Abstract—This paper addresses the problem of coordinating multiple spacecraft to fly in tightly controlled formations. The main contribution of the paper is to introduce a coordination architecture that subsumes leader-following, behavioral, and virtual-structure approaches to the multiagent coordination problem. The architecture is illustrated through a detailed application of the ideas to the problem of synthesizing a multiple spacecraft interferometer in deep space. Index Terms—Control architecture, coordinated control, interferometry, spacecraft formation flying. I.

this paper. Following a decentralized coordination architecture via the virtual structure approach, decentralized formation control strategies are introduced, which are appropriate when a large number of spacecraft are involved and/or stringent inter-spacecraft communication limitations are exerted. The e#ectiveness of the proposed control strategies is demonstrated through simulation results

This paper presents the coupled dynamics approach to executing Elementary Formation Maneuvers (EFM) for Hilare-type mobile robots. The concept of an EFM is presented. It is then shown that each of these EFMs posses a common mathematical structure and thus may be executed by the same type of robot control. We present three different EFM controls in this paper. The first puts feedback on the relative motion and the global motion of each robot. The second control adds inter-robot damping. And the third control uses saturated inputs on the relative motion and the global motion of each robot. We present simulation and hardware results for each of these controls. I. Introduction Cooperative robots can often be used to perform tasks that are too difficult for a single robot to perform alone. For example a group of robots can be used for moving large awkward objects [1], [2] or for moving a large number of objects [3]. In addition groups of robots can be used for terrain model acquisition [3]...

Formation Flying is quickly revolutionizing the way the space community conducts autonomous science missions around the Earth and in space. This technological revolution will provide new, innovative ways for this community to gather scientific information, share this information between space vehicles and the ground, and expedite the Human exploration of space. Once fully matured, this technology will result in swarms of space vehicles flying as a virtual platform and gathering significantly more and better science data than is possible today. Formation flying will be enabled through the development and deployment of spaceborne differential Global Positioning System (GPS) technology and through innovative spacecraft autonomy techniques. This paper provides an overview of the current status of NASA/DoD/Industry/University partnership to bring Formation Flying technology to the forefront as quickly as possible, the hurdles that need to be overcome to achieve the formation flying vision, and the team's approach to transfer this technology to space. It will also describe some of the formation flying testbeds, such as Orion, that are being developed to demonstrate and validate these innovative GPS sensing and formation control technologies.

Formation control for multiple vehicles has become an active research area in recent years. Generally there are three approaches to this problem, namely leaderfollowing, behavioral, and virtual structure approaches. In this paper, formation control ideas for multiple spacecraft using virtual structure approach are presented. If there is no formation feedback from spacecraft to the virtual structure, the spacecraft will get out of formation when the virtual structure moves too fast for the spacecraft to track or the total system must sacrifice convergence speed in order to keep the spacecraft in formation. The spacecraft may also get out of formation when the system is affected by internal or external disturbances. To overcome these drawbacks, a novel way of introducing formation feedback from spacecraft to the virtual structure is illustrated in detail. An application of these ideas to multiple spacecraft interferometers in deep space is given.

This paper considers the problem of rotating a formation of satellites from one orientation to another, using an optimal amount of fuel. The formation is constrained to have the same shape at the beginning and end of a maneuver. However, the shape is unconstrained throughout the maneuver. This implies that to optimize fuel, each spacecraft travels in a straight line, from its beginning to end position. A cost function, motivated by the entropy function from information theory, is used to trade off fuel minimization verses equalizing the fuel across the constellation to avoid fuel starvation. 1 Introduction Multiple spacecraft formation flying is emerging as an enabling technology for a number of planned NASA missions. An example is the proposed separated spacecraft interferometry missions. Since the life expectancy of a satellite is limited by its fuel, fuel optimization is critically important to formation control algorithms. For various application of spacecraft formation flying, i...

This paper considers the problem of rotating a constellation of spacecraft using on/off thrusters such that the relative distance between the spacecraft is maintained to within a specified tolerance. The basic idea is to resolve all of the constraints into a sphere around the desired trajectory of each spacecraft. As the constellation rotates, the sphere sweeps out a tube that constrains the motion of the spacecraft. The control is activated when the spacecraft encounters the constraint sphere, the direction and magnitude of the thrust are calculated to maximize the travel of the spacecraft before the next required thrust, thus minimizing thrust. 1 Introduction Multiple spacecraft formation flying is emerging as an enabling technology for a number of planned NASA missions. Of particular interest to this paper is separated spacecraft interferometry. Some interferometry missions impose the constraint that the constellation be rotated, or retargeted, while maintaining the relative distan...

of a dissertation submitted by Jonathan R. T. Lawton This dissertation has been read by each member of the following graduate committee and by majority vote has been found to be satisfactory.

This paper considers the problem of rotating a formation of spacecraft from one orientation to another, using an optimal amount of fuel. The formation is constrained to have the same shape at the beginning and end of a maneuver. However, the shape is unconstrained throughout the maneuver. This implies that to optimize fuel, each spacecraft travels in a straight line, from its beginning to end position. A cost function, motivated by the entropy function from information theory, is used to trade off fuel minimization verses equalizing the fuel across the constellation to avoid fuel starvation. 1 Introduction Multiple spacecraft formation flying is emerging as an enabling technology for a number of planned NASA missions. An example is the proposed separated spacecraft interferometry missions. Since the life expectancy of a spacecraft is limited by its fuel, fuel optimization is critically important to formation control algorithms. For various application of spacecraft formation flying, i...

Separated spacecraft interferometry missions will require spacecraft to move in a coordinated fashion to ensure minimal and balanced consumption of fuel. This paper develops strategies for determining interferometry mission plans that result in significant fuel savings over standard approaches. Simulation results demonstrate that valuable reductions in fuel consumption can be realized by combining the retargeting and imaging maneuvers required to image multiple stellar sources. Fuel-optimal imaging strategies have been developed for twospacecraft interferometry missions similar to the proposed Space Technology 3 mission using chained local optimization methods. Based on these strategies, sampling pattern guidelines for space-borne interferometry missions have been developed. 1 Introduction Space-based optical interferometry has been identified by NASA as one of the key technologies in furthering the scientific exploration of the universe in the Engineer, Flight Dynamics De...