Different Types of Robots Robot Arms (Fixed Robots) Mobile Robots Humanoid Robots Legged Robots Wheel Robots 3 wheels 2 Driver wheels, 1 Caster 1 Driver wheel, 2 Casters 4 wheels Casters make diverse problems in the control of the robot

Wheel Robot Main Components Mechanics Wheels Driver Motor (s) Power Transmission System Electronics Controller Board Needing feedback from environment Sensors We are now discussing some of the above topics

Different Types of Motors DC Motors You can simply control it AC Motors It’s difficult to be controlled but it can be used in high power applications Servo Motors You have complete control on the shaft angle

Different Types of Feed Back Sensors IR Sensors Pressure Sensors Light Sensors Temperature Sensors Encoder

What is Encoder

Why do we use Power Transmission Systems? To reduce Angular Velocity To increase Torque P = (T . w) = cte. Different Transmission Systems Gear Hard manufacturing and adjustment Pulley So w => T

Gear Gears are used to change the speed and force of the motor. You can use gears to: Speed up or slow down your robot. Make your robot stronger or weaker. There are many different types of gears Spur Gear Bevel Gear Worm Gear Rack & Pinion

Gear Spur gears are wheels with teeth

Gear Bevel gears mesh at right angles, so they change the direction of rotation.

Gear Worm gears look like screws. They have many special properties.

Gear Rack & pinion gears turn rotational motion into straight-line motion.                                   

Where does all this “torque” come from? Consider a pair of gears that are meshed together. F A torque on this axle... t …produces a force at the tooth. r The moment arm is the radius of the gear. Remember: t = F x r

The force from the small gear’s tooth pushes against the large gear’s tooth. This creates an equal (and opposite) force in the large gear. This is Newton’s 3rd Law. F …and produces a larger torque on this axle. r t The force acts through this larger moment arm...

Analyzing the forces... t1 = F1 x r1 t2 = F2 x r2 F1 = t1 / r1 F2 = t2 / r2 F1 = - F2 t1 / r1 = -t2 / r2 -t2 / t1 = r2 / r1 F1 = -F2 t2 r2 t1 r1 The ratio of torques is the ratio of the gear radii. This is the gear ratio!

Idler Gear An idler gear is a gear that is inserted between two other gears. Idler gears do not affect the gear ratio between the input and output gears. The gear ratio would be computed just the same if there were no idler gear.

Idler Gear Recall that when using spur gears, the output axle rotates in the opposite direction as the input axle. You can also use idler gears to change the spacing between the input and output axles Remember, idler gears do not change the gear ratio

Gear The gear ratio of this gear box is 75 to 1 That means the last axle rotates 75 times slower than the first axle. It also means the last axle has 75 times the torque as the first axle.

Try this experiment. Have one person turn this wheel. And have another person try to hold on to this wheel.

Gears can increase the torque (and force) that they exert on something. This is known as mechanical advantage. torque increases BUT, it comes at a price. Do you know what it is?

Belt Drives Uses friction to transmit power Velocity Ratio: 2 1 C w2 w1 D2 D1 Velocity Ratio: D1.w1=D2.w2

Belt Drive Basics DR DN Size Size Center Distance Motor Nameplate (center shaft to center shaft) Shaft Size for DR, can use NEMA frame Motor Nameplate Take-up/Installation Allowance

Ratio always greater than 1 Belt Drive Basics Speed Ratio = 2.5 R N Speed-Up Speed-Down 10” 1750 rpm 4” 700 rpm 4375 rpm Ratio always greater than 1

How to assemble our Robot Here is our package

How to assemble our Robot 1 2 3

How to assemble our Robot Bottom view of the robot

How to assemble our Robot Sensor board assembly

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