Laboratory evaluation of moisture performance of weather resistive barriers

The objective of this thesis aimed (1) to evaluate the effectiveness of the existing test methods used in characterizing moisture performance of weather resistive barrier (WRB) products, and (2) to provide a benchmark for assessment of different boundary conditions. The test materials were placed between a layer of water and various types of hygroscopic sinks including vacuum cast gypsum, oriented strand board (OSB), thick adsorbing paper (blotter) and a desiccant (anhydrous calcium chloride). The WRB were either placed directly in contact with the hygroscopic sink or were separated from it by an air gap. These tests indicated that moisture transport was highly dependent on the conditions introduced on the upper and the lower surfaces of the WRB. This thesis reports the results of a series of experimental studies, which examined moisture transport to characterize WRB for input into material standards. The new test methods developed in the thesis include: modified inverted cup ( MIC ) test for measuring the maximum possible total moisture transmission, moisture flux ( MF ) test for measuring moisture flow to an OSB or plywood substrate, and liquid penetration resistance ( LPR ) test for measuring onset and the rate of the liquid phase transport. The test methods were used to examine moisture transport through new WRB. The test were also used to evaluate effect of penetrations, outdoor weathering, and contribution of detergent dissolved in the interstitial water. Subsequent to the material testing, an assembly testing provided a comparative evaluation of such effects as penetrations or additives in a stucco layer. Proposed in this thesis are new laboratory test methods and the acceptance criteria to be incorporated in the next edition of North American material standards. (Abstract shortened by UMI.

Robust unknown input observer for state and fault estimation in discrete-time Takagi-Sugeno systems

In this paper, a robust unknown input observer (UIO) for the joint state and fault estimation in discrete-time Takagi-Sugeno (TS) systems is presented. The proposed robust UIO, by applying the H-infinity framework, leads to a less restrictive design procedure with respect to recent results found in the literature. The resulting design procedure aims at achieving a prescribed attenuation level with respect to the exogenous disturbances, while obtaining at the same time the convergence of the observer with a desired bound on the decay rate. An extension to the case of unmeasurable premise variables is also provided. Since the design conditions reduce to a set of linear matrix inequalities that can be solved efficiently using the available software, an evident advantage of the proposed approach is its simplicity. The final part of the paper presents an academic example and a real application to a multi-tank system, which exhibit clearly the performance and effectiveness of the proposed strategy.Postprint (author's final draft

Development of experimental methods for characterizing water vapor transmission in building materials

Water vapor transmission (WVT) through building materials are determined experimentally using dry cup or wet cup tests. These measurements are typically affected by several sources of uncertainties including air layer resistance, transient behavior of the desiccant, masked edge, as well as temperature and relative humidity of the surrounding environment. WVT cup tests conducted with highly permeable membranes are affected by boundary layer effect on the top surface and by the transient behavior of the moisture sink on the lower surface. WVT cup tests conducted with low permeable materials having moisture storage capacity are lengthy, often requiring several weeks to determine single WVT point at specified set of conditions, which might not be sufficient for input into advanced heat, air and moisture (HAM) models. The objectives of this study were to evaluate the transient behavior of calcium sulfate and silica gel in standard ASTM E96 (2005) dry cup WVT tests conducted with highly permeable construction materials, and based on experimental findings provide recommendations related to frequency of moisture sink replacement in the dry cup WVT tests to improve the current standard. Develop a novel approach for testing WVT of highly permeable materials. A multi-layer approach was developed and verified using highly permeable Class-P WRB membrane. The value of the multi layer approach is that it allows the determination of the Kirchhoff potential function from a single series of tests (continuous material function which can be used as a direct input into CHAMP-BES simulation tool). This leads to added benefits of this approach include: generation of a shortened period of testing, reduced resource needs, and application of the top layer as a buffer layer in isolating the boundary layer effects. An approach of shortening the period of WVT testing by reducing specimen thickness was examined with oriented strand board (OSB). The findings showed that reducing material thickness from 11.6 mm to 6.8 mm decreased the test duration from 900 to 300 hours. The minimum adequate material thickness was determined to be 6.8 mm, and the sensitivity of the dry and the wet cup WVT tests was comparable for OSB thickness greater than or equal to 6.8 mm

A Novel Adaptive Sensor Fault Estimation Algorithm in Robust Fault Diagnosis

The paper deals with a robust sensor fault estimation by proposing a novel algorithm capable of reconstructing faults occurring in the system. The provided approach relies on calculating the fault estimation adaptively in every discrete time instance. The approach is developed for the systems influenced by unknown measurement and process disturbance. Such an issue has been handled with applying the commonly known H∞ approach. The novelty of the proposed algorithm consists of eliminating a difference between consecutive samples of the fault in an estimation error. This results in a easier way of designing the robust estimator by simplification of the linear matrix inequalities. The final part of the paper is devoted to an illustrative example with implementation to a laboratory two-rotor aerodynamical system

Robust Multiple Sensor Fault–Tolerant Control For Dynamic Non–Linear Systems: Application To The Aerodynamical Twin–Rotor System

