ON NONLINEARITY CONTROL OF CNC FEED DRIVES

A Unified Reconfigurable Open Control Architecture (UROCA) ai ms at unifying the reconfiguration aspects and managing the interaction amongst the different operating levels of individual machining control systems that are Iikely to perform in reconfigurable manufacturing systems. The hierarchical control structure of UROCA demands the usage of a supervisory control scheme in order to manage operations of supervisory and servo controllers altogether into a reconfigurable control process. The main function of the supervisory unit is to serve as a switchinglreconfiguring logic amongst different available controllers, according to need, in order to maintain motion output within the permitted Iimits. Due to backlash, efficiency of machine tools will be undesirably turned down causing higher vibrations, lower contouring accuracy, and may draw the whole system into instability region. A Switching control scheme designated to manage the control process where two different controllers with two different control functionalities, acting differently in two vital zones - one of them where the backlash lies, and the other when moving past the backlash - is the main topic of this paper. The proposed switching schemes emphasize a reconfiguration aspect on the control process level for machine tools as perceived, investigated and resolved by the physical and controllayers located at the deliberative part of the UROCA architecture.