UAV TECHNICAL REPORT. By BrisbaneUAV.

Transcription

1 UAV TECHNICAL REPORT By BrisbaneUAV

2 Contents Licensing... 1 Sponsors... 1 Executive Summary... 2 Introduction... 2 Design and Rationale... 3 Quadcopter Frame... 3 Hardware Selection... 3 Software Selection... 4 The following points have been discussed to meet the specific rules and criteria. Each numbered point is a reference to that section in the challenge rules Aircraft Requirements Unmanned System Requirements Operational Requirements... 5 Risk Management... 6 Safety Kit... 7 Flight Test Results and Discussion... 8 Conclusions... 9 Licensing Everything in this technical report (unless otherwise referenced) is released under the Creative Commons Attribution-ShareAlike 4.0 International License. It may be used for any purpose as long as you provide attribution to BrisbaneUAV and release any modifications under the same license. This document, and many other resources may be found on our website at brisbaneuav.com.au. Quick Note: While there is nothing stopping you from submitting this as the technical report for your team in the UAV challenge, the rules forbid it so it s likely it would not be accepted. Sponsors BrisbaneUAV has received major financial support from the following sponsors: Drone Boys Ubiquiti Networks (donated WiFi radio gear) Cate Bolt (from Foundation 18) Julie Fish (from Little Jewels Décor)

3 Executive Summary Outback Joe needs urgent medical treatment for is anaphylaxis but the nearest help is too far away. An autonomous UAV is needed to help deliver an Epipen that is paramount to his survival. BrisbaneUAV have developed an autonomous system that can automatically locate Joe and deliver the needed package. We have done this by devising a UAV system full of the latest technology and safety features like GEO fences and high bandwidth data links capable of streaming HD video straight from the aircraft. There is a tiny computer powerful enough to do on board image processing adding reliability and safety to the system. All these features, hardware and software has been put together to form a safe, reliable system and has been extensively tested. The system works well, albeit with some drawbacks, which are constantly being improved upon. BrisbaneUAV s autonomous system can meet the task quickly, effectively and safely. Introduction The High School UAV Outback Challenge is an exciting event run every year with the purpose of demonstrating the usefulness of UAVs (Unmanned Airborne Vehicles) for civilian applications like search and rescue. This year, the challenge is to deliver an Epipen as close as possible to outback Joe using a fully autonomous system. This differs from previous years as the system must be completely autonomous (operate by itself) and require minimal user input. The system must automatically find Outback Joe and deliver the Epipen to him. This is so he can treat his anaphylaxis immediately while he waits for professional medical aid to reach him at his remote location. This report will detail the design and rationale, risk management and discuss the results of flight tests. The project was approached from a safety and reliability point of view. Most design decisions were made in favour of higher reliability or safety in the system. Each section will be focused on detailing the safety aspects of the system. Overall, this report will give the UAV Challenge Technical Committee a detailed source of information regarding the system that they can use to determine if it meets the safety and operational requirements of the 2015 challenge. The overall aim of this project is to create an autonomous UAV system that can effectively locate Outback Joe and deliver a vital Epipen as close as possible. The main criteria that affects the success of this project is the accuracy and reliability of the system and the overall safety. The system needs to be safe, reliable and accurate when performing the delivery. Where there is a number in the title, it is specifically referring to that section in the rules. The design and rationale has been detailed over the next few pages.

