The error occurs because the Plant Transfer Function block can ony accept 1 INPUT, instead 3 SEPARATE Inputs.
The PID controller produces only 1 Output, despite it has 3 Components, namely Proportional, Derivative, and Integral actions.
Important node: Fixing this issue should allow you to run the simulation without error message.
You have designed 3 Fuzzy Systems for the Nonlinear Gain Schedules of Kp, Kd, and Ki. Unknowingly, I suspect that you created outputs {
, 
, α} for each of the Fuzzy System.
, , α} for each of the Fuzzy System.
So, please ensure that each Fuzzy System has only one corresponding Output as shown in the figure below, and the problem should be fixed. Whether the results are satisfactory or not, this is a different unrelated issue that requires some tuning of the fuzzy membership functions and the rules. In fact, you shouldn't directly follow the proposed values {10000}, {500}, and {1} in the paper if your Plant model is different. I understand that you may want to get it run successfully first, and then tune them later.
