Skookum Sk-gps User manual

SK-GPS

Instruction Manual

Rev. 1.10 – August 1, 2014

©Skookum Robotics Ltd.

Ta le of Contents

Safety .......................................................................................................................................................................................................... 1

Box Contents............................................................................................................................................................................................... 2

Getting Started............................................................................................................................................................................................ 3

SK GPS Internal Blue LED States ............................................................................................................................................................. 3

Swash Bump at Init ................................................................................................................................................................................. 3

Mounting the SK GPS.................................................................................................................................................................................. 4

Connecting the SK GPS ............................................................................................................................................................................... 7

Connecting the Superbright EX LED............................................................................................................................................................ 8

Configuring the SK GPS Using the PC Interface .......................................................................................................................................... 9

GPS Responses (Functions)................................................................................................................................................................... 11

Calibrating (Swinging) the Compass ......................................................................................................................................................... 17

Using the SK GPS....................................................................................................................................................................................... 19

Warranty and Technical Support.............................................................................................................................................................. 21

Safety

An R/C helicopter is not a toy and can cause serious injury to people or damage to property. Use of this gyro places a flight control

computer (the SK720) between the radio receiver and the servos that position the helicopter’s controls. Loss of control of the

helicopter may result if the SK720 is mistuned or set up incorrectly. See the Warranty and Technical Support section for warranty

information.

WARNING: Stand clear! Always test fly in an area away from spectators and keep yourself at a safe distance when flying the

helicopter, especially after any change in the gyro’s setup or tuning. DO NOT stand closer than 10m (30 feet) from the helicopter

during test hovers or any other flying. Keep bystanders clear of the flight area at all times.

WARNING: Always “safe” the motor before you use the PC setup software or SK LCD terminal to set up or tune your SK 720.

Basic safety practice is to kill the engine on a nitro RC helicopter or disconnect the motor or main battery on an electric RC helicopter

whenever the heli is behind the flight line or is being adjusted in any way.

Box Contents

The SK GPS includes:

• The SK GPS unit

• Anti vibration kit for the SK 720

• Tri color super bright External LED

• Two 4 pin connecting cables

• Mounting tape for the SK GPS

Figure 1 - The SK-GPS Module, LED and connecting cables

Getting Started

The SK GPS uses the same setup software as the SK 720. However, you will need to upgrade the setup software and SK 720

firmware to the latest versions (3.30 software, 3.30 firmware as of Feb, 2013) in order to set up and use the GPS module.

SK-GPS Internal Blue LED States

There are five (5) LED indicator states for the SK GPS. These states are shown in the table below:

Figure 2 - SK-GPS LED Patterns

LED State Mode

Solid Good satellite lock

Slow Flash Searching for satellite lock

Fast Flash Error

Short Single Blinks Compass swing mode, Yaw

Short Dou le Blinks Compass swing mode, Nose Up

A demonstration of the different LED states can be found on our Youtube channel

(http://www.youtube.com/user/SkookumRobotics)

Swash Bump at Init

Normally, when the SK 720 finishes initializing it will “bump” the swashplate up and down to show it’s ready to fly. If the SK GPS is

connected, the swash bump will not happen until the SK GPS also has a satellite lock.

If your heli is a multicopter, the SK 720 will instead give two very short pulses of all the motors.

Mounting the SK-GPS

The SK GPS can be mounting in four different configurations. In all configurations the module’s antenna (the black dome) must

point upwards in order to receive a good signal. It should also have a clear view of as much of the sky as possible, without carbon

fibre or metal covering it or directly beside it. Plastic or thin fibreglass canopies are normally ok.

The GPS module must also be mounted 90° to the helicopter’s frame, aligned with the main shaft, with its back parallel to the tail

boom. As a result, the SK GPS can be mounted label-left, label-right, label-front, and label-aft. The diagram below displays an

example of each mounting position on both a single rotor helicopter.

If you mount your GPS module on your heli’s tail boom, make sure to position it no more than half way to the tail assembly. If you

mount the GPS module away from the helicopter’s centre of gravity, be sure to change the Offset setting in the software. An

explanation of the Offset setting can be found in the Configuring the SK-GPS section.

Figure 3 - SK-GPS Mounting Positions

Figure - Antenna Configuration

The 3 axis magnetic compass built into the SK GPS is sensitive to some of the magnetic components on helicopters. Specifically, the

SK GPS should be mounted at least:

• 10cm (4”) from ESCs

• 15cm (6”) from motors

• 5cm (2”) from servos

The cable for the GPS should also be at least 3cm (1”) from motor or battery wires, and should be at least 1cm (0.5”) from servo

wiring. It is OK for the GPS wire to cross servo wiring at 90 degrees.

