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Digital hydraulic piston pumps and motors have shown the potential of improving efficiency in hydraulic systems. Two independently controlled fast switching on/off valves are connected to each piston chamber and allows for optimal valve timing and independent piston control. Each piston chamber is only pressurized when necessary, resulting in losses that almost scale with motor and pump displacement. This simulation study investigates the potential of using digital hydraulic pumps and motors to increase efficiency in a hydraulic offshore auxiliary winch with a safe working load equal to 20000 kg. Onedigital hydraulic winch drive system and one conventional hydraulic winch drive system are simulated hoisting two different loads. The payload in the first load case is 18000 kg and the payload in the second load case is 4000 kg. The efficiency and control performance of the two different winch drive systems are then evaluated. The simulation results show that digital hydraulic winch drive systems have the potential of increasing efficiency of hydraulic offshore winches.

The offshore oil and gas industry has traditionally used hydraulically driven applications. Hydraulic systems are known to suffer from relatively low efficiency. Due to environmental issues, more efficient systems are now required. Today, the offshore oil and gas industry is experiencing a shift in driveline systems; high efficient electric motors tend to replace low efficient hydraulic systems. In addition to the electric motors, a new alternative to the conventional hydraulic system is digital hydraulic machines. This paper investigates the feasibility of using a digital hydraulic winch drive system and presents a new digital hydraulic winch drive control system. The simulated system is based on a 20000 kg hydraulic offshore auxiliary winch with a drum capacity of 3600 m of wire. The digital hydraulic winch drive system is a closed-circuit system with one high-speed digital pump and one low-speed high-torque digital motor. One of the biggest challenges in digital hydraulic pump/motor technology is the fast switching on/off valves. The valvesmust have high durability, low power consumption, zero leakage and low response time. The on/off valves in this study are modeled with an ideal behavior. The simulation results show that the payload follows the reference trajectory when using a digital hydraulic winch drive system for a wide range of loads and speeds.