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A key topic discussed in the energy industry has long been how to steadily convert tidal energy into mechanical energy and then electrical power. Gear transmissions are widely used in mechanical systems for electrical power production, converting low-speed input rotation into high-speed output rotation to drive a generator rotor. However, to achieve a large speed ratio and stepless speed change, gear transmissions must be accompanied by complex structures and high-precision manufacturing technology. The application of gear transmissions in tidal energy power generation must therefore come at a high cost. A large speed ratio and stepless speed-changing capability are precisely the two essential elements of the mechanical system for tidal energy power generation. In this paper, a new type of speed-increasing CCHMT has been proposed that is capable of achieving large transmission ratio speed change between the blade rotor input and the generator rotor output. It is also capable of changing the input speed steplessly into a stable output speed suitable for power generation and for high-quality electric power production. To verify the feasibility of using a speed-increasing CCHMT in tidal energy, a simulation model has been established for the wave power at the input end. With the assistance of a volumetric speed-control system and hydraulic accumulator, the speed-increasing CCHMT can stably transmit disordered input speed. Simulation results show that the output rotational speed gained a stable amplification ratio within 20 and 30. The mean square error of the rotational speed was controlled to within 29 and the output speed is limited within 85% to 115% of the average output speed, thus ensuring the quality of power generation.

Heavy duty vehicles, especially special vehicles, including wheel loaders and sprinklers, generally work with drastic changes in load. With the usage of a conventional hydraulic mechanical transmission, they face with these problems such as low efficiency, high fuel consumption and so forth. Some scholars focus on the research to solve these issues. However, few of them take into optimal strategies the fluctuation of speed ratio change, which can also cause a lot of problems. In this study, a novel speed regulation is proposed which cannot only solve problems above but also overcome impact caused by speed ratio change. Initially, based on the former research of the Compound Coupled Hydro-mechanical Transmission (CCHMT), the basic characteristics of CCHMT are analyzed. Besides, to solve these problems, dynamic programming algorithm is utilized to formulate basic speed regulation strategy under specific operating condition. In order to reduce the problem caused by speed ratio change, a new optimization is applied. The results indicate that the proposed DP optimal speed regulation strategy has better performance on reducing fuel consumption by up to 1.16% and 6.66% in driving cycle JN1015 and in ECE R15 working condition individually, as well as smoothing the fluctuation of speed ratio by up to 12.65% and 19.01% in those two driving cycles respectively. The processes determining the speed regulation strategy can provide a new method to formulate the control strategies of CCHMT under different operating conditions particularlly under real-world conditions.