Sensors Collecting Manufacturing Process Data

Transcription

1 Sensors & Actuators

2 Sensors Collecting Manufacturing Process Data Data must be collected from the manufacturing process Data (commands and instructions) must be communicated to the process Data are of three types: Continuous analog signals Discrete binary data Pulse data or discrete data that is not binary

3 Sensors and Transducers Sensor A device that is used to make a measurement of a physical variable Transducer A device that converts one type of energy to another Converts a physical variable to electric voltage (or current) which is is more convenient to evaluate and analyze

4 Different Types of Sensors Accelerometer Ammeter * Bimetallic switch Bimetallic thermometer Tachometer * Dynamometer Float transducer * Fluid flow sensor * Fluid flow switch Linear variable diff. transformer Limit switch (mechanical) * Manometer * Ohmmeter * Optical encoder * Photoelectric sensor * Photoelectric sensor array * Photometer Piezoelectric transducer Potentiometer * Proximity switch * Radiation pyrometer * Resistance-temperature detector * Strain gage * Thermistor Thermocouple * Ultrasonic range sensor * * Indicates currently have in sensor inventory

5 Classification of Sensors Type Based on converted signal Analog Digital (discrete) Method of Detection Contact Non-contact In-Process

6 Actuators Provide the means accomplish the automated process Classifications Electrical Pneumatic Hydraulic

7 Sensors Photoelectric sensor A binary non-contact sensor (switch) consisting of emitter (light source) and receiver (photocell) triggered by interruption of light beam. Two common types: 1. Transmitted type, in which object blocks light beam between emitter and receiver; and 2. Retro reflective type, in which emitter and receiver are located in one device and beam is reflected off remote reflector except when object breaks the reflected light beam.

8 Photoelectric Sensors Source: #Basics%20of%20Sensors Sample products:

9 Proximity switch: Sensors A binary non-contact sensor is triggered when nearby object induces changes in electromagnetic field. Two types: (1) inductive and (2) capacitive.

10 Sensors Ultrasonic range sensor: Time lapse between emission and reflection (from object) of high-frequency sound pulses is measured. Can be used to measure distance or simply to indicate presence of object.

11 Vision Machine vision/computer vision/ Artificial vision Sensing vision data and its interpretation by computer Applications Components Camera (sensing image data) Digitizing hardware Digital computer Interface hardware and software Operations Sensing and digitizing of image data Image processing and analysis Application

12 Actuators

13 Actuators Actuator is hardware device that usually converts a controller command signal into a change in position or velocity of a mechanical device. Classification based on the type of power used: Electrical Hydraulic Pneumatic

14 Types of Actuators DC motor Stepping motor AC induction motor Hydraulic piston Pneumatic cylinder Solenoid Linear induction motor Relay switch

15 Electrical actuators Most common Different Types: DC servo motors, stepper motors, AC motors, and solenoids. Electrical actuators include both linear devices (output is linear displacement) and rotational devices (output is rotational displacement or velocity)

16 Pneumatic actuators Air Cylinders -- Piston inside cylinder exerts force and provides linear motion in response to air pressure. Use compressed air (typically shop air in the factory environment) as the driving power. Both linear and rotational pneumatic actuators are available. Advantages: Low cost of maintenance and operation High speed Disadvantages: Compressibility of air, limited accuracy for servo control Air filtering and drying Mostly open loop Usually limited to relatively low force applications (due to relatively low air pressures) when compared to hydraulic actuators

17 Solenoid Two-position electromechanical assembly consists of core inside coil of wire. Core is usually held at one position by spring, but when coil is energized, core is forced to other position. Linear solenoid most common, but rotary solenoid available.