Cellular solids form the basis of many biological and engineering structures. Most models use the relative density and the mechanical properties of the bulk material as the main parameter for the prediction of the mechanical properties of such structures. In this work the influence of the architecture of periodic cellular solids on the mechanical properties is investigated numerically and experimentally.Using computer aided design, structures with 8x8x8 base cells are designed and fabricated. The physical prototypes which are tested experimentally are made from thermosetting and thermoplastic polymers by employing Rapid Prototyping (RP) techniques. Various RP techniques are compared regarding their suitability for the fabrication of cellular materials.For numerical simulation of the cellular structures, linear Finite Element analysis is employed. Three-dimensional models are set up using higher order beam elements. In a first step, the structure is treated as an infinite medium and homogenization via a 'periodic micro-field approach' is used. The entire elastic tensors for different relative densities are evaluated, from which the directional dependencies of the Young's moduli are derived. In a second step, simulations of finite structures are performed for direct comparison with experiments. Samples consisting of several basic cells are modeled which leads to a better correspondence to the experimental setup. Finite structures of different numbers of cells are modeled to study the influence of the sample size.The experimental and numerical results correspond very well and form a consistent picture of the problem. The multi-disciplinary approach leads to a comprehensive view of effects which govern the mechanical behaviour of the investigated cellular structures. RAPID PROTOTYPING OF CELLULAR MATERIALSRapid Prototyping (RP) offers the possibility to fabricate cellular structures with defined internal and external geometry [1]. Furthermore, recently developed techniques enable the fabrication of complex structures with very small feature resolution. Microstereolithography for instance enables the user to fabricate parts with feature resolutions in the range of 5-10 µm [2,3]. In the course of this work, RP techniques have been used to fabricate polymeric cellular structures whose mechanical properties (strength, stiffness) were investigated experimentally.Cellular structures exhibit multiple undercut features. The utilized process must be able to shape such features. In the course of this work, two RP processes were utilized: Stereolithography (SLA) and selective laser sintering (SLS) [4]. SLA offers excellent feature resolution. Problems might arise with structures which cannot be built without support. Due to the cellular structure of the fabricated parts, support structures cannot be removed mechanically. The unit cells of the Mat. Res. Soc. Symp. Proc. Vol. 823

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The Genium\ Bionic Prosthetic Knee (Genium) offers the amputee features and modalities for ambulation that had not been available in prosthetic knee joints before. A biomechanical pilot study revealed that, compared with the C-Leg\, the Genium permits new activities such as climbing stairs and stepping over obstacles step over step. Further improvement in safety and close approximation of movements to those of nonamputated subjects were observed with the Genium Knee. Rehabilitation aims at the best possible restoration of independence and participation of the patient in family, business, and social life. Therefore, this study with 10 unilateral transfemoral amputees (Medicare Functional Classification level 3 and 4) investigated whether the Genium Knee is able to further improve the perceived safety and difficulty of 45 activities of daily living as compared with the C-Leg. Results show that after 3 months of Genium use, it could be shown that perceived safety improved in 27 activities (60%) and perceived difficulty improved in 24 activities (53%). Improvements were seen in the categories of Family and Social Life as well as Mobility and Transportation. These findings create the basis for further improvement of independence and participation of amputees in family, business, and social life by using the Genium Bionic Prosthetic Knee. (J Prosthet Orthot. 2013;25:110Y117.) KEY INDEXING TERMS: microprocessor-controlled knee, activities of daily living, Genium, C-Leg, transfemoral amputees

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An algorithm for dynamic trajectory generation employing numerical multi-objective optimisation is presented. The crucial innovations are the description of the trajectory through velocity and curvature on the one hand and the restriction of the otherwise infinite function space to a set of basis functions on the other hand. A number of boundary conditions and inequality constraints ensuring the feasibility of the planned trajectory for real vehicles are adhered to. This algorithm is embedded in a rudimentary map-building scheme and an efficient path-planning concept working with incomplete environment information. The performance of the system is demonstrated by application to randomly generated environments.