Geometric Basics and Calculation Methods for the Design of a Technical Saddle Joint based on Owl Neck Vertebrae

A saddle joint enables the movement of two components relative to each other primarily about two axes of rotation and, to a limited extent, in translational direction. This type of joint is primarily found in nature, for example in the human thumb, in the ossicles and the cervical spine of owls. Motivated by the high degree of the owls’ head mobility, the authors aim to make this high motion potential technically accessible by defining relevant design parameters and developing calculation methods for dimensioning the saddle joint components. First, an abstracted contact geometry model based on the owls’ saddle joints is de-fined. A method for calculating the kinematics of the joint as a function of the previously introduced design parameters of the contact is derived mathematically. Regarding the implementation in a design process, this model is used to calculate the restoring forces required to stabilize the joint parts as well as the actuator torque needed for a specific rotational movement around those axes. Furthermore, the rotational stiffness of a specific joint geometry is calculated as an important design criterion. In summary, the defined contact geometry, the kinematics, and the computable forces serve as basis for designing technical saddle joints in the future

Development and Implementation of a Guideline for the Combination of Additively Manufactured Joint Assemblies with Wire Actuators made of Shape Memory Alloys

Smart Materials actuators in the form of wires made of shape memory alloys in combination with additively manufactured carrier components are used in a wide variety of prototype developments of innovative joint assemblies. This combination is relevant because of the same manufacturing costs of the additively manufactured components, which are independent of the quantity of parts, the free geometric design possibilities as well as the huge energy density of the aforementioned actuator technology. In particular, the focus is on the possibility of appropriately fitting large wire lengths on a compact part volume while taking into account acceptable force losses. Since there is no design guideline for such joint developments, each is individual, which results in unnecessarily long development times and a higher risk of errors. Based on selected in-house and third-party examples, integration possibilities of shape memory alloy wire actuators in additively manufactured carrier components are analysed and transferred into a universally applicable design guideline. These recommendations are brought into the framework of existing design guidelines of the VDI (Verein Deutscher Ingenieure – Association of German Engineers), namely VDI 2206 and VDI 2221 with extensions for additive manufacturing, for a better usability and integrability into existing processes. Finally, this results in a simplified access to the topic of the combination of additive manufacturing and shape memory alloys and a more efficient realisation of such joint developments

Ein Eulenhalsgelenk für effizientere Maschinen

Im Rahmen des Projekts „Ein Eulenhalsgelenk für effizientere Maschinen“ wurden biologische Erkenntnisse der extremen Bewegungsfähigkeit der Eulenhalswirbelsäule gesammelt und analysiert, eine energieeffiziente und ressourcenschonende Aktorik ausgewählt, ein Steuerungskonzept auf Basis einer Bewegungssimulation entwickelt und ein Funktionsmuster in Form eines Gelenkroboterarms aufgebaut sowie evaluiert. Die biologische Datensammlung erfolgte in Zusammenarbeit mit dem Lehrstuhl und Institut für Biologie II der RWTH Aachen und dem Tiergarten Nürnberg. Mit Hilfe der umfassenden biologischen Erkenntnisse entstand eine Abstraktion des biologischen Vorbilds hin zu einem technischen Prototyp. Als Antriebstechnik kommen Drahtaktoren aus Formgedächtnislegierungen (FGL) zum Einsatz, welche sich durch eine extreme Energiedichte [1] auszeichnen. Durch diese enorme Energiedichte kann mit geringem Materialeinsatz eine große Arbeit verrichtet werden. Das Steuerungskonzept des Prototyps basiert auf einer Bewegungssimulation, welche durch den Einsatz einer inversen Kinematik realisiert wird. Damit ist es möglich, alle erreichbaren Positionen des Greifers zu erfassen, anhand verschiedener Erreichbarkeitskarten darzustellen und mögliche Vereinfachungen der Einzelwinkel zwischen den Wirbeln zu ermitteln. Der aufgebaute Prototyp wurde hinsichtlich seiner Funktionsfähigkeit, maximalen Belastbarkeit und Dynamik evaluiert

