PROJECT HISTORY & OVERVIEW

 

 

1.1 GATEWAY COALITION PROGRAM BACKGROUND

            The Gateway Coalition is an organization comprising seven institutions dedicated toward advancing engineering education.  Supported by the Engineering Directorate of the National Science Foundation, the Gateway Coalition sponsors several projects, including this multi-university senior design project.  The system developed for this project is a wheelchair-mounted robotic arm to assist paraplegics and quadriplegics in their daily lives.  Three institutions are currently collaborating to develop the robotic arm: Ohio State University, Wright State University, and Sinclair Community College.

            The multi-university project has continued since 1995, and the robotic arm for a wheelchair has been used as a project since 1996.  A brief description of the previous years’ efforts is given in the following sections.  This is followed by the details on the project for the 2000-2001 academic year.

 

1.2 1996-1997 DESIGN

 The 1996-1997 final design is illustrated in Figure 1.1.  This device was a 3 link, 6 degree of freedom device with a transmission system consisting of cables and transmission pulleys.  The purpose of the transmission pulleys was to keep the motors at the base of the robot, thus decreasing the torque on the arm.  Unfortunately, a mistake was made in the initial torque analysis, so inappropriate motors, which were not strong enough to easily move the arm, were selected. Its overall size complicated manufacturing requirements, and the predicted high maintenance costs also hindered the design.

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Figure 1.1 - 1996-1997 Final Design

1.3 1997-1998 DESIGN

A solid model of a design concept proposed by the 1997-1998 Ohio State team is seen in Figure 1.2.  This design featured 5 degrees of freedom, with vertical motion controlled by a lead screw and horizontal motion accomplished by a motor at the elbow joint.  This design differed significantly from the first design in that no cables or pulleys were used, because the motors are mounted directly on each joint (motor-on-joint control).  Lower assembly and maintenance costs were the primary advantages of this design over the cable and pulley system.  Another feature of this design is that it utilized more off-the-shelf parts.  A drawback however, was that the required off-the-shelf components were quite expensive.  It was also questionable whether the structure of the arm was rigid enough to support the torque produced by both the object to be picked up and the motors required to manipulate the arm.

Figure 1.2 – Ohio State’s 1997-1998 Initial Design

 

 

 

The final 1997-1998 design (pictured in Figures 1.3 and 1.4) incorporated a transmission system similar to that of the previous year’s design.  Some of the improvements included the addition of a knuckle joint and a more compact rotating base.  This design was structurally and functionally better than the previous year’s design.  However, it was very expensive due to the large amount of machining required, and it was never mounted to a wheelchair.  Another drawback of this design was that the gripper could only be actuated in one direction.  It was spring-loaded in the open position and closed by a cable, which was wound with a small motor. 

 

 

 

 
 


 


1.4 1998-1999 DESIGN

Figure 1.5 is a solid model of the 1998-1999 initial design. This design utilized motor-on-joint control and square extruded aluminum tubing in an attempt to reduce the complexity and machining costs of the arm. Another advancement was the attempt to control the gripper motion in both directions. Additionally, this was also the first year that the robot was actually mounted to a wheelchair.

Figure 1.5 - 1998-1999 Initial Design

 

 

Figure 1.6 is a photograph of the prototype that was built. One of the main shortcomings of this design was that the gripper was very bulky and could not produce enough force to lift a payload.  The shoulder motor extended about 8 inches from the side of the joint, severely inhibiting the passage of the wheelchair through standard doorways. Finally, although the arm was mounted to the wheelchair, the base rotation failed to function due to both an undersized bearing and motor at the base.

Figure 1.6 - 1998-1999 Final Design

 

 

 

1.5 1999-2000 DESIGN

            Seen in Figure 1.7, the 1999-2000 design utilized six degrees of freedom in the arm and was mounted to a wheelchair.  The large range of motion was made possible by two motors located at the shoulder, controlling the twist and bend motions, as well as a motor controlling the elbow bend.  The arm also featured a three-point underactuated gripper connected to a compact differential gear set, which permitted both twist and bend at the wrist.

            The final design was not without drawbacks, however.  The entire arm assembly was heavy, weighing over 40 pounds, and requiring at least two people to mount the arm to the wheelchair.  Extensive machining also increased the manufacturing costs.  Additionally, the arm could only lift a 1-kilogram (2.2 pound) payload.

Figure 1.7 - 1999-2000 Final Design

 

 

1.6 2000 GRADUATE STUDENT DESIGN

            Ohio State University graduate student Chris Fearon produced a completely enclosed design in the summer of 2000, as seen in Figure 1.8.  His design incorporated 2.5-inch square tubes throughout the length of the arm, and the shoulder bend motor was located within the tubing.  The motor for the shoulder twist rotation was placed beneath a compact mounting plate.  The smaller design was lighter in overall weight than the 1999-2000 design.  The primary drawback to the design was its cost, requiring over $10,000 for extensive machining and fabricating.  Furthermore, mounting to the wheelchair remained difficult due to the two-piece clamping brackets.

Figure 1.8 - 2000 Graduate Student Design

 

 

1.7 MARKET ANALYSIS

            Rehabilitation robotics in general was studied by conducting literature and patent searches.  The patent search did not reveal any existing patents for rehabilitation robotics in particular, but some specific components have been patented such as grippers.  The literature search revealed many interesting facts about the state of rehabilitation robotics today.  These findings are discussed in the following paragraphs.

