Achieving Mobility (Calvin College)

Dan Evans, Matt Last, Matt Rozema, and Rob VanderVennen (Calvin College)

ABSTRACT

The project is to design and build a customized electronic wheelchair (hereon referred to as a stroller because of its layout) for a 10-year-old boy customer who has Spinal Muscular Atrophy, a neuromuscular, degenerative disorder affecting his muscle movement. Due to the disease, he prefers to remain horizontally positioned; therefore, the stroller will have a completely horizontal layout. It will have the capability of being manually pushed or controlled electronically. The user interface for the electronic controls will be a single touch button which the user can press whenever the stroller is in the desired directional state. There will be four directional states, which change at a set interval, signified by a series of four LEDs. Also, there will be a camera feeding live video to an LCD for the user to safely navigate the device. The final product will be given to our customer in May of 2011.

INTRODUCTION

The main objective of this project is to design, prototype, and deliver a motorized stroller that will provide the customer with adequate mobility and comfort. The focus of the design will be in the areas of safety, reliability, and ease of use. The user will be able to control the stroller with the touch of his finger and he will see where he is going via an LCD screen that is wired to cameras around the stroller. With two electrical and two mechanical engineering concentration students, this project presents several electrical and mechanical design challenges that are appropriate for this team. Even though this product is specifically designed for a particular customer, it has the potential to benefit individuals with similar disorders. Providing the gift of mobility to otherwise immobile people is the overall goal of this project.

Shown below is the design team (L to R: Matt Last, Rob VanderVennen, Matt Rozema, and Dan Evans) with the customer.

Engineering Team with Isaac

Achieving Mobility Team with customer

PROBLEM STATEMENT

The main focus of our project is directed toward a particular individual. He is a 10-year-old boy who was diagnosed with Spinal Muscular Atrophy (SMA) as an infant. This is a rare genetic disorder that causes his muscles to deteriorate over time. Currently, he has lost virtually all voluntary muscle ability in his body except for the use of his left index finger and slight facial expressions. Unfortunately, he may lose the ability to use these muscles as well but at this time it is hard to say when that will happen according to his doctors. He has two primary means of transportation – a stroller in which he lies down while someone pushes him as well as an electric wheelchair in which he sits up and controls with his finger. Unfortunately, both means of transportation are no longer suitable for him. He has outgrown his stroller and the manufacturer does not make one large enough to fit his growing body. In addition, he cannot use his electric wheelchair for more than twenty minutes due to the amount of strain that it puts on his back and breathing difficulties. After initially meeting the customer, the team knew that this was a project worth pursuing and that this was a great way to make an impact in the community.

APPROACH

Since this team is split between two concentrations, dividing up the work between all four members of the team is important in order to stay organized and on schedule. At the beginning of each week, certain tasks are laid out for each team member to complete over the course of the week. Then at the end of the week, status reports are utilized to analyze the work completed as well as what needs to get done the following week. The three main areas that the work has been divided into are hardware, software, and mechanical.

Hardware

The hardware components are split between Dan Evans and Matt Rozema since they are the two electrical engineers on the team. Tasks were split up based on different skills between the two electrical engineers and their varying abilities.

Software

The majority of the software components will be handled by Matt Rozema. Matt has experience working with software design from an internship and feels that he will be able to handle the design of the software components.

Mechanical

The mechanical components have been divided into major components and will be split up between Rob VanderVennen and Matt Last. Each team member will be responsible for designing, purchasing, assembling, and testing each component. Rob and Matt both have a different set of skills that will be utilized in the design of each component.

RESULTS

Stroller Design and SolidWorks Model

The design of the stroller is completed, and construction of the stroller should be completed by April 20, 2011.  A Finite Element Analysis has been performed on the device in order to ensure that it will not fail under maximum load conditions.  A SolidWorks diagram of the stroller is shown below.

SolidWorks Model

SolidWorks Model of Electric Stroller

Motor Control

The way the wheels will turn is determined by the host controller.  The host controller uses the input from the user interface (LED lights and touch pad) and determines which direction the stroller will move.  There are two motor controllers which are responsible for sending the appropriate power to each motor. The motors then turn the wheels.  The block diagram below shows the hard topology of the system.

Hardware Toplogy

Motor Control System

The directions are forward, reverse, left, and right as well as staying idle, which will be the case the majority of the time.  The videos below show the host controller, motor controllers, motors, and wheels working together on an old wheelchair that was donated to the team.  This first video shows the donated wheelchair moving forward.

This second video shows the donated wheelchair turning left.

