The automated control of a process or a condition by a digital device is referred to as direct digital control, digital and analog converters gather all instrumentation and signals to the central controller are transported by the network. A centralized computer causes actions to be sent by following all its production rules through a common network to actuators, and valves.
The control entails collecting and measuring data, information processing and finally controlling the action, the elements of a digital control system include the controller, sensors, the data types, and the control loop.
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The controller does the comparison of a set of instructions with the input, required action, and throttle range. Finally, the controller brings forth the output signal that causes the action that is required for the condition satisfaction ( Zavadsky, 2017).
Measurement of controlled inputs and controlled mediums in an accurate and repeatable manner is performed by the sensor, they measure pressure, temperature, humidity, fluid flow, electrical demand condition, fire, time of the day, airflow, and low/high limits ( Lyly-Yrjänäinen, 2016).
Data types are analog, accumulating and digital. Analog data appear in a decimal or numeric number showing electrical variations of the input. Likewise accumulating data is in numeric and decimal number which is obtained from a sum of given functions.
The interaction of the controlled devices, the sensors, and the controller is known as a control loop. For instance, an indoor air temperature regulation. The indoor air temperature and the data outputs are measured by the sensor.
The direct digital control logic is programmed using three common approaches, they include, line programming, graphical and menu-based programming. Basic or FORTRAN languages along with HVAC are used in line programming systems.
Menu-driven programming involves the use of common HVAC logical function's template, they contain parameters for the functioning of each program block. The flow of data is connected to each template; this kind of programming requires less experience.
Benefits of Direct Digital Control Systems
Direct digital control systems lead to increased control efficiency and improved control effectiveness and finally energy efficiency.
Improved Effectiveness
DDC leads to effective HVAC control systems since it provides more accurate data, as electronic sensors accurately measure humidity, temperature, pressure, and airflow. DDC is also far more flexible to schedule reset changes since the logic of control loop is available. With DDC one can implement energy-saving features, use more complex strategies and perform system optimization since cost associated with change is low.
It is usually easier to integrate DDC system into other computer systems, it can also integrate into lighting control systems, fire control systems and management systems ( Lyly-Yrjänäinen, 2016).
Improved Operational Efficiency
Most DDC systems have the ability to have alarms routed to various network locations, it allows engineers to control problems by troubleshooting the system. They also allow for various data format visualization and the data can also be used for trend analysis. It also allows multiple users to troubleshoot problems. The design engineer, control vendor, and the authority can all visualize and diagnose a problem. In addition, direct digital control systems are easy to maintain.
Increased Efficiency
There are energy-efficient routines added as a result of the use of more complex mathematical functions that are used with DDC. It can be used to implement strategies such as limiting and monitoring of demand. In addition, DDC ensure maximum coordination of systems within a facility. DDC systems also ensure convenience in security systems automation by use of motion sensors ( Bessa, 2017).
Direct digital control systems are able to perform system diagnostic functions, energy management, and controls, they are more accurate and reliable.
References
Lyly-Yrjänäinen, J., Holmström, J., Johansson, M. I., & Suomala, P. (2016). Effects of combining
product-centric control and direct digital manufacturing: The case of preparing customized hose assembly kits. Computers in Industry , 82 , 82-94.
Bessa, I., Ismail, H., Palhares, R., Cordeiro, L., & Chaves Filho, J. E. (2017). Formal non-fragile
stability verification of digital control systems with uncertainty. IEEE Transactions on Computers , 66 (3), 545-552.
Zavadsky, D., & Hebert, T. G. (2016). U.S. Patent No. 9,450,689 . Washington, DC: U.S. Patent
and Trademark Office.
