Moving towards the maximum speed in stepping motors by means of enlarging the bandwidth of the current controller

Abstract

This paper pursues to maximise the mechanical speed when using stepping motors (SM) without position sensors in order to achieve a rapid-response manufacturing whenever any equipment based on such electrical machines is involved.The novelty of this paper is the fact that not only the bandwidth of the current controllers is improved for such maximization of the SM mechanical speed, as traditionally done in previous works, but also a comprehensive approach has been addressed. Such global approach starts justifying why the traditional PI controller is not sufficient and it includes the analytical tuning of the current controllers, considering implementation tiny issues (but of paramount importance) such as the delays caused by the processor and the sample and hold current measurements. It is proved and justified that this previously mentioned issues, which are often omitted, play a crucial role when trying to maximise the speed of the SM, since the electrical fundamental frequencies of the SM move close to the sampling frequency. Therefore, the analytical process to tune and implement the current controllers will have to be done in discrete-time domain, i.e. using the Z transform and treating the SM drive as a sampled data system.Experimental waveforms and results based on real prototypes will prove the validity of the entire research.Finally, a real case-study based on Printed Circuit Board (PCB) prototyping machine which is composed by two stepper machines, is fully reported. Such PCB prototype is the fruitful collaboration between the University (research institution) and a private company (industry).