Dieter Schwarzmann

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

Control Concept for a Hydraulic Mobile Machine Using a Haptic Operating Device

A control methodology for the operation of a hydraulic excavator using a haptic operating device is developed. The main idea is to use position controllers for both the excavator and the operating device where both control loops output the reference position to the other, i.e., two position controlled systems are placed in a feedback loop with each other. The human operator acts as an input disturbance to the operating device. This approach allows intuitive operation of the machine and gives the operator haptic feedback of the boom position.Internal model control (IMC) is employed to design the position controllers for both the hydraulic manipulator and the operating device. To this end, a simplified design rule for the IMC filter and a novel anti-windup approach for models with pure integrators are proposed.The master-slave control methodology is exemplified on an 18 ton excavator; measurement results are given.

A Haptically Enhanced Operational Concept for a Hydraulic Excavator

In mobile hydraulic machines, like excavators, backhoe loaders, wheel loaders, and forklift trucks, haptic human-machine interfaces are not in use. Today, the machines are operated with mechanical-hydraulic joysticks. Each joystick axis controls a single hydraulic actuator. This leads to not very easy to use operational concepts. Since electrohydraulic systems with electronic joysticks are available for serial applications, alternative operational concepts become feasible. A known alternative is to control the machine using an operating device whose segments resemble the manipulator geometry, as shown in Fig. 1 (Uchino et al., 1977). This operational concept is often called coordinated control. Typically, a master-slave system is employed where the operating device (master) outputs the reference position to the position control loop of the machine (slave). This concept promises an intuitive operation of the machine.

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

Test signal generation for service diagnosis based on local structural properties

Test signal generation for service diagnosis based on local structural properties The paper presents a new approach to the generation of test signals used in service diagnosis. The tests make it possible to isolate faults, which are isolable only if the system is brought into specific operating points. The basis for the test signal selection is a structure graph that represents the couplings among the external and internal signals of the system and the fault signals. Graph-theoretic methods are used to identify edges that disappear under certain operating conditions and prevent a fault from changing the system behavior at this operating point. These operating conditions are identified by validuals, which are indicators obtained during the graph-theoretic analysis. The test generation method is illustrated by a process engineering example.

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.

Service diagnosis utilizing the dependencies between the system structure and the operating points

The paper presents a new approach to the generation of test signals used in service diagnosis. The tests make it possible to isolate faults, which are generally not isolable, but can be distinguished if the system is brought into specific operating points. The basis for the test signal selection is a graph that represents the couplings among the external and internal signals of the system and the faults. This graph is used to identify edges that disappear under certain operating conditions and prevent a fault from changing the system behavior in this operating point. The test generation method is illustrated by a process engineering example.

Service diagnosis of dynamical systems based on local structural models

The paper presents a new approach to the selection of tests used in service diagnosis of dynamical systems. It proposes a method to select input signals that steer the system into a particular operating region and to find the corresponding local residuals for evaluating the systems I/O behavior. The tests allow the isolation of faults that are generally not distinguishable, but become isolable under specific operation conditions. The method is based on the analysis of the structure graph, which represents the couplings among external and internal signals of the system and the possible faults. This graph changes if the system variables are restricted to different operating regions. Accordingly, the local structure of the system distinguishes from the global structure that holds for the unrestricted variables. By utilizing this difference, it is possible to determine tests that are sensitive to specific faults. The method is illustrated by its application to a throttle valve.

Testgenerierung für die Werkstattdiagnose auf der Basis struktureller Modelle

Zusammenfassung Es wird ein Verfahren zur Bestimmung von automatischen Tests für die Werkstattdiagnose vorgestellt, das ein strukturelles Modell des zu diagnostizierenden Systems nutzt, in dem die Ursache-Wirkungsbeziehungen im fehlerfreien und im fehlerbehafteten Zustand dargestellt sind. Durch die ausgewählten Tests wird das System in Betriebszustände gesteuert, in denen bestimmte Fehler eine signifikante Wirkung entfalten während die Wirkung anderer Fehler verschwindet. Die Vorgehensweise wird am Beispiel der Drosselklappe eines Pkw-Motors illustriert. Abstract A novel approach for the determination of automatic tests for service diagnosis is presented. It uses a structural model of the system that is to be diagnosed in order to represent the cause-effect interrelations in the faultless and in the faulty situation. The selected tests steer the system into operating points in which specific faults have a significant impact on the system behavior whereas the effect of other faults vanishes. The procedure is exemplified by a throttle valve of an automobile engine.