Performances: Curvature Radius
The short distance between control sectors and the possibility of modifying in realtime this distance allow obtaining a minimum curvature radius of 30 mm. This value corresponds to the resolution of the system, and allows users to render a large range of smooth surfaces.
Concerning the accuracy of the rendering, the possibility to select the best position for the control points by means of the developed control algorithm, ensures the capability to control the elastic deformation of the plastic strip. Indeed, deforming the strip by means of the control sectors placed in particular points (e.g., minimum, maximum or inflection points) ensures the best configuration available for managing the strip behaviour.
The system in charge of managing the control points along transversal plane consists of modules with absolute configuration. These modules can be replicated, and it is possible to decide how many modules to include in the desktop station according to the characteristics of the surface to render.
As already explained, the minimum number of modules required to obtain a properly working interface is equal to three. Therefore, it is possible to adapt the length of the rail and the rank, required to perform the longitudinal translation, so as to obtain the space needed to increase the number of modules. In any case, it can be decided to increase the number of modules in order to obtain two different results: increase the length of the rendered trajectory or/and increase the resolution of the system. Regarding the first case, increasing the rail length and the number of modules, and maintaining similar the nominal distance between the sectors, allows increasing the total length of the trajectory that can be rendered. Otherwise, maintaining the same rail length, while increasing the number of modules, implies that the nominal distance between the modules has to be reduced. This feature increases the resolution of the system (Fig.7.2).
Regarding the maximum number of modules that can be installed, there is not a theoretical limit. The limitation regards technical aspects and in particular: the rail length and the working space of each module. Obviously, if we increase the length too much we will lose the feature of portability, and the resulting interface could be cumbersome to use as a desktop device.
Regarding the working space of the module, if the system is equipped with identical modules, it will be possible to augment the length of the trajectory, while the working space on transversal plane of the whole interface will remain the same. If we consider the working space of the device as a half-cylinder with axis parallel to the rail, increasing the number of modules will allow increasing the height of the cylinder while the radius remains the same.
In order to increase the working space of a single module on the transversal plane, which allows augmenting the working space of the whole device, it has been developed the module so that it is capable to provide the scalability feature. Indeed, the structural components that compose the elements Arm1 and Arm2 are made of commercial profiles, which can be chosen with different dimension.
The servomotors in charge of rotating these elements are able to provide high torque value, which has been purposely over-dimensioned so as to allow the module scalability.
Therefore, as shown in Fig.7.3, each module can be scaled so as to increase its working space. The maximum scalability ratio that can be chosen is 2:1. This value does not depend on the servomotor maximum torque but on the resulting stiffness of the module. Indeed, if the length of the elements is increased over this value, the resulting module will not have the proper level of stiffness that is required.