CCITE

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innovative organisations committed to the improvement

of technological education for young people.

The Centre for Innovation in Technological Education in Cambridge http://ccite.org

Ohbot – a humanoid robot system for schools Adrian Oldknow 27th April 2015 I came across Ohbot from a posting on the Computing At School (CAS) group website in January. This was at a time when I was writing a guide to many of the programming systems and hardware now available to support `tinkering’ (or `physical computing’). These are collected in the `Contributed’ section of the National STEM Centre’s eLibrary: http://www.nationalstemcentre.org.uk/elibrary/media/547/learning-to-code-with-a-purpose. The short section 22 in Part 5 of that guide shows the state of my knowledge then.

22. More Robotics - OhBot: This is another UK invention currently being crowd-sourced. £80 buys you the top-of-the-range model with 6 motors to control: http://ohbot.weebly.com/ and

http://www.crowdfunder.co.uk/ohbot-robot/backers/ . There are some videos from BETT show 2015 at: http://ohbot.weebly.com/bett-videos.html . Matt Walker and Dan Warner have set up a company called Loopy Computy in Stroud: http://www.loopycomputy.com/about.html . So I took the plunge and pledged my 80 quid at Crowdfunder: http://www.crowdfunder.co.uk/ohbot-robot. Here is their pitch: “We think children should have access to a creative robot system which is modelled on themselves, which they can program to talk, display emotions, act, react and solve real world problems. So we are developing Ohbot, a kit robot that primary children can assemble in an hour, connect to a computer and bring to life by scripting programs using easy drag-block software modelled on Scratch. Ohbot will come with a pack containing the kit, straightforward making instructions, software and challenge projects developed by experts. The sequence of learning-through-making projects will challenge children to turn Ohbot into a story teller, a street performance poet, teacher, actor or helper. Children will be introduced to key programming concepts including sequences, repetition, selection and variables through applying them to make Ohbot work. This is tailored to address the demands of the Computer science elements within the new curriculum for Computing. WHAT'S NEXT? We need innovative teachers and learners to trial Ohbot and help continue the development process. If this sounds like you and your class please pledge. Ohbot is launching in the Futures area at the BETT Education Show in London on 21st January 2015. `Ohbot’ is a collaboration between Dan Warner, a teacher and former LA advisor, and Mat Walker, a roboticist with experience building humanoid robots to do real world jobs. With your pledge you can secure a development kit of one of the first run of this exciting new resource. For £80 you will receive one Ohbot (6 motor version) with drag-block control software and a pack of supporting educational resources. ” So now my own kit has been delivered I have started to get to grips with how to make it, what it does and how it can be used. The Ohbot team make it clear that backers like me are members of the development group – and they provide plenty of means of information, help and communication including: Instructions: http://ohbot.weebly.com/uploads/2/1/8/3/21834178/ohbot_instructions_crowdfunder_v2.pptx.pdf Notes for owners: http://ohbot.weebly.com/notes-for-owners.html Help: http://www.whoosh.co.uk/ohbothelp/help.html#examples.

Founder: Prof. Adrian Oldknow, Church Lane House, Eastergate, Chichester, PO20 3UR adrian@ccite.org

The instructions are pretty good, but at times they could usefully provide a little more detail and additional photos/video/audio. The head is built up from around 18 shaped pieces of dark blue plastic. Each piece has a number of holes and/or slots and either side is covered in a thin protective layer of pale blue plastic. It was only after I had built the complete assembly that it dawned on me that perhaps I should have peeled off the plastic coating BEFORE I started the assembly. I have now torn off the coating from the external faces of the pieces, but left the inside of my robot’s skull to be lined with a thin protective layer of plastic in lieu of mucus! The full 6-motor version of Ohbot has its brain between its shoulders – this is the Micro Maestro 6-channel USB Servo Motor Controller 1350: https://www.pololu.com/product/1350 . A UK supplier has this priced at £15.76 http://www.hobbytronics.co.uk/pololu-servo-controller-6. There is a manual at: http://www.hobbytronics.co.uk/datasheets/pololu_maestro.pdf

The 5 small servo motors which perform the fine movement s are each Tower Pro Micro Serve 9g servos. A data sheet is at: http://datasheet.sparkgo.com.br/SG90Servo.pdf . They cost £3.10 each from http://www.servoshop.co.uk/index.php?pid=SG90G. The large servo which moves the whole head assembly is a Futaba S3003 which costs £7.70 from: http://www.rcworld.co.uk/acatalog/Futaba-servos.html. So that’s about £30 (retail) just for the over-the-shelf electronic hardware in the Ohbot box. Some of the structural panels are held together with bolts and nuts, others using lengths of plastic cable tidy. If you look carefully at the lower front edge of the `cheek’ panel on the left below you can see that I have had to enlarge the slot using a hack-saw to get the upper jaw to fit in – hence the slight `hare-lip’!

The head can nod up and down as well as turn left and right. The jaw can open and shut. The eyes can swivel left and right as well as look up and down, and the eyebrows can be raised and lowered. The picture on the right above shows three of the linkages (copper wire) connecting servo arms to perform different movements. The one on the left controls the tilt of the head, the one on the right makes the eyes move up and down, and the one at the top moves the eyes left and right. Installing the software is a two part process. First the Maestro Control Centre is used to establish contact with the servos. You can use the sliders to control each servo manually to check the linkages are working properly.

Once the communication with the servos has been initialised you can exit the Maestro software and run the Ohbot software – which is for Windows 7 and 8. When you run the software you have several windows on display. The top left has the start, rewind and stop buttons. The next below simulates the movements of the Ohbot whether or not one is physically connected. The bottom one shows the output from a webcam – in this case it has detected my face. In the middle of the screen is the window with the Scratch-like commands for Ohbot, and on the right is the program editor space.

