MATLAB: Is there ‘Multiply by -1’ operation in demo models under Target Support Package TC2 (R2008a)

Question

In the demo models "Simulation of FOC using PMSM Model" and "Permanent Magnet Synchronous Motor Field-Oriented Control" under Target Support Package TC2, the 'Speed Control' and 'c2812pmsmsim/Scaling/multiply by -1' subsystems respectively have an '-1' multiplication operation with the 'IQN' blocks.

There is no documentation that explains such an operation and I am not able to find any literature outside MATLAB in regards to such an operation. Please explain.

ReproductionSteps:

1) Open the demo 'c2808pmsmsim.mdl'

2) Go to subsystem 'c2808pmsmsim/Scaling/multiply by -1/' and observe the constant block with value '-1'

Answer 1

Documentation on the 'multiply by -1' operation for the these 2 demo models under Target Support Package TC2 (2008a) is missing from product and manual.

Here is additional information on this matter:

The speed variable is signed. A positive value means one direction while

negative means the other direction. Speed is just the derivative of the position signal, and can be interpreted either way.

The convention used on the generated code is different than the one used for simulation by the SimPowerSystems blocks. Therefore, it is necessary to introduce a -1 in one case in order to be able to reproduce the same behavior in simulation and code generation.