# MFC/IMC Control Algorithm for Reduction of Load Torque Disturbance in PMSM Servo Drive Systems
## 6 Conclusions  
In this paper, the authors introduced the MFC/IMC algorithm for velocity control of PMSM. The numerical analysis of a linear system in frequency domain shows that the presented MFC/IMC structure is much more insensitive to disturbances at the plant input. The experimental results prove that the exploitation of MFC/IMC scheme in servo drive system reduces the influence of load torque disturbances compared to the classical cascade control structure. Measured reference and actual velocity signals of PMSM during conducted tests indicate explicit improvement in load torque reduction by the MFC/IMC scheme. Additionally, the calculated performance indices show a substantial difference between both control structures in favor of the new method. The above factors lead the authors to believe that introducing the MFC/IMC algorithm in cascade velocity control significantly improves the servo drive's insensitivity to external torque disturbances. This, in turn, is highly beneficial in any application where a precise execution of the desired path is required, e.g., CNC milling, robotics. Moreover, the implementation of MFC/IMC algorithm is feasible in commonly utilized servo drives for industrial applications. There is no need to modify existing classical cascade control structure. The algorithm can be easily applied in open-structure control systems while employing such techniques like rapid prototyping and PLC code generation without dedicating too many resources. The proposed Model Following Control algorithm requires a model of the object to generate an additional control signal. In this paper, the authors exploited a nominal linear model of the PMSM motor. One of the advantages of the MFC/IMC algorithm is that the model itself does not need to be accurately identified. Precise identification allows to generate a more \"suitable\" additional control signal, but in many cases, it is not required as long as the signal's value remains within the operating range of the controlled device. One of the disadvantages of the proposed control method is the lack of explicit \(R_{\Delta}(s)\) controller tuning procedure. Although the controller used in the article was tuned with the assumption: \(|R_{\Delta}(s)|>|R_{\omega}(s)|,s=j\omega,\omega\in[0,\infty)\), it is only a general recommendation. The \(R_{\Delta}(s)\) tuning is scarcely described in the literature leaving the field relatively unexplored. Another drawback of the MFC/IMC algorithm is the need to develop an elaborate model for more complex applications. For example, applying this algorithm in CNC motion control may demand the modelling of a feed drive which can itself be a challenging task. One should also be aware that some trade-offs in model's complexity may be necessary if it is to be implemented in the CNC control system. The effectiveness of the presented MFC/IMC algorithm possibly could be improved. The authors currently conduct new simulation experiments that utilize the piecewise affine models and sets of controllers in the correction block. The first results are promising, but more work is needed to be undertaken to confirm the usefulness of this new approach. Conceptualization, K.P. and P.W. ; Data curation, P.W. and M.K. ; Formal analysis, K.P. and P.W. ; Funding acquisition, K.P. ; Investigation, K.P., P.W. and M.K. ; Methodology, K.P. and P.W. ; Project administration, K.P. ; Resources, K.P. ; Software, M.K. Supervision, K.P. ; Validation, K.P., P.W. and M.K. ; Visualization, P.W. ; Writing--original draft, K.P. and P.W. ; Writing--review & editing, K.P. and M.K.