Futaba GY401 User Manual download pdf

FEATURES

FOREWORD

•AVCS system

Since rudder trim changes caused by wind and other meteorologi-

cal changes and front, rear, forward, reverse, and other helicopter

attitude changes are automatically cancelled, tail (rudder) opera-

tion is easy, making it perfect for 3D flight.

•SMM gyro sensor

Use of newly developed extremely low drift SMM (Silicon Micro

Machine) gyro sensor virtually eliminates rudder trim changes

during flight.

•Digital servo compatible (DS mode)

DS mode makes it compatible with Futaba digital servos. Maxi-

mizes the high-speed response performance of the digital servo.

•Remote gain function and mode switching func-

tion

Remote gain function allows sensitivity switching from the trans-

mitter and mode switching function allows AVCS/normal gyro

mode switching.

•Integrated, compact, and lightweight

Compact size (27x27x20mm) and light weight (27g) realized by

high density mounting technology.

•Conductive resin case

Conductive resin case improves EMC (electrostatic and electro-

magnetic interference) resistance.

SET CONTENTS

•GY401

•Double-sided tape

(3 sheets)

The GY401 is a high performance, compact, light weight AVCS

(Angular Vector Control System) gyro developed for model

helicopters. Because the sensor and control circuit are integrated,

it is simple to install.

S9253 Ratings

(Digital servo for gyro)

•Speed: 0.08sec/60˚(at 4.8V)

•Torque: 2.0kg-cm(at 4.8V)

•Dimensions: 40x20x36.6mm

•Weight: 49g

•S9253

(Only a set w/servo)

Applicable servos

Gyro performance largely depends on the servo used. The

higher the speed and response of the servo, the better the gyro

sensitivity and performance. From this standpoint, a digital

servo is perfect for use with this gyro. The S9253 high-speed

digital servo developed especially for gyro use is recommended.

• No part of this manual may be reproduced in any form without prior permis-

sion.

• The contents of this manual are subject to change without prior notice.

• This manual has been carefully written. Please write to Futaba if you feel that

any corrections or clarifications should be made.

Thank you for buying a GY401 AVCS gyro.

Before using your new gyro, please read this manual thoroughly and

use the gyro properly and safely. After reading this manual, store it

in a safe place.

1M23N08102

The GY401 comes with the following accessories:

•Mini screwdriver

(for adjustments)

GY401 Ratings

(Integrated sensor type AVCS rate gyro)

• Control system:

Digital advanced PI (Proportional Integration) control

• Gyro sensor:

SMM (Silicon Micro Machine) system vibration gyro

• Operating voltage: +4 to +6VDC

• Operating temperature range: -10˚C to +45˚C

• Dimensions: 27 x 27 x 20mm

• Weight: 27g (including connector)

• Functions:

Gyro operation direction switch, DS mode switch, Control delay

trimmer, Limit trimmer, Remote gain control, AVCS/normal mode

switching

AVCS Gyro

Conventional gyros send control signals to the

rudder servo only when the tail of the helicopter

moves. When the tail stops moving, the control

signal from the gyro becomes zero. Conversely,

the AVCS gyro continues to send control sig-

nals to the servo even when the tail of the

helicopter stops moving.

The following sequentially describes the con-

ventional gyro and the AVCS gyro.

Operation of Conventional Gyro

Basic operation is described by considering the

case when the helicopter is hovering under

cross-wind conditions. With a conventional

gyro, when the helicopter encounters a cross-

wind, the force of the cross-wind causes the tail

of the helicopter to drift. When the tail drifts,

the gyro generates a control signal that stops the

drift. When the tail stops drifting, the control

signal from the gyro becomes zero. If the cross-

Operation of AVCS Gyro

Conversely, with an AVCS gyro, when the

helicopter encounters a cross-wind and the tail

drifts, a control signal from the gyro stops the

drift. At the same time, the gyro computes the

drift angle and constantly outputs a control

wind continues to cause the tail to drift in this

state, the "stop" operation is repeated until the

tail faces downwind. This is called the

"weathervane" effect.

signal that resists the cross-wind. Therefore,

drifting of the tail can be stopped even if the

cross-wind continues to effect the helicopter. In

other words, the gyro itself automatically cor-

rects (auto trim) changes in helicopter tail trim

by cross-wind.

