ON THE DESIGN, IMPLEMENTATION AND FLIGHT
TESTING OF INTEGRATED GUIDANCE AND CONTROL SYSTEMS FOR UNMANNED AIR
VEHICLES
ISAAC KAMINER
DEPARTMENT OF AERONAUTICS AND ASTRONAUTICS
NAVAL POSTGRADUATE SCHOOL
In a great number of envisioned mission scenarios Unmanned Air Vehicles
(UAVs) will be required to follow inertial reference trajectories
accurately in 3-D space. To achieve this goal, the following systems
must be designed and implemented on-board UAV's: i) navigation, to
provide estimates of linear and angular positions and velocities of the
vehicle, ii) guidance, to process navigation/inertial reference
trajectory data and output set-points for the vehicle's (body) velocity
and attitude, and iii) control, to generate the actuator signals that
are required to drive the actual velocity and attitude of the vehicle to
the values commanded by the guidance scheme.
The advent of GPS (Global Positioning System) has afforded UAV systems
engineers a powerful new means of obtaining accurate navigation data
that is required for precise tracking of given inertial trajectories.
However, traditional guidance and control schemes used to steer the
vehicle along such trajectories may prove inadequate in the case where
frequent heading changes are required or in the presence of shifting
wind. Traditionally, such systems are designed separately, using well
established design methods for control and simple strategies such as
line of sight (LOS) for guidance. During the design phase, the control
system is usually designed with a sufficiently large bandwidth to track
the commands that are expected from the guidance system. However, since
the two systems are effectively coupled, stability and adequate
performance of the combined system about nominal trajectories are not
guaranteed. In practice, this problem can be resolved by judicious
choice of guidance law parameters (such as so-called visibility distance
in LOS strategy), based on extensive computer simulations. Even when
stability is obtained, however, the resulting strategy leads to finite
trajectory tracking errors, the magnitude of which depends on the type
of trajectory to be tracked (radius of curvature, vehicle's desired
speed, etc).
In this talk, I will discuss a new methodology for the design of
guidance and control systems for UAVs, whereby the two systems are
designed simultaneously. This methodology has two main advantages over
traditional ones: i) the resulting trajectory tracking system achieves
zero steady state tracking error for a class of so-called trimming
trajectories, and ii) the design methodology explicitly addresses the
problem of stability and performance of the combined guidance and
control systems. The talk will cover the theoretical aspects of the
methodology. This will be followed by a discussion of the application of
the methodology to the design, implementation and flight testing of an
integrated guidance and control system for a UAV Frog operated by the
UAV Lab at the Naval Postgraduate School.