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Ethernet AC drives ease machine motion control

Posted: 12 Mar 2007 ?? ?Print Version ?Bookmark and Share

Keywords:Ethernet? AC drive? motion control? machine control? motor control?

Three-phase AC drive from Baldor

Baldor Electric Company has launched the Ethernet Powerlink three-phase AC drives offering all major motion control functions including single-phase drives, a motion and machine controller, and development tools. This technology promises machinery OEMs a versatile control platform, thereby improving performance, simplifying the control architecture and reducing costs.

"The technical benefits of a high speed machine network have been well publicized, but it's the simple factors of product availability and system cost savings that are being overlooked," said David Greensmith of Baldor. "Machine builders are definitely sold on the system building benefits of the architecture. For example, for each drive node, a single Ethernet CAT5e cable tends to eliminate somewhere in the region of 40 to 50 cable stripping, soldering and assembly tasks. The completion of the product range with three-phase drives opens the technology to machinery OEMs."

All-Ethernet systems
The three-phase drive is beneficial in small to medium multi-axis systems as it reduces costs mainly in the area of simpler engineering, control hardware, cabling and assembly. It allows the user to build all-Ethernet systems with the choice of motor technology for each axis, from small to large loads. Rotary and linear versions of brushless servo and AC vector motors are all software selectable.

It can also be used to provide software-centric, reconfigurable equipment as its single controller can manage up to 200 different machine control components such as I/O, absolute encoders, Ethernet PowerLink DS402 positioning drives, stepper motors, as well as up to 16 interpolated axes. The machine builders could replace pneumatic actuators with stepper or servo motors with no increase in controller hardware, thus eliminating the costs and issues associated with maintaining a secondary supply of clean compressed air.

Unlike traditional motion networks, the Ethernet network allows systems to continue with the traditional central controller if preferred, thus coordinating all drives in profiled torque, speed or position modes. However, these axes can also be self-controlled positioning devices (DS402-compatible positioning drives) that respond on command and consume little central processing overhead. In addition, intelligent (programmable) drives can be employed in a system to implement standalone axes, or to implement the complete motion system.

100Mbps network
The bandwidth of the 100Mbps Ethernet network also simplifies machine building by merging the functionality of a fieldbus and a motion bus into one system. The total network visibility capability of this common network allows it to communicate to device service port functionalities such as firmware updates, configuration and diagnostics.

Applications can be implemented using two flavors of Ethernet. The Powerlink provides a real-time performance that makes its suitable for handling demanding motion, as well as a means to link with standard Ethernet networks. A simple gateway device can be added into a PC or machine network to allow any PC controller with its standard Ethernet interface to communicate with the real-time motion-control hardware.

Alternatively standard TCP/IP protocols can be used if the automation in question does not have any demanding time synchronization or multi-axis coordination considerations. In this case, free ActiveX development tool provides programmer's API interface to every function of the Mint motion and machine control language built into the hardware, allowing users to issue commands to the motion hardware without needing to understand Ethernet protocols. This helps the developers to create Windows-based PC applications that can communicate with the motion hardware via Ethernet.

In either case, the use of Ethernet allows organizations to access the machine remotely, to view status, perform diagnostics etc. This approach uses standard routing network technologies and integrates firewall security features such as NAT, MAC address filtering and port blocking etc.

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