Saturday, December 26, 2015

Hexacopter First Flight

I managed to get the Hexacopter to fly after a few flips on takeoff.  It turns out that the motor configuration and wiring for a Pixhawk is not intuitive or well documented.


  1. You have to search through DIYdrones forums to find the information here.
  2. Connect motors 1 to 4 to Pixhawk inputs 1 to 4, same as a quadcopter.
  3. Connect motor 7 to Pixhawk input 5
  4. Connect motor 8 to input 6
Bingo!

Tuesday, December 15, 2015

Quad to Hex

I decided to go further and build a hexacopter.  I was able to use my existing 550 quadcopter parts and purchase an inexpensive hex frame from Banggood.com, two more motors, two more ESCs, and use some extra landing gear parts.  Here is what I have so far:







Saturday, December 12, 2015

Flysky i10 PPM

A while back I reviewed the Flysky i10 radio.  It is a great radio for the price, but I needed PPM output from the receiver in order to feed my Pixhawk.  PPM is a single wire interface for all channels, in place of the one-cable-per-channel PWM interface, which is about 40 years old.

The manual tells you nothing about how to do this, but the online forums were filled with people saying it could be done.  I tried everything, and could not find a way to do it.

Finally, I found a bunch of postings about a very helpful fellow at Diamond Hobby, Jim Ogorek, who might be able to help (email: jim@diamondhobby.com).  In spite of the fact that I bought the radio through another retailer, Amazon, he helped me by sending me the update software for the radio.  Note that there are two versions, US and China.  I needed China because my radio showed up as a "CN" device on windows.

After running the software on my PC and connecting up the radio, I was able to update the transmitter, and it then updated the receiver, and bingo, I had PPM!  You go to the receiver menu on the transmitter and there is a simple check box for PPM and it enables PPM output on ch1 of the receiver.  Works like a charm.

Friday, December 11, 2015

Eachine Racer 250 - How Does Openpilot Compare to APM/Pixhawk


I saw a good deal on Banggood.com for a small ARF (Almost Ready to Fly) Quad called the Eachine Racer 250 and went ahead and purchased it.  It is a 250 sized unit with the FPV built in, includes a battery, and charger, and cost around $125.  I added a spare Orange DSMX receiver and a Spectrum DX4e transmitter and was up and running!  It sends video to my 5.8 GHz integrated receiver-monitor and works like a charm.  Build quality is good for the price, packaging was good, and it is designed well.  As usual, there are NO INSTRUCTIONS from the Chinese manufacturer in the box and you have to hunt around on the web to find out how to set it up.  I found a few good Youtube videos and they guided me through setup without a problem.

The only thing that was challenging was my lack of knowledge of the flight controller, the CC3D, an open source flight controller that is somewhat different from the APM or Pixhawk.  I again queried the web and found the ground controller for Openpilot, which supports CC3D hardware.  I downloaded the software, installed it, connected USB to the quad, and followed the instructions in the video.

The quad flew, but was very sensitive to control inputs, too much for my flying skill.  I again went to the web, found some tutorials, and tried to fix the settings.  The tutorials were out of date so I went to the wiki, which seems to be permanently down.  I then posted a question on RCgroups.com and got some information.

Unfortunately, there seems to be a schism in the Openpilot community and it has split into three factions: Taulabs, Librepilot, and Openpilot.  While Openpilot works, it does not seem to have as much support as it used to.  The other 2 options seem to be works in progress.  APM and Pixhawk/PX4 are definitely better options if you have a choice.

But I did figure out how to desensitize the quad using the current Openpilot and it flew well in a couple of outdoor test flights.  Stay tuned for more info.


Thursday, August 20, 2015

Short Review: Olympus Air as Drone Camera

As a dedicated Micro 4/3 Mirrorless camera user, I thought it would be great to try the new Olympus Air A01 camera.  This is similar to a product put out by Sony which attached a photo-quality lens to a Smartphone.  However, the unique ability of the Olympus Air is that it will take any interchangeable Micro 4/3 lenses.  Price is low: approximately $299 street price in USA for body only.

