Discrete approximation of continuous systems with timers based on partition of threshold switching faces

A method of integrating partition of threshold switching surfaces (PTSS) and segmenting approximation of flow pipe (SAFP) based on variant time interval is used to solve the trouble when there exists timers in continuous blocks and one can not use PTSS. The notion of interim states is also put forward. Enlarging the analysis time domain when approximating interim states by SAFP, one can get the timer´s reasonable range, which expands the application scope of the above method. Finally the verification method is elucidated by an example of chemical process control