The paper deals with the problem of designing sensor-fault tolerant control for a class of non-linear systems. The scheme is composed of a robust state and fault estimator as well as a controller. The estimator aims at recovering the real system state irrespective of sensor faults. Subsequently, the fault-free state is used for control purposes. Also, the robust sensor fault estimator is developed in a such a way that a level of disturbances attenuation can be reached pertaining to the fault estimation error. Fault-tolerant control is designed using similar criteria. Moreover, a separation principle is proposed, which makes it possible to design the fault estimator and control separately. The final part of the paper is devoted to the comprehensive experimental study related to the application of the proposed approach to a non-linear twin-rotor system, which clearly exhibits the performance of the new strategy

Virtual Diagnostic Sensors Design for an Automated Guided Vehicle

In recent years, Automated Guided Vehicles (AGVs) have been playing an increasingly important role in producing industry and infrastructure and will soon arrive to other areas of human life such as the transportation of goods and people. However, several challenges still aggravate the operation of AGVs, which limit the amount of implementation. One major challenge is the realization of reliable sensors that can capture the different aspects of the state of an AGV as well as its surroundings. One promising approach towards more reliable sensors is the supplementary application of virtual sensors, which are able to generate virtual measurements by using other sources of information such as actuator states and already existing sensors together with appropriate mathematical models. The focus of the research described in this paper is the design of virtual sensors determining forces and torques acting on an AGV. The proposed novel approach is using a quadratic boundedness approach, which makes it possible to include bounded disturbances acting on the AGV. One major advantage of the presented approach is that the use of complex tire models can be avoided. Information from acceleration and yaw rate sensors is processed in order to realize reliable virtual force and torque sensors. The resulting force and torque information can be used for several diagnostic purposes such as fault detection or fault prevention. The presented approach is explained and verified on the basis of an innovative design of an AGV. This innovative design addresses another major challenge for AGVs, which is the limited maneuvering possibilities of many AGV designs. The innovative design allows nearly unlimited maneuvering possibilities but requires reliable sensor data. The application of the approach in the AGV resulted in the insight that the generated estimates are consistent with the longitudinal forces and torques obtained by a proven reference model

A Combined H 2 / H ∞ Approach for Robust Joint Actuator and Sensor Fault Estimation: Application to a DC Servo-Motor System

The main objective of this paper is to develop an actuator and sensor fault estimation framework taking into account various uncertainty sources. In particular, these are divided into three groups: sensor measurement noise, process-external exogenous disturbances, as well as unknown fault dynamics. Unlike the approaches presented in the literature, here they are not processed in the same way but treated separately in a suitably tailored fashion. Finally, the approach resolves to minimizing their effect on the fault estimation error in either the H 2 or H ∞ sense. As a result, a mixed performance–based actuator fault estimation framework is obtained, along with its convergence conditions. The final part of the paper presents performance analysis results obtained for a DC servo-motor. Subsequently, another three-tank-system-based example is presented. In both cases, the proposed approach is compared with an alternative one, which clearly exhibits its superiority

Neural network-based robust actuator fault diagnosis for a non-linear multi-tank system

International audienceThe paper is devoted to the problem of the robust actuator fault diagnosis of the dynamic non-linear systems. In the proposed method, it is assumed that the diagnosed system can be modelled by the recurrent neural network, which can be transformed into the linear parameter varying form. Such a system description allows developing the designing scheme of the robust unknown input observer within H∞ framework for a class of non-linear systems. The proposed approach is designed in such a way that a prescribed disturbance attenuation level is achieved with respect to the actuator fault estimation error, while guaranteeing the convergence of the observer. The application of the robust unknown input observer enables actuator fault estimation, which allows applying the developed approach to the fault tolerant control tasks

Towards Simultaneous Actuator and Sensor Faults Estimation for a Class of Takagi-Sugeno Fuzzy Systems: A Twin-Rotor System Application

The paper is devoted to the problem of estimating simultaneously states, as well as actuator and sensor faults for Takagi–Sugeno systems. The proposed scheme is intended to cope with multiple sensor and actuator faults. To achieve such a goal, the original Takagi–Sugeno system is transformed into a descriptor one containing all state and fault variables within an extended state vector. Moreover, to facilitate the overall design procedure an auxiliary fault vector is introduced. In comparison to the approaches proposed in the literature, a usual restrictive assumption concerning fixed fault rate of change is removed. Finally, the robust convergence of the whole observer is guaranteed by the so-called quadratic boundedness approach which assumes that process and measurement uncertainties are unknown but bounded within an ellipsoid. The last part of the paper portrays an exemplary application concerning a nonlinear twin-rotor system

Simultaneous estimation of multiple sensor and process faults for non-linear discrete-time systems

International audienceThe paper deals with the problem of simultaneous estimation of sensor and process faults. For that purpose, a novel scheme is proposed and its complete design procedure is described. The approach results in a robust estimation strategy with guaranteed convergence. In particular, apart from simultaneous estimation ability the proposed approach makes it possible to attenuate the exogenous disturbances up to the predefined level. Finally, the design procedure boils down to solving a set of linear matrix inequalities. The last part of the paper shows an illustrative example with the application dedicated to the laboratory twin-rotor aero-dynamical MIMO system