Sub-Pages

Power Consumption Calculations

        This page contains a copy of the MATLAB program that was used to determine how much power (from batteries and air canister) the robot would consume and how long it could operate on a mission. This program can be downloaded from here.

The following table summarizes the results of the MATLAB program.

%power_calcs

clear all

close all

%buoyancy force per airlock cycle

wpc=.042;

%starting negaitve buoyancy/weight of the robot

sw=1.6;

%volume of gas per inflation in m^3

Vg=1.591*10^-5;

%Pressure of gas

Pg=12000;

R=8.314472; % ideal gas constant

mmco=44; %molar mass of CO2in grams

Tg=273+15; %gas temperature

%P*V=m*R*T/M find m, m=P*V*M/(R*T)

%Mass/weight of CO2 used per airlock cycle (in pounds)

gm=Pg*Vg*mmco/(R*Tg)*2.205*10^-3;

msa=2900; %max amount of mAh for solenoids

mra=1200; %max amount of mAh for relays and microcontroller

%Determine how many days the air supply will last and how much battery

%power will be required

%set the current weight and other counter variables

cw=sw;

i=0; %number of inflation cycles

cc=0; %number of inflate-deflate cycles

sa=0; %number of solenoid activations

sp=0; %amount of power for solenoids

rp=0; %amount of power used for relays

while cw>(sw-.75) %run until the current weight is less than the starting weight less the CO2 (until the CO2 is gone)

    cc=cc+1;

    bf=0; %preset buoyancy force

    j=0;

    while bf<(cw+.5)

        bf=bf+wpc;

        cw=cw-gm;

        i=i+1;

        sa=sa+2*1;

        j=j+1;

    end

    sa=sa+3;

    count(cc,:)=[i j sa cw];

    sp=sa*(1/(60*60))*400;

    rp=sa*(1/(60*60))*5/700+3*cc*2;

    if sp<msa

        tsa=cc; %record the number of cycles possible before exhausting solenoid battery

    end

    if rp<mra

        tra=cc; %record number of cycles possible before exhausting microcontroller battery

    end

end

%determine how many days it will take to exhaust the robots onboard

%resources

s.cnt=size(count);

daysGas=s.cnt(1)/12;

daysSol=tsa/12;

daysRel=tra/12;

days=[daysGas daysSol daysRel];

maxdays=min(days);

%determine the stages at which to changes thenumber of airlock cycles

i=0;

j=1;

h=1;

for k=1:s.cnt(1)

    if i~=count(h,2)

        i=count(h,2);

        act(j,:)=count(h,1:2);

        j=j+1;

    end

    h=h+1;

end

Output:

ans =

Number of days possible for one mission

maxdays =

   16.5833

ans =

Number of days possible based on Gas, Solenoid Battery, and Microcontroller Battery

days =

  197.5000   21.4167   16.5833

ans =

i and j values to program the microcontroller with.

ans =

These determine how many times the airlock is cycled per inflate-deflate cycle

act =

          50          50

        5449          49

       10887          48

       16310          47

       21761          46

       27188          45

       32587          44

       38042          43

       43459          42

       48876          41

       54328          40

       59727          39

       65186          38

       70619          37

       76020          36

       81455          35

       86879          34

       92318          33