Добавил:
ivanov666
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:The design of the exoskeleton. Monograph
.pdf
101
The section will give some basic tests on details and typical, basic loads for
them.
6.2.7. Hip
Description: the Item for the purpose of replacing the thigh of a
person. Therefore, according to the previously described loads while
performing different exercises for legs, designed item needs to at least
satisfy us of the strength and deflection at corresponding loads. I have
previously described in the formation of the customs Union, the most
complex and Laden with movement to develop the mechanics will be the
squat. For this exercise, the load on the link is maximized.
Model 1
Material: Steel 30.
Yield point, MPa: 320
Load 340 N
Weight:0.695 kg
Results:
• Factor of safety: 0.62
• Maximum deflection, mm: 3.34
It was assumed that the link of such parameters would more than
satisfy the design, so even it was facilitated by drilling the material.
However, after testing the part in the SolidWorks system, it became
apparent that the link required major improvements to be able to work
with such efforts.
Model 2
Material: Steel 30.
The boundary yield stress, 320 MPa:
Load 340 N
Weight: 0.873 kg
The weakest places in the previous sample were the holes, so it was
decided to get rid of the holes in the weak zone, and the parts that were
previously fixed by bolt connections, are now fixed by welding.
102
Results:
• Factor of safety: 2.54 • Maximum deflection, mm: 0.71
Moving can be considered within acceptable limits as the factor of
safety, but in the process of developing a complete design, it became clear
that such a detail will not be sufficiently technological in the Assembly of
the structure and inconvenient for integration into its composition of new
elements. Therefore was developed the same detail settings but more
technologically advanced.
Model 3
It was decided to develop this part as a welded construction of sheet
elements that were cut by laser. The advantage of such a part is that it is
possible to apply virtually any material from existing in the sheet form and
the final part can get virtually any geometric shape of the flat parts, which
makes it possible to achieve the maximum possible results from the design
at a constant weight. Standard profiles such an advantage of course can
not boast , as are made of a narrow range of metals and have a relatively
narrow assortment.
Material: Steel 30.
Yield point, MPa: 320
Load 340Н Weight: 1.2345 kg
Results:
• Factor of safety: 2.27 • Maximum deflection, mm: 1.26
As a result, regarding this detail, we can say that this design is quite
technological and simple today. As can be seen from the design, the part
can be welded to a number of elements, mainly cut on the laser, which
allows the use of a wide range of materials while not being limited to the
shape of the flat elements of the part. Also, this embodiment allows
considerably easier in the future to integrate into the part holes for
mounting of various fixtures and other fixtures, and the like.
103
6.2.8. Litka. Design of components
The design consists of several components that need to be tested
separately.
Link 1
Description: the Part serves as a transition link between the knee joint
and the joint of the foot rotation relative to the axis of the Shin. The part,
in particular the mounting holes are designed for a constant variable
cyclic load.
Model 1
Material: Steel 30.
Yield point, MPa: 320
Load 340 N
Weight:0.078 kg
Results:
• Factor of safety: 0.22 • Maximum deflection, mm: 3.2
As in the previous part, it is not necessary to facilitate the item until
there is no certainty that it is at least in the initial, light condition provides
strength. The test result showed multiple zones that do not satisfy the
tensile strength and have a safety factor of 0.219. As you can see, the main
voltage concentrators are holes.
Model 2
Material: Steel 30.
The boundary yield stress, 320 MPa:
Load 340 N
Weight: 0.11 kg
Results:
• Factor of safety: 1.9
• Maximum deflection, mm: 0.52
After several modifications, the result was gradually obtained, which
satisfies the strength and strength parameters. However, in further tests,
it was revealed that the hole for fastening the hinge shaft to the knees will
not be able to work with those loads regardless of its shape. In addition, a
104
complex form of opening would entail a separate technological complexity,
and therefore, at least additional costs, There was a need for a conceptually
different approach.
Model 3. Test 1
Material: Steel 30.
Yield point, MPa: 320
Load 340 N
Weight: 0.172 kg
Results:
• Factor of safety: 3.171
• Maximum deflection, mm: 0.224
In the case where the load acts on the part that way, the strength
conditions finally satisfied us, however, it should be remembered that the
load, depending on the actions performed by the system may have a
different character, so this effect should also be checked.
Model 3. Test 2
Material: Steel 30.
Yield point, MPa: 320
Load: M kr=170 Nm
Weight: 0.172 kg
Results:
• Factor of safety: 0.43
• Maximum deflection, mm: 0.515
According to the test results, it was found that under such loads the
part has an insufficient factor of safety, so it is recommended to replace
the part material with a material with at least twice the yield strength.
The shaft of the hinge of the knee
For design reasons, it was decided to test this part only after obtaining
acceptable dependent parts. As a result, the obtained part was tested with
the following results.
Material: 45H Steel.
Yield point, 835 MPa:
Load: 170nm torque.
105
Weight: 0.087 kg
Results:
• Factor of safety: 2
• Maximum deflection, mm: 0.015
The shaft of the hinge of the foot rotation relative to the axis of the
Shin
Material: 50X.
Yield point, 1650 MPa:
Load 340 N at a distance of 300mm from the edge of the part.
Weight:0.03 kg.
The hinge shaft has a minimum safety factor of 0.3 and displacement
by force up to 0.55 mm, which makes you think about a different approach
to the design. This does not mean that this design and its parts are poorly
designed and not viable, but only that such a design can be applied to less
loaded areas.
