TABLE OF CONTENTS The effect of structural non-linearity on aeroservoelastic calculations has also been considered. Backlash (free-play) in the torsional spring of the control surface motion was considered.
Figure 14 plots the variation of the hinge moment against the flap deflection angle. The solid line represents the linear variation that has been used so far, and the dashed line shows the typical non-linear characteristics for backlash. There is a range of rotational amplitude where the restoring hinge moment is zero, outside this range a linear relationship between the restoring hinge moment and flap deflection angle exists.
Free-play of the hinge axis modifies the aeroelastic and aeroservoelastic equation only for the ? (flap) degree of freedom. Outside the free-play region the equation of motion for the flap degree of freedom is given by
| (24) |  |
where the positive sign is used when ? > ? fp and negative sign is used when ? < ? ? fp to evaluate free-play hinge moment (FPHM). The same time-marching scheme can be used again to integrate equation (24), as only change lies in the representation of the right hand side force. It is now given by f = f a + f c + f fp where f fp is the free play hinge moment and is given by f fp = {0, 0, FPHM} T.
As before the energy identity given by equation...
