Something

Center of Gravity

Center of Gravity

the “average position” of all the weight on the robot

heavier objects count more than lighter ones in determining where the (____) is, and pieces that are farther out count more than pieces that are near the middle

Support Polygon

the imaginary polygon formed by connecting the points where your robot touches the ground (usually the wheels)

usually has one per robot

Stability

the robot will be most (____) when the center of gravity is centered over the support polygon

Fasteners

allow for things to be put together

the most common problem with robots that fall apart or lose pieces easily is that groups of parts are not joined securely enough and separate from each other and move around

Bracing Arms

provides support and shortens the lever

Exposure and Vulnerability

There are certain parts of a robot that are more fragile than others. Always plan the structural design to protect these parts from unwanted physical contact if possible

For the best protection ensure all robot components that can be damaged are well shielded and inside robot structure. Route wires inside the robot and away from all moving components.

Gear Ratio

a “multiplier” on torque and a “divider” on speed

(3:1) multiplies troque

(1:3) divides torque

Driven/Driving

Out/In

Mechanical Advantage

The ratio of the force a machine can exert to the amount of force that is put in. It can also be thought of as the “force multiplier” factor that a mechanical system provides

Idler Gears

inserted between the driving and driven gears

have no effect on the robot’s gear ratio

used to change the direction of spin and fill space between gears

Compound Gear Ratio

formed when you have more than one gear on the same axle

Each pair has its own gear ratio, but the pairs are connected to each other by a shared axle

calculated by multiplying the gear ratios of each of the individual gear pairs

Gear ratio with non-gear systems

(belt-and-pulley drives & chain-and-sprocket drives)

Belt or chain drives are often preferred over gears when torque is needed to be transferred over long distances.

Unlike spur gear reductions, (____) reductions do NOT reverse rotation

Wheel Sizes and Acceleration

bigger tires give you slower (_), while smaller tires give you faster ().

motor generate a spinning force which wheels convert into a pushing force

Force = Torque/Wheel Radius

Wheel Sizes and Top Speed

rolling father per rotation allows for faster (___)

Speed = Circumference * (turns/secs)

Friction

occurs everywhere two surfaces are in contact with each other

Wheel () has both positive and negative consequences for your robot. On the one hand, () between the wheel and the ground is absolutely essential in getting the robot to accelerate

Terrain

Both the size of a tire and the amount of friction it generates will be very important in ensuring that you can successfully navigate over them.

Clutches

are designed to protect the gears internal to the motor from “shock-loads”.

once it pops for the first time, it is easier for it to pop every time after that; for some robotics applications it may be necessary to regularly replace it in key areas.

ALWAYS recommended

When it pops, it is doing its job.

When it pops, it is a sign that there is something wrong with the robot design.

First Use of a Battery

remember to let them charge fully before you use them the first time because they are usually shipped uncharged

Memory Effect

refers to a mistaken belief that total battery capacity diminishes PERMANENTLY by a failure to drain the battery to ZERO voltage and then recharge it to full

does not exist in consumer devices, only in very specific laboratory conditions.

Voltage Drop

a measurable phenomenon where a battery that is repeatedly “shallow discharged” (used only part way before recharging) will start delivering lower and lower voltages, and will run out sooner

Discharge Cycles

to fix voltage drop drain/recharge and recharge the battery a few times

Overcharge

can cause permanent damage to the battery by (____)

important that you get a good NiCd charger that knows when to stop adding charge to the batteries.

Trickle Charge

a charger should switch over into (____) mode

a low current mode that can be safely applied over a long period of time to maintain a full charge, or shut off \n the charger

Temperature

Charging or draining batteries quickly will result in them heating up

Excessive heat can cause permanent damage to the battery

Do not store batteries in high temperature conditions

If batteries are hot after charging or running, let them cool down before charging or running

Age

Rechargeable NiCd batteries can be used over and over again for hundreds of battery cycles if properly maintained

HOWEVER all batteries will eventually wear out over time

Environmental Issues

The cadmium found in NiCd batteries is highly toxic, and should not be disposed of in the trash. It is illegal to do so in many countries and states.

Gravitational Potential Energy

When the water was up on top of the cliff, it had a lot of (____), energy that was stored in the water because it was high up even though gravity wanted to pull it downwards

Electrons

have negative charges, and naturally move \n toward areas with positive charges because opposite charges attract

How Batteries Flow

Tne end (the “–“ side) holds electrons at an area where they have high potential energy, just like the top of the cliff. The other side (the “+” end) is like the bottom of the cliff, an area of low potential energy that the electrons would like to travel toward.

The battery doesn’t just let the electrons travel freely from the high-energy end to the low-energy end. You need to provide a path for the electrons in order to let them get from one end to the other by connecting the battery to a circuit. The wire provides a path for electrons to get from the “–” side to the “+” side.

Batteries in Series

add battery their voltages together

how multiple AA batteries (which are 1.2-1.5V each) produce a single larger “battery pack”

Battery Cells

Individual batteries (like a single AA) are often called (____), to distinguish them from the entire “battery” pack.

Analog Sensors

can detect and communicate any value in a range of numbers

(____) = Shades of Gray and Black and White

Digital Sensor

can only detect two values, maximum and minimums

(____) = Black or White

Electromagnetic Waves

When electrons accelerate, they radiate an electromagnetic signal that moves at the speed of light. By accelerating and decelerating electrons in a controlled pattern, a wave pattern can be generated in the radiated electromagnetic field. These are called (____)

Good at carrying information quickly from one place to another

Frequency Modulation (FM)

The VEX Radio Transmitter uses an electromagnetic wave with a certain frequency to transmit data to the RF receiver module.

Is a way of encoding information in wave patterns such as these.

Frequency-Modulated Signals

The frequency of the basic wave, known as a carrier wave, is modified by combining it with another signal known as the modulating wave. This produces a final wave that looks irregular, but is really carrying the data from the signal wave on top of the carrier wave.

AM vs FM

() is less susceptible to interference than other radio transmission methods, such as amplitude modulation () or direct transmission of the signal wave.