REAL-TIME PREDICTIVE CONTROL OF CONNECTED VEHICLE POWERTRAINS FOR IMPROVED ENERGY EFFICIENCY

The continued push for the reduction of energy consumption across the automotive vehicle fleet has led to widespread adoption of hybrid and plug-in hybrid electric vehicles (PHEV) by auto manufacturers. In addition, connected and automated vehicle (CAV) technologies have seen rapid development in recent years and bring with them the potential to significantly impact vehicle energy consumption. This dissertation studies predictive control methods for PHEV powertrains that are enabled by CAV technologies with the goal of reducing vehicle energy consumption. First, a real-time predictive powertrain controller for PHEV energy management is developed. This controller utilizes predictions of future vehicle velocity and power demand in order to optimize powersplit decisions of the vehicle. This predictive powertrain controller utilizes nonlinear model predictive control (NMPC) to perform this optimization while being cognizant of future vehicle behavior. Second, the developed NMPC powertrain controller is thoroughly evaluated both in simulation and real-time testing. The controller is assessed over a large number of standardized and real-world drive cycles in simulation in order to properly quantify the energy savings benefits of the controller. In addition, the NMPC powertrain controller is deployed onto a real-time rapid prototyping embedded controller installed in a test vehicle. Using this real-time testing setup, the developed NMPC powertrain controller is evaluated using on-road testing for both energy savings performance and real-time performance. Third, a real-time integrated predictive powertrain controller (IPPC) for a multi-mode PHEV is presented. Utilizing predictions of future vehicle behavior, an optimal mode path plan is computed in order to determine a mode command best suited to the future conditions. In addition, this optimal mode path planning controller is integrated with the NMPC powertrain controller to create a real-time integrated predictive powertrain controller that is capable of full supervisory control for a multi-mode PHEV. Fourth, the IPPC is evaluated in simulation testing across a range of standard and real-world drive cycles in order to quantify the energy savings of the controller. This analysis is comprised of the combined benefit of the NMPC powertrain controller and the optimal mode path planning controller. The IPPC is deployed onto a rapid prototyping embedded controller for real-time evaluation. Using the real-time implementation of the IPPC, on-road testing was performed to assess both energy benefits and real-time performance of the IPPC. Finally, as the controllers developed in this research were evaluated for a single vehicle platform, the applicability of these controllers to other platforms is discussed. Multiple cases are discussed on how both the NMPC powertrain controller and the optimal mode path planning controller can be applied to other vehicle platforms in order to broaden the scope of this research

Strain Signals Governed by Frictional‐Elastoplastic Interaction of the Upper Plate and Shallow Subduction Megathrust Interface Over Seismic Cycles

The behavior of the shallow portion of the subduction zone, which generates the largest earthquakes and devastating tsunamis, is still insufficiently constrained. Monitoring only a fraction of a single megathrust earthquake cycle and the offshore location of the source of these earthquakes are the foremost reasons for the insufficient understanding. The frictional‐elastoplastic interaction between the megathrust interface and its overlying wedge causes variable surface strain signals such that the wedge strain patterns may reveal the mechanical state of the interface. To contribute to this understanding, we employ Seismotectonic Scale Modeling and simplify elastoplastic megathrust subduction to generate hundreds of analog seismic cycles at a laboratory scale and monitor the surface strain signals over the model's forearc across high to low temporal resolutions. We establish two compressional and critical wedge configurations to explore the mechanical and kinematic interaction between the shallow wedge and the interface. Our results demonstrate that this interaction can partition the wedge into different segments such that the anelastic extensional segment overlays the seismogenic zone at depth. Moreover, the different segments of the wedge may switch their state from compression/extension to extension/compression domains. We highlight that a more segmented upper plate represents megathrust subduction that generates more characteristic and periodic events. Additionally, the strain time series reveals that the strain state may remain quasi‐stable over a few seismic cycles in the coastal zone and then switch to the opposite mode. These observations are crucial for evaluating earthquake‐related morphotectonic markers and short‐term interseismic time series of the coastal regions

Slow slip in subduction zones: Reconciling deformation fabrics with instrumental observations and laboratory results

