Specifications

5 Designing and Testing Controllers in Simulink
5-26
When the masses are disconnected, as at the start, MPC2 applies excessive force and
then over-compensates, resulting in oscillatory behavior. Once the masses join, the
move more smoothly, as would be expected.
The last transition causes especially severe oscillations. The masses collide frequently
and M1 never reaches the desired position.
If MPC1 is in charge exclusively, the masses move sluggishly and fail to settle at the
desired position before the next transition occurs. For more information, see the
Scheduling Controllers for a Plant with Multiple Operating Points.
In this application, at least, two controllers are, indeed, better than one.