Automated Manufacturing systems
In our everyday lives we use devices that are operated by manual control; that is, they need to be operated by humans.
Examples include cars, sewing machines, vacuum cleaners and electric drills. Automated systems, on the other hand, are designed to operate under automatic control.
Automatic control means they will operate independently or without human intervention.
Automated control systems
These systems accept data, process this data and produce data signals or actions to change the operations of another system.
The purpose of an automated control system group of elements that maintains a desired result by manipulating the value of another variable in the system is to maintain a desired result.
It achieves this result by manipulating one or more variables of another system.
Input—the air conditioner reads the room temperature using a temperature sensor
Process—this reading is compared to the set temperature entered by the user
Output—signals are sent to turn the thermostat on to adjust the temperature.
Components of automated control systems
Signal conditioners are used to ensure data signals can be understood and measured by a data acquisition device.
Often, control systems need to convert analogue data to digital data (and vice versa). During this process, the signals may suffer from interference—sometimes referred to as noise.
Signal conditioners help remove any unwanted interference and may be used on both input and output data signals.
Input devices that detect conditions in the environment then send the results as signals to the controller
Devices that help keep the signals passed to and from the controller 'clean'; that is, reduce the amount of interference in the signals
Devices that process the input signals from the sensors to produce the output signals required to drive the actuators
Output devices that perform the physical actions that have an effect on the environment
Types of automated control
Designed and built to perform one manufacturing task, 24 hours a day, 7 days a week, with some time required for system maintenance. Not flexible, e.g. new model car may require a new assembly plant to be built.
Produces large quantities of a particular product, but can be quickly altered to produce new or alternative products. The control system is capable of being quickly reprogrammed.
Entire system is involved in producing a single item. Produces items only in small quantities, e.g. CAD/CAM. Least suited to large-scale production. Expensive
Sensors obtain information from the environment
Active: Require physical interaction between the sensor and another device.
Passive: Require a change in the environment in order to operate
Type of sensor
Measure current temperature and may include control units, such as those used to control temperature in air-conditioning units
Motion and pressure sensors
Detect sudden changes of movement.
Detect changes in light or changes in colour.
Detect the presence and quantity of various chemicals.
An alarm, which uses a motion sensor, automated control component that detects sudden changes of movement detector to pick up unexpected movements in its path. These types of systems have two main components: a source of light such as a laser beam an optical/light sensor.
In a home security system, the light beam is aimed at the light sensor, across a passageway.
Automatic doors use a sensor to open doors at the required time.
The sensor is often placed at the head of the door.
It is passive and may be an ultrasonic device or a passive infrared detector.
When the presence of a person is detected a message is sent to the controller to open the door.