hockey论文翻译(一种新的五相步进电机驱动电路开发)中英文对照

Development of a Novel Drive Topology for a Five

Phase Stepper Motor

T.S. Weerakoon and L. Samaranayake

Dept. of Electrical and Electronic Engineering, Faculty of Engineering, University of

Peradeniya, Sri Lanka

Abstract

-In

this paper, a

novel

drive

topology for

a

five

phase stepper

motor

is

described in detail. Commercially off the shelf, low cost, standard stepper motor

drive ICs are used to derive a novel drive topology for five phase stepper motors

which enables closed loop speed and position control powered by inner current

control

loop.

It

is

proved

that

the

derived

topology

can

be

generalized

to

any

stepper motor with higher odd number of phases.

The

designed

driver

consists

of

full

step,

half

step,

clockwise

and

counter

clockwise drive modes with the speed control and current control.

I. INTRODUCTION

In most of the robotics and automation engineering designs various types of stepper

motors are used to obtain the required motion profiles. Stepper motors are preferred,

as they do not require frequent maintenance and due to their ability to operate in many

harsh

environments.

Selection

of

the

motors

and

their

drive

circuits

depend

on

the

required

performance

characteristics

of

the

applications.

The

two

phase

and

four

phase stepper motors are the most common types available in the market.

However, for applications requiring high precision, low noise and lower vibration,

Five

Phase

Stepper

Motors

are

used.

Due

to

smaller

step

angle,

five

phase

stepper

motors

offer

higher

resolution,

lower

vibration

and

higher

accelerations

and

decelerations.

Therefore

it

is

essential

to

make

sure

that

these

motor

characteristics

can be obtained from the designed drive topology.

Because

the

five

phase

stepper

motors

are

a

rarely

used

type

in

the

robotic

applications and the construction is typically complicated, it is very difficult to find

driver

ICs,

which

are

manufactured

exclusive

for

them.

As

a

result,

the

available

Driver circuits for five phase stepper motors are very expensive.

Using the available drive control

ICs

manufactured for

common kinds of stepper

motors

such

as

2

phased

and

4

phased

and

using

them

in

modeling

new

driver

topology for other stepper motors would be a cost effective approach.

The

IC

L297

integrates

all

the

control

circuitry

required

to

control

bipolar

and

unipolar

stepper

motors.

The

L298N

dual

H

bridge

drive

forms

a

complete

microprocessor to stepper motor interface. Here, novel drive topology is investigated

and developed for five phase stepper motors by adding a microprocessor and logical

control

system

with

L297

and

L298N.

The

complete

topology

is

described

in

this

paper.

Section II explains the component characteristics. Section III is on the control logic

circuit design phenomena. The interface design is given in Section IV with results in

Section V

. Finally the conclusions are presented in Section VI.

II. CHARACTERISTIC ANALYSIS OF MAIN COMPONENTS

The IC L297 can be used with an H bridge driver IC for motor drive applications as

shown

in

Fig.1.

In

this

design

H

bridge

function

is

achieved

from

the

L298N

or

L293E.

This

may

change

depending

on

the

power

rating

of

the

motor.

The

control

signals to the L297 may be received from microcontroller or from external switches.

A single IC can drive a 2 phase bipolar permanent magnet motor, a 4 phase unipolar

permanent

magnet

motor or

a 4 phase variable reluctance motor. Because very

few

electronic

components

are

used,

it

has

many

advantages

such

as

lower

cost,

higher

reliability

and

the

ability

to

house

in

a

comparatively

smaller

space.

The

L297

generates three modes of phase sequences, namely half step mode, full step mode and

wave mode depending on the input signals it receives.

Fig. 1. Circuit diagram to drive a 2 phase bipolar or 4 phase unipolar stepper motor

using L297 and L298N ICs

A.

CURRENT CONTROL

Small

stepper

motors

generally

need

small

DC

supplies

that

control

the

winding

currents and they are limited by the winding resistances. On the other hand, motors

with the larger rated torque values have windings with smaller resistances. Therefore,

they require a controlled current supply.

The L297 provides load current control in the form of two Pulse Width Modulation

(PWM) chopper circuits and each chopper circuit consists of a comparator, a flip-flop

and an external sensing resistor.

In this method, while the motor current is increasing, the control system applies the

supply

voltage

to

the

motor.

When

the

current

is

reached

up

to

the

threshold,

the

control system tries to maintain the current at the desired value by changing the duty

ratio of the voltage supply as shown in Fig.2. For each chopper circuit, the duty ratio

(D) of the voltage supply to the motor is defined as:

D = T

on

/ (T

on

+ T

off

),

where

the

T

on

and

T

off

are

switch

on

and

off

durations

respectively

of

the

H

bridge.

In the chopper circuit, the flip-flop is set by each pulse from the oscillator, enabling

the output and allowing the load current to increase. As it increases the voltage across

the sensing resistor increases and when this voltage reaches V

ref

the flip-flop is reset,

disabling

the

output

until

the

next

oscillator

pulse

arrives.