Olympus AIR A01

I received the AIR yesterday and rushed to get it charged (about 4 hours) and get it set up.  It is not a perfect product and there are a few warts, some of which could be fixed in future software.  The cylindrical body of the AIR is quite small and light, and it communicates with your IOS or Android device via Bluetooth and Wifi.  This has some issues as you disconnect from your home wifi to access the AIR wifi, as the AIR sets itself up as an access point.  You also have to download the correct Olympus AIR app, and set a few things up.  The normal mode of use is to clip your smartphone to the back of the AIR and use it as a viewfinder and remote control.  I tried this and it works as advertised.

The AIR has the following useful qualities for drones:

  • Professional quality sensor (16MP) and lenses, Full HD at 30 fps
  • No added functions, buttons, screens, & grips which are normally part of a photo quality camera - you don't have to lift a whole DSLR to get Photo quality
  • Tripod mount - invaluable as you can easily adapt it to existing gimbals and mounts
  • Interchangeable lenses
  • Autofocus, image stabilization, face detection, long list of DSLR type features
  • Ability to turn off wireless connections so they do not interfere with drone radio control
  • Built-in battery
  • Light - I measured 368 gm for the AIR with a Panasonic 14-42mm zoom lens, which is not the lightest 4/3 lens by any means.  The AIR alone is about 150 gm.
  • Open API interface so software could be written to control the camera and lens in flight
I rushed to get it installed on my test mule drone, an SK450 Deadcat.  I found a tripod mount that attached to my existing Gopro mount, but it was not ideal as it mounted the AIR too high and too far forward, but it sort of worked (see photos).

There are a few drawbacks to the AIR, which I will list below, mainly concentrating on drone-specific items:
  • The setup is complicated, you have to read the instructions carefully and follow them
  • The app is not intuitive, some updates needed here
  • Wifi video transfer to smartphone takes a long time for some unknown reason, about 10 minutes for a 3 minute video.  I recommend connecting the AIR via USB to your PC where the transfer took about a minute.
  • You have to keep your smartphone hooked up to the AIR by wifi and bluetooth, and the smartphone will try to go back to its home network if you turn off the AIR or connection is lost, causing you to have to go back to the setup menu and reselect the right networks again.
Olympus AIR with Panasonic 14-42mm lens

SK450 Deadcat with AIR

Closer View of Not-So-Great Mount



Wednesday, August 19, 2015

Always Keep Two Quadcopters

I learned again that it is a good idea to have two quadcopters:

  1. One to fly
  2. One that you crashed and is being repaired
Another important lesson was not to fly near trees, as Quadcopters Love Trees.

Thursday, August 13, 2015

Quanum Q-2D Brushless GoPro 3 Gimbal Test

Gimbal Mounted on S500 Quadcopter


Attached a 2D camera gimbal to the drone and did a quick test flight with my Gopro Hero3+ Black.

The included Gimbal mount on the S500 frame was not useable as there was only about 1-2 cm of clearance between the bottom of the gimbal and the ground and I was sure that the gimbal would be damaged in a hard landing (see previous review of the S500 frame).

The gimbal is the HobbyKing Quanum Q-2D Brushless GoPro 3 Gimbal.  I could not get it to work attaching the gimbal controls to the Pixhawk so I connected the servo cables to the FlySky i10 receiver directly.  The only adjustment was limiting the maximum throw on the transmitter for the gimbal controls to +/- 30%.  This makes the gimbal less sensitive to the movement of the rotary controls on the transmitter.

Successful indoor Test Flight is shown below:

Unsuccessful outdoor test flight (gimbal worked, quadcopter not so much) is also below:

Tuesday, August 11, 2015

Hobbyking S500 Frame Review

S500 Quadcopter
I am building a new quadcopter for higher quality photography using the hobbyking s500 frame, which is similar to the sk450, but slightly larger.  It is now flying and I can comment on its pros and cons.

