I'm exploring building a machine using the Centroid Acorn with Clearpath SDSK motors and the Hitachi WJ200 VFD. Centroid provides a reference design for the safety circuit, but on first glace it looks fairly rudimentary. I've attached it below. I'd be interested in hearing people's thoughts on this approach. The basic idea is to use an e-stop switch to drop the "enable" lines coming from Acorn to the motors and to alert Acorn by opening a "not happy" port. Clearpath provides some general guidance about this. They state that "When Enable is de-asserted power to the motor coils is removed and themotor cannot respond to user inputs. Exception: when ClearPath is set to “Spin on Power Up” mode, the motor shaft can moveas soon as main DC power is applied, regardless of the state of the Enable Input.ClearPath motors never ship configured in this mode." Later they say: "The Enable Input is not designed for safety compliance use.Main power must be removed to ensure safety." I'm assuming that the warning about not using the enable line for safety is related to the "Spin on Power Up" mode -- but they don't make this clear. Is it ok to to use e-stop to de-assert the enable signal so long as the Spin Up on Power mode is not used?
Its also not clear to me what Acorn is doing with the VFD. In the case of the Hitachi VFD, there is a two-line gate suppress function. If either of these lines drops out, Hitachi cuts power to the motor. It would seem that I could configure two Acorn outputs to drop out on e-stop. Would this be an acceptable approach? .
The circuit also fails to provide a hardware reset -- but Centroid software provide a software reset. Is this enough?