*Article* **Electronic Constant Twist Angle Control System Suitable for Torsional Vibration Tuning of Propulsion Systems**

### **Jaroslav Homišin, Peter Kaššay, Matej Urbanský, Michal Puškár \*, Robert Grega and Jozef Kraj ˇnák**

Faculty of Mechanical Engineering, Technical University of Košice, Letná 9, 042 00 Košice, Slovakia; Jaroslav.Homisin@tuke.sk (J.H.); Peter.Kassay@tuke.sk (P.K.); Matej.Urbansky@tuke.sk (M.U.); Robert.Grega@tuke.sk (R.G.); Jozef.Krajnak@tuke.sk (J.K.) **\***Correspondence:Michal.Puskar@tuke.sk;Tel.:+421-55-602-2360

 Received: 28 August 2020; Accepted: 17 September 2020; Published: 18 September 2020

**Abstract:** Currently, grea<sup>t</sup> emphasis on reducing energy consumption and harmful emissions of internal combustion engines is placed. Current control technology allows us to customize the operating mode according to the currently required output parameters, while the tuning of mechanical systems in terms of torsional vibration is often ignored. This article deals with a semi-active torsional vibroisolation system using pneumatic flexible shaft coupling with constant twist angle control. This system is suitable, as it is specially designed, for the tuning of mechanical systems where the load torque has fan characteristics (fans, ship propellers, pumps). The main goal of this research is to verify the ability of an electronic control system developed by us to maintain the pre-set constant twist angle of the used pneumatic flexible shaft coupling during operation. The constant twist angle control function was tested on a laboratory torsional oscillating mechanical system. Presented results show that the proposed electronic control system meets the requirements for its function, namely that it can achieve, su fficiently accurately and quickly, the desired constant twist angle of the pneumatic flexible shaft coupling. It is possible to assume that the presented system will increase the technical level of the equipment where it will be applied.

**Keywords:** marine propulsion system; pneumatic flexible shaft coupling; pneumatic tuner of torsional oscillations; torsional vibration; semi-active vibroisolation; constant twist angle control; fan characteristics; model-based control; pneumatic bellows
