Hello everyone.
I was about to post this thread as a reply in some other thread but decided to open a new one so that it may be more readily available to those who may need it.
One drawback of regular step motors is the fact that they run in an "open loop" mode. That is, there is no way for the controller to be aware of the actual positions where the motors are in any given moment. It just keeps sending signals expecting the motors to move according to the signals sent to them. Among other reasons that´s why servos are the preferred choice for position accuracy. The key word is feedback.
Now then one of the major drawbacks for servos has always been the price tag attached to them as well as to the required peripheral equipment.Step motors with feedback encoders are supposed to be somewhere in the middle attempting to allow for low cost systems but accuracy similar to servos.
Note: among other limitations steppers achieve slower speeds and lower resolution than servos.
At some time in the past some of us used to attach encoders to the shafts of the motors so that our controllers could make any required adjustment to guarantee the precision. The newer motors simply make that unnecesary as they include them already.
For these new steppers the encoder feedback is used for two main purposes, speed stability and position monitoring. The result is that now the controllers are only responsible for sending the pulse signals to direct the movements as for them these systems behave as if they were open loop. In standard (old) systems the controller received the feedback signals and had to process them along with the position algorithms. In my opinion that´s one of the reasons those systems were (and still are) expensive and complex.
One question that may arise is that if it possible to use these motors with the regular drivers or that if these new controllers can be applied to standard motors.
In the first case it should be possible but it is necessary to remember that no feedback would be in effect so that steps might be lost.
In the second case, unless there is a way to overrride the feedback mode of operation a motor without feedback would be considered by the controller to be at still thus making the controller drive the motor to the maximum possible speed.
I hope this clarifies things a little.