Robots

Lectures 8, 9, and 11

forced worker

word “robot” is based on a Czech word (“robotoa”) which means ____________

Isaac Asimov’s

who created “three laws of robotics”

three laws of robotics

a robot may not injure a human being or, through inaction, allow a human being come to harm

a robot must obey orders given it by human beings except where such orders would conflict with the first law

a robot must protect its own existence as long as such protection does not conflict with the first or second laws

load of crap

the three laws of robotics are a _____________ created in a book

industrial robot

an automatically controlled, reprogrammable, multipurpose, manipulator programmable in three or more axes, which may be either fixed in place or mobile for use in industrial automation applications

automated positioning device

most industrial robots

speed, accuracy, and repeatability

industrial robots are used in tasks that require ___________________________

For these types of tasks, robots typically outperform humans

automotive industry, electronics, and cargo transport

common applications of industrial robots

three D’s

dull

dirty

dangerous

typical robot uses

die casting

forging

painting

welding

material handling (pick & place; palletizing)

components of a robot system

sensors/controls that provide a robot with information about its external environment

mechanical part or manipulator

end-effectors that processes an object

controller that processes information provided by the sensors and drives end-effectors

power supply

robot manipulator (body)

composed of chains of rigid bodies called links, and connected together by joints

body primary function

to enable and move the end-effectors end of the arm to do the required work

ex. a robotic gripper

arm and body motions and wrist motions

a robotic movement can be divided into two general categories

robot joints

prismatic joints

revolute joints

prismatic joint

provides a linear/translational sliding motion to a link along an axis

linear joint

orthogonal joint

revolute joints

provides rotating movement to a link around an axis

permit only angular motion

rotational

twisting

revolving

L O R T V

joint symbols

linear (L)

linear sliding movement

orthogonal (O)

transitional sliding movement

rotational (R)

provides rotating motion with the axis of rotation perpendicular to the axes of the input and output links

twisting (T)

joint rotates but rotation is parallel to the axes of the two links

revolving (V)

joint rotates but the output link axis is perpendicular to the rotational axis

work envelope

created when a robot moves its end-effector forward, backward, up and down

distances are determined by the length of a robot’s arm and the design of its axes

each axis contributes its own range of motion

robot can only perform within the confines of its ____________

maximum space

the three-dimensional volume encompassing the movements of all robot parts through their axis

determined by the length of robot’s arm and design of its axis

restricted space

the portion of the maximum space to which a robot is restricted by limiting devices

maximum distance that the robot, end-effector, and work piece can travel after the limiting device is actuated

safeguarded space

defined by the perimeter safeguarding devices

operating space

that portion of the restricted space that is actually used by the robot while performing its task program

encoder

in each robot joint

home position

a fixed position location for a robot where the joint encoders for each axis read zero

unique for each model of robot

typically robots return to this to confirm its encoder are operating correctly at the beginning of every cycle

industrial robot system

a system that includes industrial robots, the end-effectors, and the devices and sensors required for the robots to be taught or programmed, or for the robots to perform the intended automatic operations, as well as the communication interfaces required for interlocking, sequencing, or monitoring the robots

end effector

the device at the end of a robotic arm, designed to interact with the environment

EOAT

end of arm tooling

gripper

magnets, vacuum cups

tools

MIG gun, spot welder, spray gun, nut runner

robot teaching

to program a manipulator arm by manually guiding it through a series of motions and recording the position in the robot controller memory for playback

teach mode

a robot controller mode in which a robot manipulator is programmed by manually guiding it through a series of

teaching

to program a manipulator arm by manually guiding it through a series of motions and recording the position in the robot controller memory for playback

teach pendant

a handheld control box, which is used by an operator to remotely guide a robot through the motions of its tasks. the motions are recorded by the robot control system for future playback

250 mm/sec

robot movement speed in teaching mode is automatically limited to ______

Jacobian matrix

matrix algebra is integral in robotics for computing the position of a robot’s end effector by representing transformations between coordinates frames; the _______ is employed to analyze the relationship between joint velocities and end effector velocities, aiding in motion planning and control.

accuracy

the precision with which a computed or calculated robot position can be attained; normally worse than the arm’s repeatability; is not constant over the workspace, due to the effect of link kinematics

repeatability

a measure of how closely a robot can repeatedly obtain a taught position. for instance, once a manipulator is manually placed in a particular location and this location is resolved by the robot, the ____ specifies how accurately the manipulator can return to that exact location

robot singularity

for a standard six joint manipulator, a kinematic singularity is a point in the workspace where the robot loses its ability to move the end effector in some direction no matter how it moves its joints. it typically occurs when two of the robot’s joints line up, making them redundant

often causes sudden rapid movements

pounce position

an arbitrary point used before (and sometimes after also) a series of points defining a path; it is used to safely park the arm+tool in a convenient location ready to move to the beginning point of the path

