Project Proposal: Assistive Robotic Arm

By: Danielle McGeary Megan Madariaga

Asma Ali

Client Contact: Merriam Kurland

Speech Pathologist Hampton Elementary School

263 Main Street Hampton, CT 06247

(860)-455-9490

Executive Summary Contained within this document is a proposal to develop an assistive robotic arm for a student with limited mobility. Presented in this proposal is a brief description of Cerebral Palsy along with the client’s particular case and nature of his condition. A design schematic is also provided for each component of the device. A brief description of each component’s individual function along with a suitable material for the construction of each component are also given. Visuals are given to provide the reader with an accurate interpretation of the design. Research, regarding patents and devices similar to this assistive robotic arm, was conducted and is presented in this proposal. 1 - Introduction 1.1 - Background

Cerebral Palsy is a debilitating disease that causes chronic muscle impairment. Fortunately, the effects of this disease do not worsen over time. Although it is known that Cerebral Palsy is caused by faulty development or damage to that of the motor cortex of an infant’s brain, researchers cannot provide an answer as to why this defect occurs. The effects of Cerebral Palsy can range from extremely mild to incredibly severe. While not every patient that is diagnosed with this disease has a profound handicap that causes hindrances in everyday society, all those suffering from Cerebral Palsy do share some impediment with fine motor control. Symptoms of this syndrome can also include problems with balance, posture, verbal articulation, involuntary movements, and sometimes mental impairment. Cerebral Palsy is often first detected in infants, under the age of three, when developmental milestones are not reached.

Our client’s particular form of Cerebral Palsy can be classified as Athetoid Quadriplegia. The term athetiod represents the type of muscle impairment and the term quadriplegia describes the area of muscles involved. Patients suffering from Athetiod Cerebral Palsy lack the ability to control the particular muscles in the affected area of the body at all. Patients who suffer from the quadriplegia form of this type of Cerebral Palsy lack muscle control that encompasses all four limbs and the trunk. Since our patient suffers form such a severe impairment, he can be classified as profoundly handicapped. Sadly, our patient is confined to an electric wheel chair and is incapable of being independent. Our client cannot feed himself and is forced to have a personal assistant with him throughout the day. Fortunately, our client does not show any signs of being mentally impaired. He is academically competent and ranks amongst the top of his class.

The client also suffers from a severe oral handicap and only communicates nonverbally. The client’s only true form of communication is via a “Dyna Vox”, an augmentative communication device that orally speaks what is entered by the client from the external alphabet touch screen. The client’s progress with this machine proves he is extremely intelligent. Communication though the “Dyna Vox” requires an extensive vocabulary and advanced spelling abilities. Miraculously, the client is able to express himself better than his peers that have full oral capabilities. This ability proves that the client has a very mature depth of thought.

Since the Cerebral Palsy causes the client to have a very limited range of motion, he can only use his right index finger as his primary way of typing. When typing, the client

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twists his arm inwards, in an inverted motion, towards the medial portion of his body. This unique position causes the client to type unwanted letters. These unwanted letters lengthens the amount of time it takes the client to complete his work assignments. Furthermore, due to the strain of having to sustain this awkward position, the client’s arm easily becomes fatigued. Due to his lack of fine motor control, the client also types in an aggressive manner. Since the client pushes each key very hard, he often holds each key for a duration of time that is longer than necessary. The sustained position of each key causes the desired letter to appear multiple times on the screen. Because this happens, the client is required to constantly edit his typed documents. The constant struggle triggers the client to fall behind in the classroom. This, in turn, causes much frustration. The client is then obligated to lengthen his school day so that he can make up for lost time. The client’s typical day starts at 7:15am and ends at about 4:30pm. The normal school day starts at 8:20am and goes to 2:40pm. The client’s day is 25% longer than that of his peers. 1.2 - Purpose of Project The faculty and staff of Hampton Elementary School would like an assistive mobility device that would allow the client to obtain more independence within his classroom setting. Since the client is quite intelligent, he often appears trapped within his own mind. The client strives for independence and wants to be able to accomplish academic achievements without being dependent upon his aid. If the client were to arrive at school before his aid, he would not be able to begin his schoolwork until someone was available to open his laptop for him. This same principle applies to writing. If no one were to be available to place a pencil within the client’s hand, the client would be physically incapable of writing. The client is also unable to partake in extracurricular activities, such as band, due to his impairment. If the client were provided with a means to obtain a firm grasp and a better range of motion, the client would at least have the opportunity to take part in many diverse activities. Providing an assistive mobility device, in regards to band, would at least allow for the client to play a mallet percussion instrument. While many may view the client’s option to participate in an after school activity, such a band, to be frivolous, one often forgets how many limitations exist for this child concerning the many genres of life.

