Indiana University-Purdue University Indianapolis

IUPUI School of Engineering and Technology

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Analytical Redundancy Based Fault Tolerant Control of Drive By Wire Systems Through Predictive Observers:

 In order to achieve high level of reliability for a By-Wire system, double, triple, or even quadruple redundant sensors, actuators, communication networks, and controllers are needed. But this added hardware increases the overall cost of the vehicle. Novel analytical redundancy methodology is investigated here to reduce the total number of redundant road-wheel angle (RWA) sensors in a triply redundant RWA-based SBW system, while maintaining a high level of reliability. A full state predictive observer, which has its roots in Generalized Predictive Control (GPC), has been designed using the combined model of the vehicle and SBW system to estimate the vehicle body side slip angle using motor current and measure yaw rate as input variables. The steering angle can be then estimated from the observed and measured states of the vehicle (body side slip angle and yaw rate) as well as the current input to the SBW electric motor(s). With at least two physical road-wheel angle sensors and the analytical estimation of the RWA value (which replaces the third physical sensor), a fault detection and isolation (FDI) algorithm is being developed using a majority voting scheme. The FDI algorithm can then be used to detect faulty sensor(s) in order to maintain safe drivability. The proposed analytical redundancy based fault detection & isolation algorithms have been modeled SIMULINK. The preliminary results indicate that the predictive observers can provide early fault diagnosis than conventional observers.

Parallel Processing in SIMULINK for Fast Simulation:

Modeling and simulation are integral parts of the development of systems including vehicle and engine systems in the automotive field.  New emissions regulations and technological advances are two of the primary incentives towards the continued development of more complex system models.  As the models become more complex, their computation times increase.  Traditionally, the model, as a whole, would be evaluated at a single time step that would give the desired stability and accuracy for all states.  It is hypothesized that the models be partitioned allowing different portions of the model be solved at different time steps, allowing each state to be evaluated at a time step that will give the desired stability and accuracy.  Furthermore, with the model operating at several time steps, each time step could be solved on a separate processor of a multiple processor machine.  Using a Simulink® model of a multiple degree of freedom, spring, mass, damper system, multiple time steps is being created through the use of rate transition blocks and discrete integrators.  A multithreaded program will then be created by modifying the rsim_main.c script, the main/timing control program for compiled Simulink® models.  These modifications include the creation of a thread for each subsystem operating with a different time step.  Each of the threads contain its own local clock and dependencies are assigned between the main thread and the subsystem threads through the use of conditional waits/signals and mutexes.  This modified program is executed under Linux operating system on a dual Xeon computer with hyperthreading enabled.

Optimal Control of All Wheel Drive System for Hybrid Vehicles for Traction Enhancement

A novel optimal control law for an on-demand all wheel drive vehicle with hybrid powertrain for traction enhancement via slip regulation in a driving event is being investigated. Based on a reasonably simplified vehicle model (bicycle model) and optimization of a performance index based on wheel slip, a closed loop actuator control law is derived. The proposed optimal controller tries to minimize the wheel slip error by dynamically controlling drive torque of the default driven wheel pair (e.g. front wheels) and activating the electric motor connected to the non-driven wheel pair (e.g. rear wheels), in order to enhance vehicle longitudinal traction. The proposed control law has been analyzed for closed-loop stability via Lyapunov stability criteria. Stability conditions for which the control law provides closed-loop stability has been generated. Simulation of the proposed controller is being performed on a validated 14 degree-of-freedom detailed vehicle model in SIMULINK.

Microwave Aided Sinter Forming of High Temperature Components with Compositionally Modulated Microstructures

High-temperature intermetallics (e.g., g - TiAl ) are attractive for engine components in aerospace and automotive sectors due to their high strength-to-weight ratio, excellent oxidation resistance, low density, moderate fracture toughness, and most importantly non-catastrophic failure modes at elevated operating temperatures. However, intermetallics are normally very brittle. The strength and life are highly sensitive to micro-damages that may nucleate during their manufacturing and later service conditions. As a feasibility study, we will focus on processing a net-shape blank for an exhaust valve. Based on detailed material characterization, reaction kinetics and unit cell studies, we will first design and develop a Microwave-Aided Sinter Forming (MASF) facility with emphasis on design flexibility.