Pro

  • Slightly stiffer arms than Sk450
  • Plenty of space for electronics
  • Higher landing gear to allow for camera gimbal
  • Adjustable mount for gimbal - can shift gimbal forward and backward 
  • Integrated pcb for power distribution 
  • Spare parts available
  • Low cost 

Con

  • Landing gear not too sturdy 
  • Landing gear too low to use included adjustable mount with 2 axis gimbal, have to hard mount to pcb
Note Top of Landing Gear, too flexible, not well attached to frame

I used sunnysky 2212 motors and they are much better than the turnigy motors on the SK450 - powerful, quiet, less vibration, smaller. I was also able to use my pixhawk controller which would not interface properly to the turnigy plush ESCs when I tried it on the SK450. For the S500 build, I used low cost Spider ESCs with SimonK firmware, which worked well with the pixhawk. Carbon fiber props and the previously reviewed Flysky i10 radio rounded out the build. 

First outdoor test flight is shown below. 

Summary 

The S500 is a good frame for a camera quadcopter, but it is not recommended for a beginner builder. Modifications are needed for camera mounting, the landing gear, and perhaps for power wiring so it helps if you have some experience with building  quads. 

S500 fully assembled with Gimbal, Telemetry

Tuesday, August 4, 2015

Flysky i10 Review

I recently bought the Flysky i10 radio for my latest quadcopter project.  I love this RC unit.

The system, as delivered, includes the transmitter with rechargeable battery, receiver, external voltage sensor, rpm sensor, and temperature sensor along with a useful manual on CD.  The manual is actually well written and useful, unlike many Chinese radios.  Build quality seems good, no obvious cheap parts or poor assembly.

Transmitter

The transmitter has a touch screen interface, somewhat Android-like, and it is easier to use than the older text menu driven systems.  You can set up almost anything through the interface: limits, mixes, switch assignments, delays, failsafes, etc.  The transmitter itself is slim, with rubberized grips, making it easy to hold.  There are many different switches and knobs which can be attached to any channel.  This was great for the quadcopter as you could get 2, 3, or more flight modes on one switch or knob without using cumbersome control mixing.   Camera gimbal control is also easy with the two variable control knobs on the top corners of the transmitter, easily manipulated by your index fingers while your thumbs work the joysticks. Joystick feel is good.  The transmitter can also be programmed via USB, which I have not tried yet, and it also has an SD card for storage.  Telemetry data from the receiver and sensors is shown on the transmitter LCD display.
Home screen
Icons for customizing transmitter

Receiver

The ia10 receiver has 10 channel ports which work well with my Pixhawk and standard servos.  It also has an "Ibus" which can be used to output PPM (I have not figured this out yet), or take inputs from the telemetry sensors.  Ibus documentation is not great, so check back in a while and see if I can figure out how to use it for PPM and other purposes.  Range seems very good in my experience.
Receiver as installed on my Quadcopter


Testing

I installed the system on an S500 quadcopter and used a generic PPM converter to generate PPM for my Pixhawk controller.  It was relatively simple to set up the control functions, map the flight modes to a three position switch, and range check the system.  Performance during test flights and a long hot outdoor flying session was excellent.


Summary

I highly recommend this radio for quadcopters and believe it will also be an excellent choice for airplanes, traditional helicopters, and other vehicles.  The price, about $200 US, is unbeatable for the value received.
Sensors included with the System

Monday, August 3, 2015

First Successful Quadcopter Autonomous Mission

After all the adjustments to the Deadcat SK450, I took it out to the local "park" (remote muddy field) to try a mission.  It was a simple mission, fly to a few waypoints, circle at one waypoint, return to launch, then land.  It actually worked!  Here is the video:



Thursday, July 30, 2015

Getting Telemetry Working, A Short Review of Excelvan Radio Telemetry Kit 915Mhz

I recently purchased a small Telemetry module from Newegg.com for about $25, it runs on the unlicensed 900 MHz band.  It was quite easy to hook it up to my Hobbyking Micro APM and now I can monitor the Quadcopter while in flight, just as if it was connected to my PC via USB.  No need to connect USB on the ground, as this telemetry connection handles all communications.

