Mechanical design and analysis of a robotic human hand for prosthesis

مقدم أطروحة جامعية

Bakhy, Sadiq Husayn

مشرف أطروحة جامعية

Nacy, Sumr M.
Hasan, Shakir Sakran

الجامعة

الجامعة التكنولوجية

الكلية

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القسم الأكاديمي

قسم الهندسة الكهروميكانيكية

دولة الجامعة

العراق

الدرجة العلمية

دكتوراه

تاريخ الدرجة العلمية

2010

الملخص الإنجليزي

In Iraq, the young and elderly represent the largest percentage of individuals with a below elbow amputations due to trauma or disease of the limb.

Despite years of research and innovation, the current existing prosthetic hands but not flexible enough to accommodate a wide range of objects sizes and shapes.

Such as OTTOBOCK hand commercially available prosthetic hands (common in Iraq), are simple grippers, with one or two degrees of freedom.

Therefore, in this work, a prosthetic hand has been designed to enhance the ability of the prosthetic hand to perform optimal stable grasp, with a wide variety of objects, without augmenting the actuator power by using genetic algorithm with Mat lab program.

Five-fingered under actuated hand prosthesis has been investigated and constructed in order to achieve a good grasping functionality keeping a simple control.

This has been achieved by optimization design based on the principle of under actuation extended from the fingers to the hand itself, leading to the minimalist design of a mechanical architecture of prosthesis robotic hands with fifteen degrees of freedom, driven by only one actuator (mechanical or motor).

A differential mechanism allows the adaptability among the fingers and among the phalanges of each finger, thus enabling the grasp of irregular shaped objects.

The prosthetic hand prototype was built of hard ABS (Acrylonitrile Butadiene Styrene) plastic using rapid prototyping.

The different components of the hands were separately built and then assembled.

The critical components (e.g.

the guiding pins, sliding guides, and torsional springs) are made of metal.

Also, the present thesis presents a new contact-mechanics model for hemi cylindrical soft fingertips, proposed as a power-law equation.

That is, the half width of contact of a soft fingertip is proportional to the normal force raised to the power of, which ranges from 0 to 1 / 2.

A study of the position for application of the contact normal forces on phalanges has been done.

The results show that the contact normal force on the first phalanx is a function of the contact forces location on three phalanges of finger.

Moreover, the position of the force at second phalanx (determines if the contact force on the first phalanx will be positive or negative.

One had found that if the position of the force at second phalanx is bigger than 19 mm, then the contact force on the first phalanx is always positive.

This is very important because when is positive, a power grasp can surely be performed, on the other hand, if is negative (i.e., mm), this does not necessarily mean that the object will not be stable grasp with the three phalanxes.

While the contact normal force on the second phalanx is only affected by and the contact normal force on the third phalanx is neither a function of the contact forces location of first and second phalanges of finger nor the generalized coordinates.

Of course, the best region for grasping an object is for respectively, these values are very important in the grasping task.

The results also show that the genetic algorithm method is a powerful technique to compute the contact forces magnitude on the phalanx of prosthetic fingers, and many parameters can be introduced inside the matrix equations at a short computation time without affecting the method.

The total weight of this prototype is approximately 152g (without any actuator) and 524g (includes the motor, the transmission systems, the electronic components for the EMG signals processing, and battery).

Despite technical problems, six grasping modes were obtained (cylindrical, spherical, precision, lateral, hook, and Platform mode) in a natural flexion of the fingers with single mechanical actuation or single electrical motor in order to move the prosthetic hand.

The general result, subsuming the Timoshenko and Goodie contact theory for linear elastic cylinders materials, is in the form of a power equation.

The weighted least-squares curve fitting is applied to analyze the experimental data using the theory developed in this work for different types of silicon materials.

It is found that the experimental results (for respectively match very well with the theoretical prediction.

The equation which describes the nonlinear stiffness behavior is derived of soft contacts in a very concise (it is the product of an exponent and the ratio of the normal force versus the vertical displacement) and easy-to-use form based on the power law theory for soft hemi cylindrical fingers contacts.

التخصصات الرئيسية

الهندسة الميكانيكية

الموضوعات

• الروبوتات

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-305192