ME 4135 – Robotics and ControlAn Introduction

Dr. Richard Lindeke203 Engineering Building

726-7947; rlindek1@d.umn.edu

Contact Details

• Course Website: http://www.d.umn.edu/~rlindek1/ME4135_11/CoverPage.htm

• Office Hours: 11:30 – 12:30 MWF

• Tentative Exam Dates:– Midtern 1: Monday 8 Oct– Midterm 2: Friday 16 Nov– Final: Wednesday Dec 19 (12 N – 1:55P)

Outline Some General Thoughts Production Systems & the “Tenets of Automation”

Pose Control – Fixed Vs Flexible Automation System Synchronization System Balance

The “Problems of Robotics”

The Robot is a System – by definition! Manipulator Power System Controller Schemes End of Arm Tooling Sensors (environmental)

Just Consider This:Thank goodness robots are now at the point where using them is nearly the business equivalent of upgrading from a typewriter to a personal computer. Price has virtually been eliminated from the cost justification exercise. Today you get so much value in terms of software and technology, reliability and accuracy, that robots are affordable at any size.

Just as Joe Engelberger, the ‘‘Father of Robotics,’‘ has said so many times – when looking at solving manufacturing problems, ask the question: ‘‘Do you think a robot could …?’‘ It was a good question 40 years ago, and even better today with all the new technology.

Just Consider This Some Applications: (from The British Automation & Robot Association)

Search by [Automation/Robot] Application Area: Arc / Gas / Laser / Spot Welding Assembling Bio-Chemistry and Hazardous Applications Cutting / Grinding / Polishing Dispensing / Painting / Sealing / Spraying Handling Operations / Machine Tending / Moulding Inspection / Measurement / Testing Laser / Water Jet Cutting Loading / Unloading Packaging / Palletizing Search by [User] Industry: Aerospace Agriculture / Hunting / Forestry / Fishing Basic Metals / Fabricated Metal Products Beverages / Food / Tobacco Products Ceramics Chemicals / Fuels Clocks / Medical / Optical / Precision / Watches Communications / Radio / Television Computing / Electronics / Software Construction Cork / Wood (excluding furniture) Education Electric / Gas / Water Supply Furniture Minerals (non-metallic) Mining / Quarrying Motor Vehicles Paper / Printing / Publishing / Recorded Media Pharmaceuticals Plastic / Rubber Research & Development Textiles

North American Robotics Industry Posts Best Quarter Ever, According to New Statistics from RIAAnn Arbor, Michigan – North American robotics companies sold more industrial robots in the second quarter of 2012 than any previous quarter in history, according to new statistics released by Robotic Industries Association (RIA), the industry’s trade group.A total of 5,556 robots valued at $403.1 million were sold to North American companies, a jump of 14% in units and 28% in dollars over the same quarter in 2011. Orders in the first half of 2012 totaled 10,652 robots valued at $747 million, increases of 20% in units and 29% in dollars over the same period last year.

From: Robotic Industries Association (Posted 07/30/2012)

Orders for spot welding robots, used primarily in automotive solutions, jumped 68% in the first half of 2012. Other big jumps were seen in coating & dispensing (+42%), arc welding (+20%), and assembly (+19%). Material removal orders, a smaller application area, rose 364 percent.

Automotive related orders accounted for 65% of units and 64% of dollars in the first half of 2012. This represents sharp gains of 44% in units and 56% in dollars over the opening half of 2011.

From: Robotic Industries Association (Posted 07/30/2012)

RIA estimates that some 220,000 industrial robots are now used in the United States, placing the United States second only to Japan in overall robot use. More than one million industrial robots are used worldwide.

U.S.A.’s Robotic Usage

With So many Robots in Use, we need effective Project Management for Automated Systems

Defining Automation:–Automation is the technology concerned

with the application of complex mechanical, electronic and computer-based (computer-controlled) systems to the operation and control of production

Automation includes:– Automatic Machine Tools, Forges and Molders for

workpiece processing (CNC & DNC)– Material Handling Equipment (ASRS’s, AGV’s, Reactive

Conveyors)– Automated Assembly Machines– Feedback Control Systems/System Sensors– Process Controllers (PLC’s)– Automated Data Collection Systems (AIDC)– Automated Data Reporting Systems (MRP)

What to consider

The development of an Automated System is a 4 step process:– System problem analysis for overall needs–Determination of special needs–Design of control hierarchy–Building/programming of individual

components

Some General Thoughts on Working Intelligently with a Production System

Does Variety (types) or Piece Count (volume) dominate?• Consider Fixed Automation vs. Flexible Automation

Should we Consider Humans?• Typically, making it easier for automation makes it easier

for humans (especially true for assembly)Cost Justification of the system• Productivity Gains• Labor Replacement• Improved Quality, Repeatability & Reliability• Increased Production Capabilities• Quicker Changeovers