A new cable must be made using the supplied telemetry cable from the telemetry module and the one supplied with the APM.  Also remember to connect as follows:
Telemetry Module with black antenna

Telemetry ModuleAPM
5V5V
GndGnd
TXRX
RXTX


The PC connection was also painless, stuck the module into a USB port and the driver loaded automatically onto my Windows 7 laptop.

The only other trick is to select 57.6Kbps in Mission Planner to get the link to work.

Note: Telemetry module is from Excelvan and is called "Radio Telemetry Kit 915Mhz Module for APM APM2.5 2.6 Pixhawk PX4 RC Multicopter Quadcopter" and is available on Newegg.com

Update-Pixhawk Test

I also purchased a unit for use with my Pixhawk-S500 quadcopter covered elsewhere on this blog.  This time, I could use the included cable to connect the telemetry unit to my Pixhawk, although I had to shave a little plastic on the Pixhawk end, as the Pixhawk uses unusual connectors.  As with the APM, I set the rate to 57600 and was connected to Mavlink on the Pixhawk.  Works like a charm.

Monday, July 27, 2015

More Fixes to the SK450

I am plagued by poor loiter on the SK450 and have made further changes to improve things:


  1. Fixed the slop or wobble in the GPS mast.  It turns out that the cheap mounts rely on being able to screw down the knurled flange until the mast mount inside is snug.  However, a lot of them cannot be tightened.  I added a plastic washer from an old prop to the mast as shown and the wobble stopped.
  2. The APM mount was maybe moving in flight, so I remounted it with the special vibration reducing foam rubber and I secured the USB cable better so it could not move the APM.
  3. Added a little foam rubber inside the micro APM case to ensure the barometers were not getting fooled by the prop wash.
  4. Wait 5 minutes after power on to get the GPS and all sensors stable before trying a flight.
  5. Added some practice golf balls to the landing gear so they do not catch in the grass when taking off or landing.
  6. I very carefully recalibrated the accelerometers, making sure that the quad was absolutely level during the first stage of calibration.  This made a HUGE difference versus my previous "it looks level" calibrations - the test flight was much beter with much less yaw and pitch on takeoff and during flight.
  7. Made a stand out of a medium size plastic storage container as shown:

Monday, July 20, 2015

Pixhawk Versus APM Comparison Review

This blog entry compares two flight controllers from the Ardupilot 3DR-Open-Source stream: the generic APM 2.X controller and the Pixhawk.  I am an intermediate multirotor builder and flyer, so this comparison will focus on functionality and useability, not on advanced features.  Also, this review is based on my experience with 5 different APM modules (none sourced from 3DR) in three different physical forms: standard, mini, and micro (also called mini by some) sourced from Hobbyking and generic Chinese manufacturers.  The Pixhawk is available from multiple domestic and Chinese sources and you should check the reviews to make sure you are getting one with decent build quality.  Each was used with corresponding GPS/Compass units from the same manufacturers.  I built three different quadcopters and used them with different controllers.

