Certain new approaches for designing efficient controllers for linear systems, in particular, for integrating processes, are proposed in this book. The parameters of the proposed proportional-integral-derivative (PID) controllers and its variants are optimized by minimizing the integral square error (ISE) using the so called bacterial foraging algorithm (BFA). Although ISE is a standard minimization criterion as well as BFA has certain advantages such as better solution quality and good convergence, both of them suffer from some drawbacks. To obtain the robust closed loop performance, the ISE criterion is initially modified by appending time parameters to the said criterion. Similarly, to ensure the convergence of BFA, an adaptive strategy for the run length vector along with two modifications in the standard BFA are also proposed. Next, the parameters of the PID and its variants are estimated using the proposed `slope of the Nyquist curves'' technique. The approach of the said slope of the Nyquist curves method is also extended to design controllers for the modified Smith predictors.