WKM Build Problems

[david.scarbrow]

After what seemed to be months of collecting together all the necessary parts, tools, etc. (including advice, views and ideas from this forum) I finally joined them all up with each other. I loaded and installed the most recent versions of S/W and firmware, downloaded the most recent operators handbook, powered up the machine and set it all up, including the GPS...guess what...everything (well sort of everything) worked as designed first time. It flies like a dream with what I consider to be relative stabilty if I consider the gusty winds conditions it was flying in. I now need to explore the next part of this build which is to do with AP and FPV...I hope my experiences will be the same.

The problems that manifested themselves that made it an almost 'worked as designed' experince are typically more to do with interpretation of instructions and language the end result being that I am not absolutely sure of what to do...eg...is there a foolproof way of seting up RTH...I thought I had followed the instructions OK but when I powered off the radio the machine effectively fell out of the sky. I think it is now probably to do with the settings used in my Hitec aurora 9 radio...anyone got an 'idiots guide' approach to set up RTH successfully ?

Unfortunately for me all my home PCs and laptops are Windows 7 64 bit O/S machines. DHI make reference to simply installing the 64 bit driver in exactly the same way as a 32bit driver...easy...but where is it to download...maybe it is just a matter of that I cannot see the woods because of the trees. I emailed DHI but with no response at all...not even an acknowledgement. I had to resort to using a normal workplace laptop with a 32 bit O/S to overcome that issue...does anyone know where the 64 bit driver is kept ?

The GPS 'dish' and mast are more than a little precarious fixed and balanced on top of my machine but it is going to be so easy to break, probably in the not so distant future...does anyone out there have any experience of using other forms of screening, perhaps like the MK design, that will enable the instasllation of the 'dish' closer to the machine hub without being subjected to electrical interference ?

Oh yes, the machine is a total aluminium framed Bagheera 600 quad, wkm FC, AXI 2814/22 motors, Turnigy Plush 30A ESCs, Flydubution power distribution board, 3S Lipo. Total weight so far is 1.86 Kg and a bit heavier than I would like it to be so I am going to have to do a bit more thinking...views and ideas are more than welcome on this.

I just cannot get my wife to show any real interest in this project so I am on my own here. I am not any where good enough as a 'pilot' to have one hand on the radio and the other hand on a camera but I will provide pics and vids ASAP.

 

[BorisS]

Not completely foolproof but what you can do is instead of using a 3 step switch to have manual Attitude and GPS mode, configure the switch to let you manually trigger frail safe.

Thus

Pos. One Failsafe
Pos. Two Atttitude mode
Pos Three GPS.

I am pretty sure that your radio has somewhere the config in failsafe to bring the throttle down to zero which resulted in a motor switch off were the actual failsafe routine in the WK-M couldn't be executed any more. Maybe try the whole failsafe approach with you bird on the ground and props off. If you are sure it wont damage your motors and you have a quick hand to the lipos, bring the throttle up to minimum until the motors start and than test failsafe. The motors should start up to spin in a higher speed trying to reach failsafe hover position. With this you can at least test that the motors don't switch off again. I had a great experience from day one configuring having setup failsafe bringing down the bird and i don't know what was driving me switching of the radio, but this all indoors. The bird jumped 2 meters trying to reach its failsafe position and luckily after those 5 meters the Lipo ripped off

Concerning the weight how did you setup manage your power distribution ring or wire harness ? I was able to reduce my weight by redoing this and using this AFROesc distribution:

View attachment 1032
View attachment 1033
View attachment 1034

Concerning GPS i havent done any test yet except shielding cables to reduce interference so the GPS lock is acquired quicker.
You might be able to mount the GPS module onto one off the arms with some boom clamps, but this is really hard to answer and really up to your testing how certain position might increase SAT lock down or not.

What props are you using at the moment with your setup, the AXI 2814/22 were a good choice !

Tell your wife that your build is your one time on the side girlfriend and she better get to know it that she knows what she is up against in the next couple months, before you will start a new build thus add another one to your collection.

Boris

 

[david.scarbrow]

Boris, thankyou for your ' than useful' reply and comments. I'll try out you method of RTH switching but you have also reminded me that I need to wrap my head around Hitec failsafe mechanisms. I've actually got two of the Afroesc distribution boards on order from 3 weeks ago but they havn't arrived yet. I'm happy(ish) with the Flydution distribution board in terms of its size and weight but I truthfully don't know enough about its current handling capabilities...the very last view I want to see is my quad diving towards the ground because the power distribution board has burnt out due to the board's land patterns frying. I think I might just replace it with one of the Afroesc when they arrive. Perhaps an idea with the potential GPS interference might be to 'mask' the top of the airframe dome with electrical screening foil tape and see what happens as a staring point. I've seen 'something' somewhere on this very issue where a proprietary tape was used but I cannot remember where I saw/read about it. The props i am currently using are 13 x 6.5 AFC...they are reasonably cheaper and perhaps more useful for me at this time in my learning curve before I go on to more expensive props...eg...Xoar. This actually my second quad...my first being an original Xairforce 650 that I redesigned... reinforced booms, cut down legs, etc.. It may sound bad but I did learn a lot from it. I intend to design and build a pair of ali legs for the Bagheera this week-end so that I can at least stand the quad off the ground.

