Variable Geometry Turbo Research Articles

Dual-output PID transient control of an electric-assisted air charge system

Turbo-compressor assembly (also called turbocharger) is added to diesel engines to increase their power density and improve performance. However, during power step-up operations, the added turbocharger system could lead to a significant delay of engine response (also called turbo-lag) which negatively impact drivability. In this paper, an external electric compressor (eBoost) is added to a turbocharged, large displacement diesel engine to significantly reduce turbo-lag, along with a bypass valve. Now, the air charge system has two control targets (boost (intake manifold) pressure and rate of exhaust-gas recirculation (EGR)) but with four control actuators including EGR valve, variable geometry turbo (VGT) vane position, eBoost speed and bypass valve, making it challenge for developing the associated control scheme. In this paper, a dual-output PID (proportional-integral-derivative) controller is proposed for controlling the boost pressure using the VGT and eBoost to reduce turbo-lag, and a transition logic is also devised to detect transient operating conditions to activate the eBoost, along with the closing and opening of the bypass valve, with maximum benefit. The EGR rate PID control remains unchanged. The addition of the eBoost is shown to improve transient response time by up to 55% and reduce transient NOx emissions by up to 42% during transitional operations without negatively impacting steady-state engine performance or emissions. Note that transient performance can be further improved for production implementation when a single engine control module is used by eliminating communication delay among multiple control systems.

Unified FDI and FTC Scheme for Air Path Actuators of a Diesel Engine Using ISM Extended with Adaptive Part

AbstractA unified fault detection and isolation (FDI) and fault tolerant control (FTC) strategy for the diesel engine's air management system has been formulated. Diesel engines need to comply with the strict emission requirements for which they are equipped with specialized sub‐systems for the purpose, such as the variable geometry turbo (VGT) charger and exhaust gas recirculation (EGR). Hardware‐based controls tend to make the system more complex and prone to structured and unstructured faults. This calls for an advanced FTC technique that can ensure desired level of emissions even in the presence of minor system malfunctions. The scheme proposed in this paper detects, isolates and estimates the structured faults and minimizes their effects by re‐positioning the actuators using integral sliding mode (ISM) control. Estimating the magnitude of structured faults help to reduce the ISM controller gains, eventually reducing the chattering. The stability of the system is analyzed using Lyapunov stability criterion. Simulations have been performed using fully validated industrial scale model of a diesel engine to elucidate the effectiveness of our scheme.

MULTIVARIABLE CONTROL DESIGN FOR INTAKE FLOW REGULATION OF A DIESEL ENGINE USING SLIDING MODE

Stringent CAFÉ regulations along with technological advances in materials, high-pressure fuel injection and complex turbo charging systems have rekindled interest in the area of Diesel engines for passenger vehicle applications. A modern Diesel engine is not only clean and quiet but also allows comparable drivability relative to gasoline engines with considerable improvements in fuel economy. However the current generation diesel engine is a complex system. It is not uncommon to find features like Variable Geometry Turbo charging (VGT), Exhaust Gas Recirculation (EGR) and High Pressure Common Rail (HPCR) fuel injection. In this paper we discuss the design of a multivariable controller for the VGT-EGR system for intake flow regulation. Control design is carried out under the sliding mode framework.