Automated Precision Machines

Team 2Nicholas Neumann

Ralph PrewettJonathan Brouker

Li TianFelix Adisaputra

November 5th, 2010

Contents

Servo Motor Stepper Motor Sensors for Precision Control Robotic Programming Languages Automated Machines

What is a Servo Motor?

• Closed-Loop System• Precise position control

Servo Motor

Servo Mechanism 1 : Position Sensor 2: Electric Motor 3: Reduction Gears

Servo Motor

Closed-Loop System

Servo Motor

Example No Control No Feedbacks

Servo Motor

Proportional-Integral-Derivative Control

Overshoot = 0 Rise Time Settling Time Steady-State Error = 0

Servo Motor

Applications Labelling

Machine

Stepper Motor

• Brushless, Synchronous Electric Motor

• Open-Loop System(No Feedback)• Full Rotation Divided into

Large Number of Steps• Torque Decreases as

Speed Increases.

Stepper Motor Permanent Magnet Stepper Motor

• “Tin-Can” or “Canstock”• Low Cost• Low Resolution• 7.5o to 15o step angles• 48-24 steps/revolution

• Rotor Magnetized with Alternating Poles

• More Magnetic Flux Provides More Torque

Stepper Motor Hybrid Stepper Motor

More Expensive Better Performance

• Torque• Speed

Higher Resolution• 3.6o to 0.9o step angles• 100-400

steps/revolution

Rotor• Multi-Toothed• Axially Magnetized

Concentric Magnet

Stepper Motor

Two-Phase Stepper Motor Bipolar Drive

• Single Winding per Phase• Half the Power Loss

Unipolar Drive• Two Windings per Phase• One for Each Magnetic Field

Direction• Fewer Switches

Stepper Motor

Applications Film-Advance

Stepper Motor

Applications Conveyor

Servo Motor vs Stepper MotorServo Motor Stepper Motor

Drive Circuit Complicated. Difficult for user to fabricate it.

Simple. User can fabricate it.

Noise and Vibration Very little Significant

Speed Faster (3000-5000rpm max.) Slow (1000-2000rpm max.)

Out-of-Step Condition Not Possible (Heavy load Still Run)

Possible (Heavy load Stop)

Control Method Closed-Loop (uses an encoder) Open-Loop (no encoder)

Resolution

ppr = pulses per revolution

0.36° (1,000 ppr) to0.036° (10,000 ppr)

2-phase PM model: 7.5° (48 ppr)2-phase HB model: 1.8° (200 ppr) or 0.9° (400ppr)5-phase HB model: 0.72° (500 ppr) or 0.36°(1,000 ppr)

Sensors for Precision Control

Hall Effect Sensor Voltage Transducer Response to Changes in

Magnetic Field Applications:

• Switching, Positioning, Speed Detection, Current Sensing

Sensors for Precision Control

Advantage:They are immune to dirt, dust and water, They are capable of switching at high frequencies.They can be used for a wide variety of applications.

Sensors for Precision Control

Rotary Potentiometer Position Transducer Three-Terminal Resistor Adjustable Voltage Divider

Sensors for Precision Control

Potentiometer

If RL >> (R1 and R2),

Sensors for Precision Control

Linear Potentiometer Displacement Transducer Voltage Division

• Hybrid Conductive Film

Sensors for Precision Control

Rotary Encoder Electromechanical Device Angle Transducer Angular Position

Analog/Digital Code Types:

• Absolute Rotary Encoder• Incremental Rotary Encoder

Gray Code

Sensors for Precision Control

Rotary Encoder Gray Code

Robotic Programming Languages C Language

Pros:• Speed of Resulting Application• Application in Firmware

Programming• Compatible with Many Other

Languages• Code is Compacted into

Executable Instruction

Cons:• No Runtime Checking• No Strict Type Checking

– Can Pass Integer Value for Floating Data Type• Very Difficult to Fix Bugs as Program Extends

Robotic Programming Languages RobotC Language

Pros:• More Functions than Regular Graphical Language• Easy to Navigate Through Program• Suitable for More Complicated Programs

Cons:• Text-Based Language

– Hard for Beginners• Must be Bought Separately

from Kit

Robotic Programming Languages Ladder Logic

Pros:• Familiar Programming Language

– Relay Logic (Widely Used)• Cost-Effective Equipment• Reliable Parts

– Simple Circuits

Cons:• Difficult Integration with Third Party Software

BASIC Pros:

• User Friendly and Interactive• Simple and Easy• Rapid Development• Powerful Front-End Tool• Multiple Vendor Support

Cons:• Memory Leakage• Passing Value by Reference• Only for Windows• Sluggish Performance

Robotic Programming Languages

Robotic Programming Languages LabVIEW

Pros:• User Friendly Graphical Interface• Universal Platform for Numerous

Applications• Compatible with Other Languages• Execution Highlighting Feature

Cons:• Expandability Problem

– Depends on How Well the Original Program was Written• Memory Management

– Difficult Memory Allocation• Expensive

Robotic Programming Languages LEGO Mindstroms NXT

Pros:• Icon-Based Drag and Drop

– Graphical Language• Easy Maintenance

– Simple Programs

Cons:• Lack of Complex Features in the Compiler

Which Language to pick? Previous Experience How much time and effort you intend to invest Your goals Availability

Robotic Programming Languages

Automated Machines

Control Systems Information Technologies

Reduce Human Work

Automated Machines

Programmable Logic Controller (PLC) Digital Computer Automation of

Electromechanical Processes Multiple Input-Output

Arrangements Armored for Severe

Conditions User Interface

Automated Machines

Supervisory Control and Data Acquisition (SCADA)

• Centralized Systems• Monitor and

Control

• Human-Machine Interface (HMI)• Alarm Conditions

Automated Machines

Main Advantages Replacing Human Operators in Monotonous

Work Performing Tasks that are Beyond Human

Capabilities• Size, Weight, Speed

Dangerous Environment• Space, Underwater, Nuclear Facilities

Economy Improvement

Automated Machines

Main Disadvantages Technology Limits

• Unable to Automate All Desired Tasks

High Initial Cost Unpredictable Development Costs

Questions