Mechanism Needed for a Compact, High-Torque Transradial Prosthetic Arm

  • Thread starter KavehSanaei
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In summary, the article discusses the development of a compact, high-torque transradial prosthetic arm that utilizes an innovative mechanism to enhance functionality and user experience. It emphasizes the need for a design that allows for greater torque output while maintaining a lightweight and ergonomic structure. The proposed mechanism aims to improve the performance of prosthetic limbs, enabling users to perform daily tasks more efficiently and with greater ease. The research highlights the importance of integrating advanced materials and engineering principles to achieve these goals.
  • #1
KavehSanaei
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Hello everyone,

I'm collaborating with a group of engineering friends to develop a transradial prosthetic arm that uses a mechanical claw for gripping. This prosthetic is designed for physical activities, demanding both strength and precision. We're aiming for a pinching force of around 8 Nm (~70 lb-in) and are using a low-torque, high-speed motor (e.g., ElectroCraft RPX22) combined with a 100:1 gearbox.

Our challenge is maintaining this torque during the gripping action, which could last from several seconds up to a few minutes. The mechanism must ensure zero backlash during pinching for safe use.

We're exploring various mechanisms to hold the claws in place effectively:

  • Cam mechanisms
  • Zero-degree ratchet systems for zero backlash
  • Locking via hydraulic or pneumatic pistons
  • Utilizing the intrinsic torque of the motor and gearbox

Additionally, the mechanism needs to be compact and lightweight since it is a prosthetic.

We're looking for suggestions. What mechanism would you recommend for maintaining the claw's position under torque in a compact and lightweight design? We're open to ideas, experiences, and any suggestions you might have.

Thank you in advance for your input and ideas!
 
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  • #2
Welcome to PF.

KavehSanaei said:
to develop a transradial prosthetic arm that uses a mechanical claw for gripping.
I'm not familiar with the term "transradial" in the context of a prosthetic arm. Are you referring to the radius bone, or is there some other meaning? Thanks.

And can you upload some drawings of your concepts so far? Use the "Attach files" link below the Edit window to upload a PDF or JPEG image of your work
 
  • #3
Below I have attached a rough drawing of what we are trying to design. Both sides of the claw need to move independently. Two motors move each side of the claw independently. The gearboxes drive a cable and pully system that articulates the claws. We want the calws to have zero backlash once they are in position.

I also included an example picture of a transradial (below the elbow) prosthetic. It being transradial is not relevant to the mechanism itself.
prototype claw.png
transradial.jpg
 
  • #4
KavehSanaei said:
Both sides of the claw need to move independently. Two motors move each side of the claw independently. The gearboxes drive a cable and pully system that articulates the claws. We want the calws to have zero backlash once they are in position.
How are you going to achieve zero backlash in this? Can you post a more detailed drawing?
 
  • #5
Instead of Zero backlash, which is rather difficult in the real world, I suggest a rather hard compliant material covering the jaws/grippers -- maybe a semi-hard polyurethane. Polyurethane came to mind because it is not attacked by most chemicals and can be formulated and cast in about any hardness and shape you want.

This could be chosen for maybe a millimeter of compression at maximum force.

[edit/afterthought] If you Really require Zero Backlash, use a spring on the grippers to hold the grippers closed and use the motor to open them.

Cheers,
Tom

p.s. please keep us updated on your progress/solutions, we like to learn too!
 
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FAQ: Mechanism Needed for a Compact, High-Torque Transradial Prosthetic Arm

What is the primary mechanism used to achieve high torque in a compact transradial prosthetic arm?

The primary mechanism used to achieve high torque in a compact transradial prosthetic arm typically involves a combination of advanced motor technologies, such as brushless DC motors, and high-efficiency gear systems like planetary gears. These components work together to maximize torque output while maintaining a compact form factor.

How does the compact design affect the performance and functionality of the prosthetic arm?

The compact design aims to balance performance with wearability. While a smaller form factor can limit the size of the motor and gears, advances in material science and engineering allow for high-efficiency components that do not sacrifice torque or functionality. This ensures that the prosthetic remains lightweight and comfortable for the user while still providing robust performance.

What materials are commonly used to construct high-torque transradial prosthetic arms?

High-torque transradial prosthetic arms are often constructed using lightweight, durable materials such as carbon fiber composites, titanium, and high-strength aluminum alloys. These materials provide the necessary strength and durability while keeping the prosthetic lightweight and comfortable for the user.

How is the power supply managed in a compact, high-torque transradial prosthetic arm?

The power supply in a compact, high-torque transradial prosthetic arm is typically managed using advanced battery technologies, such as lithium-ion or lithium-polymer batteries. These batteries offer a high energy density, providing sufficient power for extended use while remaining lightweight and compact. Additionally, power management systems are employed to optimize energy consumption and extend battery life.

What are the main challenges in developing a compact, high-torque transradial prosthetic arm?

The main challenges in developing a compact, high-torque transradial prosthetic arm include achieving the right balance between size, weight, and power. Engineers must design components that are small and lightweight yet capable of delivering high torque. Additionally, ensuring the durability and reliability of the prosthetic under various conditions, as well as making it affordable and accessible to users, are significant challenges that need to be addressed.

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