The influence of external disturbances on the control of the aircraft in the horizontal plane

To side winds. When the ACS, roll forming specified by law (3), for all forms of feedback servo inevitable appearance of static error by the action of crosswinds. This is because the signal yaw angle due to the longitudinal axis rotation of the aircraft in the wind direction to eliminate the slip can be balanced only lateral displacement signal. Indeed, the

.

whence

,

ie more or less cross wind speed, the greater the error. Dynamics of the process is as follows. Crosswind plane communicates with the line of the path. As more errors ACS tilts LA. Since at LA roll unfolds at a rate proportional to the rate of the signal reduces the roll. When the lateral velocity component balances wind speed, increasing the error stops.

If ACS generates a specified list according to the laws (4) - (6), then the effects of crosswinds is provided through the flight of a given path without static error. In fact:

,

as well as in the steady state , then . It is provided at the rate of rotation of the plane nosed into the wind at an angle .

The impact of continuous disturbing moment. Under the action of constant disturbing moment heel (for example, the case of asymmetric discharge cargo) in a steady process . Therefore, when Jos servo roll forming specified by law (3) - (5) appears static error.

The behavior of an aircraft with ACS is described by the following equations

;

;

.

Solving these equations, we obtain an expression for the static error

,

ie the plane will fly with aileron, maintaining a given rate, with zero bank angle, but with a lateral deviation from the specified path .

And to the action of disturbing moment roll plane on hold given path should:

Jos used for servo control law (6);

when the law of formation of heel (3) - (5) apply SOS or IOS servo.

2. Speed ​ ​ control of flight

Speed ​ ​ control of the flight is carried out in two main controls:
• changes in engine thrust;
• elevator.

Control airspeed change thrust. Control airspeed change thrust is mainly used in rectilinear motion, and in particular, the motion of the aircraft on final approach.

Automatic performing stabilization speed by changing the thrust of the engines, commonly called autothrottle (AT). Changing the traction machine carries through the lever engine control (throttle) .

Automatic traction needed for a cruise flight with simultaneous stabilization trajectory CM LA. An example of such a regime can serve as the approach mode. If traction control is a direct effect on the longitudinal forces acting on the aircraft. Control law with AT Jos can be written as

.

In the study of the dynamics of the aircraft in speed with AT need to add the equations of motion of the aircraft equations describing the control laws of the AT and ACS. We assume that the channel pitch deviation ACS stabilizer keeps a straight trajectory. Then the system of equations describing the movement of aircraft on the speed with AT is thus reduced to the following:

;

;

.

The first equation is the projection of forces on the longitudinal axis, the second characterizes the change in traction at a deviation ORE. The engine is described by inertial element. The third equation determines the deviation ORE AT. The inertia of the process can be neglected. For the analysis of the dynamic properties of the system " plane - AT" in the management of the flight speed necessary to obtain the transfer function .

Block diagram corresponding to equation is shown in Fig.

Transfer control circuit diagram of the form

The analysis of the transfer function leads to the following conclusions:
- dynamic properties of the control loop " aircraft - AT" describes the element of the second order;
- dynamic properties of the considered control loop determined by the properties aircraft engine performance (gain and time constant) and the parameters of the AT;
- increase in factor contributes to the natural frequency of the control loop, and - damping factor. Changing parameters AT (coefficients and ) can affect the quality of the transition process;

there is a static error in completing the speed setpoint:

.

The presence of antibodies in the control law of the integral of the velocity signal will provide astatic stabilization speed.

Speed ​ ​ control with the help of the elevator. Airspeed control deflection of the elevator is used if not imposed stringent requirements for the movement of aircraft on the desired path.

The elevator in the management rate deviates by law

.

If you change the speed of flight elevator deflected to increase the angle of attack. Changing the angle of attack will change the lift and drag forces. As a result, the trajectory will be bent, and flight speed will vary.

If we assume that the aircraft at a deviation of the elevator goes instantly to a given angle of attack, the closed-loop transfer function is equal to

,

where the coefficients of the denominator are functions of aerodynamic design aircraft, and transmission coefficients of the control law. Change gear ratios and you can adjust the values ​ ​ of the coefficients , , and and ensure stability of the closed loop. However, under the law (6.) Is not always possible to obtain the desired transition.

From the analysis of the transfer function we can also conclude that the management of the speed using the elevator there is a static error that is fixed in the control law to introduce an additional integral term.

Stabilization of flight speed in principle possible to provide exposure to the drag with brake flaps. However, this method of stabilization rate is not favorable, as in the original flight mode for speed control in one and the other side of the brake pads should be rejected by some amount, resulting in increased drag aircraft.