System Engineering Studies on Induction of Redundant Electromechanical Engine Gimbal Control Actuation System in the Second Stage of Polar Satellite Launch Vehicle

Abstract

This paper describes the system engineering challenges addressed and resolved during the replacement of the simplex electro-hydraulic actuation system with the redundant electromechanical actuation system used for the second stage Engine Gimbal Control of Polar Satellite Launch Vehicle. Required modifications were conceived without affecting existing launch vehicle interfaces and with a minor increase in the overall mass. Electromechanical actuators are highly reliable and easy to test systems and possess a higher shelf life of components compared to electrohydraulic actuators. Redundancy is incorporated in electromechanical actuator and control electronics to improve the Fault-tolerant capability to handle existing single-point failure modes of electrohydraulic actuator. Redundant system implementation calls for significant changes in electrical architecture, mechanical mounting scheme for new add-ons, test methodology to verify redundancy, etc. As part of this exercise, avionics layout of sub-assemblies was reconfigured to accommodate the packages and response of each package location for vibration inputs were studied in detail to arrive at vibration test levels. This paper details the modifications carried out on structural members to take additional loads due to the new elements. Due to the induction of electromechanical actuators, mass impact, actuator sizing, changes in interface elements, changes in electrical and mechanical systems, and their impact on other systems were studied in detail and are provided in the paper. The integrated test procedure was worked out to validate the implementation before the flight.