RinksCustoms, · "...Originally thought of trying to capture the individual muscle movements but realized the potential of crosstalk having that many sensors in proximity. It's likely that obtaining isolated muscle contractions isn't all that feasable through EMG sensors. Embeded sensors (similar to an RFID tag) could be implanted below the skin to obtain the individual muscle contractions and assosiated strength or amplitude of these contractions..." · "...There's one "bump" in this thinking... To exactly mimic the human hand with ALL points of articulation, you also need to sense pinch, those muscles reside on the hand along with a few others, for amputee's this would pose a larger problem that EMG or ultrasound wouldn't be able to process...." · ·
In 10 years of working in the field of robotic research for prosthetic arms and legs.· Only in very extreme cases did I ever see electrodes that directly tapped into the muscle.· The problem arises that when you amputate a hand, yes all of the muscles remain intact within the forearm, but over time the muscles will atrophy because they won't have any external resistance to keep them in tone.· As a result the electrode located directly in the muscle only works for a short period of time.· The initial signals are useful though in determining a sequence of events that you would use to control an articulating prosthetic hand, but the motions would be pre-recorded to mimic an event at a later time. ·
Most myo-electric signals are taken from the skin level of the patient.· These signals use a common mode differential amplifier to detect the slight phase difference in voltage (typically 10's·of mV) at the skin level. ·
Other detection methods can be done with IR reflection at skin level.· The idea here is that when a muscle contracts, the blood density within the muscle changes.
Edit:
Here is an article that briefly goes over the Sodium-Potassium mechanism that I made reference to in an earlier post.· I find it very interesting that this article describes the·brain as a chemical power house with an energy density of 140kV per centimeter!!!· ...·
http://www.thenakedscientists.com/HTML/articles/article/how-does-a-brain-cell-work/ · ...I forget (ironic) at the moment what the exact frequency range is, but there are frequency components that can be measured that directly correlate to the Sodium-Potassium wave/chain reaction originating from the brain and ending in·the muscle.· The signal generated from the brain almost resembles a multi-phase PWM, increasing duty cycle proportional to·how hard the muscle is flexed.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 9/24/2008 6:43:26 AM GMT
Rayman... this OT but certainly in the spirit of recent posts.
I think we are close to a SIG here...
There was a recent story about prosthetics work at the Rehab institute in Chicago... they placed sensors in the area of the last intact portion of the nerve that originally controlled the amputated arm... and used some kind of signal analysis to figure out exactly what part of the nerve was firing and then hooked the prosthesis up to a signal generated by that analysis. It was on TV... reported to me by a friend. So I don't have the details.
But the astounding part was that the patient actually had the sensation of being able to feel the prosthesis...
Years ago, I came at this from the standpoint of having a retina that was still electrically excitable but permanently detached from its photoreceptors... complete blindness. I did a fairly exhaustive search. What I found was that whenever you place any kind of electrode directly in contact with a nerve...(which is essentially what you have left after a permanent retinal detachment) the results are never what you want... either the electrode or the nerve eventually dies. The same is probably true for muscles and electrodes. However, if you place a dye in a nerve, you don't have to touch it... you can stimulate the nerve with light[noparse]:)[/noparse] I gave up on that avenue, when I learned a little more about perception and I don't know if that idea ever got utilized to try to do something about spinal injuries. The idea hasn't been used in eye research yet.
Controlling a prosthesis with another muscle group is a similar problem... what you need to know is what is the intact muscle group is doing and translate that info into prosthetic movements. Oxygen utilization is a very good source of information... and there are a variety of ways to sense it.
Char materials are probably the best way to create a 3D oxygen sensitive probe array in any tissue. Why? Char materials trap oxygen... for a little while... and turn it into a quasi stable free radical ..which can be sensed very rapidly in 3D, using EPR(ESR). In this case the implanted coil would be intended to receive the ESR signal, which could be analyzed to provide a 3D map of oxygen concentrations. Sort of like MRI... but a thousand times faster... and your coil doesn't have to touch anything except the scar that forms around it. The whole technology can be miniaturized and is a practical way to sense 3D energy utilization from tissue in a relatively non-invasive fashion.
My expert and friend was Bob Clarkson at the U of I... unfortunately he is now with his maker... before he died we were trying to figure out how to control nerve growth patterns in vivo... any ESR guys here?
Comments
·
"...Originally thought of trying to capture the individual muscle movements but realized the potential of crosstalk having that many sensors in proximity. It's likely that obtaining isolated muscle contractions isn't all that feasable through EMG sensors. Embeded sensors (similar to an RFID tag) could be implanted below the skin to obtain the individual muscle contractions and assosiated strength or amplitude of these contractions..."
