Classical control theory is used to synthesize feedback controllers for the simultaneous control of temperature and humidity in a confined space. The decoupling or diagonalization approach is employed to reduce the multivariable control system to a pair of noninteracting control loops and the Ziegler-Nichols settings are then determined for each loop. The temperature-humidity control system is then compared with conventional temperature-only control systems.
NOMENCLATURE coefficient matrix of state variable vector x coefficient matrix of control variable vector u output matrix coefficient matrix of disturbance vector v matrix of controller transfer functions matrix of measurement transfer functions matrix of process transfer functions matrix of disturbance transfer functions matrix of final control element transfer functions open loop transfer function of first loop open loop transfer function of second loop closed loop transfer function offirst loop closed loop transfer function of second loop element of transfer matrix G c element of transfer matrix G" element of transfer matrix G p element of transfer matrix G ° element of transfer matrix G u humidity of outdoor air, Ibm HzO/Ib= dry air humidity of inlet recycle air, lb= H20/lbm dry air humidity of room air, Ibm H20/Ib,, dry air critical gain magnitude parameter of final control element magnitude parameter of final control element output matrix molecular weight of air, 28.8 molecular weight of water, 18