ROBOT SAFETY

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ROBOT SAFETY

• OBJECTIVES
• BE ACQUAINTED WITH ROBOITIC SAFETY.
• UNDERSTASND SFETY STANDARD.
• RECOGNISE SAFETY RELIABILITY.
• BE FAMILIAR WITH HUMAN FACTOR ISSUES.
• BE AWARE OF SAFETY SENSORS AND MONITORING.
• REALIZE SAFEGAURDING.
• PERCEIVE THE IMPORTANT FACTORS OF TRAINING.
• APPREHEND SAFETY GUIDELINES.
• UNDERSTAND DEFINITIONS.
• SAFETY METHOD AND TECHNIQUE USED FOR AVOIDING
  ACCIDENTS.
• INCLUDES THE USUAL CONSIDERATIONS OF MAN, MACHINE
  AND WORKSTATIONS, ENVIRONMENT, AND THE INTERDFACE
  BEHAVIOUR, BUT IT MUST ALSO CONSIDER SOFTWARE.

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ROBOTS AND CONVENTIONAL MACHINERY

• THREE MAJOR DIFFERENCES BETWEEN ROBOTS AND
  CONVENTIONAL MACHINERY CAN BE IDENTIFIED THAT ARE
  CONCERN OF SAFETY PERSONNEL.
• SPEED OF MOVEMENT.
• PREDICTABILITY OF MOVEMENT.
• HAZARD ZONES.
• IN CONVENTIONAL MACHINERY HAZARD ZONES MAY BE
  DIFFICULT TO RECOGNIZE, BUT ARE FIXED WITH TIME.
• ALSO THE MAIN DIFFERENCE BETWEEN CONVENTIONAL
  MACHINERY AND ROBOT IS THAT A ROBOT CAN BE
• PROGRAMMED TO DO DIFFERENT JOBS.
• REACT TO CHANGES IN THE PROCESS, EVEN MAKING
  DECISIONS FROM A LIMITED NUMBER OF CHOICES.
• SAFETY ENGINEERING SHOULD BE APPLIED TO ROBOT
  SAFETY, PARTICULARLY IN THE HUMAN FACTORS ASPECTS
  AND SYSTEMS SAFETY APPROACHES.
• ROBOT SAFETY MUST INCLUDE THE USUAL
  CONSIDERATIONS OF MAN, MACHINE AND WORKSTATIONS,
  ENVIRONMENT, AND THE INTERFACE BEHAVIOR, BUT IT
  MUST ALSO CONSIDER SOFTWARE

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CAUSES OF ACCIDENTS

• ENGINEERING DEFICIENCY
• LACK OF PROPER PROCEDURES
• INADEQUATE PROGRAMMING
• EMERGENCY STOP SWITCHES MUST APPEAR ON THE
  CONTROL PANEL AND ALSO BE ADDED TO THE PENDANT
  USED IN THE TEACH MODE WHERE THE OPERATOR OR
  PROGRAMMER MAY BE MOVING IN THE ROBOTS WORK
  ENVELOPE.
• COMPREHENSIVE INSTRUCTION AND OPERATION
  PROCEDURES MUST ALSO BE INCORPORATED THROUGH
  TRAINING PROGRAMS.

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SAFETY STANDARDS

• SAFETY IS AN IMPORTANT CONSIDERATION IN
  INSTALLING, PROGRAMMING, OPERATING, AND
  MAINTAINING ROBOT SYSTEMS.
• SAFETY CAN ALSO BE CONSIDERED AS A JUDGMENT OF
  THE ACCEPTABILITY OF DANGER, WHERE DANGER IS THE
  COMBINATION OF HAZARD AND RISK.
• HAZARD IS DEFINED AS INJURY PRODUCER, AND RISK IS
  DEFINED AS THE PROBABILITY THAT AN INJURY WILL
  OCCUR.
• THE CAUSES OF EMPLOYEE INJURY IN ROBOTIC
  ENVIRONMENT INCLUDES
• PARTS OF THE BODY BEING CAUGHT.
• BEING STRUCK BY A PART OR ROBOT GRIPPER.
• FALLING FROM THE EQUIPMENT OR STRUCTURE.
• SLIPPING OR TRIPPING ON WALKING OR WORKING
  SURFACES.
• EXPOSURE TO DANGEROUS LEVELS OF HEAT OR
  ELECTRICITY
• EXCESSIVE PHYSICAL STRAIN

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• SAFETY STANDARDS ARE VERY IMPORTANT IN THE
  WORKPLACE. ALL THE PROFESSIONAL ASSOCIATIONS HAVE
  DEFINED THE FOLLOWING PRIORITIES FOR ELIMINATING
  HAZARDS.
• ELIMINATE THE HAZARD THROUGH THE MACHINE DESIGN
  STAGE.
• APPLY SAFEGUARDING TECHNOLOGY.
• USE WARNING SIGNS AND LABELS.
• TRAIN AND INSTRUCT THE WORKER, PROGRAMMER, AND
  MAINTENANCE PERSONNEL.
• PRESCRIBE PERSONAL PROTECTIVE EQUIPMENT AND
  DEVICES.

