Component category for hydraulic drive systems integrated into industrial machinery. Includes hydraulic equipment such as hydraulic pumps, hydraulic cylinders, hydraulic valves, hydraulic motors, accumulators, hydraulic filters, pressure gauges, and flow control valves. Used as drive units for press machines, injection molding machines, machine tools, and construction machinery to achieve high-power, high-precision power transmission. Distinguished from electric actuators and air cylinders, specialized in fluid power equipment using hydraulic oil as the medium.