Electronics Design Laboratory Lecture #6ecee.colorado.edu/ecen2270/lectures/Lecture06.pdf · 2019....

ECEN2270 1Electronics Design Laboratory

Electronics Design LaboratoryLecture #6

Electronics Design Laboratory 2ECEN 2270

Speed Sensor and Filter

GND

5VDC

0-5V Speed Output proportional to actual motor speed

Vspeed

ForwardController

Reverse Controller

0-10V

0-10V

0-5V Speed Output proportional to desired motor speed

+-Speed error

Forward

NOT Forward

Experiment 1 & 2

Experiment 3A

Experiment 3B

Introduction to Lab 3 Part B: Closed-Loop Speed Control

ENCA

VDC+

VDC-

DC motor driver and speed sensor

Electronics Design Laboratory 3

+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB

O1

O2

encspeed sensor(Lab 2)

+5V

tp = 1/fenctp = 1/fenc

ton

+5V +5V

00

RI

CI

vs

sense_PWM

Q1

Q3

Q2

Q4

vo

𝑓𝑒𝑛𝑐 =𝜔

2𝜋× 13 × 51 ≈ 106𝜔

( ) ( ) encon

enc

ons ft

t

tv V5V5 +=+=

ECEN2270

enctenct

R3 and C3 from speed sensor

“Open-loop” speed control using vo


+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB

O1

O2


+5V


ton

+5V +5V

00

RI

CI

vs

sense_PWM

Q1

Q3

Q2

Q4

vo

vo = +10V

Faster

Slower

ECEN2270

vo = 0

vs = 0

vs = +4V

System Gains


+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB

O1

O2


+5V


ton

+5V +5V

00

RI

CI

vs

sense_PWM

Q1

Q3

Q2

Q4

vo


2𝜋× 13 × 51 ≈ 106𝜔

ECEN2270

enctenct

vrefμC

INPUT OUTPUT

Speed sensor gain

Electronics Design Laboratory 6ECEN2270

Encoder OutputFrequency proportional to physical speed

encf

Speed Sensor PWMDuty cycle proportional to frequency

ont


2𝜋× 13 × 51 ≈ 106𝜔Frequency of encoder pulses [Hz]

Speed sensor output voltage [V] 𝑣𝑠 = +5V𝑡𝑜𝑛𝑡𝑝

= +5V 𝑡𝑜𝑛𝑓𝑒𝑛𝑐

Speed sensor gain [Vs/rad] 𝐾𝑠𝑒𝑛𝑠𝑒 =𝑣𝑠𝜔= 106 × 5 × 𝑡𝑜𝑛 = 530 𝑡𝑜𝑛

5V

0V

Voltage OutputVoltage proportional to Duty Cycle

Physical Frequency Duty Cycle Voltage

Encoder Speed Sensor Low Passencf d

sv

Open-loop system


+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB

O1

O2


+5V


ton

+5V +5V

00

RI

CI

vs

sense_PWM

Q1

Q3

Q2

Q4

vo

ECEN2270

vrefμC

INPUT OUTPUT

Speed sensor

senseK

enc

vs

Closing the feedback loop: compensator


+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB

O1

O2


+5V


ton

+5V +5V

00

RI

CI

vs

sense_PWM

Q1

Q3

Q2

Q4

vo

ECEN2270

vrefμC

INPUT OUTPUT

Speed sensor

senseK

enc

vs

• Need vs to equal vref in steady state

• Need to change vo

depending on our speed error (vref - vs)

• Need 0-10V output and0-5V inputs.

Integral compensator


+

_+10 V

O1

RI

RI

CI

CI

vs

vref

vo

( ) ( )sref

Isref

II

o vvs

Kvv

RsCv −=−=

1

ECEN2270


+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB+

_+10 V

O1

O2


+5V


ton

+5V +5V

00

RI

RI

CI

CI

vs

vref

sense_PWM

Q1

Q3

Q2

Q4

vo

ECEN2270

Closed-Loop System with Integral Compensator

OUTPUT

Speed sensor

senseK


+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB+

_+10 V

O1

O2


+5V


ton

+5V +5V

00

RI

RI

CI

CI

vs

vref

sense_PWM

Q1

Q3

Q2

Q4

vo

ECEN2270

Qualitative Analysis of Feedback Loop

OUTPUT

Speed sensor

senseK

sensed speed too high

vo goes down iDC goes down

goes down

fenc goes downvs goes down


+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB+

_+10 V

O1

O2


+5V


ton

+5V +5V

00

RI

RI

CI

CI

vs

vref

sense_PWM

Q1

Q3

Q2

Q4

vo

ECEN2270

OUTPUT

Speed sensor

senseK

s

K I

)(sGm

Integral compensator

-+verror

vs

vrefμC

INPUT

Speed control circuit as a closed-loop system

Speed control circuit as a closed-loop system


vref ve vo ω

vs

-+

m

o sG

+1

1

s

K I

)(sGc)(sGm

senseK

Integral compensatorDriver & motor

Speed sensor

Closed-loop response:

)(1

)(1)(

sT

sT

KvsG

senseref +==

Loop gain:

)()()( sGsGKsT mcsense=

Closed-loop speed control


+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB+

_+10 V

O1

O2


+5V


ton

+5V +5V

00

RI

RI

CI

CI

vs

vref

sense_PWM

Q1

Q3

Q2

Q4

vo

Steady-state:

vs = Ksense = vref

= vref/Ksense

End result: speed precisely set by vref, independent of load torque, motor imperfections, …

Faster

Slower

ECEN2270

How to change direction?


+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB+

_+10 V

O1

O2


+5V


ton

+5V +5V

00

RI

RI

CI

CI

vs

vref

sense_PWM

Q1

Q3

Q2

Q4

vo

ECEN2270

Stop & Go Control


+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB+

_+10 V

O1

O2


+5V


ton

+5V +5V

00

RI

RI

CI

CI

vs

vref

sense_PWM

Q1

Q3

Q2

Q4

vo

+5V

ON = GOOFF = STOP

Stop & Go Control Implementation


S

DG

ECEN2270

+5Vencoder

DC1 DC2

iDC

VDCsupply

= +10 V

B1 B2

vDC+_

RBRB+

_+10 V

O1

O2


+5V


ton

+5V +5V

00

RI

RI

CI

CI

vs

vref

sense_PWM

Q1

Q3

Q2

Q4

vo

+5V

PMOS

+5V = GO 0V = STOP

c

RG

Speed Control Complete Schematic


Feedback Control circuit block

• Op-amp integral compensator

• PMOS transistor used to force output vo at “b” low

• Two copies of the circuit used: one for each side of the motor (to control motor in each direction)


vo

ECEN2270

Floor planning


GND

+10V

+5V

+5V GND

+5V

GND

+5V

GND

+10V

GND

+10V

GND

Left wheel Right wheel

Feedback circuits

Left wheel Right wheel

Arduino

Speed sensors

Space for project add-ons

Space for project add-ons

Project:Remote control

receiver

ECEN2270

Speed Control Demo Setup


Use waveform generator, 0-5V, 500 Hz square wave, Hi-ZAdjust duty cycle to set the speed reference so that fenc = 200 Hz

Show speed-sensor output pulses on the scope. Frequency of the pulses should be fenc = 200 Hz

ECEN2270

Soldering tips

Electronics Design Laboratory 22ECEN 2270

Date post:	27-Feb-2021
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Electronics Design Laboratory Lecture #6ecee.colorado.edu/ecen2270/lectures/Lecture06.pdf · 2019....

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