4 Design and Rationale Quadcopter Frame A commercial quadcopter frame was originally bought but its quality was not of an acceptable standard so a custom one was made to save time and money. A custom built aircraft has been designed and constructed to suit the requirements of the challenge. A H style quad copter was selected, the completed design can be seen in Figure 1. The design uses standard 42x11mm pine timber with 7mm plywood secured on top for extra strength and somewhere to mount the gear. The quadcopter uses PVA wood glue and small nails to ensure it is strongly assembled. The use of nails in its construction was carefully considered as they are a potential hazard. It was thought that in the unlikely event of the frame separating mid-flight, causing nails to become exposed, they would likely do no more damage than broken/sharp plastic or carbon fibre from a commercial design. Figure 1: The construction and layout of the quadcopter. Custom designed 3D printer motor mounts have been used to allow easy reconfiguration or replacement. Two 3/16 or M5 (countersunk) bolts are required to attach the motor mounts to each arm of the frame. The use of 3D printed motor mounts is another potential risk which has been minimised by designing the mounts to be extremely strong and doing a lot of testing to ensure they are safe. All high current cabling has also been moved as far away as possible from the sensitive autopilot (pixhawk) and compass to minimise the risk of interference. Hardware Selection Each piece of hardware was specifically chosen to ensure reliability and safety during the development/testing phases and during the challenge. Each piece of hardware is readily available off the shelf (apart from the frame and custom made cables/adapters), with specific software developed or configured to suit the requirement. The following table outlines each major piece of hardware and what purpose it servers. Hardware Pixhawk Flight Controller Raspberry Pi 2 Ubiquiti Rocket M5/Nanobeam M5 FrSky X6R FrSky Taranis X9D Plus Ublox Neo 8 GPS/compass Lenovo X230 Tablet PC Antenna Tracker Telemetry Radio Monitor Portable 12v battery Purpose The pixhawk flight controller was specifically chosen due to its open source software that is easy to interface with from a companion computer. It s also one of the most reliable and well known flight controllers in the world. A powerful single board computer was needed to do image analysis, soft geofencing and stream HD video from the aircraft. These tasks are fairly resource intensive so a powerful and easy to access board was selected. This is the main wireless link to the aircraft and has a lot bandwidth, it can stream telemetry, HD video and can control the companion computer. The FrSky X6R is one of the most reliable and cost effective receivers compatible with a FrSky Taranis. It has settable failsafe values and an extended range when compared to other receivers. This is arguably the best open source remote controller and has a tremendous amount of features. It has also proven to be extremely reliable. The Ublox Neo 8 GPS is one of the most accurate and reliable GPS s units available today. This creates a more accurate geofence and increases its effectiveness. The Lenovo X230 tablet pc is an extremely reliable, business grade laptop. It s built in touch screen enables easy interaction and the operating system is Ubuntu for its reliability. It will run Mission Planner, MAVProxy, BrisbaneUAV s custom interface with the raspberry pi and stream HD video from the aircraft. A custom built, mostly 3D printed antenna tracker will take telemetry data and position the directional Nanobeam M5 radio towards the aircraft. A standard 915MHz telemetry radio (ie wireless serial bridge) will be used as a redundant connection in case the WiFi link is lost. A second monitor that runs off 12v is required to display some of the software. A portable 12v battery is needed to power the GCS. 12v was chosen to dues it relatively safe voltage and its popularity. The monitor, Nanobeam, network switch, and router will need power. In case the laptop battery becomes flat, the laptop also has a 12v charger.

5 The following two diagrams outline how each component interacts and the power distribution of the aircraft. The power distribution is just a summary of the current layout. It is possible another BEC will be added to ensure more redundancy. Please note the sources of each graphic used as they are not necessarily CC licensed like this document. Figure 2 Detailed depiction of the system and how each component interacts. Figure 3 Power distribution of the aircraft Software Selection The companion computer will be running a variety of software. It will run MAVProxy with the BrisbaneUAV image recognition module. This is to recognise Joe and relay telemetry over the WiFi connection. It will also be running gstreamer in order to stream the HD video from the on board camera with low latency and high reliability. The latest stable (and tested) version of Arducopter will be loaded onto the pixhawk. The GCS laptop will be running Ubuntu for its reliability and ability to run all of the required programs easier than windows. The software it will be running is APM Planner or Mission Planner, MAVProxy and the BrisbaneUAV software to stream the HD video and control image recognition software.

