Abstract: A sheet transportation device for use in an image forming apparatus is provided which has self-diagnosis and self-repair functions. The sheet transportation device has a sheet transportation system including a plurality of units (8). A control sequence for a sheet transportation operation is applied from a system body (10) to the respective units (8). The units (8) each execute the control sequence to perform the sheet transportation operation. The units (8) are each constructed so as to perform an autonomous operation. This construction allows the respective units to autonomously perform self-diagnosis and repair operations. The fault diagnosis and repair operations are performed in parallel to the sheet transportation control. Therefore, the sheet transportation device can flexibly adapt itself to an external influence such as a change in the use environment and a malfunction due to a time-related change such as the aging of components thereof.

Abstract: A simulation system is provided which is capable of simulating the behavior of a sheet transported by a transportation system. In response to application of a control sequence formulated for the sheet transportation system, a simulation is performed to check how the sheet is to be transported in the sheet transportation system on the basis of the applied control sequence. Necessary data are extracted from hardware systems constituting the real sheet transportation system. On the basis of the extracted data, a virtual sheet transportation system is constructed in a computer, and the sheet is represented by information indicative of the locations of opposite ends of the sheet and the distance therebetween. The sheet thus represented is moved by a predetermined unit distance in the virtual sheet transportation system on the basis of the control sequence, and data is computed for every movement of the sheet.