Understanding Control Systems
Control system
A combination of devices and algorithms that automate tasks by monitoring and manipulating the environment
These systems are designed to operate independently, reducing the need for human intervention.
Control systems are mostly input-process-output systems. They receive input from sensors, process it using algorithms, and produce output through actuators.
Key Components of Control Systems
Key components of control systems usually include:
- Sensors
- Processors
- Output transducers/actuators
Sensors
Sensors
Devices that detect and measure physical quantities, converting them into signals
Sensors provide signals representing the environment to be processed by microprocessors to make decisions.
Key functions of sensors:
- Data Collection: Sensors detect physical quantities such as temperature, motion, or pressure.
- Signal Conversion: They convert these analogue signals into digital form using an analogue-to-digital converter (ADC).
What is ADC?
Key Sensor Characteristics:
- Accuracy: Ensures precise measurements.
- Range: Defines the limits within which the sensor operates effectively.
- Resolution: Determines the smallest change the sensor can detect.
Sensors must be insensitive to irrelevant environmental factors and should not influence the property they measure.
Processors
Processors
Components that analyse the data from sensors and decide what actions to take in the context of control systems
Key functions of processors:
- Data Processing: The processor receives digital signals from the sensor and executes algorithms to determine the appropriate action.
- Decision Making: Based on the processed data, the processor
- Think of the processor as the decision-maker.
- It analyses data from sensors and determines the appropriate action to take based on predefined rules or algorithms.
One of the most popular types of processors is microprocessor.
Microprocessor
Integrated circuits that perform arithmetic, logic, and control operations
We can outline several types of microprocessors:
- General-Purpose Microprocessors: Found in computers, capable of running a wide range of applications.
- Microcontrollers: Embedded in devices like washing machines and elevators, designed for specific tasks.
- Graphics Processing Units (GPUs): Specialised for handling complex graphics calculations.
Microprocessors are programmable, meaning they can be updated or reprogrammed to adapt to new tasks or improve performance.
Output transducers
Key functions of output transducers:
- Signal Conversion: The processor's digital output is converted into an analogue signal using a digital-to-analogue converter (DAC).
- Action Execution: Output transducers, often actuators, convert these signals into physical actions, such as moving a motor or opening a valve.
Actuators
Devices that effect changes in a system based on controller signals.
This cycle is the foundation of closed-loop control systems, where feedback is used to adjust actions and maintain desired outcomes.
What is a Feedback Loop?
Feedback Loops
Mechanisms that use the results of previous actions to adjust future behaviour, helping the system improve or maintain performance
Feedback loop can be divided into four steps:
- Sensor Input: Collects data from the environment.
- Processing: Compares the data to a desired state or setpoint.
- Output: Adjusts actuators to achieve the desired state.
- Feedback: Monitors the results and repeats the cycle.
- When analysing a control system, always identify the input, process, and output stages.
- This will help you understand how the system functions and adapts to changes.
In some cases, a control system can be considered a process control system.
Process control
A system that automatically monitors and manages physical processes (like temperature, speed, or pressure) to maintain desired output
More About Feedback
Feedback
The process of using output data as input to adjust future actions
Why is feedback important? Because it improves:
- Stability: Feedback helps maintain a system's desired state, even in changing conditions.
- Efficiency: By continuously adjusting actions, feedback minimises resource waste.
- Adaptability: Systems can respond to unexpected events or disturbances.
We classify feedback into two types:
Positive Feedback: Amplifies changes, often leading to instability.
A thermostat adjusts heating to maintain a set temperature.
When designing a feedback loop, ensure sensors are accurate and responsive to changes in the environment.
And negative feedback: Counteracts changes, promoting stability.
Additionally, based on the presence or lack of feedback, we can distinguish between 2 types of control systems: open-loop and closed-loop.
Open-loop systems
Execute predefined operations without feedback.
A microwave that runs for a set time regardless of food temperature.
Closed-loop systems
Continuously monitor output and adjust inputs based on feedback.
- A car's cruise control system monitors the vehicle’s speed.
- If the car slows down while going uphill, the system detects this and increases engine power to maintain the set speed, using the output (speed) to adjust the input (throttle).
- Relying solely on open-loop systems can lead to inefficiencies, as they cannot adapt to changes in the environment.
- In contrast, closed-loop systems are more efficient because they do continuously adapt to changes in the environment.
The Impact of Control Systems
- Efficiency: Automate repetitive tasks, reducing human error and energy waste.
- Safety: Enhance safety in environments like elevators and traffic systems.
- Convenience: Improve accessibility and user experience in everyday devices.
- How does feedback differ between open and closed-loop systems?
- Why is negative feedback more common in control systems than positive feedback?
- Can you think of a real-world example where feedback is essential for system stability?
- How do control systems balance the need for automation with the potential loss of human oversight?
- What ethical considerations arise when designing systems that replace human decision-making?