6 The following points have been discussed to meet the specific rules and criteria. Each numbered point is a reference to that section in the challenge rules. 3.1 Aircraft Requirements The aircraft will meet the requirements by; using an electric propulsion system, being capable of vertical take off and landing, having a pixhawk autopilot, being untethered and free flying, weighing less than 7KG, will have continuous communication with the UAV controller (and redundant links to the mission manager/gcs operator) and will contain both off shelf and custom made systems on board Geofence Due to lack of support for a square Geofence in the current Arducopter code, a module has been written that runs on the raspberry pi companion computer. The purpose of this to continually check the current GPS coordinates of the aircraft. If it starts nearing the edge of any boundaries a Soft geofence will automatically land the aircraft to prevent damage. If the aircraft cannot safely land before reaching the hard geofence then it will perform flight termination as required by section Flight Termination Behaviour A FrSky X6R receiver is being used on the aircraft, it has the ability to revert to predetermined values when radio communications are lost. The receiver has been programmed to activate manual control and close the throttle. Because it is being set by the receiver, the autopilot may not override flight termination Criteria for Flight Termination The autopilot will automatically activate flight termination if loss of the radio link from the UAV Controllers remote occurs. The companion computer is also used as a backup, if for some reason the autopilot doesn t trigger flight termination. If the aircraft is getting to close to the hard geofence the soft geofence will trigger and try to land the aircraft, if at any stage the aircraft crosses the hard geofence it will immediately activate flight termination. If GPS is lost for at least 5 seconds, the aircraft will immediately land if it s in an auto mode. By switching off the transmitter, the UAV Controller can manually trigger flight termination at any time or on request by the judges/safety personnel. The UAV Controller has been instructed to activate flight termination immediately, and without delay or argument if instructed to do so by the GCS operator, judges or range safety coordinator. 3.2 Unmanned System Requirements UAV Controller Override A switch on the remote control has been assigned as a manual override allowing the UAV Controller to switch into a manual operating mode at their discretion or upon request by the judges Situational Awareness The GCS software MAVProxy is being used in conjunction with Mission Planner. Using MAVProxy allows the ground station to have two redundant, telemetry data links to the aircraft and automatically switch to the best one. The two data links consist of the main, telemetry over IP which will be routed through the on-board WiFi access point. The second, redundant link is a standard 915MHz telemetry transceiver commonly used by UAV systems Radio Equipment All transmitters being used for the UAV system fall under the ACMA LIPD (Low Interference Potential Device) class license allowing their use. In total, there are 3 transmitters being used in the UAV. There is a link between a ubiquiti rocket M5 and Nanobeam M5 operating on 5.8GHz using the standard n protocol, a FrSky Taranis and FrSky X6R Rx using 2.4GHz and FrSky ACCST protocol and two 915MHz telemetry radios. 3.3 Operational Requirements Take-off and landing The aircraft will try to take off and land autonomously. If for any reason the GCS Operator or the UAV controller feel uncomfortable with the autonomous take-off or landing, the UAV controller will manually take control. The flight inside the search grid will be fully autonomous, the autopilot will be running a predetermined course.

