Rainer Nitsche

Pressure control of a two-stage turbocharged diesel engine using a novel nonlinear IMC approach

This paper deals with nonlinear multivariable output feedback control of a two-stage turbocharged diesel engine. The feedback structure of internal model control (IMC) is used in combination with a nonlinear feedforward controller based on geometric nonlinear control design methods. Input saturations as well as measured disturbances are taken into account and a severe rank deficiency is handled. This novel control approach is the first model-based solution to this problem and results in impressive control performance

A flatness-based approach to internal model control

The design principle of internal model control (IMC) focuses on developing a feedforward controller which also acts in the feedback loop to attenuate disturbances. This paper uses ideas developed in the theory of flat systems for the design of feedforward controllers and adapts them to IMC control. By extending this idea, a method for output feedback control of nonlinear flat systems is presented. It shows the interesting result that the classical design procedure for IMC controllers and the new flatness-based approach end up with identical results for linear systems

Fault-tolerant Internal Model Control with Application to a Diesel Engine

Abstract The paper proposes a new structure for fault-tolerant control of nonlinear systems subject to persistent faults. The principle of Internal Model Control (IMC) is extended to ensure fault tolerance with respect to faults that do not affect the plant stability. The method is based on a representation of sensor, actuator and plant faults as parameter changes of the plant model, which is part of the IMC control law. It is proved that the IMC control loop, which is extended by a diagnostic unit, tolerates substantial faults and ensures the nominal loop performance unless the fault changes the structure of the nonlinear plant. These results are illustrated for the air path of a Diesel engine.

NONLINEAR MULTIVARIABLE ROBUST INTERNAL MODEL CONTROL OF A TWO-STAGE TURBOCHARGED DIESEL ENGINE

Abstract This paper proposes a new approach to the design of Internal Model Controllers (IMC) for nonlinear systems with emphasis on robustness issues. A nonlinear IMC controller is used which is based on the right inverse of the plant model. As the right inverse is, in general, not realisable, it is combined with a linear filter. The right inverse is constructed using nonlinear geometric control methods for input-affine systems. Robust stability of the closed-loop is investigated for unstructured (multivariable) output uncertainties. The industrial feasibility of the controller and the robustness analysis is shown for the nonlinear IMC control loop of a two-stage turbocharged diesel engine.

Fault-Tolerant Internal Model Control of a Diesel Engine Air Path

Abstract The paper considers the fault-tolerant control of the boost pressure and the exhaust gas recirculation of a two-stage turbocharged Diesel engine air path. The aim is to recover the stability and setpoint tracking properties of the closed-loop system in case of actuator, sensor or system faults. A model of the nominal air path is extended to describe the Diesel engine under the influence of the faults and to apply the principle of Fault-Tolerant Internal Model Control (FTIMC). The application study compares the FTIMC scheme with the nominal Internal Model Control of the Diesel engine and shows that for several important fault cases the FTIMC principle recovers the stability of the control loop and leads to severe improvements of setpoint tracking properties.

Internal Model Control of Nonlinear Systems with Input Saturation

Abstract An Internal Model Control structure for nonlinear, stable single-input single-output systems with actuator saturation is proposed. The main topic is the analysis of the stability and the steady-state input-output behaviour of the IMC filter which is an integral part of the IMC structure. Despite of the actuator magnitude limitation and the plant nonlinearities, the closed IMC loop is shown to be internally stable and to possess the set-point tracking property. The performance of the approach is demonstrated by its application to the intake manifold pressure control of a combustion engine. Zusammenfassung Der Beitrag beschreibt die Eigenschaften einer IMC-Regelung für nichtlineare stabile Eingrößensysteme mit Stellgrößenbegrenzung. Der Schwerpunkt liegt bei der Analyse der Stabilität und des stationären Eingangs-Ausgangsverhaltens des IMC-Filters, das Bestandteil der IMC-Regelung ist. Es wird bewiesen, dass der IMC-Regelkreis trotz der Stellgrößenbegrenzung und der nichtlinearen Streckeneigenschaften stabil ist und die Eigenschaft der Sollwertfolge besitzt. Die Leistungsfähigkeit des Ansatzes wird anhand der Regelung des Saugrohrdrucks vor einem Verbrennungsmotor demonstriert.

A new structure for fault-tolerant internal model control

Internal Model Control (IMC) has been extended recently to a fault-tolerant IMC scheme (FTIMC), which ensures that the main IMC properties like stability, robustness and setpoint tracking are retained if faults occur. This paper proposes a new type of IMC controller for input-affine systems with input-saturation, which is based on a systematic analysis of the demands on the IMC filter, the construction of the filter and its subsequent extension to an IMC controller. Properties of FTIMC with the new controller are derived and demonstrated by a process engineering example.

Fault Tolerant Oxygen Control of a Diesel Engine Air System

Abstract This paper is devoted to the fault tolerant control problem of a Diesel engine air system having a jammed Exhaust Gas Recirculation (EGR) valve. The fault tolerant control is based on replaning the trajectory in order to track a new controlled variable which is the oxygen concentration in the intake manifold instead of the fresh air mass flow. The trajectory planning is based on an inverse model approach, utilizing the fundamental thermodynamic relations of the air system.