Microprocessor and Microcontroller Based Systems Instructor: Eng.Moayed N. EL Mobaied The Islamic University of Gaza Faculty of Engineering Electrical Engineering Department بسم الله الرحمن الرحيم EELE 4315 — Fall 2010 Lecture 15

In this lecture we will present: Actuators types Control method for:  DC motor  AC motor  Stepper motor  Servos motor Actuators are used in order to produce mechanical movement in robots. Actuators for Robots

Actuator Types

Electrical Actuator

DC Motor

AC Motor

Stepper Motor

Servos Motor

Hydraulic Actuators

Pneumatic Actuators

Other Actuators

Controller H-bridge PWM control DC motor control

DC motors only have two leads. The direction it spins is determined by which terminal has power applied and which is connected to ground. An H-bridge consists of four switches (in our case BJTs) and depending on which two are closed, allow the motor to operate in either direction We chose to use an L298 chip from STMicroelectronics because it has two H-bridges in one package. H-Bridge

DC motor control PWM control A pulse-width modulated signal is a rectangular waveform with a varying duty cycle. A longer duty cycle means the voltage is on for longer and the average voltage applied to the motor is higher and vice versa. Will be implemented using the PWM generator on our microcontroller.

Pulse-Width Modulation

Stepper Motor (uni-polar)

Stepper Motor Stepping Sequences for Single Coil Excitation Only one coil is active at a given instant of time

Stepper Motor Single Coil Excitation

Stepper Motor (Single Coil Excitation)

Stepping Sequences for Double Coil Excitation Two coils active at any given instant of time Stepper Motor (Double Coil Excitation)

Stepper Motor (Driver circuit)

Stepper Motor (sequence)

Servos motor

lDo not confuse “servos” with “servo motors”

Servos Motor

Motors and Encoders

Feedback measurement “optical encoder” Relative position - direction - resolution grating light emitter light sensor decode circuitry

Ideal mask/diffuser grating light emitter light sensor decode circuitry Real A diffuser tends to smooth these signals Optical Encoders

Relative position - direction - resolution grating light emitter light sensor decode circuitry Optical Encoders

Relative position - direction - resolution grating light emitter light sensor decode circuitry A B A B A lags B Optical Encoders

Relative position - direction - resolution grating light emitter light sensor decode circuitry A B A leads B Phase lag between A and B is 90 degree Optical Encoders

Design # 1 ( Stepper motor) Design problems Design controller for stepper motor  Switch for on/off  Switch for right/left rotation with single coil excitation method.  Switch for right/left rotation with double coil excitation method.  Switch for speed (1,2) selection.