When mounting the GPS unit, it may help to watch the Magnetic Field Strength display on the GPS form in the setup software. Aim

for a mounting location with a field strength under 2. Note that often bolts can be strongly magnetized, so replacing them with

stainless steel bolts may help.

The location of the GPS unit’s magnetic sensor is shown in the image on the left, on the

upper right corner of the unit. The sensor itself is on the underside of the circuit board.

The metal ring included with the GPS cable is a ferrite bead, not a magnet. This ring

reduces high frequency electronic noise. Other tips for reducing EMF and electronic noise

include:

• If cables have to cross, they should cross at 90°

• Don’t run ESC or main battery wires near servo cables, the SK GPS, or its cable

• Don’t run any other wire in parallel with the GPS cable

• Avoid mounting near magnets or bolts (any steel bolt can be considered a magnet)

Connecting the SK-GPS

The SK GPS module connects to the SK 720s GPS port using the included 4 pin cable. The second port on the SK GPS module is used

for future Skookum accessories.

Figure 5 - Connecting the SK-GPS to the SK-720

Connecting the Super right EX-LED

The SK GPS comes with a super bright tricolor version of the SK EX LED (Red / Green / Blue). It has one 3 wire jumper that connects

to the SK 720’s EX LED port, and a standard power cable that can be connected to any 5 to 8 volt source.

Figure 6 – Connecting the SK-LED2

All except blue SK 720's with a "Traditional Receiver"

Only blue SK 720’s with a “Traditional Receiver”

Figure 7 – SK-LED2 Patterns

LED State Mode

Solid Red Initializing

Solid Green Ready for normal flight (GPS not availa le)

Solid Blue Ready for GPS assisted flight

Flashing Blue / Green GPS has primary control of Heli

Green with Red flicker Vi ration Alarm

WARNING: DO NOT look directly at the Tricolor EX LED. It is extremely bright and only intended for use while flying the heli.

Configuring the SK-GPS Using the PC Interface

The interface used for setting up the GPS module is launched from the Utility menu of the setup software, under Setup GPS. The

upper half of the GPS interface displays the live data from the GPS. This data can be used for general reference, and to double check

position and compass data when desired. The lower half of the interface sets the orientation and functions of the GPs module.

1. GPS Orientation

The direction the GPS unit’s label faces. Details regarding mounting the SK GPS

can be found on page 4.

2. Fore-Aft Offset

This is the distance of your GPS module from the helicopters centre of gravity

(COG). On a single rotor heli, the COG will be the main rotor shaft. On a

multirotor heli, the COG will be the balance point. If the GPS is behind the

main rotor shaft, this should be negative.

3. Scale Heli

Click this box if you have a single rotor helicopter that hovers at or around mid

stick on the collective.

4.a. GPS Control Switch 1 Position 1 Mode

This box selects the GPS function for the middle switch position (for 3 position switches) on the Tx channel that you selected GPS

switch 2 in the “Control” tab on the main setup software window. This switch mode is not supported on 2 position switches.

4.b. GPS Control Switch 1 Position 2 Mode

This box selects the GPS function for the lo er/do n switch position (for 2 and 3 position switches) on the Tx channel that you

selected in the “Control” tab on the main setup software window.

ote: The top/up switch position on all GPS control switches is “Manual” or “Off” mode. No GPS functions are enabled when the

switch is in the top/up position. Reverse the channel in your transmitter if you prefer the lo er/do n position to be off.

5.a. GPS Control Switch 2 Position 1 Mode

This box selects the GPS function for the middle switch position (for 3 position

switches) on the Tx channel that you selected for GPS switch 2 in the “Control”

tab on the main setup software window. This switch mode is not supported on

2 position switches.

5.b. GPS Control Switch 2 Position 2 Mode

This box selects the GPS function for the lo er/do n switch position (for 2 and

3 position switches) on the Tx channel that you selected in the “Control” tab

on the main setup software window.

ote: The top/up switch position on all GPS control switches is “Manual” or

“Off” mode. No GPS functions are enabled when the switch is in the top/up

position. Reverse the channel in your transmitter if you prefer the lo er/do n

position to be the off position.

6. Altitude Floor

The altitude floor sets the level where the SK GPS will bail the heli out. The lowest setting for the altitude floor is 8m (25 ft),

however we recommend setting it to at least 10m (30ft).

