L11

29/08/26 Sat 10:36am

Causal Modeling

A causal model has an explicit defined direction of calculation, every block receives one or more inputs, processes them and produces output.

$$\text{input}\to \text{model}\to \text{o/p}$$

Example:

Desired speed   --> Controller <--
                        |         |
                        |         |
                      Motor       |
                        |         |
                        |         |
                  Torque / speed --

Acausal Modeling

In acausal modeling a component is described by its physical equation and connection codes. The modeler does not initial define the input and output.

Example :

Battery <-> Converter <-> Motor
                            |
Body                        |
of the <-> Wheels <-> Gearbox
vehicle

Advantages of Acausal Modeling

1. Component reuse
2. Natural Representation:
   The virtual assembly resembles the architecture of the physical machine.
3. Multi-Domain Integration:
   Electrical, Mechanical, Thermal and Hydraulic components can be coupled in one model.
4. Automatic Equation handling:
   The environment assembles, simplifies and rearranges equations before simulation.
5. Bidirectional interaction:
   Loading feedback and conservation effect are expressed directly through physical connections.

Aspect	Causal modeling	Acausal modeling
Basic Representation	Directed input/output block	Physical components, equations and port
Direction	Fixed by modeler	Determine while simulation
Dataflow	one way	bidirectional
Applicability	Control, filtering, etc…	Physics based modelling, multidomain plant modelling
Reusability	not reusable	components are reusable
Platform	Simulink, Lab view	Simscape, Modelica, Altair