Goals of the project
Our group wanted to choose a project which would solve a major problem affecting the lives of many. After brainstorming, we chose to design and build a device capable of augmenting the grip of a variety of users. Prospective users include the elderly as well as individuals with physical and mental restrictions on movement, such as those affected by stroke, brain damage, or carpal tunnel syndrome.
Nature of the Collaboration
Group members were divided into functional integration (CEO), technical integration (COO), project manager, control systems team, manufacturing team, and budget and research team. Each team member had an assigned job that he/she does. The group met on a regular basis to update each other and work on the project. Moreover, all of the team members were involved when manufacturing and assembly started.
The project requires 3D Modeling on SolidWorks, project management, motor assembly and control logic design, MasterCAM for CNC machining parts, cost estimation, and 3D printers for prototypes. Each member contributes his/her skills including project management, mechanical design, stress analysis, manufacturing processes, and electrical engineering.
Throughout the course of this project, our group utilized a wide range of product development skills including designing, machining, and budgeting as well as project and personnel management.
The tools and equipment that are used in the project are:
- 3D printers for making prototypes
- Laser cutter for the acrylic Electronics Case
- 3 axis Vertical mill CNC machine to cut parts
Our group wanted to choose a project which would solve a major problem affecting the lives of many. After brainstorming, we chose to design and build a device capable of augmenting the grip of a variety of users. Surveys and market research have shown that a majority of these prospective users have difficulty maintaining grip and would therefore benefit from such a device. This data was used to screen various design metrics and determine end goals for our design. Our design attempts to replicate the human hand’s anatomy and aims to be lightweight, safe, and ergonomic.
After discussing a conceptual idea of the desired outcome and creating sketches, CAD software was used to model the assembly. Specifications were generated for the materials, mechanical properties, and power required and a BOM was created including all necessary components. While designing, we considered design for manufacturability and assembly and solved problems that could possibly arise later on.
The intelligence behind this device is a control system that uses a flex sensor in the thumb to recognize when the user is initiating a grip. This communicates with the motor which varies its speed and range of motion to match the needs of the user. The platform which houses the circuitry and motor was fabricated using a 3D printer. A glove was purchased and artificial tendons run through channels sewn into the interior of the glove. Padding and shielding were then added to maximize comfort and safety.
The major milestones are its programmable microcontroller, its natural gripping mechanism, its ergonomic design, and manufacturability. The microcontroller has been programmed with a failsafe code that will not allow the AGR to operate to the point of hurting the operator. The mechanism by which the AGR achieves the gripping motion is very natural because it uses the operator’s fingers as the frame itself about which it applies a torque to cause the fingers to curl.
The development of our idea is not unique. The challenge is how to create a low cost, smart device that can provide the comfort and ease of use expected from a product that is placed on a person's hand. The design of the Assisted Gripping Rig (AGR) started with a goal of developing an orthotic device. The integration of technology into our daily lives spurred our design team to consider the development of orthotics as an aide to grant greater freedom to individuals limited by happenstance and the natural deterioration of bone and sinew. With the numerous advances in the area of robotic assisted walking, little attention has been focused on the development of hand aids beyond passive restraints and exercises. For these reasons the team decided to build an assisted gripping rig.
To accomplish this goal, the AGR design team applied a number of engineering management and project development theories to the development approach. The team applied concurrent engineering, rapid prototyping, and cloud communications to better facilitate time and effort.
Team members designed, researched, and prototyped models of the AGR all at the same time. While this did lead to confusion at times, the ability to rapidly prototype allowed the group the unique ability to review the failures of each system. Cloud communication further facilitated the orderly documentation and clear agenda for development.
We were successfully able to reduce all critical mechanical properties of the AGR by at least 50%, which shows an immense improvement in the safety factor of the AGR for the user. We were able to maintain similar torque characteristics compared to the “Tendon Design” Prototype, while reducing the volume of the motor by 90.1%, the weight of the motor by 94.0%, and the weight of the overall AGR by 52.5%. Even though Table 6.2 shows 162.75 oz-in of torque compared to the 58.9 oz-in of torque in the current design, we were only supplying 3V to the motor in the “Tendon Design” Prototype, so that its torque characteristic was closer to that of the motor currently inside the RTM AGR. This ceiling of almost 4 lb-in. of torque is in itself a safety factor such that the motor cannot harm the user’s hand at maximum power output.
Innovations, impact and successes
The highlights of the AGR are its programmable microcontroller, its natural gripping mechanism, its ergonomic design, and manufacturability. The microcontroller has been programmed with a failsafe code that will not allow the AGR to operate to the point of hurting the operator. The mechanism by which the AGR achieves the gripping motion is very natural because it uses the operator’s fingers as the frame itself about which it applies a torque to cause the fingers to curl. Additionally, the AGR is teeming with ergonomic design choices. From an armlet that is designed about the contours of a human hand, to a low profile housing for the components and an easy-to-wear strapping system, we are certain that the AGR has the smallest learning of any product in its category. Finally, from a manufacturability standpoint, the AGR can be produced in high volumes; its production volume will vary inversely with its price since only 18% of its BOM is manufactured and all other parts are COTS, which can be purchased in large batches and lower price points.