From an academic standpoint, the client shows much academic prowess and possesses an aptitude for mathematics and linguistics that far exceeds the limitations of his condition. It is essential for a device to be implemented that would allow the client to obtain a greater range of motion so that the client would have the ability to get necessary objects for himself. Since time is a valuable resource in itself, it is a shame that so much is often wasted to the client’s limited mobility. At this point, it seems essential that a device be developed that would allow the client to achieve the academic success that he his capable of while requiring much less effort and constraint. 1.3 - Previous Work done by others 1.3.1 - Products

Exact Dynamics of Netherlands created a device that assists disabled people with severe handicaps to the upper limbs. The device is referred to by the acronym ARM; Assistive Robotic Manipulator. This device compensates for an arm that no longer

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works. The device is mounted to an electric keyboard. It is also capable of receiving inputs from a number of devices including a keyboards, joysticks, or switches. The functionality of input device depends upon the ability of the body part that the customer uses to control it. This device can be used for an assortment of tasks including eating, drinking, cooking, taking medications, brushing teeth, combing hair, and opening doors and drawers. This robotic arm consists of a gripper, which has the ability to clamp at a force of 20 Newtons, and a power supply that works along with the power supply of the wheelchair. Another previous work similar to this project is the “Reacher Arm for Quadriplegics.” This device was created by Mississippi State Engineering Department as a senior design project sponsored by the National Science Foundation. This project attached to a wheelchair and had the capability to retrieve an object up to two pounds of weight, from a variety of positions. This device was comprised two switches; one switch controlled the rotation of the arm to the position of the object and the second switch controlled the device as it clasped on to the object. Finally devices from the National Science Foundation Engineering Senior Design Projects for persons with disabilities were created that effect specific aspects of this current project. First Tulane University constructed the “Hand Helper”. This was a glove-like device which fit the forearm and hand, and contained tongs for grasping. This was made for a client with cerebral palsy. This device operated by balancing the elasticity of grabber and strong finger flexors. The client pulled on the wire loop, which closed the grabber and gave the client the ability to pick up the object.

Another device was the “Feeding mechanism” created by the University of Illinois. This device allowed the client to feed himself. All of the parts excluding the utensil, were enclosed in a protective plastic casing. The device took the food from the bowl, where the spoon was almost vertical. The spoon was then rotated into the horizontal position and it brought up vertically until the utensil was parallel to the client’s mouth. The client then leaned over and took the food into his mouth. Another assistive device created was the “Daily Assist Door Knob Gripping Handle for Individuals with Arthritis”. This device was created in Arizona State to allow the client to grip around doorknobs and turn them by leverage; not by utilizing pronation.

This project is essentially an improved reaching device. There have been many variations of reaching devices in the national Science Foundation Engineering Senior Design Projects for persons with disabilities. One such device was the “Clutching and Gripping Device” made by Arizona State University. For this device their client had a motorized scoter, for mobility and needed an assistive device to grasp and collect items out of his reach. This device eliminated the problem of the client having to keep the prongs closed while moving the object. The device started out with the prongs closed, so when the client squeezed the trigger to open the prongs and then once around the object the client let go and the prongs closed automatically. Another reaching device project was done by the University of Massachusetts called the “Assistive Reach Mechanism”. This device reached objects up to four feet away and lifted up to five pounds. This device had the ability to pick up objects as small as a needle or as large as a can with the gripping claw. Finally also at the University of Massachusetts they created “The Outreach Reaching Aid”. This device increased the strength of the device to pick up

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larger objects, made the trigger mechanism more advanced and had a variable length of the reaching aid, which ranged from 12 inches to 30 inches. 1.3.2 - Patent Search Results

Other objectives of our project related to certain patents found in the U.S. Patent registry. One patent was #06871563, which patents an orientation preserving angular swivel joint that is made up of two members and an angular bevel gear that connects the two members of the joint. Another patent was #06846331 which patents a gripping device which has two parts that move together and can be moved towards each other to grip the device and also have a mechanism to move away from each other and release the object. The gripping action is increased when it is connected to an electrical motor.

2 - Project Description 2.1 - Objective

The purpose of this device is to compensate for a handicapped individual with a severe case of limited mobility within the upper limbs. A device of this nature will be extremely beneficial to the client’s condition especially in an integrated classroom setting. This device will be able to aid the client with the many tasks that most students take for granted. The device will allow the client to retrieve objects such as pencils, pens, rulers, crayons, and various other accoutrements that are consistently utilized in an elementary setting. The device will also assist the client in reaching for his backpack, draped on the back of his wheelchair, and opening his laptop. The device will also aid the client in opening doors so that he will gain the ability to enter and exit various locations independently. The new found mobility will give the client the ability to obtain items the have fallen to the ground.