Feature/CharacteristicGeneric APM 2.X3DR PixhawkComment
Size/WeightSmallLargerAPM is available in 35x35x5 mm board.  Pixhawk is 81x50x16 mm
CostLowHigher, about 4XAPM with GPS ~$65
QualityVariableBetterInspect a generic APM after you get it for poor soldering, loose USB..
SupportGoodGoodThe best support is from peers on DIYdrones and APM forums
Flight StabilityGoodGoodThis is my experience with a well setup APM and Pixhawk, your experience may vary
AccuracyGoodBetterIt does depend on your GPS and its accuracy.  Pixhawk has a more powerful processor and more memory
Onboard indicatorsPoorGoodPixhawk has multiple LEDs and tones to tell you status, APM has a few LEDs
Ease of SetupModerateModerateMore components to interconnect on Pixhawk, but well documented. Cables and connectors often an issue with APM and documentation must be found on the Internet.
Ability to fly autonomous missionsYesYes
Mission Planner Ground Station CompatibilityYesYes
Flight logging CapabilityGoodBetterPixhawk logs more information and has a microSD for storage. APM has limited storage of most important variables.
UpgradeabilityNoneYesAPM code is now frozen to my knowledge, but Pixhawk software with improvements still being released
Debugging difficultyGoodMore difficultAPMs seem to always work, Pixhawk is more finicky about ESCs, setup, etc.

Overall, both controllers are excellent and have worked well for me.  The APM is a better fit for small quadcopters and is probably better for the beginner builder due to its simpler setup and low cost.  The Pixhawk is very good but it takes more time to set up and it is likely higher quality and performance, so it works well in larger camera quadcopters and similar expensive vehicles.

APM equipped SK450 "Dead Cat" Quadcopter
S500 Quadcopter with Pixhawk

Saturday, July 18, 2015

Fixed the Loiter

Well I fixed the Loiter problem, the quadcopter will now hold position and altitude on command.  The changes were detailed in the previous blog post
  1. Put in a new GPS.  
  2. Improve power feed to the controller and receiver by using a UBEC (battery eliminator) instead of the power feed from the ESCs.  
  3. Get rid of extra wires in the controller wiring harness.
  4. Performed an indoor test flight and analyzed logs.  
  5. Performed an outdoor test flight which was successful.
I also included a parameter change:

- changed INS_MPU6K_FILTER from 0 to 20 to filter out barometer fluctuations

Tuesday, July 14, 2015

Further Enhancements

After the exciting flight last week, I had to repair the Quadcopter as one of the arms broke in a landing.  So I decide to make a few enhancements:

  1. Put in a new APM controller and GPS to fix the Loiter issue.  This did not turn out well as the new controller was defective but the GPS seemed to improve things.  The new GPS is Hobbyking brand, old one was a "no-name" with some mods to make the cable work.
  2. Improve power feed to the controller and receiver by using a UBEC (battery eliminator) instead of the power feed from the ESCs.  This is recommended due to the interference from the ESC and I do think  it improved things.
  3. Get rid of extra wires in the controller wiring harness.  Done.
  4. Install new arm.  Did this, I learned from the dearly departed Flying Flowerpot quadcopter that it is almost impossible to properly fix a quad's arm and they are reasonably cheap.
  5. Performed a test flight and analyzed logs.  Seemed to improve things with few glitches on barometer and GPS and more stable flight.  Testing will continue.

Saturday, July 11, 2015

Don't Try Auto if You Cannot Loiter

Learned a new lesson yesterday, should not have needed to learn it, because it is obvious.

If your quadcopter cannot LOITER successfully, don't try an AUTO mission.

I headed over to the local "park" - more like a remote muddy field that the county calls a park - to fly my quad.  The plan was to check out AUTO mode with the program shown in the previous blog entry.  I forgot, or ignored the previous tests that showed that LOITER mode did not work well, the copter bobbed up and down and did not hold position.

So I try taking off in AUTO mode with no luck, then do a manual takeoff and flip the switch for Auto mode.  At first, things seemed OK, then the quad headed for the river, gaining altitude.  Before I could react, it was over the Potomac at about 75 feet, then it dipped below the tree line and I could not see it.  I flipped back to manual (Stabilize) control and thought "that quad is gone".  I hit the throttle to try and bring it back up above the trees and it appeared as a little speck in the distance.  I then was able to bring it back with some skillful (lucky) stick work and land it.  Was I ever lucky!

The saving grace is that it took some great video footage while on its semi-controlled mission.  Also, this is why you should not fly near people, as this could happen to you and someone could get hurt.