7 Risk Management There are many risks involved with experimental development of UAVs. There are so many things that can go wrong and potentially become injure someone or damage property. BrisbaneUAV s main focus while developing the UAV system has been on increasing the systems reliability and safety. A detailed risk analysis of the system and ways that BrisbaneUAV have minimised this risk has been included below. Before an analysis can begin, appropriate definitions must be made. According to the ACT s Worksafe government department the following definitions apply: A hazard is an act or condition that has the potential to cause damage to plant or equipment, or result in an illness or injury. Hazards can be categorised by the type of outcome, energy exchange process or geographic location - e.g. manual handling hazards, slips and trips, laundry hazards. A risk is the likelihood of a specific consequence occurring. Risks are usually expressed in terms of likelihood and consequences - e.g. the risk of contracting Ross River Fever while working in Tasmania might be considered to be very low. According to the same government department, there are three main stages in Risk Management. They are risk identification, risk assessment and risk control. BrisbaneUAV have used the hierarchy of control to minimise any potential risks. In order of most to least effective, the ways of controlling a risk are Elimination, Substitution, Isolation, Engineering Controls, Administrative Controls and Personal Protective Equipment (PPE). Due to the large number of risks, only the risks considered Major are listed as there is not enough space. The risks have been listed in a table with an analysis performed on each and the suggested management approach. The rating of the severity of the risk was done using the Risk Matrix in figure 4 below. Risk Likelihood Consequences Rating Management Injury from props Possible Catastrophic High The most effective control measure is administration controls. Everyone operating on or around the aircraft must be aware of prop safety and never have hands near the props when power is connected. Whenever operating on the aircraft props should be removed or power should be disconnected. Basic administration tasks like these can greatly minimise the chance of this particular risk becoming an issue. Injury from falling quad Damage from LiPo batteries Electrical Shocks Possible Catastrophic High The most effective control measure for this risk is isolation. Whoever is not directly needed to control the aircraft should be nowhere near it when in flight. The CASA 30m rule which applies to UAVs and hobbyist planes has deemed to be an appropriate distance away from the aircraft while in operation to be safe. Unlikely Major Moderate Isolation and administration are the most effective control measures for LiPo batteries. LiPo batteries can catch fire or explode if mistreated so everyone who needs to handle them must have a good knowledge of how to be safe. They should never be under/over charged, exposed to extreme heat/cold or be punctured, bent or stressed. Unlikely Moderate Moderate Electrical shocks from batteries and power supplies must be managed. The most effective measures of control are isolation and engineering controls. All electrical connections that do not need to be changed often should be completely sealed in appropriate tape or heat shrink. Ensuring good soldering connections and good quality connectors can also help minimise this risk.

8 Trip Hazards Sleep Deprivation Possible Major Moderate Engineering and administrative controls are the most effective for this risk. All cabling for the GCS should be neat and mats placed on top when running along floor. The BrisbaneUAV safety kit will contain towels and duct tape to ensure all cabling and other hardware is secure, neatly hidden and doesn t become a trip hazard. Likely Moderate Moderate Due to the nature of the competition it is likely some team members will be lacking of sleep leading up the competition. Being severely sleep deprived can have as much of an effect on the brain as being drunk. Therefore all team members must have a good night s rest for the two nights leading up to and during the challenge. This administration technique has been deemed the most effective. Risk Rating Matrix Likelihood Consequences Rare Unlikely Possible Likely Almost certain Catastrophic moderate moderate high critical critical Major low moderate moderate high critical Moderate low moderate moderate moderate high Minor Very low low moderate moderate moderate Insignificant Very low Very low low low moderate Figure 4 Risk rating matrix ( Safety Kit BrisbaneUAV will also put together a safety kit and keep it close at all times. The safety kit contains essential items required to react to various situations that could cause injury or property damage. The safety kit contains the following items: First Aid Kit Fire Extinguisher (Date checked every time flights are done to ensure it s still useful) Basic tools like o Gloves o Pliers o Heavy Duty Scissors o Sidecutters o Duct Tape o Zip ties Towel for covering cables Details of closet emergency services and contact numbers (will need to be updated when flying somewhere new and before arrival at the challenge) Checklist to ensure everything is present By having the safety kit, implementing risk management strategies and designing smart hardware/software BrisbaneUAV has minimised the potential risk for the UAV system. This ensure the safety of all team members and spectators who may be present when operating the UAV system.

