Main Menu:

People

Chakravarthini Saaj

Lecturer in Space Robotics

BTech MTech, PhD, CEng, FBIS, SMIEEE, SMAIAA, MIET

Short Biography:

Chakravarthini did her graduation in ‘Electrical and Electronics Engineering’ with distinction and post-graduation in ‘Control Systems’ with distinction and first rank from the University of Kerala, India, in 1996 and 1999 respectively. In 2003, she was awarded a Ph D by the Indian Institution of Technology, Bombay, for her contributions to the field of discrete-time sliding mode control.

She joined the Surrey Space Centre as a research fellow in March 2005. At Surrey, she has worked on diverse space applications ranging from public outreach to planetary rovers and spacecraft swarms. Chakravarthini was the technical lead for a project from the ESA and was successful in securing funding. Also she contributed to another successful research proposal to PPARC. She was appointed as a lecturer in Space Robotics in July 2007. Prior to joining the Surrey Space Centre, she worked as a Research Fellow at the Technical University Hamburg-Harburg, Germany and as a Visiting Research Associate at King’s College London.

Chakravarthini is a chartered engineer, Fellow of BIS, senior member of IEEE and AIAA and member of IET, and IEEE Women in Engineering. Since 2002, she has been a reviewer for IEEE and IET journals and various conferences. She has authored and co-authored many research proposals in collaboration with various leading national and international research groups. She has numerous publications in international journals and conferences to her credit. She also has extensive undergraduate and postgraduate teaching experience.

She is actively involved in promoting engineering and space education in the UK. She has delivered several public/outreach lectures to various schools and colleges across the UK. She won the 'Visiting Lectureship' from the Engineering and Technology Board, UK in 2008 and delivers lectures to inspire young people to take up a career in engineering. This two year 'Engineers Make It Happen' campaign is co-sponsored by the Royal Academy of Engineering, Elesevier publications and PKP Communicators.

Research Interests:

At Surrey, Chakravarthini specializes in robotic exploration of space and her research interests are broadly in the following topics:

Modelling and control of mobile robots and robotic manipulators for space exploration.
Guidance, navigation and traction control of planetary rovers and autonomous ground vehicles.
Robotic on-orbit servicing.
Micro/Nano-scale robot swarms.
Pin-point landing systems for planetary landers.
Spacecraft swarm formation flying, dynamics and control.
Launch vehicle and Flight control.
Systems Identification, modelling and control of non-linear systems.

Ph. D, M. Sc/M. Eng, UG projects are available in the above topics. A brief description of the projects is given below, under research projects.

Research Collaborations:

Chakravarthini works closely with all academics in the Surrey Space Centre and technical experts at the Surrey Satellite technology Ltd, on various aspects of space exploration. She has also established links with ESA, ISRO, DLR, NASA, EADS Astrium, BAE Systems, QinetiQ, SciSys, Mississippi State University, Cornell University, Virginia Tech, King's College London, University of Leicester, University of Bremen, Technical University Hamburg-Harburg, Germany and Indian Institute of Technology, Bombay.

Teaching:

Chakravarthini teaches the following modules, for which she is the module co-ordinator:

2007- to date: Level M (Elec. Eng.) Space Robotics (EEM.ROB)
2008- to date: Level HE3 (Elec. Eng.) Power Electronics (EE3.PWE)
2008-to date: Level HE2 (Elec. Eng.) Power Conversion (EE2.PWC)
2009-to date: Level HE2 (Elec. Eng.) Electronics VI (EE2.el6)

Departmental Duties:

Dr. Saaj is actively involved in many public outreach activities to promote engineering education in the UK. Administrative roles include managing post-graduate and under-graduate course schedules and conduction of examinations. Other administrative duties include marketing/Schools outreach activities relating to the Space Centre and managing Space Centre's research infrastructure.

Selected publications / conference presentations:

Seelcted Publications:

Papers in Refereed International Journals:

