Development of a control system for remotely controlled non-rigid airship
Devendra Khitoliya,
M.Tech,
05,
69 pp.
Department of
Aerospace Engineering
Indian Institute of Technology Bombay,
Powai, Mumbai 400 076.
Supervisor(s):
R. K. Pant
An airship is a lighter than air vehicle that derives
its lift mainly from buoyancy. An airship is considered to be the most
capable vehicle for long endurance flight at low speeds, for
applications such as advertisement, scientific exploration, and aerial
surveillance. The most common type of airship currently in use is the
non-rigid airship, also called as blimp. An airship is a highly
non-linear and complex system; hence modeling its dynamics poses
several challenges, compared to a heavier-than-air aircraft. Due to its
buoyant nature, very large volume and considerable change in the center
of gravity location during operation, added or virtual mass terms
assume importance in its dynamic modeling and inertia properties. This
study covers literature survey related to the modeling of airship
dynamics, stability, control and its simulation. Some issues related to
the operation of non-rigid airships are highlighted. Non-linear
equations of motion are derived from the standard equations of motion
of a rigid body with 6 degrees of freedom. The dynamic modeling
includes the effects of virtual mass and inertia. A procedure for
estimation of various airship related parameters required for the
simulation of its dynamics is outlined. A linear PID controller is
designed for the decoupled longitudinal and lateral-directional motion
of an airship. The behavior of an airship can be determined by the
simulation of this non-linear model for different cases of inputs.
Finally, the linear controller is applied to non-linear dynamic model
for a case of tracking of forward velocity at various speeds, at a
given altitude. The linear PID controller seems to work well with the
non-linear model, as it gives the limiting overshoot. The time response
of the PID controller for forward velocity also matched quite well with
the published results using an autopilot system. ��