I have used the `settings’ menu tab and selected `motors’ to show how the servos can be manually set using sliders. The password is `Einstein’! Now you are all set to start programming. Now is a good time to start reading the online `Help’ info and exploring the Example programs.

So here is my very first Ohbot program. In principle nearly all Ohbot’s inputs come via the computer. They can use peripherals such as the web-cam to gather intelligence from images – such as the position of your face or hand in the image window. I am using just the keyboard and the mouse to control the program. This uses two built-in variables called `mouse x’ and `mouse y’ which range from 0 to 10 as the mouse ranges over the whole display screen. These are used to control the servos which turn and tilt the head. The program starts when the green `start’ flag is clicked and ends when the space key is pressed. The exception to the input rule is that you can measure the position of any of Ohbot’s servos. So the variation on the theme tests the state of the `HeadTurn’ and uses it to control the mouth. Similarly we test the state of the `HeadNod’ and use it to control the way the eyes look. The Ohbot software also utilises the Microsoft Windows speech recognition system as show by the example program below.

It also uses face recognition from the webcam connected. At first I tried to control it by moving my own face in front of the camera, but then I accidentally found that it also recognised an ornamental china doll on the shelves behind me. So I swivelled the camera away from me just to pick up movements from the doll.

The software also allows Ohbot to use the computer’s loud-speakers to provide spoken output. It can also access the computer’s clock as well as current weather data for your locality from Yahoo! Messages can also be sent and received to control actions.

I hope this has given enough of a feel for what Ohbot can do for you to want to buy, make and use your own. Whether or not Ohbot goes on sale is a matter for its designers, but personally I very much hope it will be available BOTH for schools AND families to purchase. I particularly like the way the designers have used (their own variant of) Scratch as the basic language system for feedback and control. I would like to have some more maths functions like sine in the Operators as well as the facility to name procedures as well as variables. I very much like the sense of engagement you get by having to build it for yourself – you really do feel some kind of bond with the object which you don’t get by buying ready-made robots like Edison, Robotiky or Robosapiens. I think the instruction manual is a good start, but an overview video of the stages of construction before you start would have been helpful. The other nice thing is the sense of openness about the whole project. I was very happy to pledge for this project through crowd-sourcing – as I have also done with Code Bug, Edison, Robotiky and Soldering System. Now as a pilot-tester for Ohbot I feel I am part of a community. I am even starting to follow Ohbot on Facebook, Google groups and Twitter – and made my first posting! So it came as no surprise to receive an e-mail from the Ohbot team less than 24 hours after I had made my Ohbot to inform me of the problem with the slot in one of the cheek pieces and to offer to send a replacement! There is a fascinating time-line showing the stages in Ohbot’s development at http://whoosh.co.uk/ohbottimeline/. This brings home the way a good design idea can be taken from the drawing board to a successful product – something which our students currently taking D&T courses at school (not to mention their teachers) could really benefit from. I like the idea that given access to the right tools such as laser cutters and 3D printers and good software such as AutoCAD, Inventor and TinkerCAD any of us can build our own projects.

The idea of servos and linkages as combining computer control with mechanical engineering is again something new for me. It helps me to understand how Robosapiens works and to see how we have used bio-mimicry to replace muscles, tendons and neurons. Since Ohbot is a static device it just stays hooked up to the computer with its USB cable. But I can also see how the same control board and servos can be used with wireless control to fly model aircraft, drones, helicopters etc. as well as the new up-market sailing boats. I was very excited when I first saw that Scratch could be used with LEGO We-do for feedback and control – but equally horrified by their prices. Very quickly we are seeing a range of British designed microelectronic devices which offer much more scope to the imagination at much more affordable prices. The system also reminds me of the model industrial robot created by ST Robotics called Go Forth Robotics using an ARM mbed controller, servos and a Meccano chassis: http://forth-robotics.org/materials.html . The one aspect of Ohbot’s software I have not touched on is the simulation screen which shows a computer animation of a 3D model. So I thought I would have a play with the 3D animation in the free GeoGebra software to see if we can make that work like the servo and linkage controls work on Ohbot. First we’ll examine just one linkage in detail in 2D – the one controlling the nodding movement using the servo on the left cheek when viewed from behind. There are two fixed points in the lower region, the neck. One of these is the centre of the axle around which Ohbot nods (E), the other is where the copper rod is secured (D).

The `four-bar linkage’ DEFG defines the current position determined by the position of the servo F and its arm FG. In GeoGebra you can import a photo, resize it and change its transparency – which is a great help. In the quadrilateral DEFG all the lengths are fixed constants – we can just change the angle EFG by moving the servo. Unfortunately I can’t find a simple geometric way to construct the position of points F and G given the value of the angle EFG. So I have had to resort to some trigonometry called the `cosine rule’. Knowing lengths b = FE and e = FG and given the angle EFG we can calculate the side g = EG. Using the same rule in reverse in triangle DEG we can then calculate the cosine of angle EDG. Since DE is fixed in space (or in the neck) we can just rotate E around D through the computed angle EDE’ to find the new direction of the linkage DE’ and hence the new position of its endpoint G’. We can now locate the new position of the centre of the servo F’ as the intersection of two circles of known radii. To test the system I have created the circle centre A with an arc HK defined on it for the point J to slide and to define the servo angle KBJ. Using this for EF’G’ allows us to calculate the corresponding EDG’ and hence to draw the new position of the linkage DEF’G’. Now we are ready to go into 3D! Sliding the red point turns the head left and right and sliding the green point nods (part of) the head forwards and back using the same computations as for the 2D linkage.