Integrated Motion Control
Applications
Smart Belt with ControlLogix and Ultra3000
Smart Belt systems are widely used in packaging applications to convert randomly spaced product into evenly spaced product that's properly phased to the infeed of another machine, such as a flow wrapper or cartoner. There are many variations of a smart belt depending on the required speed and accuracy of the placement of the product from the infeed to the outfeed. Factors such as speed and accuracy and product characteristics usually determine how many correction belts are used. This can range from two belts to as many as ten belts.
Randomly spaced product is typically fed with the use of a conveyor driven by an induction-type motor. The servos that make up the smart belts follow the infeed of the next conveyor down stream so that the smart belt's speed is matched to that machine's speed.
The registration input from the sensor on each smart belt senses the product and makes position corrections based on error calculations performed in the controller. The corrections are performed on a percentage of the total error, based on whether the belt is performing a coarse or fine correction. The first belts in the process are usually coarse correction belts and typically make a large correction for as much as 70 to 100% of the total phasing error amount. The last belts perform fine correcting for 100% of the measured remaining phasing error even though the total error is smaller, relative to what it was at the beginning of the correcting process.
Rockwell Automation Solution
ControlLogix with embedded Motion is the control of choice for the Smart Belts. A typical configuration would include using a 1756-M08SE SERCOS Interface™ Motion Module that links with fiber optic cable to the multiple Allen-Bradley Ultra3000 SERCOS Servo Drives with MP-Series Low Inertia Motors. MP-Series Low Inertia Motors have been chosen for Smart Belt axes because of their high acceleration and deceleration capability, as well as their compact size. Machine operators can use PanelView600 Operator Interface connected to the ControlLogix Platform using ControlNet in order to change process configuration information and monitor actual machine performance. RSLogix 5000 Programming Software provides flexibility in setup of the control hardware, as well as programming and diagnostics.
Through the use of RSLogix 5000, all motor and drive parameters are defined as part of the motion axis configuration and require no secondary software package for machine or drive setup. The ControlLogix controller automatically configures the drives over the SERCOS interface at power-up. This allows for drives to be powered-up right out of the box with little configuration by the user. Programming is simplified as well with the use of global controller tags and local program tags that allow each correction belt to have identical logic yet function separately. Error detection is simplified with the use of hard registration inputs for each axis that can be cross-referenced to the master axis through a precise position and time-based interpolation process.