This paper presents a study on the dynamics of parallel kinematic mechanisms (PKMs), and the determination of which dynamics terms are candidates for identi cation. Using D'Alembert's method, the dynamics equations of motion are derived with inclusion of the strut masses. These equations are used to solve for the required actuator forces that are grouped according to inertial and gravitational components. Comparative observations are made using Euclidean norms and sample trajectory-based characterizations. Detailed results are presented for the University of Florida Special 6-6 PKM and two geometric variants. Observations of the Hexel PKM machine tool and Ford PKM vehicle simulator's dynamics are also presented to further demonstrate shifts in the dynamics effects. Experimental validation substantiates the simulationbased results and highlights the measurement dif culties as well as delineating a need for an iterative methodology for full dynamic system identi cation implementation.
This paper addresses a new concept of autonomous guidance for close proximity operations in space. A potential function is developed with the intent that a minimum occurs at a desired relative position. A control law is then used to account for the dynamic effects and ensure the path generated is obstacle free. CW maneuvers are used to traverse solutions provided from the guidance algorithm. Trajectories are shown for a variety of situations in which a completely autonomous spacecraft can rendezvous with a cooperative satellite in an unspecified amount of time. A comparison is made between the new algorithm and traditional APFG methods by examining the total impulse thrusts and time of flight. It is shown that the new algorithm is more fuel efficient and has a shorter time of flight than traditional APFG methods.
One of the primary concerns associated with the design of small satellites is achieving power capacities sufficient to support payload and mission operations while simultaneously retaining communications capabilities. Furthermore, small satellites must be able to easily transform from their tightly stowed configurations to their fully operational mode. To address these concerns, this paper presents the theoretical modeling and analysis of a class of foldable mechanisms, based on the Hoberman mechanism's kinematic theory, and their parametric coupling with the system parameters of both an antenna array and a solar array. The resulting models provide viable solar array and antenna array designs to generate power and communications capabilities on small satellites. 12
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