Multivariable controller structure in a variable cam timing engine with electronic throttle and torque feedback

By adding an electronic throttle and a torque sensor to an engine equipped with variable cam timing (VCT), it is potentially possible to vary cam phasing to improve emissions and fuel economy while preserving the torque response of a conventional non-VCT engine. To do so effectively, however, requires the use of multivariable control. A controller consisting of decentralized individual control loops will not yield satisfactory performance because such a controller cannot compensate for system interactions. Yet, a fully multivariable controller may not prove necessary in order to achieve the desired performance. In this paper, we design linear multivariable controllers at a number of operating points and simplify the resulting controllers by eliminating cross-coupling terms that do not affect the closed loop response. Doing so provides insight useful in tuning controller parameters