Monday, October 27, 2008

[UAV] Draganflyer X6

My friend sent me a link today, and it is the Draganfly UAV. There are two types of UAV they have, and the helicopter one (X6) is really amazing. After viewing some of its videos, I can only say ``Wow...''

The X6 has different configuration from the R/C type which has four arms and blades. The three sets of counter-rotating blades of X6 should improve its aerodynamic performance, and also saves the energy from wasting on anti-torque.

Here are some videos of Draganflyer X6. Hope you enjoy with it.

Sunday, May 18, 2008

[UAV] 080515 Flight Test

Okay, we had some successful tests that day.

Before the test, I asked CH and Shawn to exchange the OEM4 and OEM5 which were installed on SWAN and H-LING, respectively. Therefore, at the beginning of the test, SWAN was equipped with OEM5, and something wrong during the flight. We found the onboard PA gave abnormal information, and of course SWAN couldn't perform normal heading tracking flight. At first, we thought the problem was due to the complementary filter which had not been tested onboard before. However, after turning off the complementary part, the PA still exhibited strange results. Then, we put the OEM4 back instead of the OEM5, everthing was okay! Therefore, we concluded that something not right with the OEM5.

With the complementary PA, SWAN had performed several not bad heading tracking and turning. It has been about two years since the previously autonomous flight of SWAN. The successful flight test made SWAN ``reborn.'' At least I feel so. :-)

Another good result is the PA of H-LING calculated onboard. The PA calculated in realtime matched the one by post-processing. So, it's the time to test the PA in the hovering control.

God bless H-LING.

Friday, May 16, 2008

[UAV] 080513 Flight Test

Because Shawn has to realize the heading tracking of SWAN, and I also want to apply my method of attitude determination for the model-scaled helicopter, we decided to have another flight test.

On that day, only H-LING was tested. And the number of the testing group was the least one: only 3 people.

CH, Shawn, and me, we went to Saikang with the H-LING system in one car. That's really a simple team. I was the pilot, CH took the video, and Shawn was in charge of the GCS.

The PA of the H-LING seemed not good according to the report by Shawn in real time. After the flight test, I ran the code to check the PA and found they were totally unacceptable... We didn't know why then, but later, with another flight test, we have known that's due to the GPS receiver.

Monday, May 12, 2008

[UAV] 080509 Flight Test

Yes, we conducted 3 flight tests in a single week! My God, it really made us exhausted.

Some good results, however, was obtained.

We tested SWAN and H-LING that day. The attitude determination methodology of SWAN had been modified. When the pilot switched SWAN to auto-mode, I felt some tension as SWAN rolled too one side. But it turned back!

SWAN did ugly but stable autonomous ``straight'' flight. It ``meandered'' across the sky along the desired heading. Some modification of the attitude determination method seems necessary, and we have decide to accomplish it before the next flight test.

We found a problem of H-LING's fuzzy logic controller. The attitudinal inputs didn't fired the corresponding rules. This might be the cause of the poor resistance of H-LING to the side wind. H-LING cannot restore its own attitudes after deviating from the trim condition, and the unfired rules might be the reason.

[UAV] 080508 Flight Test

The test was not so successful. Only SP-X.6 did some tests for gathering data for system ID.

SWAN didn't show attitudes' information on the GCS (ground control station) and hence only flew to record some flight data. Unfortunately, these data showed no useful information. Some programming bugs caused the failure.

That day was not H-LING's day either. After the test of SWAN, the Xsens AHRS suddenly had no output. H-LING has shared the same AHRS with SWAN, because the other one was sent to Holland for repairing and has not been sent back yet. Therefore, we ended the test of H-LING even didn't start the engine.

Sunday, May 11, 2008

[UAV] 080505 Flight Test

Only SWAN had flown for test that day. The AHRS was still not usable under the vibration. The attitudes, especially the roll angle, were not reasonable. Therefore, SWAN didn't perform expected autonomous flight.

