Getting Started Guide

## Introduction

Welcome to the getting started guide for building your entry in the Robot Fighting League! This guide is designed to take you through the full process of designing, building and entering your robot into a RFL competition. For more details about a topic try clicking the links to take you the corresponding wiki page. If you have a question that's not answered here check out the forums on the RFL website or ask one of the RFL team in person at the many workshops. To find when the next workshop is check out the Facebook page

## Competition at a glance

The RFL competition pits fighting robots against each other in an arena. Each robot trying to immobilize the other competitors for 5 seconds to win.

Each robot is generally built by hand featuring cheap pre-made electronics and scavenged materials. Robots may feature an active weapon to try and damage opponent's robots.

The arena itself is a secure container for the robot's to fight in. It will feature some hazards such as pits (holes in which your robot can fall in and become immobilized) and other obstacles.

Robot's can be entered by an individual or as part of a group. We recommend groups should stay between 2 and 4 people. Because limits on venue capacity only 4 members of a team can be allowed into the workshop area on the day of the competition, the rest will gain free access to the spectator area.

In order to enter a robot you must fill out the signup form on the website here. You must also bring your robot to the preliminary inspection a week before the competition.

Robots will be charged an entry fee of £15 for non-shock soc members and £10 for shock soc members. Robots can avoid paying any fee by taking part in the documentation initiative. If the team can provides CAD files of their robot along with photos and documentation of their work (eg. meetings, photos of robot assembly, build timelapse, development blog/vlog) then the robot is deemed "documented" and doesn't pay an entry fee. This program aims to develop a catalog of robot designs to help future robot designers and to help RFL apply for funding in the future.

## Designing your robot

### Robot Introduction

Building a fighting robot can seem like a daunting task. Hence the first step is to divide up the robot's design into several sub blocks. These blocks depend on each other so will need to be designed in parallel to ensure they all work together. This guide will now go through each design block and show an image of what where it features in a simple lifter robot.

* Locomotion - How the robot moves about   The robot will need to be able to move to avoid enemy robots and to position itself for its own attacks. Drive motors need to be powerful enough to move the heavy robot over uneven terrain. Often wheels are used in a differential drive arrangement. This arrangement requires a third non driven wheel or point of contact for support.

* Offensive Measures *- Measures to immobilize other robots*   The robot will need some good offensive measures if it to perform well in the competition. Common offensive measures include: Good Pushing ability, servo lifter mechanism and rotary spinner weapon.

* Defensive Measures *- Measures to mitigate the offensive measures of other robots*    Defensive measures include things like good body strength, armour plates, self righting mechanisms.

* Body and Chassis *- Holds the robot's components together*    The body and chassis mounts all the other components to the robot and so will depend heavily what you choose in the locomotion, offensive measures and defensive measures design blocks. However a general shape or form can be decided early on eg. Wedge.

* Power *- Provides energy for the robot's active component*    The power block can only really be finalised once you know all the other components in the system. However, it also must be considered when choosing the power hungry components of your system such as motors. The power system will usually consist of a battery, DC converters (BECs) and protection elements such as fuses and switches.

* Control *- Controls the robot's functions*    The control block is again closely linked to the other components chosen in the system. Using standard RC kit allows you transmit PWM signals. Servo motors have inbuilt controllers that give positional control from these signals. Brushed and brushless motors can be controlled using an ESC which provides speed control from the these signals.

### Electronics

Electrical concepts

* Electrical Energy - Energy transmitted via move electrons through a conductor (eg A wire) often likened to water moving through a pipe
* Voltage - The pushing force applied to electrons (the pressure of water)
* Current - The rate at which the electrons are moving (the flow rate of the water)
* Power - The amount of energy present per unit time

These components are commonly found in combat robots

* DC Electrical Motors - Use electricity to make rotary motion
	+ Brushed - simple, cheap, often with gearbox meaning high turning force (torque) lower speed
	+ Brushless - more complex, more expensive, higher efficiency, higher power for size, often without gearbox meaning higher speed less turning force
	+ Servos - Allows positional control, contain gearbox for high torque, have in built controller
* RC radio kit - Transmit control signals wirelessly
	+ Transmitters - A remote control that broadcasts signals
	+ Receiver - Receives signals from transmitter and sends them to other components
	+ ESCs - Take signals from Receiver and drives motors
* Power Equipment
	+ Li-Po Battery - A rechargeable powerful and cheap battery common in hobbiest remote control vehicles
	+ Fuse - A device which stops current flowing is exceeds it a certain level (its current rating)

## Design stages

Before beginning any design work it would be a good idea to familiarise yourself with the rules. Your robot will not be able to take part in the competition is it violates these. You should also check your design against the rules regularly.

### Conceptual Design

The first thing is to quickly establish a concept of your robot. You will need to decide what the active weapon of your robot is going to be. Conventional weapons include:

* Pushers - Easy
* Lifters (using servo) - Medium
* Spinners - Hard

You also need to decide on a drive scheme, the most common is differential drive.

The other thing to think about is the shape of your robot, you will need to ensure that this shape can reasonably be expected to fit in all the other components of your robot.

This gives you a conceptual design of your robot. The next step is to do the detailed design of how exactly everything will fit together.

### Detailed design

Detailed design consists of picking exactly what you are going to use and ensuring it all works together. The first step is choosing all your electrical components. RFL also has a couple of components that can be borrowed for the duration of the competition as well as some which can be purchased. Full details can be found here.

When picking electrical components it's important to ensure that they're compatible with each other. You should check that your chosen ESC is rated well above your motor's maximum current (stall current). Additionally you should also check that the overall current drawn by the circuit does not exceed your batteries maximum discharge current (30-52A if you're borrowing a battery). Another power issue can be caused by the BECs built into the ESCs in your circuit not having enough current to power servos, this can be addressed using a dedicated power circuit (probably an s-bec).

#### Bill of Materials for Lifter robot

##### Borrowing parts (these parts are available to borrow RFL for free for the competition)

+ Reciever
LiPo battery

Once you know what you are using then you should order your electronic parts immediately so they arrive in time (check your delivery dates if ordering from overseas). You can then begin designing the body and chassis to mount your components. This is a design you will have physically make so make sure you consider how everything is going to fit together and how strong each fixing or joining method you use will be.

Often people lasercut parts. These parts are designed in software (using a CAD package such as Solidworks) and then exported in .dxf format to be printed. When doing this you need to ensure you allow for clearance on all holes by adding 0.2mm. For more details visit the laser cutting page.

Another common method of creating your chassis uses a more DIY *bodge* approach. Components can be attached to an existing structure such as a tupperware box or block of wood.

Once your electronic components arrive, connect them together to test they all work. Then mount them to your constructed frame and test the components again (do not attach spinners or other weapons when testing outside the arena). If you have any extra time before the event you can use this time to modify your robot if you spot any issues. Its also a great time to pimp your robot.

Finally you must show your assembled robot at the preliminary inspection a week before the event. Then look forward to the competition to see how your design fare in the ARENA OF HONOR.

## Conclusion and next steps

Hopefully this guide has given a feel for what will go into designing and building your combat robot. Here's a final few tips to give you best chance of success in your death machine design endeavours.

* Fill out the signup form on the RFL website to enter the competition.
* Follow the RFL page and join the RFL competitors group to keep fully informed on workshops, rule changes and announcements.
* Read the robot design rules
* Explore the rest of this wiki for more useful resources including the recommended parts list.
* In terms of designing your robot the most urgent thing to do is to choose and order components. A rough timeplan for making your robot is shown below.