Difference between revisions of "SUMO"
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= Airframe file =
= Airframe file =
Revision as of 14:29, 19 December 2019
The Small Unmanned Observer (SUMO) has been developed by the Paparazzi community together with the Geophysical Institute of the University of Bergen, Norway. It is designed to support research in the lower atmospheric boundary layer. It uses industry standard sensors for temperature, air pressure, humidity and wind speed/direction as well as more specialized sensors as infrared/visible light radiation, particle concentration or ionizing radiation (full list). It has been used in many measurement campaigns by various research institutions.
As with all Paparazzi software and hardware this does not come with any guarantee. Make sure you follow all applicable rules and laws (safety, radio regulation, ...). No part of the system is certified by any national or international authority. Please refer to the national aviation regulation for Remotely Piloted Aircraft Systems of the accountable country before you start operating. A special permit is usually needed for any activity not related to hobby/recreational usage and especially important if you intend to fly at high altitudes. The experience is that the necessary consultations need quite some time and effort.
Provided below are some weights to aid in estimating an all up weight for your UA
- Tiny13 1.1 Weight: 25g (0.88oz)
- IR Sensor Head: 5g (0.18oz)
- XBee Pro: 4g (0.14oz)
- Hitec HS-55 Servo: 8g (0.28)
- Brushless Outrunner 250W: ~90g (~3oz)
- FunJet assembled, no hardware: 165g (5.82oz)
- FMA Encore 5ch Receiver: 11g (0.40oz)
- Castle Creations Phoenix 35: 24.5g (0.9oz)
The installation of autopilot, sensors and modem is described here. More extensive building not needed if a ReadtToRun(RR) Funjet kit is ordered from Multiplex.
The gyro should be mounted with the PCB perpendicular to the X (roll) axis of the aircraft. So the PCB should be parallel to the YZ plane of the aircraft. The rotation about the X axis is not important.
The sensor FOV is typically around 60-100 deg, depending on brand. Everything emits heat, so you should try to keep the view as unobstructed as possible. There is of course no way to mount the sensors such that they are perfectly unobstructed and a complex set of calibration factors exist in the code to deal with this. Just be sure to keep any obstructions symmetrical, particularly difficult with pitch, and try to avoid having sun-heated surfaces in the FOV - such as the top of a wing, tail, or fuselage.
Avoid placing sensors in the exhaust stream since oil buildup will certainly cause trouble and you may even have problems with hot exhaust. It's important to note that you cannot cover the sensors with any commonly available material - only very special materials will allow LWIR to pass.
Most importantly, keep any video/data transmitters away from the sensors and their wires.
The mounting procedure of the Dual IR sensor is explained by the FMA CPD4 Manual on pages 6 and 7.
Slightly different installation and setup procedures are explained on page 23 of the CPD4 Manual. For planes which:
- Have a low or mid wing, and exhaust flows under fuselage.
- Have a canopy.
Mount the single IR sensor so that it is vertical when the aircraft is in level flight, and has an unobstructed view of the sky and ground. Helicopter blades will not obstruct the sensor's view.
External GPS Antenna
Place transmitting radio devices (modems and video transmitters) as far away from receiving radio devices (RC receiver) as possible. The countermeasures to radio interference should be taken.
The picture below shows a modem install on a funjet, and the Dual IR sensor.
It is ok to place the modem near motor and control. Do not place it near the RC receiver.
Place the RC receiver as far away as possible from any transmitting radio device and from motor and control. On a pusher plane (Funjet) put it in the nose, on a standard plane (EasyGlider) put it in the tail. Especially if you are using older RC equipment (27/35/40MHz) this is important. Modern 2.4GHz RC is less prone to radio interference.
You will get best performance and least interference by placing the video transmitter as far away from any other electronical device, e.g. on the wing tip or in the tail of the plane. Especially if you are using a high power video transmitter this is extremely important.
