Mechatronics Design Project

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Mechatronics Design Project Spring 2003
Demonstration May 7, 2003
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Hardware Update

• Previous Car was difficult to Control
• Steering had too much play in wheels
• Decided to get a new system rather than fix
• due to time constraint

3

• Drive Motor
• located at rear of car
• Controls speed

New Hardware

• Main Difference
• - spring return

• Steering Motor
• - located at front
• controls tracking of
• car based on track
• sensors
• - Utilizes PID controller

4
Sensors

• Already Calibrated
• 2 Front Sensors (follow track)
• 1 inch apart, best distance

1

• Side Sensor
• (stopping)

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Other Adjustments

• Changed track to ¾ inch wide
• - sensors on outside of track
• Change track color to cardboard brown
• - provided less contrast than white background

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Flow Chart Code
void main() int y , i float r
0.0 float e_curr // current error float
check_time float t_sample .03 // sample
time float u_control float e_prev
0.0 float i_prev 0.0 // PID
Values float kp0.6 float td0.00
float ti100000.0 float mvalue int
knob_value
start
Declare Variables
continued
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// reduces sensitivity of knob and set to
standard speeds   while(!stop_button())
if(knob()lt 25) knob_value15
if(knob()gt25 knob()lt50) knob_value18
if(knob()gt 50 knob()lt75) knob_value20
if(knob()gt75 knob()lt100)
knob_value23 if(knob()gt100
knob()lt125) knob_value25 if(knob()gt
125 knob()lt175) knob_value27
if(knob()gt175 knob()lt225) knob_value30
if(knob()gt225 knob()lt255) knob_value32
printf("d\n",knob_value)
msleep(200L)
Set speed With knob
Stop Button Pressed?
no
yes
continued
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Start Button Pressed?
printf("press start!") start_press()
reset_system_time() //set motor speed to knob
values motor(3,knob_value)
no
yes
Reset system time
Motor speed knob value
continued
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Stop Button Pressed?
yes
Check_time seconds t_sample (float)(i)
no
-.01lt Time lt0.01 ?
no
yes
Object near Side ?
Set integral
Motor(1,u_control)
i
Set u_control
Update errors and integrals
Set y (error)
yes
Set e_curr
end
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while(!stop_button())
check_time seconds()- t_sample(float)(i)
if (check_time lt 0.01 check_time gt -0.01)
while(analog(5)gt8)
float i_curr i_prev
0.5 (e_curr e_prev)t_sample
u_control kpe_curr kptd(e_curr -
e_prev)/t_sample (kp /ti)i_curr
y analog(4)-analog(2)
e_currr-(float)(y) //set motor speed to
u_control motor(1,(int)(u_control)
) e_preve_curr
i_previ_curr i
ao() tone(1000.0,0.3)tone(999.0,0.3)t
one(850.0,0.3) tone(750.0,0.3)tone(642
.0,0.3)tone(510.0,0.3)tone(510.0,0.3)
printf("\nClear!")
ao() printf("\nBye!") beep()beep()

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Tuning PID Controller

• Process
• Introduced step input curve
• lined up car on marks for each measurement
• Car ran at constant speed, 23

curve
marks
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Varing Kp

• Initial Kp set to 1.0
• Varied Kp 1.0 ? 0.3
• Ti 100,000
• Td 0.0

Use Kp0.6
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Varing Ti

• Initial Ti set to
• 100,000

Use ti500
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Varing Td

• Initial Td set to 0
• does not seem
• to decrease response
• time but less over
• Shoot

Use td0.5
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- Demonstration - Questions?