The servo drive has an error/reset pin to initialize and reset error conditions. We will simply place a momentary contact normally open button on it which has to be pressed to initialize the drive, and if an error occurs it can be pressed to reset the drive. For testing, I'm using a micro pcb switch type button mounted in the servo drive terminals. When powered on, the servo drive does not energize the motor, until the reset button is pressed. If a position error occurs, that drive will shut down (others may continue running), until the reset button is pressed. Of course, when the controls are enclosed the buttons will need to be accessible whenever the machine is turned on. And sometimes you'll want to be able to see the lights on the motor driver during testing and tuning.