Fall 2016 Prosthetic Hand: Interface Control Document
Mission, Systems, and Test Engineer – Mia Lai
Table of Contents
System Overview
As defined in the mission profile, the Upper-Limb Prosthetic System shall allow a soldier to eat a McDonald’s Quarter Pounder with Cheese meal. The system will be designed to replicate functionality of a human upper limb system. The program objective is to effectively control the Upper-Limb Prosthetic system without the use the other hand. In order to complete the mission profile, the Upper-Limb Prosthetic System will be manufactured as two separate systems, including a Prosthetic Arm and a Prosthetic Hand. These two systems shall work in conjunction and function as a single unit to feed the soldier a McDonald’s Quarter Pounder with Cheese Meal.
System 1: Prosthetic Arm
System 2: Prosthetic Hand
The Prosthetic Arm system will be responsible for the fabrication of the forearm unit, including a vertical range of motion localized at the elbow, and a bicep component. The control method for lifting of the arm is via electromyograph signals from bicep muscles in the upper arm. In conjunction with the Prosthetic Hand, the system would have the ability to enable a soldier to consume a fast food meal, with up to a 20 minute duration.
The Prosthetic Hand system will be responsible for the fabrication of the hand unit, including the fingers and palm, and wrist/forearm attachment. The control shall include wrist rotation capability and hand grasping capability. In conjunction with a Prosthetic Arm, the system would be able to the soldier to consume a fast food meal, with up to 20 minutes
Concept of Operation and Interface Requirement
This Interface Control Document provides an outline of interface requirements imposed on the participating systems, including the Prosthetic Hand and Prosthetic Arm systems. It will describe briefly the concept of operations and functionality related to the interface of the two systems. Further information on interface requirements will be described the subsequent sections.
Upper-Limb Prosthetic Systems Weight and Size Allocation
Weight of a prosthetic device is a key factor contributing to interface discomforts and muscular fatigue in prosthetic users. The Upper-Limb Prosthetic System will be designed as close to a human upper limb as possible. The overall weight of the Upper-Limb Prosthetic System shall be no heavier than 4.0 ± 0.61 kg (8.82 ± 1.35 lbs) to match with the human average weights for an upper arm, forearm, and hand in combination [1], [2]. Including the bicep, the weight allocation for the Prosthetic Arm is 1.73 ± 0.61 kg (3.82 ± 1.35 lbs). Extending from the elbow down however, to the tip of the fingers, the forearm, hand and food should not exceed a combined weight of 6.83 lbs, to correspond with a torque of 10.634 NM at 35 cm for our stepper motor. From this requirement, the weight allocation for the Prosthetic Hand is 1.35 ± 0.23 kg (2.97 ± 0.5 lbs). The system shall be capable of picking up a maximum of 0.69 kg (1.52 lb) of food.
The Upper-Limb Prosthetic System design will replicate the size and shape of a human upper limb system. The overall length of the system should not exceed a length of 76.51cm ± 0.37cm (30.12 in ± 0.14 in), from the tip of the middle finger, to the end of the shoulder. The length of the forearm (inclusive of the Hand), measured from the elbow to the tip of the middle finger shall be of 35 ± 5 cm (13.78 in ± 1.55 in). From this allocation, the length of the hand measured from the middle finger tip to the end of the wrist/forearm interface shall be 269 ± 13mm (10.6 in ± 0.51 in).
Space Accommodation
The Arm in agreement with the Hand will provide an availability of 83 mm (Length) x 64 mm (Width) x 38 mm (Height) (3.25 in x 2.5 in x 1.5 in) space allocation for the Hand to store MCU and PCB boards.
