Zero-shot Deep Reinforcement Learning Driving Policy Transfer for Autonomous Vehicles based on Robust Control

Although deep reinforcement learning (deep RL) methods have lots of strengths that are favorable if applied to autonomous driving, real deep RL applications in autonomous driving have been slowed down by the modeling gap between the source (training) domain and the target (deployment) domain. Unlike current policy transfer approaches, which generally limit to the usage of uninterpretable neural network representations as the transferred features, we propose to transfer concrete kinematic quantities in autonomous driving. The proposed robust-control-based (RC) generic transfer architecture, which we call RL-RC, incorporates a transferable hierarchical RL trajectory planner and a robust tracking controller based on disturbance observer (DOB). The deep RL policies trained with known nominal dynamics model are transfered directly to the target domain, DOB-based robust tracking control is applied to tackle the modeling gap including the vehicle dynamics errors and the external disturbances such as side forces. We provide simulations validating the capability of the proposed method to achieve zero-shot transfer across multiple driving scenarios such as lane keeping, lane changing and obstacle avoidance.Comment: Published at IEEE ITSC 201

Heißrissvermeidung beim Schweißen von Aluminiumlegierungen mit einem Scheibenlaser

Due to the high beam quality of modern disk lasers slim and deep welds can be produced, which results in coarse columnar grain structures in the weld. Such kind of structures has a high hot cracking susceptibility. Therefore, the aim of this study is to increase the weld-ability of laser welds of aluminum alloys by grain refinement. In order realize grain re-finement, the weld grain structure was investigated depending on Ti/B-contents and weld parameters. Based on this investigation, the influence of grain refinement on hot crack susceptibility was studied via DELTA test. In order to understand the mechanism of hot cracking prevention by grain refinement, an analytical model was developed which de-scribes the influences of the grain structure and solidification parameters on the three main factors, which are the duration of the mush zone, the capillary pressure as well as the permeability of the dendritic network in the melt pool. The model reveals that the hot cracking susceptibility is determined by the combination of these three factors. With this model the hot cracking susceptibility can be quantitatively predicted depending on the grain structure. Thanks to this work, a knowledge base has been created for a controllable increase of weldability by grain refinement

Age of Information of Multi-user Mobile Edge Computing Systems

In this paper, we analyze the average age of information (AoI) and the average peak AoI (PAoI) of a multiuser mobile edge computing (MEC) system where a base station (BS) generates and transmits computation-intensive packets to user equipments (UEs). In this MEC system, we focus on three computing schemes: (i) The local computing scheme where all computational tasks are computed by the local server at the UE, (ii) The edge computing scheme where all computational tasks are computed by the edge server at the BS, and (iii) The partial computing scheme where computational tasks are partially allocated at the edge server and the rest are computed by the local server. Considering exponentially distributed transmission time and computation time and adopting the first come first serve (FCFS) queuing policy, we derive closed-form expressions for the average AoI and average PAoI. To address the complexity of the average AoI expression, we derive simple upper and lower bounds on the average AoI, which allow us to explicitly examine the dependence of the optimal offloading decision on the MEC system parameters. Aided by simulation results, we verify our analysis and illustrate the impact of system parameters on the AoI performance

Tunneling magnetoresistance in Mn2_2Au-based pure antiferromagnetic tunnel junction

Antiferromagnetic (AF) spintronics is merit on ultra-high operator speed and stability in the presence of magnetic field. To fully use the merit, the device should be pure rather than hybrid with ferromagnet or ferrimagnet. For the magnetism in the antiferromagnet is canceled by that of different sublattices, breaking the symmetry in the material can revive the native magnetism, which can be detected by the magnetoresistance (MR) effect. Achieving noticeable MR effect in the pure AF device is diffcult but essential for the AF spintronic applications. Here, we study the tunnel magnetoresistance(TMR) effect in the Nb/Mn$_2$Au/CdO/Mn$_2$Au/Nb pure AF magnetic tunnel junctions (AF-MTJs) based on a first-principle scattering theory. Giant TMRs with order of 1000% are predicted in some symmetric junctions, which is originated from the interfacial resonance tunneling effect related with the k dependent complex band structures of CdO and Mn$_2$Au in companion with the enhanced spin polarization of the interfacial magnetic atoms. The effect of voltage bias and interfacial disorder such as Oxygen vacancy, Manganese vacancy, and Manganese-Cadmium exchanges at Mn2Au/CdO interfaces are studied also. Our studies suggest Nb/Mn$_2$Au/CdO/Mn$_2$Au/Nb AFMTJs promising material for AF spintronic application, and rocksalt CdO a potential symmetry filtering material for spintronic applications

Laboratory measurement of shear strength and related acoustic properties

The general purpose of this research is to pursue the correlationship between acoustic properties and strength properties of sands. Conventional methods for correlating these characteristics rely on in-situ measurements of the wave velocity and shear strength. These measurements are subject to error from contamination by many unknown influences. A combined laboratory acoustic-triaxial testing equipment was developed to study reliably the interrelationship between shear strength and shear wave velocity by using piezoelectric ceramic benders to measure shear wave velocity in the triaxial tests. In processing the wave signals, the Hilbert transform technique was applied to precisely determine the wave propagation time. -- An unified stress-strain model is proposed for predicating sand behavior under loading conditions. It is found that the popular hyperbolic equation is a special case of the new model that can be applied to sands with a wide range of relative densities. -- Shear wave velocity increases with increasing confining pressure but decreases with increasing void ratio. It is found that shear wave velocity increases with increasing axial strain until reaching its peak strength and then drops. The rate of decrease depends on the type of sand and confining pressure. -- The microstructural analyses and experimental results indicate that the shear wave velocity-axial strain relationship follows the same mechanism controlling stress-strain behavior of sands. Therefore the new stress-strain model is modified further according to experimental results to correlate shear wave velocity and shear strength. Unambiguous results in shear wave velocity have been established as a function of stress ratio and axial strain. The comparisons between model and measured data indicate that the proposed equation can describe well wave velocity changes with stress and strain