A closed-loop control system, also known as a feedback control system, is a type of control system in which output is measured and compared to a desired or reference value. Based on this comparison, corrective actions are taken to adjust the system’s behavior and minimize any deviation from the desired output.
The design of closed loop control systems is comparatively more complex than open loop control system. Given below are 10 examples of closed loop control systems.
Contents
Thermostat Heater
The thermostat heater is an example of closed loop control system. The thermostat senses the temperature of the system and maintains the temperature.
- Input: Desired temperature setpoint
- Output: Actual temperature measured by the thermostat
- Plant: The heating system (heater)
- Controller: The thermostat
In a thermostat heater system, the desired temperature set point serves as the input, indicating the temperature the user wants to maintain in the room. The output is the actual temperature measured by the thermostat. The plant in this system is the heating system itself, which includes the heater. The controller is the thermostat, which continuously monitors the actual temperature and compares it to the desired set point. If the actual temperature deviates from the set point, the thermostat sends a signal to the heating system to adjust the heat output accordingly. For instance, if the actual temperature is lower than the set point, the thermostat signals the heater to increase the heat output. Conversely, if the actual temperature is higher than the set point, the thermostat signals the heater to reduce the heat output. This continuous monitoring and adjustment process maintain the room temperature close to the desired set point, effectively regulating the heating system as a closed-loop control system.
Sunseeker solar system
Sunseeker solar system is an automatic tracker which uses LDR to sense the sunlight. A microcontroller reads the LDR voltage and signals the connected motor which rotates the panel towards the sun.
Input
- Sunlight intensity
- Desired orientation of the solar panels
Output
- Actual orientation of the solar panels
Plant:
- Solar panels and associated tracking mechanism
Controller:
- Control algorithm/software
- Sensors for measuring sunlight intensity and panel orientation
- Actuators for adjusting panel orientation
The Sunseeker solar system utilizes a closed-loop control system to optimize the orientation of solar panels for maximum sunlight exposure. The input to the system includes the intensity of sunlight and the desired orientation of the solar panels, while the output is the actual orientation of the panels. The plant consists of the solar panels themselves and the tracking mechanism responsible for adjusting their orientation. The controller, which includes control algorithms and software, as well as sensors and actuators, continuously monitors the sunlight intensity and panel orientation. Based on this feedback, the controller calculates necessary adjustments to ensure that the panels are always facing the sun optimally. By constantly comparing the desired orientation with the actual orientation and making real-time adjustments, the Sunseeker solar system maintains maximum efficiency in harnessing solar energy. This closed-loop control system allows the solar panels to adapt to changing environmental conditions and optimize energy production throughout the day, ultimately maximizing the system’s overall performance and output.
Voltage stabilizer
The voltage stabilizer stabilizes the supply voltage in case of fluctuations. Modern voltage stabilizers utilize solid state electronic components which measure the fluctuation in voltage and reduce/increase (buck/boost) the voltage to the desired level.
- Input: Fluctuating input voltage.
- Output: Stable output voltage.
- Plant: The electrical system or load where the voltage stabilization is required.
- Controller: The device responsible for measuring the output voltage and adjusting the system to maintain stability.
In a voltage stabilizer system, the input is the fluctuating voltage from the power source, which could vary due to factors like fluctuations in the power grid or sudden changes in load. The output is the desired stable voltage required by the electrical equipment or appliances. The plant represents the electrical system or load that requires stable voltage.
The controller is the core component of the closed-loop control system. It continuously monitors the output voltage using sensors or feedback mechanisms. When the output voltage deviates from the desired level, the controller activates corrective measures to adjust the system and bring the voltage back to the set point. This adjustment could involve altering the transformer taps or changing the duty cycle of a voltage regulator.
Overall, the closed-loop control system ensures that the output voltage remains stable despite variations in the input voltage, thus providing a reliable power supply to the connected electrical devices. This stability is crucial for preventing damage to sensitive equipment and ensuring consistent performance in various applications, such as industrial machinery, telecommunications systems, and residential electronics.
