System Components and Automation
FoundationManual systems run on people while automated systems sense, decide and act by themselves; learn to break systems into subsystems and you can read how electric doors, thermostats and traffic lights work.
- Manual systems run on people; automated systems sense, decide and act themselves
- Four component roles: sensors input, controllers decide, actuators act, feedback corrects
- Control systems are everywhere, from thermostats to automatic railways
文體小知識：科技知識說明文把系統拆解成組件與子系統，配合手動與自動化的對比實例，令讀者掌握分析身邊控制系統的方法。
§Text Passage
1Some systems run on people from start to finish; others sense, decide and act by themselves. Manual systems are like an old tap — every move needs a hand. Automated systems use sensors for eyes, a controller for a brain and actuators for hands, forming a tireless loop of operation: sensor taps, electric doors and robot vacuums all work this way.
2Open any automated system and you find four roles: sensors turn environmental changes into signals, the controller judges against settings, actuators turn commands into motion, and feedback returns results for correction. Thermostats, lift dispatching and automatic trains are all the work of these components in concert.
3Faced with a complex system, engineers use subsystem analysis: split the whole into blocks with clear functions, each with its own input, processing and output, linked by signals. Understanding, design and fault-finding all become orderly — vending machines and electric doors yield to the same method.
4Analysis is also where design begins: draw the block diagram, decide what will sense, control, act and feed back, then pick real components and assemble. See through a system's structure and you can understand the technology around you — and build automated devices of your own.
1Summary 重點摘要
Manual systems run on people while automated systems sense, decide and act by themselves; learn to break systems into subsystems and you can read how electric doors, thermostats and traffic lights work.
2Vocabulary cards Vocabulary
A system that senses, decides and acts on its own without continuous human operation.
A system whose every step is operated and controlled by a person.
A part detecting environmental changes and turning them into signals.
The part that receives signals, decides and issues commands.
The part that turns commands and energy into action, such as a motor or cylinder.
An independent block within a larger system, handling one function.
Returning the output to the controller for comparison so later actions are corrected.
The current, air pressure or data carrying information inside a system.
A door opened and closed automatically by sensing and drive systems.
Control that holds a set temperature automatically from temperature sensing.
3Step by step Steps
- Manual systems versus automationSecondary 1 taught input, processing and output; Secondary 3 sorts systems by who operates them. In a manual system a person observes, decides and executes every step — pulling a cord to light a lamp, adjusting a tap by hand. An automated system replaces eyes with sensors, the brain with a controller and hands with actuators, running its sense-decide-act loop alone, like a tap that sees hands and flows. Automation reacts fast, never tires and works in dangerous places. For example, old lifts needed an operator working the lever floor by floor; modern lifts sense and decide their stops and doors automatically, far safer and faster.
- What system components doAn automated system is usually built from four kinds of component. Sensors on the input side detect and turn temperature, light, distance or pressure into signals. The controller receives signals and judges against settings, such as whether the room has fallen below the set point. Actuators act on commands, starting motors, heaters or cylinders. Feedback parts report the result back to the controller, closing the loop. For example, a motion-sensor lamp's infrared sensor detects a person, the controller notes the room is dark, a relay lights the lamp, and after a quiet interval it switches off — all four components present.
- Control systems at homeHomes grow more automated by the year: an air conditioner's thermostat compares room temperature with the setting, compressing and stopping by itself; refrigerators, rice cookers, robot vacuums, sensor lamps and smart locks are everywhere; some add phone control and schedules to become smart homes. The key to understanding them is locating the sensor, controller, actuator and feedback. For example, a robot vacuum senses obstacles and drops, plans its cleaning route, drives wheels and fan, and when the battery runs low the feedback sends it home to charge — no hands needed, the result of components working together.
- Control systems in societyBeyond the home, public infrastructure is full of control systems: traffic lights tune junctions by traffic flow and time; railways watch train positions and gaps, adjusting speed automatically for safe spacing; water systems start and stop pumps by pressure; car-park barriers and automatic tellers work the same way. Such systems demand extreme reliability, so they add interlocked sensors and backup power. For example, some MTR lines run automatic train operation: trackside sensors compute each train's position, a central controller decides speed and stopping, trains glide under protection while the captain supervises and handles exceptions — automation in public transport.
- Subsystem analysis: splitting the wholeFaced with a complex system, engineers split it: divide the whole into subsystems, each with its own input, processing and output, then chain their outputs and inputs together and the system reads clearly. The method makes faults easier to locate and design and testing easier to share. For example, analyse a vending machine into a coin-sensing subsystem, a selection-control subsystem, a product-delivery subsystem and a display subsystem — the coin block sends a paid signal to the control block, which turns the spiral to release the goods; check block by block and no fault can hide.
- Open and closed loops in automationSecondary 2 introduced open and closed loops. An automated system without feedback merely follows its preset program — open-loop automation, simple but unable to correct itself. With feedback, closed-loop automation keeps comparing target with result and adjusts automatically. Which to choose depends on how much accuracy and disturbance the task involves. For example, street lamps on timers are open loop — they light on schedule whatever the sky; an air conditioner's thermostat is closed loop, the sensor feeding back to hold the room at the setting; an irrigation system with a soil-moisture sensor upgrades from timed watering to need-based watering, saving water and growing better plants.
- Steps for analysing the systems around youBuild an analysing habit. First state the system's task. Second identify which parts sense (input), which control (processing) and which act (output). Third decide whether feedback exists — open loop or closed. Fourth draw the block diagram with signal flows marked. The same steps serve design: sketch the block diagram first, then pick real components for each block. For example, analyse motorised curtains at home: the motor and belt are actuators, the remote receiver the input, the controller processes commands, and limit switches feed back to stop over-travel — one block diagram tells the whole story.
5Worked example Example
Example: a shopping mall's electric door opens as someone approaches, closes after they pass, and bounces back the moment it meets an obstacle. Analyse it with subsystems.
- Sensing subsystem → microwave and infrared sensors detect approach and output a person-present signal
- Control subsystem → the controller decides between open, hold and close states and keeps the timing
- Drive subsystem → a motor with a belt moves the door leaves along the track open or shut
- Safety subsystem → edge sensors and limit switches feed back the door position, triggering an immediate bounce on obstacles
- Answer: The electric door is a classic closed-loop automation: sensing as input, with microwave and infrared detectors reading the flow of people; control as processing, choosing open, hold or close against the clock; drive as output, the motor and belt moving the leaves; and safety as feedback watching position and obstacles, bouncing back the instant something is caught. Four subsystems linked by signals, each with a protective response if another fails. Subsystem analysis turns a complex door into a few clear blocks — the engineer's basic method for understanding and repairing any system.
6Common mistakes Mistakes
7Quick check Quick check
Q1Which component turns commands into real action?
Q2Is an air conditioner's thermostatic control open or closed loop, and why?
Q3What are the benefits of subsystem analysis?
Q4Which is a manual system? A. sensor tap B. traditional tap C. thermostatic kettle
Q5What does feedback do in an automated system?
8Recap Recap
- Manual systems run on people; automated systems sense, decide and act themselves
- Four component roles: sensors input, controllers decide, actuators act, feedback corrects
- Control systems are everywhere, from thermostats to automatic railways
- Subsystem analysis splits complexity into blocks for understanding, design and repair
- Open loops are simple and reliable, closed loops precise and self-correcting — choose by task