Dynamic Hand Support for ET Reducing

Last crawled date: 1 year, 11 months ago

This will be my second entry for the GrabCAD challenge:
https://grabcad.com/challenges/va-innovation-creation-series-challenge-2

Statistical research of essential tremor among people over 65 years old shows that the prevalence of disease reaches about 600 per 100 000 people. This means that disease affects tens of millions of people. Serious forms of essential tremor catastrophically affect on the coordination of voluntary movements of hands, making an everyday self-services difficult or impossible.In addition to pharmacotherapy, and more radical surgery, for many years now developments in the field of mechanical suppression of hand tremor using wearable mechanical devices are carried out. The most successful device (IMHO) is this smart spoon: http://www.liftware.com/

Yet, the most promising in terms of efficiency, is using of a hand exoskeleton with full control of kinematics. It seems that the kinematic complexity of the human hand raises this task as the difficult to achieve rank. Such devices are bulky, expensive and usually exist only at the stage of laboratory installations, such as this:
http://www.tremorjournal.org/article/downloadSuppFile/77/figure-77-1-raw

While searching for possible solutions, I was focused on the design of effective, but compromise, realizable and available by components and a price.
Also, the design should have a novelty in comparison with the existing solutions of the problem.

Existing methods of suppressing tremors involve the use of one or more joint orthoses, with damping motion in the joint. Usually, for efficient suppress of a hand tremor the solution must use ortheses in several joints - wrist, elbow, shoulder. The point of support in this case falls on the belt ties of joint orthoses.

What if to transfer the point of support of the hand directly on the shoulder by a flexible cord?

Implementation of the idea.

It is expected that developed device should work as a dynamic-controlled support with damping. The device allows to hold a hand by height in desired equilibrium position.
Of course the device will be efficient only if the cord is always tensioned. The cord tension must be maintained at a certain level in any arm position. For such a function is the simplest use of spool with a torsion spring. I believe that the strength of the spring should be comparable with the weight of a relaxed hand.
Also, to suppress the vibrations of arm, the cord spool must be damped. The suspension point of the palm should be as close as possible to the fingers.

In the simplest case, the device can be only passive.
The minimum set of components in this case is: the spool with a cord, torsion spring, a rotary damper, based on the dilatant fluid.

I think that using of dynamic damping is more perspective. The most perspective is the use of the damper based on a magnetorheological fluid. Magnetorheological damper (MR damper) has a high-speed control and high dynamic range of damping adjustment, from full off damping to full brake. In this case, the device become "smart" by also adding an electronic control unit with an accelerometer.
The device will be even more perfect if the force of the spring can be controlled dynamically. In this case, there must be added the following components: DC gear motor, cord tension sensor, cord spool revolution counter and spring revolution counter.

The cord is a thin round cloth, not prone to tangling, inextensible (e.g. from aramid fiber).
Such design of the device is shown in illustrations. To simplify, speed and spool-spring sensors not shown in the renderings.

It is assumed that in a properly configured device, the movement (lifting, lowering, and stopping the hand at a certain position) is only triggered by efforts of the flexor or extensor muscles, further uniform motion is performed automatically by winding or unwinding of the cord. Relaxed muscles of the driven hand can also provide an additional factor in reducing tremor. Of course such action for a person suffering from an ET might be unusual, and it will require additional training of a person and the device.

TECHNICAL REQUIREMENTS of the challenge do not envisage using of power source.

The proposed method for suppressing tremors do not completely rule out a passive device. But intelligent damping can serve as a key to a successful application. The energy of the battery is used sparingly and only for damping control. It is assumed that, and the device can work a weeks without recharging.

Damping behavior can be controlled intelligently by recognizing hand gestures via accelerometer. It can be easily realized with software algorithm in the electronic control unit. A similar method of controlling acceleration and deceleration is used in the well-known electric scooter Segway.

As fantastic function, device may be provided by voice control.
This function can be implemented using the Google Voice service, if it is additionally provided with a bluetooth module to connect to your smartphone. Of course this function requires a special application.
Examples of voice commands:
"Up" - lifting a cup of water to the mouth,
"Down" – putting down a cup on a table.
"Stop" - Stop arm at the desired height.
"Eating" - the periodic lifting and lowering hands.
"Key" - release hands to the height of the door keyhole.

The second part of the device is a point of support. The support point is realized as a corset with the tab on the shoulder area. On the tab placed a round groove with a magnet. The end of the cord is joined to a plastic ball with magnetic core. In such a construction it is assumed that a person suffering from ET will be available to attach and detach the cord singly.

The proposed method suppression tremor does not exclude placement of a support point elsewhere. For greater comfort, it may be placed on the left shoulder for a right hand or on a waist-belt. Also a support point may be mounted on the table edge by means of clip for tablecloth.

The most important part of the device - the algorithm of the electronic control unit may be the subject of additional scientific research and clinical trials.
_______

At the end I bring comic video of how it works.
Note: The video contains a short fragment of the Soviet satirical play "Energetic People" (1974)
This video excerpt shows "creativity" of a man suffering from alcoholic hand tremor when, he tries to drink a glass of whiskey. Video is humorous, but of course, I did not want to hurt people suffering from hand tremors.
https://www.youtube.com/watch?v=rWpXG530oY8

Special thanks to Cardero Carlos for ARTICULATED HUMAN BODY.