Eaton Corp needed a small, general-purpose motion controller for use in its 300mm medium current ion implanters. The company's engineers wanted a solution that could improve reliability while at the same time reducing both cost and size. They needed to control three axes of motion with low current DC brush-type motors, and it was vitally important that their motion controller generate smooth trajectories.

The Eaton engineers chose the MC1401A servo control chipset from Performance Motion Devices (PMD) for their controller after investigating a number of other solutions, including single-axis chips and off-the-shelf motion cards. The MC1401A comprises two programmable chips-a Digital Signal Processor (DSP) for profile and PID calculations and an Application Specific Integrated Circuit (ASIC) to handle motor-specific functions such as encoder feedback. Available in 1, 2 and 4-axis configurations, the PMD chipset also offers S-curve profiling.

"PMD's chipset was selected primarily for its S-curve motion profile capability," explains Mike Harris, line product manager at Eaton. "Previous generation controllers were limited to trapezoidal moves, which can put increased stress on the load or the drive mechanism, resulting in vibration. By using S-curve profiles, the cycle time of certain moves was reduced by as much as 20% in Eaton's application," Harris adds.

Eaton's new controller, Micro3, met all the company's expectations for cost and size. "The high integration and PWM interface of the PMD chipset helped Eaton reach these goals by enabling a significant component count reduction over previous designs," observes Harris. In addition, by allowing tighter positioning control throughout the move profile and improved positioning accuracy at the profile destination, the chipset actually helped improve performance and increase throughput for the ion implanter itself.