1. A Radio Frequency IDentification (RFID) Prosthetic Control System
Andrew Butler1,2, Walker Arce1,2, Jorge Zuniga Ph.D.1
1Department of Biomechanics, University of Omaha, NE, USA
2Department of Electrical and Computer Engineering, University of Omaha, NE, USA
ABSTRACT
RESULTS
METHODS
Printed Circuit Board: A printed circuit board that fits the footprint of the prosthetic arm was developed utilizing EAGLE EDA that incorporates all necessary components from the block diagram for the system. The PCB is a two layer board that measures 1x2 inches and incorporates two PQ12 motor connectors.
Software: The Arduino development environment was used to develop the software as the microcontroller was compatible with this software. AVR Studio 7 was used to program the device along with an AVR ISP MKII.
Power Testing: A 30V 10A power supply was used to perform power testing along with a TekPower USB multimeter to collect the current measurement results. A Matlab script was developed to simulate multiple grip events over a period of time to be able to capture the battery life of the device over a period of use. In addition the battery life of the device on multiple sized lithium polymer batteries was calculated using this script.
Cost: The developed device was designed to use low cost components that can be easily integrated into a small footprint. The components were also sourced to allow for easy purchase of the bill of materials in the United States.
Item classification and tagging in embedded systems has become ubiquitous in our society due to radio frequency identification (RFID) and the cost has dropped significantly for hardware that can interact with these devices. Due to this, possibilities in the realm of prosthetic control systems opens up for dynamic grip selection without user intervention. This study focuses on the development of a device capable of this functionality that is compatible with the prosthetics designed by Dr. Zuniga and his research team.
The printed circuit board (PCB) was designed using the EAGLE EDA package and incorporates a lithium polymer battery with a charging circuit, a dedicated powers supply, motor drivers, microcontroller, and a Melexis 125kHz RFID transceiver. This is shown in figures one and two.
The obtained power consumption results were analyzed for six different lithium polymer capacities and for a varying number of grip events in a twelve hour period. The battery life of the device is then calculated using a standard battery life equation.
The data collected during this study is shown below and was analyzed using the aforementioned Matlab script.
Battery Life (Hours)
Number of Grip Events in a Twelve Hour Period
Battery Sizes (mAh)
250
500
1000
2000
3000
4000
5000
6000
7000
8.96
5.81
3.45
1.89
1.31
1.00
0.80
0.68
0.58
400
14.33
9.29
5.52
3.03
2.09
1.59
1.29
1.08
0.93
17.91
11.62
6.90
3.79
2.61
1.99
1.61
1.35
1.16
1200
42.99
27.88
16.55
9.09
6.27
4.78
3.86
3.24
2.79
71.65
46.47
27.59
15.15
10.45
7.97
6.44
5.40
4.65
2500
89.56
58.08
34.48
18.94
13.06
9.96
8.05
6.75
5.82
Grip Events
Average Current (mA)
250
19.54
500
30.13
1000
50.75
2000
92.38
3000
134.00
4000
175.70
5000
217.50
6000
259.10
7000
300.80
INTRODUCTION
MATERIALS
As electronics continue to reduce in size and cost, possibilities are emerging for the creation of new prosthetic modes of control with integrated control circuitry [2]. With the proliferation of surface EMG (sEMG) control systems in prosthetics, there are limitations for users as sEMG control system can be taxing on the user’s affected limb and cause fatigue from use [4]. In addition, commercial devices can be too costly for many patients, which has led to the advent of 3D printed prosthetic devices such as the one created by Dr. Zuniga et al [3].
In order to control cost and maintenance, the battery was required to be a single cell lithium polymer battery so a standard, low-cost, integrated charger could be used. In addition, low-cost components that are widely available were used in the device.
The purpose of the present investigation was to address the need for this kind of device and develop an integrated solution that could fulfill the requirements of the aforementioned limitations.
The developed PCB was ordered from JLCPCB (JLCPCB, Shenzhen, China) and were populated by hand for the study. The prosthesis this control board was designed to interface with is the hybrid actuation prosthetic arm with two PQ12 motors integrated into the socket. The motors were driven at 12V to optimize the torque produced for each motor. In addition, a 500mAh lithium polymer battery was used for testing the device.
The low-cost 3D printers used in this study
were the Ultimaker 2 Extended+ (Ultimaker
B.V., Geldermalsen, The Netherlands).
The materials for printing the prostheses
were polylactic acid (PLA) and acrylonitrile
butadiene styrene (ABS). Other components
of the prostheses included: 1 mm nylon lift cord,
1.5 mm diameter elastic cord, Velcro,
medical-grade firm padded foam, a protective
skin sock, and a BOA dial tensioner system.
The final completed system was capable of
being integrated into these prosthetic devices.
The data generated for this study was completed
using a dedicated power supply to test the operating
requirements of the device.
Figure 3: The graphed results of the Matlab script.
CONCLUSION
The device developed in this study was promising and warrants future study as an alternative prosthetic mode of control.
REFERENCES
Trachtenberg, M. S., et al, (2011). Radio frequency identification — An innovative solution to guide dexterous prosthetic hands Annual International Conference of the IEEE Engineering in Medicine and Biology Society. doi: /iembs
Lake, Christopher & Miguelez, John M., 2003, ‘Evolution of microprocessor based control systems in upper extremity prosthetics,’ Technology and Disability 15, Advanced Arm Dynamics of Texas, Dallas, TX.
Zuniga, J, et al. (2015), doi: /s
Zecca, M., Micera, S., Carrozza, M. C., & Dario, P. (2017). Control of Multifunctional Prosthetic Hands by Processing the Electromyographic Signal. Critical Reviews in Biomedical Engineering, 45(1-6), doi: /critrevbiomedeng.v45.i
Figure 1: Block diagram of the RFID prosthetic control system. The USB interface is used for charging the on-board battery, the power supply recharges the battery and powers the system with an on-board 12V boost regulator. The microcontroller is satisfied by using an ATtiny2313A and interfaces to the DRV8838 motor drivers and Melexis RFID device.
Figure 2: The developed custom control board