2017 Leaving Certificate Project

I created this robot for the Leaving Certificate Technology course. In the issued brief we are asked to ‘...design and manufacture a model of a device, system or technological aid that could be used in a process of cleaning or maintenance in a context of your choice.’ Unlike all the other projects I have done, this one was a lot more opened ended. I wasn't given a certain competitive task to accomplish, I was just given a real world issue and told to create a device that could aid this issue. As long as my product aided in the process of cleaning and maintenance it could take any form i want it to.

In this project, the planning and designing stage took much longer than the other projects. I first had to do research on the internet to locate the specific products i wanted to replicate whilst also keeping in mind the design and manufacture limitations given my knowledge and tools at my disposal. I had to pick a product, that could be realistically made but creative enough to warrant an H1. There were many ideas i considered, that fit this criteria. Such as a automated car wash, however this was dealt too time consuming. Another idea was a car maintenance lift, however this was too uninspired. Given my experience with robotics up to this point, i thought a robot would be a suitable idea. This would lead me to choosing a robotic lawnmower as my final idea for my project.

Final Design

After much deliberation, i had decided how my robot would look and function. It will be roughly 250mm by 200mm in size. It will have a curved front to replicate many robotic lawn movers on the market. It will be created using both black and green acrylic. To move, it will have to wheels on either side of the base. Underneath the act of mowing will be simulated by two rotating blades. There will be a swivel wheel at the front of the base to assist in driving. The on/off button will be a toggle switch. Inside there will be a genie E18 board to control the motors, which in turn control the wheels and blades. At the front there will be a distance sensor, so the robot can detect obstacles and act accordingly. Lastly, there will be a speaker inside, so when the robot is lifted (to simulate theft), the LDR will detect the change in light intensity which will cause the speaker to ring out to as an alarm.

Specification

These are the criteria my robot would follow

1. My project will be a robot lawnmower.

2. I will use an electromechanical element as required.

3. I will use a GENIE E18 (used it with sumo and line follower too) motor board along with various inputs and outputs.

   1. Inputs - Distance sensor, LDR, SPST switch

   2. Outputs - Small buzzer, 3 motors

4. My project will be powered by 9V batteries

5. The main materials that I will use is 5mm green and black acrylic

Manufacture

The many pieces were designed on 2D design programme

This is just one example of pieces I designed on the 2D design program to be cut out by the CNC machine. Nearly all my pieces were cut in this way. This reduced the amount the waste produced and quicken up the manufacture of the shell of the project

The designed pieces into the CNC machine and were cut out

Once the pieces were designed they were imputed into the CNC machine, and cut out. I had to do this about 3 times as I had so many both large and small pieces to cut out in either 5mm green or black

Required holes were drilled in by the pillar drill.

Once all pieces were cut out by the CNC I drilled any holes that would be needed for switches or sensors. The larger pieces I held by hand, the smaller pieces I held in a small vice

The curved front and back panel was heater to create their curve.

I measured the black and green acrylic to their required measurements using a ruler and pen, I drilled holes in each piece that was needed for switches or sensors. I turned on the heater, allowed it to warm up and placed the pieces in it for around 10 mins or longer if necessary. Once in a flexible state I would place it over a wooden cast to create the required curve.

Sanding and filing

Sand and filing was required on all pieces to get every piece fitting together correctly, some that were too large where sanded on the belt sander, while some only needed to be filed and sanded by hand.

The shell was assembled using liquid solvent cement.

I held the pieces that needed to be glued in position, I used cramps wherever possible to hold everything steady. I added Liquid solvent cement to the edges of the pieces by a paintbrush. I continued to hold the pieces in position until they were completely glued together.

Creation of the removable panel

To access the Genie Board, batteries, and various mechanisms, I created a removable panel for easy access to them. I drilled a screw into 5mm Foamex and connected this to the top of the robot.

The wheel mechanism

This is a very simple mechanism; an inline motor is connected to each large wheel. Each wheel has a hole that the end of the motor slots into. When the motor is turned on, the wheel begins to rotate thus allowing the project to move.

The blade mechanism

This mechanism is contained in a gear box. One gear is connected directly to another inline motor, this gear powers the other two. These other two gears have a bar connected to them, with each one connected to a blade which allows it to rotate, thus simulating the movement of lawnmower blades.

Problems / Modifications

The design of the robot went through many changes. I decided on the the above model, however there was changes to be made. Even with all the planning, there was necessary changes that had to be made. For instance, my original plan was to have a swivel wheel the front of the robot. However the swivel wheel cased problems with turning so it was changed to a spherical slider. Another issue was the rotating blades, i planned on having the motors connected directly to the blades. How as this system didn't work correctly i had to construct a gear box. The gearbox contained bevel gears that inside created a more reliable rotation. As the proposed speaker couldn't be heard over the blades, i instead used a buzzer which is much louder. As the smooth wheels had problems traversing, i had to create new wheels with grooves in them, to increase grip on the synthetic grass. Lastly i had to use two pic boards in my robot, as functionality was limited with just the one board. These were necessary changes to insure my robot mower worked to its best ability.

Programming

• There will be a command, each for a different output

• Once the SPST switch is pressed, the motor will turn on and rotate the two blades underneath the robot.

• Once the switch is pressed, the robot will begin moving forward, it will keep moving forward until the distance sensor at the front of the robot notices something in its way.

• If the sensor notices something in its path it will keep turn about 160 degrees

• And move straight again, bouncing from wall to wall, in a zig zag line

• The LDR will be constantly monitoring, once the robot is lifted, to simulate theft, the LDR will detect the change in lightning and will notify the buzzer to release a sound, and the blades will stop rotating.

The explanation for the program is as follows

• The two boards are connected to one master switch, the SPST switch.

• The blades will start spinning as soon as the robot is switched on.

• The wheels will also begin to rotate, moving the robot forward

• The robot will keep going forward until the distance sensor notices an object.

• Once the object is in sight, the robot will turn 160 degrees approximately.

• If no object is in the robot’s way, it will continue driving forward thus repeating the process.

• If the robot is lifted (to simulate thief), the LDR will notice the change in light intensity.

• It will send a signal to the GENIE Board to play the buzzer, thus notifying the alerting the owner to the thief.

• It the buzzer will stop if the robot is placed back onto the ground.

Conclusion

• If you want to produce a good, fully functional project you’re going to have to put in a lot of hard work and dedication

• As Murphy's law states ‘If it can go wrong, it will’, this is true when dealing with technology, but the key is to stick with, and carry on if you want to succeed.

• Once again project management is of vital importance, if I did not have good project management when creating my project, I honestly don’t think I would have finished it in time.

• It is better to have a simple, working project than an amazing looking project that does not work.

• Always have a plan B, for everything. Things will without a doubt go wrong, in these times you must adapt to the situation and limit the amount of time you will waste fixing the problem

• It’s okay to ask for help, if you’re having persistent trouble with something, it’s okay to ask someone else for advice on how to fix the problem.

Thankfully after all the hard work I received a H1 in the subject. Getting a H1 was my aim since starting technology as a leaving cert subject in fifth year, therefore i was very happy with my result. That September i started studying Robotics and Intelligent devices in Maynooth University.

This section was heavily influenced by my Leaving Certificate report, which is listed below to provide more information.