Electric Motors
Real Time Embedded Systems www.atomicrhubarb.com/embedded Lecture 1 January 17, 2012 Topic
Warning! This is a work in progress. Watch out for sharp corners and slippery surfaces
Motors CSCI 190.80/297.80 Real Time Embedded Systems George Washington University Spring 2010 www.atomicrhubarb.com/embeddedsy stems
Motors Inductors Inductors make relays, motors, Basic Motor
Motors
Motor Types Types of motors DC Servo Stepper Others that we are not going to talk about...
Inside a DC motor
Inside a real DC motor
Whats that coil thing?
Inductor
Inductors
Inductors Make... Electromagnet Relay
and... Transformer Solenoid
Electro Magnetic Field
Input Protection
Input Protection
Some words/terms Torque Speed Power Torque/Speed curve Power curve
Torque F τ = F r r Torque A force to produce a rotation. A twisting force. SI units = N m, English units = inch-pounds, foot-pounds
Angular Velocity ω r V tangential = r ω Angular velocity Rate of rotation around an axis. In radians/second or rotations/minute.
Power Power Rate at which work is done or energy is emitted/transferred. SI units = Watts (1 watt = 1 N*m/s). English units = Horsepower or footpound/second. P = τ ω
Torque/Speed
Torque/Speed curve Mostly linear τ motor = τ s - ωt s /ω n ω motor = (τ s t s ) ω n /t s
Recall P = τ ω Area of rectangle under curve is power Max Power P max = ½τ s ½ω n Power Curve
Power curve We know P = τ ω τ motor = τ s - ωt s /ω n ω motor = (τ s t s ) ω n /t s So P motor (ω) = -(τ s /ω n )ω 2 + τ s ω P motor (τ) = -(ω n /τ s )τ 2 + ω n τ
Power Curve
Torque Pull-Out Torque - The largest torque under which a motor can operate without sharply losing speed. Pull-In Torque - The largest steady torque with which a motor will attain normal speed after accelerating from a standstill.
DC Motors To to control them Use a transistor (for low DC voltages) Power Mosfets How to reverse How to vary speed (PWM) Assorted circuits Transistors H-bridge
Some DC motors
DC Motor Speed Contol
Simple DC motor driver
Power MOSFETs
?
Driving Loads
DC Motor Speed Control
DC Motor Speed Control
DC Motor Direction Control
DC Motor Direction Control
DC Motor Direction Control
DC Motor Direction Control
DC Motor Speed & Direction
DC Motor Speed & Direction
Servo Motors How they work How to control them 555, uc, servo controller No H-Bridge needed
Servo Motor
Servo Control
Some ready-made drivers Servo Pololu Others Directly from a z8 Can a java microcontroller control a servo?
Stepper Motors Unipolar Bipolar Variable Reluctance Bifilar We consider Unipolar and Bipolar A look inside, how they work
Variable Reluctance Motor
Variable Reluctance Motor
Unipolar Stepper Motor
Unipolar Stepper Motor
Bipolar Stepper Motor
Bipolar Stepper Motor
Universal Stepper Motor
Universal Stepper Motor
Stepper Motors
Stepper Motor Control
How do you drive a stepper motor (what hardware)?
Dual H-Bridge
More on Steppers Setpping Half-stepping Microstepping Friction, Dead zone, Dynamics - holding torque, running torque
Unipolar Stepper Motor
Still More Control circuits Power transistor Darlington pair H-Bridge (the real answer)
Real Motor Spec
Another
Some ready-made drivers Stepper Pololu Jameco H-bridges Whats in a stepper driver board and why?
An Example
Motor Coupling
Special Motors Threaded shaft Linear motors Solenoids Muscle Wire
Linear Stepper
Threaded Shaft
Muscle Wire muscle wire A shape memory alloy (smart metal, memory metal, memory alloy, smart alloy) is an alloy that "remembers" its original, cold-forged shape: returning the pre-deformed shape by heating.
Solenoid
Measuring Motor Speed or position DC Stepper
Sensing Motor Position Optical Hall-effect
Questions?
Motor Example Example_ StepperMotor Demonstrate how to control a simple stepper motor
References http://en.wikibooks.org/wiki/practical _Electronics/Stepper_Motors