Biomechatronics Research
Several laboratories around the world conduct research in biomechatronics, including MIT, University of Twente (Netherlands), and University of California at Berkeley. Current research focuses on three main areas:- Analyze human motions, which are complex, to aid in the design of biomechatronic devices
- Study how electronic devices can be interfaced with the nervous system (implantable electrodes in brain and muscle, surface galvanic electrodes on skin)
- Test ways of using living muscle tissue as actuators for electronic devices
Analyze Human Motions
Human motions are complex, whether it be reaching for a glass or walking over rough terrain. We must understand how humans move so that we can design biomechatronic devices that effectively mimic and aid human movement.
Dr. Peter Veltink and colleagues at the University of Twente are analyzing walking movements (gait analysis) by measuring body movements with camera systems, ground reactive forces with force meters, and muscle activity with electromyograms (recordings of the electrical activity produced by muscle contractions). The analysis of normal and impaired patients will help understand free walking motions and diagnose specific gait problems in impaired patients. Veltink's group similarly evaluates balance control while walking and standing.
Dr. Hugh Herr's Biomechatronics group at MIT uses computer models and camera analyses of movement to study balance , leg retraction during running , and angular momentum conservation during walking.
Interfacing Electronic Devices with Humans
An important aspect that separates biomechatronics devices from conventional orthotic and prosthetic devices is the ability to connect with the nerves and muscle systems of the user so he can send and receive information from the device.
Peter Veltink's group in the Netherlands is using implantable electrodes to stimulate the calf muscles. They are developing sensing and control methods for the dorsiflexor muscles, which lift the foot during walking. This will help to treat paralysis and stroke victims who cannot control this foot during walking (i.e. dropped foot).
Hermie Hermens and Laura Kallenberg of Veltink's group are using electrodes placed on the skin to monitor the electrical activity of the underlying muscles (electromyography) rather than using electrodes implanted directly into them. This reduces pain and discomfort and may also be a pathway for 2-way communication. (http://bss.ewi.utwente.nl/research/biomechatronics/rsi.doc/index.html).
Veltink's group is also using electromyogram surface electrodes for feedback and control of lower-leg prosthetics. In the prosthetic, the knee angle is detected and the information is relayed by electromyography to the stump muscles in the amputated leg. The wearer can sense the activity and be taught to interpret it. Eventually the electrical activity of the stump muscles might be used to control the prosthetic.
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Hugh Herr's group at MIT is developing a sieve integrated circuit electrode (an integrated circuit is a tiny plastic chip with an entire electrical circuit imprinted on it). In this setup, two stumps of nerve are connected through a guidance channel (a small tube that keeps the nerve endings close to each other). In the channel, there is a sieve with each hole connected to an electrode on an integrated circuit board. As the nerve fibers grow through the holes to connect with each end, they contact the electrodes, thereby creating an interface.
Advanced Orthotics and Prosthetic Devices
Hugh Herr's lab is also making prosthetic devices that better mimic true human movements:
- A knee prosthesis senses knee force, torque, and position and adjusts the swing and movement of the knee to the individual user. In the knee is a magnetorheologic fluid, which is oil containing a suspension of tiny iron particles (0.1-10 microns in diameter). An electromagnetic field applied across the oil can change the thickness or viscosity of the fluid because the iron particles form chains as they align with the magnetic field. Because the viscosity of the fluid can be adjusted by fine tuning the electromagnetic field, this controls and adjusts the resistance of the knee on a moment-to-moment basis, thereby giving the user a realist gait. (See http://biomech.media.mit.edu/research/pro3_1.htm for a video of this device). Commercially, this knee is a product called Rheo-KneeTM, which is made by Ossur.
- To treat drop foot gait, an orthotic device was developed that controls and varies the stiffness of the ankle joint on a moment-to-moment basis as the user steps forward. This device gives the user a more normal gait than current orthotic devices.
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