<p>To fulfil emission requirements specified by environment demands, such as Euro 4 and Euro 5, there is a need to utilize engines based on technologies such as Variable Turbine Geometry (VGT) and Exhaust Gas Recirculation (EGR). A model of an engine using VGT and EGR was created by Ph.D student Johan Wahlström at Linköping University. This thesis evaluates Wahlström's model and shows how it successfully describes the engine and its behaviour. The thesis also confirms theories about the occurrens of non.minimum phase behaviour in different transfer functions, e.g. from VGT signal to the mass flow through the compressor.</p><p>An interesting phenomenon when applying VGT and EGR is a nonlinearity leading to, for example, that the same pressure in the intake manifold can occur for two different VGT signals. Such phenomenon can cause problems when designing a control system. Furthermore, this nonlinearity also results in a replacement of the nonminimum phase behaviour with an overshoot when a large (above 80%) VGT control signal is used.</p><p>This thesis also provides a linearized model, which describes the engine satisfactory. The linearization results in transfer functions with two zeros and three poles, whose locations do not change much when varying engine speed and load (except at high load and low engine speed). This fact will most likely make it possible to utilize just a few different linearizations for all speeds and loads. However, altering VGT and EGR positions greatly affect the transfer functions. Thus, several linearizations are probably needed to cover all operating points.</p><p>When designing a future control system a good strategy is to utilize a decoupled system since the model has strong cross-connections. Another solution would be to apply multi dimensional control strategy, e.g. LQ-theory.</p>

To fulfil emission requirements specified by environment demands, such as Euro 4 and Euro 5, there is a need to utilize engines based on technologies such as Variable Turbine Geometry (VGT) and Exhaust Gas Recirculation (EGR). A model of an engine using VGT and EGR was created by Ph.D student Johan Wahlström at Linköping University. This thesis evaluates Wahlström's model and shows how it successfully describes the engine and its behaviour. The thesis also confirms theories about the occurrens of non.minimum phase behaviour in different transfer functions, e.g. from VGT signal to the mass flow through the compressor. An interesting phenomenon when applying VGT and EGR is a nonlinearity leading to, for example, that the same pressure in the intake manifold can occur for two different VGT signals. Such phenomenon can cause problems when designing a control system. Furthermore, this nonlinearity also results in a replacement of the nonminimum phase behaviour with an overshoot when a large (above 80%) VGT control signal is used. This thesis also provides a linearized model, which describes the engine satisfactory. The linearization results in transfer functions with two zeros and three poles, whose locations do not change much when varying engine speed and load (except at high load and low engine speed). This fact will most likely make it possible to utilize just a few different linearizations for all speeds and loads. However, altering VGT and EGR positions greatly affect the transfer functions. Thus, several linearizations are probably needed to cover all operating points. When designing a future control system a good strategy is to utilize a decoupled system since the model has strong cross-connections. Another solution would be to apply multi dimensional control strategy, e.g. LQ-theory.

A VGT or Variable-Geometry Truss can be thought of as a statically determinate truss that has been modified to contain some number of variable length members. These extensible members allow the truss to vary its configuration in a controlled manner. VGTs are often symmetric. constructed of repeating cells, and have exceptional stiffness to weight ratios. VGTs have been widely recognized as adaptive or collapsing structures for space and military applications. Some of the typical applications envisioned for VGTs are as booms to position equipment in space. as supports for space antennae. and as berthing devices. Lately, they have also been proposed as parallel-actuated. long chain. high dexterity manipulators. This work describes basic VGT theory. and presents criteria to use in the determination of valid VGT unit cells. Four of the VGT unit cells - the tetrahedron. the octahedron, the decahedron. and the dodecahedron are discussed in detail. The typical modeling and formulation procedure for developing the kinematic equations associated with the forward kinematic problem of each of the above is described. Another intent of this work is to present a new and efficient technique for solving the forward kinematics problem of VGTs. All VGT problems lead to systems of equations. Commonly, such systems are solved by an iterative numerical method, usually a Newton method or a variant. For such methods to yield a solution, a starting point sufficiently close to the actual solution must be supplied. For systems of the size of those encountered in VGT problems, this is a formidable task. On the other hand, recently developed methods in homotopy continuation for polynomials are not only global, but also exhaustive; i.e., they do not require good initial guesses and they also guarantee convergence to all solutions. Homotopies are a traditional part of topology and have only recently begun to be used for practical numerical computation. Polynomial continuation is used to track the solutions of the systems of equations describing the kinematics of VGTs. This method has proven to be robust and reliable. It may also prove to be a valuable tool in the analysis of other kinematic devices with a high multiplicity of solutions. / Ph. D.

No description available.

