Presentation on theme: "ISAT 303 Mod 1-1 1997-2001 M. Zarrugh Module I Sensors and Measurements in MFG The objectives of this module are to –understand the role which sensors."— Presentation transcript:
ISAT 303 Mod 1-1 1997-2001 M. Zarrugh Module I Sensors and Measurements in MFG The objectives of this module are to –understand the role which sensors and measurements play in manufacturing –describe sensors used in detecting objects –introduce object identification through bar codes and RFID tags –discuss measurements used to describe conditions of a process –briefly describe sensors used in machine tool and robotic applications
ISAT 303 Mod 1-2 1997-2001 M. Zarrugh Sensing and Measuring Sensing - determination of process condition by automatic means. Measurement - implies the automatic and real-time determination of process values »Values include pressure, temperature, velocity, no. of parts, etc..
ISAT 303 Mod 1-3 1997-2001 M. Zarrugh Automation & Shop Floor Control contd. CONTROL IMPLIES: »sensing current conditions »analyzing them and then »effecting changes in the process [ACT]
ISAT 303 Mod 1-4 1997-2001 M. Zarrugh Automation & Shop Floor Control It is Necessary to: –gather information in real-time and –use the information to make “timely decision”. E.G..: »secure production equipment »move assembly materials and components »move material handling equipment as needed e.g.. robots, AGVS, LGVS, conveyors.
ISAT 303 Mod 1-5 1997-2001 M. Zarrugh Sensing and Measurement are Critical Elements of Feedback Control Systems Controller System or Process Actual Behavior Desired Behavior Open-Loop Control Closed-Loop (Feedback) Control Controller System or Process Actual Behavior Desired Behavior Sensing & Measurement
ISAT 303 Mod 1-6 1997-2001 M. Zarrugh Feedback Control Systems: An Example FurnaceRoom Thermometer in Thermostat Heat q Actual Temperature T Desired Temperature TdTd On/Off signal Actuator Space Heating System System Sensor Thermo- stat Controller
ISAT 303 Mod 1-7 1997-2001 M. Zarrugh Role of Instrumentation & Measurement in Manufacturing Statistical Process Control: manufacturing process data must be collected and transmitted to the control computer which prepares the control charts and alerts the operator to serious deviations. Dedicated Digital Control: programmable logic controllers need status data of the tasks and events being controlled. Numerical Control of Machine Tools: positions of the cutting tool relative to the part must be fed back to the control computer to insure accurate cutting.
ISAT 303 Mod 1-8 1997-2001 M. Zarrugh Role of Instrumentation & Measurement in Manufacturing Adaptive Control: cutting conditions, such as noise, vibrations, temperature and force data need to be measured so that the controllers can adapt cutting parameters to changing conditions. Shop Floor Control: real-time data on the status of resources (people and machines) and parts need to be monitored so that timely decisions can be made. Manufacturing Cell: supervisory computer needs status data of the operations and events being controlled so that these are sequenced properly.
ISAT 303 Mod 1-9 1997-2001 M. Zarrugh Types of Measurements in the Factory Object detection Object identification Measurement of condition Sensing for machine tools and robots
ISAT 303 Mod 1-10 1997-2001 M. Zarrugh Object Detection Limit Switches: mechanical contact closes or opens when an object trips the switch. (cheap, simple, but slow) –single pole (SP) normally open (NO) –single pole (SP) normally closed (NC) –double pole (DP) normally open (NO) Photoelectric Sensors: object interrupts light or IR beam which causes on/off action in sensing circuit. –hysteresis: light threshold level for “on” or “off” setting Proximity Sensor: non-contacting sensors that respond to the presence of material: inductive and magnetic sensors for metallic material and capacitive devices for all materials
ISAT 303 Mod 1-11 1997-2001 M. Zarrugh Object Identification Necessary for tracking materials, parts and final products in the factory. Bar codes (sequences of light and dark bands) are most common: –Universal Product Code (UPC) for consumer items (numbers only) xxx xxx 12 Digits MFRItem Parity Code Key 4 bars per digit –Code 39 provides 44 alphanumeric characters: most common in manufacturing: more versatile and flexible than the UPC code. There are 9 bars per character.
ISAT 303 Mod 1-12 1997-2001 M. Zarrugh Measurement of Conditions: Transducers Transducers are devices which generate an electrical output from other forms of input energy. Basic transducer types by physics of operation:
ISAT 303 Mod 1-13 1997-2001 M. Zarrugh Sensing for Machine Tools Basic sensing associated with motion control of the machine tool itself will be discussed in module III. Other types of sensing needed for machining are Part dimensions: –Coordinate measurement machines (CMMs) –Optical gaging: laser, video camera Tool wear (indirect): –increased cutting forces –increased power consumption Axial motion: –Optical encoders Sequencing: –proximity or limit switches
ISAT 303 Mod 1-14 1997-2001 M. Zarrugh Robot Sensing Basic sensing associated with motion control of the robot itself is similar to that of machine tools and will be discussed in module III. Other types of sensors needed to provide tactile, visual or force feedback to the robot are Touch sensors: –Skin-like sensors: arrays of strain or pressure transducers –Spatial (hepatic) perception: wrist force measurement Vision: –Video camera: record images which are analyzed to recognize part shapes and orientations and to detect defects Voice recognition: –Speech recognition are used for programming robots and for issuing commands from busy operators or from disabled persons using the robots as assistive devices.
ISAT 303 Mod 1-15 1997-2001 M. Zarrugh Sensing & Measuring in Manufacturing ObjectIdentification ObjectDetection ConditionDetection Sensing for Mach/Robots bar codes magnetic stripes RF devices vision/voice limit switches prox. detectors sensors transducerst/c laser systems tv cameras optical encoders encoderstactile sensors sensors