TOWARDS THE DESIGN OF KRESLING TOWER ORIGAMI AS A COMPLIANT BUILDING BLOCK

In this paper, the use of the Kresling tower origami as a building block for compliant mechanism design is considered. Design tools to help building systems using this origami are introduced. First, a model which can describe the tower kinematics during its deployment is introduced. This model is exploited to link the origami pattern geometry to the main Kresling tower characteristics which include the position of stable configurations, the helical motion and the configuration of panels during the tower deployment. Second, a local modification of fold geometry is introduced to adjust the tower stiffness. This aims at modifying the actuation force without affecting the kinematics and consists in the removal of material on the fold line where constraints are concentrated during the folding. Experimental evaluation is conducted to verify the relevance of the proposed models and the impact of fold line modification. As a result, the design relationships derived from the model are precise enough for the synthesis, with a global relative mean error around 0.8% for the prediction of the helical motion, and 3.1% for the assessment of stable configurations. The capacity to significantly modify the actuation force thanks to the fold line modification is also observed with a reduction of about 73% of the maximal force to switch between two stable configurations.

The Hanging Drape: a Vertex Analogy

We present a novel, rigidly folding vertex inspired by the shape of the simplest hanging drape. Fold lines in the vertex correspond to pleats and ridges in the drape, and are symmetrically arranged to enable synchronised at folding of facet pairs. We calculate the folded rotation angles exactly using a spherical image specialised for inextensible vertex folding. We show that the vertex shape is bounded by a pair of conical surfaces whose apex semi-angles directly correspond with fold-line rotations, which expresses a geometrical equivalence between the external shape and internal folding motion of the vertex. We discuss how the vertex viz. drape perform as a novel type of conical defect based on its spherical image topography; and we highlight the meaning of bistable behaviour for the vertex, in analytical- and practical terms.

Finite Element Analysis and Thick-Panel Clash Behaviour of Steel Fold-Lines

The structural and mechanical behaviours of most origami-inspired or folded structures is strongly dependent upon the mechanical behaviours of their constituent crease lines. Characterisation of the rotational behaviours of the steel hinges is therefore a critical step in the analysis of origami-inspired steel structures. This paper will present a numerical modelling approach for simulating the rotational response of digitally-fabricated steel hinges, over a large rotation range from 0° up to 170°. Numerical response predictions are verified against published experimental results, over a range of sheet thicknesses and fold line parameters. Models are then used to give insight into observed thick-panel clash behaviours and fold-line localised strap mechanics. The developed numerical modelling procedure provides a convenient analysis method for rapid prediction of steel hinge behaviour.

Effects of Visual Active Deceleration Devices on Controlling Vehicle Speeds in a Long Downhill Tunnel of an Expressway

Because the inside of a road tunnel is a closed strip, the driving environment changes suddenly at the tunnel entrance and exit, which is why accidents occur more frequently in tunnels than elsewhere. Based on visual psychology, reverse-perspective-illusion deceleration lines (RPIDLs) and visual-intervention deceleration devices (VIDDs) were designed to control vehicle speeds near the entrance and in the middle of a tunnel, respectively. Then, to assess the speed-controlling performance of the RPIDLs and VIDDs for vehicles in a long downhill tunnel, laser velocimeters were used to measure the vehicle speeds at different observation points in the tunnel before and after implementing the RPIDLs and VIDDs. The results show that the RPIDLs and VIDDs decreased the average vehicle speed and controlled its dispersion effectively. The 60 m RPIDLs improved the traffic safety in the tunnel without lessening the passing ability therein. The slash-line VIDD had no obvious effect on the maximum vehicle speeds in the middle of the tunnel. Both the 90° fold-line VIDD and the four-yellow–four-white VIDD decreased the maximum vehicle speeds significantly. The 60 m RPIDLs and the 90° fold-line VIDD gave the best deceleration effect on vehicles near the entrance and in the middle of the tunnel, respectively, and controlled the average speed and its dispersion effectively.