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How do bionic hands relate to physics?
How do bionic hands relate to physics?
Free body diagrams
Free body diagrams
Free body diagrams are a staple of physics, and they are used in many kinds of engineering. For example, in biomedical engineering they are used in the designing of prosthetics to understand the forces at play. For example, a simple way of actuating a finger is having a string along the edge of the finger like pulleys to contract the digits. To understand the model, engineers use free body diagrams not unlike the one pictured above.
Motor Selection
Motor Selection
In the creation of bionic hands two factors come into play when selecting motors. The first is size and weight, so that the motor fits in the prosthetic and is not too bulky.
The other is the ratio on the motor, as the max angular velocity of a motor is inversely correlated with the torque output. At the highest level, the motor will move infinitesimally slowly, but has incredible torque, whereas on the other end it will move with blazing speed, but not have any force behind the motion.
This is particularly important in bionic hands, as the hand needs to move quick enough that it works for everyday life, but also with enough torque that it can move things and actually interact with the world.
Torque and Newton's Second Law
Torque and Newton's Second Law
Humans naturally can rein in the strength of their own hand, but when it comes to bionic prosthetics, that work must be done by the hand itself. If the prosthetic moves too quickly, i.e. has too great an acceleration, then according to Newton's law of force and acceleration, the force will be high. With high force comes high torque, which can make for killer handshakes or a smashed meal.
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