Proceedings of the RINA 5th International Conference on Ship and Offshore Technology ICSOT 2017 December 7-8, 2017, IIT Kharagpur, India ICSOT2017-42 HORIZONTAL PLANAR MOTION MECHANISM (HPMM) INCORPORATED TO THE EXISTING TOWING CARRIAGE FOR SHIP MANOEUVRING STUDIES Akhil Balagopalan Department of Ocean Engineering Indian Institute of Technology, Madras Chennai, India. 600036 Email: bgakhil@gmail.com Kunal N. Tiwari Department of Ocean Engineering Indian Institute of Technology, Madras Chennai, India. 600036 Email: kt@fourier.in P Krishnankutty Department of Ocean Engineering Indian Institute of Technology, Madras Chennai, India. 600036 Email: pkrishnankutty@iitm.ac.in ABSTRACT Planar Motion Mechanism (PMM) equipment is a facility generally attached with Towing Tank to perform experimental studies with ship models to determine the manoeuvring charac- teristics of a ship. Ship model is oscillated at prescribed am- plitude and frequency in different modes of operation while it is towed along the towing tank at predefined speed.The hydrody- namic forces and moments are recorded, analyzed and processed to get the hydrodynamic derivatives appearing in the manoeu- vring equations of motion of a ship. This paper presents the de- tails about the Horizontal Planar Motion Mechanism (HPMM) equipment which is designed, developed and installed in Towing Tank laboratory at IIT Madras. NOMENCLATURE r Yaw velocity. u Surge velocity. v Sway velocity. x E Position in x-direction. y E Position in y-direction. y a Sway amplitude. x s Distance between load cell mounting and midship. β Drift angle. ψ Euler angle for rotation about z-axis. ψ a Yaw amplitude. 1 INTRODUCTION Manoeuvring quality assessment for ships are essential for the navigational safety purpose.International Maritime Organisa- tion (IMO) has prescribed safety guidelines for the sea going ves- sels to ensure its navigational safety and operational efficiency. Manoeuvrability of ships depends on the and the effectiveness of rudder or other control devices.The accurate prediction of manoeuvring behaviour of the vessel has to be done at design stage itself. Directional stability and control characteristics of ship are understood by solving the manoeuvring equation of mo- tion, for which the knowledge of hydrodynamic derivatives are essential.The quality of manoeuvring behaviour prediction relies on the accuracy at which the hydrodynamic derivatives are es- timated. The hydrodynamic derivatives are usually determined by theoretical, numerical or experimental methods. Empirical relations provided by researchers such as M Hirano et al. [1], Kijima et al. [2] gives a rough estimate of the hydrodynamic derivatives but fails to predict non linear and coupled derivatives accurately. More reliable values can be obtained only by con- ducting captive model testings on ship models, of which Planar Motion Mechanism is the widely used one. Planar Motion Mech- anism (PMM) pioneered by Gertler and Goodman et al(1962) [3] is considered to be the major outbreak for captive model test- ings in ship manoeuvring area. Large amplitude planar motion mechanisms installed around the world in early years of 1980s provided much more enlightenment in ship motion predictions. PMM facility installed in a towing tank enable us to perform the dynamic tests in pure sway, pure yaw and combined sway and yaw modes of model oscillations. These dynamic tests provide 1 Copyright c  2017 by RINA