As sinter is a typical timevarying and nonlinear system with large delay time, it is difficult to describe the whole process using a mathematical model.
烧结是一个典型的时变、非线性、大滞后的系统，很难用一个确定的数学模型去描述整个过程。
2
Based on a typical timevarying and nonlinear system with large delay time, it is difficult to describe the whole process using a mathematical model.
基于复杂工艺过程的时变、非线性、大滞后的系统，很难用一个确定的数学模型去描述整个过程。
3
The model-free control is especially useful for real nonlinear systems whose orders and modeling are very difficult to be known and timevarying.