Autonomous Platform – The Intro

Building blocks of an autonomous mobile platform may sound futuristic but ever since I was a child, I dreamed of building robots, so I feel so fortunate to be alive and involved in science / engineering in this age as this is all possible on a budget and here is the start of my journey.

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I started to look into learning Computer Vision as i want to build Rovers and Drones that are not only remotely operated but also aware of their surroundings for automated BIM capture to start as a commercially viable platform but with the insight in mind to expand these platforms for emergency service too once the core platform is established.

The mechanical aspects are an obvious hurdle which require knowledge of what role the platform will take i.e. Land, water or Aerial based. What work is to be done, what accessories etc. It all starts to take physical shape working back from the design brief / CtoQ’s / Goals or scope of the design vision.

Once you have the basic mechanical concept then Electrical components start to take shape to provide the mechanical structure with the motion it requires for the length of time required between charges and also the charging / automated battery swap criteria. I use battery swap loosely as when designing electric powered vehicles, I do not rule out liquid batteries which drain and fill electrically charged fluids rather than a solid lump of a battery.

Once the bulk of the electrics are designed, you can start placing the control electronics and sensing devices (camera,lidar, Ultrasonic, bump switch etc) but modifying the electrics to suit.

That just about sums up the overview of Robotics Hardware which for an engineer is not easy but not an impossible challenge either.

Now for control software we could start from scratch using Java ( which is not freeware for much longer) or Python ( which would be great) but for most standard platforms there already is Open Source Robotic Control Software (flight software) ready to be tweaked. For Rovers (land based) see Ardupilot.org and in fact this will do every vehicle type but for Aerial platforms, also look at px4.io or droncode.org as these are industry supported and in development. I will also mention that you need a compatible autopilot hardware kit, which for me with a raspberry Pi 3 will be the Navio2. These tend to come with a GNSS antenna for high location precision.

There is also numerous open source ground control and mission software like QGroundControl.com using MAVLINK or Mission Planner. If using a PC, you will need a telemetry transmitter and receiver kit(433 or 868MHz for UK, 900 for USA and Canada). There are numerous free offering for tablets too in Android or IOS flavours.

Ok So we no have the blocks to create a fully functioning remotely controlled semi autonomous vehicle but how do we make it autonomous. Well that, ideally would take LiDAR and Computer Vision with OpenCV.

LiDAR is an option at this point but with limited open source options we will leave this for a more advanced Robot ‘The Mark 2’.

So lets talk about Computer Vision. This is the route that Car manufacturers are going down, with support of LiDAR, and is all about detecting dangers and picking out data from the camera and turning that image data into usable sensory information that can be processed by the Controller. To do this we can use a piece of open source software called OpenCV. I will mention that OpenCV will also process LiDAR data so we can expand the capabilities later.

This will turn the image data into code which we can interact with using Python code.

At this point I will mention that I am not going to create videos on how to use OpenCV myself because I have found an abundance of youtube courses which are perfect so why remake the wheel. Instead I am going to compile pages with other peoples videos and supplementary information to help cover all bases. This means that I can write faster and other kind people who have taken the time to create content get the boost from more views on their videos.

I will however embed the videos and also give the code from the video which I have tested and added comments – yes we are all doing this together.

So without further a do, lets get on with learning OpenCV and really get our robotics alive. Once we understand how this all works, we will come back to the design brief capabilities and then hopefully on with the design and build. This should be fun, as is most blue collar engineering, but please share the posts with colleagues / friends and comment back with suggestions. Don’t forget you can always email privately at contact@vulcanrealm.com.

If you are looking for all the current lessons then please look under this page’s dropdown in the navigation menu to the left.

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Indoor Drone Flying

Indoor Drone Flying has its disadvantages regarding autonomous flight but has many benefits including

  • No CAA Licence required – The CAA is only interested in external airspace and has updated its ANO (Air Navigation Order) to reflect this – in short, if it cant escape into an external airspace then it now falls under Health and Safety and not the Airspace legislator. This also goes further to include netted structures. Having said that, your Health and Safety may want you to have a licence as a competency requirement much like a driving licence but this could also be an in-house course. https://www.caa.co.uk/Consumers/Unmanned-aircraft/Recreational-drones/Recreational-drone-flights/
  • Small drones can reach places for inspection where it may be impractical to send a person i.e. confined spaces or into tall buildings to alleviate the working at height risks or cover search areas with thermal imaging to look for people or faults.