Enabling Live Data Controlled Manual Assembly Processes by Worker Information System and Nearfield Localization System

AbstractExisting localization solutions cannot be directly integrated into production systems. This article describes a nearfield localization system which can be installed on tools due to its small dimensions. Live data controlled manual assembly processes are enabled. In combination with worker information systems, the manual assembly process can be supported more precisely compared to common systems. The benefits are shown within product-specific assembly scenarios. One benefit is enabling work out of sight (non-visible range) guided through a virtual model on a screen. Error prevention (zero-defect assembly) can be realized by monitoring and matching the actual position to the assembly location. Even without augmented reality devices, comparative 3-D representations of real and virtual world are feasible, supporting employees in mobile workshop with complex repairs. In particular, difficult accessibility can be easily determined when carrying out maintenance work by knowing the complete product structure

Verbesserte Ergonomie durch Mensch-Roboter-Kollaboration als sozio-technisches System

In dieser Veröffentlichung soll untersucht werden, ob vorhandene Methoden aus dem Bereich der sozio-technischen Systeme (STS) genutzt werden können, um Mensch-Roboter-Kollaborationen (MRK) hinsichtlich ihrer Ergonomie zu optimieren. [... aus der Einleitung

Verbesserte Ergonomie durch Mensch-Roboter-Kollaboration als sozio-technisches System

In dieser Veröffentlichung soll untersucht werden, ob vorhandene Methoden aus dem Bereich der sozio-technischen Systeme (STS) genutzt werden können, um Mensch-Roboter-Kollaborationen (MRK) hinsichtlich ihrer Ergonomie zu optimieren. [... aus der Einleitung

Verbesserte Ergonomie durch Mensch-Roboter-Kollaboration als sozio-technisches System

In dieser Veröffentlichung soll untersucht werden, ob vorhandene Methoden aus dem Bereich der sozio-technischen Systeme (STS) genutzt werden können, um Mensch-Roboter-Kollaborationen (MRK) hinsichtlich ihrer Ergonomie zu optimieren. [... aus der Einleitung

Fluid-based Removal of Inner Support Structures Manufactured by Fused Deposition Modeling: An Investigation on Factors of Influence

AbstractAdditive manufacturing is growing in importance in industrial environments. In this context, a holistic process control is required. The process steps in additive manufacturing are generally data preparation, production, and post-production. If there are overhanging geometric elements in the components to be manufactured, they must be supported. The type of support is technology-specific. In fused deposition modeling, a support structure is simultaneously built to accommodate such geometric elements. The support structure may be mechanically removed in post-processing or in a bath of alkaline solution. For inner support cores with complex geometries, a removal in a liquid bath is preferred for reasons of accessibility. However, sufficient contact with the liquid solution is not always given. Consequently, the removal in these cases is not guaranteed. Information about the duration and quality of removal is currently not precisely quantified. An approach to systemize this process is presented in this paper. Therefore potential factors of influence are listed. Selected parameters and their effects were analyzed in experimental trials. The experiments were designed around removing the support material using injection nozzles. The experimental results show the significant impact of pressure, flow rate, and size of contact area on duration and quality of removal

Biomimetic Spider Leg Joints: A Review from Biomechanical Research to Compliant Robotic Actuators

Due to their inherent compliance, soft actuated joints are becoming increasingly important for robotic applications, especially when human-robot-interactions are expected. Several of these flexible actuators are inspired by biological models. One perfect showpiece for biomimetic robots is the spider leg, because it combines lightweight design and graceful movements with powerful and dynamic actuation. Building on this motivation, the review article focuses on compliant robotic joints inspired by the function principle of the spider leg. The mechanism is introduced by an overview of existing biological and biomechanical research. Thereupon a classification of robots that are bio-inspired by spider joints is presented. Based on this, the biomimetic robot applications referring to the spider principle are identified and discussed