In the idea of always improving the comfort and operational capabilities of our suit-testers, we are now developing a project dealing with glove designing. Wearing a glove of any type reduces the sensations you feel, especially for our 3 layers’ spacesuit gloves. The first step is to evaluate our gloves in order to point out the major issues impeding tactility and to get estimators of sensibility.

These pilot tests are described below:

Protocol

Several tasks have been accomplished to conduct these tests: first of all material selection and gathering, here is a list of what is needed before beginning:

• Test plates : 2 sets of 5 plates, patterns from 1 mm to 5 mm
• Earplugs and eye masks
• Computer : to record the results
• Weighing machine
• Excel spreadsheet/questionnaire ready for the subject
• Entire spacesuit glove (3 layers)
• Repositionable tape

Another task was to define the protocol and the sheets to record data, the test protocol lies below:

• we have 2 sets of 5 plates with different patterns from 1 mm to 5 mm (a 5 mm pattern plate as an example below)
• they are randomly presented in sequence of 2 plates each time to the subject
• to the question : “are the plate identical ?” The subject has to answer Yes or No according to his perception.

5 mm pattern plate (c) OEWF (Marc Rodiguez)

Here is an example of a random sequence as it will be presented to the subject:

• we assign a score to each test depending on the performance (e.g. : {2;5} is easier to discriminate than {1;2}) (see performance valuation § for complete explanations)

Test bench while testing (c) OEWF (Marc Rodriguez)

The test plates were printed with the 3D printer in the lab, they are made of ABS plastic, and the problem encountered there was the resolution of the printer: we were not able to print patterns of less than 1 mm. If you know that the hand can easily detect irregularities of 0.2 mm above a surface, it is easily imaginable that – even through glove – patterns of 1 mm can be detected. This issue has been balanced by limiting the contact strength between the subject’s finger and the plate at 500 g. This limit provides a threshold of perception reflected in the answers, allowing us to compare the performance of the subjects.

Performance valuation
There is one performance mark for each combination of plates (Yes and No scales are different). The question answered is: “are the plates identical?” The more the result is close to “1”, the more the test is conclusive. As well, we can observe that the {1;2} test gives “1” if the answer is No because plates are very difficult to discriminate. Moreover, if someone answers No to a test with identical plates, he gets “0”. After that all the intermediate marks are evenly divided: e.g. for “Answer Yes” {4;5} gives “0.75” while {1;4} give “0.25”.

Test bench with spacesuit glove : two identical 3 mm pattern plates on the balance (c) OEWF (Marc Rodriguez)

Several aims
The first aim as said before is to value the current gloves and to focus on points of improvement. The other hidden aim is to train our suit-testers with the training programs provided to blind people to observe eventual changes in their results. If so, that could be another kind of training added to the one already set up for EVAs.

Results
From the first data we have gathered with this pilot test, we can say that blind people have results significantly above “normal vision” people: On the one hand, this can be explained by the effect of compensation occurring in the blind people cortex, allowing them to get more tactile sensitivity (use of the vision area to perceive tactile stimulus). On the other hand, and we believe it has an important effect, the training they followed in schools for blind people especially for Braille reading and texture recognition.
Concerning the glove design, we have encountered various causes that can impede tactility (independently of the layers’ thickness) : the fitting first of all as the gloves are not made to measure, the sewing at the fingertip also makes hard edges avoiding contact between finger pulp and the glove.

Conclusion
These are just the first tests of a long series but we are optimistic to prove the effect of a tactile training program tailored for suit-testers that would increase naturally their capabilities. This is a type of human centered development that can provide great results without any technology added: Combining a tailored human-factors training with an improved tactility – optimized surface of the gloves – maybe one day can make the difference in selecting the rock sample indicating the presence of extinct life on Mars?

Dieser Artikel ist auch verfügbar auf: German