To understand how TrueLimb and other advanced prosthetic arms are controlled, it’s important to understand what the term “myoelectric” means. When you think of a bionic arm or an advanced prosthetic arm, chances are you’re thinking of a myoelectric arm. The term “myoelectric prosthesis” is a catch-all for advanced prosthetic arms. TrueLimb is classified as a myoelectric arm. It has the same functionality and features as traditional myoelectric arms. But TrueLimb is dramatically different from traditional myoelectric arms in one specific way — the way the arm receives information from you, the user.
How You Control Traditional Myoelectric Prosthetic Arms
Both TrueLimb and traditional myoelectric prosthetic arms are controlled by sensors in the arms’ sockets. The socket functions as the way the arm connects to the body. It also contains the control mechanism for the arm. The sockets have sensors in them, and the sensors register muscle movements in your residual limb.
The sensors in traditional myoelectric prosthetic arms pick up electric signals generated by your muscles. This is where “electric” in the term “myoelectric” comes from, with “myo” meaning muscle. Typically there are two sensors in the socket, on either side of the residual limb. These myo-sites detect a muscle flex in either direction.
These sensors need to be very precisely placed in the socket, and align perfectly with the muscle sites they are receiving electrical signals from. They also require direct contact with the skin in order to register an electric signal. If there is not direct contact with dry skin, or the sensors are not perfectly placed, control of the arm will be impacted. You can not wear a protective sock while using a myoelectric prosthetic arm.
How You Control TrueLimb
In order to create a device that is truly intuitive and easy to use, TrueLimb reimagines how prosthetic arms are controlled. At the heart of this system is TrueSense™, a new patented technology that lets you operate a bionic arm in a completely new way.
Instead of just two sensors, TrueSense™ employs a range of ultra-precise sensors embedded within the socket. This 360-degree array of ultra-precise sensors respond to topographic changes in your residual limb, not electrical signals. Simply put, TrueSense™ interprets the intention behind muscle movements to open, close, and alternate grips.
Since TrueSense™ is not responding to electrical signals, direct skin contact with these sensors is not necessary. If you prefer, you can wear a protective sock on your residual limb. Perspiration or moisture will also never interfere with your control of the arm.
TrueSense™ is about more than just control. Through training and use, TrueSense learns the unique muscle strength and movements of your residual limb. If the strength of the muscles in your residual limb change over time, TrueSense™ learns and adapts to this change. The more you use your TrueLimb, the more muscle patterns TrueSense™ has to learn and recognize.