Here is the video:

Tuesday, July 7, 2015

Status of the DeadCat SK450

The Deadcat SK450 is working fine.  A few minor modifications:

  • packaged up the APM controller and mounted it on anti-vibration foam
  • added a LiPo batter monitor
  • tidied up some cables
A photo with some details is shown below.


I am also working on a new mission which includes takeoff and landing in the Mission Planner software, see below.


Tuesday, June 2, 2015

Quanum FPVplus Wide-Angle 1080P HD FPV Camera with 5.8GHz Transmitter Review




I recently purchased this camera from Hobbyking with the intent of using it for video recording on my quadcopter and perhaps FPV operation.  The camera takes still photos, videos, and real time video and incorporates a transmitter so you can use it for FPV flying.  It is an integrated alternative to using an FPV camera and separate 5.8 GHz transmitter and it follows the GoPro form factor to a large extent.

After some use, here are my views on this product.

Positives


  1. It uses the Gopro form factor, so it can use Gopro accessories.  It is lightweight.
  2. You need to do some work to adapt this to your quadcopter:
    1. You have to adapt the supplied cable to provide a 12V supply to the camera.  It has no internal battery so it is useless without power.
    2. It has no included mount or tripod threaded hole so you need to adapt a Gopro mount to your purpose.  This can be done with the usual hobby tools.
  3. The video is of acceptable quality, quite good in fact, see the video sample below.  This was taken with no gimbal, a shock absorbing mount, and reasonably balanced props, so it still has some shake.
  4. Construction seems rugged.
  5. With the included transmitter and antenna, it is easy to set up for FPV operation.  I was able to connect the camera to my RX LCD5802 7 inch monitor in about 5 seconds - truly easy.
  6. Downloading the videos to a Mac or PC is easy using the microSD card.  Note that the camera will not work without a card.  Also note that the developers seem to have used Huawei phone software as the base for this product - you will see some directories and files that are unusual for a standard digital camera.
  7. I recommend always connecting the antenna when the camera is powered up.  Some RF transmitters can burn out if they have no load like an antenna.  Don't know if that is the case here, but better safe than sorry.

Negatives

  1. It is difficult to know what mode the camera is in as there is no LCD display and only one LED to provide status.  Spend some time with the very brief instructions on your workbench to familiarize yourself with operation before flying.  Otherwise, you may take off with the camera turned off.
  2. The MicroSD card sticks out and can be easily ejected.  You may want to put some tape over it temporarily so you don't eject it at an inopportune time.  You also need to consider this when you adapt the camera to a Gopro accessory.
  3. You cannot adapt an onscreen display (OSD) to show quadcopter telemetry on your ground screen as the video to transmitter inteface is within the camera and cannot be accessed to insert an OSD card between camera and transmitter.
In summary, I recommend this camera as a simple to set up FPV camera and transmitter system for quadcopters and other UAV.  It is easy to set up, provides good video, and is rugged.

Rear View

Side View with antenna removed
Side view with MicroSD slot, mode switch, connector
Gopro mount modified to accomodate antenna, cable, switch, etc.



Monday, June 1, 2015

Latest flights - SK450 Deadcat

Got three flights in last week and the quadcopter is still in one piece.  The video from the quad is cleaner than before as there is less vibration, but still a bit of jello.

Saturday, May 16, 2015

Balancing a Quadcopter

After a short break, I am back to working on the Deadcat SK450 quad.  One thing I am learning is that balancing the quadcopter is important.

Model aircraft are very sensitive to their point of balance, but I did not realize quadcopters had a similar tendency.

If your quadcopter, properly calibrated with the trims set at 0, tends to go forward or backward slowly after takeoff in Stabilize mode, you are likely nose (forward movement) or tail (backward) heavy.  If your quadcopter is not symmetrically built (left to right across the centerline), you could also see a consistent movement left or right.

