Output feedback force control for a parallel turning operation

Parallel machine tools (i.e., machine tools capable of cutting a part with multiple tools simultaneously but independently) are being utilized more and more to increase operation productivity, decrease setups, and reduce floor space. Process control is the utilization of real-time process sensor information to automatically adjust process parameters (e.g., feed, spindle speed) to increase operation productivity and quality. To date, however, these two technologies have not been combined. This paper describes the design of an output feedback controller for a parallel turning operation that accounts for the inherent nonlinearities in the force process. An analysis of the process equilibriums explains the system stability behavior for different design specifications and the reverse trajectory method is used to numerically determine the exact stability boundary. Effects of saturation on stability are also analyzed and from this sufficient conditions for global stability are obtained.