Horst Schulte

Robust adaptive fault detection using global state information and application to mobile working machines

In this paper, an observer-based fault detection approach for a class of nonlinear systems is presented, which can be modeled by Takagi-Sugeno (TS) fuzzy models. We propose a sliding mode fuzzy observer that deals with bounded uncertainties in the plant and allows fault estimation based on an equivalent output error injection approach [3]. Furthermore an adaption scheme based on pattern recognition algorithms is presented. It allows to deal with situational uncertainties, which affect the system, by adapting the fault sensitivity. An extensive simulation of a mobile working machine is used to demonstrate the effectiveness of the proposed scheme.

Model-Based Nonlinear Trajectory Control of a Drive Chain with Hydrostatic Transmission

Abstract This paper presents an innovative nonlinear trajectory control scheme for drive chains based on a hydrostatic transmission, which are commonly used in working machines. Control-oriented modelling results in a system of four nonlinear differential equations including the actuator dynamics. It is shown that the differential pressure of the hydrostatic transmission and the angular velocity of the hydraulic motor as controlled variables represent flat control outputs. Therefore, the differential flatness of the system is exploited in combination with Ljapunov techniques to stabilize the error dynamics. Additionally, model uncertainties in the equation of motion like nonlinear friction are counteracted by an observer-based disturbance compensation. Simulation results show an excellent control performance.

Control-Oriented Modeling of Hydrostatic Transmissions using Takagi-Sugeno Fuzzy Systems

Hydrostatic transmissions, also called hydrostatic gears, have been widely used in mobile machines and off-road vehicles such as wheel loaders, graders or tractors. The hydrostatic transmissions are gears with high power density which offer important advantages like continuously variable transmission, maximum tractive force at low speeds and reversing without changing gear. In the industrial practice the transmission output torque, transmission ratio or output speed are usually controlled by model-free PID control methods. This approach results in limited closed-loop bandwidth, limited working efficiency and accuracy due to the high nonlinear characteristic of the plant. This paper presents a control-oriented model of a general hydrostatic transmission as a first step towards a multivariable model-based fuzzy state feedback gain scheduling controller. The controller structure based on parallel distributed compensation scheme (PDC) using Takagi-Sugeno (TS) fuzzy models of the plant. First principles are used to determine the structure of the TS fuzzy model. The applicability of the approach is shown by simulation studies.

Observer Design Using T-S Fuzzy Systems for Pressure Estimation in Hydrostatic Transmissions

Hydrostatic transmissions, also called hydrostatic gears, have been widely used in mobile working machines and off-road vehicles such as construction and agricultural machines. This kind of transmission offers important advantages like continuously variable transmission with high power density, maximum tractive force at low speeds and reversing without changing gear. The automatic electronic control of hydrostatic transmissions, which depend on a number of measurable values, has become more common in industrial practice. To ensure the reliability and safety at least a two-channel redundant system for the measuring channels is required. In this paper, a general model-based approach using a Takagi-Sugeno (T-S) fuzzy observer for analytical redundancy of the oil pressure measuring process in hydrostatic transmissions is developed. It has been shown by experimental results that this approach can be used to estimate the pressure values under varying load conditions and different driving situations.

Disturbance Compensation by Wind Speed Reconstruction based on a Takagi-Sugeno Wind Turbine Model

In this work, the nonlinear Tagaki-Sugeno modelling method is utilised to set up an observer-based feed-forward control scheme for wind turbines, which can compensate for the influence of the disturbing wind variation on the rotational speed. The applied scheme leads to a reduced thrust force acting on the rotor.

On nonlinear observers in Takagi-Sugeno form based on fixed and variable structure

This paper analyses the observer synthesis for a class of nonlinear systems represented by Takagi-Sugeno models with premise variables depending on unmeasurable system states. It is well known that in case of unmeasurable premise variables the time-varying difference of the membership functions with true and estimated premise variables has to be considered in general as external disturbances or unknown disturbances. For this class of design problems, in recent years, some methods have been proposed that allow a systematic synthesis using stability conditions in terms of LMIs. Common to all methods is the use of observer laws with a fixed error feedback term, where the synthesis based on more or less conservative assumptions of the error bounds. The main contribution of this paper is to establish a variable structure observer, that is robust to time-varying error caused by unknown premise variables and disturbed inputs. To illustrate the applicability, the design approach is demonstrated by the Rössler hyperchaotic system.

Two-layer observer-based FDI with application to NREL 5 MW wind turbine model

In this paper, a two-layer fault detection and isolation (FDI) scheme with application in wind turbines is presented. Commonly, model-based FDI concepts use a suitable mathematical model of the plant as a redundancy for on-line available data such as measurements and control outputs. In addition, the proposed two-layer concept exploits the redundancy between component and structure models at their common physical interfaces. It is shown by a illustrated example how the FDI problem can be formalized to a two-layer scheme. First, the models of both layers are proposed, a observer is derived for the component-layer and combined with the structure-layer. Applicability is shown by means of the NREL 5 MW reference wind turbine with objective of detection and isolation of parameter faults in the blade slewing bearings and blade structure.

Control Engineering Analysis of Mechanical Pitch Systems

With the help of a local stability analysis the coefficient range of a discrete damper, used for centrifugal forced, mechanical pitch system of small wind turbines (SWT), is gained for equilibrium points. – By a global stability analysis the gained coefficient range can be validated. An appropriate approach by Takagi-Sugeno is presented in the paper.

CONTROL-ORIENTED MODELING OF HYDROSTATIC TRANSMISSIONS CONSIDERING LEAKAGE LOSSES

Abstract Hydrostatic Transmissions, also called hydrostatic gears, have been widely used in mobile machines and off-road vehicles such as wheel loaders, graders or tractors. The hydrostatic transmissions are gears with high power density which offer important advantages like continuously variable transmission, maximum tractive force at low speeds and reversing without changing gear. In the industrial practice the transmission output torque, transmission ratio or output speed are usually controlled by model-free PID control methods. This approach results in limited closed-loop bandwidth, limited working efficiency and accuracy due to the high nonlinear characteristic of the plant. This paper presents a control-oriented model of a general hydrostatic transmission as a first step towards a multivariable model-based fuzzy state feedback gain scheduling controller based on parallel distributed compensation scheme (PDC) using Takagi-Sugeno (TS) fuzzy systems. First principles are used to determine the structure of the TS fuzzy system. The relevance of the approach is shown by simulation studies.