The solution is to move equipment to counteract the imbalance.  The battery is usually the easiest thing to move.  The process is like this:

  1. Take a short test hop inside or in very calm winds and note which way the quad wanders.
  2. Move the battery back if you wander forward, or move the battery forward if you wander backward.  Mark the battery's new position with masking tape.  See figure 2 for battery installation (farthest to rear) on my quadcopter when camera is installed.
  3. Try another test hop, see if the quad will hover in one place.  If yes, the balance is OK.
  4. If it still wanders, move the battery as in step 2. and also move the tape.   Take a test hop, see if it is fixed.  Repeat until you get a nice stable hover, something like you see in the video below.  My problem was the quad moving forward consistently, which is now fixed, it still moves from side to side due to my clumsy control inputs.
  5. Once you have the battery in the right spot, leave the tape in place and mark it so you know where to put the battery next time.  See figure 1.
Figure 1 Tape markings for different quad configurations

Figure 2 Battery installed in camera configuration

You may have to do this for different configurations, like with and without camera, so you would have two markings for where to put the battery.

Don't add weight to get a balance unless you really have to.  Adding weight just decreases flight time and dynamic stability.


Saturday, April 11, 2015

Back Up and Running


My Deadcat SK450 is back running and as well as ever, the youtbe proof is above.  The modifications I made:


  1. Replaced 3DR Pixhawk and GPS with Hobbyking Micro APM and no-name GPS.
  2. Removed 3DR power monitoring module.
  3. Used Spektrum DX6i radio and DX610 receiver.
  4. New landing gear shock absorbers (see picture).
The finished unit is shown below:

Reconstructed Quad

The other mods are shown in the following pictures:





Friday, March 27, 2015

Putting Pixhawk aside

Micro APM mounted on standoffs on plywood base

Wider view

After many days of debugging Pixhawk problems with ESC calibration, channel mapping, poor stability.. I put it aside and went back to an APM 2.7 unit for the SK450 dead cat.  The pixhawk seems like a nice unit, but the factory support was mediocre, the warranty is 3 months, and it seems pretty finnicky about ESCs, powering, and such.  Online support from forums is usually helpful but not always and not in this case.

Removing the Pixhawk was reasonably easy but the APM was a pain as it is a micro unit and is not nicely packaged.  I mounted it on standoffs as shown and replaced the GPS with a known good unit as well, let's see what happens.

Friday, March 6, 2015

Drones Today = PC's in the Late 80's


I got the drone back up and running.  It turned out that Mission Planner, the PC software that interfaces with the drone, was loading quadcopter firmware with airplane parameters.  It could be that I mistakenly changed a drop down box that selects the default parameter file, or it could be that Mission Planner did not change the parameter file when I reset the drone software from drone to airplane to drone in order to get a "clean load" of drone software (this is the recommended method for resetting your APM/Pixhawk software).

In reflecting on all the hours spent debugging the problem, and the difficulty in identifying the problem, I think the "Drone Industry" is about where PCs were in the late 80's.  It is not a perfect comparison, but it is reasonably close, check out my table below:

CharacteristicDrones TodayLate 80's PCsPCs Today
Off The Shelf Complete UnitsYes (DJI, 3DR..), but many complaints about the white label productsYes (IBM PC, Apple MAC..), but many complaints about the white label productsAlmost all PCs bought off the shelf and work 1st time
HardwareSomewhat standardized, but incompatibilities are commonStandardized, but incompatibilities are commonPlug and Play for almost all hardware
SoftwareLots of variations, nice user interface over a command line operating system, lots of variables to customize, many bugsA few variations, nice user interface (Windows) over a command line operating system (DOS), lots of variables to customize, a few bugsA few variations, nice user interface (Win or OSX), a few variables to customize with wizards to help, few bugs
Growth RateVery highVery highShrinking as people use more mobile devices
Industry ParticipantsAll small companies (DJI, 3DR, Turnigy..), no leaderIBM, Apple, and Compaq are leaders, many small players as well (Packard Bell, Nortel, ..)A small number of huge well known companies: Apple, HP, Lenovo..

