In the framework of the VERITAS FP VII project we built an interactive panel. The system includes an LCD and force sensors. With the system it is possible to measure the ability of a subject to interact with images and instructions appearing on the monitor.
By storing and processing the data acquired during the experiments (time, position and force) it is possible to estimate the position, speed and force of the finger’s movements, estimate its accuracy and analyze the frequency content via FFT.
Several tests and measurements can be achieved. In the following some examples.
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| This is an example of a cognitive test.
A matrix of buttons is shown, the user must press the suggested one as fast as possible. |
This is a test to achieve the human Transfer Function. The subject tries to follow the vertical line that moves horizontally.
The human TF was modeled as a delay plus a first order system. Whith the sequence data it was estimated the following parameters: |
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| A screen shot of the Fitts law test. | The result of the Fitts test.
The graph gives the movement time as a function of an index of difficulty. To see a video of our system: http://www.youtube.com/watch?v=2Tm8Hggba_w An interesting video explaining the phylosophy of Fitts law: |
Beside the screen shot of a test able to quantify the subject ability to control simultaneously force and trajectory.
The circle diameter is proportional to the exerted force and must be keeped of the same size as the path gray stripe that in this case is an horizontal segment.
Deviation in position, velocity and force are acquired together with its FFT that for example allows to estimate tremor.
The result of a force control sequence and its FFT.
During the sequence a tremor was superimposed to the motion. The armonic at 4.8 Hz is due to that.
Vertical deviation as a function of time and its FFT. The tremor is more evident on this parameter.