Influence of sensor and communication setup on electric cam phaser control quality

Abstract

This study investigates the control quality of an electric cam phaser system. The impact of different sensor concepts, synchronization algorithms, controller and hardware topologies on the control quality is examined by using a transient simulation covering the electric cam phaser, valve train, mechanical transmission and a wide variety of cam- and crankshaft trigger wheels. Limited angular accuracy effects are simulated by realistic sensor models and the processing of sensor signals by a real-time capable synchronization algorithm. Nonlinear friction in transmission and valve train are considered by the simulation accordingly. Furthermore, the effects of distributed controller algorithms based on conventional electronic control units are evaluated. Communication latencies have a strong impact on the control plant and are taken into account during controller definition. The effects of different layouts are compared in the time domain, and a sensitivity analysis is carried out to evaluate the effects of different parameters on the cam phasing control quality. The control quality is measured in terms of overshoot, phasing duration and energy consumption of a phasing event. Using a sensor fusion for the current cam phasing angle and an integrated controller layout – that is, an architecture without any communication delay – improves the controllability and reduces overshooting, phasing duration and electrical energy consumption under transient conditions.