Photo credit: Flickr

Thursday, March 5, 2015

New Drone is Down, Debugging Now

The new Deadcat drone no longer works.  I cannot figure out why and have spent about 6 hours trying everything.  It seems to be related to the Pixhawk flight control unit interacting with the ESC (speed controllers).  Below is a summary of the problem that I sent to 3DR, the designers and manufacturers of the Pixhawk.  I will let you know what happens.

--------------------------------------------------------------------------------------------------------------------------
I might have a bad Pixhawk autopilot.  I bought it in December and it worked fine for about a month.

Here is my config:

SK450 frame
4 x Turnigy plush 30A ESC (red power lead is disconnected - Pixhawk is connected to signal and ground only)
4 x Turnigy Multistar 2216-800kv motors
Pixhawk
3DR GPS module
3DR battery sensing module
Spektrum DX6i Transmitter
Orange R615X receiver
Various turnigy 2200mah batteries
Mission Planner on a PC for ground station

It worked like a charm before, reference this Youtube video (excuse the lousy quality).  Deadcat SK450 Test Flight 1

No crashes, I was still test flying in the basement as it is 20 degrees outside with snow.  I was upgrading it as the R615X receiver has limited range.  So I  tried a new receiver, the Orange R800X, and never really got it to work, then I went back and did the following:

- reloaded arducopter 3.2.1 by first loading the plane software, then reloading the quadcopter software, also pressed the reset button on the pixhawk
- recalibrated all my ESC s manually one by one
- did many full setups: compass, accelerometer, radio, .. calibrations
- checked a lot of the parameters and adjusted them, then set them back if there was no improvement
- verified the radio was working by connecting servos to the receiver and also by doing the manual one by one calibration of the ESCs
- verified the pixhawk was seeing the radio inputs, and was putting out the correct outputs, such as increasing throttle on all 4 output channels when the radio throttle was advanced after arming

Here are the problems that I am seeing:

1. The USB connection fails 50% or more of the time.  I have to power cycle the pixhawk and/or plug and unplug the USB cable.  I tried two different USB ports on my laptop, no difference.  This is pretty consistent for the past 5 days.  It worked fine before.
2. The ESCs continuously complain that the initial throttle input coming from the Pixhawk is not low enough.  Here is a phenomenon I saw today regularly:
  1. I calibrate the ESC by connecting it directly to the throttle output of the receiver, and go through the calibration procedure.  The ESC responds with OK tones.  
  2. I try the motor still connected to the receiver, and it revs up and down with the throttle input.
  3. I move the ESC input over to the Pixhawk, arm the Pixhawk, and then the motor responds properly after arming.  Note that I did not power down the pixhawk or receiver.
  4. I power down the quad (radio, pixhawk etc.), and start it back up.  I get normal startup tones from pixhawk and the ESCs complain that they have no throttle input (this is normal as the safety switch is off)
  5. I turn on safety switch, arm the pixhawk and get OK tone, but the ESC complains that the throttle input is not low enough again.  Motors will not function.
  6. WEIRD!
  7. I also tried calibrating one ESC through the pixhawk instead of connecting to receiver (step 1).  The ESC seems to calibrate successfully.  I execute step 3 successfully.  I get the same problem at step 4.
3. Parameters do not seem to be reliably stored in the Pixhawk.  It keeps resetting the battery failsafe settings and sometimes when I try to write a parameter change via mission planner I get an error "Bad Number", which is not very useful.
4. Now, I cannot get the Pixhawk to connect to either receiver, the previously used and flown R615X or the new R800X.  The radio calibration screen shows no activity, but the receiver is definitely connected to the transmitter as I test it with a servo or connect it to an ESC and can throttle the motor up and down.

I am stumped.  If I had my trusty Tektronix oscilloscope from EE school, I would check the signal on the pixhawk ouputs but alas, I don't have one.