John L. Junkins

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In this paper a novel approach is developed for relative state estimation of spacecraft flying in formation. The approach uses information from an optical sensor to provide multiple line-of-sight vectors from one spacecraft to another. The line-of-sight measurements are coupled with gyro measurements and dynamical models in an extended Kalman filter to(More)
A new family of orientation parameters derived from the Euler parameters is presented. They are found by a general stereographic projection of the Euler parameter constraint surface, a four-dimensional unit sphere, onto a three-dimensional hyperplane. The resulting set of three stereographic parameters have a low degree polynomial non-linearity in the(More)
The stationary Fokker-Planck Equation (FPE) is solved for nonlinear dynamic systems using a local numerical technique based on the meshless Partition of Unity Finite Element Method (PUFEM). The method is applied to the FPE for two-dimensional dynamical systems, and argued to be an excellent candidate for higher dimensional systems and the transient problem.(More)
In this paper, an algorithm is proposed to avoid singularity associated with the most famous minimum element attitude parametrization, Euler angle set. The proposed algorithm makes use of the method of sequential rotation to avoid singularity associated with Euler angle set. Further, a switching algorithm is also proposed to switch between different Euler(More)
Abstract In this paper an optimal solution to the problem of determining both vehicle attitude and position using line-of-sight measurements is presented. The new algorithm is derived from a generalized predictive filter for nonlinear systems. This uses a one time-step ahead approach to propagate a simple kinematics model for attitude and position(More)
Autonomous in-flight aerial refueling is an important capability for the future deployment of unmanned aerial vehicles, because they will likely be ferried in flight to overseas theaters of operation instead of being shipped unassembled in containers. A reliable sensor, capable of providing accurate relative position measurements of sufficient bandwidth, is(More)
A novel approach for vision sensing and vision-based proximity navigation of spacecraft is presented. We have recently invented a new sensor which utilizes area Position Sensing Diode (PSD) photodetectors in the focal plane of an omni-directional camera. These analog detectors inherently centroid incident light, from which a line of sight vector can be(More)
In this paper, the stationary Fokker-Planck equation (FPE) is solved for nonlinear dynamical systems using a local numerical technique based on the meshless partition of unity finite element method (PUFEM). The method is applied to stationary FPE for two, three and four-dimensional systems and is argued to be an excellent candidate for higher dimensional(More)