Axis AX-906 Betriebsanweisung PDF herunterladen (Seite 21)

Controlling

motor

velocity

CHAPTER

4.

APPLICATION DESIGN

77

The

recommended

system

frictional

load

for a

step

motor

is

approximately 5% of

the

motor's

maximum

torque

capability.

For

motor

specifications

and

speed/torque

curves,

refer to

Chapter

6,

Hardware Reference.

The

step-to-step

accuracy

of

the

step

motor

should

not

be

confused

with

the

motors

absolute accuracy. Absolute

accuracy

is

based

on

the

quality of

the

mechanical

construction

of

the

motor.

This

means

that

tuning

of

an

open-loop

stepper

motor

and

drive

will

not

improve

this

spec.

On

the

other

hand,

the

drive electrOnics

are

responsible for

adjusting

current

in

the

two

phases

of

the

motor

which

create

the

m1crosteps found between

each

1.8

0

full

motor

step.

The

amount

of

distance

each

step

can

vary is referred to

as

the

step-to-step

accuracy

of

the

system

and

it

may

be possible to

improve

this

by

tuning.

The

motor

should

be

tuned

to

its

drive while

under

nonnal

loaded conditions.

Tuning

prior

to

this

is

useless

since

changes

in

the

load

or

the

system's

transmission

will

result

in

a new

natural

frequency for

the

motor.

Tuning

the

drive affects

the

profile of

current

being

sent

to

the

motor. You will

need

to

re-tune

the

drive

if

the

current

setting

switches

are

changed. Refer to

Chapter

6 for valid settings for

DIP switches 1

through

5.

When

using

the

AX

Drive,

the

built-in

indexer

will solve

this

problem. Using

an

RS-232C

communications

device, place

the

AX

in

Mode

Continuous

(MC)

and

use

the

Acceleration (A)

and

the

Velocity

(V)

commands

to

get

the

motor

moving,

then

vary

the

velocity

using

the

Immediate Velocity

(VC)

command.

Command

MC

A10

V1

G

VC2

VC.s

Description

Set to Mode continuous

Set acceleration to 10 rev/sec

Set velocity to 1 rev/sec

Execute the move (Go)

Set immediate velocity to 2 rev/sec

Set immediate velocity to .5 rev/sec

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