Advantages and Disadvantages of Digital control system

Advantages of Digital control:

  • It gives better resolution

  • Coding of digital signal and digital communication: The entry of digital control to the industrial scenario was chiefly through the big process industries like steel mills, chemical, fertilizer and cement industries because of the cost advantage.

  • Time sharing: One communication channel may be used to transmit discrete control signal for more than one control systems.

  • Control system with inherent sampling: Sampling is inherent in some applications, and it is necessary in other applications, it is desirable for still other applications.

  • Digital computer implementation of sophisticated control law: Dedicated minicomputers and microprocessors can be used to implement sophisticated algorithms such as high-performance state variable manipulation, Kalman Filtering and Adaptive control.

  • System design: For some control system application, better system performance may be achieved by a sampled data control system design. For a continuous system the differentiator, not only may enhance the existing noise but may also be a source of additional noise. In a sampled data system, the differentiating action can be implemented by a digital computer without increasing system noise problem.

Disadvantages of Digital control:

  • System design: The mathematical analysis of a digital controller is sometimes more complex and more tedious as compared to continuous data control systems.

  • System stability: System stability is degraded by converting a continuous data system to digital system. Even a stable second order system can be unstable when converted to discrete version.

  • Loss of signal information: The signal output from the digital controller is to be converted to analog form before applying to the actuators. However, the reconstruction of digital to analog signal using hold circuits is only an approximation of the actual signal. So, some signal information is lost in the process.

  • Controller dynamic update: Analog to Digital (A/D) and Digital to Analog (D/A) converters along with digital computer introduce some time delay.

  • Software errors: The complexity of the controller is in the software implemented algorithms, which may contain errors