So I am liking this concept and sure enough there is a solution on the market – Enter the ELIOS 2 from Flyability. At this point I will say that I am not on commission and have only seen one of these on display by COPTRZ at the GeoBusiness day.

Image of ELIOS 2 Indoor Drone
An Image of ELIOS 2 indoor Drone (photographed from the COPTRZ brochure)

So this drone is in the realms of £25k but it boasts the following:-

  • Collision resilient cage (Carbon Fibre 40cm Diameter)
  • GPS free Stabilization
  • Distance Lock from object if monitoring one object – i.e. an automated process or inspecting structures – I am thinking visual inspections of aircraft skin joints in a hangar would be one great application with the oblique lighting. Thermal imaging of composits in-situ (an authorised work process would be required of course) etc
  • 4k Camera
  • Thermal Camera (FLIR)
  • 180 degree tilting camera pod
  • Adjustable and Oblique Lighting upto 10k lumens. This is also Dustproof.
  • FPV without line of sight
  • Flight and Reporting is performed via the Cockpit 2 software
  • 1 day of training to get the most out of it.
  • Transport case
  • Remote Control (2.4GHz) and Samsung Tablet
  • IATA approved for carry on Luggage

 

All that with a 10 minutes flight time but with a 1 min battery change time, you could inspect whatever you wanted and send the video or images to the relevent qualified person to study.

One minute a 737 Bulkhead inspection, the next an A380 paint inspection after a storm – One person on location and the expensive engineers at home base for the time duration required – no more or less. Maybe even some post maintenance inspections can be performed remotely this way reducing senior engineers physically onsite.

What does this mean – No more flying teams of engineers with every tool for every eventuality or erecting scaffolding to inspect/appraise faults. You just need a drone operator and a remote engineer.

Imagine the time resource this will free from travel as well as the carbon footprint. This is Proactive Workforce management but of course Regulations and best practices apply and as always I am trying to start a conversation with ideas for you to debate not go ahead and act based on what you have read. Please see site usage terms and conditions for more information.

For more information or Demo please visit the flyability or COPTRZ websites.

If you do, please let them know you saw it here and they may let me review one.

 

Wiring protection techniques

There are many ways in protecting cables from damage which range from correct routing and bunching to adding extra protection to the cables insulation or outer sheath. We need to discuss a few as you will have to recognise what is to be used when and how. We shall begin with looming which is bundling of a group of wires to route them through the Aircraft or vehicle in an organised fashion. The looming of aircraft wires should always be done carefully and in accordance with the Aircraft Wiring Manual. Failure to comply with this fundamental rule can have fatal consequences. for instance, if a fuel tank sensor wire was loomed with the main generator output cables and after time the loom were to chafe and expose a couple of wires on the main generator output cable and maybe just one wire strand on the fuel tank sensor wire, then there is the possibility that a high electrical charge may be passed down the sensor wire, creating a big spark inside of the fuel tank with the possibility that it might ignite the fuel vapour inside the tank and thus i need not say how catastrophic this could be. ALWAYS PERFORM IN ACCORDANCE WITH THE MANUAL SO THAT THESE THINGS DON’T HAPPEN, IF THEY DO HAPPEN, THE AUTHORITIES WILL CHECK TO SEE IF YOU PERFORMED THE JOB CORRECTLY. REMEMBER YOU ARE AN ENGINEER SO BE PROFESSIONAL. Now if you still wish to pursue this career then we shall continue. Wire looms are generally large in size so they are generally tied with a bundle or loom tie and then broken down into groups which are tied with a group tie. These ties used to be tied with lacing cord which in the main is being phased out and replaced with plastic cable ties no different than what you may find inside your computer or behind your car dashboard except they are approved for aircraft work. When using lacing cord or cable ties, it is important that the tie is tight enough to prevent movement down the loom but not so tight that it bites into the insulation of the wire as this may aid fraying of the insulation. Lacing cord should be tied and secured with a double knot. Cable ties are self locking for a more professional and permanent fix. Cable looms may run for long distances through the aircraft and because of this, cable loom supports known as ‘P’ clips are used at distances stated in the aircraft maintenance manual. As a general rule, the loom should be supported so that no wire is stretched during the expansion and constriction due to the hoop stresses endured by a pressurised aircraft structure during normal flight operations. Having said this, it is not permitted that the loom may exceed more than 1/2 an inch deflection between its supports when the clamps are tightened and a moderate hand force is placed on the loom in the middle between the two clamps. When routing looms near plumbing lines, they should always be level or above the pipeline and it is no closer than half an inch although a six inch gap is preferred where possible. If the gap is less than two inches then a sheathing resilient to the fluid carried in the pipeline should be used especially if it is oxygen or hydraulic fluid. Obviously it is not preferred that looms are routed near moving components but sometimes it is inevitable. When this is the case then there must be mechanical guards fitted to protect the cable and a distance of at least three inches must be maintained from the components path of travel throughout its entire range of movement. When securing cables by cable clamps or p clips, the clamp must be secured directly to the structure if it is being used to support the loom, but if it is only to maintain the spacing of the loom between plumbing lines and the loom itself, then providing that the minimum distance spacing is achieved, then a P clip around the loom may be bolted to another P clip located around the plumbing line may suffice. The bend radius of a loom should be gradual and constant, preferably of approximately ten times the outside diameter of the loom in that area but if the bend must be Tighter then, providing it is adequately supported then a bend radius of approximately Three times the outside diameter of the loom in that area is possible but always check your aircraft standard practice manual. Shielded or screened cables are cables that are covered in a metal braid. This metal braid should be turned back on itself at the end and secured with tinned copper wire or should be cleanly cut off without damaging the insulation or the wire underneath the braiding. If the wire to be routed is a co-axial cable then it must be routed in the most direct manner as possible. Important note; It is not permitted that an unscreened radio aerial lead be passed any closer than 18 inches to any other unscreened aircraft cable. Heat shrink wrapping of wires is a simple process of slipping over an approved piece of heat shrink of the desired length and diameter just slightly larger than the wire or wire group and heating with a WARM air gun set to the appropriate temperature for that heat shrink. Remember if it is too hot you may damage the wire itself.

