Study of The Cycloidal Curves and The Application in Hydraulic Motor Design

The research described in this paper is a part of the design and development of a compact and high-torque hydraulic motor for robotic arms.Traditional motors are too bulky to be installed on robotic arms.This paper presents new designs of hydraulic motors based on cycloidal curves.It presents the mathematically detailed generation of both epicycloidal and hypocycloidal curves, including the standard, shortened, and modified cycloids, for cycloidal gears and corresponding pin gears.The innovative design of hydraulic epicycloidal and hypocycloidal motors (also known as orbital motors) was described, including designs of gears and the oil distribution system.The comparison with traditional orbital motors is discussed, and the advantages of the new design, including compact size and high precision, are highlighted.A hydraulic motor for a subsea robotic arm was designed as a real industrial design case.Compact size, high output torque, and smooth spinning at low speeds were needed.The method presented was used to make an orbital motor with seven teeth on the inner gear.The designed motor was installed on a subsea robotic arm and has been operating in a subsea environment for over a year.This design case completely proves that the theory and design method proposed here are effective.