Functional Allocation
The Prosthetic Hand will be responsible for grasping food items and rotation capability of the wrist to fulfill the mission. In conjunction with the Prosthetic Arm, the Prosthetic Hand will include a rotation capability at the wrist base to grip different food items depending on the position of the hand to the food item. The maximum angle of rotation shall be 90 degrees up or down from the neutral position of the hand. The hand shall also be designed with three different gripping patterns to grip three different food items. These food items can be as small as a French fry or as big as a medium cup of soft drink or a quarter pounder burger. In conjunction with the Hand, the Arm will include vertical movement of the forearm at the elbow to lift the Hand and respective a food item. The maximum range of the motion will be 60 degree up and 90 down from the horizontal line.
Control Mechanism and Data Transfer
The Prosthetic Hand and Prosthetic Arm systems will be controlled independently. The Hand will operate based on the Arduino Micro microcontroller while the Arm will operate based on the Teensy 3.2 microcontroller. No data will be transferred between these two systems. The Hand will receive input signals from a foot control panel to control movement of the fingers and the rotation of the wrist. The Arm will receive electromyograph (electric potential) input signal from a human upper arm muscle to control the movement of the forearm.
Power Transactions
The Prosthetic Arm and Prosthetic Hand will be energized via a common powertrain, supplied by a 1600-mAh, 14.8-V (4S) Lithium-Ion Polymer (LiPo) battery stored in the bicep of the Prosthetic Arm system. From this power source, the Prosthetic Hand will be allowed a current allocation of 3500 mA on a regulated 12V supply and 1000 mA on a regulated 5V supply respectively. A total of three 22-AWG stranded wires will be used for 12V, 5V, and ground to transmit power between the Prosthetic Arm and Prosthetic Hand. Two ends of wires will be connected through a screw terminal block (rated 20 AWG) at the printed circuit boards of the Prosthetic Arm and Prosthetic Hand respectively. Through housing the power supply, the Prosthetic Arm will be responsible for providing power to the Prosthetic Hand, and therein by the Upper-Limb Prosthetic System, in such a way that enables the system 20 minutes of operation.
Mechanical Interface
The Hand system and the Arm system will have mechanical interface at the wrist/forearm interconnection. Wrist/ Forearm attachment integrates the Prosthetic Arm and Prosthetic Hand as a component of the Upper-Limb Prosthetic System. The Prosthetic Hand will be responsible for allocation of the wrist attachment. The respective systems will be joined through a squareshaped mounting interface consisting of 4 screws of 4M (4-mm diameter), and dimensions of 76.2mm (length) X 76.2mm (width) ± 12.7 mm margin (3 in x 3 in ± 0.5 in margin). In addition, the design of the mounting interface will consist of a hollow center, allowing the Prosthetic Arm to feed power cables to the Prosthetic Hand in such a way that they are not operationally inhibited by the Prosthetic Hand’s rotation. Also in agreement, the Prosthetic Hand will be responsible for ensuring its own cabling and communication to their MCU/PCB components, which are allotted physical volume allocation in the forearm section of the Prosthetic Arm, for spacing purposes.
Besides, the Upper-Limb Prosthetic System and the soldier’s body will have an interface at the soldier’s upper arm. The Prosthetic Arm system will be responsible for connection between the Upper-Limb Prosthetic System and the soldier’s upper arm. The interface between the UpperLimb Prosthetic System and the soldier will be shoulder mounted.
Aesthetics
The Prosthetic Arm and Prosthetic Hand will coordinate sleeve and glove covers respectively, to have a matching outer appearance such that the Upper-Limb Prosthetic System does not attract unwarranted public attention to the user. Currently, a vacuum-form technique, in which heated plastic is stretched onto a mold and then given form via vacuum application, is being explored as a potential alternative for a surface cover to both the Prosthetic Arm and Prosthetic Hand components of the Upper-Limb Prosthetic System.
Processing Schedule (Tentative)
The Prosthetic Hand, in conjunction with the Prosthetic Arm will have their respective systems ready for integration by a tentative date of 11/19/2016.
Safety
The Prosthetic Arm will implement an electronic kill switch within its circuitry, giving the user an option to disable the power supply to the Upper-Limb Prosthetic System, including the Prosthetic Hand, in the case of a perceived emergency situation or safety concern.
