Affordable processing power has been strategic in allowing the migration of digital closed loop control technology into the heart of hydraulic servo actuation products. The most recent developments have been within the control valve itself and are already paying dividends, for example: improved performance characteristics; rapid customisation to suit application needs; and user adjustability of key valve parameters. The issues of standardisation and modular design have also played a big part in shaping the valves of the future. The Moog DIV digital interface valve provides an example of the new technology in action. The name DIV is in reference to the CANopen communication protocol used to replace (or complement) the conventional +/-10V or +/-10mA analogue interface. However the onboard 32bit floating process allows for much more than this. At the core of the valve, digital technology is used to shape the motor current driver and provide smart algorithms for more effective handling of the motor and spool flow force characteristics. The digital spool position loop includes improvements to the active damping control to ensure faster and more stable operation under all conditions. The inclusion of an onboard pressure transducer (optional) and PID closed loop controller allows the same valve to be used in any one of three operating modes: Q – flow P – pressure; or P/Q – flow, with pressure limiting. These features make the DIV ideally suited for the control of position, speed, load or power applications.
