LAB 4: MOTORS & MECHANISMS Goals - Basic knowledge of different motor types and their use - Basic knowledge of mechanisms // ACTUATORS - Mechanical device for moving or controlling something - Converts electrical signal into "motion" - I broaden the term to anything at "acts" on the world, including sound, light, motion // A few examples of sophisticated motion - 18th Century Automata . Vaucanson’s Duck . Pierre Jaquet-Droz Japanese Automata ("Karakuri") Archer Boy, Tea Serving Boy - Kinetic Art . Jean Tinguely . - Modern robotics . MTRAN 3 . Cornell Self-modeling - Thinking about Gravity / Weight / Momentum . Honda Ad "The Way Things Go" by Fischli and Weiss // MOTORS Before selecting a motor, first figure out what kind of motion is desired. There are common mechanical techniques (below) that allow motion to be converted from one type to another. Motor classification: - Direct Current (DC) - Servo - Stepper - Solenoid Motor considerations: - Voltage (all) - Amperage (all) - Torque (all) - RPM (dc) - Resolution (servo, stepper) DC - Speed . PWM to reduce voltage (reduces torque) . Gears - Control . Direction Servo - Precise position (0 - 180 degrees) through pulsing - Internal feedback mechanism - Can be converted to DC motors Servo Tutorials: Solenoid - Linear motion (push, pull) - Binary - Need gravity, spring, magnet for return - Continuous vs momentary (duty cycle) Stepper - Move one "step" at a time - Precise positioning - More wires > more difficult software Additional Actuators - Shape Memory Alloy a k a Muscle Wire - Synthetic Muscle Notes - For the small motors, the external supplies are OK - Stall current - Driving large motors (e.g. 110V), use a relay - Driving many motors (8, 16, 24, +), use a shift register // MECHANISMS Some simple machines - Lever - Pulley - Screw Gear - Ratios, reduction - Gear box necessary for DC motors for increased torque Cam - Use to produce range of subtle motion from one motor Spring - Helps to create natural motion Linkage - Used to produce organic curves and movement Converting from one type of motion to another - Cam (rotation > linear) - Worm gear (rotation > linear) - Rack-and-pinion (rotation > linear) - Piston (rotation > linear) - Ratchet (linear > rotation) // Exercises - Select a motor and write a program to control it from your Arduino board - Exercise 1 // Resources - Flying Pig - SoftIntegration - Small Parts