Cataclasites are a characteristic rock type found in drill cores from active faults as well as in exposed fossil subduction faults. Here, cataclasites are commonly associated with evidence for pervasive pressure solution and abundant hydro­ fracturing. They host the principal slip of regular earthquakes and the family of so­called slow earthquakes (episodic slip and tremor, low to very low frequency earthquakes, etc.). Slip velocities associated with the formation of the different types of cataclasites and conditions controlling slip are poorly constrained both from direct observations in nature as well as from experimental research. In this study, we explore exposed sections of subduction faults and their dominant microstructures. We use recently proposed constitutive laws to estimate deformation rates, and we compare predicted rates with instrumental observations from subduction zones. By identifying the maximum strain rates using fault scaling relations to constrain the fault core thickness, we find that the instrumental shear strain rates identified for the family of “slow earthquakes” features range from 10−3s−1 to 10−5s−1. These values agree with estimated rates for stress corrosion creep or brittle creep possibly controlling cataclastic deformation rates near the failure threshold. Typically, pore­fluid pressures are suggested to be high in subduction zones triggering brittle deformation and fault slip. However, seismic slip events causing local dilatancy may reduce fluid pressures promoting pressure­solution creep (yielding rates of <10−8 to 10−12s−1) during the interseismic period in agreement with dominant fabrics in plate interface zones. Our observations suggest that cataclasis is controlled by stress corrosion creep and driven by fluid pressure fluctuations at near­lithostatic effective pressure and shear stresses close to failure. We posit that cataclastic flow is the dominant physical mechanism governing transient creep episodes such as slow slip events (SSEs), accelerating preparatory slip before seismic events, and early afterslip in the seismogenic zone

Growing Faults in the Lab: Insights into the Scale Dependence of the Fault Zone Evolution Process

Analog sandbox experiments are a widely used method to investigate tectonic processes that cannot be resolved from natural data alone, such as strain localization and the formation of fault zones. Despite this, it is still unclear, to which extent the dynamics of strain localization and fault zone formation seen in sandbox experiments can be extrapolated to a natural prototype. Of paramount importance for dynamic similarity is the proper scaling of the work required to create the fault system, Wprop. Using analog sandbox experiments of strike-slip deformation, we show Wprop to scale approximately with the square of the fault system length, l, which is consistent with the theory of fault growth in nature. Through quantitative measurements of both Wprop and strain distribution we are able to show that Wprop is mainly spent on diffuse deformation prior to localization, which we therefore regard as analogous to distributed deformation on small-scale faults below seismic resolution in natural fault networks. Finally, we compare our data to estimates of the work consumed by natural fault zones to verify that analog sandbox experiments scale properly with respect to energy, i. e. that they scale truly dynamically

Creep on seismogenic faults: Insights from analogue earthquake experiments

Tectonic faults display a range of slip behaviors including continuous and episodic slip covering rates of more than 10 orders of magnitude (m/s). The physical control of such kinematic observations remains ambiguous. To gain insight into the slip behavior of brittle faults we performed laboratory stick-slip experiments using a rock analogue, granular material. We realized conditions under which our seismogenic fault analogue shows a variety of slip behaviors ranging from slow, quasi continuous creep to episodic slow slip to dynamic rupture controlled by a limited number of parameters. We explore a wide parameter space by varying loading rate from those corresponding to interseismic to postseismic rates and normal loads equivalent to hydrostatic to lithostatic conditions at seismogenic depth. The experiments demonstrate that significant interseismic creep and earthquakes may not be mutually exclusive phenomena and that creep signals vary systematically with the fault’s seismic potential. Accordingly, the transience of interseismic creep scales with fault strength and seismic coupling as well as with the maturity of the seismic cycle. Loading rate independence of creep signals suggests that mechanical properties of faults (e.g. seismic coupling) can be inferred from shortterm observations (e.g. aftershock sequences). Moreover, we observe the number and size of small episodic slip events to systematically increase towards the end of the seismic cycle providing an observable proxy of the relative shear stress state on seismogenic faults. Modelling the data suggest that for very weak faults in a late stage of their seismic cycle, the observed creep systematics may lead to the chimera of a perennially creeping fault releasing stress by continuous creep and/or transient slow slip instead of large earthquakes

