What Is a Block Diagram?

A block diagram consists of blocks that represent different parts of a system and signal lines that define the relationship between the blocks. Block diagrams are used in engineering areas such as feedback control theory and signal processing. A block within a block diagram may define a function, an operation, or a model in itself.

Block diagram of mathematical model.

Block diagram representation.

Use Block Diagrams to Graphically Represent Dynamic Systems

Block diagrams are widely used by engineers for controls, signal processing, communications, and mechatronics. Engineers build and use block diagrams to:

  • Provide a high-level graphical representation for a mathematical model of real-world systems, as in the figure below.
  • Understand the relationship and interdependencies among different parts of a system, such as a house heating system.
  • Analyze dynamic system behavior in time and frequency domains.
Block diagram in Simulink.

Block diagram representing an airframe model in Simulink.

Engineers rely on the Simulink® environment to efficiently build and simulate block diagrams for multidomain systems. This environment provides:

  • A graphical editor for building and managing hierarchical block diagrams
  • An extensive set of block libraries and templates to design block diagrams
  • Solvers to simulate a range of systems, including continuous-time (analog), discrete-time (digital), hybrid (mixed-signal), discrete-event, and multirate systems

For details on modeling and simulating block diagrams, see Simulink.

Block Diagrams in Simulink

Simulink is a graphical modeling and simulation environment for static and dynamic systems. You can create block diagrams, where blocks represent parts of a system. You can connect blocks to other blocks to form systems and represent more complex functionality.

The primary function of Simulink is to simulate behavior of system components over time. In its simplest form, this task involves keeping a clock, determining the order in which the blocks are to be simulated, and propagating the outputs computed in the block diagram to the next block.

At each time step, each block computes its outputs from its inputs. Once all the signals in a diagram are computed at a given time step, Simulink determines the next time step (based on the model configuration and numerical solver algorithms) and advances the simulation clock. Then each block computes their output for this new time step.

Software Reference

See also: Simulink, modeling and simulation, simulation software, Bode plot, control design software, linearization, parameter estimation, PID control, PID tuning