Tensegrity structures consist of isolated compression members (rigid bars) suspended by a continuous network of tension members (cables). Tensegrity structures can be used as variable geometry truss (VGT) mechanisms by actuating links to change their length. This paper will present a new method of position finding for tensegrity structures that can be used for actuation as VGT mechanisms. Tensegrity structures are difficult to understand and mathematically model. This difficulty is primarily because tensegrity structures only exist in specific stable tensegrity positions. Previous work has focused on analysis based on statics, dynamics, and virtual work approaches. This work considers tensegrity structures from a kinematic viewpoint. The kinematic approach leads to a better understanding of the conditions under which tensegrity structures exist in the stable positions. The primary understanding that comes from this kinematic analysis is that stable positions for tensegrity structures exist only on the boundaries of nonassembly of the structure. This understanding also allows the tensegrity positions to be easily found. This paper presents a method of position finding based on kinematic constraints and applies that method to several example tensegrity structures. / Master of Science

<p>Today’s diesel engines are complex with systems like VGT and EGR to be able to fulfil the stricter emission legislations and the demands on the fuel consumption. Controlling a system like this demands a sophisticated control system. Furthermore, the authorities demand on self diagnosis requires an equal sophisticated diagnosis system. These systems require good knowledge about the signals present in the system and how they affect each other.</p><p>One way to achieve this is to have a good model of the system and based on this calculate an observer. The observer is then used to estimate signals used for control and diagnosis. Advantages with an observer instead of using just sensors are that the sensor signals often are noisy and need to be filtered before they can be used. This causes time delay which further complicates the control and diagnosis systems. Other advantages are that sensors are expensive and that some engine quantities are hard to measure.</p><p>In this Master’s thesis a model of a Scania diesel engine is developed and an observer is calculated. Due to the non-linearities in the model the observer is based on a constant gain extended Kalman filter.</p>

Today’s diesel engines are complex with systems like VGT and EGR to be able to fulfil the stricter emission legislations and the demands on the fuel consumption. Controlling a system like this demands a sophisticated control system. Furthermore, the authorities demand on self diagnosis requires an equal sophisticated diagnosis system. These systems require good knowledge about the signals present in the system and how they affect each other. One way to achieve this is to have a good model of the system and based on this calculate an observer. The observer is then used to estimate signals used for control and diagnosis. Advantages with an observer instead of using just sensors are that the sensor signals often are noisy and need to be filtered before they can be used. This causes time delay which further complicates the control and diagnosis systems. Other advantages are that sensors are expensive and that some engine quantities are hard to measure. In this Master’s thesis a model of a Scania diesel engine is developed and an observer is calculated. Due to the non-linearities in the model the observer is based on a constant gain extended Kalman filter.

Indiana University-Purdue University Indianapolis (IUPUI) / Stringent regulatory requirements and modern diesel engine technologies have engaged automotive manufacturers and researchers in accurately predicting and controlling diesel engine-out emissions. As a result, engine control systems have become more complex and opaquer, increasing the development time and costs. To address this challenge, Model-based control methods are an effective way to deal with the criticality of the system study and controls. And physics-based combustion engine modeling is a key to achieve it. This thesis focuses on development and validation of a physics-based model for both engine and emissions using model-based design tools from MATLAB & Simulink. Engine model equipped with exhaust gas circulation and variable geometry turbine is adopted from the previously done work which was then integrated with the combustion and emission model that predicts the heat release rates and NOx emission from engine. Combustion model is designed based on the mass fraction burnt from CA10 to CA90 and then NOx predicted using the extended Zeldovich mechanism. The engine models are tuned for both steady state and dynamics test points to account for engine operating range from the performance data. Various engine and combustion parameters are estimated using parameter estimation toolbox from MATLAB and Simulink by applying the least squared solver to minimize the error between measured and estimated variables. This model is validated against the virtual engine model developed in GT-power for Cummins 6.7L turbo diesel engine. To account for the harmonization of the testing cycles to save engine development time globally, a world harmonized stationary cycle (WHSC) is used for the validation. Sub-systems are validated individually as well as in a loop with a complete model for WHSC. Engine model validation showed promising accuracy of more than 88.4 percent on average for the desired parameters required for the NOx prediction. NOx estimation is accurate for the cycle except the warm-up and cool-down phase. However, NOx prediction during these phases is limited due to actual NOx measured data for tuning the model for real-time NOx estimation. Results are summarized at the end to compare the trend of NOx estimation from the developed combustion and emission model to show the accuracy of in-cylinder parameters and required for the NOx estimation.

No description available.

In this master’s thesis, a turbine model and a common control structure for theturbocharger for SI and CI-engines is developed. To design the control structure,simulations are done on an existing diesel engine model with VGT. In order tobe able to make simulations for engines with a wastegated turbine, the model isextended to include mass flow and turbine efficiency for that configuration. Thedeveloped model has a mean absolute relative error of 3.6 % for the turbine massflow and 7.4 % for the turbine efficiency. The aim was to control the intake manifoldpressure with good transients and to use the same control structure for VGTand wastegate. By using a common structure, development and calibration timecan be reduced. The non-linearities have been reduced by using an inverted turbinemodel in the control structure, which consists of a PI-controller with feedforward.The controller can be tuned to give a fast response for CI engines and a slowerresponse but with less overshoot for SI engines, which is preferable.