Camera and LCD System

The video camera will send the live video feed directly to the LCD screen. The camera will be mounted to the front of the wheelchair so the user knows what is ahead when driving forward.  The LCD will be mounted in front of the user’s face.  The camera will be detachable so that if someone wants to show him something they can point the camera at it.  The camera and LCD system have been set up and work correctly, which can be seen in the picture below.

LCD and Camera

LCD and Camera System

Power Regulation

A circuit was designed in order to make sure each electrical component receives the correct amount of power to it.  The circuit contains an LED to show when power is going to it, an overvoltage limitation, and capacitors for filtering and providing extra current.  The diagram below is the power regulation circuit, which was designed in LTSpice.

Power Regulation

Power Regulation Circuit

DISCUSSION AND CONCLUSION

The delivery design will be specifically designed for team’s customer; however, if the product were to hit the market it would be modified to meet the needs of more individuals. The group has made substantial progress throughout the year, and has logged over 1000 hours of work. We have made substantial progress during these last seven months, and we will need to continue to be diligent in our work in order to deliver the device by May 7, 2011. This product has proven to be a great example of how we can use our engineering education to make a difference in someone’s life. Knowing that this product will touch someone’s life and give them the opportunity to see life in a new perspective is what makes this project so special. It is our goal that by May 7, 2011 our customer will be able to put life into drive and achieve mobility.

COST

Thankfully, we have had a significant amount of expensive components and labor donated to us in order to help out with a great cause.  Ivanrest Christian Reformed Church has significantly supported the financial burden of the project.  Shown below is a list of money we have spent or expect to expend in the near future.

Part Cost
12V 50Ah lead acid batteries $270.00
Adjustable Handle knobs $50.00
Aluminum Shelf (per sq. in) $100.00
Aluminum Tube (per in) $102.08
Backpack Hooks $4.00
Board Video Camera $0.00
Brake Cable $0.00
Brake Calipers $42.83
Brake Handles $0.00
Development Board with LCD $0.00
Electronics casings $0.00
Encasing Gasket $10.00
Fasteners $12.90
Flexible goose-neck tube $30.00
Handle Grips $15.00
Labor (Welding) $2,200.00
LCD Screen $0.00
Main Motor Controller $0.00
Motors $1,600.00
Parking Brake $0.00
Pipe Caps $6.00
Powder Coat $65.00
Power regulators $0.00
Ratchet Strap $15.00
Rubber Handle Bar Covers $10.00
Seatbelt $33.00
Seatbelt mounting bar $18.00
Speed Sensor $15.00
Tie-down hooks $8.00
Touchbutton $77.00
Upholstery Seat $300.00
Website Template $67.00
Wires, cables, connectors $30.00
Contingency (5%) $254.04
Total $5,334.85

ACKNOWLEDGMENTS

There are several individuals and organizations that have helped the team out with the project. A special thanks goes out to the following:

  • Calvin College for providing the team with the resources to design the project as well as funding a portion of it.
  • Professor VanderLeest, the team advisor, for pushing the team and offering advice and criticism wherever necessary. His organization and project management techniques proved to be very helpful in organizing the project.
  • Tim Theriault from GE Aviation, for being the team’s industrial consultant and providing us with contacts at Texas Instruments.
  • Russel Ramsay from Texas Instruments, for donating the development kits and offering his time to help the team through problems.
  • Ivanrest CRC for providing the necessary funding for this project. A special thanks to Carole Pettijohn, head of outreach ministries at Ivanrest, for setting up the donations and making this project possible.
  • Invacare for providing the team with guidance with wiring up the current motors.
  • Greg Bush, electrical design engineer at Gentex, for providing the team with LCD screens and cameras as well as mentoring the team with the camera and LCD screen design.
  • Jim Ebling, manager at Ebling and Son, Inc. Blacksmiths, for donating his time and resources to assist the team in welding and machining the frame.
  • Professor Ribeiro, the professor of Engineering 315, for allowing the team to use class time and resources to design components of the control system.
  • Josh Schroyer, who helped film and edit the videos for the RESNA 2011 Student Design Competition
  • The Business 396 team which consists of Ji Won Choe, Audrey Petrini, Will Richert, Theo Van Hoek, and Peter Wierenga, for providing the team with help on the business plan and financials.

CONTACTS

If you wish you to contact Achieving Mobility you can contact Dan Evans at dan.evans5@gmail.com . His current address is the following:

Dan Evans

1835 Conlon Ave SE

Grand Rapids, MI

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