Transport system, image forming system, and control device

An image forming system, comprising:

• an image forming device provided above a transport path of a sheet and is configured to discharge ink droplets to form an image on the sheet;
• a transport mechanism including a first roller and a second roller configured to transport the sheet and arranged in the transport path across a section which is defined within the transport path and above which the image forming device is provided;
• a first driving device configured to rotate the first roller;
• a second driving device configured to rotate the second roller;
• a first measuring device configured to measure a rotation speed Z1 of the first roller;
• a second measuring device configured to measure a rotation speed Z2 of the second roller;
• and
• a controller configured to control an operation of transporting the sheet with rotations of the first roller and the second roller by controlling the first driving device and the second driving device,
• the controller being configured to perform:
• estimating a reaction force R1 acting on the first roller in a case that the first roller is rotated by the first driving device;
• estimating a reaction force R2 acting on the second roller in a case that the second roller is rotated by the second driving device;
• calculating a control input U1 in accordance with a deviation between a target speed and a speed of the sheet (Z1+Z2)/2, based on the rotation speed Z1 measured by the first measuring device and the rotation speed Z2 measured by the second measuring device;
• calculating a control input U2 in accordance with a deviation between a target tension and an estimated tension of the sheet (R1−R2)/2, based on the reaction force R1 and the reaction force R2;
• inputting, to the first driving device, a control signal in accordance with a sum (U1+U2) of the control input U1 and the control input U2;
• inputting, to the second driving device, a control signal in accordance with a difference (U1−U2) between the control input U1 and the control input U2;
• estimating a non-tensional component RE1 which is a component included in the estimated reaction force R1 and unrelated to tension of the sheet, based on the reaction force R1 estimated during a first period of time in which the sheet is transported only by the first roller from among the first roller and the second roller, or a non-tensional component RE2 which is a component included in the estimated reaction force R2 and unrelated to tension of the sheet, based on the reaction force R2 estimated during a second period of time in which the sheet is transported only by the second roller from among the first roller and the second roller;
• and
• correcting the control input U2 so as to prevent a control error caused by the non-tensional component RE1 and the non-tensional component RE2 included in the estimated tension of the sheet (R1−R2)/2, during a third period of time in which the sheet is transported by both of the first roller and the second roller, based on the non-tensional component RE1 or the non-tensional component RE2.

A controller configured to control an operation of transporting a sheet by controlling a first driving device configured to rotate a first roller and a second driving device configured to rotate a second roller, in a transport mechanism configured to achieve the operation of transporting the sheet with rotations of the first roller and the second roller which are arranged apart from each other along a transport path of the sheet, the controller configured to perform:

• estimating a reaction force R1 acting on the first roller in a case that the first roller is rotated by the first driving device;
• estimating a reaction force R2 acting on the second roller in a case that the second roller is rotated by the second driving device;
• calculating, based on a state quantity Z1 concerning a rotary motion of the first roller and a state quantity Z2 concerning a rotary motion of the second roller which are measured by a measuring device, a control input U1 in accordance with a deviation between a target state quantity and a state quantity of the sheet (Z1+Z2)/2;
• calculating a control input U2 in accordance with a deviation between a target tension and an estimated tension of the sheet (R1−R2)/2, based on the reaction force R1 and the reaction force R2;
• inputting, to the first driving device, a control signal in accordance with a sum (U1+U2) of the control input U1 and the control input U2;
• inputting, to the second driving device, a control signal in accordance with a difference (U1−U2) between the control input U1 and the control input U2;
• estimating a non-tensional component RE1 which is a component included in the estimated reaction force R1 and unrelated to tension of the sheet, based on the reaction force R1 estimated during a first period of time in which the sheet is transported only by the first roller from among the first roller and the second roller, or a non-tensional component RE2 which is a component included in the estimated reaction force R2 and unrelated to tension of the sheet, based on the reaction force R2 estimated during a second period of time in which the sheet is transported only by the second roller from among the first roller and the second roller;
• and
• correcting the control input U2 to prevent a control error caused by the non-tensional component RE1 and the non-tensional component RE2 included in the estimated tension of the sheet (R1−R2)/2, during a third period of time in which the sheet is transported by both of the first roller and the second roller, based on the non-tensional component RE1 or the non-tensional component RE2.