"Control and Guidance Complexities of Aerospace Vehicles"

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Dr. BN Suresh

Chancellor, Indian Institute of Space Science and Technology, Thiruvananthapuram

Presents:

"Control and Guidance Complexities of Aerospace Vehicles"

Thursday, July 12, 2018

11:00am

Guggenheim 133 (Lees-Kubota Lecture Hall)

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 Abstract:

This presentation focusses on the intricacies of  Control and Guidance(C&G) system design used for in  space transportation system and its validation. The primary objective of the  space  vehicle is to inject the satellite into the targeted orbit within the specified dispersion band and also  to bring back the module from the space   to earth depending on the requirement.  The   C&G system plays a complex role     in   stabilizing  the vehicle along the desired path to achieve the orbit within  the specified accuracy against  the wide range of dispersions in various parameters like propulsion, aerodynamics,   ground and upper atmosphere winds etc. In addition, a wide variety of internal and external disturbances during the flight make the functions of control and guidance very complex. The navigation system  on-board provides the instantaneous rotational and translational response of the vehicle during the flight.   While the guidance system generates the  desired vehicle attitude  steering command to realize the optimum trajectory in real time, the vehicle control system, comprising of autopilot and control power  plant steers the vehicle to follow the desired attitude.

The    C&G system must  ensure  the integrity of the vehicle during flight and to direct the vehicle to achieve the intended target under all possible environments.  The  C&G  system of the vehicle is generally configured with  three distinct  loops: (i) inner most loop consisting of control power plant with  high bandwidth,   (ii) middle loop, autopilot with fast response and (iii) the outer loop with rather slow response, concerning  navigation and guidance.   The design and validation of this system is very complex since it  encounters high level of interaction, with a number of  vehicle sub systems   like propulsion, aerodynamics, structure, actuators, sensors, liquid sloshes and also the engines or nozzles used for control.

The demand on control force and impulse  is to be carefully assessed  so as to   restrict them within the   capability of control power plants.  The  structural loads in terms of axial and bending loads should not exceed the design limits of the structures and their   design should be highly robust . Guidance function starts at  lift-off  and continues till the final target conditions, during the atmospheric phase  with open loop guidance and outside the atmospheric phase with closed loop guidance.      The guidance law  has  to be robust to cater to larger deviations of vehicle trajectory and  to have provision for fault detection and isolation. The talk highlights the complexities of control and guidance design along with various processes involved in the design and validation needed for the clearance of the system for the flight.