128 CHAPTER 4. DEMONSTRATION EXAMPLES
δv Perturbations along the velocity vector.
αAngle of attack. I.e. angle between the velocity vector and the aircraft’s longitudinal
axis.
qRate-of-changeof aircraftattitude angle.
θAircraft attitude angle.
Control can be exerted via the elevon and canard, denoted by δeand δcrespectively.
The angle of attack (α) and attitude angle (θ) are available as direct measurements.
A weighted output disturbance rejection problem will be considered. This problem also
encompasses other maneuvering objectives. The closed-loop perturbation modelof the
vehicle is illustrated in Figure 4.1.
Figure 4.1: Himat open-loop perturbation model
Note that Wp,Wdel, Himat and Kare each two-input, two-output systems. Similarly,
the inputs dist and pertin are two element vector signals. The desired result is the
four-input, four-output system, denoted by clp, and shown in Figure 4.2. This is used in
the design example given below.
4.1.2 State-space Model of Himat
The state space description of the Himat plane is given below. The states of the plant
model are: forward speed (v), angle-of-attack (α), pitch rate (q) and pitch angle (θ).