Parkinson’s disease brings on the shakes, and these tremors often get worse as the disease progresses. To prevent this symptom from interfering with patients’ daily lives, researchers in London have devised a clever arm exoskeleton that recognizes actions that require fine motor control, like lifting a cup or pointing, and turns on to suppress the tremors at those crucial moments.
It’s quite early days for this experimental device, which was discussed at the IEEE Body Sensor Network meeting earlier this month. But the researchers intend to develop their prototype to help patients with Parkinson’s, as well as people with essential tremor.
The research team, from Benny Lo’s lab at Imperial College London, made a lightweight exoskeleton that fits around the user’s arm (it weighs 350 grams, or less than 1 pound). Starting with a 3D-printed plastic frame, the researchers added two small servo motors, at the wrist and elbow, which contain positional sensors. They also attached an accelerometer and gyroscope to the back of the hand.
The combined data from these sensors allowed the researchers to determine movement signatures for common daily activities, including walking, running, picking up a bottle of water, and pointing. So far, the prototype can distinguish activities with about 70 percent accuracy. As the researchers develop the classification software, they could add in other activities that Parkinson’s patients struggle with, such as writing, typing, and eating.
To steady the user’s hand, the exoskeleton detects the rhythmic movements caused by the tremor and uses its actuators to produce precise countermovements, pushing on the arm with vibration-like motions that cancel out the shaking. This isn’t the first arm exoskeleton to employ this method; several other research groups have worked on similar devices.
But Lo’s lab gave their prototype a compelling new feature. Because the exoskeleton can classify the user’s activities, the researchers say it can turn on to suppress tremors only when really necessary. So it can remain in standby mode when the user is walking to the couch or sitting in front of the TV, then switch on when the user reaches out to pick up a glass of water. That selectivity would minimize power consumption, making the device more practical.
There are many other approaches to help people deal with tremors. For Parkinson’s patients there are medications (though some become less effective over time) and surgically implanted deep brain stimulators. Another experimental method uses electrodes on the skin to both record the rhythmic movement of the arm muscles during tremors and stimulate the muscles in a countervailing fashion. To address the particular challenge of eating, there’s even a fancy spoon that detects tremor and cancels it out.