The weather became worse after SWAN's flight test. It rained, and we decided to terminate the tests before our gears got into the rain. We had too much stuff to load them back to the car in time. Fortunately, our pilot's car offered a good shelter for our aircraft. He even drove these things back to our lab. Thanks for his great help!

Okay, only one thing was worthy for me to record, that is, the inverted hovering of the RC helicopter which is shown in the photo. However, I found only 20% performance of what I have in the simulator can be realized in actual RC flight... Orz

Wednesday, May 07, 2008

[UAV] 080501 Flight Test

The flight tests were completed without too severe problem. Only the SP-X.6 had a hard landing due to the pilot's concern. Because the runway end located high bush, it has been a obstacle threatening the pilot as landing. The pilot wanted to slow down the aircraft while avoiding the bush in the same time, then the SP-X.6 went into stall just before flare. Fortunately, only the nose gear was bended and no more damage else.

SWAN did some fuzzy control to track given heading. Some results were good and some were unacceptable. After checking the onboard program, we found the cause. The definitions of the heading were not consistent. One was defined from 0 to 360 and another was from -180 to +180. Therefore, when the heading was given westward, then the SWAN went the wrong response.

H-LING also tested with the FLC and some results were not bad. The helicopter held itself in hovering for several seconds, and the longest one was about 12 or 13 seconds. However, we found the recorded data showed some unexpected results. The FLC controlled the helicopter toward the desired attitude and then drifted away sometimes. The reason has not been figured out yet.

More photos can be seen HERE.

Friday, May 02, 2008

[UAV] 080425 Flight Test

As usual, we had three groups for flight test. Actually, we are ``a'' group with three UAV systems for testing.

The SWAN UAV is the oldest system in use of our lab. It's a fixed-wing UAV made by fiberglass. It had completed beyond-the-vision cross sea flight in 2005. Here is a video about the SWAN.

The second fixed-wing UAV is the SPOONBILL, which has been designed by Chi-seng for longer range autonomous flight. The goal is to fly from Tai-lam (Tainan) to Phenn-ou (Penghu). We all hope this project can be successful. Many tests have been done with a 60% scaled prototype, the SP-X.6. It was also flew on that day. The yellow one in the photo is the SP-X.6.

H-LING is the third system which is an unmanned helicopter project launched in 2006. Since about 2007, I have been the test pilot of H-LING. This project is still under the phase of hovering control test. We have worked hard to try to realize the autonomous hovering, but it's really not an easy task. However, the relevant studies about the H-LING is interesting. At lease, it is true for me. :-)

On that day, unfortunately, we crashed the vehicle of H-LING. Something abnormal happened when the vehicle was flying in automatic rolling control. A sudden pitching down occurred when the pitching cyclic input is still under my control. I ignored the abnormal motion and kept to test the rolling control. Finally, the vehicle lost the control suddenly. I turned off the automatic control but still cannot save the vehicle. It was just totally out of control and crashed down. We all have no idea about the causes. Of course, this was not the first time we crashed vehicles in flight tests... :-p

The autonumous hovering in that day was not successful. Still lots of works to do.

[Heli] Inverted Flight: Very Slow Progress

My first inverted flight of the RC heli was done with T-rex 450 SE before more than 1 year ago. Now, I can invert the heli steadily in hovering at altitude lower than a man's height. Of course, I am still practicing for inverted flight in different orientations.

It's really very slow for my progress in the RC helis' flight. Perhaps that is because that I have no talent and no time as well as money to have enough practices. But it's okay, I have had lots of fun in learning to control the RC helis! :-)

Moreover, this hobby makes me able to help our lab to conduct the unmanned helicopter's flight test. In these 2 years, I have flown almost all the helis in flight tests of our lab. I am very glad to contribute to the team work.

Keep flying.

Tuesday, January 22, 2008

Data is/are?

When I am writing my dissertation, I have been bothered by the usage of ``data is'' and ``data are.'' After searching via Google, I have found some information and some of them give some interesting opinions.