Wednesday, 13 December 2017

Bridge Surveys in Wicklow

Siyuan Chen
Time: 2017
Location: County Wicklow


In this summer, Linh and I have conducted several times of survey in the county Wicklow for bridge data collection. If ignore the windy weather, the experience was great. This area is surrounded by beautiful lakes and green mountains. Sheep are fitting in every piece of land. To be honest, I am sure that those sheep should be the happiest sheep in the world, if they could have a longer summer. : P

























































There are 3 candidate bridges in this area. After the site pre-check, the bridge A has been selected as the inspection target. Both the laser scanning and photogrammetry inspection have been conducted in the following days. 

 

 


 




Contact
Siyuan Chen 
School of Civil, Structural and Environmental Engineering
University College Dublin, Ireland

Email:  siyuan.chen@ucd.ie

Tuesday, 12 December 2017

Lab experiment - 3D reconstruction of a masonry wall

Siyuan Chen
Time: 2017
Location: Dublin


As we know, photogrammetry methods like structure from motion (SFM) has the potential to generate 3D models or point cloud from 2D imagery data. Combined with UAVs, this method can provide a significant help for civil engineers in rapid modeling. The usage scenario could be urban modeling, post-disaster survey and construction site inspection. To have a better understanding of the limitation of the method and related influence factors, a lab-based experiment has been conducted in UCD.

With the help from my colleagues Iman and Atteyeh, four masonry walls have been built in the lab. Both the Laser scanner and the digital camera have been applied for data collection. An adjustable tripod has used to control the camera angle and distance to the wall. The reconstruction process has been completed by the open source software VisualSFM. After a comparison, we figure out that the result is highly related to the images angles. The data completeness, density distribution and geometry accuracy are all related to the angle selection. More details have presented in the conference paper ‘The effect of angles and distance on image-based, three-dimensional reconstructions’- DOI10.1201/9781315210469-350. The final suggestion is that, in UAV inspection, it is much better to put the camara axis vertical to the target surface. And using muitipal flight path can improving the data completeness.











































Contact
Siyuan Chen 
School of Civil, Structural and Environmental Engineering
University College Dublin, Ireland

Email:  siyuan.chen@ucd.ie








Thursday, 15 June 2017

Fly the drone above water - Floating base design for UAVs

Fly the drone above water - Floating base design for UAVs

Date: May 30, 2017
Location: Dublin


Using drones for photography and inspection have become more and more popular. In some situation,  such as recording the water sports or doing under bridge inspection, we have to fly the drone close to the water surface. It looks like an easy job,  but it is really a challenging for drone operators. The done should always keep a safe distance to the water surface, but the cross wind and waves will prevent the operator to do so. Even advanced drones are equipped with high-tech sensors, such as ultrasonic sensor, visual detector, barometer for altitude holding, they are not working well in an environment filled with random reflection and inconstant air flows.



Figure 1. Flying above the water

Figure 2. Floating base for UAVs


In our research, for under bridge inspection, we designed a cheap floating base to avoid water damage, shown in Figure 1 and Figure 2. The float base only includes a frame and four bottles and appropriate for different drones. In the field survey, it works well. If you are interested in it and want to make one for your ‘baby’, here are some tips:

1. Frame

The frame is used for connecting the drone and fixing bottles caps. You can use any light and solid materials (acrylic or aluminum) or any manufacturing method (machining or 3D printing), but remember to leave am empty areas below the camera and other sensors. In addition, make the angle between two front bottles bigger can further ensure the camera is unblocked. 


Figure 3. Frame design

2. Bottles

Theoretically, a 1L bottle can support 1kg's weight. Thus for a DJI Phantom 4 (about 2kg), 4x500ml bottles will be enough. But considering the momentum when the drone falls off and the possible deformation of plastic bottles, we used 4 1L bottles in our case.

Instead of installing the bottles vertical or horizontal,  we using a 30-degree angle to avoid the flip-over problem (vertical setting will have). It solved the inefficient aerodynamic problem and lower floating center problem (horizontal setting will have) as well.  If you are lucky to find some narrow neck bottles, the aerodynamic performance could be further improved.




