Designing and analysis ACS (курсовая работа на английском языке), страница 2

    Consider now transient response of the servomechanism to a ramp input (Fig.1.4b). In the early stages of the input (instant ), and while the error signal is small, the load accelerates slowly and lags behind the input. The signal increases as the lag increases, thereby building up the acceleration. Eventually the input and loud speeds are equal (instant ), but since a substantial position error exists, the load continuous to accelerate. Then the acceleration is reduced, and the load attains a constant speed (instant ) at zero position error with no error signal, and so on. Thus, as in the case of a step input, a continuous oscillation is produced.

If there are coloumb and viscous frictions the oscillations are damping (Fig.1.4). But using only inherent friction light damping is achieved. It is necessary, therefore, to use special approaches to restrict the oscillations. 

 Actuator RD – 25FA

The actuator is intended for activity in a structure of the servomechanism as an actuator of the autopilot and mechanically connected to a control system of an airplane.

The main characteristics:

Voltage across the winding of excitation of the engine

Voltage across the winding of control of the engine

 The firing moment of the engine

Voltage across the winding of excitation of a tachogenerator

Steepness of voltage output of a tachogenerator not less

Steepness of voltage output of the induction potentiometer not less

Power of engine DG – 25B

Efficiency of the reduction gearbox

The block diagram

The given block diagrams of linear and non-linear servomechanisms we find in mathematical packet MATLAB 6.1 as follows:

1. We start MATLAB;

2. In a command line we write Demos;

3. In menu MATLAB Demos Simulink it is chosen Aerospace in which menu it is chosen Electrohydraulic Servomechanisms;

4. We receive schemes of linear and non-linear servomechanisms;

Linear servomechanism










 Definition of transients of servomechanism

Drawing of transient characteristics (of linear servomechanism) is made under following scheme



Linear                                       Nonlinear

From the received schedules it is visible, that the system is steady.

Settling time  


Research of frequency response of servomechanisms

Research of frequency response we shall conduct on linear model.

To draw frequency characteristics it is necessary to receive a transfer function of a servomechanism.

Transfer function of closed-loop system is

where  - transfer function of disconnected system


proceeding from this


The logarithmic amplitude frequent characteristic,

The logarithmic phase frequent characteristic,

The amplitude-phase frequent characteristic,

Drawing LAFC, LPFC , MPFC with the help of commands Bode, Nyquist.

From the received schedules it is visible, that the system is absolutely steady.

Design part

The principal diagram of the final cascade of the servomechanism amplifier

Fig. 2.1. The final cascade of the amplifier

Account of the final cascade of the amplifier

    It is necessary to choose transistors  for obtaining in load of voltage  and a current .

          We choose the amplifier of general application . Its basic parameters:


  1. Resistance of load


  1. Power, dissipated on transistors

3.  Maximum voltage on a collector

Taking into account values , we choose transistors  и . Their basic parameters:

These transistors meet the requirements on permissible

  1. Permissible power dissipation rating on a collector at

, transistors  can be used without heat rejections.


6.   Power supply voltage of the amplifier


  1. Currents  at :

  1. Taking into account, that at  transistors  are open we shall define a current of base

At  transistors  are open for currents:

, that is the amplifier provides a current of load


     10.   Maximum voltage  of transistors:


11.  Power, which dissipates on transistors:


Taking into account the received values, we choose transistors

      12.  Currents of bases of transistors:


      13.  Currents of dividers  and  also should exceed considerably. We receive .


14.  Resistance of resistors  it is considered, taking into account :


We receive

15.  Capacitor


Assembly drawing of the printed-circuit-board of the amplifier

Development of technological process

The analysis standard TP and selection of operations

Analyzing standard TP, we choose operations for worker TP [11].