Considering operation of an AVCS gyro, when

the tail of the helicopter rotates, the servo also

rotates in accordance with the angle of rotation

of the tail. When the tail stops rotating, the servo

judges that it has stopped in that position. This is

the auto trim function.

Fuselage Maintenance

Precautions

Do not turn the sensitivity trimmer with

too much force.

The trimmer may break. Always use the miniature

screwdriver supplied to make adjustments.

Make positive maintenance of the fuselage

tail section a habit.

The rigidity of the tail section has a large effect on gyro

performance. Therefore, loose supporter and tail pipe

aging also have a large effect on the characteristics.

Service the fuselage with a little vibration

as possible.

Fuselage vibration has a very adverse effect on gyro

performance.

Mounting Precautions

Always use the accessory sensor tape to

install the gyro to the fuselage.

This is necessary to securely fasten the gyro to the

fuselage so that operation of the gyro does not transmit

unwanted fuselage vibrations directly to the sensor.

When mounting the gyro, provide a little

surplus so that the gyro connection cables

are not too taut.

If the gyro cables are too taut, the gyro will not display its

full performance. If the gyro peels, control will be lost

and result in a dangerous situation.

When using the gyro with a helicopter,

install the GY401 at least 10cm from the

drive motor.

The drive motor generates strong electromagnetic noise.

This noise may interfere with the gyro sensor and cause

erroneous operation.

Mount the GY401 so that metals or other

conductive objects do not touch the gyro

case.

The GY401 uses a conductive resin case to reduce

electromagnetic interference. Because the surface of the

case is conductive, metal objects may cause a short

circuit.

Insert the connectors fully.

If a connector works loose due to vibration during flight,

control may be lost and result in a dangerous situation.

Always check the direction of operation of

the servos.

If you attempt to fly the model when a servo operates in

the wrong direction, the fuselage will spin in a fixed

direction and enter an extremely dangerous state.

Operation Precautions

Never move the fuselage for about 3 sec-

onds after turning on the gyro power

(shared with receiver).

Since the data inside the gyro is automatically initialized

as soon as the power is turned on, if the fuselage is

moved, the neutral position will change. If this occurs,

FUTABA CORPORATION

Makuhari Techno Garden Bldg., B6F 1-3 Nakase, Mihama-ku, Chiba 261-8555, Japan

Phone: (043) 296-5118 Facsimile: (043) 296-5124

©FUTABA CORPORATION 2000, 7

Special Markings

Pay special attention to the safety at the parts of this manual that are indicated by the following marks.

Mark Meaning

Procedures which may lead to a dangerous condition and cause death or serious injury to the

user if not carried out properly.

Procedures which may lead to a dangerous condition or cause death or serious injury to the

user if not carried out properly, or procedures where the probability of superficial injury or

physical damage is high.

Procedures where the possibility of serious injury to the user is small, but there is a danger of

injury, or physical damage, if not carried out properly.

Symbol: ; Prohibited ; Mandatory

Check the operating time of the receiver,

gyro, and servo batteries at the adjustment

stage and decide the number of remaining

flights while allowing a margin.

turn the power off and on again. When turning on the

power, set the transmitter switch to the AVCS position

and turn on the transmitter power switch, then turn on the

gyro power.

Do not operate the rudder trimmer while

flying in the AVCS mode.

When the power is turned on, the GY401 assumes that

the rudder stick is in the neutral position. If the rudder

trimmer is moved during flight, the neutral position will

change.

Avoid sudden temperature changes.