Images of the test and field survey


Flight time and wind resistance test (20 min)



Weight and balance test (2.5 kg)



































Under bridge survey
































Contact
Siyuan Chen 
School of Civil, Structural and Environmental Engineering
University College Dublin, Ireland






Thursday, 20 October 2016

Drone Workshop in UCD

Drone Workshop in UCD

Date: September 29th, 2016
Location: Newstead, UCD


Unmanned aerial vehicles (UAVs) or Drones developed rapidly recently and drawn attentions from mass public. To help students get a close contact with drone technologies, last month in UCD, Dr Eleni Mangina arranged a workshop for graduate students. PhD student Even O'Keeffe and I made presentations during the workshop. Almost 20 students attended.

In the beginning, Dr Eleni Mangina introduced the history and current applications of UAVs.



After that, Even O'Keeffe explained the legal requirement for UAVs application in Ireland. He also shared his experience in drone-related software developing.



Then, I showed them the steps of building a DIY drone. Introduction to each component and tips for model selection also included.


In the last, students get a chance to have a close look at different drones and ask questions.




Contact

Siyuan Chen
School of Civil, Structural and Environmental Engineering
University College Dublin, Ireland
siyuan.chen@ucd.ie


Thursday, 28 July 2016

Boyne Viaduct Bridge Aerial Survey


Boyne Viaduct Bridge Aerial Survey



Date: July 6th, 2016
Location: Boyne Viaduct Bridge
Completed by: Jonathan Byrne, Siyuan Chen

Background

Boyne Viaduct Bridge is located in Drogheda, about 50 km north of Dublin city center. The viaduct is 30 meters high, comprises twelve stone arches on the south side, and a further three arches on the north. It was designed by the Irish civil engineer Sir John Benjamin Macneill, constructed in 1855, and refurbished in 2015.
Google Map

In the early morning, Jonathan and I inspected the south side with two flights.








Aerial Images


                   

3D Reconstruction

3D reconstruction process was based on 287 aerial images and 321 ground images. Python Based platform VisualSFM[1], Commercial platform PhotoScanPro[2],  and open source platform Meshlab[3].













Aerial Video

In the last, let us enjoy a short aerial video.




                             




Contact

Siyuan Chen
School of Civil, Structural and Environmental Engineering
University College Dublin, Ireland
siyuan.chen@ucd.ie




[1] VisualSFM was created by Changchang Wu at the University of Washington Seattle.

[2] PhotoScanPro, developed by Agisoft, is a stand-alone software product that performs photogrammetric processing of digital images and generates 3D spatial data.

[3] MeshLab is an open source, portable, and extensible system for the processing and editing of unstructured 3D triangular meshes.

Tuesday, 26 July 2016

New Drone Test


New Drone Test


In last month, I started to build a new DIY drone. Some details will be attached below.

Drone Building

This drone we using an old Tarot 650 carbon fiber frame, 4 x kv800 rotors,4 x 12-inch propellers (4 x 15-inch propellers), 4 x 30-A ESCs, Pixhawk flight controller with 3DR GPS module, Turnigy 9xr pro radio controller with FrySKY XJT module, X8R SBUS receiver, and 3DR telemeter.





Drone Setting

APM Planner was used fro flight controller setting. RC was programmed by eepskye. 


After basic setting and sensors calibration, I went out for several times flight test. Here I can write a book named 'Drone accidents'. The first time, before took off, one propeller was loose and shoot off. The second time, it spinning on the ground and flipped over. The third time, it can take off, but direct crashed on a tree (One leg was gone). The fourth time crashed on a wall (Another leg was gone). The fifth time.....  (Sorry, too many times, it is hard to recall all of them.)

Every accident made the drone settings improved a little but made the physical structure damaged a lot. I do not want it to be totally destroyed before the successfully take off. So, after several days' hard repairing, I designed a few indoor test methods. 
                   

Indoor Test

Four pipes were mounted on each arm to keep a safe distance for propellers. Steel core cord went through those pipes to restrict drone’s movement. In the video, you can see the drone flight just like an angry wasp. It was lucky I bought strong enough cords.







PID Tuning

To adjust the PID parameters for flight control. Two tables were used to fix the vertical movement of the drone. After several times test, with the help from Even, the PID curves are looks much better.


                                 


Outdoor Test

After got a satisfied setting, we did an outdoor test. Finally, it successfully took off and followed with a safe landing.   : D



Contact

Siyuan Chen
School of Civil, Structural and Environmental Engineering
University College Dublin, Ireland
siyuan.chen@ucd.ie