9 Flight Test Results and Discussion The UAV system meets all the requirements set out in the rules and follows everything written in this technical report. It has an active geofence, flight termination criteria monitoring, a manual override switch, a graphical display of the status of all systems including waypoints and current location and it also complies with all laws and regulations required by Australian law. The aircraft flies very well and handles wind satisfactorily. After a few rather hard landings everything was still strong with no movement or damage to the airframe or electronics. The handling characteristics are OK but are a little bit sluggish compared to other aircraft which is OK as it results in a more stable platform. The large area of the frame can house all the required equipment quite comfortably with enough space for wiring and batteries. The motor mounts were also tested and could be easily replaced in as little as a few minutes with a spare one. The quadcopter gets the required flight time of at least 10 minutes, in fact it lasts significantly longer at closer to 15 minutes of flight time at full payload. All of the individual components work well together but have not been compiled into a single program yet. This gives BrisbaneUAV the confidence everything will work one it has been properly fit together. Currently, the HD streaming, image recognition, antenna tracking, WiFi connection, telemetry connection and all other aspects of the system work well, albeit not entirely together as of yet. In the next few weeks the software will be consolidated into a simple MAVProxy module making it more reliable, efficient and safe. The image recognition software was based on OpenCV. Whilst it is not very accurate at this current time, it was still able to detect Joe autonomously but had trouble accurately dropping the package. During the next few weeks, the second improvement will be to increase the accuracy and reliability of the image recognition software so that the package is dropped on the target, every time. This just requires some fine tuning and minor code adjustment so isn t a large task. The antenna tracker has performed excellently and has never failed during testing. Once during transport, the antenna tracker was dropped and part of it that was intentionally designed to break to limit damage successfully broke. This resulted in no other damage being done to the expensive Ubiquiti Nanobeam on top or the other parts and servos. The antenna tracker reliably and accurately tracked the quadcopter at distances similar to what it will be operating at during the challenge. Whilst the performance during ground tests only a few metres away suffered, this is OK as it will never be used that close during actual use. This is because the GPS is not accurate enough at such close range to continue tracking accurately. The remote control (FrSky Taranis X9D Plus) and receiver (FrSky X6R) has been an excellent combination and has never glitched, dropped out or otherwise had any problems. It has been the most reliable radio and receiver combination used by BrisbaneUAV and will be used during the challenge. The GCS setup is still a little cluttered, clunky and inefficient to set-up and take down but that is also being improved. Custom mounts for everything are being designed so they can easily attach to a tripod or table allowing even quicker set-up and pack-up times. So far the GCS set-up in general has been satisfactory, but will be significantly improved before the start of the challenge. The dropping system had to be modified after the technical committee decided lowering the package was not an acceptable solution. The new solution was to implement two shock absorbers that slipped onto either end of the package. This allowed the package to be suspended in a net of rubber bands which significantly reduced the force it experienced under impact. According to calculations, it should impact with a force much less than 75Gs. To confirm this theory, a high G rating accelerometer has been ordered so the exact impact can be measured accurately (within about 6Gs) to determine if it meets that requirement. If it is found in actual use that the impact is still close to or above 75Gs, a small parachute will be added to slow the descent rate, whilst minimising the drift over the ground it may cause.

10 Conclusions The UAV challenge requires a vertical take-off and landing capable aircraft to autonomously deliver a package to Joe by following a serious of symbols and locating an X. This package is an important Epipen vital to treat Outback Joes Anaphylaxis. BrisbaneUAV has developed an autonomous UAV system that is capable of meeting the difficult requirements of the challenge while still remaining safe and reliable. This report detailed the design and rationale, risk management and evaluated the results of the flight tests. The entire project was initially approached from a safety reliability point of view to ensure the safety of all team members, challenge personnel and spectators watching the challenge. Most design decisions were made in favour of safety or reliability over features. This report has given the UAV Challenge Technical Committee a detailed source of information regarding BrisbaneUAV s system that will help them determine if it meets the safety and operational requirements of the 2015 challenge. The project has created an autonomous UAV system that can quickly and safely located Outback Joe and deliver his vital Epipen as quickly as possible while he waits for medical attention. The main criteria that affected the success of this system is its overall safety and reliability. The system is safe, reliable and mostly accurate when autonomously locating outback Joe and delivering his life save Epipen.

11 All team member declare that all work has been done by us and all other sources have been appropriately referenced. Signed by all Team Members: Jaimyn Mayer Tiernan Martin