# Roll Eccentricity Signal Detection and Its Engineering Application Based on SFFT-IAA
## 5 Engineering Implementation and Validation  
This study conducted engineering application research and algorithm validation of eccentricity compensation by taking an actual 1150 mm six-roller reversible rolling mill as the experimental object. The roller system parameters of the experimental rolling mill are as follows: the upper and lower backup roller diameters are 1018.8 mm and 1052 mm, respectively; the upper and lower intermediate roller diameters are 392.2 mm and 396.36 mm, respectively; the upper and lower work roller diameters are 324.25 mm and 325.72 mm, respectively. The sampling period is 10 ms, and the parameters of the SFFT-IAA algorithm are the same as those used in the simulation. Roll eccentricity detection and compensation were implemented in the rolling mill. AGC system. Considering that the construction algorithm of eccentricity signal detection and eccentricity model based on the SFFT-IAA algorithm is complex and cannot be easily implemented only by the basic automation level (L1), the thickness control system adopts a two-level computer control system combining the basic automation level (L1) and the process automation level (L2). The L2 system adopts industrial control computers to receive and store on-site data and to analyze and to calculate the roll eccentricity signal with advanced language programming. Then, the eccentricity model is constructed and sent to the L1 control system. The L1 control system uses a hardware platform based on Siemens S7-400 PLC and Siemens FM458 to receive the eccentricity model and to perform eccentricity compensation control based on the eccentricity model. The 1150 mm six-roller reversible cold rolling mill, rollers, and control system are presented in Figure 9.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Eccentricity Parameter**} & \multirow{2}{*}{**Actual Value**} & \multicolumn{2}{c}{**SFFT-IAA**} & \multicolumn{2}{c}{**FFT**} \\ \cline{3-6}  & & **SNR = 30** & **SNR = 10** & **SNR = 30** & **SNR = 10** \\ \hline frequency 1/Hz & 0.3981 & 0.3981 & 0.3968 & - & - \\ amplitude 1/mm & 0.2 & 0.1991 & 0.1912 & - & - \\ phase angle 1/rad & 0 & 0.0000 & 0.0003 & - & - \\ \hline frequency 2/Hz & 0.3915 & 0.3915  
The data used to detect the roll eccentricity signals were obtained from the rolling force and outlet thickness deviation data collected on site. The specific steps include:  
1. Conducting a zero-pressure dependence experiment in the roller gap control mode after each roller change;
2. Collecting the rolling force data when the rolling pressure is in the open-loop state;
3. Using the collected data to generate the roll eccentricity model. At this point, without the influence of the rolled piece, the rolling force can fully reflect the roller state and an accurate roll eccentricity model can be established. In the normal rolling process, due to changes in the working condition, the eccentricity model parameters will also change. Therefore, during the rolling process, the thickness fluctuation data of exporting strip steels were collected and then used for online roll eccentricity detection, and the amplitude and the initial phase angle of each harmonic in the eccentricity model established in the zero-pressure dependence state were corrected. Figure 10a shows the rolling force data collected on site at a rolling speed of 1.07036 m/s under the zero-pressure dependence condition. The pressure fluctuation data were divided by the rolling mill stiffness after removing the direct current component and trend processing to obtain the data of the roll gap fluctuation caused by roll eccentricity; the result is shown in Figure 10b. The L2 computer used the proposed SFFT-IAA to process the collected roll gap fluctuation data. First, SFFT was used to obtain the frequency distribution of the roll eccentricity signal (see Figure 11). Figure 10: Curve of practical rolling data. (**a**) Rolling force; (**b**) roll gap. Figure 9: The rolls of six-roller reversible cold rolling mill and the control system of cold rolling mill.