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Oversampling brings greater accuracy to multi-axis servos
Beckhoff has upgraded the firmware in its AX8000 multi-axis servodrives to support oversampling, allowing multiple sampling of process data within one communication cycle, with the data being transferred via EtherCat. With an oversampling factor of up to 128, this allows higher-level controllers to transmit several setpoint positions or speeds to the drive within one cycle, which the drive then follows. In addition, measured variables can be recorded several times in the drive, and the buffered values can be made available to the controller within a single cycle.
The AX8000 drives are already characterised by high dynamics and short cycle times. The motor current is scanned in cycles measured in microseconds, while the minimum adjustable EtherCat cycle time is 62.5μs. New setpoint values can be transferred to the servodrive every 62.5μs from a motion controller running in an industrial PC. Beckhoff says that comparable control systems usually operate with cycle times of around 1ms.
The oversampling technology – already familiar from Beckhoff’s EtherCat I/Os – will allow, for example, charts in the TwinCat Scope View software to be resolved even more finely.
Synchronisation with other drives – with or without oversampling functions – is possible via EtherCat’s distributed clocks function. The oversampling function can be used in precision machines and systems where high-resolution measured values need to be evaluated.