 

[RTRyder]

Your main problem is the failsafe setting of the Tx and RX. When you bind the RX it notes the positions of all control sticks and when it loses TX signal it will use those settings. If you did the bind with the throttle stick all the way down, thats what its going to use when you go into failsafe mode on the WKM. What you need to do is rebind the RX to the transmitter with the throttle set to halfway which on the WKM will be the hover position.

Don't worry about the strength of the GPS mast, I had mine fall roughly 15 feet when the motors shut down accidentally and the mast took a portion of the weight in the fall as evidenced by the dirt and grass stuck to it afterward. Nothing more than a slight bend in the shaft, easily straightened and back in place without even having to remove the GPS pod. You DO need to keep the GPS pod well clear of the IMU and control box the RFI from both will increase the GPS lock time to 10 minutes or more, putting the pod 20cm above the IMU reduced the lock time to about a minute for me.

You will find the correct 64 bit driver for Windows OS here...
http://www.rcgroups.com/forums/showpost.php?p=19367105&postcount=1902

Ken

 

[BorisS]

Ken I am a little confused about the throttle response when weight is added. I overloaded or lets say put on 2 additional lipos adding up to 5.5 KG. The copter didn't take of until being way over mid point with the throttle. Than bringing back the throttle resulted in the normal midstick one yellow blink attitude mode and staying to meter of the ground. If i interpret this the MC needs the calculate the throttle needed newly after every weight change on the copter. Just want to go sure that I understand it and that thats really the case and not some mechanical problem i am having is overseen.

At the same time since the firmware 3.2 the motorstartup speed varies everything hards starts slow soft starts etc. Have you experienced the same. I think is has something to do with the amount of gain on attitude mode.

Bois

 

[RTRyder]

Ken I am a little confused about the throttle response when weight is added. I overloaded or lets say put on 2 additional lipos adding up to 5.5 KG. The copter didn't take of until being way over mid point with the throttle. Than bringing back the throttle resulted in the normal midstick one yellow blink attitude mode and staying to meter of the ground. If i interpret this the MC needs the calculate the throttle needed newly after every weight change on the copter. Just want to go sure that I understand it and that thats really the case and not some mechanical problem i am having is overseen.

At the same time since the firmware 3.2 the motorstartup speed varies everything hards starts slow soft starts etc. Have you experienced the same. I think is has something to do with the amount of gain on attitude mode.

Bois

Yes there is something weird in the way the motors initally spin up fast then slow a bit then seem to settle down to a more normal speed with the 3.2 software, I don't think its directly related to the gain settings although it could be. It does appear that the IMU needs to start flying after changing the weight before it knows how to regulate the throttle properly, there's lot going on in the software and I doubt we'll ever really know much about it, definitely not open source!

 

[david.scarbrow]

Ken, thanks for that info...I'm gaining lots of answers and 'things' to try in response to my questions of this morning. Your response to the issue of failsafe setting within the Hitec radio now makes sense to me. I will definately attempt and reset this tonight when I get home. My WKM came with 3 seperate carbon masts of different lengths...I chose the medium length...what I think I will do now then is try out the longest mast and time the GPS lock response. My guess is though from what you have 'said' is that your mast(s) are of metal construction and allow for it to be bent a little...my carbon masts won't allow for that and as they are effectively glued in position I fear that on impact with something the resultant damage might be more than a bent mast. Many thanks for the link to the 64 bit driver.

Borris, I still can't wrap my head around how the quad will detect different weights and the need calculate 'somehow' the new throttle settings to compensate for the weight change...I think I am being vague in my thinking here.

 

[Flying Tivo]

Yes there is something weird in the way the motors initally spin up fast then slow a bit then seem to settle down to a more normal speed with the 3.2 software,

Its not weird, remember that if you are in Att/Gps mode, the stick position is not Throttle. Remember that stick position is Ascend/Hover/Descend, and the more deflection of the stick the higher the rate it Asc/Desc. Now if you are in Manual mode, then it is just pure throttle and it will take off at the position depending on the weight of your craft.

Felipe

 

[BorisS]

I agree but why is the initial throttle responds from one lipo to the other most of the time different. For me personal i take a look at all different behavior at every flight that something could be wrong. Different throttle responds is just another variable i dont need if nothing on the setup really changed. I think they dont store the info and take an average value for startup with every new lipo, linked to some variables that i am not aware of at the moment.

 

[RTRyder]

Its not weird, remember that if you are in Att/Gps mode, the stick position is not Throttle. Remember that stick position is Ascend/Hover/Descend, and the more deflection of the stick the higher the rate it Asc/Desc. Now if you are in Manual mode, then it is just pure throttle and it will take off at the position depending on the weight of your craft.

Felipe

Understood but that goes against what I'm seeing. In the mode you describe when the throttle stick is at its lowest point the motors should be spinning slower than at mid stick because that is where it would be to descend quickly and therefore the motors necessarily needed to be spinning much slower than they would to hold a hover. What I see happening is as soon as the throttle starts to move away from bottom the motors spin up to some percentage of rpm for a short amount of stick travel and then slow down to a very noticeable lower speed and then come back up to where you would expect as the stick nears center and the hex begins to lift off. It did not exhibit that behavior with the previous software version and is something I noticed immediately on the first flight with the 3.2 version of code, happens every time. Other than that it all works normally as it did before.

Ken

 

[BorisS]

since i don't like that behavior, also out of security reasons i will post it in the RCgroups forum. Ken i might take some wording from you, english is always troublesome for me ! if thats okay