Project Management for Automated Systems – what to consider

Quantify Overall System Needs:– Number of Parts per hour (Production Rate!)– Product Variety– Part Size – Part Shape – Part Weight, etc

STEP 1

Project Management for Automated Systems – what to consider

Find Special Needs:–Robot Tooling and Machine Fixturing– Sensors for Pose Control or Decision-making–Communication Requirements (Machine to

Machine)

STEP 2

Project Management for Automated Systems – what to consider

Determine Control Hierarchy:– Isolated Actions– Master/Slave(s)– Event Driven Response – under higher or parallel

control

STEP 3

Project Management for Automated Systems – Final Actions

Build and/or Program Individual Units:– Robot Path Control– Machine Tool Codes– AGV Paths/Controls– ASRS Designs/Controls– Communication Network– Relays/Sensors, etc.

STEP 4:

“Tenets of Automation” – Or what must be ASSURED when Machines replace Humans

Pose Control: is a principle that states that each degree of freedom of a machine, tool, product or process must be fully known or accounted for at all times for the (high quality) production systems to operate.

Degree of Freedom is (in this physical sense): – a set of positional bits (X, Y or Z) – a set of Rotational bits (Roll, Pitch or Yaw)– Full POSE Control Requires 6 dof from the machine!

“Tenets of Automation”

• System Synchronization (timing control) of operations must be maintained: – this requires that the sequence and timing of

each movement during the process activity must be known and controlled. – This includes part counting, machine and

product arrivals and departures, completed and closed communication sequences, etc.

“Tenets of Automation”• System Balance: – Each step in a process must be

appropriately sized to complete its tasks within the overall system processing requirements. – Thus, no process should be slower/smaller

(or faster/larger) than its predecessor or followers without accounting for product accumulation within the system.

Achieving Automation – Fixed vs Flexible

• In Fixed Automation Systems – POSE CONTROL is imposed by stops, cams,

rotators, etc– SYNCHRONIZATION is controller by in-feed supply,

part feeders, hoppers, pallet movers, etc– BALANCE is controlled by (Overall System) design

Achieving Automation – Fixed vs Flexible

• In Flexible Automation Systems– POSE CONTROL is achieve by sensing and

adaptation by the machines and product in the system

– SYNCHRONIZATION is by adapting to the changing needs of the feed stock and throughput demand

– BALANCE is by design over extended time horizon, machines can be reprogrammed (on-line in Real Time) for changing part mix

What Are the “BIG Problems” for a robot engineer

• Where Am I (Now)– This is the Forward Kinematics Problem

• Where Am I going– This is a Forward/Inverse Kinematics Problem

• How will I get there– This is a combination of the two needs:• Path Planning• Force/Torque Kinetics and (Servo) Control

The Robot System Contains 5 Major Sub-systems

• Manipulator• Power System• Control• End-of-Arm Tooling• Environmental Sensors

The Robot System

• The Manipulator – includes an Arm part and a Wrist part– consists of joints (revolute or prismatic), actuators,

and kinesthetic (positional) sensors– Arm Types: • Cartesian• Cylindrical• Spherical• SCARA (selectively compliant assembly robots)

• Articulating Arms

Cartesian Types (PPP)

X0Y0 Z0

J1

J2J3

Gantry Type

Cantilevered Type

Cylindrical Types (RPP or PRP)

P-R-P//R-P-P

Configuration

Spherical Types (RRP)

R

X0

Y0

Z0

Articulating Type (RRR)

3

1

2

L2

L1

Z0

X0Y0

SCARA Type (RRRP)

Manipulator Wrists

Spherical and/or RPY variants -- Idealized

…To Practical Realizations of 3 dof

Wrists

The Robot System

• The Power Systems– Pneumatic for light loads at elevated speed– Hydraulic for heavy loads or very high speeds– Electric Servo for general applications

The Robot System

• The Controllers– Bang-Bang: are mechanically programmed (movement to stops) and

usually one-axis-at-a-time

– Point-to-point servo: feedback of joints positions as moves from point A to B are run – no control of the path between A and B only end points are assured

– Servo w/ Path Control: the motion is controlled completely between point pairs including positions and orientation to follow desired space curves

– Autonomous Control: Device control that allows paths to be determined in ‘real time’ as the devices moves and interprets various sets of sensory inputs to create ‘intelligent’ paths as it moves

The Robot System

• The End of Arm Tooling -- their complexity of task dictates the type of control scheme that is required– Grippers/Hands/spot welders– Sensor Arrays (static reading)– Sensors (active scanning)– Ladle/Hooks– Routers/Grinders/Drills– Spray Guns/Torches

The Robot System

• Environmental Sensors – devices that give higher level information for

program control and or path planning

• Thus, Robots are Systems requiring design choices at 5.2 levels!