For those missing limbs, a robotic prosthesis represents a real and useful way to regain capability.But such prostheses are traditionally very expensive and are inaccessible to a large percentage of the people who would benefit from them.In an effort to improve the situation, Pavel Kochetkov of Weird Motions Lab designed this affordable open-source robotic prosthetic arm.
When it comes to a prosthesis like this, there are two big challenges.The first is the mechanical design, as it needs to mirror the physiology of the user, while being powerful enough to be useful and comfortable enough to be practical.The second is control, because the prosthesis needs to be intuitive and seamless in everyday use.
Kochetkov overcame both challenges on a budget.This “bionic arm” straps onto the upper arm with synthetic foam pads for comfort.The frame is a relatively lightweight combination of steel and 3D-printed plastic.
It is intended to replicate the functionality of the lower arm and hand.It does so with two joints: an elbow and gripper.Those are actuated by DSservo DS51150 servo motors operating under the power of an Arduino Leonardo board.
The Arduino controls those motors according to input from two sensors: a gyroscope and a myoelectric sensor.The gyroscope simply tells the Arduino the current orientation (relative to Earth’s gravity) of the upper arm.The myoelectric sensor is more interesting.
It detects bicep muscle activity, so flexing is a control command.In theory, the user will develop muscle memory to control the arm and that will become seamless.Kochetkov’s demonstration of the bionic arm is compelling.
He is able to perform tasks that require a fair amount of dexterity, which is impressive given the low cost of the prothesis.