1. Presented by Robert Clark Instrument Technician
Cardington UAS
Presented by
Robert Clark
Instrument Technician
Good afternoon everyone. I am Robert Clark and I’m going to talk to you today about the Cardington UAS. We acquired the UAS early on this year and I think we’ve progressed well since then, getting to grips with the new technology. For us it has been an extremely interesting year, despite the weather being unfavourable for long periods during the Summer.

2. UAS stands for Unmanned Aircraft System
What is a UAS?
UAS stands for Unmanned Aircraft System
The term UAS generally refers to the entire operating equipment, including aircraft, ground control station and wireless data link
UAS technology increasingly of interest in many civil applications, such as surveillance, aerial photography, security and meteorology
UAS technology offers us exciting new potential for atmospheric studies, including temperature & humidity profiles, wind speeds and direction, boundary layer height & turbulence, fog, cloud & aerosol spectra, etc
I guess I should start by explaining what a UAS is, given the subject has already been raised in the notes for our conference this week..... So, UAS stands for Unmanned Aircraft System. It seems to have taken over from ‘UAV’ (Unmanned/Uninhabited air/aerial vehicle), giving more prominence to the word ‘Aircraft’. The term UAS generally refers to all the operating equipment making up the system, including the aircraft, ground control station and the wireless data link.
There has never been a better time for the Met Office to investigate the possibilities that a UAS can offer. The technology has developed to such an extent that it is increasingly of interest in many civil applications, such as surveillance, aerial photography, security and..... meteorology. For us, the technology offers exciting new potential for atmospheric research.

3. Cardington UAS Specifications:
Wingspan: 1.8 m
Length: 1.2 m
Weight (Empty): 1.5 kg
Payload: 1.5 kg
Max. Speed: 18 m/sec
Flight Duration: Up to 45 min
This is the Cardington UAS, awaiting take-off on its launch ramp. A few basic details are m wingspan and weighs 1.5 Kg when empty. Ours currently weighs 3.1 Kg, which is just over the manufacturers suggested limit. Maximum speed is around 18 m/sec and, with 2 batteries on board, can stay airborne for around 45 mins (although we have yet to confirm that...). What we can say is that it can climb to 5000 ft in under 7 mins, because we have done it....

4. Model: MAJA ( Manufactured by Bormatec)
Cardington UAS
Airframe Details:
Model: MAJA ( Manufactured by Bormatec)
Construction: EPP, Correx sheet
No. of channels: 4
Control Surfaces: Elevator, ailerons, rudder
Motor: Electric, with Electronic Speed Controller (ESC)
Power Source: Lithium Polymer (LiPo) batteries
This is the basic airframe. It is called the MAJA and is manufactured by Bormatec in Germany. It is made mainly out of a type of foam called EPP (Expanded PolyPropelene). This is a quite remarkable material in that it is light, rigid and incredibly robust. Even when it does break, a quick application of 5-minute epoxy produces a bond that is even stronger than the original material. The EPP is supplemented on the model with Correx sheeting, which is like a plasticised version of corrugated cardboard. This too is a very light and rigid material and is applied ingeniously on the airframe to provide extra strength and a novel interlocking system.
The model has 4-channel radio control, the control surfaces being elevator, rudder and ailerons. The electric motor employs a pusher propeller mounted at the rear of the aircraft. This leaves the front end of the fuselage entirely clear enabling, eg, a camera or sensors to be mounted without interference. The motor is powered by 2 Lithium Polymer batteries.

5. Cardington Modifications (1)
In order to adapt the basic airframe for our own purposes, we’ve had to make several modifications. The first was to make and install this bespoke sensor housing. It is made from glass fibre and holds 2 sensors: a fast PRT temperature sensor and a Vaisala HMP44 humidity sensor. As you can see, we have mounted the housing on the top surface of the fuselage, to minimise the likelihood of it taking a knock on landing.
Sensor housing:
Temperature sensor (fast PRT)
Humidity sensor (Vaisala HMP44)

6. Cardington Modifications (2) Sensor Interface Unit:
The second modification required the careful design and build of a sensor interface unit (by Martyn). It contains a barometric pressure sensor and signal conditioning circuitry to interface the Cardington sensors with the autopilot’s ADC board and an SD card. It is all housed in a box made from Correx sheeting, making it very light and sturdy. I should add that since this picture was taken, the circuitry has been repackaged into a box half the size.
Sensor Interface Unit:
Correx enclosure
Integral barometric pressure sensor (Druck RPT 410)
In-house signal conditioning circuitry
Proprietary ADC board and SD card (SkyCircuits)

7. Cardington UAS: Internal Layout Temp & Humidity Sensor Leads
Pressure Sensor
Sensor Interface Unit
2.4GHz Receiver
Pitot Probe
Anyone that visited our stand at the recent Expo in The Street at Exeter will probably recognise this picture from the poster we had on display and, indeed, is on display here this week. It shows the internal layout of our UAS....
Note the box at the front is the autopilot, which I shall come on to shortly....
Battery Packs
Autopilot
RF Antenna
GPS Antenna I/P