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HUMAN FACTOR ISSUES

• HUMAN FACTOR(ERGONOMICS) ISSUES OR ENGINEERING IS
  THE STUDY OF THE HUMAN-MACHINE INTERACTION AND IS
  DEFINED AS AN APPLIED SCIENCE THAT COORDINATES
  THE DESIGN OF DEVICES, SYSTEMS AND PHYSICAL
  WORKING CONDITIONS WITH THE CAPACITIES AND
  REQUIREMENTS OF THE WORKER.
• A MACHINE OR ROBOT SYSTEM DESIGNED WITH POOR
  ERGONOMICS WILL BE UNCOMFORTABLE AND TIRING TO
  USE, MAY EVEN BE DANGEROUS.
• BESIDES THE SIZE OF A ROBOTS WORK ENVELOPE, ITS
  SPEED, ITS PROXIMITY TO HUMANS, AND INTERACTION
  WITH OTHER MACHINERY, MANY OTHER FACTORS SHOULD
  BE CONSIDERED AND INVESTIGATED SUCH AS
• THE LAYOUT OF CONTROL PANELS.
• TEACH-PENDANT ACCURACY.
• PERSONNEL TRAINING
• BARRIER GUARDS.
• SAFETY DEVICES.
• INTERLOCKS.
• WARNINGS
• IN ADDITION HUMAN FACTOR ISSUES SHOULD INCLUDE
  EVALUATION OF A ROBOT WORKSTATIONS WHEN AN
  OPERATOR ENTERS THE WORKSTATIONS FOR MAINTENANCE,
  PROGRAMMING, AND THE LIKE.

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SAFETY SENSORS AND MONITORING

• SAFETY MONITORING INVOLVES THE USE OF SENSORS TO
  INDICATE CONDITIONS OR EVENTS THAT ARE UNSAFE OR
  POTENTIALLY UNSAFE.
• THE OBJECTIVE OF SAFETY MONITORING INCLUDES NOT
  ONLY THE PROTECTION OF HUMANS WHO HAPPEN TO BE IN
  THE CELL, BUT ALSO THE PROTECTION OF THE
  EQUIPEMENT IN THE CELL.
• THE SENSORS USED IN THE SAFETY MONITORING RANGE
  FROM THE SIMPLE LIMIT SWITCHES TO SOPHISTICATED
  VISION SYSTEM THAT ARE ABLE TO SCAN THE WORKPLACE
  FOR INTRUDERS AND OTHER DEVIATIONS FROM THE
  NORMAL OPERATING CONDITIONS.
• GREAT CARE MUST BE TAKEN IN WORKCELL DESIGN TO
  ANTICIPATE ALL POSSIBLE MISHAPS THAT MIGHT OCCUR
  DURING THE OPERATION OF THE CELL, AND TO DESIGN
  SAFEGAURDS TO PREVENT OR LIMIT THE DAMAGE
  RESULTING FROM THESE MISHAPS.

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LEVELS OF ROBOT SAFETY

• THE NATIONAL BUREAU OF STANDARDS DEFINES THREE
  LEVELS OF SAFETY SENSOR SYSTEMS IN ROBOTS.
• LEVEL 1 --- PERIMETER PENETRATION DETECTION.
• LEVEL 2 --- INTRUDER DETECTION INSIDE THE
  WORKCELL
• LEVEL 3 --- INTRUDER DETECTION IN THE IMMEDIATE
  VICINITY OF THE ROBOT.
• LEVEL 1 SYSTEMS ARE INTENDED TO DETECT THAT AN
  INTRUDER HAS CROSSED THE PERIMETER BOUNDARY OF
  THE WORKCELL WITHOUT REGARD TO THE LOCATION OF
  THE ROBOT.
• LEVEL 2 SYSTEMS ARE DESIGNED TO DETECT THE
  PRESENCE OF AN INTRUDER IN THE REGION BETWEEN THE
  WORKCELL BOUNDARY AND THE LIMIT OF THE ROBOT WORK
  VOLUME.
• LEVEL 3 SYSTEMS PROVIDE INTRUDER DETECTION INSIDE
  THE WORK VOLUME OF THE ROBOT.

