ADVANCED SPACE VEHICLE CONTROL
1 September 2006
Space Vehicle Control is facing new challenges: providing more performance capabilities for space missions within smaller physical constraints (mass, power). Coupling this with the new challenge to return to the moon and discover Mars, it is important to develop new efficient, robust and cost effective for present and new space missions. 25 participants attended the international workshop from the USA, UK, France, Germany, Italy, Netherlands, Greece and Turkey.
With a total of 19 presentations, the workshop was kicked-off by Surrey’s own Professor Sir Martin Sweeting founder of the Surrey Space Centre and Surrey Technology Ltd discussing the upcoming challenges of small satellite missions.
Dr. Gazi (Turkey) gave an interesting mathematical prospective of path planning of vehicles for different space applications using potential field methods. In the same area Dr. Tsoudros from Cranfield University gave a presentation on path planning techniques for Unmanned Aerial Vehicles using different sensor technologies. Dr Saaj completed the path planning section of the workshop with a talk on spacecraft formation flying control with path planning control based on Dr. Gazi’s work and on a newly developed hybrid method utilising electrostatic forces and electric propulsion. Drag free control is an interesting control concept being investigated to test Einstein’s theories using sensitive 'free' masses within a spacecraft and accurate thrusters for attitude control/compensation.
The next section of the workshop focused on the theme of solar sails. These large thin/light reflective structures are used to propel spacecraft using photons coming from the sun. Remi Drei (Netherlands) from the European Space Agency presented an interesting approach combining attitude control with the trajectory function of a solar sail. Professor McInnes from Strathclyde presented a number of new near term solar sail mission concepts based on non-Keplerian orbit techniques. Dr. Dachwald from the German Space Centre (DLR) presented a realistic plan on solar sail missions for asteroid deflection and sample return missions with a focus on trajectory design. Professor Wie from Arizona State University (USA) gave a talk on a solar sail gravity tractor concept for asteroid deflection, one of the most interesting mission areas currently being researched. McDonald from Scisys (UK) presented the Attitude control design of the LISA/Pathfinder mission one of the most challenging missions for formation flying and attitude control requiring ultra high precision accuracy control.
Following a lunch break, the next two talk focused on the entry, descent and landing control methodologies required for safe Mars landings. Professor Sparkes from Dundee showed some very interesting results on simulating Mars surfaces using low computational intense algorithms. Dave Dungate from Analyticon (UK) presented the design of a computer tool for the trade-off design of entry, descent and landing systems for Mars landers.
The following presentations (6) focused on the design and control algorithms of Control Moment Gyro actuators for agile spacecraft control. Dr. Lappas presented a new CMG control logic for miniature CMGs with gimbal angle constraints, work co-authored with Prof. bong Wie. Mr Underhill of Honeywell (USA) presented two interesting talks on CMG singularity avoidance laws that guarantee singularity avoidance using singularity free regions. His second presentation highlighted the use of a large agile spacecraft simulator equipped with CMGs for accurate line of sight tracking. Dr Palmer from Surrey presented some new findings on a singularity avoidance law that is exact for a cluster of 4 CMGs using analytic methods. Dr. Pechev (Surrey) presented another singularity avoidance law which does not require the direct calculation of the pseudo-inverse jacobian matrix. Mr. Richie (Surrey/USA) presented a new compact, novel method for sizing combined energy and attitude control systems for small satellites. Finally and to end the workshop, Dr. M. Peck from Cornell presented an interesting approach to the design of twin CMG systems for agile small satellites and the trade off with conventional single gimbal CMGs.
The workshop was divided in three areas: (i) path planning techniques for spacecraft/multi vehicle control (ii) solar sail missions and orbit/attitude control (iii) agile spacecraft attitude control using CMGs (Control Moment Gyros). Fruitful discussions were initiated during the question sessions and the informal BBQ which followed the workshop.
All speakers and attendees agree that a follow up workshop would be the most useful means to continue the interchange of ideas and work in the area of advanced space vehicle control. It was proposed that:
- A follow up workshop before or after the International Astronautical Congress in 2008 taking in place in Glasgow could be a realistic target with the workshop theme focused on Solar Sail missions and technology
- Another follow up workshop taking place in the USA or China funded by DLR, again, with a focus on Solar Sails in 2007
An important step is the selection and publishing of the best 6 papers of the workshop in the Journal of the British Interplanetary Society, which will be completed by January 2007.
Dr Vaios Lappas
3 December, 2006