This example shows an oscillating hydraulic mechanism that consists of a single-acting hydraulic rotary actuator, winch, flow control valve, two-position electro-hydraulic valve, and power and control units. The mechanism maintains oscillating vertical motion of the weight by raising it to 25 cm and then allowing it to fall. To raise the weight, the electro-hydraulic valve is energized and connects the power unit to the hydraulic actuator inlet. As the weight reaches 25 cm the valve is deenergized, connecting the actuator chamber to tank.
The plots below shows the behavior of the rotary actuator. The load rises much faster than it falls under the influence of gravity. Looking at the flow rate into and out of the rotary actuator, we see that fluid enters much faster than it exits, resulting in different speeds during the cycle. The last cycle is interrupted as the winch is being raised.