IB COMPUTER SCIENCE | Centralised Control Systems for Topic 7

CONTROL SYSTEMS | CENTRALISED CONTROL SYSTEMS

ALSO IN THIS TOPIC
CENTRALISED CONTROL SYSTEMS
DISTRIBUTED CONTROL SYSTEMS
TOPIC 7 REVISION
KEY TERMINOLOGY
TOPC 7 ANSWERS

A centralised control system is a type of control system where all decision-making and control processes are managed by a single central unit. This central unit receives data from various sensors or input devices, processes this information, and then issues commands to actuators or output devices to control the operation of the entire system. In such systems, the central unit is responsible for the overall management, including monitoring, decision-making, and control actions.

Centralised control systems are often contrasted with distributed control systems, where control is decentralised and distributed among multiple, interconnected units. The centralised approach is typically simpler in terms of design and communication structure, as all control actions are coordinated from a single point. However, it can have limitations in terms of scalability, fault tolerance, and flexibility compared to distributed systems. These systems are commonly used in environments where unified, cohesive control is necessary and where central oversight is beneficial, such as in building management systems, manufacturing processes, or traffic control systems.

SECTION 1 | CONTROL SYSTEMS IN EVERYDAY LIFE

Control systems are used in a wide range of applications to regulate and manage a process or a system. Here is a brief overview of some common control systems and the process control taking place in them:

Automatic doors: Automatic doors use sensors to detect the presence of people or objects, which then triggers the door to open or close. The control system in an automatic door manages the motor and the sensors to ensure that the door opens and closes smoothly, safely and efficiently.
Heating systems: Heating systems use a thermostat to regulate the temperature of a room. The thermostat senses the current temperature and sends signals to the heating system to turn on or off as needed to maintain a comfortable temperature.
Taxi meters: Taxi meters use sensors to detect the distance traveled and the time elapsed during a journey. The control system in a taxi meter calculates the fare based on the distance and time traveled and displays the amount on a screen.
Elevators: Elevators use a control system to manage the movement of the elevator car and the opening and closing of the doors. The control system ensures that the elevator operates smoothly and safely, and that the doors open and close at the right times.
Washing machines: Washing machines use a control system to manage the cycle of washing and rinsing clothes. The control system regulates the amount of water and detergent used, the temperature of the water, the speed of the drum, and the timing of the cycles.
Domestic robots: Domestic robots use a control system to manage their movements and actions. The control system monitors sensors such as cameras and microphones, and uses algorithms to determine how the robot should move and interact with its environment.
GPS systems: GPS systems use a control system to manage the reception and processing of satellite signals. The control system calculates the position of the GPS receiver based on the signals received from multiple satellites.
Traffic lights: Traffic lights use a control system to manage the timing of the lights and the flow of traffic. The control system monitors the presence of vehicles and pedestrians, and adjusts the timing of the lights to ensure a safe and efficient flow of traffic.

SECTION 2 | BASICS OF HOW A CONTROL SYSTEM WORKS

In a control system, the sensors, analog-to-digital converters, microprocessors, and actuators work together to regulate and manage a process or system. Here's how they work together:

Sensors: Sensors are used to measure various physical variables such as temperature, pressure, position, and speed. They convert these variables into electrical signals that are sent to the microprocessor.
Analog-to-Digital Converters (ADCs): ADCs are used to convert the analog signals from the sensors into digital signals that can be processed by the microprocessor. The ADCs sample the analog signals at regular intervals and convert them into a digital form, typically in the form of binary numbers.
Microprocessors: The microprocessor is the "brain" of the control system, and it performs various calculations and decisions based on the input signals from the sensors and ADCs. The microprocessor uses software algorithms to analyse the input signals and determine the appropriate control signals to send to the actuators.
Actuators: Actuators are devices that are used to control a process or system. They receive control signals from the microprocessor and convert them into physical action, such as opening a valve, turning on a motor, or adjusting a thermostat.

Together, these components form a closed-loop control system, where the output of the system is continuously measured and compared to a desired set-point. The microprocessor uses this comparison to adjust the control signals sent to the actuators, in order to keep the system operating within pre-set values. This process is repeated continuously, making small adjustments to the control signals until the desired output is achieved. In this way, the control system works to regulate and manage a process or system in an automated and efficient manner.

SIMPLE QUESTION
Streetlights are controlled automatically using sensors and a microprocessor to turn on and off as needed depending on how dark or light it is outside Describe the microprocessing involved in such a system and role of the sensors.

