The Controller/Drive Sandwich

And hold the wires, please

One ongoing debate in the realm of motion control is whether a system should have centralized (one controller for several axis of motion) or distributed (one controller per motor) intelligence. Much of this discourse has been spurred by the reduction in controller size — many companies are packaging controllers directly onto motors, while separate, stand-alone devices can disappear inside a coffee mug. Ultimately, the control system becomes less cumbersome, allowing machines to take less floor space or to increase the range of functions they can perform within a given envelope.

The engineers over at Galil Motion Control Inc, Rocklin, CA, took the size issue for a centralized controller to another level — they designed their DMC-21x3 control boards, introduced earlier this year, to couple directly to their own amplifier boards. The latest version, shown here, combines the AMP-20540 amplifier, which is designed for driving four brushless or brushed motors up to 500W, with the DMC-2143 four-axis controller. A 96-pin DIN connector provides the link between the two boards, eliminating the need for a wiring harness between controller and drive.

Typically half-the-size-and-price of box-level Ethernet controllers, the company’s DMC-21x3 series includes such high performance features as 1-8 axis control of step or servomotors, 10-BaseT communications with RS232 port, and various modes of motion like point-to-point positioning, jogging, linear and circular interpolation, electronic gearing, ECAM and contouring.

The AMP-20540 contains four transconductance, PWM amplifiers, each capable of driving brushed or 3-phase brushless motors up to 500W per axis. The amplifier also accepts 18 to 60 VDC and outputs 7A of continuous current. PWM switching frequency is 60 kHz. Additionally, since the AMP-20540 is attached to the DMC-21x3 controller, the system offers programming and diagnostics capability. The AMP-20540 provides protection for over-current, short-circuit, under-voltage, over-voltage and over-temperature; and a new command — TA — which allows easy interrogation of errors and status. Another command set sent via the DMC-2143 facilitates Hall sensor set-up and helps ensure that the brushless phases are kept properly aligned. The amplifier gain can be specified for 0.7, 0.4, or 0.2 A/V using another new command — AG.

For applications requiring fewer than four amplifiers, Galil provides the AMP-20520 two-axis model. In addition, other multi-axis amplifier boards that mate directly to the DMC-21x3 Ethernet motion controller include:

•SDM-20240 full- and half-step drives for four stepper motors
•AMP-20340 linear amplifiers for driving four 20-watt brush servo motors
•AMP-20440 PWM amplifiers for driving four 200-watt brush servo motors
•ICM-20100 interconnect for interface to external amplifiers

For a nominal tooling fee, the company can create custom amplifier boards that mix-and-match amplifier types and power output per axis.

—RM