Home Engineering Tactile Display for Virtual 3D Shape Rendering
Modality with Interval Definition and Variable Distance Between Control Points
The third modality is similar to the second one but the selection of the centre point is made directly by the software. Indeed, the user has to select only the portion of the surface to render and the software selects the position of all the control points
Fig. 6.20 Phase 3 - Servomotors positions
according to the boundary condition (collision avoiding and strip length). These points are placed, when possible, in sensible points, such as relative minimum point, relative maximum point and high values of curvature variation. Figure 6.17 shows two conceptual examples of the control points management for a generic trajectory in the modality with constant distance between control points.
Once the positions of the points are defined, it is possible to calculate the normal vectors to the surface. Figure 6.18 shows an example of the selection of a control point in a relative maximum point and the consequent normal vector.
Leaving the software free to choose all the control points positions, it is possible to obtain the best rendering. Indeed, by placing the control sectors in these points, it will be possible to set the system in the best configuration to control the strip deformation. Figure 6.19 shows the procedure used to manage the control points with the described modality.
Phase 3: Calculation of the Servomotors Positions and Sending of Serial Signals
The coordinates and the torsional and tangential angles of each control point are the output of Phase 2. These data are used as input for Phase 3. This step reads the coordinates and the angles of the control points. By means of the inverse kinematic analysis, it calculates the angular position that each servomotor has to assume in order to perform the rendering (Fig. 6.20).
Fig. 6.21 Control process
After that each angular position is converted from an angular value to the appropriate millisecond value according to the RC PWM communication protocol. Figure6.21 shows the whole control process.
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