EECS192 Lecture 7

Mar. 5, 2019

Topics• Quiz 3

• PCB quick note

• Speed sensing/velocity control- quick intro

• Line sensor- processing– Automatic Gain Control

– Edge detection/fitting

– Sanity check: median/outlier

• HW1 Python template and Natcar 2016 team1 data

(under Resources on Piazza)

Notes:

1. Check off-

• 3/8/2019 : benchtop velocity control

+ Lab Clean (individual)

• 3/15/2019: benchtop line tracking (line camera+servo)

• 3/22/2018 drop-and-run, figure 8

2. Community Spirit: PCB peer review, Piazza, helping fellow students

3. CalDay Sat. April 13 @ UCB,

PCB Notes

BATTERY

On board- quick intro

• Shaft encoder

• Incremental position

time_min = rc_nanos_since_boot();

angle1 = rc_encoder_read ( int ch);

time_max = rc_nanos_since_boot();

Velocity Sensing• On board: estimating Dx/DT

velocity sensing

Note: care about velocity sensing usually at cruise speed (also stopping)

Sharp GPS260

100 us response time

velocity sensing

Sharp GPS260

• Choose current 4 mA in LED

• Vcc = 3.3 V

• May want regulated/clean voltage for Vcc

velocity sensing

Non-inverting amp to measure motor

current.

Back EMF can be estimated from battery

voltage and motor resistance.

Back EMF velocity sensing

1.8V

+

-0.01 ohm

(10 squares)

To A/D

Low voltage r-r op-amp

Velocity Control overview

On board…Proportional control:

U = kp*e = kp* (r-y);

Proportional + integral controlU = kp*e + ki * e_sum;

e_sum = e_sum + e;

PWM

Commanded

velocity

Sensed velocity

TSL 1401 line sensor

Line sensor

TSL 1401 line sensor

Line sensor

TSL 1401 line sensor- option exposure control(would need to modify PRU code)

Line sensor

SI

CLK

AO

Exposure time (>25 us)

129 clocks

Clock only

no A/D read

A/D read

~12 us

TSL 1401 line sensor NATCAR 8 bitFrame 0

Frame 0

Frame 1

Frame 2 Frame 2-Frame 0

Frame 1-Frame 0

Line sensor

Python Template# track_center_list - A length n array of integers from 0 to 127.

Represents the predicted center of the line in each frame.

# track_found_list - A length n array of Booleans (100=true, 10 = false).

Represents whether or not each frame contains a detected line.

# cross_found_list - A length n array of booleans.

Represents whether or not each frame contains a crossing.

Start line finish linecrossingSteps

Extra Slides

Differential amp to read back EMF for

H Bridge driving motor. Change values for

12V Back EMF…

Back EMF velocity sensing

3.3V

SW

t

closed

im

VL

open

0 57 us20 us

7.5V

5 amp

6.5 amp

-2.65V

+

-10v

+ VL -

vDS0.1 ohm

SW

Lim

Rm

e+ -

2v

Snubber/flyback diode

Back EMF velocity sensing

VDS = 10V - VDIODE