The video below demonstrates some of the research done with prosthetic arms. It is a few years old and may not represent the absolute latest in prosthetics but it does provide a good example of what robotics technology can do in this area.
In the video the prosthetic arms are being controlled by the nervous system but this doesn’t allow for any feedback from the arm. The only way the user can know how the arm is positioned or if it is touching anything is to look at it. This limitation makes grasping small or delicate objects difficult.
One solution to this problem is using what is sometimes referred to as a haptic device mounted somewhere on the patents body and connected to the prosthetic. This device would take input from sensors on the prosthetic and translate that into something the user could feel. For example, if the device was mounted on the patent’s back then it would apply pressure to a point on their back in proportion to pressure applied to a pressure sensor on the prosthetic. The idea is that now the person using the prosthetic arm can grasp something delicate, like a paper cup, without crushing it.
The next step up from this is to make it so instead of feeling the pressure on some other part of their body they actually feel it on their missing hand. The surgery the subjects in the video underwent to restore some of the severed nerves allowed for them to feel sensations of touch in the missing hand. So, in theory, all you have to do is place a haptic device on the person’s chest and line it up with the appropriate nerve endings. In reality, it isn’t that easy.
The paper On the Design of Miniature Haptic Devices for Upper Extremity Prosthetics (this paper is from the IEEE website and the full text may not be available to people without a subscription) goes into more detail and documents some of the work being done in this area. It discusses the development of three haptic devices that can provide touch, pressure, vibration, shear force and temperature to an amputee who has had targeted nerve reinnervation surgery.
This is just one of many different aspects of robotic prosthetics and hopefully I’ll be able to discuss some others in future posts.
Great post--nice use of video, and I like that you link to the IEEE paper and indicate subscription required. Good, focused foray into the topic.
ReplyDelete9News had a story last night or the night before on some high school students who are in a pre-engineering program at a technical school (maybe in Thornton) who designed not prosthetics but robotic devices to assist a few people with disabilities. If you can find it, you should check it out. An interesting take on your topic.