Missile Launcher
- Input: Target coordinates or information
- Output: Adjusted direction and launch parameters
- Plant: Missile launcher system including the missile and its launch mechanism
- Controller: System responsible for processing input data and adjusting launch parameters
A missile launcher operates as a closed-loop control system, where it continuously monitors and adjusts its parameters based on feedback. The input to the system consists of target coordinates or information obtained from sensors or external sources. This input is processed by the controller, which calculates the necessary adjustments to ensure accurate targeting. The controller then outputs commands to the plant, which includes the missile launcher system itself. The plant adjusts the direction, angle, and other launch parameters of the missile based on the controller’s commands. As the missile is launched, sensors track its trajectory and provide feedback to the controller. The controller uses this feedback to further refine the launch parameters, ensuring that the missile accurately reaches its target. This closed-loop control system allows the missile launcher to adapt to changing conditions and improve the accuracy of its launches.
Auto Engine
The tachometer in auto engine generates a voltage proportional to the speed of the shaft. The voltage is subtracted from the input voltage to calculate an error voltage that provides information about current speed and desired speed. The error voltage is then used to arrange the throttle after amplification.
Inverter AC
The inverter air conditioner uses an inverter for controlling the compressor speed. Sensors measure the ambient air temperature and then adjust compressor to the required level.
- Input: Desired temperature set by the user.
- Output: Actual room temperature.
- Plant: The air conditioning system itself, including the compressor, condenser, evaporator, and fan.
- Controller: The inverter control system, which adjusts the compressor speed based on feedback from temperature sensors.
Explanation:
Inverter air conditioners operate as closed-loop control systems, where the desired temperature set by the user serves as the input. The system’s output is the actual room temperature, which is continuously monitored by temperature sensors. The plant in this context refers to the air conditioning system itself, comprising components such as the compressor, condenser, evaporator, and fan. The controller, which is the inverter control system, plays a crucial role in regulating the system’s operation. It adjusts the speed of the compressor based on the feedback received from the temperature sensors. If the room temperature deviates from the setpoint, the controller modulates the compressor speed to maintain the desired temperature, effectively closing the loop. This closed-loop control mechanism allows the inverter air conditioner to achieve precise temperature control and energy efficiency by dynamically adjusting its operation in response to changing conditions.
Automatic toaster
The automatic toaster measures the temperature, moisture vs dryness level of toast and adjusts the heat setting of toasts.
Input:
- Desired level of toasting (set by the user)
- Bread slices to be toasted
Output:
- Toasted bread slices
Plant:
- Toaster mechanism and heating elements
Controller:
- Thermostat or timer
In an automatic toaster, the user sets the desired level of toasting using a thermostat or timer, which acts as the controller. The input to the system is the desired level of toasting and the bread slices to be toasted. The plant, in this case, includes the toaster mechanism and heating elements.
When the toaster is turned on, the heating elements start to heat up. As the bread slices are inserted into the toaster, they absorb heat from the heating elements. The controller continuously monitors the temperature inside the toaster and compares it to the desired level of toasting set by the user.
As the temperature reaches the desired level, the controller signals the heating elements to turn off, preventing the bread from over-toasting. If the temperature falls below the desired level, the controller activates the heating elements again to maintain the desired level of toasting.
This process of continuously monitoring and adjusting the temperature based on the desired level of toasting represents a closed-loop control system. The controller ensures that the output (toasted bread slices) meets the desired specifications (desired level of toasting) by adjusting the input (heat) based on feedback (temperature monitoring).
Turbine Water Control System at power Station
In modern hydroelectric power stations, the level of water coming from the nozzles and gate is adjusted using automatic controls.
