Extreme Hydraulics: Auto-alignment system

In a project that I am currently developing, rotation on the XY plane is required (axis of rotation is Z). After calculations, due to high forces demanded, a pair of hydraulic cylinders are required (see render above ).

There are two major problems in this type of construction:

• Absolute Synchronization of the two hydraulic cylinder during motion
• Auto-alignment of the construction at its center position after motion, in order to retract the construction in a storing box

Hydraulic Components of the Circuit:

The hydraulic circuit consists of two custom-made identical double acting hydraulic cylinders with spring return (see video of operation above), a 4/3 way valve with bypass (venting) position & a 2/2 way On/Off Valve.

NOTE: All Hydraulic Diagrams are made with FESTO FluidSIM Software. The pistons are set to have a variable force at its stroke length s=1000mm (0-300N at a range of 0-1000mm). This force is used to simulate the spring effect F=-Kx, where K=constant. Therefore, as the spring is compressed, it creates a force that its profile has a linear behavior.

Connections of the Circuit:

As it can be seen in the Hydraulic Diagram, the back sides of the hydraulic cylinders are short-circuit connected (this connection is for the absolute synchronization).

On the contrary, the front sides of the hydraulic cylinders are connected to ports A and B of 4/3 way valve with bypass (venting) position. Furthermore, the 2/2 way On/Off Valve is placed between the A and B port tubes. This enables the user to short-circuit ports A and B (this connection is for the auto-alignment).

Calculations of Synchronization

Calculations of Auto-alignment

Phases

In the following diagrams, the position of the phases of operation & the position of the pistons are shown in the chart.

NOTE: The two pistons move absolutely symmetrically!!!

1. Venting

2. Rotation to the right initiating from the center

3. Rotation to the left initiating from right position

4. Auto-alignment