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A Sampling of Content in Line of Sight Stabilization Primer Two-Axis Tracker Configuration

Above is a figure found in Chapter 2: LOS Control Architecture and Design which describes the basic line of sight control architectures, performance requirements, error budgets, and design methodology


Design Methodology


Chapter 2.0 LOS Control Architecture and Design

Chapter Synopsis: Basic line of sight control architectures, performance requirements,
error budgets, and design methodology

Before delving into a LOS servo control loop design, the pointing control
architecture must be chosen based upon specified performance criteria. A design
methodology for achieving the performance objective is then established which provides
the flow-down of pointing performance requirements to control loop and component
specifications. A typical 2-axis elevation over azimuth gimbal configuration, as used to
direct the pointing vector along the LOS, is illustrated in Figure 2.1. It is representative
of the LOS control mechanisms addressed. The track sensor (i.e. camera, ladar, radar,
detector array, etc.) is the mass to be stabilized and is mounted on the inner axis of the
gimbal. With mirror systems, the sensor could also be located below/above the gimbal,
coupled to the LOS via a stabilized steering mirror (SSM). In control system
terminology, the sensor or stabilized mass is the plant for the gimbal inner axis. Ideally it
is simply a torque integrator scaled by inertia producing an angular rate response.
Design challenges arise from the gimbal geometry and the wide variety of disturbances
applied. As discussed, pointing control is normally implemented via two servo loops, the
outer track or pointing control loop and an inner rate or stabilization control loop. The
track processor contains the signal processing and servo compensation algorithms for
the outer loop. The symbol, G S , represents all the transfer functions associated with the
inner stabilization loop compensation. The basic architecture shown in Figure 2.1 is
assumed throughout this book, with the primary focus being the inner stabilization loop.
The track sensor detects the target location, determining a track error used by the track
processor to generate rate commands directing the gimbal aim-point toward the LOS.
The track loop response must have sufficient bandwidth to track the LOS kinematics.