Project Overview

Problem Overview:
           In the United States, stroke is the leading cause of disability in adults [2]. After a stroke, many patients experience hemiparesis, a debilitating condition which is characterized by the weakening of movement and functionality on one side of the body. Though this condition is less severe than hemiplegia, hemiparesis still affects the lives of many patients. Patients with hemiparesis may be able to flex their fingers in order to grasp object but find it difficult to extend their fingers to let go or release an object. This loss of functionality in the gripping and releasing of objects can make it difficult for these patients of hemiparesis to perform basic, daily tasks. Creating a device that will aid their ability to grip and release objects will not only promote rehabilitation but also improve their quality of life. 

Design Constraints:

The OrthoGlove will offer stroke patients suffering from hemiparesis a chance to regain the use of their hands to perform basic tasks. But the device does operate with some limitations and restraints. These constraints are mainly caused by the design of the glove and the specific needs of stroke patients.

           To power the OrthoGlove’s motors, sensors, and microprocessor, an external battery will be used. Thus the design is limited by the battery’s capacity. To preserve battery life, the servos used will not be able to be supplied with the maximum voltage provided by the battery. Low-powered servos will limit the strength and precision of motion that the glove will be able to produce and patients will not be able to lift heavy weights above 100 to 200 oz. [3], [4]. Since servo motors cannot offer the finesse of healthy muscles, the individual wearing the glove would not be able to complete delicate functions such as writing or drawing properly [5]. The motors would also not be able to function as precisely as desired because of the low power state in which they will be working.

Since the OrthoGlove will be designed for long-term use, it must be comfortable. Many patients will be wearing this device for many consecutive hours doing extensive physical therapy. Pain during therapy is a common complaint among many stroke patients, so the orthosis will need to remain comfortable even after hours of repetitive exercise [2]. Badly-fitting orthoses can cause fatigue and further damage to paralyzed muscles [6]. Quick and powerful movements from the servos can also cause injury as badly-postured orthoses have been shown to cause fatigue [6]. However, servo control can be improved to closely mimic natural hand motion if effective algorithms are developed. This would allow patients to complete daily tasks in a similar manner as they would have pre-stroke.

Finally, all of these constraints will have to be addressed while keeping the cost of the OrthoGlove to under $300 dollars. With many pre-existing devices already on the market, a low-cost alternative would have a competitive edge in the industry.

   
Pre-Existing Solutions:
            One of the cornerstones of post-stroke physical therapy is the application of repeated exercise of affected limbs. For patients suffering from hemiparesis of the hand, studies have shown that repeated hand exercise improves hand function over time. It has been suggested that the brain retains enough plasticity after a stroke to relearn motor control with enough exercise [7]. This results in less time needed by patients to complete tasks using their hands. To assist in rehabilitation, many researchers have already developed hand orthoses to speed up and improve the recovery process [7] [8] [2].

Many devices for post-stroke hand rehabilitation have already been developed and are available to patients. The majority of the hand orthoses found on the market are meant for short-term, rehabilitation uses where patients wear the devices during therapy sessions with clinicians. Most of these devices involve orthoses that stimulate normal hand motion and assist finger extension. Some designs use other parts of the body to trigger hand movement, while others rely on assisting the remaining hand control that most patients retain after stroke.

In a study on the effects of stroke therapy with and without the use of orthoses, researchers at Northwestern University developed two separate orthoses designs. The first was a cable orthosis (CO) that assisted hand grasping via cables connected to the shoulder and elbow. This design extends all five fingers simultaneously when the shoulder or elbow is extended. The second design highlighted was a pneumatic orthosis (PO) that uses air-filled sacs attached to the undersides of fingers to buoy them in an extended position. In the study, patients using these orthoses were compared to those who received therapy without the use of these devices. After the one month trial period, all patients experienced an improvement in hand control. However, there was no significant improvement in the groups that used the CO and PO orthoses. [7]

While both of these designs use relatively simple and inexpensive materials, they were custom-built for the purposes of the study. However, there are hand orthoses currently on the market that have been widely used in the medical industry. One of the most popular orthoses is the Saeboflex (fig. 1). This device assists finger extension by using a system of springs that pull the fingers straight after they are closed. In a clinical trial, thirteen stroke patients suffering from hemiparesis received therapy using the Saeboflex for six hours each day for five days. During the trial, no patient complained of pain or discomfort. At the conclusion of the trial, patients experienced improvements in wrist function but did not gain any statistical improvements in finger extension. [8]

Fig. 1. A patient doing hand exercises with the Saeboflex. [9]

Another novel device currently on the market is the Bioness H200 orthosis (fig. 2). Instead of using springs, the H200 uses Functional Electrical Stimulation (FES) to stimulate paralyzed muscles in patients’ hands. With the aid of a wearable computer device, the H200 can be used as both a therapy device and an orthosis for daily use. A 2008 study showed that the device improved hand function for a woman suffering from post-stroke hemiparesis. The patient received therapy using the device three hours a day with clinicians over a twenty-day period. At the end of the trial, the patient experienced statistical improvements in hand motor control and required less time than before treatment to complete daily tasks. However, the study reported that the patient experienced fatigue and shoulder pain numerous times during the trial [2].