SAMPLE ANSWER
An input device such as a light sensor detects the light level, a signal is sent from the input device to the processor via an analogue to digital converter(ADC). The microprocessor receives the value and compares it to pre-set values and determines if the value is greater, less than or within the pre-set values. If needed a signal is sent to the actuator, an output device such as a light bulb and the light is turned on or off. The whole process is continually repeated in a loop. To avoid continuous/rapid change of state a delay may be added, so for example it should remain dark for a pre-set period of time before a signal is sent to turn the light on.

SECTION 3 | CONTROL SYSTEM INPUT DEVICES

Control systems use various types of input devices to gather information about the system being controlled. Here are some input devices that are commonly found in everyday control systems:

Sensors: Sensors are devices that measure physical variables such as temperature, pressure, motion, light, and sound. They convert these physical variables into electrical signals that can be processed by a control system. Sensors are commonly used in heating and cooling systems, automotive systems, and home automation systems.
Switches: Switches are simple devices that are used to control the on/off state of a system. They typically have two states: open (off) and closed (on). Switches can be manually operated, or they can be controlled automatically by a microprocessor in a control system.
Keypads: Keypads are input devices that allow users to enter data into a control system by pressing buttons. They are commonly used in home automation systems, security systems, and industrial control systems.
Microphones: Microphones are input devices that convert sound waves into electrical signals. They are commonly used in voice recognition systems, home automation systems, and automotive systems.
Cameras: Cameras are input devices that capture visual information and convert it into electrical signals. They are commonly used in security systems, traffic control systems, and home automation systems.
GPS Receivers: GPS receivers are input devices that receive signals from GPS satellites and use the information to determine the location and movement of a device. They are commonly used in automotive systems, navigation systems, and location-based services.

The choice of input devices in a control system depends on the specific application and the information that needs to be gathered. A well-designed control system will use the appropriate input devices to gather accurate and reliable information about the system being controlled.

Below is more detail about the purpose and possible usage of popular sensors:

Temperature sensors: Temperature sensors measure the temperature of a system or environment. They are commonly used in HVAC systems, refrigerators, and weather stations.
Pressure sensors: Pressure sensors measure the pressure of a gas or liquid. They are commonly used in industrial control systems, automotive systems, and medical equipment.
Light sensors: Light sensors measure the amount of light in a system or environment. They are commonly used in cameras, security systems, and automatic lighting systems.
Proximity sensors: Proximity sensors detect the presence or absence of objects in a system or environment. They are commonly used in industrial control systems, automotive systems, and home automation systems.
Accelerometers: Accelerometers measure the acceleration of a system or object. They are commonly used in automotive systems, aircraft systems, and mobile devices.
Magnetic sensors: Magnetic sensors detect the presence and strength of magnetic fields. They are commonly used in automotive systems, security systems, and medical equipment.
Humidity sensors: Humidity sensors measure the amount of water vapor in the air. They are commonly used in HVAC systems, weather stations, and food storage systems.
Infrared sensors: Infrared sensors detect infrared radiation and are commonly used in security systems, motion detection systems, and temperature measurement systems.

SECTION 4 | FEEDBACK LOOPS

In a control system, feedback refers to the process of using the output of the system to adjust and regulate the system's operation. Feedback is a critical component of a control system, as it helps to ensure that the system operates within the desired parameters and achieves the desired output.

The feedback loop in a control system involves several steps:

Measurement: The system's output is measured using sensors, gauges, or other monitoring devices.
Comparison: The measured output is compared to the desired output or setpoint.
Error calculation: The difference between the measured output and the desired output is calculated to determine the system error.
Adjustment: The control system adjusts the system's operation based on the error calculation to bring the measured output closer to the desired output.
Repeat: The feedback loop is repeated continuously, making small adjustments to the system's operation to keep it operating within the desired parameters.

The role of feedback in a control system is to ensure that the system operates reliably and achieves the desired output. Without feedback, the system may drift from the desired output and operate outside of the desired parameters. Feedback helps to correct for any errors or disturbances that may occur in the system, ensuring that it remains stable and responsive to changes in the input or operating conditions.

Feedback is used in a wide range of control systems, from simple systems such as thermostats to complex industrial control systems. In all cases, the role of feedback is to ensure that the system operates within the desired parameters and achieves the desired output.

Feedback can be classified into two main types: closed feedback loops and open feedback loops. Understanding these concepts is essential for designing systems that can autonomously adjust their behavior based on output results or external conditions.

CLOSED FEEDBACK LOOPS
A closed feedback loop, also known as a control loop, involves a process in which the system continuously monitors its output and adjusts its input based on feedback to maintain desired operation. This type of loop is "closed" because the action of the system is dependent on its current output.

Self-regulating | The system adjusts itself based on feedback from sensors.
Goal-oriented | Aims to reach and maintain a predefined condition or setpoint.
Dynamic response: |Automatically compensates for disturbances.