Build your own
The SUMO is bascially an RC airplane equipped with additional hardware for automatic flight and to collect data for scientific usage. It needs some knowledge in the fields of model airplanes, electronics, hard- and software to build and operate it. One successful strategy for an university research group might be to team up with the engineering department. Get in contact with local RC enthusiasts and ask them to support you in safety piloting the aircrafts. There are many different ways to assemble a Paparazzi aircraft. We are describing a way hat has shown great results in the past years.
The groundstation consists of a laptop, a bi-directional modem, a standard RC transmitter and battery chargers.
The computer should be able to operate outdoors and cope with dust, water, temperature, etc. We have mainly used Panasonic Toughbook CF-19 laptops that never showed any weakness. The recommended operating system is Ubuntu 12.04 LTS.
The modems section describes an overwhelming number of various modems that are available for all sorts of applications. The 2.4GHz Digi XBee Series 1 are proven all-purpose modems that can be used almost world wide. For the ground station we use the readily available Digi XBee USB modem in a robust metal case. It is connected to the laptop through a standard USB A-B cable and brings its own whip antenna.
RC Transmitter / Receiver
The RC world gives you many options to control your aircraft. If you or any supporting team member already owns an RC system, you might try to get this to work. It is important that your RC receiver supports the output of a sum signal that contains all servo data in one signal. You need an extra channel for switching the flight mode. If you start from scratch the Futaba/robbe system is a good option.
There are many different brands and types available and we can not really give a suggestion. We were happy with devices from evoTech or Schulze. Get in contact with your local RC dealer and find a device suitable for you. It is important that the device fits to the power requirements you will see in the field (12V DC/115V AC/230V AC). Do not buy the cheapest available. Follow the instructions carefully, Lithium Polymer batteries can be dangerous.
We chose to use the Multiplex Funjet right after it appeared in 2006. The goal was to have an aircraft that can fly fast to be able to operate in wind conditions up to 15m/s. To achieve an easy take-off for non-RC-enthusiasts we equipped it with a bigger propeller than normal (9x6). Some outer parts have been strengthend with glass fiber. The recent Funjet Ultra can also be used but we do not see much improvement for our goals. It is heavier and the visibility is poor.
The Funjet is not a beginners airplane. Get some piloting help when you are new to RC. You always need a safety pilot that can take over the aircraft.
Use the best RC parts you can get. There is no use in saving some Euros on this. We use Graupner servos, an AXI motor and Jeti motor controller.
Prepare specific electronic parts
These are the non-standard parts you need. Look in the get hardware section for a source of these parts. In the current version of the SUMO we use the Umarim Lite v2 autopilot, a TWOG board as data logger, a Digi XBee Pro Series 1 modem, a Hygrosens temperature sensor, Sensirion humidity sensor, Meas Spec pressure sensor and an optional Eagletree airspeed v3 sensor.
Install electronic parts
This describes how the electronics are installed in the aircraft.
General Electrical Advice
We had immediate success by connecting the motor chassis, the motor mounting bracket, the minus of the motor driver supply, the minus of the servo battery, the minus (ground) of the receivers onto a common ground wire which we laid through the whole plane body from tip to tail. Actually we use a braid from a shielded cable. Remove the insulation, then push the wire mesh shield ends together which makes it easy to slide off the cable, then pull to full lenght again. Finally the mesh was about 5 mm wide flat litz wire. Alternatively one could use thin copper tape which is available from electronics suppliers. High frequency currents run on the outer surface of the conductors, therefore it is important to have as much surface as possible on the ground wires. Connect each metal part to ground, e.g. motor mount.
Twisting is almost as good as shielding. Twisted cables normally do not have to be shielded in moderate environments. How does twisting work?
The electromagnetic field induces interference currents in the wires. By twisting the wires we change the polarity of the induced voltages every twist, and so the disturbances cancel each other.
