Abstract
A universal electronic testing machine has been experimentally produced and the characteristic of its control system has been analyzed with respect to the effect of nonlinear properties of transfer elements on the stability of the system.
When the input signal is sinusoidal, there is no output signal produced if the input amplitude falls in the backlash zone, but when the input signal contains some random noise in it, the stable regions are changed.
(1) Whenκ1; is assumed the equivalent gain of the neutral zone for the sinusoidal input, a formula κ1; =(TA; +TM;)[-(T2A; +T2M; )+√<D>]/k[(TA; +TM; )2-radic;<D>]TA; TM; is obtained where D=(T2A; -T2M; ) 2+4(TA; TM; )2(TA; +TM; )K
The proportional gain K of the linear part is included in the denominator and numerator of the above formula. As a result, the increase of K value results in the increase of κ1; . So that, the increase of K extends the stable region for both sinusoidal input and random input. In other words, the increase of K has the same effect on the stability of the system as the increase of (Az; /a).
(2) Decreasing of variance σn; 2 of the random noise extends the stable region.
(3) Above conclusions lead us to the next method for increasing the stability of the system.
When the value of Az; /a is large and the proportional gain K is fixed, it is recommended to place a saturation element in front of the neutral zone, and provide a filter to reduce the value of σz; /a.
