Tobias Strauss

Making Bertha Drive?An Autonomous Journey on a Historic Route

125 years after Bertha Benz completed the first overland journey in automotive history, the Mercedes Benz S-Class S 500 INTELLIGENT DRIVE followed the same route from Mannheim to Pforzheim, Germany, in fully autonomous manner. The autonomous vehicle was equipped with close-to-production sensor hardware and relied solely on vision and radar sensors in combination with accurate digital maps to obtain a comprehensive understanding of complex traffic situations. The historic Bertha Benz Memorial Route is particularly challenging for autonomous driving. The course taken by the autonomous vehicle had a length of 103 km and covered rural roads, 23 small villages and major cities (e.g. downtown Mannheim and Heidelberg). The route posed a large variety of difficult traffic scenarios including intersections with and without traffic lights, roundabouts, and narrow passages with oncoming traffic. This paper gives an overview of the autonomous vehicle and presents details on vision and radar-based perception, digital road maps and video-based self-localization, as well as motion planning in complex urban scenarios.

Local Residual Stress Distribution at the Tooth Root Surface of a Broached Steel Component

Broaching is an important technique for creating tooth structures in mechanical components. In the present work, the effects of the broaching process on the material state in the near surface region at the root of the tooth was analyzed. The studies were carried out on broached plates made from case hardening steel SAE 5120. The cutting speed and machining condition (cooling lubricant, dry machining) were varied. During broaching with a TiAlN coated tool the cutting forces were monitored. Subsequently, the local residual stresses at the root of the tooth were determined using X-ray diffraction. Further, surface roughness and micro hardness measurements as well as microstructure analysis complement the results. The results indicate that cutting forces have a high influence on the development of the residual stress state at the machined surface whereas no significant effect on changes in surface hardness and microstructure could be observed. Dry cutting with relatively high cutting speeds (≥ 30m/min) result in low cutting forces and hence in high tensile residual stresses in broaching direction.

Making Bertha Cooperate–Team AnnieWAY’s Entry to the 2016 Grand Cooperative Driving Challenge

This paper presents the concepts and methods utilized by Team AnnieWAY for the 2016 Grand Cooperative Driving Challenge. The paper introduces the automated vehicle BerthaOne. The vehicle, even though being based on the Bertha platform, distinguishes itself from its siblings by its software modules and algorithms. We, therefore, describe its system architecture and algorithms for perception, cooperation and motion planning. In Particular, we present a motion planner that plans different maneuvers flexibly by augmenting the cost function with situation specific cost terms. We subsequently describe the requirements of the 2016 GCDC and evaluate our performance during the competition.

Photometric laser scanner to camera calibration for low resolution sensors

In modern automated systems the usage of sensors with orthogonal measurement principles is indispensable for assuring a redundant system. The combination of laser scanners and cameras is particularly prevalent. To profit from the potential of fusing information from these sensors, the basic step is sensor registration. State of the art cross-calibration methods for laser scanners and cameras establish geometric correspondences for example by detecting checker-boards in size and form. However these approaches suffer from ambivalent features and are only usable if the laser scanner has a high scanning density. Therefore, we present a reconstruction-free and vision-based extrinsic calibration algorithm with distinct features, which was developed with special focus on low-density laser scanners and high measurement noise. Moreover, we contribute an evaluation methodology demonstrating the capability of our approach. Along with this paper, we publish the associated code.

Local Residual Stress Depth Distribution in the Inner Gearing of a Case Hardened Sliding Collar

With respect to residual stress analysis the inner gearing of an automotive sliding collar is a component with a challenging, complex geometry. The accessibility of the tooth root does not exist for conventional measuring approaches. However, the process steps like e.g. broaching and case hardening induce characteristic residual stress distributions, which must be known for the valuation of the mechanical integrity of the parts. For lab X-ray stress analysis approaches according to the sin2ψ-method [1] the ring like structure must be sectioned, which affects the process induced residual stress state. The tooth root is rather small, which further leads to shadowing effects during tilting of the sample. Standard mechanical approaches like incremental hole drilling can be excluded due to the narrow tooth root. Local neutron diffraction residual stress analysis in the tooth root by means of neutron through surface strain scanning at the STRESS-SPEC instrument at the research reactor FRM II, Garching (Germany) was successfully carried out for the inner gearing. A measuring and evaluation strategy is proposed, where special attention is paid to the compensation of the surface effect due to the incomplete immersion of the nominal gauge volume during through surface scanning and to the local variation of the D0-value as a consequence of the case hardening process.

Kalibrierung von Multi-Kamera-Systemen - Kombinierte Schätzung von intrinsischem Abbildungsverhalten der einzelnen Kameras und deren relativer Lage zueinander ohne Erfordernis sich überlappender Sichtbereiche

This thesis presents a method for the combined intrinsic and extrinsic calibration of multi camera systems including cameras with fisheye lenses and cameras with non-overlapping fields of view. A temporal movement of a calibration target consisting of a fixed arrangement of multiple checkerboard patterns is captured and used as measurement. The process of camera calibration is formulated as a full bundle adjustment.