The robotic arm would also aid the client by providing an array of eating mechanisms. The mechanism will provide the client with the ability to independently retrieve food with a utensil, bring the utensil towards oral portion of the face, and grant the client with the ability to reach the food with his mouth on the utensil. This will give the client independence from his aid and provide him with a more social and interactive lunch amongst his peers.

This apparatus will consist of three joints and a stable base. The arm will be segregated into to three distinct areas allowing for different ranges of motion depending upon the task being performed. These three joints will be located at the base, elbow, and wrist. The elbow joint, with separate the upper and lower arms, will be immobile except for the joints themselves. Between all four joints, the client will be provided with a full 360 degree rotation among the X, Y, Z axes and throughout the three primary planes of motion. Along with range, the device will also be capable of obtaining the basic anatomical motions of flexion, extension, pronation, supination, circumduction, abduction, adduction, opposition, reposition, and rotation.

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Connected to the wrist will be the gripping device. The gripping device will have removable accessories that will correspond to the client’s particular activity. These accessories will snap in and out of an attachment located at the wrist. These attachments will include a fork, spoon, drinking glass, gardening tools, and a default gripper. The gardening tools will be utilized in the client’s fifth grade classroom where the students are currently studying botany as part of their science curriculum. There will also be independent switches that will correspond to the various motions of each specific joint.

This device will be beneficial to any client that has the ability to operate a keypad and joy stick, has a sufficient enough learning ability to comprehend the function of the device, has a strong visual ability, and possesses a desire for independence while striving to explore and utilize the capabilities of the device. The device will all also better the client as an individual by strengthening his self-confidence. It will provide an alternate perspective upon the confined world in which he has become so accustomed to.

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Design Layout of Robotic Arm

Build Robotic Arm

Assemble Pieces

Program Microcontroller

Connect Key Pad

Design Keypad

Obtain Materials

Obtain Materials

Make Keypad

Safety Testing

In the Senior Design Lab

On-Site Testing at Hampton Elementary

Teach client how to operate robotic arm

Give client keypad to practice on

Give product to client

Figure 1: Order of Operations for device creation

2.2 - Methods

Contact client

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The device that will be implemented for this design will be an assistive mobility

device.(Figure 2) This device will consist of a robotic arm with multiple points of rotation. The first point of rotation will occur at the base of the device. This base will contain a mounting and stability device. The base will mount to the end of the arm rest for the client’s wheelchair. The stability device will be used for controlled rotation about the shoulder and will elevate stress on the distal end of the mechanical arm.

Figure 2 – Schematic of Robotic Arm

Knowing that the assistive device will undergo much stress and strain because of constant usage, the material that the limb will be constructed from should be extremely durable. Two durable materials that would be suitable for this application will be steel and aluminum. Both of these materials have a high fatigue resistance and also possess low stress-shielding. The entire base and arm components will be constructed out of an aluminum-steel alloy. This particular alloy was chosen to avoid bimetallic corrosion; corrosion that occurs when two metals are mixed.

The rest of the arm will be constructed out of pure steel. This steel will also be rust proof. Rust proof steel is essential so that the client can use the robotic arm in an outdoor setting. Fiberglass will also be implemented into this design around the joints. Fiberglass is a dense, water-proof material that is a stranger to rust. It is essential that no

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rust occurs within any joints of the apparatus. Due to the nature of the external shape of this device, the assistive arm has the potential to be prone to crevice corrosion from all the various small nooks and crannies that occur on the surface. Crevice corrosion occurs when a stagnant liquid remains in a crevice while the surrounding metal dries out. When this happens, an anodic attack of the metal occurs near the mouth of the crevice and a cathodic reduction of oxygen from the surrounding metal surfaces takes place around the mouth. This reaction can cause undesired results. If a joint were to rust, it could malfunction and potentially produce a safety hazard to the client.

Temperature also plays a critical role in how any mechanical device operates. If the client were to decide to travel between two extreme climates the device should still function without any discrepancies. The device should be able to operate between -20° and 60° Celsius. Also, as a safety precaution, the velocity of the arm should never exceed 10cm/s. For the arm to move at a faster rate, the current to the electric motor would exceed what is deemed safe and could cause harm to the client.