Noise
The Prosthetic Arm and Prosthetic Hand will work together to maintain operation of the UpperLimb Prosthetic System below an estimated noise level of 60 dB, as measured by the Noise Expert, LLC, in their “Noise Analysis Study for a Proposed McDonald’s Restaurant” in Tucson, Arizona [3]. The respective teams will go out onto the field in an experiment, to obtain actual noise level data across various times at the local McDonald’s facility, to better obtain a benchmark noise guideline for operation of the Upper-Limb Prosthetic System.
Qualification Methods
Approvals
The Interface Control Document has been written on agreement between the Prosthetic Arm System and Prosthetic Hand System. Approvals for the Interface Control Document:
Prosthetic Arm System
Project Manager: Carolina Barrera Date: 10/31/2016
Prosthetic Hand System
Project Manager: Kimberly Younger Date: 10/31/2016
Records of Change
Specification of this document is subject to change. A summary and an explanation of changes between the approved versions of this document and a new agreement will be submitted for approval as a supplemental of this document.
Revision 1: 11/19/2016
2.6 Mechanical Interface
The Hand system and the Arm system will have mechanical interface at the wrist/forearm interconnection. Wrist/ Forearm attachment integrates the Prosthetic Arm and Prosthetic Hand as a component of the Upper-Limb Prosthetic System. The Prosthetic Hand will be responsible for allocation of the wrist attachment. The respective systems will be joined through a square-shaped mounting interface consisting of 4 screws of 4M (4-mm diameter), and dimensions of 76.2mm (length) X 76.2mm (width) ± 12.7 mm margin (3 in x 3 in ± 0.5 in margin). In addition, the design of the mounting interface will consist of a hollow center, allowing the Prosthetic Arm to feed power cables to the Prosthetic Hand in such a way that they are not operationally inhibited by the Prosthetic Hand’s rotation. Also in agreement, the Prosthetic Hand will be responsible for ensuring its own cabling and communication to their MCU/PCB components, which are allotted physical volume allocation in the forearm section of the Prosthetic Arm, for spacing purposes.
Besides, the Upper-Limb Prosthetic System and the soldier’s body will have an interface at the soldier’s upper arm. The Prosthetic Arm system will be responsible for connection between the Upper-Limb Prosthetic System and the soldier’s upper arm. The interface between the Upper-Limb Prosthetic System and the soldier will be shoulder mounted.
Revision 1: 11/19/2016
2.6 Addendum to 2.6 Mechanical Interface
“The respective systems will be joined through an “integrated piece” consisting of 6 M3 screws (3-mm diameter) (Figure 2) and allocated up to 20 cm ± 2 cm from the center of the elbow to the wrist. Within this structure, the responsibilities of the Prosthetic Arm will conclude at the acrylic holster end, including the holster and mounting for the PCB of the Hand, whereas the Prosthetic Hand is responsible for the areas allocated for their slip ring and wrist servo respectively (Figure 1).
Figure 1: “Integrated Piece” Demarcations (Orange)
Figure 1: Visual Compartmentations of Integrated Piece
Approvals for ICD Revisions 1 and 2:
Prosthetic Arm System
Project Manager: Carolina Barrera Date: 11/19/2016
Prosthetic Hand System
Project Manager: Kimberly Younger Date: 11/19/2016
References
[1] HHS Public Access. Military Services Fitness Database: Development of a Computerized Physical Fitness and Weight Management Database for the U.S. Army. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2761744/table/T1/
[2] Tözeren. Human Body Dynamics – Classical Mechanics and Human Movement. Table A2.3. retrieved from http://ayurvedavignan.in/freeEbooks/Human%20Body%20Dynamics%20- %20classical%20mechanics%20and%20human%20movement.pdf
[3] Noise Analysis Study for a Proposed McDonald’s Restaurant. Retrive from https://www.tucsonaz.gov/files/pdsd/McDonalds_Tucson_Noise_Report.pdf