NONLINEAR SIGHTLINE CONTROL
Lead Research Organisation:
University of Glasgow
Department Name: School of Engineering
Abstract
A sightline system encompasses all subsystems and algorithms necessary for accurate target tracking, pointing and stabilisation of a sensor line-of-sight. Each system integrates technologies obtained from several established research domains. The strategic intention of this research proposal is to develop sightline control as an independent, coherent research topic for the first time in the UK. The first step in achieving this objective is to apply rigorous research methodology to two of the most important sightline control problems / nonlinear nadir control and long-range imaging.The airline industry is severely hit by the economic after effects of terrorist actions (as seen post 9/11). There is therefore a need to adopt technologies that will safeguard aircraft security when operating in high-risk areas. One of the key military aircraft defence technologies identified by the U.S. Department of Homeland Security as a priority transition to the civil sector is the Directed Infra-Red Countermeasures (DIRCM) system (a technology in which the UK is a significant stakeholder). The purpose of such systems is to defend friendly aircraft against the threat posed by Man-Portable Air Defence Systems (MANPADS) / typically shoulder-launched Surface-to-Air Missiles (SAMs) / by tracking the incoming IR-guided missile and confusing the guidance mechanism through delivery of a jamming signal onto the missile seeker. However, for gimballed sightline systems, there exists a pointing angle that, were the target to pass through, infinite rate demands would be sent to one of the axes. This is known as the nadir and introduces significant additional tracking error, which is potentially disastrous for the aircraft. It is the intent of this project to investigate the applicability of several advanced control algorithms, using predictive methods, to minimising tracking error around the nadir and so improve the survivability of the aircraft.To obtain high-resolution images it is essential that sightline jitter be minimised, as jitter is often the dominant contributor to roll-off of the image modulation transfer function (MTF) at high spatial frequencies (blurs-out fine detail in the image). Jitter can be decomposed into two further sub-groups comprising sightline motion introduced by mechanical imperfections in the steering system (notably friction and vibration) and aberrations external to the system introduced by atmospheric turbulence. Control solutions for reducing mechanical jitter have been well researched, using, for example, classical control, friction estimation and robust methods, but very little nonlinear controller activity has been documented. The astronomical community has used adaptive optics for several years to correct for atmospheric distortions in the image by measuring the wavefront and using this information to control an extremely fast deformable mirror. However the complexity of such systems makes them unsuitable for deployment in an airborne environment. The alternative approach proposed here is to investigate the mapping between sightline jitter under nonlinear control and the shape of the MTF. The resulting controllers will, for the first time, be directly coupled to the quality of image obtained, which should see significant improvements in the attenuation of mechanical jitter while simultaneously taking the first steps in researching image-based atmospheric correction.
Organisations
- University of Glasgow (Lead Research Organisation)
- Defence Science & Technology Laboratory (DSTL) (Collaboration)
- Selex ES (Collaboration)
- Applied Control Technology Consortium (Collaboration)
- Defence Science and Technology Laboratory (Project Partner)
- Leonardo (United Kingdom) (Project Partner)
- Industrial Systems and Control (United Kingdom) (Project Partner)
People |
ORCID iD |
David Anderson (Principal Investigator) |
Publications
Anderson D
(2007)
Sightline Jitter Minimization and Shaping Using Nonlinear Friction Compensation
in International Journal of Optomechatronics
D Anderson
(2007)
Multirate and nonlinear controllers for low-cost laser tracking systems
D Anderson
(2008)
Application of MPC and Sliding Mode Control to IFAC Benchmark Models
Anderson D
(2009)
Fast Model Predictive Control of the Nadir Singularity in Electro-Optic Systems
in Journal of Guidance, Control, and Dynamics
Description | There were two significant contributions obtained from this grant. The first was a predictive controller design for the management of tracking error in the neighborhood of gimbal lock. The second was the creation of the sightline control toolbox, a computational method for optimizing the system-level design parameters of electro-optic tracking systems. |
Exploitation Route | The nadir control algorithm has been implemented on at least one industrial product (SELEX ES). |
Sectors | Aerospace Defence and Marine |
Description | The nadir predictive control algorithm has been used in at least one industrial product line. The Sightline control toolbox was also used as a basis for further investigation in tribology, i.e. design of optimal friction-compensation algorithms for imaging systems. |
First Year Of Impact | 2008 |
Sector | Aerospace, Defence and Marine |
Impact Types | Economic |
Description | Applied Control Technology Consortium |
Organisation | Applied Control Technology Consortium |
Country | United Kingdom |
Sector | Private |
Start Year | 2006 |
Description | DSTL |
Organisation | Defence Science & Technology Laboratory (DSTL) |
Country | United Kingdom |
Sector | Public |
Start Year | 2006 |
Description | Selex-Galileo |
Organisation | Selex ES |
Department | SELEX Galileo Ltd |
Country | United Kingdom |
Sector | Private |
Start Year | 2006 |
Title | Sightline Control Toolbox |
Description | Allows the user to design optimal sightline control architectures for maximizing image performance. |
Type Of Technology | Software |
Year Produced | 2010 |
Impact | Architecture was used as the basis for MAVERIC. |