Interseismic deformation transients and precursory phenomena: Insights from stick-slip experiments with a granular fault zone

The release of stress in the lithosphere along active faults shows a wide range of behaviors spanning several spatial and temporal scales. It ranges from short-term localized slip via aseismic slip transients to long-term distributed slip along large fault zones. A single fault can show several of these behaviors in a complementary manner often synchronized in time or space. To study the multiscale fault slip behavior with a focus on interseismic deformation transients we apply a simpli�ed analog model experiment using a rate-and-state-dependent frictional granular material (glass beads) deformed in a ring shear tester. The analog model is able to show, in a reproducible manner, the full spectrum of natural fault slip behavior including transient creep and slow slip events superimposed on regular stick-slip cycles (analog seismic cycles). Analog fault slip behavior is systematically controlled by extrinsic parameters such as the system sti�ness, normal load on the fault, and loading rate. Accordingly, interseismic creep and slow slip events increase quantitatively with decreasing normal load, increasing sti�ness and loading rate. We observe two peculiar features in our analog fault model: (1) Absence of transients in the �final stage of the stick-slip cycle ("preseismic gap") and (2) "scale gaps" separating small interseismic slow (aseismic) events from large (seismic) fast events. Concurrent micromechanical processes, such as dilation, breakdown of force chains and granular packaging a�ect the frictional properties of the experimental fault zone and control interseismic strengthening and coseismic weakening. Additionally, interseismic creep and slip transients have a strong e�ect on the predictability of stress drops and recurrence times. Based on the strong kinematic similiarity between our fault analog and natural faults, our observations may set important constraints for time-dependent seismic hazard models along single faults

Die historische Rheinpolitik der Franzosen

Digitalisat der Ausgabe sechstes Tausend von 1922, erschienen 201

On the efficient and reliable numerical solution of rate-and-state friction problems

We present a mathematically consistent numerical algorithm for the simulation of earthquake rupture with rate-and-state friction. Its main features are adaptive time-stepping, a priori mesh-adaptation, and a novel algebraic solution algorithm involving multigrid and a fixed point iteration for the rate-and-state decoupling. The algorithm is applied to a laboratory scale subduction zone which allows us to compare our simulations with experimental results. Using physical parameters from the experiment, we find a good fit of recurrence time of slip events as well as their rupture width and peak slip. Preliminary computations in 3D confirm efficiency and robustness of our algorithm

Das Rätsel der Anden-Orogenese: Ist der Erdmantel für den Start der Gebirgsbildung verantwortlich?

To this date, the question of why and how a plateau-type orogen formed with massive crustal thickening at the leading edge of western South America remains one of the hotly debated issues in geodynamics. During the Cenozoic, the Altiplano and Puna plateau of the Central Andes developed during continuous subduction of the oceanic Nazca plate in a convergent continental margin setting – a situation that is unique along the 60 000 km of convergent margins around the globe. The key challenge is to understand why a first-order mechanical instability of the later plateau extent developed along the central portion of the leading edge of South America only, as well as why and how this feature developed only during the Cenozoic, although the cycle of Andean subduction had been ongoing since at least the Jurassic. Although the widespread presence of partial melts or metamorphic fluids at mid-crustal level has been suggested to indicate upper plate weakening from heating and partial melting, it is recently found that upper plate strain weakening at lithospheric scale plays a significantly larger role. This first order control is tuned by factors affecting the strength balance between the upper plate lithosphere and the plate interface of the Nazca and South American plates such as variations in trenchward sediment flux affecting plate interface coupling and slab rollback or the role of inherited structures. Late initiation of orogeny in the Eocene, however, and its sustained action over tens of million years is now found to be related to the penetration of the slab into the lower mantle around 50 Ma ago, producing a slowdown of the lateral slab migration (‚slab anchoring’), and dragging the upper plate against the subduction zone by large-scale return flow. The combination of these parameters was highly uncommon during the Phanerozoic leading to very few plateau style orogens at convergent margins like the Cenozoic Central Andes in South America or the Laramide North American Cordillera