7. Alt Hold Gain

Altitude Hold Gain is similar to the Cyclic and Tail gain you set in your SK 720. While the cyclic and tail gains set how hard the SK 720

will try to control your heli in aileron, elevator and rudder, the Altitude Hold Gains set how hard the SK GPS tries to control the

collective.

Set the altitude Hold Gain the same way as you would the Tail or Cyclic. Increase the gain until the heli oscillates, then back the gain

down until the oscillation stops. Cyclic and Tail gains for GPS control do not need to be adjusted for different helis.

GPS Responses (Functions)

The SK GPS has nine available flight modes. Any two of the modes can be set to a three position switch on the transmitter. One

position on the switch will always set the GPS to “manual” control to give full control back to the pilot. We strongly suggest that

your first flight test ith the GPS system should be ith Position or Altitude hold modes.

If you have two channels available, you can use two GPS control switches, allowing four active GPS aided modes. Note that switch 1

will always be dominant over switch 2. So if you select a GPS mode on switch 1, switch 2 will be ignored.

Home Positions ote:

Each GPS switch can also have its own “home” position and direction, which is used for the Go Home, Grid, Radial, and Point modes.

Both home positions and directions are initially set the first time throttle is raised.

You can re set the home position of a GPS control switch by toggling the switch from “manual” to position 1, then back to manual, 5

times quickly. The system will tell you that switch’s home position has been re set by slowly flashing blue on the superbright LED.

Altitude Control ote:

The collective stick position controls altitude in all GPS control modes except for go home or rescue modes. So it must be set to

“zero climb” when you enable the GPS control mode. Otherwise, the altitude will slew down or up depending on the transmitter

stick position. The system will hold altitude for up to 2 seconds before it responds to the stick position.

If you are flying a multicopter, or have selected “Scale Heli” on the GPS setup form, “zero climb” is at center stick, so be sure that the

collective is centred while in any GPS control mode (except go home or rescue). For other helis, the hold altitude position is at

about +1/3 positive stick (near the normal hover stick position for a 3D heli).

Aileron/Elevator Control ote:

While in most GPS control modes, you can slew the heli around using the cyclic stick (aileron/elevator). There is a deadband near

the center, so small stick movements will not change the set position. Do not make large stick movements, because 50% stick travel

will give full speed, and more will be ignored. This is to prevent upsets if the GPS system loses its position fix and drops to manual

mode.

Position Hold

Setting the GPS to Position Hold will cause the SK720 to automatically hover the helicopter at one

position. While in this mode, control inputs from the transmitter are interpreted as “slew” commands.

Up/down collective slews the helicopter position up and down while the cyclic slews the helicopter’s

position set point in the direction of the cyclic control input, as illustrated at right. Yaw (rudder) control

will still work normally while in position hold.

Altitude Hold Only

Setting the GPS to Altitude Hold Only will take collective control away from the pilot. Up/down collective

commands from the transmitter will slew the altitude set point up and down. Cyclic and tail control will work normally.

Rescue Modes

The SK GPS has three different rescue modes. All will stop the heli’s motion, level it out, and orient it tail in (tail towards you). The

difference between the three modes lies in when the SK GPS bails the heli out. Once the heli is stopped level and above the altitude

floor it will go back in position hold mode until you reset by going back to manual mode. The tail in direction is set when the SK GPS

first gets its satellite lock.

Rescue ow

This version of the SK GPS’ rescue functions allows you to fly normally until you flip the switch to trigger rescue mode.

Rescue Hard Floor

This version of the SK GPS’ rescue functions allows you to fly normally until you go below the set minimum altitude. Once the

minimum altitude is reached, the SK GPS will stop the heli’s descent and go into rescue mode (described on the page above).

Rescue Soft Floor

The ‘soft floor’ rescue bails your heli out at or before it reaches the set minimum altitude. In this mode, the SK GPS will

calculate how much distance is needed to stop in time, and will activate rescue mode if it thinks it is running out of room to

recover before going below the floor. This allows you to set the rescue floor lower, however it gives less control to the pilot.

Lock Grid

Setting the GPS to Lock Grid will cause the SK720 to automatically hover the helicopter at one

position. While in this mode, control inputs from the transmitter are interpreted as “slew”

commands. Up/down collective slews the helicopter position up and down, and cyclic slews the

helicopter’s position in the direction of the cyclic control input, as illustrated at right.

This mode differs from normal position hold mode in that cyclic commands slew the helicopter’s

position the same direction, no matter which direction the nose is pointed. So for example if you first

throttled up with the nose pointed away from you, then left cyclic moves the helicopter to your left,

regardless of which way the nose is pointing.

