Integrated closed-loop drives
Original article date: October 1999
An innovative positioning unit has the motor and drive close-coupled. WAYNE BROWN finds out the implications
On the face of it the Icla positioning drives look like a motor of some sort, having a shaft, a body and a cable entry. But take a closer look and you will see that SIG Positec has squeezed a gearbox, motor, encoder, power stage, microprocessor and fieldbus interface into a single unit.
What this means is that, given a fieldbus and central controller, you can download an instruction to the Icla drive and it will then move to the required position and stay there until it receives the next instruction. Indeed, you will notice that there is no mention of a brake so far, and that is because the high holding torque of the brushless DC motor is sufficient to maintain the position under normal conditions. However, if there should be a disturbance, the drive’s real-time position correction will come into play and bring the drive back into position.
One of the most obvious advantages of this all-in-one configuration is that you no longer need to find cabinet space for the motor controller. Time and money can also be saved because of the simplicity with which the integrated unit is mounted. In terms of electrical connections, all that is required is a bus link and a suitable power supply.
Of course, the bus link is bidirectional so, as well as sending instructions to the drive, the central controller can also receive diagnostic data. SIG Positec supplies a software package with the Icla units so that configuration, operation and remote diagnostics are made as quick and simple as possible.
Despite the innovative configuration, there have been no compromises on accuracy or torque – either running torque or holding torque. Four different gearbox options are being launched, giving nominal speeds of 30 to 220rpm and nominal torques from 3.5 to 12Nm.
Typical applications are anticipated to be in the fields of printing, packaging, and the wood, metal and plastics processing industries where ‘push-button’ format adjustments are frequently required on machines.
We have already seen several motors introduced with inverters mounted on their bodies, but we certainly like the look of this fully integrated positioning drive.
- SIG Positec
October 1999