Fig. 2. A patient receiving therapy using the Bioness H200 device. [10]

Design Goal:

After a stroke, patients commonly experience hemiparesis which paralyzes limbs to various degrees depending on the extent of the stroke. Many patients specifically experience paralysis of the hand where grasping control is partially intact but finger extension is severely affected. Without finger extension, patients cannot use their hands to hold objects or complete everyday tasks. The OrthoGlove will restore finger extension and other affected hand controls to stroke patients using a system of sensors and motors.

This design consists of a motorized glove with sensors and a microprocessor to amplify and assist the residual motor control in affected hands. Finger extension and flexion will be achieved using fishing line cables attached to the glove fingertips so that all five fingers move as a single unit (fig. 3). Attached to the fingers will be a flex sensor that can detect the bending motion in the fingers. As patients attempt to move their fingers, the slight movement in the fingers will change the flex position of the flex sensor, triggering the motor to assist in the desired finger movement.

Figure 3. Detail of the fishing line/cable system that controls the fingers.

               The servo used in this design will be a Dynamixel AX-12 robot actuator. This is a special servo with a built-in microprocessor that can sense position, torque, temperature, and other variables while operating as a conventional servo. It also has around 160-200 oz.-in. of torque, far more than that of a conventional hobby servo [3]. All of the sensors and the motor will be connected to an Arduino UNO microprocessor which will read from the sensors to power the motor. 
              In conjunction with the sensors, the Dynamixel actuator will make the OrthoGlove operate like an exoskeleton for the hand. This will make the device useful for both rehabilitation and daily use, unlike the orthoses used by Northwestern University and the Saeboflex [7], [8]. The OrthoGlove will also have the advantage of assisting both opening and closing of the hands which most other orthoses can not accomplish. While the Bioness H200 is the most advanced of all the orthoses discussed, FES still has drawbacks such as fatigue and pain [2]. Both the Bioness and Saeboflex are also extremely expensive, costing upwards of a thousand dollars [11]. The Orthoglove will restore hand motion to patients without pain and for a fraction of the cost of current options.

Project Deliverables:

• OrthoGlove prototype
• Pro/Engineer model of OrthoGlove
• Arduino program 

Project Schedule:

Week 1
·         Research and make blog

Week 2
·         Research and write design proposal
·         Update blog

Week 3
·         Finish design proposal
·         Buy necessary material: flex sensor, rings, eyelets (to guide fishing line), fishing line, hand mannequin,  glove, motor, microprocessor, other electrical components
·         Update blog

Week 4
·         Make pro/E representation of design
·         Put together non-electrical components of design
·         Come up with programming strategy
·         Update blog

Week 5
·         Put together electrical components
·         Figure out how electronics will be attached to patient/other components of design
·         Update blog

Week 6
·         Characterize Flex sensor
·         Characterize motor
·         Write procedure and results of these tests for final report
·         Update blog

Week 7
·         Put together non-electronic and electronic components of design.
·         Write program to control glove and characterize movement
·         Continue improving design (fixing whatever problems arise, etc.)
·         Update blog

Week 8
·         Continue altering the glove as needed
·         Make Pro/E representation of final design
·         Write about final design/ conclusions etc. for report
·         Update blog

Week 9
·         Finish final report
·         Make presentation
·         Final touches on prototype
·         Update blog

Projected Budget:

Glove 1 X $22.49
http://www.amazon.com/Manzella-Power-Stretch-Glove-Medium/dp/B000VN3NHS/ref=sr_1_2?s=sporting-goods&ie=UTF8&qid=1334671391&sr=1-2

flex sensors: 2 X $12
http://microcontrollershop.com/product_info.php?products_id=3802

servos: 1 X $45
http://www.trossenrobotics.com/dynamixel-ax-12-robot-actuator.aspx

Arduino UNO 1 X $37
http://www.amazon.com/Arduino-Uno-Starter-Solderless-Breadboard/dp/B0051QHPJM

hardware (cables, nuts and bolts, springs)
Fishing line 1 X $4.18
http://www.amazon.com/Sporting-M1420-South-Bend-Monofilament/dp/B000SM3SCM/ref=sr_1_1?ie=UTF8&qid=1334631576&sr=8-1

Batteries 1 X $17 
http://www.amazon.com/Tenergy-3000mAh-Battery-Tamiya-Connectors/dp/B0037U35SO/ref=sr_1_2?s=toys-and-games&ie=UTF8&qid=1334632694&sr=1-2

TOTAL PRICE = approx. $140 (not including shipping)


Team members may also already have some materials at home, bringing the final cost down.