            The market for such assistive robotic products was found to be somewhat limited, as robots are an alternative only for individuals who may have a deficiency in manipulation ability.  Only about 10% of the population has some sort of handicap, and much less have both lower and upper body mobility impairments.  The simple fact that only those individuals with both upper and lower body handicaps will use the product limits the market.  Those benefiting from a robotic arm must also not be so severely handicapped that they cannot reasonably control a joystick or other input device, further limiting the market.  Therefore, it is estimated that of the approximately 1.5 million people who are confined to electric wheelchairs in the United States, between 100,000 and 500,000 could benefit from a robotic arm based on the type and extent of their disability.  These numbers indicate that there is a market for a rehabilitation robot, even though it may be limited.  Furthermore, if one looks at the number of assistive robotic products sold as compared to the number of people that could benefit from such a product, it is obvious that only a very small portion of these individuals are currently benefiting from rehabilitation robots.  This suggests that there is still a need for such a product if it could be designed to be affordable and efficient.

            Since the product is aimed at individuals who have a deficiency in manipulation ability, the primary focus of such a device is to provide the user with a device that aids them in performing day-to-day manipulation tasks.  Other groups have conducted research to determine the impact on the life of the user by such a robotic device.  A study was performed by creating a profile of an individual with a severe manipulation disability.  This profile was defined as a person having sedentary strength and no use of reaching, handling, and fingering.  The Dictionary of Occupational Titles, which defines all jobs in terms of different levels of manipulation abilities, was then used to find the number of possible types of jobs that an individual with this particular profile could hold.  The study found 40 job descriptions that this type of individual would be able to perform.  These jobs consisted of primarily professional, technical, and managerial jobs.  The study then made the assumption that with the aid of an assistive robotic product, the same individual would marginally increase their manipulation ability.  The profile was redefined as a person having occasional and then frequent use of reaching, handling, and fingering skills.  An individual with occasional use of these skills was then shown to be capable of performing approximately 300 jobs.  The individual with frequent use of these skills was shown to be capable of performing over 1100 jobs.  The results of this study alone demonstrate the impact a rehabilitation robot would have on the lives of potential beneficiaries and validates the attempt to design such a device.

            There have been a number of attempts thus far to create a rehabilitation robot that is both affordable and effective.  A list of such products is shown in Table 1 below.  Only three of the commercial endeavors shown in the table (Rehab Robotics, Exact Dynamics, and Rehabilitation Technologies) are actively marketing and supporting their product.  The Raptor, by Rehabilitation Technologies, began sales in 2000 and has not had enough marketing time to measure its sales performance.  As can be seen from the table, many of these products have not been successful, and no one product has had overwhelming success.  There are many factors which contribute to the failure of these previous attempts, including poor user interface, isolation from clinical reality, the cost benefit is not justified, lack of portability, poor organization, and lack of capital funds.  All of these factors must be taken into serious consideration when attempting to design a rehabilitation robot. 

Table 1.1 – Previous Attempts at Marketing Robotic Arm

Product Name

Country

Company

Type

Approx. Cost

Approx. # Sold

Where Sold

Prab

 

PRAB

Vocational

 

 

Worksites,

Command

USA

Robotics

Workstation

$48,000

20

Rehab Centers

DeVar

USA

Independence

Vocational

$100,000

3

Clinical

 

 

Works, Inc.

Workstation

 

 

Evaluation

Manus

Nether-

Exact

Wheelchair

$35,000

50

Dutch

 

lands

Dynamics

Mountable

 

 

Users

Handy 1

UK

Rehab

Mobile Base,

$6,000

140

Individual

 

 

Robotics

Feeding Unit

 

 

Users

 

 

Kinetic

Wheelchair

 

 

Clinical and

Helping Hand

USA

Rehabilitation

Mountable

$9,500

10

Research

 

 

Instruments

 

 

 

Evaluation

 

 

Papworth

Wheelchair

 

 

Clinical and

Papworth Arm

UK

Group

Mountable

$8,000

5

Research

 

 

 

 

 

 

Evaluation

 

UK,

Oxford

Vocational

 

 

Clinical

RAID

France,

Intelligent

Workstation

$55,000

9

Evaluation

 

Sweden

Machines

 

 

 

 

 

 

Arlyn

Education,

 

 

 

Arlyn Arm

USA

Works

Vocational

$30,000

0

 

 

 

 

Workstation

 

 

 

 

 

Robotic

 

 

 

 

Sidekick

USA

Assistance

Mobile Base

 

0

 

 

 

Corporation

 

 

 

 

Raptor

USA

Rehabilitation

Wheelchair

$11,950

N/A

Unknown

 

 

Technologies

Mountable

 

 

 

Robotic

 

Neil

Vocational

 

 

Clinical,

Assistive

Canada

Squire

Workstation

$23,000

7

Rehab, and

Appliance

 

Foundation

 

 

 

Industry

 

            It is also worth noting that the price and performance of a robotic aid is linked to the complexity of its design.  For example, fewer degrees of freedom will lead to a device with less capability.  However, this fact alone does not mean that simpler robotic aids will not be useful.  The important characteristic is whether the robotic aid will meet the needs of the consumer.

 

Table of Contents

Acknowledgements

Section 2: Coalition Dynamics