1. C. M. Saaj and B. Bandyopadhyay, “Output Feedback Sliding Mode Control of Linear Second Order Systems-A Moving Switching Line Approach”, Systems Science Journal, Vol. 27, No.3, pp. 5-22, 2001.
2. C. M. Saaj, B. Bandyopadhyay and H. Unbehauen, “A New Algorithm For Discrete-Time Sliding Mode Control Using Fast Output Sampling Feedback”, IEEE Transactions on Industrial Electronics, Vol. 49, No. 3, pp. 518-523, 2002.
3. B. Bandyopadhyay and C. M. Saaj, “Algorithm on robust sliding mode control for discrete-time system using fast output sampling feedback”, IEE Proceedings - Control Theory and Applications, Vol. 149, No.6, pp. 497-503, November 2002.
4. C. M. Saaj and B. Bandyopadhyay, “Variable structure model following controller using non-dynamic multirate output feedback”, International Journal of Control, Vol. 76, No. 13, pp. 1263-1271, 2003.
5. C. M. Saaj, B. Bandyopadhyay and H. Unbehauen, “A minor correction to “A new algorithm for discrete-time sliding mode control using fast output sampling feedback” ”, IEEE Transactions on Industrial Electronics, Vol. 51, No. 1, pp. 244-247, Feb. 2004.
6. C. M. Saaj, V. Lappas, D. Richie, H. Schaub, D. Izzo, “Hybrid propulsion system for spacecraft swarm aggregation using hybrid propulsion”, Journal of the British Interplanetary Society, Vol. 60, No. 7, pp. 268-274, July 2007.
7. M. A. Peck, B. Streetman, C. M. Saaj and V. Lappas, “Spacecraft formation flying using Lorentz forces”, Journal of the British Interplanetary Society, Vol. 60, No. 7, pp. 263-267, July 2007.
8. C. M. Saaj, C. Underwood, C. Noakes, D. W. G. Park and T. Moore,“ The Science and Technology behind Galileo- Europe’s GPS’, Journal of the British Interplanetary Society, Vol. 61, No. 3, pp. 91-98, April 2008.
9. V. Lappas, C. M. Saaj, D. Richie, H. Schaub, D. Izzo, “Hybrid propulsion system for formation flying using electrostatic forces”, submitted to Aerospace Science and Technology, 2007.
Recent International Conference Papers:
1. Scott, G. P., C. M. Saaj, E. Moxey, Proceedings of the AIAA Space 2008 Conference, San Diego, USA, September 2008.
2. Scott, G. P., C. M. Saaj, E. Moxey, Proceedings of the Towards Autonomous Robotic Systems Conference, Edinburgh, UK, September 2008.
3. C. M. Saaj and S. Parsa, to appear in the Proceedings of the 10^th ESA Workshop on Advanced Space Technologies for Robotics and Automation, Noordwijk, The Netherlands, 11-13 November, 2008.
4. Lappas, V., Pechev, A., Saaj, M., Moxey, E., Underwood, C., Vladimirova, T., Palmer, P., Gao, S., Gao Y., Sweeting, M., Proceedings of the 10^th ESA Workshop on Advanced Space Technologies for Robotics and Automation, Noordwijk, The Netherlands, 11-13 November, 2008.
5. Scott, G. P., C. M. Saaj, E. Moxey, Proceedings of the International Society of Terrain Vehicles Systems Conference, Turin, Italy, November 2008.
6. G. Scott, B. Smith, C. M. Saaj, to appear in the Proceedings of the 4th International Conference on Recent Advances in Space Technologies, Istanbul, Turkey, 11-13 June 2009.
7. D. Sancho and C. M. Saaj, to appear in the Proceedings of the European Control Conference, Budapest, Hungary, 23-26 August 2009.
8. C. M. Saaj, V. Lappas, D. Richie, H. Schuab and V. Gazi, to appear in the Proceedings of theEuropean Control Conference, Budapest, Hungary, 23-26 August 2009.
9. Mahmood, W. and C. M. Saaj, “to appear in the Proceedings of the European Control Conference, Budapest, Hungary, 23-26 August 2009.
10. S. Seyyedi Parsa, C. M. Saaj, C. Underwood, to appear in the Proceedings of the International Conference on Space Technology, Thessaloniki, Greece, 24-26 August, 2009.
11. G. Scott and C. M. Saaj, to appear in the Proceedings of the AIAA Space 2008 Conference, Pasadena, US, 14–17 September 2009.
12. B. Smith and C. M. Saaj, to appear in the Proceedings of the 60th International Astronautical Congress, Daejeon, Republic of Korea, 12-16 October 2009.
13. C. M. Saaj, S. Bandyopadhyay and B. Bandyopadhyay, to appear in the Proceedings of the 60th International Astronautical Congress, Daejeon, Republic of Korea, 12-16 October 2009.
14. A. Khorram, S. Parsa and C. M. Saaj, to appear in the Proceedings of the 60th International Astronautical Congress, Daejeon, Republic of Korea, 12-16 October 2009.