Results:
• Factor of safety: 0.31
• Maximum deflection, mm: 0.55
Calf link 2
The next task was to choose the design of caviar, which would satisfy
us not only in strength but also in weight.
Model 1
Material: Steel 30.
Yield point, MPa: 320
Load 340 N
Weight: 0.27 kg
Results:
• Factor of safety: 0.615 • Maximum deflection, mm: 4.59
However, this part, which was created before the establishment of a
clear TK and was unsatisfactory for this development both for the
deflection and the factor of safety, so a long selection of the necessary
design was carried out as this task requires not only the strength, but also
the minimum own weight.
106
Model 2
The result was this part that performs aligned as seen. The shaft of the
foot hinge and the flange for the hook of the springs of the passive foot
stabilization system are present on the designed Lanka. At the same time,
the difference in weight compared to the first sample is 115 grams, but a
number of elements have already been integrated into the sample, which
would need to be additionally fixed to the first sample.
Material: Steel 30.
The boundary yield stress, 320 MPa:
Load 340 N
Weight:0.398
Results:
• Factor of safety: 1.79
• Maximum deflection, mm: 1.76
Foot
Model 1
The first embodiment was the execution of the foot, which after
clarification of the vehicle was obviously unacceptable.
A long experimental research work was also carried out on the
modeling of the foot to identify the design that will meet the necessary
parameters and have the least weight. Let me remind you that the goal is
to create an integrated system that is able to return the ability to walk even
those who have no legs at all.
Model 2
This design was close to the required parameters, but it had too much
weight with its mechanical parameters.
Material: Steel 30.
Yield point, MPa: 320
Load 340 N
Weight: 0.573 kg
Results:
• Factor of safety: 0.278
• Maximum deflection, mm: 6
107
Model 3
As a result, the following construction was accepted as permissible.
Material: Steel 30.
Yield point, MPa: 320
Load: 550 N
Weight: 0.49 kg.
Results:
• Factor of safety: 1.3
• Maximum deflection, mm: 1.56
Conclusions: As a result of the search work, a foot model was found
that will meet the needs of the development, but it should be understood
that in the case of rehabilitation equipment, an individual approach is
needed, since for example such a foot model can be used to work with any
patients, but in the case of the absence of the patient's legs, from a
technical point of view, it will be more reasonable to perform a symmetrical
design of the foot, and for a patient with existing feet, such strength of this
part will be excessive, as the stop user will have to add to the detail and the
actual safety factor in the process of operation will be significantly higher.
Therefore, it is advisable to take an individual approach to each individual
case, because only in this way it will be possible to get the most balanced
design that will not have controversial compromise solutions.
Summary
Therefore, the angles of rotation of the foot relative to the horizontal
15;0;20 degrees, respectively, the extreme upper position, horizontal and
extreme lower.
In the equilibrium position the foot is in the lowermost position. The
magnitude of the impact of the support on the foot in a precise contact
region of the surface of the foot sometimes: 550Н . In accordance with such
force foot will try to raise user conditional support "on tiptoes."
Thus, with these parameters and taking into account the geometry of
the parts made, it is necessary to calculate the suitable springs. To
108
implement the calculation, use the calculation scheme. The calculation will
be carried out in the MathCad system.
Based on these results, we can decide whether to further model the
springs or change some parameters of the structure itself. For example,
consider the increase in the levers on the foot, as the result of the
calculation we see that the spring №2 works with sufficiently large forces,
which can change even a small change in some sizes.
In particular, in the subsequent design of springs, you can use the
Autodesk Inventor computer-aided design package.
109
7. SPECIAL SECURITY ISSUES
7.1. International standard ISO 13482:2014
A large number of versions and various designs of exoskeletons
created to date and developed for the future, necessitates the introduction
of their classification based on the most characteristic features [12].
Consider the classification of exoskeletons by application:
1. Exoskeletons for extreme applications. These include
exoskeletons for military use and exoskeletons for use in the prevention
and elimination of emergency situations.
The advantages of exoskeletons of this application are the possibility
of their use not only to improve the security of the fighter on the battlefield,
but also to improve the whole complex of its characteristics. As well as
opportunities for the application of exoskeletons in the rubble is heavy
machinery that will leave the maximum chance for survival save.
The main disadvantages of exoskeletons for extreme applications are
due to the fact that they do not completely repeat the biomechanics of
man, thereby imposing significant restrictions on his movements.
An example of an exoskeleton related to this area is shown in figure
4.1.
1. Exoskeletons for civil applications. These include mainly industrial and
medical exoskeletons.
110
Figure 7.1 – Prototype of the exoskeleton Hercule
It should be noted the following advantages of the second exoskeleton
this area is considered as the ability to greatly facilitate the hard physical
labor of workers in the industry and construction industry, the ability in
some conditions to successfully replace heavy construction machinery,
lifting machinery and mechanisms. And also the fact that the use of
exoskeletons in medicine can not only accelerate the rehabilitation of
patients, but also to increase the chances of restoring the mobility of
patients with problems of the musculoskeletal system. Despite these
advantages, it is necessary to pay attention to the shortcomings, namely
the lack of research on the profitability of the use of exoskeletons in
Соседние файлы в предмете [НЕСОРТИРОВАННОЕ]