Distributed servo drive system for modular machines

Beckhoff

The AMP8000 distributed servo-drive system provides support for the implementation of modular machine designs. The system involves having a servo drive directly integrated into a servomotor, with a compact design. In this way, the power electronics have been relocated to the machine, reducing space requirements in control cabinets to a single coupling module. In addition, decentralised distribution modules and the universal EtherCAT P solution further optimise the modular machine design approach.

The system consists of three main components – a single-channel or alternately dual-channel coupling module that forms the starting point, and the only component that still needs to be installed in the control cabinet. The coupling module establishes a connection between the DC link, 24V DC supply and EtherCAT communication. For use with the high-performance AX8000, the AX883x coupling module is connected to the AX8000 supply module in order to provide a link to the IP 65-rated devices with one or two outputs. In combination with the AX5000 digital compact servo drive, the AX503x coupling module can also be used in stand-alone mode due to an integrated power supply unit. In this way, 20A (per output in the case of the AX883x and as sum current in the case of the AX503x), 600V DC link voltage, 24V power supply and EtherCAT networking are available via the EtherCAT P outputs (B23 sockets).

This power is initially supplied to an AMP8805 distribution module as a second system component. As an IP65-rated component that is integrated into the machine layout, it supplies up to five AMP80xx distributed servo drives. It can be mounted either directly (brick style) or using a bracket available as an accessory (book style) and adapted ideally into individual machine designs. The distribution module has an internal capacitance of 1120 µF to support the DC link. Additional EtherCAT P Box modules, such as for I/Os or for a second feedback system, can be connected simply and quickly via an additional EtherCAT P M8 output.

The third system component is the AMP80xx distributed servo drive. It is identical to the standard servomotors in the AM8000 series with regard to its mounting dimensions and performance data. Only the overall length has increased in comparison with the standard motors due to the integrated power electronics. Since this added length is not usually critical for the installation, most existing machine designs can be upgraded without the need for modification. The AMP80xx distributed servo drives are initially available in the flange sizes F4 and F5. Various versions are available with rated outputs of 0.61kW to 1.18kW and standstill torques of 2.0Nm to 4.8Nm (F4) or rated outputs of 1.02kW to 1.78kW and standstill torques of 4.1Nm to 9.7Nm (F5). The STO and SS1 safety functions are integrated as standard and a range of extended safe motion functions are currently being prepared. In addition, the new flange sizes F3 and F6 are in development and will complement the AMP8000 distributed drive system in the lower and higher power ranges.

Universal cabling and cascadable installation via EtherCAT
The components in the AMP8000 system are universally connected with the uniform One Cable Automation (OCA) cabling technology, which connects via identical cross-sections and connectors. This is a dynamic, drag-chain compatible EtherCAT P cable with ECP-B23 connectors, which means the one cable solution features a hybrid cable that combines EtherCAT P (communication plus 24 V system and peripheral voltage) with additional power cores. Also it is worth noting that preassembled cables and connectors facilitate easy installation and minimise errors during cabling.

The AMP8000 system is also cascadable via the distribution module, meaning even highly complex machines and plants can have a simple and clear-cut topology layout. For this purpose, one or several additional distribution modules are connected to one of the module outputs in place of a distributed servo drive. For example, one main distribution module can supply five sub-modules, to which a maximum of 25 distributed servo drives can be connected, assuming an adequate supply of power to the individual motors is provided.

Compact drive integration in optimised design
With the AMP80xx, the integration of drive technology has been implemented in a compact design, made possible through the use of the latest output stage technologies. The power module is attached at the rear end of the servomotor shaft, ensuring that the attachment dimensions are identical to those of the corresponding standard servomotors in the AM8000 series. Only the overall length is about seven centimetres larger. For machine builders, this means only a small amount of additional space is required, making it possible to change their drive concepts without any fundamental design modifications.

Apart from the small overall volume, the elegant and slim design of the AMP80xx offers further advantages over certain servomotors commonly encountered on the market, where the power electronics are mounted on top. With the AMP8000, the two dissipated heat sources – motor and power electronics – are separated from each other and ensure much better heat dissipation by design, without the need for additional installation space or heat sinks. As a result, the distributed servo drives attain the same properties as the corresponding standard AM8000 servomotors from Beckhoff.