This page is to help teachers to get their teams ready for Robocup NZ. This is a ‘free to use and share’ resource. I have compiled it together from my experiences competing in Robocup, reading material online and building some of those robots myself. This ‘getting started’ series is just to help you make your choices and provide some links to good resources to build your robot specifically for the competition.
Week 1: Making an autonomous Line Follower using Lego NXT 2 or EV3 kit
The one big advantage of using the Lego system is that the program to make a (simple) line follower is very straightforward. Building the line follower is also enjoyable as its Lego! No need for external motivation and the bits seamlessly fit with each other.
Categories:
Primary – for upto year 6.
Senior – everyone else not in primary, who have built robots for the competition before and won a place, and also the ones with custom bots ( like using Arduino over Lego NXT kits).
Premier – Open for all groups but more complex tasks.
Differences in the three categories: In primary and senior rescue you follow the line and then eventually get into a space to rescue ( push) the water tank (can of coke usually covered in tin foil on which the person is stuck) to safety (out of the green zone).
In Premier Rescue– there is a maze of lines to navigate through, go around an obstacle, before coming into an area where you rescue (lift) the water tank (can of coke) and place them in a safe location ( usually a raised platform like a brick).
The empty can of Coke will have 60grams of weight added to it.
Dimensions: Robot should not be over 22 cms in diameter which is fairly large (for premier its 30cms) . Some teams put the motor units vertical to save space which isn’t a bad idea either. There is a height restriction as well, 18cm for primary and senior while Premier its at 30cm.
Points: Even though the objective is search and rescue, there is definitely some motivation along the way (10 points for every tile completed) and there are points for navigating certain turns ( for the full set of rules download this attached form).
Build: Be creative and stay within the size limits. Good practice is to have your line sensors close enough to your wheels so when you are receiving the reading from the sensors, the turn is effective relatively closer than further away. You don’t need to buy a color sensor as you can use a light sensor to detect the difference between dark and light (black and white in this case). IMP: You have to work around the sensor values on the given day of the competition as the lighting will be different when you programmed in class to lighting conditions at new location.
Program: This program is to make a line(edge) follower which means it measures the difference in the (threshold) value set and observed value to work its way forward. However, there are more complex programs that you should be aiming to make with a combination of two sensors if you have access to them, which then makes it more effective than an edge follower!
You can collect readings from the light sensor on the reflected light using the onboard program under “NXT datalog”, which will be helpful when playing around with adjusting values in the program.
Light Sensor vs Color Sensor: The light sensor is part of the NXT 2.0 standard kit and the color sensor is an extra hundred odd dollars plus shipping from www.teaching.com.au so its quite an extra burden on teams; however it does the job and you continue working on the same Lego platform. You can make a decent line follower with 2 light sensors though (instructions in links below).
Another approach is to find after market products for sensors like in here, Mindsensors that make sensors for Lego and have a line sensor http://www.mindsensors.com/ev3-and-nxt/48-line-follower-sensor-for-nxt-or-ev3 of which the test video is https://www.youtube.com/watch?time_continue=89&v=isf2Kz_jdrA It looks very effective; however it is to note, they used RobotC for coding and that might be an extra learning curve for some students.
Getting started: Now that you are sort of ready with some background knowledge, you should get started with building your robots. However, if you are still struggling for ideas and need in depth knowledge on how things work, then the link below is a good guide.
https://www.youtube.com/watch?time_continue=133&v=T9GcZFmZzFw
Furthermore, the link to all Robocup line follower tutorials are provided here again on Robocup Australia page: https://www.robocupjunior.org.au/tutorials
Dr.Damien Kee has good resources on his website if you are interested in robotics.
Next week, I will post a similar post; however using the Arduino platform.
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Session 4: Hopefully this was the last session for construction. Students started to apply their final touches. A few important questions came up. The battery pack which sits just above the servos is a tight fit. It was hard to remove the battery pack every single time it ran out of charge. One solution was to get rechargeable batteries and make a connector plug which will easily swap between the Arduino and a recharging unit. Another alternative was to use a LiPo which will easily fit in the space.
I realised that I have a LiPo charger for my Radio Control Toys and a few LiPo’s around the 9V mark which is the upper limit of the Arduino (2S will make 7.4V which I think should be good enough).
Session 3: Our chassis had arrived and we started putting them together using the online tutorial. The laser cut acrylic sheets were a breeze to put together. However, a certain glitch in the cutting because of the angle of the laser cutter meant that the servos would not sit without a bit of adjusting. But students enjoyed the tinkering as it brings out the engineering aspect to modify existing designs to suit their purpose. The whole bot was complete for just under $50 as we got bulk discounts on Arduino’s, Servo’s and the battery packs. Students will keep the robots if they like after paying the parts cost.
Another issue we faced was the front castor wheel and gluing it using a hot glue gun. It wasn’t the strongest of glues which is why we decided to screw it on or use Super Glue. We also needed marbles to pop in the front wheel castors and asked students to hunt for them around their houses.
Session 2: Our sessions are on the first and third Thursday’s of each month. In the second session we looked at Sumo Bots. We decided that it would be ideal to learn robotics through using an existing design at this early stage so we can learn more about the functionality without any pressure of intense construction. John used his resources at Vic to build the chassis for the Sumo Bot. All plans are available on GitHub (https://github.com/makenai/sumobot-jr) and it looked real easy to put together.
While that was in the pipeline, we decided that we could look further into continuous rotation of servos. The existing examples on Arduino had the knob and sweep modes for servos which we tinkered with. But students realised sooner that it would need to be adapted in order to use that program for a rotating wheel. Our current servos (9g Micro servos) were 180 degree fixed. There are online tutorials on how to open them up and convert them into a continuous rotation servo but we decided to wait for John to get us new ones.
Session 1: We finally launched our much anticipated Robotics club last Thursday. It’s an after-school club for the students of Samuel Marsden Whitby and local primary/secondary schools(which we will invite after sorting out Health and Safety requirements) to participate in teams and build robots that will culminate in challenges against each other with the aim to compete in the regional/ national robotics competitions.
It is mainly run by John Barrow, the education outreach co-ordinator at Victoria University, Wellington. Leath Powell, the mathematics teacher at school who is a ‘geek’ in the purest sense is also supporting the club and joins us for sessions. Most likely we aim to have a session each fortnight to give students enough learning that they can carry home and try it out. We provide all the resources and students are welcome to buy their own kits eventually.
These are the objectives listed out for the functioning of the club.
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- To promote the integration of science, technology, engineering and mathematics (STEM) through challenges created specifically using electronic components.
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- To develop leadership skills for students
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- To encourage students to work in teams effectively
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- To provide alternative pathways for the gifted students in the area of robotics
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- To engage students in problem solving and creative thinking
- To promote Samuel Marsden Whitby (and Victoria University) as competitive and engaging learning avenues for students thinking of higher education
Currently we have started with learning more about the Arduino. The aim will be to construct a fully functional autonomous vehicle using the Arduino and motors. We were able to get a class set of Arduino kits through the local Mana community grant.