- Input: Water flow rate, turbine speed, power demand
- Output: Control signal to adjust turbine blades, generator output
- Plant: Turbine, generator, water flow system
- Controller: Control unit monitoring turbine speed and power demand, adjusting turbine blades
Explanation:
The Turbine Water Control System at a power station operates as a closed-loop control system, where feedback from the system is used to regulate its operation. Inputs to the system include parameters such as water flow rate, turbine speed, and power demand. The control unit continuously monitors these inputs and compares them to desired setpoints. Based on the feedback received, the controller generates control signals to adjust the position of the turbine blades, thereby regulating the flow of water through the turbine. This adjustment ensures that the turbine operates at the desired speed to meet the power demand while maintaining stability. The output of the system is the control signal sent to the turbine mechanism to position the blades accordingly. The plant consists of the turbine, generator, and the water flow system, where the turbine converts the kinetic energy of water into mechanical energy, which is then converted into electrical energy by the generator. Overall, the closed-loop control system of the Turbine Water Control System ensures efficient and stable operation of the power station by continuously monitoring and adjusting the turbine’s operation in response to changing conditions and demands.
Automatic Clothes Iron
The automatic clothes iron adjusts the required temperature for proper pressing. An automatic iron regulates the temperature of iron itself in such a way that the temperature for a cloth stays in specified temperature range.
- Input: Desired Temperature
- Plant: Automatic Iron
- Controller: Thermostat
- Output: Temperature
- Input: The desired temperature setting is the input to the system. It represents the target temperature at which the iron should operate.
- Process: The process refers to the iron’s heating element, which converts electrical energy into heat. The heating element is responsible for raising the iron’s temperature.
- Output: The output is the actual temperature of the iron. It represents the current temperature of the iron, which should ideally match the desired temperature.
- Sensor: The iron employs a temperature sensor, such as a thermostat, to measure the actual temperature of the iron.
- Controller: The controller is responsible for comparing the desired temperature (input) with the actual temperature (output) measured by the sensor. It calculates the error, which is the difference between the desired temperature and the actual temperature.
- Actuator: The actuator in this case is the control mechanism that adjusts the heating element’s power based on the controller’s instructions. It controls the heat generation in response to the error signal.
- Feedback: The feedback loop is established by the sensor, which continuously monitors the temperature of the iron. It provides the necessary information about the system’s current state.
Sequence of Work for Automatic Clothes Iron closed-loop control system:
- The desired temperature is set by the user, serving as the reference input.
- The temperature sensor measures the actual temperature of the iron.
- The controller calculates the error by comparing the desired temperature with the actual temperature.
- Based on the error signal, the controller sends instructions to the actuator, which adjusts the power supplied to the heating element.
- The heating element responds to the actuator’s instructions and either increases or decreases heat generation accordingly.
- The temperature sensor continues to monitor the temperature, providing feedback to the controller.
- The controller adjusts the actuator’s instructions based on the feedback, aiming to minimize the error and bring the actual temperature closer to the desired temperature.
- This feedback loop continues until the actual temperature matches the desired temperature, at which point the controller maintains the temperature by fine-tuning the heating element’s power.
A human traveling on the road
The human body itself is the perfect example of closed-loop control systems. He looks around for traffic and changes his position accordingly.
- Input: Information from the environment (e.g., road conditions, traffic signs, other vehicles).
- Output: Actions taken by the human (e.g., steering, accelerating, braking).
- Plant: The vehicle itself, along with its mechanical components (e.g., steering system, engine, brakes).
- Controller: The human driver’s brain and nervous system, interpreting input and sending commands to the plant.
A human traveling on the road can be conceptualized as a closed-loop control system, with various components interacting to maintain desired behavior. In this analogy, the input consists of sensory information received from the environment, including road conditions, traffic signs, and the presence of other vehicles. The human driver processes this input through sensory perception and cognitive interpretation. The controller, analogous to the brain and nervous system, generates output signals based on the interpreted input, determining appropriate actions such as steering, accelerating, or braking. These output signals are then sent to the plant, representing the vehicle and its mechanical components. The plant executes the commands received from the controller, translating them into physical actions that affect the vehicle’s motion. Feedback loops continuously monitor the vehicle’s state, providing additional input to the controller to adjust actions as needed. This closed-loop control system enables the human driver to navigate the road safely and effectively, responding dynamically to changing conditions and maintaining control over the vehicle’s trajectory.