The next generation motion control system of the upgraded GMRT

The GMRT servo system implements motion control systems to position each of thirty 45-m antennas towards astronomical sources and track these during astronomical observations with a precision of 10 arc-seconds, even in presence of
gusty winds up to 40 kmph, which can be challenging due to relatively low stiffness of these antennas. It also positions the feeds that are located on the four faces of the rotating turret at the prime focus thereby enabling selection of one of the four operating Bands for astronomical observations. While these systems have performed well since 1995, the servo-motors, drives, interlock and servo-computers faced obsolescence. In the recent upgrade, the challenge was to upgrade these with state-of-art embedded systems, which are relatively obsolescence and radiofrequency interference-free, hand-in-hand with science operation of GMRT in a phased manner. The upgrades in servo-computer and main telescope drive will be described in this talk with details of the validation process and results apart from the management of mass commissioning of the antenna systems. The new features of the upgrade will be described followed by the current developments and future plans for improvement of overall operations of motion control systems.

About the Speakers:
Professor Bhal Chandra Joshi has been working with GMRT since 1993 and has been coordinating the activities of GMRT servo group as its academic coordinator. He obtained Bachelor and Master degree in Engineering from IIT, Roorkee and Mumbai respectively and Masters and doctoral degree in Physics and astronomy. He contributed in the early development of GMRT servo systems with a simulation of the error budget of GMRT antenna, which was also used for tuning system parameters in the motion control system designed with help of Bhabha Atomic Research Centre. He also contributed in commissioning of GMRT antennas in early days and has guided the recently concluded upgrade of the servo system. He works in pulsar astronomy with his main research interests in emission mechanism of radio pulsars, their search and timing and use of pulsars in the discovery of nano-Hertz Gravitational Waves using pulsars, where he leads the Indian pulsar timing array consortium (InPTA).

Shri Shailendra Bagde has been working with GMRT since 1998 in the servo group. He obtained Bachelor in Engineering from Nagpur University. In the late commissioning stage, he contributed towards reliability and stability of servo system's operations by coordinating maintenance of the servo system. He also contributed in the design and development of new solid-state interlocks and PC104-based servo computer and feed positioning system, and contributed towards testing and development of shielded enclosures for BLDC drives.