It is absolute necessary to twist the power cables from the motor battery to the driver board, because there run high pulsed currents and what is true for reception, is also true for transmitting, and the electric noise transmitted from the power cable will cancel itself when run over twisted cables. Needless to say, make the wires as short as possible, from the battery to the driver to the motor. Those components must be placed as near as possible, especially the driver and the motor.
Always use twisted servo cables and remove those 3 pole flat cables from your design if possible!
Grounding loops are not that much of concern as in audio equipment or in microvolt sensors, but there is a general simple rule to ground loops: avoid them.
I do not recommend the use of ferrite beads, because if I need them, my basic design is flawed. Sometimes ferrites help to overcome problems, but I recommend to correctly design and install wirings and shields the proper way. For example, I would lay out the interior of a sensor compartment with thin copper foil or mesh or spray with conductive paint to get a shielded chamber. Of course, I must take care to connect all shields to ground on several places.
Preventing and Fixing Interference
All small-signal cables should be shielded, power cables twisted. Signal inputs should have small capacitors to ground for HF filtering, or an inductor + cap or a resistor + cap. Power cables must have HF capacitors on both ends! Electrolytic caps are not HF qualified. Cables could be connected via "feed through capacitors" and loaded with ferrite beads. Ground connections between the boards should be short and made of litz wires. Card cage should be lined with copper foil and connected to common ground on many places. And so on. Much to be tried out experimentally.
I would start to shield and filter the most sensitive circuitry. Find the point of maximal sensitivity. Switch off and on the various transmitters to identify the source.
Wrap the boards in thin copper sheet, and so on. Line the complete electronics compartment with thin copper and connect to ground. Put a conductive "ground plane" where the antennas are mounted. Adhesive copper shielding tape is available but you must put solder dots all over the tape joints. Conductive paint spray is also available. Create a HF "zero reference" plane where all ground connections meet. "Star" grounding configuration is less important to HF designs, but we must avoid wire loops.
Software configuration setup
Describes the software setup for the SUMO.
Operating the logger
This page describes how to setup and use the on-board logger.
Browse through the wiki for learning how to use Paparazzi. The Users Manual gives a compact introduction to the system.
Misc Airframe Notes
MotoCalc is an Electric Flight Performance Prediction program for Windows and is available for a 30 day free trial. MotoCalc has an internal database of thousands of motors/props/etc. and can make power/flight predictions based on data input.
Electric Motor Calculator by Diversity Model Aircraft is a free online tool for matching props to motors to batteries.
Propeller Thrust Calculator is a free online calculator to give thrust from given propeller and RPM or vice versa.
MultiSurface Aerodynamics is an airfoil and wing analysis software package. The software predicts lift and drag for multiple interacting wings.
Nickel Cadmium (NiCd)
- Energy/Weight: 40-60 Wh/kg
- Nominal Cell Voltage: 1.2V
- Fully Charged Cell Voltage: 1.2V
- Depleted Cell Voltage: 0.8-1.0V
Nickel Metal Hydride (NiMh)
- Energy/Weight: 30-80 Wh/kg
- Nominal Cell Voltage: 1.2V
- Fully Charged Cell Voltage: 1.35-1.4 V (unloaded)
- Depleted Cell Voltage: 1.0V
- Energy/weight: 160 Wh/kg
- Nominal Cell Voltage: 3.6 / 3.7 V
- Fully Charged Cell Voltage: 4.2V
- Lowest Cell Discharge Voltage Before Damage: 2.4v to 3.0v
Lithium-Ion Polymer (LiPo)
- Energy/weight: 130-200 Wh/kg
- Nominal Cell Voltage: 3.7V
- Fully Charged Cell Voltage: 4.23V
- Lowest Cell Discharge Voltage Before Damage: 3.0V
Typical Power Requirements
- 70W/kg (35W/lb) for sedate flying from hand launch
- 100W/kg (50W/lb) for ground take off
- 150W/kg (75W/lb) for performance / aerobatics
External links that could be usefull for this project
- None yet...