Chapter 5Work Cell Design and Control

Contents

• Robot Cell Layouts

• Multiple Robots and Machine Interface

• Some Consideration in Work Cell Design

• Interlocks, Error Detection and Recovery

• Robot Cycle Time Analysis

Introduction

Step of a company to implement a roboticsprogram in its operation:• Initial familiarization with the technology• Plant survey to identical potential applications• Selection of application• Selection of the robot• Detailed economic analysis & capital

authorization

Robot work cell layout

• Robot-centred work cell

• In-line robot work cell

• Mobile work cell

Robot-centred work cell

• Center of work cell• High utilization of robot• Method of work part

delivery (eg: conveyor, part-feeders, pallets)

• Install for single robot servicing 1@more production machines

In-line robot work cell

• 1 @ more robots located along in-line conveyor

• Work is organized so each robot performs assembly operation on each part (eg: welding line)

Mobile work cell

Mobile work cell

• Transport mechanism: floor mounted @ overhead railing system

• Service for more than one station

• Problem: to find optimum number of station to service

Multiple Robots and Machine Interface

• Physical Interference of Robots

• Machine Interference

Some Modification in Work Cell Design

• Modification to other equipment in the cell• Part position and orientation• Part identification problem• Protect of robot from its environment• Utilities• Control of work cell• Safety

Work cell control

• Sequence control

• Operator interface

• Safety monitoring

Sequence control

Sequence control includes:

• Regulate the sequence of activities

• Control of simultaneous activities

• Making decision to proceed/stop/delay work based on events

Operator Interface

Operator to interact with robot work cell.

Operator interface is required to:• Program the robot, modify and update programs• Let human operator participate in work cycle• Do data entry by human operator• Do emergency stopping activities

Interlock

Error Detection and Recovery

When a computer is used to detect and

correct errors, this is known as “error

detection and recovery”

Error Recovery

Error Recovery

Robot Cycle Time Analysis

Robot Cycle Time Analysis

Robot Cycle Time Analysis

Robot arc welding

• Robot welding means welding that is performed and controlled by robotic equipment.

• In general equipment for automatic arc welding is designed differently from that used for manual arc welding.

• Automatic arc welding normally involves high duty cycles, and the welding equipment must be able to operate under those conditions.

• In addition, the equipment components must have the necessary features and controls to interface with the main control system. 

• A special kind of electrical power is required to make an arc weld. The special power is provided by a welding machine, also known as a power source.

• All arc welding processes use an arc welding gun or torch to transmit welding current from a welding cable to the electrode. They also provide for shielding the weld area from the atmosphere. 

• The nozzle of the torch is close to the arc and will gradually pick up spatter. A torch cleaner (normally automatic) is often used in robot arc welding systems to remove the spatter.

• All of the continous electrode wire arc processes require an electrode feeder to feed the consumable electrode wire into the arc.   

• Welding fixtures and work piece manipulators hold and position parts to ensure precise welding by the robot.

• The productivity of the robot welding cell is speeded up by having an automatically rotating or switching fixture, so that the operator can be fixing one set of parts while the robot is welding another.

• To be able to guarantee that the electrode tip and the tool frame are accurately known with respect to each other,

• the calibration process of  the TCP (Tool Center Point) is important. An automatic TCP calibration device facilitates this time consuming task .

Robot spot welding

• Automatic welding imposes specific demands on resistance welding equipment. Often, equipment must be specially designed and welding procedures developed to meet robot welding requirements. 

• The spot welding robot is the most imortant component of a robotized spotwelding installation.

• Welding robots are available in various sizes, rated by payload capacity and reach.

• Robots are also classified by the number of axes. 

• A spot welding gun  applies appropriate pressure and current to the sheets to be welded.

• There are different types of welding guns, used for different applications, available.  An automatic   weld-timer initiates and times the duration of current.    

Robot spot welding

• During the resistance welding process the welding electrodes are exposed to severe heat and pressure.

• In time, these factors begin to deform (mushroom) the electrodes. To restore the shape of the electrodes, an automatic tip-dresser is used. 

• One problem when welding with robots is that the cables and hoses used for current and air etc. tend to limit the capacity of movement of the robot wrist.

• A solution to this problem is the swivel, which permits passage of compressed air, cooling water, electric current and signals within a single rotating unit.

• The swivel unit also enables off-line programming as all cables and hoses can be routed along defined paths of the robot arm.

Military Applications• DARPA Programs:(Defense Advanced Research Projects Agency)

Tactical Mobile Robotics

Robot Applications• Fire Fighting, Search and Rescue

Robot Applications

NASA/DARPA Robonaut project: a humanoid robot that can function as an astronaut equivalent for spacewalks. Human operators on earth can control the robot’s movements from distance. Website: http://vesuvius.jsc.nasa.gov/er_er/html/robonaut/robonaut.html

• Space Robotics:

Mars Exploration Rovers: Spirit and Opportunity --- twin robot geologists,

landed on Mars: Jan 3, and Jan 24, 2004, and still alive, today in 2006!

Website: http://marsrovers.jpl.nasa.gov/overview/

Robot Applications• Robots for Assistive Technology

Robot Applications• Entertainment Industry

Robot Applications• Entertainment Robots

Sony-Qrio

Personal Robot?

• Just as the personal computer is used for automated information management even in households, robots can be used to execute domestic tasks.

• Manipulation of bits of information (PC)• Manipulation of physical objects (PR)

http://www.personalrobots.com

Architecture of Robotic Systems• Mechanical Structure

– Kinematics model– Dynamics model

• Actuators: Electrical, Hydraulic, Pneumatic, Artificial Muscle • Computation and controllers• Sensors• Communications• User interface• Power conversion unit

Environmentalsensors

Motion planner Controller

MechanicalStructure

Configuration sensor

INDUSTRIAL APPLICATION

Gantry Robots• gantry robot systems are used in large work

envelope environments with significant system integration tasks.

• Examples of delivered projects include systems for spent nuclear fuel handling, automated calorimetric, special nuclear material storage and retrieval, deployment of manipulator systems,

• deployment of process tools such as TRU Waste Box opening saws and in-process handling of chemical munitions in demilitarization processes..

• Deployment of large payloads is enabled by PaR Systems' patented telescoping tube technology.

• Telescoping tube systems motion is based on linear bearing technology.

• We have delivered hundreds of telescoping tube systems that offer payload capability exceeding 6,000 pounds (2,700 kg) and the rigidity to deliver a payload to very fine positional tolerance.

• Many telescoping tube sets are provided with over 40 feet (over 12 meters) of vertical motion.

Nuclear fuel handling

• Recent delivered integrated solutions include spent nuclear fuel handling, plasma arc, water jet size reduction systems, and buried TRU waste box opening.

• In each case, PaR Systems provided the right combination of automated and remotely operated features, with automated end effectors changing, computer based operations control and advanced operator interfaces.

• For Spent Nuclear Fuel and other high level handling, we provide varying degrees of remote maintainability as well as deployment system retrievability.

Manipulators

• PaR Systems' manipulator systems have served the nuclear industry hot cell operators worldwide since the early 1960s.

• "It's a PaR" is generic terminology for a remotely operated manipulator system.

• The PaR Systems M3000 and M6000 are simple rugged manipulator arms with payloads up to 400 pounds (181 kg.).

• Applications range from hot cell utility and process operation to retrieval and waste packaging.

• Deployment is mainly by overhead mounting or wall mounting of transporters. Other options are vehicle and pedestal mounting.

Integration of Fanuc© Robotic Equipment

MULTIMOVE

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