Is a system with feedback better than an open-loop system?
No, not necessarily. Both systems have their advantage and disadvantages. Open loop systems are usually faster and require less tuning when loads are varied. They are more predictable in their dynamic behaviour. Closed loop systems may be capable of compensating external influences. NSI has chosen to use primarily open loop stepper motor systems. The reason for this is that stepper motor systems do not require tuning of feedback parameters and are very predictable in their state (position, speed, acceleration). In order to verify that during a measurement a series of steps were missed, one can use the drift check which ensures that the AUT and/or probe can return to the exact location as that it started from. In cases where there are external factors that may influence the position of an actuator (like temperature that makes that a linear slide expands so that a step on a stepper motor no longer equals a known displacament), we can apply a feedback system on top of our stepper motor sy
