Automatic regulation must be added owing to the unstable characteristics of the open loop secondary system.
由于二次调节的开环不稳定特性，必须为其设置自动调节系统。
2
But the learning period of opened-loop iterative learning control is long, and the unstable and high gain phenomena may be taken place during the initial stage of iterative learning control.
开环迭代学习控制学习周期长，在迭代学习的初期容易出现不稳定和高增益的现象。
3
An unstable process is transformed into a minimum-phase system through mirror-injection, then solve the robust controller using closed loop gain shaping algorithm.