Figure 3 – Schematic of Rotational Motions This device will be designed so that the client can maximize all six degrees of freedom that the human arm is capable of. (Figure 3) At the base, the arm will be capable of rotating 360 degrees about the z-axis. (Figure 9) Once the joint is rotated to the desired position about the z-axis, the attachment between the base and upper arm will have the capability of rotating about either the X or Y axes depending upon the orientation of the

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base. The shoulder joint connection and will mimic the motion of a hinge joint. (Figure 8) The upper arm and lower arm will be connected by the wrist joint. This joint will be capable of rotating about the z-axis at a full range of 360 degrees. (Figure 7) The connection between the gripper and the lower arm of the device is stationary. This connection is for stability purposes only. (Figure 6) Finally, the gripper will be capable of opposition, the grasping motion, and reposition, the releasing motion of an object. (Figure 5) The grippers will be capable of grasping with a force of approximately 3 Newtons. All of these motions will be obtained by buttons and joy sticks located at the base of the arm. (Figure 4) This will make the device easily manageable for the client.

Figure 4 – Joysticks and keypads for controlling the arm’s motion

The keypad for this robotic arm will function similarly to a regular keyboard on a computer except it will only contain the arrow keys. The keyboard uses switches and circuits to translate the signals from the keys into a signal that the computer can understand. The keypad will act as the input device for this robotic arm. Much like on a

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regular computer, the arrow keys will be used to move up, down, and sideways in small increments. In essence, this keypad will function as a mini computer. It will contain its own microprocessor to carry information to and from the robotic device. Part of this keypad will also contain the key matrix. This matrix consists of a grid of circuits. Below each key, the circuit can be opened or closed depending upon how the key is positioned. When the client pushes the key, the circuit will be completed and a small amount of electricity will flow in. Due to the client’s condition, the keypad will be required to have a spring with a greater spring constant, k, in order to produce more resistance to compensate for his gross movements. The greater resistance will prevent the client from holding a key down too long and having the processor in the keyboard interpret that he is continually hitting the keys.

The gripping mechanism (Figure 5) also requires slip free grippers. This is important so the client will not drop any objects he is attempting to move. Objects made of glass are very slippery and can also cause injury to the client if dropped or broken. A good material to place on the ends of the grippers will be leather or rubber. Both of these materials will not only provide a more secure grip on the object, but would also prevent the grippers from scraping the object.

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Figure 5 – Schematic of Gripping Device

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Figure 6 – Connection between Gripping Device and Wrist (Stationary)

Figure 7 – Wrist connection between Upper Arm and Lower Arm

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Figure 8 – Shoulder Joint connection Stability Base and Upper Arm

Figure 9 – Base

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3 - Budget The budget allotted for this project is $750.00. The faculty and staff of Hampton Elementary School also offered to aid any addition funding or resources that the project many require. Below, in Table 1, is a projected estimate cost for the raw materials that the assistive robotic arm requires. The total cost, as of now, remains within the limits of the budget. It is essential to not exceed the limit early on so back-up resources will be available for unforeseen issues. Material Cost Raw Metal $84.39 Electrical Motor $40.00 Power Source $69.99 Microcontroller chip $25.99 Parallax Standard Servo $10.36 Robotics with the Boe-Bot Parts Kit $55.97 Board of Education (Serial) - Full Kit $55.97 Boe Bot Chassis $23.50 Screws $4.00 Nuts $2.30 3 pin single row header $1.50 Servo Gripper & Servo $45.95 Serial I/O Controller $99.95 Bulk Wire $3.39 A/C Adapter $10.00 Total $533.26

Table 1 – Budget 4 - Conclusion

The assistive device will be able to meet most of the challenges in client’s everyday life. The device will be designed to fulfill the tasks without him facing any hindrances due to the lack of muscle activity. While there are numerous products available on the market that serve as an assistive aid for people suffering with such conditions, the Robotic Arm designed is unique to client’s specific condition of Athetoid Quadriplegia. Since there is limited muscle activity in the hands of the client, the controllers of this device are designed to uniquely compensate for his needs. Although devices similar to the one being created are available on the market, the cost of obtaining such a product is phenomenal. This robotic arm will be designed to aid the specific needs that a fifth-grader with limited mobility faces in an integrated classroom.

According to research, Robotic Arms designed for challenged individuals have proven to be valuable. No matter what type of impairment is being faced by the consumer, anyone who has the capability to use a keypad and controller can become more independent. The device will be beneficial to the client since he has the ability to obtain a firm understanding of the device quickly along with an aspiration to be

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independent of his helper. This device will provide the client an opportunity to partake in the simple everyday tasks that many take for granted. The client will also be able to grow as an individual as he discovers all that he will be capable of. Since the client has proven to be extremely intelligent, he will be able to thrive and gain a new perspective on life. Being provided with a means of greater mobility will allow the client to escape from the confined world of dependence that he is currently living in.

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