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• THERE ARE TWO COMMON MEANS OF IMPLEMENTING A
  ROBOT SAFETY SENSING SYSTEM
• PRESSURE SENSITIVE FLOOR MATS --- ARE AREA PADS
  PLACED ON THE FLOOR AROUND THE WORKCELL THAT
  SENSE THE WEIGHT OF SOMEONE STANDING ON THE MAT.
  THESE CAN BE USED FOR EITHER LEVEL1 OR LEVEL2
  SENSING SYSTEMS.
• LIGHT CURTAIN --- CONSISTS OF LIGHT BEAMS AND
  PHOTSENSITIVE DEVICES PLACED AROUND THE WORKCELL
  THAT SENSE THE PRESENCE OF AN INTRUDER BY AN
  INTRRUPTION OF THE LIGHT BEAM. USE OF LIGHT
  CURTAINS WOULD BE MORE APPROPRIATE AS LEVEL1
  SYSTEMS.

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• PROXIMITY SENSORS LOCATED ON THE ROBOT ARM COULD
  BE UTILIZED AS LEVEL 3 SENSORS.
• THE SAFETY MONITORIN STRATEGIES THAT MIGHT BE
  FOLLOWED BY THE WORKCELL CONTROLLER WOULD INCLUDE
  THE FOLLOWING SCHEMES.
• COMPLETE SHUTDOWN OF THE ROBOT UPON DETECTION OF
  AN INTRUDER.
• ACTIVATION OF WARNING ALARMS.
• REDUCTION OF THE SPEED OF THE ROBOT TO SAFE
  LEVEL.
• DIRECTING THE ROBOT TO MOVE ITS ARM AWAY FROM THE
  INTRUDER TO AVOID COLLISION.
• DIRECTING THE ROBOT TO PERFORM TASKS AWAY FROM
  THE INTRUDER.
• NOTE THERE IS ANOTHER SAFETY MONITORING CALLED A
  FAIL-SAFE HAZARD DETECTOR. THE CONCEPT OF THIS
  DETECTOR IS BASED ON THE RECOGNITION THAT SOME
  COMPONENT OF BASIC HAZARD SENSOR SYSTEM MIGHT
  FAIL AND THAT THIS FAILURE MIGHT NOT BE FOUND OUT
  UNTIL SOME SAFETY EMERGENCY OCCURRED. THE
  FAIL-SAFE HAZARD DETECTOR IS DESIGNED TO OVERCOME
  THIS PROBLEM.

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SAFEGUARDING

• MOST INDUSTRAIL ACCIDENTS OCCUR ARE THE RESULTS
  OF UNSAFE ACTS BY THE WORKER. UCH ACTS CAN OCCUR
  DUE TO
• IMPROPERLY TRAINED OPERATORS.
• CARELESS PROGRAMMERS ACTIVATING THE WRONG
  CONTROLS.
• COMPONENT FAILURE OR OTHER UNSAFE CONDITIONS IN
  THE PLANT.
• MAJOR CONCERN IN SAFETY OF ALL PERSONNEL INVOLVED
  WITH INDUSTRIAL ROBOTS IS VERY IMPORTANT.
• ACCORDING TO THE NATIONAL SAFETY COUNCIL(1991)
  THE PRINCIPAL HAZARDS ASSOCIATED WITH ROBOTS ARE
  AS FOLLOWS
• BEING STRUCK BY A MOVING ROBOT WHILE INSIDE THE
  WORK ENVELOPE.
• 2. BEING TRAPPED BETWEEN A MOVING PART OF A ROBOT
  AND ANOTHER MACHINE, OBJECT, OR SURFACE.
• 3. BEING STRUCK BY A WORKPIECE, TOOL, OR OTHER
  OBJECT DROPPED OR EJJECTED BY A ROBOT.

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SAFEGUARDING (CONTD.)

• ROBOT SAFEGUARD
• TO ERECT A PHYSICAL BARRIER AROUND THE ENTIRE
  PERIMETER OF A ROBOTS WORK ENVELOPE.
• A GUARD CONTAINING A SENSING DEVICE THAT
  AUTOMATICALLY SHUTS DOWN THE ROBOT IF ANY PERSON
  OR OBJECT ENTERS ITS WORK ENVELOPE CAN BE
  EFFECTIVE.
• TO PUT SENSITIZED DOORS OR GATES IN THE PERIMETER
  BARRIER THAT AUTOMATICALLY SHUT DOWN THE ROBOTS
  MOVEMENT WHEN THEY ARE OPENED.

