MIME Senior Design Clinic
Fall 2007
September 13, 2007
Project Proposal:
Device to Assist in Buckling a Seatbelt
2007-04-10
Team Members
Keith Knippen – Group Leader
Chris Miller – Technical Liaison/Web Page Specialist
Michael Baiz – Purchasing Agent
Faculty Advisor
Dr. Efstratios Nikolaidis
Client Advisor
Ms. Jill Caruso, The Ability Center of Greater Toledo
Project Sponsors
The National Science Foundation
The Ability Center of Greater Toledo
Device to Assist in Buckling a Seatbelt
Table of Contents
SectionPage
Executive Summary3
Introduction and Project Description3
Proposed Methodology4
Work Plan and Project Deliverables10
Budget12
References13
Executive Summary
The objective of this project is to design, analyze, build and test a device that will assist the client, who has cerebral palsy, in buckling his seatbelt. The client cannot easily buckle he seatbelt because of two factors: He cannot reach the seatbelt tongue (male connector) end and he has trouble lining the tongue with the buckle (female connector) when latching them together. The proposed solution is to design a working system with two main components. The first component is a grab handle attached to the seatbelt to make it easier to pull forward the tongue end of the seatbelt. The second component will possess a seatbelt extension containing a “funnel” to assist in lining up the tongue with the buckle by putting it in a better position. This will not only make the process of latching the seatbelt easier for the client but it is a simple design that can be easily removed from the car in the case of a driver change.
Introduction and Product Description
The client, Tim, needs a device that would assist him in buckling his seatbelt. Tim cannot buckle his seatbelt because he has cerebral palsy. The term cerebral palsy, better known as CP, refers to any one of a number of neurological disorders that appear in infancy or early childhood and permanently affect body movement and muscle coordination but don’t worsen over time. Even though cerebral palsy affects muscle movement, it isn’t caused by problems in the muscle or nerves. It is caused by abnormalities in parts of the brain that control muscle movements. The most common are a lack of muscle coordination when performing voluntary movements; stiff or tight muscles and exaggerated reflexes; walking with one foot or leg dragging; walking on the toes, a crouched gait, or a “scissor” gait; and muscle tone that is either too stiff or to floppy. [1]
As noted earlier in the paper Tim cannot easily buckle he seatbelt because of two main factors: He cannot reach the seatbelt tongue end located behind his left shoulder to pull it around his body and he has trouble lining the tongue with the buckle when latching them together. Because of these factors he does not wear his seatbelt at all. On the other hand, Tim has no problems with the tension in the seatbelt while bringing the seatbelt around him. Tim has also made aware to the team that his right hand is his good hand and he would like all interaction, if possible, with the system to be with that hand.
Personal safety is the biggest reason this project is being performed. Government studies have shown that seat belts, when worn, reduce the risk of death by 45% and serious injury to front seat occupants by 50%. [2] It is crucial that a design is made to Tim’s preferences with overall safety in mind. Due to Tim’s work responsibilities he is on the road almost every week on long trips not including personal trips. These trips are all without a seatbelt because it is too difficult for him to buckle. This project is very important to complete because it makes his life that much safer.
After looking at a variety of designs the best one was picked based on Tim’s requirements using the house of quality found later in the paper. The main requirement like most designs is that this device is safe because the seatbelts only function is for personal safety. Tim also wants a design that is easy to use because there is a concern if it is not easy to use that he might continue not using his safety belt. He wants a device where are no permanent damages to his car current car, a 2000 Chrysler Concorde. He does not plan on keeping his car forever so he wants a device that can be easily removed. Once he sells his car he wants to be able to put it in his new vehicle, he wants something that is universal. Tim would also like something that isn’t really complicated and something that is reliable.
Tim knows a lot of people that has his same issue in buckling his seatbelt that could also benefit from this device. Learning through the client that this issue was present with many people, research was conducted to see if there are any current products that could be used. A comprehensive search over the internet for possible devices was done. Some of the better design that would work with the application is included in the next section.
Proposed Methodology
Vehicle dynamics, human safety, and environmental interaction all present challenges in designing a device to assist an individual with buckling his seatbelt. The interior of a vehicle is isolated from the road, yet it has been designed as a single system to handle vehicle motion and vibration. Car manufacturers spend millions of dollars developing and testing safety belts specifically for each vehicle to maximize human comfort and protection. While the interior of a vehicle is normally a contained environment, external forces resulting from collisions can cause problems inside the vehicle.
While the process of buckling a seatbelt is a simple task to most users, people with disabilities that limit muscle coordination and control find the task more challenging and difficult. The design team wanted to approach the challenge from three completely different views as to optimize the variation in idea development. The team looked at mechanical systems, electric motors, new devices, manual operation, and several other options that would be effective and safe in the environment. From the brainstorming, the design team decided on three approaches:
1. Automatic Seatbelt
2. Seatbelt Retraction Device
3. Manual Two Piece System
1. Automatic Seatbelt
The design team’s first step was to investigate and evaluate current solutions on the market and possible variations suitable for the application. The high complexity, low interaction design involves an automatic seatbelt, similar to those found in vehicles in the early 1990s. This design was conceived to eliminate the human interaction in the buckling process.
The intricate system would require adaptation to the Chrysler Concorde since it did not originally have this design, where a rail and pulley process would be implemented around the door frame. An electric motor would be built into the sidewall of the vehicle or in the dash to control the movement of the buckle and latch.
Figure 1: Automatic Seatbelt Placement
Figure 2 is an example of the latch and pulley system that would operate in the built in track. Since the design has already been introduced as OEM product, the goal is to develop a custom system for vehicles that do not currently have the feature. The design scope could be expanded to include the lap belt with a second rail and latch, which currently would require the user to manually operate this belt.
