ME 224 Experimental Engineering: Professor Espinosa 2005

TEAM:

JamieCharlesCarloNikoJavier

ME 224 Experimental Engineering: Professor Espinosa 2005

Overview

Goal

Assembly

Programming

Gyroscope Calibration

Feedback Control

Conclusion

ME 224 Experimental Engineering: Professor Espinosa 2005

Goal• Goal is to follow given path

ME 224 Experimental Engineering: Professor Espinosa 2005

Assembly• Building and assembly

– Robotic kit

– Additional parts• Handy board

• Metal Wheely Bar

• Bread board– Gyroscope, Operational amplifier,

low pass filter: R, C

• Programming– Several choices in programming

codes

ME 224 Experimental Engineering: Professor Espinosa 2005

Programming

• Choosing the Code– Labview

• Non RealTime

• External connections

– Basic Stamp• Avoid analog to digital converter

• External computations

• Programmed in Basic

ME 224 Experimental Engineering: Professor Espinosa 2005

Programming• Interactive C

– Advantages• Analog input with 8 bit

precision

• No external connections

• Easier to program

• LCD display

– Disadvantages• Causes noise in the

gyroscope rate out

– CODE

ME 224 Experimental Engineering: Professor Espinosa 2005

Self Test

* Verified Chip Function

* Applied the following connections

* Behavior:

- +/-0.66V Change @ rateout

ME 224 Experimental Engineering: Professor Espinosa 2005

ADXRS150 - Angular Rate Sensor

• http://www.sensorsmag.com/articles/0903/53/main.shtml

Fc = -2m(ω x vr)

ME 224 Experimental Engineering: Professor Espinosa 2005

Gyroscope Calibration• First Stage

– Rotate Robot at different angular velocities for different periods of time

– Use Labview to obtain Output Voltage

– Analyze data with Excel, taking an average of the output voltage

– Test Robot

ME 224 Experimental Engineering: Professor Espinosa 2005

Labview Code

ME 224 Experimental Engineering: Professor Espinosa 2005

Obtained Data

Gyroscope Calibration

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0 100 200 300 400 500 600 700 800 900 1000

Time (5ms)

Vo

ltag

e d

iffe

ren

ce f

rom

bas

elin

e (V

)

ME 224 Experimental Engineering: Professor Espinosa 2005

Calibration ResultsGyroscope Output Voltage vs. Angular Velocity

y = -0.0022x + 1.9356

R2 = 0.9998

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

50 100 150 200 250 300

Angular Velocity in Deg/Sec

Gyr

osc

op

e O

utp

ut

Vo

ltag

e in

V

ME 224 Experimental Engineering: Professor Espinosa 2005

Gyroscope Calibration

• Angles not followed correctly

• Second Stage Calibration– Reduce noise caused mainly by vibrations and

handy-board by adding a low-pass filter– Supply 5V instead of 4.75 V to gyroscope– Re-Calibrate using different method

ME 224 Experimental Engineering: Professor Espinosa 2005

Re-Calibration

• Write simple program to rotate robot 1080 degrees

• Adjust the “gyro calibration factor” (degrees/second/volt)

• Iterate several times until angle of rotation is accurate enough

• Test Robot by following the path

ME 224 Experimental Engineering: Professor Espinosa 2005

FeedBack Control• Two Sectors of control

– Straight– Turns

• Limitations of servos– Do not change speeds easily– 20 millisecond update limit– Jitter response to noise

ME 224 Experimental Engineering: Professor Espinosa 2005

Is t < desired runtime L

Calibrate gyro center: C(volts)

No YesStop

Servo Pulse: A7=constA5=const

V < C - .03 V > C + .03 V = C ± .03

t = t +.5Gyro output: V(volts)

Correct Left:Servo A7 pulse +1

Correct RightServo A5 pulse + 1

No Correction

Feedback Control Diagram for Strait Linear Motion

User Input: L(seconds)

ME 224 Experimental Engineering: Professor Espinosa 2005

Feedback Control Diagram for Constant Rotation Turns

User Input: D(degrees) Calibrate gyro center: C(volts)

Is Deg < D

No Yes

Servo Pulse: A7=constA5=const

Calibrated gyro conversion factor: S(ω/volt)

Stop

Gyro output: V(volts)

Deg = Deg + ω*.01

ω = (C-V)*S

t = t +.01

ME 224 Experimental Engineering: Professor Espinosa 2005

Special Features

• No extensions / attached harnesses

• LCD read out

• Adjustable trajectory length

• Accuracy

ME 224 Experimental Engineering: Professor Espinosa 2005

Conclusion

• We applied learned techniques in Labview

• Utilized ECE knowledge– OpAmp voltage output modification– Capacitive filtering– Voltage Divider

• Created effective control programs

• Integrated Gyro Sensor

• Had Fun