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• SAFEGUARDING (CONTD.)
• EVEN THOUGH IT IS DIFFICULT TO GO TO A RISK-FREE
  ENVIRONMENT BECAUSE THER IS ALWAYS THE
  POSSIBILITY OF A MALFUNCTION OR THE VIOLATION OF
  GOOD SAFETY PRACTICES. HOWEVER, THERE ARE WAYS TO
  MINIMIZE THE POTENTIAL OF THESE ERRORS
• SAFETY TRAINING
• DEPENDABLE MACHINE DESIGN
• HIGH-RELIABILITY CONTROLS
• PROPER LAYOUT WORK AREA.
• SAFE POSITION AND CLEAR VISIBILITY FOR
  PROGRAMMING.
• ESTABILISHING PROPER MAINTENANCE PROCEDURES.
• ADEQUATE INSTALLATION PERFORMED IN THE PRESENCE
  OF SAFETY PERSONNEL.
• OBEYING SAFETY RULES AND REGULATIONS OF
  AUTHORITATIVE ORGANIZATIONS.

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SAFETY GUIDLINES

• THE UNEXPECTED ROBOT MOVEMENTS ARE THE CONCERN OF
  EMPLOYEES FOR OBTAINING FURTHER GUIDELINES ON
  ROBOTICS SAFETY.
• RESEARCHERS HAVE DEVELOPED MANY GUIDELINES
  PERTAINING TO SAFETY ISSUES IN ROBOTS.
• FOLLOWING GUIDELINES ARE FOR SAFE USE OF ROBOTS
  IN A PRODUCTION ENVIRONMENT
• IF THE ROBOT IS NOT MOVING, DO NOT ASSUME IT IS
  NOT GOING TO MOVE.
• IF THE ROBOT IS REPEATING PATTERN, DO NOT ASSUME
  IT WILL CONTINUE.
• ALWAYS BE AWARE OF WHERE YOU ARE IN RELATIONSHIP
  TO THE POSSIBLE POSITIONS THAT THE ROBOT MAY
  REACH.

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SAFETY GUIDELINES (CONTD.)

• 4. BE AWARE IF THERE IS POWER ACTUATORS.
  INDICATOR LIGHTS WILL BE ON WHEN THERE IS POWER
  TO THE ACTUATORS.
• 5. TEACHING, PROGRAMMING, SERVICING, AND
  MAINTENANCE ARE THE ONLY AUTHORIZED REASONS FOR
  ENTRY INTO THE WORK ENVELOPE.
• 6. BEFORE ACTIVATING POWER TO THE ROBOT,
  EMPLOYEES SHOULD BE AWARE OF WHAT IT IS
  PROGRAMMED TO DO, THAT ALL SAFEGUARDS ARE IN
  PLACE, AND THAT NO FOREIGN MATERIALS ARE PRESENT
  WITHING THE WORK ENVELOPE.
• 7. NOTIFY SUPERVISION IMMEDIATELY WHEN AN
  UNEXPECTED INTERRUPTION TO THE NORMAL ROBOT WORK
  CYCLE OCCURS.
• 8. REPORT ANY MISSING OF DEFECTIVE SAFEGUARD TO
  SUPERVISION IMMEDIATELY. CHECK ALL SAFEGUARDS AT
  THE BEGINNING OT EACH SHIFT.

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SUMMARY

• SAFETY IS AN IMPORTANT COMPONENT IN INDUSTRIAL
  AUTOMATION.
• ROBOT SAFETY DEPENDS ON THE SIZE OF THE ROBOTS
  WORK ENVELOPE, ITS SPEED, AND ITS PROXIMITY TO
  HUMANS.
• SAFETY SENSORS AND MONITORING PROVIDE THE
  CAPABILITY OF THE WORKCELL CONTROLLER AND ITS
  SENSORS TO MONITOR THE OPERATION DURING UNSAFE
  CONDITIONS IN THE CELL.
• SAFEGUARDING IS THE PREVENTION OF INJURY OR
  ACCIDENT IN THE WORKPLACE.
• TRAINING IS A MAJOR FACTOR IN THE SUCCESSFUL
  IMPLEMENTATION OF ANY ADVANCED TECHNOLOGY IN A
  COMPANY OR OPERATION.
• SAFETY GUIDELINES HAVE BEEN DEVELOPED BY
  RESEARCHERS PERTAINING TO SAFETY ISSUES IN ROBOTS
  TO REDUCE OR ELIMINATE ACCIDENTS IN A PRODUCTION
  ENVIRONMENT.