Connecting Electrical Wire/Cables and Connectors

Connection of wires is performed, in the majority, by two methods either by the use of plugs which insert in to a mating plug with a special external barrel with a screw thread which is turned to lock the connecting plugs together or by a form of terminal block. When using terminal blocks it is important to know the proper installation practice to prevent corrosion and damage to the block and terminals.

If you are connecting copper wire terminals to the block then you should

  • Connect the wire terminal directly onto the nut securing the terminal block stud.
  • Place a plain washer over the terminal.
  • Followed by a self locking nut or, if there is not a self locking nut available, you may use a spring steel locking washer followed by a standard nut.

If the terminal you are connecting is for an aluminium wire then you should

  • Place a plain brass washer over the terminal block stud securing nut
  • Then place the wire terminal onto the stud.
  • Followed by another plain brass washer
  • Then either a self locking nut or spring steel lock washer followed by a plain nut.

If you must connect an aluminium wire terminal and copper wire terminal to the same stud then the following order must be achieved:-

  • Place the plain brass washer onto the terminal stud followed by the aluminium wire terminal.
  • Place another brass washer over the aluminium wire terminal followed by the copper wire terminal
  • Then place a plain washer followed either by a self locking nut or a spring steel lockwasher and plain nut.

Please note that unless the wire terminals are of different materials i.e. copper wire terminals and aluminium wire terminals, then no washer should ever be placed between them.

Electrical Wire Crimping Techniques

Crimping is a method of attaching a terminal lug to an electrical wire. This gives us the advantage of being able to connect and disconnect wires from units without the possibility of damaging heat sensitive circuitry by hot soldering irons.

This crimping operation sounds complicated but is not. Depending on the material of the wire being either aluminium or copper, dictates which of the following crimping methods should be employed.

Aluminium wire crimping is carried out in the following manner:-

  • Refer to the relevant wiring diagram and maintenance manuals and IPC to find out the correct crimp terminal and paste ( Normally petrolatum and Zinc based ) to use ( the barrel of the crimp lug is normally provided half full of crimp paste).
  • Strip the insulation on the wire back sufficiently to be able to insert bare wire into the terminal lug sufficiently so that the bare wire reaches to the end of the barrel ( there is an inspection hole at the end oof the barrel to confirm this ) and so that the insulation butts up against that back or entry point to the barrel.
  • Cover the inspection hole or the end of the barrel with your thumb or finger to prevent the paste from escaping and insert the wire into the barrel of the lug.
  • Now using the approved crimping tool for the terminal ( as designated by the terminal manufacturer ) Which is normally in the form of a set of crimping pliers which may cover a range of crimp sizes, Select the appropriate jaw for your terminal and squeeze the handles together tightly ( modern crimp pliers normally have a ratcheting mechanism which will not release until the crimp is satisfactory to give you a perfect crimp joint between the terminal lug and the wire).
  • If the terminal is not normally pre-insulated so then you must use an approved insulation sleeve which is normally transparent and tied to the wire with a lacing cord to prevent it from moving. This insulation sleeve must cover the barrel and about 3/4 to 1 inch of insulated wire behind the terminal.