Figure 2: Automatic Rail System
The automatic seatbelt mechanism allows the design team the sturdiest, most rigid design with no interaction for the shoulder belt. The automatic seatbelt in its current design would still require the user to buckle the lap belt, a task the client would prefer not to do. The system cannot be moved from vehicle to vehicle and would require extensive modification of the doorframe and dashboard. Because of this electric motor, a controller and power source would be needed to operate the motor, further extending the material and development costs.
2. Seatbelt Retraction Mechanism
The client preferred the system to be easy use and not require vehicle modification, a peripheral device was devised to solve the issues regarding reaching the buckle and finding the latch. Since the methods used to buckle a seatbelt can be complex and especially difficult for individuals with disabilities. To simplify the entire process, a seatbelt retraction mechanism permanently attached to the buckle could be employed.
Figure 3: Seatbelt Retraction Device
The user would only be required to grab the mechanism upon entering the vehicle, and then the device would retract to the point where it can be attached to the buckle at the base of the seat, depicted in Figure 3. The retraction can either be accomplished using an electric motor as shown above or a loaded spring controlled by a release mechanism. The retraction would occur to the location of the latch and draw the buckle to its destination, allowing the user to lock it into place.
Figure 4: Retraction Device Seat Placement
The seatbelt retraction device is automatic once it is attached in place, which allows the client buckle his safety belt with minimal interaction. The device is unlike any available on the market, but is moderately difficult to function because it requires the user to introduce new steps when entering and leaving a vehicle. Since it is fully removable and applicable to most vehicles, it meets his preferences of minimal installation. The design team has decided that the device is somewhat cumbersome for the action that it replaces, since it requires cables drawn across the user’s body while retracting the belt buckle. It could become difficult to latch and unlatch the belt buckle due to the size of the mechanism and its primary function. A mechanized system such as this would require a battery power supply, further adding to the cost and compromising efficiency and user functionality.
3. Two Piece System
The team’s next design was a departure from the previous attempts to accomplish all of the client’s goals with one device. A two device system would allow utilization of the individual’s strengths and develop a solution for the weaknesses. We would be easy to find and pull the buckle by attaching a handle, depicted in Figure 5.
Figure 5: Grab Handle on Market [3]
The client wants to determine that this is sufficient for his needs. The team will be working to modify the existing design or develop a different system depending on the client’s preferences. The design team has been working on designs for alternate approaches depending on what works best for the client. The existing design requires that the user switch hands to grab the buckle due to the design, something that the client expressed concern with. An alternative approach would be to bring the buckle out from the door frame into a position at which the user can grab the buckle, pull it across his or her body, and buckle it with one complete motion.
The next device in the system would include a seat belt extension consisting of an existing buckling mechanism attached to a buckle machined to match the existing latch. This will allow the extension to attach to the existing latch without modifications to the vehicle and allow for quick removal when switching drivers or selling a vehicle. A sketch of the extension, variable design ideas, and the funnel-type mechanism to assist the user with finding the latch with the buckle are represented in Figure 6.
The funnel-type mechanism will direct the motion of the user with the buckle in his or her hand to the latch. Because of the client’s disability and the design of the seatbelt buckle, he has difficulty directing this motion which prevents him from safely operating his vehicle.
The design team used the House of Quality to analyze the three designs developed during brainstorming against the features that are most important to the client. The results of the analysis can be compared in Figure 7. The House of Quality results have shown that the third design, Two Piece System, is the best choice.
Work Plan and Project Deliverables:
To ensure that all stages of the senior design project are completed, the group has developed a work plan and a timeline. The work plan outlines the duties of each member of the group. The group leader for this project is Keith Knippen. His responsibilities include scheduling and coordinating group meetings and making sure all deadlines are met. He is the primary contact for the client and client advisor. He is also responsible for submitting the weekly progress reports. The technical liaison and web designer is Chris Miller. Chris, as the technical liaison is responsible for making sure all engineering drawings and solid models are correct. He will also submit drawings to the machine shop supervisor, John Jaegly, and maintain contact with him to assure the completion of desired projects. Chris, also being the web designer has the responsibility of designing the group’s web page with all relevant information and documents. Mike Baiz is the purchasing agent. As the purchasing agent Mike will be responsible for keeping track of the project budget, as well as keeping in contact with Ms. Carrie Schonter. When it comes time to purchase material and equipment he will provide her with the necessary purchase requisitions. Mike is also responsible for making sure all the material selected are within the limits of the budget.
Due to the time constraints of this project a timeline has been created and must be followed in order for completion of the project by the desired date. A detailed timeline for completion of various tasks is shown in Figure 8.
The group anticipates meeting with the client and seeking input on a regular basis throughout the design and build phases of the project. Weekly meetings with the group and faculty advisors have been set for Tuesday mornings from 10:00 a.m. to 11:00 a.m. The client advisor, Jill Caruso will also be present at these meetings. These meetings have been set to discuss the progress of the project. The faculty advisor will also assist in engineering and design help.
Figure 8: Timeline
Project Budget
A proposed budget has been put in place in order to give the group an idea of the necessary funding for this project. The budget includes having the client experiment with two existing grab handles that are on the market. If he does not like the design of these more money is included in the budget for a new or modified design. For the extension piece of the design material for the steel bracket and funnel is included. The cost of the machining of these is donated by the University. Finally, the budget includes money to purchase existing seatbelt, used ones from the junkyard are adequate, to modify and/or experiment with. Table 1 shows the proposed budget with the estimated cost of each item. The total estimation is $285 for the entire project.
Table 1: Proposed Budget
References
[1] - Proposed Projects for MIME Senior Design Clinic Packet
[2] -
[3] -
2007-04-10 Device to Assist in Buckling a Seatbelt