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8 Advanced Applications Information
8.1Using Closed Loop Control
8.1.1What is Closed Loop Control?
Closed loop control is widely used in industrial applications to control a broad variety of processes. Control engineering is a complex subject, but a simple closed loop control uses a feedback signal from the process (such as temperature, pressure, speed) a desired value from a set point (often set manually) and a control system that compares the two and derives an error signal. The error signal is then processed and used to control the inverter and motor (in this case) to try to reduce the error.
The error signal processing can be very complex because of delays in the system. The signal is usually processed using a Proportional, Integral and Differential (PID) calculator, and these parameters can be adjusted to optimize the performance and stability of the system. Once a system is set up and stable, very efficient and accurate control can be achieved.
8.1.2Closed Loop Control using MICROMASTER MM420
A standard PI control loop function has been incorporated in the MICROMASTER MM420, requiring only the connection of a suitable feedback transducer, and configuration of parameters.
The control loop is not suitable for fast response control systems, but is ideal where the controlled variable changes slowly, or where transient errors are not critical (for example temperature or pressure control).
Note.
The system is not intended specifically for speed control but can be used in this way, provided fast response is not required. Where fast response and accuracy are critical, external PID control systems or higher performance Siemens inverters should be considered.
The following information relates to MM420 parameters and closed loop functionality.
MICROMASTER Applications Handbook | 47 |