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Scientific and commercial data is often incomplete. Recovery of the missing information is an important pre‐processing step in data analysis. Real‐world data can in many cases be represented as a superposition of two or more different types of structures. For example, images may often be decomposed into texture and cartoon‐like components. When incomplete data comes from a distribution well‐represented...
We consider nonholonomic mobile robots. Since the system is finite time controllable, it is stabilizable by a receding horizon control scheme with purely quadratic stage costs if an infinite optimization horizon is employed. However, due to the so called short‐sightedness of model predictive control, these stability properties are not preserved if the control problem is only optimized on a truncated...
In this paper the idea of design exploration in the context of structural design sensitivity analysis considering elastoplastic material behaviour is outlined. Sensitivity information involves the influence of history dependent material behaviour and is obtained analytically by means of a variational approach. Applying singular value decomposition (SVD) to response sensitivities provides deep insight...
This work outlines a rigorous variational‐based framework for the phase field modeling of fracture in isotropic and anisotropic porous solids undergoing small elastic but large plastic deformations. It extends the recent work [1] to a formulation of porous plasticity with particulate microstructures characterized by spherical pores or by ellipsoidal voids, which additionally undergo a change in size...
We propose a concept for the comprehensive optimization of load bearing structures. The main idea is to decompose the optimization task. First, we use a phase field model to evolve the topology as basic design. The parameters of this process are the filling level of the design domain and the tendency to nucleate more or less holes. Second, we use an interface to set up a subsequent structural model,...
We consider the computation of the ℒ∞‐norm for a general class of ℒ∞‐functions and focus on the case where the function is represented in terms of large‐scale matrix‐valued factors. We propose a subspace projection method to obtain reduced approximations of this function by interpolation techniques. The ℒ∞‐norms are computed for the resulting reduced functions, then the subspaces are refined by means...
The hydrodynamics of rising air bubbles in water filled bubble columns are examined using a transient numerical model following the Euler‐Euler method. In this particular case the bubble‐size distribution is assumed to be mono‐disperse and the influence of this assumption on the specific mass‐transfer area is discussed. Additionally, the influence of the bubble size is discussed with regard to the...
The human thumb possesses joint axes with intricate descriptions, which enable the thumb to perform complex motions like opposition. To validate a thumb multibody model kinematically, we firstly study the difference in the volumes of the thumb tip workspace for the maximum range of motion (RoM) and the grasp RoM. We compare the volume difference for five models (with same joint designs but different...
In an aging society where the number of joint replacements rises, it is important to also increase the longevity of implants. In particular hip implants have a lifetime of at most 15 years. This derives primarily from pain due to implant migration, wear, inflammation, and dislocation, which is affected by the positioning of the implant during the surgery. Current joint replacement practice uses 2D...
For the simulation of the mechanical behaviour of components, an appropriate material model and a good experimental data base to identify the material parameters are needed. Due to the fact that the typically used standard test specimen do not include any inhomogeneous effects, an alternative component‐oriented specimen is introduced. To improve the identification, a design of experiments strategy...
Time‐optimal path following, i.e. moving a robot's end‐effector optimally along a specified geometric path, is a very important and well discussed problem in robotics. Nevertheless, most of the existing approaches concerning this topic neglect the speed dependency of torque constraints. The present paper presents a method for taking such constraints into account within a dynamic programming approach...
Due to their low weight robots with flexible links are ideal candidates for use in dynamically demanding applications. Since the main goal of the robot control is to achieve precise positioning, the damping of oscillations due to low stiffness is imperative. Furthermore classical PD motor position control is insufficient for vibration damping. This paper presents an approach using an eye‐in‐hand camera...
In this contribution, we investigate the accuracy of surrogate models for fuzzy systems. Within a virtual tolerance analysis, unknown uncertainties are considered by fuzzy numbers. These fuzzy numbers consist of higher‐dimensional intervals, where each interval is assigned a membership value. To reproduce fuzzy numbers correctly, a large number of system evaluations is needed. Instead of evaluating...
Rubber‐toughened thermoplastic polymers such as PC/ABS blends exhibit a pronounced plastic dilatancy in their overall deformation behavior which results primarily from damage mechanisms in the ABS phase while PC behaves plastically incompressible, e.g. [1]. In this contribution, two commercial PC/ABS blends of different composition and morphology are approximated through appropriate unit cell models...
In this contribution, the phenomenological material modelling of a polyurethane based adhesive including the curing process is considered. First, the underlying chemical process is regarded. To this end, differential scanning calorimetry experiments were carried out, models for the reaction heat and a so called degree of cure were formulated, and the corresponding model parameters were identified...
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