Electronics for Digital Clay
The electrical interface will not be discussed in detail for lack of space. Following figure gives the general layout and complexity however. Suffice it to say that there are numerous challenges to interface a large array of sensors with minimum distortion. For more information, please refer to the related publicaitons at the bottom of this page.
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General Layout of the Electronics |
Picture of Part of the Electronic System |
Surface Refresh Methods for FMD
Similar to the LED array using Matrix Drive method, Fluidic Matrix Drive based hydraulic actuator array also works on a row and column matching method. Three array refresh methods are investigated and listed as following
One-time Refresh Method
[Illustration Video]Actuators are controlled to reach their final positions (determined by the surface matrix) row by row and in one step. One-time refresh method is the simplest surface refresh method, but the visual effect is bad (for Digital Clay as a human machine interface) due to obvious discontinuous movement of the pin-rods.
Gradual Refresh Method
[Illustration Video]A solution to make the surface refresh smoother is gradually achieving the final surface through several intermediate surfaces. The increment of each intermediate surface is a fraction of the final surface. The more intermediate surfaces are used, the smother the surface generation process is, but the longer time it takes. The excessive time is spent on the refresh settling processes. For the actuator array constructed in this work, the refresh settling time is around 50~100 ms.
Approximation Gradual Refresh Method
[Illustration Video]One-time refresh method and gradual refresh method are essentially the same: row refresh are processed one after another. For the approximation gradual refresh method, the whole surface may be refreshed at the same time. The biggest advantage is that the time used is much shorter than the other two refresh methods and the visiual effect is good..
The intermediate surfaces used in this method usually are not proportional to the final surface, but the superposition of these intermediate surfaces yields the final surface. By this approach, the total refreshing time can be reduced and a gradually changed surface can be achieved. The problem foreseen in this method is the decomposition of the desired surface matrix into intermediate surface matrices. The solutions to the problem will be left for future research.
Dynamic Computing Resource Allocation
Haptic interaction between the user and Digital Clay can comsume a big amount of computing resource. This problem can be releaved by following method and shown in the figure right side. Define two display methods: 1) passive display, if there is no interaction between the user the Digital Clay, and 2) active display, if the user contacts the working surface and the Digital Clay needs to provide haptic interface. During the passive display, the working surface is refreshed by the refresh coordinator. However, under most circumstances, Digital Clay works under the active display. If the user contacts the Digital Clay, most of the cells still operates under passive display; only the cells in a small area will work in the active display. That is because the area the user hands have limited area (< 0.04 m2) compared with that of the cell array (0.5~2 m2) The surface level control frequently monitors the pressure of each actuator. Once a pressure change is detected that is due to the user contacting the actuator, that actuator will be defined as the hot spot. When a hot spot is defined, the surface level controller will define a hot area including the hot spot and its neighboring actuators. Then the surface level controller passes the hot spot and the hot area information to the hot area processor, halts the surface refresh coordinator and enables the hot area processor. |
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Example of camera artifact for resolution evaluation