, and the high scan frequency yields particularly good control results. Further application options for Beckhoff's new AH2000 hydraulic controller range include, for example, revolving automatic machines, punching or nibbling machines, bending machines, and high-speed presses.