The Delta-Tau PMAC2 controllers in a VME form factor are used at the Gemini observatory to control the telescope mount (Azimuth, Elevation), the Cassegrain rotator / Cable Wrap and all the mechanisms of the A&G Unit and are therefore responsible for the optical quality of both telescopes.

Even if Delta-Tau supported in a case by case basis some sparing for special clients in the past, this generation of controllers along with the Turbo PAMC family in VME form factor are already obsolete or slowly passing into obsolescence. Note that the recent industrial context (Acquisition of Delta-Tau by OMRON in July 2015) will surely consolidate the rationalization of Delta-Tau's production lines in a mid-term time scale.

The last trade-off study for the A&G Upgrade project in terms of "Motion Control System Upgrade" led to the last generation of Delta Tau's PMAC controller with a versatile/expandable architecture. A MACRO RING (fiber optic) architecture of “highly integrated” Power Brick controllers (controller & amplifier inside a 1.4Ghz real time kernel linux machine) supervised by a POWER PMAC Etherlite was indeed proposed. This will not only provide 20 more "obsolescence free" years to the A&G control system but also optimize its reliability and maintenance and pave the way for future upgrades.

In the first part of the talk I will briefly present the A&G unit design and current limitations that motivated the upgrade.

Then the POWER PMAC Controllers will be described together with the new Development Environment (IDE) and the architecture defined for the A&G.

During the third part I will present my hardware and Software realizations starting with the electro-mechanical test bench designed to support future developments on POWER PMAC at Gemini.

After this I will focus on various developments done to demonstrate advance features of these new controllers and to propose some optimizations in terms of control system for the A&G unit.

Among them I will detail a trajectory generation/tracking strategy, optimized velocity profile, following modes and backlash compensation methods a key issue for the most critical mechanisms of the Telescope.

Conclusions and perspectives will be finally presented.