A singularity free parallel robotic mechanism for aiming antennas and cameras
Several different mechanisms have been used to aim narrow beam communications links between earth stations and orbiting satellites. Only two axes are required to aim the beam but for the three conventional serially connected mechanisms currently used, a singularity about the first axis prevents tracking through a key hole region centered on the first axis and the communication link can fail. This key hole or mechanical singularity is caused by dynamic limitations which can never be overcome with the standard two axis serial mechanism. To keep the aim, it is common to add a third axis, or even add a two axis gimbaled base for marine applications. These serial connections reduce the stiffness of the aiming mechanism and increase the cost. A solution to this problem is to use a parallel robot. Previous work on two axis parallel robots showed that while such a mechanism could provide hemispherical coverage, a singularity in the drive linkages prevented full control of the coverage. A different drive system has been developed to avoid all singularities and is presented here for the first time. The results of dynamic simulations of the system in marine applications are presented to show reduced drive system loadings due to motion of the mounting base. This robotic mechanism is also capable of providing singularity free hemispherical aiming capability for aircraft mounted camera systems.
KeywordsRevolute Joint Parallel Robot Base Acceleration Marine Application Robotic Mechanism
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