Research Proposals

Chakravarthini has authored and co-authored several research proposals on the following topics:

1. Integrated Robust Autonomous Navigation and Control System for Planetary Rovers and Unmanned Ground Vehicles.

2. Navigation & locomotion control for ExoMars rover (Funded from PPARC)

3. Electrostatic Forces for Satellite Swarm Navigation and Reconfiguration (Funded by ESA)

4. Techniques to improve spacecraft monitoring using on-board visual systems

5. Advanced Injectors for Chemical Rockets Inspired by Ink-jet Printing Technology

6. Active Coating for Position and Attitude Control

7. Identification of Linear Parameter-Varying Models for Gain-Scheduling Control

Research Projects

Guidance, navigation and traction control of planetary rovers and autonomous ground vehicles: The need for a better navigation and traction control algorithm is acutely felt in the field of extra-terrestrial rovers because of past failures and tremendous costs of missions. This study aims to identify the shortcomings of existing technology and to develop cost effective solutions using techniques like artificial potential field method and behaviour-based control. On-line slip estimation of rover wheels is another aspect of this study. It is intended to extend these algorithms for unmanned ground vehicles.
Rigid and flexible robotic manipulators for on-orbit servicing, assembly and self-repairing: Force feedback control of the manipulator end-effector whilst capturing the client spacecraft and handling delicate on-board components is under investigation. It is proposed to use virtual reality to simulate the interaction between the freeflyer and client satellite. The freeflyer servicer spacecraft is proposed for servicing satellite clusters (GPS/Galileo constellations). Chakravarthini and her colleague Dr. Eddie Moxey are initiating this move in the OOS industry. Chakravarthini has a research interest in self-repairing/servicing robots and flexible lightweight manipulators.

Legged robots for future space exploration: The walking robot technology is still premature compared to wheeled mobile rovers. Chakravarthini’s research interest is in developing an autonomous platform for a walking robot. This project aims to develop a low cost prototype of a four/six legged robot that is capable of walking on challenging terrains that cannot be explored by wheeled rovers.

Modelling and identification of linear parameter varying models for gain scheduled control:

At Surrey, Chakravarthini specialises in motion control of a six-dof robot manipulator. The aim is to develop modelling and identification strategies based on gain-scheduling techniques for linear parameter varying systems. The resulting controller will have performance and lower complexity than advanced control schemes based on feedback linearization (computed torque).

Autonomous micro and nano-scale robot swarms: The advancement in the field of micro-electronics and nanotechnology has revolutionised the space industry. The goal of this study is to use commercial-off-the shelf (COTS) components and equipment to develop many small inexpensive micro/nano rovers to work co-operatively instead of one very expensive and large rover. Chakravarthini together with her colleague Dr. Yang Gao, is investigating the concept of robot swarms.

Pin-point landing systems for planetary landers: Surrey Space Centre and Surrey Satellite Technology Ltd together with Mississippi State University are working on a NASA funded project on developing a low cost pin-point lander technology for future planetary landers. Chakravarthini is working together with other team members to develop efficient GNC algorithms for the proposed Entry Decent and Landing System (EDLS).

Sliding mode control for spacecraft and robots: Chakravarthini has several years of research experience in Sliding Mode Control (SMC). She developed the concept of ‘Fast Output Sampling Sliding Mode Control (FOSSMC)’. Chakravarthini is developing a sliding mode observer for estimating the motion parameters of robot manipulators and mobile robots. She currently aims to apply the FOSSMC technique for spacecraft swarms and robots.

Formation flying of satellite swarms using Coulomb forces: Chakravarthini was the lead researcher for a project funded by the European Space Agency, on formation flying of satellite swarms using electrostatic forces. A hybrid propulsion system using Coulomb forces and conventional electric thrusters for satellite propulsion in high Earth orbits was developed. This project now aims to further investigate various reconfiguration scenarios suitable for formation flying missions.

Launch vehicle dynamics and control: The launch vehicle is aerodynamically unstable, which puts a great demand on the vehicle autopilot and control system with respect to stabilization and control. This study aims to develop a digital autopilot, which would demonstrate robustness compared to other elegant classical approaches used widely. It is proposed to develop an H-Infinity controller and to compare and validate its performance with conventional controllers, for various dynamic models of the launch vehicles.

Contact Details

Email	c.saaj@surrey.ac.uk
Telephone	+44 1483 682225
Room
Postal Address	Faculty of Engineering & Physical Sciences University of Surrey Guildford GU2 7XH United Kingdom