A common example is a thermostat-controlled heating system. The thermostat monitors the temperature of a room and compares it with a desired setpoint. If the room temperature drops below the setpoint, the thermostat signals the heater to turn on and heat the room until the setpoint is reached, at which point it turns the heater off. This process involves continuously measuring and reacting to the temperature of the room, ensuring the temperature stays within a target range.

OPEN FEEDBACK LOOP
An open feedback loop, by contrast, does not use feedback to control its actions. Instead, the system operates based on a preset sequence of operations without regard to the output's effect on the process or environment.

Non-self-regulating | Does not adjust based on output; follows a set plan.
Simple implementation | Easier to design and implement as it doesn’t require sensors or feedback mechanisms.
Less responsive | Does not adapt to changes in the environment or process conditions.

An example is a washing machine's basic cycle. The machine runs through a programmed sequence of filling, washing, rinsing, and spinning, regardless of the actual condition of the clothes inside it. The cycle runs for a fixed duration set by the user without adjusting for variables like the amount of dirt on the clothes or changes in load size during operation.

In embedded systems design, choosing between a closed and an open feedback loop depends on the specific requirements of the application, including factors like desired precision, responsiveness to environmental changes, and complexity of the system. Closed loops are better for applications requiring high accuracy and adaptability, while open loops can be sufficient for simpler, less variable tasks.

SECTION 5 | HOW THE COMPONENTS WORK TOGETHER

Control systems are designed to regulate and manage a process or system by continuously monitoring input data from various sensors and making adjustments to output signals that control the system's actuators or valves. The sensors are input devices that gather information about the system being controlled, such as temperature, pressure, or motion. This data is then sent to the microprocessor, which receives the analogue signals and converts them into digital form using the ADC.
Once the digital data has been processed, the microprocessor compares it to the pre-set value, also known as the set-point. If the value exceeds the pre-set value, the microprocessor sends a signal to the actuator/valve to make adjustments and maintain the system within pre-set values. If the value falls below the pre-set range, the microprocessor also sends a signal to adjust the system output signals accordingly.
To send the output signal to the actuators or valves, a DAC may be used between the microprocessor and devices to convert the digital signal back to analogue form. The control system continuously monitors the sensor inputs and adjusts the output signals as needed until the desired output is achieved.
A key aspect of control systems is the use of feedback, which is the process of comparing the output signal to the input signal to determine if the system is functioning correctly. By continuously monitoring feedback, the control system can make adjustments to the output signals to ensure that the system operates within pre-set values. This process of input, process, and output, along with the use of feedback, is what enables control systems to regulate and manage a process or system in an automated and efficient manner.

SECTION 6 | ETHICAL CONSIDERATIONS

Embedded systems, such as tagging prisoners, surveillance systems, CCTV, and improved safety systems, can have significant social impacts and raise ethical considerations. Here are some examples:

Tagging prisoners: Electronic tagging is used to monitor the movements of prisoners, allowing authorities to enforce curfews and monitor their whereabouts. While electronic tagging can be an effective way to manage prisoners, it raises ethical concerns about privacy, human rights, and the potential for abuse.
Surveillance systems: Surveillance systems, including CCTV, are used to monitor public spaces, workplaces, and homes. While surveillance systems can improve security and safety, they can also be intrusive and may infringe on people's privacy rights.
Improved safety systems: Improved safety systems, such as electronic stability control and anti-lock braking systems in cars, can improve safety on the roads. However, they can also raise ethical considerations around the cost of implementation, the potential for errors or malfunctions, and the loss of control over the vehicle.
Smart home systems: Smart home systems, which are designed to control lighting, heating, and security in the home, can provide convenience and comfort. However, they can also raise concerns about data privacy and security, as the systems may collect and share personal information about the user and their activities.

In all of these cases, it is important to consider the potential social impacts and ethical considerations of embedded systems. Some of the key ethical considerations include:

Privacy: Embedded systems may collect and store personal information, raising concerns about privacy and data protection.
Autonomy: Embedded systems can limit the autonomy of individuals, raising concerns about the potential loss of control over one's own life.
Bias: Embedded systems may contain biases that can impact certain groups or individuals, raising concerns about fairness and discrimination.
Accountability: Embedded systems may lack accountability, making it difficult to hold individuals or organisations responsible for their actions.

To mitigate these ethical considerations and ensure that embedded systems are developed and used in a responsible and ethical manner, it is important to consider the potential impacts on individuals and society as a whole, and to involve stakeholders in the development and implementation process. This may involve consulting with users, community groups, and regulatory bodies to ensure that the system is designed and implemented in a way that is fair, transparent, and respects individual rights and freedoms.