Lock Radial

Setting the GPS to Lock Radial will cause the SK720 to automatically hover the helicopter at one position. While in this mode, control

inputs from the transmitter are interpreted as “slew” commands. Up/down collective slews the helicopter position up and down

while the cyclic slews the helicopter’s position set point in the direction of the cyclic control input, as illustrated below.

This mode differs from normal position hold mode in that left/right cyclic commands slew the helicopter’s position in a circle about

the home position and fore/aft cyclic slews the helicopter’s position away or towards the home position. Similar to the “Lock grid”

mode, the helicopter slews the same direction, no matter which way the nose is pointed.

Lock Point

Setting the GPS to Lock Point will cause the SK720 to automatically hover the helicopter at one position. While in this mode, control

inputs from the transmitter are interpreted as “slew” commands. Up/down collective slews the helicopter position up and down

while the cyclic slews the helicopter’s position set point in the direction of the cyclic control input, as illustrated below.

This mode differs from normal position hold mode in that left/right cyclic commands slew the helicopter’s position in a circle about

the home position and fore/aft cyclic slews the helicopter’s away or towards the home position. While in this mode, the SK720

controls the helicopter’s heading so that it always points nose in towards the home position

Return Home

Selecting the GPS to Return Home mode will take all control away from the pilot. The

helicopter will climb in altitude, fly the heli back to a predetermined ‘home’ position then

descend to the ‘fail safe’ altitude. It will then orient the heli tail in and hover above the home

position. Due to safety concerns, the SK GPS will not land a heli automatically.

The home location must be set before Return Home mode will work. The home position is set

when the throttle is first increased after the GPS external LED turns solid blue. The home

position can be reset to a new position (one position for each GPS mode switch) after the

initial home position has been set. Do this by quickly toggling a GPS mode switch on and off

five times.

NOTE 1: Please make sure your home position is a safe distance from other pilots or spectators. Stored home positions are not saved

between flights. The home position location is deleted when the power is turned off.

NOTE 2: As of firmware release 4.0, fail safe return home after receiver signal loss will only work for multicopters.

Cali rating (Swinging) the Compass

Swinging the SK GPS’ 3 axis magnetic compass allows the SK GPS to learn the local magnetic field

distortion caused by your helicopter. You do not have to swing the compass every time you fly the SK

GPS. You do need to swing the compass when you:

• Have moved the GPS module to a different helicopter

• Have mounted the GPS module on a different location on your helicopter

• Are using the GPS with a different SK 720

• Have changed any major equipment on your helicopter, such a servos, ESCs or motors.

To swing the compass, the heli needs to be rotated in yaw (rudder axis) and then pitch (elevator axis).

This should be done outdoors, at least 10m away from power lines, cars, or large metal objects or

concrete pads that may contain rebar. You should also remove your wristwatch and any keys from your

pockets (think airport security). The swing is completed in 7 steps:

1. In the Utility menu, select S ing SK-GPS Compass.

2. Power the SK 720 and GPS. You can do this with your main flight pack, but be sure to

disconnect motor wires for safety. We recommend, especially with multirotors, powering

the SK 720 and GPS with a BEC. Your transmitter doesn’t need to be on.

3. Wait for the SK 720’s LED to turn green, and the SK GPS to show blue.

4. Hold the heli in a level attitude and start rotating slowly as shown in the top image at left.

The SK GPS’ LED will give short single blinks to show that it is in compass swing mode. You

can rotate left or right, and the rotations should take about 10 seconds each. Turn around

until the SK GPS’ LED blink pattern changes to a short double blink, normally 2 turns.

5. Tumble the heli on its pitch axis, taking care not to wobble the heli in the roll and yaw axes.

You can rotate nose up or nose down during this phase of the swing. Like the horizontal

swing, this should take about 10 seconds per rotation. Keep tumbling the helicopter (see

image on the previous page) until the SK GPS’ LED blink pattern changes to slow blinking or a steady blue. Normally it

takes only 1 2 rotations.

6. Place the heli back on the ground, and wait 10 seconds. You can check the status of your compass swing by connecting

the helicopter to a computer to view the “Setup GPS” window in the setup software.

7. If the compass was swung properly, the LED will have returned to the solid “good satellite lock” LED. A fast flashing

SK GPS LED means that the compass swing failed.

Any failure related to swinging the compass will shut down GPS functions. Compass swing failures include:

• Compass not done at all

• Changed GPS orientation

• Failed compass swing

Compass swing related failures are indicated by an “Invalid Compass S ing” warning in the GUI’s setup window, or an error flash

from the GPS unit itself.

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