Robot Arm

Robot Arm is slated as a Division C national event for the 2011-2012 season, replacing Mission Possible, after being run as a Division C trial at the 2011 National Tournament. The event involves the construction of a robotic arm to grab, lift, and deposit specific items in prescribed locations. The Trial rules can be found Here

Base
In order to have a functioning Robot Arm, you'll need a base. This can be made out of any material, as long as it fits within the designated 30cmx30cm box. Something to keep in mind is that the base needs to be heavy enough to prevent the device from tipping over when the arm is moving objects around.

The base can also contain a motor used to spin the arm. One possible design of a base can be seen below:



The Arm
Due to the event being named Robot Arm, one should probably include an arm in their device. If a team wishes to get maximum points then they're arm needs to reach about 58cm(from the center if the designated arm square to the top of the bonus boxes). They really only need to reach 10-15cm outside of the base box if the operator plans on only utilizing the East and West Goals. In order to utilize the North Goal, you'll need to build with a sturdy enough material to keep the arm from breaking or flexing, while also keeping it lightweight enough for your motors to still be able to handle the load.

Your arm will most likely include a number of joints as not only will it need to lift the objects off the arena and up into boxes, but also it needs to bend up to fit inside the 30x30cm base box. Each joint will probably be controlled by a motor. It's up to you how many joints you use, though 2 on the arm and one on the "hand" should be more than enough if done properly. Keep in mind that the number of motors on your device is a tie breaker.

Motors
If you're new to robotics choosing motors can be one of the most daunting parts of the construction process as you have quite a few choices. One of the best choices for this event are servos. Servos are extremely useful in robotics. The motors are small, have built in control circuitry, and are extremely powerful for thier size. Most teams will obtain these through the VEX robotics company. While VEX has somewhat of a negative reputation with some people, there isn't really much wrong with it. Even the national trial winner in 2011 used a VEX robot.

If you're a more advanced builder you might want to look into stepper motors. A stepper motor is a brushless, electric motor that can divide a full rotation into a large number of steps. The motor's position can be controlled precisely without any feedback mechanism, as long as the motor is carefully sized to the application.

The "Hand"
The "hand" is one of the most important parts of the arm. It must also be the most versatile, as it needs to be able to grip pencils, pvc pipe, and nails in order to be a high scoring device. The rules allow for electromagnets which should prove useful for the ferromagnetic nails, so with that part down, you'll have to design a "hand" that can pick up rounded objects.

Kits
The rules state that teams can utilize kits as long as they modify them in some way. The way that you modify them is completely up to you. Here are a couple common choices for kits.


 * Lynxmotion
 * OWI
 * VEX
 * Edge
 * Lego Mindstorms

Controls
There is a wide variety of methods to controlling your arm, ranging from simple plug-and-play systems to fully automated computer control. You can also choose between wired and wireless, though in most cases wireless with be much more exspensive.

Toggle Switches
This is by far the simplest and cheapest way to make a control system. Just use switches hard wired to simple DC motors and a battery. Flip the switch to turn a motor on or off.

Remote Control
Using an RC system is usually rather simple, but can be exspensive ranging from under hundred to several hundred dollars. I suggest visiting a local hobby shop and looking for a good deal on a used system. An RC system comes with a transmitter and a receiver. You can plug a battery and servos into the receiver and use the controls on the transmitter to control the position of the servos. You can also use an Electronic Speed Control(ESC) to throttle a DC motor. The only downside to using an RC system with servos is that most limit the servo's range to 90°; some systems can be programmed to fully extend the range, usually to 180°, however these systems can cost more.

Microprocessor
The use of a microprocessor really opens of the possibilities and at around $100 isn't enormously exspensive. However to fully utilize one requires knowledge of both programming and electronics. With a microprocessor you can use a variety of input devices including joysticks, buttons, laptops and completely custom built controls. If you really wanted to be fancy you could preprogram the arm to do the event with no controls, with or without sensors to correct errors. You will need both a control board, such as the Lyxnmotion Bot Board II or the Arduino, and the actual microprocessor, such as the BASIC Atom family.

Practice/Running the event
This event is about 30% design and 70% practice. You can have an arm that could win nationals, but without practice, the design is worthless. The best way to practice is to put yourself in the situation that you would be at a competition. In order to do this you'll need an arena to practice on, printable layouts can be found here. After practicing for a while, you should develop an efficient plan for the order that you will move the objects and how you will move the objects. A finalized version of this will be part of the documentation that you will need to hand into the event director at the tournament.