Reaction type for Exoskeleton study

Hi,

I have interfaced a simple 2 link exoskeleton with its hip joint coinciding with human hip joint. And to assist human, I am providing a class called AnyKinEqSimpleDriver to exoskeleton hip joint which intends to assist the human model to lift up. But since, the exoskeleton is constrained with human at two nodes, it takes reaction type 'On' by default, and when I switch these reaction type 'Off', I get an error "Muscle recruitment solver: solver aborted due to singular kkt matrix". Please suggest on how to keep the reaction type Off and avoid this error

Hi,

How is the exoskeleton connected to the human at the two nodes? Are there some reactions that allow a kinetic connection between the human and the exoskeleton at those nodes?

Best regards,
Dave