Spring 2017 Prosthetic Arm: Power Allocation Report
The Robot Company | CEO Professor Gary Hill
Blog Post Created by Project Manager | Bianca Esquivel
Project Documentation Written by Mission, Systems, and Test Engineer | Phuong Tran
This report is created in response to requirements
L1-3: The Prosthetic Arm shall be able to operate for at least 16 minutes and 39 seconds (999 seconds) which is the duration allowed to play a game of minesweeper.
L2.3.1: The capacity of the battery shall be more than 943 mAh
In this report, we seek to understand the source of each quantity placed in the report.
Test and Evaluation
In this section, we seek to understand the reason for each quantity placed in the power report
B3: This value was from the last semester measured current draw of the hand
D3: This uncertainty was 20% because the MST engineer was not present when the measured value was taken
E3: This high margin corresponds to the high uncertainty percentage
B4: This value was calculated by 20mA (current draw from each I/O port) multiply by 20 (# of I/O ports)
D4: this low uncertainty results from the values were taken from Arduino manufacturer website
E4: similarly, low uncertainty percentage corresponds with low margin
B5: This value was taken from the maximum current draw of the 5V pin of the Arduino
C5: This value was taken from the result of the Servo Load Test
D5: This uncertainty is low because we have done the test. Even though the expect current is different from the measured value, we have changed our PCB layout accordingly. In addition, the project allocation value is determined with this difference in mind.
E5: This low margin is the result of low margin percentage
E12: This is the spec from the battery chosen since we performed the Battery Discharge Test
E13: we total the margin in mA
E14: we total the expected current in mA
E15: the formula for contingency = E12 – E13 – E14
F12: This value is the capacity of the battery chosen from the Battery Discharge Test
F13, F14: These values are computed by multiplying mA value with duration of the mission (0.2775 hours – requirement L1.3)
F15: the formula for contingency = F12 – F13 – F14
Due to the allocation value, we pick the 11.1V 2200mAh 3S LiPo because this battery will satisfy L1.3 and L2.3.1. This decision is the result of Battery Discharge Test.