SAMPLE QUESTION
Discuss the social impacts and ethical considerations associated with the use of embedded systems for the purpose of tagging prisoners. Your discussion should go beyond the information given in the slides provided.

Embedded systems for tagging prisoners have significant social impacts and ethical considerations. From a social perspective, these systems can aid in rehabilitation by allowing prisoners more freedom, such as home confinement, while still ensuring public safety. They can reduce overcrowding in prisons and potentially lower incarceration costs. However, there's a risk of creating a 'surveillance society' where tagged individuals could be constantly monitored, potentially infringing on their privacy and civil liberties.

Ethically, the use of such systems raises questions about the dignity and rights of the prisoners. Constant monitoring can be seen as an invasion of privacy, leading to a feeling of perpetual punishment, even outside prison walls. There's also the issue of consent – whether prisoners can truly consent to being monitored in this way, or if it's a forced choice given the alternative of staying in a prison facility.

Moreover, the reliability of the technology is a concern. Malfunctions can lead to false accusations of violating parole terms, unfairly penalizing individuals. This brings into question the justice and fairness of relying on technology for monitoring.

Another ethical consideration is the potential for data misuse or breaches. The sensitive information collected by these systems could be targeted by hackers, leading to unauthorized tracking or profiling, which could have severe consequences for the individuals involved.

In conclusion, while embedded systems for tagging prisoners offer benefits like reduced prison populations and potentially improved rehabilitation processes, they also present significant social and ethical challenges, including privacy infringement, consent issues, technological reliability, and data security. Balancing these benefits and risks is crucial in deciding the extent to which such systems should be employed.

SECTION 7 | CENTRALISED TRAFFIC LIGHT SYSTEM

A centralised traffic light system is a structured approach to traffic management in urban areas, where all traffic signals are controlled from a single, central location. This system is based on the principles of centralised control systems, which are characterised by centralised decision-making and management. Here's an explanation using points from the provided webpage:

Key Features of a Centralised Traffic Light System

Centralised Decision-Making | The core of a centralised traffic light system is a central control unit that manages all traffic signals in the area. This unit processes data from various sources and makes decisions about traffic light timings and sequences.
Uniform Control and Coordination | All traffic lights are synchronised and coordinated from the central unit, ensuring uniform traffic flow and reducing the likelihood of traffic jams and delays.
Efficient Monitoring and Management | Centralised systems allow for efficient monitoring of traffic conditions and quick response to changes, such as adjusting timings during peak hours or in response to traffic incidents.
Simplified Communication Structure | Communication occurs primarily between the traffic lights and the central control unit, simplifying the network's architecture and reducing the complexity of communication links.
Scalability Challenges | While centralised systems are easier to manage, scaling them up to accommodate more traffic lights or larger areas can be challenging and may require significant infrastructure upgrades.

Contextual Implementation

Traffic Efficiency | The system can optimise traffic flow across a larger area, reducing congestion and improving travel times.
Emergency Situations: In emergencies, the central control unit can quickly modify signal patterns to clear paths for emergency vehicles.
Data Analysis and Planning | The centralised unit can collect and analyse traffic data, aiding in traffic planning and infrastructure development.

Challenges and Considerations

Complexity in Large Networks | Managing a large network of traffic lights from a single point can become complex and challenging.
Dependence on Central Unit | The system's effectiveness is heavily reliant on the central unit's performance. Any failure in the central unit could impact the entire network.
Limited Flexibility |Centralised systems may lack the flexibility to adapt quickly to local traffic conditions at individual intersections.
Cost and Infrastructure | Establishing and maintaining a centralised traffic control system can be costly, requiring substantial investment in control centers and communication infrastructure.

A centraliSed traffic light system offers a structured and unified approach to traffic management, ensuring coordinated control of traffic signals. However, it also presents challenges in terms of scalability, flexibility, and dependency on the central control unit, making it crucial to weigh the benefits against potential limitations in urban planning contexts.

1: Describe the role of sensors in a centralised control system. [4]
2: Explain the concept of a feedback loop in a control system. [6]
3: Highlight ethical considerations that arise from the implementation of centralised control systems in society. [4]
4: Give an example of a centralised control system in everyday life and explain its components.[2]
5: How do analog-to-digital converters (ADCs) function in a control system? [4]
6: What role do actuators play in a centralised control system? [4]
7: Discuss the importance of microprocessors in centralised control systems. [6]
8: Identify and describe two input devices commonly used in centralised control systems. [6]

ALSO IN THIS TOPIC

CENTRALISED CONTROL SYSTEMS
DISTRIBUTED CONTROL SYSTEMS
TOPIC 7 REVISION
KEY TERMINOLOGY
TOPC 7 ANSWERS