Page - 7 - in Adaptive and Intelligent Temperature Control of Microwave Heating Systems with Multiple Sources

1.2. Overviewof theStateof theArt microwave source in order to make the measured temperature reach thepredefinedtarget temperature. This modeling-and-control approach is effective for microwave heat- ingsystemswithonefeedingsource,andmostoffollowingworkuses the same kind of strategy. For instance, in [RCVI99] a proportional- integral-derivative (PID) controller was developed to control temper- atures in microwave heating. In [SBA00] the autoregressive-moving- average model with exogeneous inputs (ARMAX) [BJR13] method was utilized to build the system model. Another model-based feed- backcontrollerwasdesignedandarecursiveKalmanfilter (RKF)was used to estimate the parameter of the ARMAX model, which further enhanced the control performance. Similar control schemes can also be found in [KRS08] and [HS07]. Despite the model based feedback controller achieved good control performance regarding to the SISO heating scenario, the entire temperature distribution of the heated load was not considered in the control model, and hence, not con- trolled. In order to truly improve the temperature homogeneity, microwave heating systems equipped with multiple distributed feeding sources were studied and developed, such as the system used in our experi- mentsandtheonementionedin[LLHG14]. Ontheonehand,systems withmultipledistributedmicrowaveheatingsourceshaveagreatpo- tential toachieveamoreuniformtemperaturedistribution. Butonthe other hand, they are much more complicated than systems with only onefeedingsource. Alotof itsproperties,suchastheEMdistribution, excitementofdifferentmodes,effectsofdifferentpositionsofsources, especially the temperature control strategy, still remain unknown. Al- though in [LLG14] and [LLHG14], a distributed temperature control system was claimed to be implemented for controlling power of in- dividual sources, there is no detailed introduction about this system. Corresponding modeling and controlling methods are still not clear. Totheauthor’sknowledge,upuntilnowthereisnosophisticatedthe- ory or model published to deal with the controller design of systems withmultipledistributedmicrowaveheatingsystems. 7