Design and fabrication of a hybridized modular prosthetic arm

Project Title

Design and fabrication of a hybridized modular prosthetic arm

Project Area of Specialization Biomedical EngineeringProject Summary

Project summary:

An increasing number of upper limb amputations occur each year due to a variety of reasons including trauma, hazardous workplace incidents and congenital defects etc. This results in the person being unable to perform activities of daily living with ease, feel like an outcast among the society and limits their job opportunities as well leaving them both financially and mentally distressed and unable to survive independently. This is where rehabilitative devices such as prosthetic hands come in that are aimed towards restoring lost functionality. Looking at the Pakistani market, where most amputees belong to the lower-class laborer or middle-class category, we can see that there exists a wide gap between the product available and the demands of the consumer. For example:

• Devices available have limited motion with 1-2 DOF max
• Have primitive and purely cosmetic designs with limited functionality
• Maybe highly functional but extremely expensive.

Usually advanced and highly functional prosthetics made either locally or internationally employ techniques such as additive manufacturing specifically 3D printing of plastic filaments to allow for rapid prototyping and production of complex designs. While these may provide improved functionality, they clearly lack structural integrity.

Our aim is to design a prosthetic arm (specifically for an upper limb above the elbow amputee) that not only is affordable but is also highly functional. We hope to do this via employing two distinct approaches towards designing the product, first of which is a modular approach and the second being a hybridized structure.

• The Modular approach:
  • This will employ the use of easily replaceable and serviceable components that can be rapidly manufactured in large quantities to meet consumer demands.
• The Hybridized approach:
  • This will eliminate the problem of structural integrity by using different types of materials combined with a simplified design aimed towards the demands of the consumer

Project Objectives

Project Objectives:

• Cost-effective design
• Modular components that are easily replaceable and serviceable
• Hybridized design that does not solely employ 3D printing for manufacturing instead uses appropriate materials that are structurally sound and easy to rapidly manufacture via processes such as injection molding and casting

Project Implementation Method

Project Implementation Method:

The project will be made using components easily available in the market so as to make the design feasible, easy to manufacture and reduce service costs overall. The arm is to be designed for an above the elbow amputee which will constitute of three elements or parts. the coupling element the end element and the connecting element.

The coupling element will comprise of a fiberglass socket filled with silicone molded and formed according to the patient’s requirements and comforts i.e. their stump and gold-plated reusable electrodes will be embedded into the silicone so as to acquire real-time EMG signals to control of the arm. The signals will serve as an input to the machine learning algorithm coded into the microcontroller thus providing an output to the control system.

The connecting elements can be divided into two parts, the first being the 3D printed forearm and the second being the metallic upper arm. The connecting elements will further comprise of two joints i.e. the elbow and the shoulder. The elbow will be a high torque servo motor(60kgcm-1) controlled via a myoelectrical control signal while the shoulder will be passively controlled by the body.

The end element will be an opposable gripper as the aim of this project is to achieve at least the rudimentary task of grabbing and picking up objects with varying force. The force and grip strength will be controlled using current sensors to properly estimate the load needed and applied to grasp the object of concern.

Lastly the batteries and remaining electronics will be integrated into the arm specifically at the forearm so as to allow wireless and untethered control for over 4-8 hours of operation and constant load.

Benefits of the Project

Benefits of the project:

• A cost-effective & affordable product
• Highly functional to allow the user to perform activities of daily living with ease
• Ease of repair and service
• Ease of manufacturing:
• Modularity
• Structurally sound
• Simplified design
• Use of materials best fit for the job
• Community integration
• Vocational Rehabilitation

Technical Details of Final Deliverable

Technical Details of Final Deliverable:

• Passively controlled shoulder joint
• Custom fitted coupling element with embedded reusable electrodes
• Durable and lightweight metallic upper arm
• Elbow joint with (1 DOF)
• Rechargeable device with a days’ worth of working capacity
• Myoelectrical control
• Opposable Gripper (1 DOF)
• Rotating wrist (1 DOF)
• 3D printed PLA forearm that also encases the electrical components

Final Deliverable of the Project HW/SW integrated systemCore Industry HealthOther Industries Medical , Manufacturing Core Technology RoboticsOther Technologies Artificial Intelligence(AI), 3D/4D Printing, Wearables and ImplantablesSustainable Development Goals Good Health and Well-Being for People, Decent Work and Economic Growth, Industry, Innovation and Infrastructure, Reduced InequalityRequired Resources

Item Name	Type	No. of Units	Per Unit Cost (in Rs)	Total (in Rs)
			Total in (Rs)	80000
Servo Motor	Equipment	1	4500	4500
Servo Motor	Equipment	3	3500	10500
Custom Coupling Element	Equipment	1	3000	3000
Custom Connecting Element	Equipment	1	10000	10000
Reusable Electrodes	Equipment	6	200	1200
Micro controller	Equipment	1	1200	1200
Batteries	Equipment	2	3000	6000
Buck Converter	Equipment	1	1500	1500
Power Supply	Equipment	1	5000	5000
Servo Gripper	Equipment	1	2500	2500
Forearm	Equipment	1	20000	20000
Servo Brackets	Equipment	10	200	2000
Jumper Cables	Equipment	60	5	300
Electrode Paste	Equipment	1	900	900
Custom PCB Manufacturing	Equipment	2	700	1400
Amputee Compensation	Miscellaneous	1	5000	5000
Travel/ Transport	Miscellaneous	1	1500	1500
Clinical Consultation	Miscellaneous	1	3000	3000
Printing	Miscellaneous	1	250	250
Stationery	Miscellaneous	1	250	250