How to optimize using DRESP3 response ?

Hello everybody,

          I used Optistruct to perform a simple parameter optimization. I need to extract the average corner stress of a certain node as a constraint. Minimum mass as objective function.

          So I came up with the idea of using DRESP3 response to extract through OML scripts. Extract average corner stress data by using the readcae3d statement in OML. When I set everything up, there was an error running the program. The return value of DRESP3 is 0, indicating an issue in the OML script. But there is only one readcae3d instruction in the statement.

         I guess it's because the h3d file during optimization is protected, and the readcae3d statement in the oml script cannot extract corner stress data in real-time from the h3d file, resulting in a return value of 0 for DRESP3.Do anyone know what caused this ？If that's the case, what should I do? How can I extract the corner stress data of a node as a constraint every iteration?

Thanks you very much in advance,

Best regards,

yuankun