·
"...There's one "bump" in this thinking... To exactly mimic the human hand with ALL points of articulation, you also need to sense pinch, those muscles reside on the hand along with a few others, for amputee's this would pose a larger problem that EMG or ultrasound wouldn't be able to process...."
·
·
In 10 years of working in the field of robotic research for prosthetic arms and legs.· Only in very extreme cases did I ever see electrodes that directly tapped into the muscle.· The problem arises that when you amputate a hand, yes all of the muscles remain intact within the forearm, but over time the muscles will atrophy because they won't have any external resistance to keep them in tone.· As a result the electrode located directly in the muscle only works for a short period of time.· The initial signals are useful though in determining a sequence of events that you would use to control an articulating prosthetic hand, but the motions would be pre-recorded to mimic an event at a later time.
·
Most myo-electric signals are taken from the skin level of the patient.· These signals use a common mode differential amplifier to detect the slight phase difference in voltage (typically 10's·of mV) at the skin level.
·
Other detection methods can be done with IR reflection at skin level.· The idea here is that when a muscle contracts, the blood density within the muscle changes.
Edit:
Here is an article that briefly goes over the Sodium-Potassium mechanism that I made reference to in an earlier post.· I find it very interesting that this article describes the·brain as a chemical power house with an energy density of 140kV per centimeter!!!· ...·
http://www.thenakedscientists.com/HTML/articles/article/how-does-a-brain-cell-work/
·
...I forget (ironic) at the moment what the exact frequency range is, but there are frequency components that can be measured that directly correlate to the Sodium-Potassium wave/chain reaction originating from the brain and ending in·the muscle.· The signal generated from the brain almost resembles a multi-phase PWM, increasing duty cycle proportional to·how hard the muscle is flexed.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 9/24/2008 6:43:26 AM GMT
I think we are close to a SIG here...
There was a recent story about prosthetics work at the Rehab institute in Chicago... they placed sensors in the area of the last intact portion of the nerve that originally controlled the amputated arm... and used some kind of signal analysis to figure out exactly what part of the nerve was firing and then hooked the prosthesis up to a signal generated by that analysis. It was on TV... reported to me by a friend. So I don't have the details.
But the astounding part was that the patient actually had the sensation of being able to feel the prosthesis...
Years ago, I came at this from the standpoint of having a retina that was still electrically excitable but permanently detached from its photoreceptors... complete blindness. I did a fairly exhaustive search. What I found was that whenever you place any kind of electrode directly in contact with a nerve...(which is essentially what you have left after a permanent retinal detachment) the results are never what you want... either the electrode or the nerve eventually dies. The same is probably true for muscles and electrodes. However, if you place a dye in a nerve, you don't have to touch it... you can stimulate the nerve with light[noparse]:)[/noparse] I gave up on that avenue, when I learned a little more about perception and I don't know if that idea ever got utilized to try to do something about spinal injuries. The idea hasn't been used in eye research yet.
Controlling a prosthesis with another muscle group is a similar problem... what you need to know is what is the intact muscle group is doing and translate that info into prosthetic movements. Oxygen utilization is a very good source of information... and there are a variety of ways to sense it.
Char materials are probably the best way to create a 3D oxygen sensitive probe array in any tissue. Why? Char materials trap oxygen... for a little while... and turn it into a quasi stable free radical ..which can be sensed very rapidly in 3D, using EPR(ESR). In this case the implanted coil would be intended to receive the ESR signal, which could be analyzed to provide a 3D map of oxygen concentrations. Sort of like MRI... but a thousand times faster... and your coil doesn't have to touch anything except the scar that forms around it. The whole technology can be miniaturized and is a practical way to sense 3D energy utilization from tissue in a relatively non-invasive fashion.
My expert and friend was Bob Clarkson at the U of I... unfortunately he is now with his maker... before he died we were trying to figure out how to control nerve growth patterns in vivo... any ESR guys here?
http://books.google.com/books?id=2oN1p-2czmQC&pg=PA575&lpg=PA575&dq=ESR+free+radicals+char+materials&source=web&ots=lqH8fRBD2R&sig=vtl0KqFXHV8Uhtpzjtt4eZB4RL0&hl=en&sa=X&oi=book_result&resnum=8&ct=result#PPA1,M1
Rich
Blind people can see... but only in their dreams. That fact and some solenoids are really all you need.
Post Edited (rjo_) : 9/24/2008 3:01:10 PM GMT