Engee documentation

Inertia

Perfect rotational inertia.

blockType: AcausalFoundation.Mechanical.Rotational.Elements.Inertia

inertia 1

Path in the library:

/Physical Modeling/Fundamental/Mechanical/Rotational/Elements/Inertia

Description

Block Inertia represents the ideal rotational inertia, which is described by the following equation:

Where

  • — torque;

  • — moment of inertia;

  • — angular velocity;

  • — Time.

By default, the unit has one non-directional rotary mechanical port. The positive direction of the block is from the port to the control point. A torque is positive if it results in acceleration in a positive direction.

In some applications, it is customary to display inertial elements sequentially with other elements on the flowchart. To support this use case, the parameter Number of graphical ports allows you to use the second port.

The dual-port option is exclusively graphical: both ports have the same angular velocity, so the unit functions the same regardless of whether it has one or two ports. The block icon changes depending on the parameter value Number of graphical ports.

Number of graphics ports Block icon

1

inertia 1

2

inertia 2

Variables

Use the parameter group Initial Targets to set the priority and initial target values for the block parameter variables before simulation. For more information, see Configuring physical blocks using target values.

Ports

Conserving

# I — the port connecting the unit to the network
rotational mechanics

Details

A mechanical rotary port that connects the unit to the physical network.

Program usage name

flange_reference_a

# J — the second graphics port
rotational mechanics

Details

The second rotary port, which allows the inertial elements to be connected sequentially to other elements of the flowchart. This port is tightly connected to the I port, so the difference between a single-port and a two-port block representation is purely graphical.

Dependencies

To use this port, set the parameter Number of graphical ports meaning 2.

Program usage name

flange_reference_b

Parameters

Parameters

# Inertia — moment of inertia
kg*m^2 | g*m^2 | kg*cm^2 | g*cm^2 | lbm*in^2 | lbm*ft^2 | slug*in^2 | slug*ft^2

Details

The value of the moment of inertia, which is constant during the simulation.

Units

kg*m^2 | g*m^2 | kg*cm^2 | g*cm^2 | lbm*in^2 | lbm*ft^2 | slug*in^2 | slug*ft^2
Default value

0.01 kg*m^2
Program usage name

I
Evaluatable

Yes

# Number of graphical ports — number of graphics ports
1 | 2

Details

Number of graphics ports:

  • 1 — the unit has one port that connects it to a mechanical rotary system. If the unit has one port, connect it to the connecting line between the other two units.

  • 2 — when this option is selected, the second port opens, which allows you to connect the unit in series with other units in the circuit. The two ports are rigidly connected and have the same angular velocity, so the unit functions exactly as if it had a single port.

Values

1 | 2
Default value

1
Program usage name

flange_count
Evaluatable

No

Examples