Tham khảo tài liệu 'frontiers in adaptive control part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 266 Frontiers in Adaptive Control T c0 c1 C2 Ằ R IO_PID 10 1 1 FO_PID 10 IO_PID 5 1 1 FO_PID 5 Table 3. Controller parameters for the mechanically ventilated respiratory system Frequency rad sec Figure 11. Left frequency domain approximation and Right unit step responses for T 5 reference blue IO_PID green and FO_PID red . Circles denote settling times 4. Discussion Tuning aspects Obviously the first and crucial step in DIRAC is the choice of the reference model R s . This can be done if some knowledge on the process is available. Some of the rule-of-thumb guidelines can be summarized in the following list if the controller contains integral action it ensures zero steady state error which must be reflected in the closed loop gain the latter should be 1 . R 1 1 if both process and controller contain an integrator it is the case of type 2 control loop double integrator this means that the closed loop can track a ramp-setpoint without error and this should be reflected by the choice of the reference model see for example 18 if the process contains a dead-time the closed loop will also be affected by it therefore in the reference model the presence of the dead-time is necessary and an approximate value suffices to obtain good results if the process is non-minimum phase the closed loop will also have this property therefore the reference model should also be non-minimum phase. In the previous sections it has been stated that the choice of the time constant in the reference model affects the speed of the closed loop. When defining the time constant of the reference model the actual time constant of the process has to be taken into account. In other words the desired closed loop speed should be in the same order of magnitude as the open loop settling time of the process. If this condition is not fulfilled the reference Model-free Adaptive Control in Frequency Domain .