Induction motors with two degrees of freedom are unconventional drives offering broader possibilities of different movements than traditional drives. There is general opinion that construction of a machine with 2 degrees of freedom (2DoF machine) is much more complicated and expensive than a machine with one degree of freedom. In the paper the authors show that it is possible to construct in easy way (even in an university laboratory workshop) a 2DoF 2-module induction motor using components of a factory-manufactured 3-phase squirrel-cage motor. The presented solution is one of many possibilities and should be treated as the exemplary case elaborated and tested at the Silesian University of Technology in Gliwice.
Purpose -The main purpose of the paper is to develop model basing on the modified and properly-adopted Fermi-Dirac equation which combines proper accuracy with adequate simplicity as well as to show how steady state and transient curves resulting from this model can be applied for solving design task. Design/methodology/approach -The standard Fermi-Dirac equation was modified and extended. Full performance cycle for the SMA actuator was characterized by double-valued function describing the actuator activation and the actuator deactivation. All these functions and parameters can be easily determined by analysis of measurement data or with use of Hooke-Jeeves optimization algorithm. Findings -SMA linear actuator can be used in mechatronic systems as a special non-standard drive when ultra-light mass and very simple mechanical construction of power feed system is required. The proposed steady-state and transient performance curves as well as operation diagram constitute sufficient base for effective designing SMA drive systems.Research limitations/implications -The greatest disadvantage of a SMA actuator is long time of deactivation resulting from slow self-cooling process. As far as efficiency is concerned as essential factor for choosing the most suitable linear actuator, there is no sense to take into account a linear SMA actuator because of its very low efficiency. Practical implications -Designer can use performance curve which determines proper length of SMA actuator and range of its motion. The proposed model can be implemented in SMA drive control unit for controlling position of the actuator. Originality/value -Similarities between change of martensitic phase during transition process and probability P of electron energy level distribution described by the Fermi-Dirac two-variable equation were taken into account. Such an approach seems to express in the most suitable way the physical nature of m-a transition. The authors decided to extend concept (proposed in Jayender et al.) and to adopt the Fermi-Dirac equation for describing behaviour of a SMA linear actuator.
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