8. Cardington Modifications (3)
UAS Launcher: Desirable Attributes
Lightweight
Collapsible
Single-person launch
Launcher Enhancements:
Increased power
Carriage support
Self-cocking mechanism
Positive release
100% improved reliability!
Our 3rd modification concerned the UAS launcher. You may have spotted our UAS does not have any undercarriage. This is not a problem for landings – belly landings are actually less fussy on terrain type than wheels. However, launches are a different matter. We can’t take off from the ground and a hand launch with a propeller at the rear is not a good or safe option . So a launcher is required to get the UAS into the air. Bormatec brought this launcher out earlier in the year, specifically designed to launch the MAJA. On paper, it suited our requirements for a lightweight and collapsible launcher, capable of a single-person launch. Except it didn’t work.... not even close. However, we have made some drastic improvements, listed here, and we now have a launcher up to the job.
The picture on the right shows the launcher collapsed down and in its carrier, which is roughly the size of a golf bag.

9. Autopilot: SkyCircuits SC2
Autopilot Sensors:
3-axis magnetometer
3-axis accelerometer
3-axis gyroscope
Dynamic & static pressure
Functions:
Selectable levels of autonomy
GPS navigation
Monitor all flight parameters
Hardware-In-The-Loop (HIL) support
Internal RF module (868 MHz) for comms with Ground Control Station (GCS)
Ok, I mentioned the autopilot earlier and this is it. The SkyCircuits SC2. This is the smart device that converts, what is essentially, a radio-controlled model into a true UAS. Inside the model, it is connected between the radio-control receiver and the servos (which are actuators for the control surfaces). A UAS must always have a human Safety Pilot who can assume control at any time. A simple flick of a switch on the radio-control transmitter permits the autopilot to take full (or part) control of the UAS. Its behaviour from this point on is entirely dependent on the route that has been pre-loaded into the autopilot by the operator. At any time, the Safety Pilot can regain control by simply flicking the switch back again.
The autopilot is equipped with all the sensors it needs, listed here, to be able to work out its precise orientation and status.
The autopilot incorporates these main functions..... Selectable levels of autonomy means it can either operate fully autonomously, or part manual/part autonomous. Eg You could fly the UAS manually, but have the autopilot maintain a constant height.
Hardware-in-the-loop support enables you to hook the autopilot up to a flight simulator and ‘fly’ routes in the simulated environment.

10. Autopilot Communications With Ground Control Station (GCS)
GCS To UAS Communications:
Upload new routes
Issue commands
Issue mission scripts/mission updates
UAS To GCS Communications:
Transmit real-time flight data
Transmit real-time sensor info
This diagram illustrates the communication that takes place over the RF link between the autopilot and the GCS. As you can see, it is very much a 2-way conversation. The GCS can upload new commands or mission scripts to the UAS, whilst the UAS sends real-time flight data and sensor information to the GCS, which is subsequently presented to the operator.

11. Autopilot: Planning A Route
The autopilot is accompanied by a comprehensive set of software that runs on the GCS computer. Three packages are provided: ‘GCS’, ‘Plan’ and ‘Flight’. The GCS software covers all aspects of a mission but is also more complex to operate. The GCS main user interface screen is shown here on the left. On the right is a screenshot from ‘Flight’ which illustrates quite neatly a simple route plan.... With waypoints, as you’d expect, defining the route from start to finish, one with an orbiting radius. Note too the Safety Radius. If the UAS flies beyond this radius, a pre-planned safety script automatically kicks in.
Example from ‘GCS’ manual: Main user interface screen
Example mission (extract from ‘Flight’ manual)

12. Cardington UAS Data: Autonomous Flight on 23/11/12
Temperature (Deg.C)
RH (%)
PTU Plots:
Ascent & descent profile for Temp & RH
Ascent profiles more densely populated as UAS takes longer to climb than to descend
Good evidence of stable boundary layer conditions with temperature inversion
Pressure plot shows UAS sensor v MO sensor
Winds data currently being processed
Now I have some data to show you, to bring you right up to date. Our last flight with the UAS was on 23rd November. We flew to a height of 2000 ft and acquired the temperature, humidity and pressure data shown here. (We also have winds data, but it is currently still being processed). The plot on the left of each pair shows the data acquired during the ascent. The plot on the right of each pair shows the data captured during descent. Note there are fewer data points during the descent as the UAS came down much faster than it went up..... Refer to bullet points on slide.
All in all, a very plausible set of data.
Pressure (mb)

13. Cardington UAS
The End
Just to finish off, although I am the one standing here, I wanted to emphasise this development is very much a team effort. Tony Jones built the sensor housing and has improved the launcher beyond recognition. Martyn Pickering designed and built the sensor interface unit. Jeremy and Volker have both been focussing on the autopilot software and scripting. Also, 3 of those people are training to be Safety Pilots.