In

this

method

V

ref

determines the peak load current.

Fig. 2. Circuit containing the flip-flop,

the oscillator and the comparator used

Fig.3. PWM operation of the

voltage for current control

for current controlling

Fig.3

shows

how

the

current

through

the

motor

is

controlled.

When

the

motor

current

goes beyond the set point, the voltage applied to the motor terminal will be

grounded.

Therefore

the

current

will

decay

and

finally

the

motor

current

can

be

controlled.

The L298N is a monolithic circuit contains two H bridges. In addition, the emitter

connections of the lower transistors are brought out to external terminals allowing the

connection of current sensing resisters.

B. CURRENT CONTROL IN INHIBIT CHOPPER MODE

Inhibit chopper control mode and phase line chopper control mode are two of the

most common types of current

control

techniques

available.

In the latter case when

the voltage across the sensing resistor reaches to V

ref

, only the low side switch is made

off. Hence this method is not suitable and inhibit chopper control mode has to be used.

The required switching sequences for this can be taken directly from L297.

Inhibit chopper mode can be selected by pulling down (grounded) the CONTROL

input

signal

of

L297.

Then

chopper

acts

on

INH

to

control

the

current

through

the

motor

coils.

Therefore

the

contribution

of

INH

signal

generated

from

L297

is

very

important to create ENABLE signal for L298N. In the case when the voltage across

the sensing resister reaches to V

ref

, the chopper flip-flop is reset and INH is activated

and is brought to low. Then it turns off all four switches of the bridge. The chopping

frequency is determined by the internal oscillator of the L297. After switching off all

transistors, the diodes provide a path to divert the winding current. The switches of

the H bridge are made on in the next oscillator cycle.

Fig.4 explains current control phenomena at an instant when phase signal A is high

and B is low. These A and B signals are fed to two AND gates connected to low and

high

side

switches

in

the

L298N

to

generate

excitation

signal

with

the

same

INH1

signal

in

order

to

control

the

load

current.

The

AND

gate

output

will

become

high

only if and only if the INH1 is high.

Fig. 4. Inhibit chopper waveform when CONTROL is LOW

III. LOGIC CIRCUIT DESIGNING

In

any

mode

of

operations,

wave

patterns

of

A,

B,

C

and

D

phases

of

the

L297

repeat after four clock cycles as shown in Fig.5. Translation of the repetition of the

phase waveform after the ten clock cycles is essential to derive the drive topology for

the five phase stepper motor.

Fig. 5. In the normal operation, L297 two phases of a 4 phase stepper motor or two

ends

of

a

2

phase

stepper

motor

winding

are

made

ON

at

a

time

and

the

sequence

repeats after every 4 clock cycles

Fig. 6. Five phase excitation sequence

By

analyzing

the

three

modes

of

operations

of

the

L297,

it

is

clear

that

in

the

normal

drive mode, which is

usually

called as

two-phase-on drive mode, should be

selected

to

achieve

the

required

excitation

sequence

for

a

5

phase

stepper

motor

as

shown in the Fig.6.

By studying the required excitation sequence for 5 phase stepper motor and A, B, C,

D

phase

sequences

of

the

L297,

the

required

logic

circuit

was

designed.

The

procedure mentioned below was followed.

(i)

Separation of High and Low side transistor excitation pattern for each phase

from five phase excitation sequences as shown in Fig.6.

(ii)

Selection of suitable phases from A, B, C and D of L297 to generate the high

side excitation sequences.

(iii)

Generating input signals to the L298N using A, B, C, D output signals of the

microcontroller and the relevant AND gates.

(iv)

Create ENA (enable A) and ENB (enable B) signals for L298N

By dividing ten (10) steps of required phase pattern in to twenty (20) steps can be

equated to the four clock cycles of output wave pattern generated by the L297. The

Fig.7

explains

the

clock

cycle

selection

for

required

high

and

low

side

excitation

sequence.

High side transistor excitation sequence can be generated from L297 by selecting

suitable

output

phases

of

the

L297.

The

selected

order,

which

is

the

two-phase-on

mode of L297 is shown in the Fig.8. The microcontroller signals are used to generate

the required high side pulse patterns. The DM74LS08 Quad 2-Input AND Gates are

used to AND microcontroller signals and signals received from L297.

As shown in Fig.9, the input signals and Enable signals determine the high side and

low

side

transistor

switching

patterns.

Therefore

ENABLED

(EN)

signals

are

fed

from the microcontroller. But to achieve current control of the motor INH signal must

engaged

with

the

Enabled

signal

to

the

L298N

as

explained

under

current

control

section.

The

Fig.10

explains

how

the

EN

signal

to

L298N

is

generated

using

the

required Enable signal created by the microcontroller and Inhibit (INH) signal from

L297. An

AND operation of these two signals

generates

the relevant

EN signal

for

L298N.