Sudden temperature changes will cause the neutral

position to change. For instance, do not fly the model

immediately after removing it from inside a heated

vehicle in the winter and an air conditioned vehicle in the

summer. Let the model stand for about 10 minutes to

allow the temperature inside the gyro to stabilize before

turning on the power. Also, consider sudden temperature

changes when the gyro is exposed to direct sunlight or is

installed near the engine. Take measures so that the gyro

is not exposed to direct sunlight.

When using the gyro in the AVCS mode,

set revolution mixing to 0% or OFF.

In the AVCS mode, all rudder corrections are made by

the GY401. Therefore, if rudder mixing is ON, the model

will operate the same as if the neutral position changed.

Using the AVCS mode correctly

An AVCS gyro is an angular velocity command type gyro. The gyro con-

stantly compares the transmitter rudder operation signals and gyro internal

reference signal (transmitter rudder neutral signal) and controls the helicop-

ter tail rotation speed accordingly. Therefore, for the AVCS function to

operate normally, the rudder neutral signal must be memorized in the gyro

before flight.

•Rudder neutral signal memorization methods

[Method 1] When the gyro power is turned on, the transmitter rudder signal

automatically received at that time is assumed to be the neutral signal and

is memorized. The gyro is normally used in this state.

[Method 2] Rapidly switch the transmitter sensitivity switch between the

AVCS and normal modes at least 3 times at a 1 second or shorter internal,

then set the switch to the AVCS mode position. The monitor LED flashes

instantaneously and the rudder signal is memorized. If the trimmer was

moved during flight, the memorized neutral position can be updated to the

current neutral position by repeating this operation. When performing this

operation, land the model and hold the rudder stick in the neutral position.

•Rudder neutral check method

In the AVCS mode, the servo does not return to the neutral position even

when the rudder stick is returned to the neutral position. When you want to

check the servo neutral position during linkage neutral check, etc., select

the normal mode, or remain in the AVCS mode, and move the rudder stick

left and right at least 3 times at an interval of 1 second or less, then imme-

diately return the stick to the neutral position. This operation returns the

rudder servo to the neutral position.

•AVCS mode usage precautions

In the AVCS mode, always set revolution mixing to OFF. If revolution

mixing (pitch->rudder mixing) is ON, the pitch operation signal changes

the rudder neutral position. The gyro judges that an angular velocity com-

mand was received and rotates the tail, therefore, the neutral position

changes.

The model flies in the same rudder trim position (including sub trim) as

when the power was turned on (neutral position memorized in the gyro).

When flying in the AVCS mode, set the rudder trim to the same position

under all flight conditions, including hovering and idle up. In the AVCS

mode, the gyro automatically trims the rudder so that trimming during

flight and other precision rudder trim adjustments are unnecessary.

Other precautions

•DS switch setting precaution

When the DS switch is set to the ON position, the rudder servo is driven by

approximately 270Hz high-speed pulses. This mode is for use with Futaba

digital servos only.

When using servos that are not compatible with high-speed

pulse drive, other than digital servos, never set the DS switch

to ON.

The servo may be destroyed.

•Operation of trimmers, etc.

Miniature trimmers and switches are used with the GY401 to reduce its

size. When operating the trimmers and switches, always use the miniature

screwdriver supplied and do not apply excessive force.

•Servo small step operation

When the model is static, the servos may move a small step. However, this

is because the gyro sensitivity is set to a high value and is normal.

One point advice

•Relationship between servo horn length and gyro sen-

sitivity

Gyro sensitivity also changes with the length of the servo horn.

When the sensitivity is too low, length the servo horn. Conversely, when

hunting does not stop, shorten the servo horn.

1 2

Summary of Contents

Page 1 - ET CONTENTS

FEATURESFOREWORD12•AVCS systemSince rudder trim changes caused by wind and other meteorologi-cal changes and front, rear, forward, reverse, and other

Page 2 - Flight adjustment

5USEMount and adjust the GY401 as describedbelow.Use the miniature screwdriver supplied andoperate the GY401 switches and trimmers sothat excessive fo

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