pounce position

a specific point in a robot’s workspace where it is positioned to be ready for a quick, precise movement

key characteristics of pounce position

proximity - usually close to the area where the robot will perform its primary task

safety - it’s a position where the robot is unlikely to collide with other objects or people

efficiency - it’s a position that allows the robot to move quickly and efficiently to its target when provided an input

robot fixturing

a custom designed device used to locate or support the work piece during the operation

welding, machining

consistent hold

clamping

nesting

close set

space

robot work

load/unload

general duty clause

OSHA does not have a specific “robot” standard, instead it falls under the ____

general duty clause

each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees

OSHA rules that apply to robots

OSHA 1910.212 general requirements for all machines

OSHA 1910.219 mechanical power transmission apparatus

OSHA 29 CFR 1910.147 control of hazardous energy (lock-out/tagout)

NFPA 79 2015 electrical standard for industrial machinery guidelines

consensus standards

OSHA Technical Manual: Section IV: Chapter 4 - Industrial robot system safety

OSHA STD 01-12-002: Guidelines for robotics safety

Robotic Industries Association (RIA)

• American National Standard for Industrial Robots and Robot Systems - Safety Requirements

• Technical Report for Industrial robots and robot systems - Safety Requirements

OSHA robotic safety standards

robot accidents do not occur under normal operating conditions but, instead during programming, program tough-up, or refinement, maintenance, repair, testing, setup or adjustment

robot safe guarding - effective robotic safeguarding system should be based upon a hazard analysis

a combination of safeguarding methods may be used

envelope (space), maximum

the volume of space encompassing the maximum designed movements of all robot parts including the end-effector, workpiece, and attachments

restricted envelope

that portion of the maximum envelope to which a robot is restricted by limiting devices

operating envelope

that portion of the restricted envelope that is actually used by the robot while performing its programmed motions

fixed barriers

should cover the operating space and restricted space

interlocked barrier guard

a safety device used in industrial settings that prevents a machine from operating unless the guard is securely closed

safeguarding methods

fixed barrier guard

interlocked barrier guard

audible and visible warning systems

awareness barrier device

presence sensing devices

emergency robot braking

layout

wherever practicable, the ___ should allow tasks to be performed from outside the safeguarded space

if it is necessary to perform tasks within the safeguarded space there shall be safe and adequate access to the task locations

access paths should not expose operators to hazards, including slipping, tripping and falling hazards

designers should take into account the frequency and ergonomic aspects of the task

AUTO

around

under

through

over

AUTO

a fixed barrier needs to be sized such that a person cannot reach ___

fixed barrier

securely installed; requires tools to install/remove; not easily removable

safeguarding devices

personnel should be safeguarded from hazards associated with the restricted envelope through the use of one or more safeguarding devices

sensitive protective equipment (SPE)

safety mat systems

safety light curtains

safety beams

safety laser scanners

safety vision systems

minimum safe distance formula

S = (K * T) + C

K - speed constant

T - overall stopping time in sec

C - depth penetration factor in mm

muting

temporary automatic suspension of a safety function during the non-hazardous portion of the process/machine cycle

ex. muting light curtain during entry/exit of pallets on a palletizing machine

blanking

bypassing a portion of the sensing field of a presence-sensing safeguarding device

ex. small gap in light curtain to allow feeding of material through it to punch press while still protecting the operator

safety mats

pressure-sensitive safeguarding products that are designed to detect the presence of people in the sensing surfaces

anchor to the floor

risk assessment

involves identifying hazards, estimating risks, and implementing mitigation measures like engineering controls, administrative protocols, and safety equipment to ensure compliance with safety standards

it is required to ensure the safety of workers, bystanders, and equipment, as mandated by international standards

collaborative robots

designed to work in collaboration with humans through physical interaction in a shared workspace

four types of collaborative systems

power and force limiting

hand guiding

speed and separation monitoring

safety monitored stop

(these are not mutually exclusive)

power and force limiting (PFL)

where incidental contact initiated by robot is limited in energy to not cause operator harm

• forces robot can exert are limited

• robot system design eliminates pinch points, sharp edges, etc.

• robot complies and reacts when contact is made

• conditions requiring frequent operator presence

hand-guiding operation

operator uses hand-operated device to transmit motion commands or leads robot movement through direct interface

• robot motion responds to operator commands

  • may run in non-collaborative operation resumes when operator leaves collaborative workspace

speed and separation monitoring

where the robot speed reduces when an obstruction is detected

• separation distances are monitors

• robot speed directly correlates to separation distance - zones dictate allowable speed

  • stop condition given if direct contact proximity is attained

safety-rated monitored stop

the robot/collaborative robot stops before the operator enters the collaborative workspace

with a traditional robot this may be achieved with a ______ control system that complies with requirements in ANSI/RIA 15.06-2012

stop-motion condition ensured

drive power remains on

motion resumes after obstruction clears

robot motion resumes without additional action