Fig. 7. Required High and Low side transistor excitation sequences

Fig. 8. Generation of Input signals to the L298N

The

L298N

consists

with

H-bridges

and

one

output

of

a

bridge

was

used

for

a

phase. Two inputs of one H bridge is dependent each other. Therefore both outputs of

a single bridge cannot be used. To generate five phases, it is required to have three

numbers of L298N dual full bridge driver ICs. The selection of inputs and outputs of

L298N are shown in Fig.13 of Section IV

.

Fig. 9. Pull up and Pull down operation of L298N

Fig.10. Generation of ENABLED signal

IV

. INTERFACE DESIGNING

The

logic

circuitry

used

to

generate

required

input

signals

for

L298N

and

microcontroller

control

signals

play

a

major

role

in

the

driver

circuit.

The

Fig.11

shows interface of L297, DM74LS08 Quad 2-Input AND Gates ICs and L298N with

the microcontroller PIC16F877A.

The circuit configuration for L297 is shown in Fig.12. The control signal has to be

grounded to obtain the inhibit control mode in order to limit the current through the

motor

windings.

The

CLOCK

signal

is

supplied

by

the

microcontroller

and

HALF/FULL pin should always to be low for full mode (two-phase-on) of operation.

The ENABLED signal is used to control the motion of the motor. When it is low, all

INH1,

INH2,

A,

B,

C,

D

pins

are

brought

to

low.

The

V

ref

value

sets

the

current

flowing

through

the

motor.

There

are

two

L297

ICs

used

and

it

is

necessary

to

synchronize them. It can be done easily by using the SYNC pin of L297.

Fig. 11. Block diagram of the system

The Fig.13 shows how the input and output terminals are used in L298N. Usually

100nF non- inductive capacitors are used between both V

s

and V

c

with the ground. The

value of the

current sensing resistor has to be as small as 0.5Ω

in order to avoid large

voltage drops at large currents.

External diode bridges provide current circulating paths when the inputs of the IC

are

chopped.

Usually

Schottky

diodes

are

used

here

because

they

are

faster

in

recovery.

V

. RESULTS

The

theoretical

and

logical

analysis

of

the

stepper

drive

circuit

design

approach

shows that it is a simple construction having several modes of operation and control.

Fig. 12. Configuration of L297

Fig.13. Configuration of L298N

The performance of the stepper drive circuit shown in the Fig.14 was tested for the

following capabilities:

1. Speed control capability

2. Current control capability

The Fig.15 (a) and (b) show the excitation wave forms at each phase terminal. The

excitation sequences for all five phases reveal that they are working according to the

requirement. Fig.15 (b) shows additional orange and green phase excitation sequences

to

compare

the

black

phase

excitation

with

the

others.

Due

to

the

charging

and

the

discharging of the capacitors by the current flowing through the windings of the motor,

there are some transients at each excitation points.

The speed control of the motor has been achieved by varying the frequency of the

excitation sequence of the five terminals. It is clearly shown that the pulse width of

the

voltage

sequences

of

Fig.15

(a),

(b)

gets

doubled

in

the

Fig.16

(a),

(b)

in

same

time

scale

of

5ms/div.

It

is

observed

that

the

rotating

speed

(speed

1)

of

the

motor

relevant to the excitation sequence shown in Fig.15 is half that of the speed (speed 2)

of the excitation sequence shown in Fig.16. Hence by varying the pulse frequency of

the excitation sequence generated by the PIC microcontroller, the speed of the motor

can be varied.

Fig. 14. Drive circuit with microcontroller

Fig. 15(a). V

oltages of the Blue, Red, Orange and Green phases at speed 1

Fig. 15(b). V

oltages of the Orange, Green and Black phases at speed 1

Fig. 16 (a). V

oltages of Blue, Red, Orange and Green phases at speed 2

Fig. 16 (b). V

oltages of the Red, Orange, Green and Black phases at speed 2

The current controlling capability of the motor drive circuit has been demonstrated

in the Fig.17(a), (b), (c). For the sake of demonstration, only the RED phase has been

considered

and

Fig.17(a)

shows

the

current

wave

at

higher

V

ref

(=600mV)

which

is

greater than the V

sense

. Then the INH signal does not pull down to limit the current

absorb

by

the

motor.

Each

phase

has

positive

and

negative

current

components,

because

the

phase

voltage

varies

from

+V

s

,

+V

s

/2

to

0V

and

current

to

the

phase

varies from positive, zero to negative respectively, corresponding to the latter voltage

variation. By chopping the inhibit (INH) signal to the L298N, the voltage at the motor

terminals is limited to control the current through each winding.

Fig. 17(a). Phase Current and INH signal variation at V

ref

= 120 mV

Fig.

17

(b)

and

(c)

show

the

current

controlling

capability

at

two

different

V

ref

values of 200mV and 120 mV

.

Fig. 17(b). Phase Current and INH signal variation at V

ref

= 200 mV

Fig. 17(c). Phase Current and INH signal variation at V

ref

= 120 mV

VI. CONCLUSIONS

The proposed novel drive for 5 phase stepper motor is a cost effective motor driver