Rotating Hydraulic Actuator

This example shows a typical hydraulic cylinder actuator used to operate friction clutches, brakes and other devices installed on rotating shafts. The key element of the actuator is a piston that moves back and forth under pressure provided through the central drill in the shaft and through channels in the clutch. In the example, the actuator acts against a preloaded spring, which tends to push the piston against the clutch wall.

Model

The following figure shows the schematic diagram of the rotating hydraulic actuator:

- Internal piston radius

- External piston radius

, - Arm lengths of the lever

As pressure is applied to the fluid passage in the shaft, static pressure, together with pressure developed in rotating chamber, builds up until it overcomes the preload force and shifts the piston forward.

In the example, the hydraulic system is fed by a pump with delivery of 4.5 lpm. The relief valve is set to 20 bar. The motion control is performed with the 3-way directional valve, which initially connects the clutch chamber with the tank. As control signal is applied, the passage to the tank is closed and the chamber is connected with the pump.

Two actuator cycles are simulated in the example. The first stroke is performed with shaft rotating at angular velocity of 120 rad/s. The angular velocity during the second stroke is 275 rad/s.

Simulation Results from Simscape Logging

The plots below show the pressure, speed, and extension of the rotating hydraulic cylinder. A slightly higher pressure is seen in the second stroke due to the higher rotational speed of the cylinder.