Copper wire crimping is carried out in the same manner as aluminium wire but there is no need for a crimping paste to be employed. The reason why aluminium wire crimp joints must employ a crimp paste is because of the inherent tendency for aluminium to form an oxide layer on its surface. The crimp paste breaks down this oxide layer and prevents it from reforming by excluding any air or moisture form the joint.

Copper wire terminals may also come pre-insulated but if not then they must have an insulated sleeve tied to them in the same manner as the aluminium wire.

Pre-insulated copper wire terminals may be identified by the colour of the insulation on the barrel with reference to the relevant data provided by the terminal manufacturer.

Testing of Crimp Joints

The inspection and testing of crimped joints is carried out in accordance with British standard G178 and the cable manufacturers recommendations or Aircraft maintenance manual.

In general though you are looking for a secure crimp fitting with sufficient cable purchase, not exposing un-insulated wire and with a very low resistance from one end of the cable to the other end of the crimped joint.

Electrical Bonding Techniques and Testing.

Electrical Bonding is a method used to equalize electrical charges throughout all components on an aircraft or system by creating conductive paths for any charges to travel through with a minimal resistance. Maybe when you were younger, you rubbed a balloon in your hair and watched your hair stand on end towards the balloon or rubbed your slippers on the carpet and touch a radiator to see that static spark ( not recommended of course) which is similar to when an aircraft or vehicle passes through air or storm clouds. This is only one issue regarding static but there are many reasons why we bond aircraft and there components, these include:-

  • To prevent high electrical voltage potential differences.
  • To route this high electrical voltage in a way that would not malfunction the aircraft or its components.
  • To minimise damage or injury to the aircraft and its occupants.
  • To minimise radio operation problems
  • To prevent static charge build up
  • To earth the aircraft to the ground via the special conductive nose or tailwheel or boom extended to prevent harm to occupants and personnel when leaving or entering the aircraft.

These reasons determine what type of protection is used and are then placed into two categories which are titled Primary Conductors and secondary conductors.

Primary conductors are the conductors that carry the high voltages i.e Lightning strikes

Secondary conductors are the conductors that carry the lower voltages like static build up.

Because there are diferent types of problems that bonding deals with, the bonding leads and bonding path must be suitable for all the tasks that they must perform.

When bonding between components, panels and structures, it is necessary to remember the following points:-

  • Braided conductors made from aluminium or copper wires, may be used for either primary or secondary conductors, but always remember that if the conductor needs to be replaced, you must always refer to the IPC but for the exams sake, you should select a conductor of the same length and material as the original but with a greater cross sectional area.
  • Terminals should be clean and and the bonding lead secured, it is required that the terminal and bonding lead connector be treated to prevent corrosion, this is normally achieved by a form of a sealant.
  • The routing of bonding leads should be as straight as can be with all sharp bends avoided and routed in a manner that does not interfere with the operation of any equipment.
  • The end terminal lugs on the cables. leads or wires should be either soldered or crimped, these processes will be discussed later.
  • Always refer to the wiring manual to ensure the correct routing and quantity and specifications of the bonding lead.
  • There is one more point in regards to the installation of bonding leads that you must be aware of, and that is in regard to magnesium based alloy structure or parts. Due to the corrosive nature of magnesium, the component manufacturer may make a special lead for the bonding of the component, but in the absence of this, you may use a aluminium alloy bonding lead connected indirectly to the magnesium structure i.e. via a mounting bolt or bolted connection that does not move.

Testing

Bonding leads and jumpers are tested using a 250 or 500 volt ohm meter. Before use the tester should be inspected for the following:-

  • – The ohmmeter unit has not been damaged or tampered with
  • – The leads have not been damaged or repaired ( no repairs or modifications allowed.). If the leads have been damaged then the meter must be fitted with a new set of leads and recalibrated with those leads.
  • – The probes are not damaged or corroded and have a good point on the end to break through the coatings on the metal.
  • – After inpecting the condition of the meter, the unit should be switched on and the probes shorted out to give a full deflection of the scale so the needle registers 0 ohms. There is usually a fine tune knob located on the unit to set up the scale before use.

