The combination of logic control and ability to execute a simulation language was unique. Now PsxCad offers the same, but no software is offering it for the same low price.

When making a trainingsimulator a special mix of analogue and logic control must be combined with expressing the laws of nature. HCADwin offers an unique combination of those fields.
The standard user restricts himself to the drawing and testing of the control. This aspect of testing the logic in the drawing environment will boost the quality of drawing. But HCADwin offers more.

When inspecting sophisticated simulation languages like MATLAB™ and SIMULINK™ the lack of handling the normal logic control and the integration of analogue control within the domain of the physical modelling reflects a way of mathematical thinking.
The flexibility and numerical solving power is obvious, but handling the problem as a single entity also creates numerical or performance problems. To be able to transform a problem into a totaly different domain is useful for investigation, but logic control is not very suited to be executed in other than the normal time and sequential domain. But in normal practice the control will be executed in a fixed time. This time step will not reflect the most suited (or variable) time step for the modelling domain.
HCADwin uses another approach: the analogue and logic control are developped in a graphical manor and executed with a fixed frequency of 10Hz. This reflects the real systems like a PLC or DCS.
The physical model is just a symbol (HSL container) within this logic, but can be executed more often to accomodate the eigen values of the modelled process. The HSL frequency is therefore restricted to a multiple of the enforced 10Hz. Within this HSL only a single algoritme for solving the differential equations is available. It will not be a surpise that it is a fixed time step algoritme to guarantee the trainingsimulator context of performing in real time. By using the HSL container with the normal logic, the execution of the logic and HSL is synchronized without any effort and by changing the order of symbols, the engineer can predict the outcome.
When loading or saving sessions all variables form a single entity. This ensures that after loading a session, the very first calculation continues exactly from the point it was saved. No seeking for a stationairy working point due to forgotten memories like the integral part of a PID-controller.
The HSL model will accept the valve positions as fixed model boundaries during calculations. No control algoritme is included here to smooth the outputs of the normal HCADwin control. The HSL should be able to do the calculations to satisfy the measurements (DCS inputs) for the next 100 milliseconds.
When valve positions and measurements are overruled by an instructor to create some scenario of problems, the integraty of the HSL model remains intact. A disturbed valve position is equivalent to some error in the valve. It could happen and the HSL model should calculate the normal respons to that.
When a measurement is overruled, it will reflect an error in the instrument. The control reacting on wrong information, but in itself it remains fully functional in the way it was engineered.
When mixing the control and the physical modelling both domains will suffer and the degradation of integrety in unavoidable.

The PTD (Process Timing Diagram) is unique for HCADwin. Learn more about it if you want to decrease your number of instructions to a mere 10% while increase the quality, readability and ease to commission by a factor 5.
It has all to do with the paradigme shift I learned in the field of industrial automation and making training simulators. Boolean logic is overrated! Use enumerations instead. And reposition the equipment from the sun to a planet, and the process from almost absent and hidden to the central focus point. In your thinking the equipment must revolve around the process. Now the representation of that process is identical for its designer, the control and the operator.
Using HCADwin to experience that is worth trying.