When testing bonding leads or jumpers it is required that all bonding lead connections not be any greater in resistance than 0.05 ohms.In many installs, the manufacturer may require a lower resistance figure and therefore the lower figure should always take precedent.



CHAINS AND THEIR ACCESSORIES – Aircraft

This article was written according to aircraft standards but the principles of Chains remain the same but if applying the knowledge to low power chains on Bicycles, Then you can make your own risk economic based reduced standards. If working on aircraft, always refer to the Maintenance manual.

The purpose of chains is to transfer power from one sprocket to another transfer kinetic(motion) energy. To accomplish this task you need at least an assembly of chain(s)(manufactured to SBAC standards like BS228:1994 or ISO606-1982), sprockets(toothed wheels) and possibly other accessories like interplaner blocks for changing the direction of the chains.

We will start with the main unit called the chain. This is an assembly of:-

  • outer plates
  • inner plates
  • Rollers
  • Bearing pins
  • Bushes

The pitch of the chain is taken from centre of one roller to the next one i.e. the distance between the bearing pins.

Maintenance

Chains riveted links are not allowed to be broken down and re-riveted and only accepted from an approved manufacturer, with the correct packaging and transportation precautions taken.

It is permitted that a bolted joint may be disassembled and re-assembled, but, it is worth while noting these next few points.

1) SBAC states that all nut and bolted chain assemblies must be peened with the exception of the 8mm variety which must be split pinned

2) All nuts used on the chains must be locknuts(this nut is normally part of the outer plate)

3) All attachments must be either riveted or bolted

4) SBAC have standardised four sizes of chains by pitch size

BUT

British Standards have laid down the proof load as one third of the minimum breaking load (mbl)

5) Continuous(endless) chains must consist of an even amount of gaps between rollers(pitches)

6) The following table is the four classifications of chains and their statistics.

PITCH — MBL(lbs) — PROOF LOAD(lbs) — BS
8mm ——— 800 ————- 267 ——————— 1
0.375″ ——- 1900 ———— 634 ——————— 2
0.5″ ———– 1800 ———— 600 ——————— 4
0.5″ ———– 3500 ———— 1166 ——————- 6

7) A non-reversible chain is a chain that may only fit a certain way round which can be achieved by correct unsymmetrical positioning by the outer plates fitted to the chain.

8) Irreversibility can be achieved by

  • Non-reversible chains
  • Non-interchangeable end fittings
  • Correct positioning of sprockets
  • Guards and shrouds

9) When storing a chain it must be well soaked in the approved oil, laid flat on its side on top of greaseproof paper and coiled firmly (not tight but not too loose).

GENERAL INSPECTION

This unit is used as a high strength power transfer device. When inspecting the chain make sure to check the proceedure in the maintenance manual which should at minimum account for the Following

  • Wear on the sprocket ( See spec in aircraft manual)
  • Wear on the rollers ( See spec. in aircraft manual)
  • Twisting (This is cause for rejection)
  • Stiffness ( This can be determined by drawing the chain around the fingers on your hand or maybe a substitute of the same sort of shape and texture [ You do not want to damage the chain by scraping the links on an object used in inspection] and checking for smooth articulation of the links. If stiffness is detected, the chain may first be cleaned and re-checked but if this is not a solution, the rollers may be lightly TAPPED preferably with a small pin hammer. if this does not fix it the chain is the scrapped.
  • Deformities, Cracks or corrosion ( These is cause for rejection)
  • Overheating (Bluing)
  • Elongation (Maximum of 2%)( To check for this the chain must be cleaned and dried with compressed air. Lay the chain flat and straight and apply a tensile load/ force [see table below]. Now measure the distance between all the pin centres and apply the following formula:

Percentage of Elongation (Method 1)

Length Of Chain with Force applied x (No. Of Pitches x Pitch measurement)
———————————————————————
No. Of Pitches x Pitch Measurement

Note: All measurements are in inches

Tensile load required on Chain (Size is British Standard)
Size – Load (lbs)
1 —- 12
2 —- 16
4 —- 28
6 —- 28

Percentage of Elongation (Method 2)

Measured Length
——————————— x100
Original Length