Created in COMSOL Multiphysics 5.1

T r u c k Moun t e d C r an e Ana l y z e r

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About the Truck Mounted Crane Analyzer

Many trucks are equipped with cranes for load handling. Such cranes have a number of hydraulic cylinders that control the crane’s motion, and several mechanisms.

In this application, a rigid-body analysis of a crane is performed in order to find the payload capacity for the specified orientation and extension of the crane. This application also provides the usage of hydraulic cylinders and highlights the limiting cylinder. The capacity of the hydraulic cylinders can be modified in order to improve the payload capacity and the usage of the cylinders.

You can change the following parameters:

• The angle to the horizontal of the inner boom

• The angle between the booms

• The total extension length

• The capacity of the inner boom cylinder

• The capacity of the outer boom cylinder

• The capacity of the extension cylinders

Figure 1 shows the application’s user interface.

Reset input

Evaluate

Runstudy

Read documentation

Entermodel inputs

Sketch

results

Plotconfiguration

Figure 1: The application’s user interface.

Set the input parameters in the Orientation and Extension section. These parameters govern the configuration of the crane and the position of the payload. Details of these parameters and different crane parts are shown in the Sketch section. A new configuration of the crane can be plotted in the Configuration section by clicking the Update button in the

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Configuration section in the ribbon. The capacity of the inner boom cylinder, outer boom cylinder, and extension cylinders can also be modified in the Capacity of Hydraulic Cylinders

section. Finally, click the Compute button in the Simulation section in the ribbon to start the computation. Input parameters can be reset using the Reset button in the User Input section.

The results of the simulation i.e., payload capacity, and hydraulic cylinder usage are displayed in the Results section. The graphics window in the Configuration section shows the updated position of all the linkages for the specified input parameters. Finally, to generate the report of the application, click the Create Report button.

The expected computation time for computing the payload capacity of the crane is around 25 seconds on a typical desktop computer. The expected computation time, and the last computation time or, alternatively, the solution state can be seen in the Information section.

G E O M E T R Y

Figure 2: Truck mounted crane geometry.

Figure 2 shows the geometry of the truck mounted crane. Various parts of the crane, which are useful for setting up the input parameters, are given in the table below.

TABLE 1: CRANE PARTS

PARTS COLOR

Inner boom Cyan

Outer boom Green

Inner boom cylinder Red

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O R I E N T A T I O N A N D E X T E N S I O N

The angle of the inner boom with the horizontal is α; it can vary between -15º and 90º. The angle between the inner boom and the outer boom is β; it can vary between 0º and 165º. The total extension is given by Δl, which can vary from 0 m to 5.5 m. These parameters can be specified to set the configuration of the crane and the position of the payload.

H Y D R A U L I C C Y L I N D E R S

The crane has five hydraulic cylinders. The first cylinder is mounted between the base and the inner boom. This cylinder is for rotating the inner boom with respect to the base. The second cylinder is mounted between the inner boom and the outer boom. This cylinder is for rotating the outer boom with respect to the inner boom. The other three cylinders serve to change the length of the three extensions.

The capacity of these hydraulic cylinders can be specified. The capacity of the inner boom cylinder and the outer boom cylinder can vary between 0.1 ton and 1000 ton, whereas, the capacity of the extension cylinders can vary between 0.1 ton and 100 ton.

C R A N E W E I G H T

The weight of the crane is 6.48 ton. This is fixed in this application.

R E S U L T S

This application computes the maximum payload that can be lifted for the specified crane configuration and the specified capacities of the hydraulic cylinders. It also gives the percent usage of each hydraulic cylinder. The limiting hydraulic cylinder, i.e., the cylinder with 100% usage, for the specified configuration of the crane and the specified capacity of the hydraulic cylinders is also highlighted.

There is a possibility that for the specified configuration of the crane, the specified capacities of one or more of the hydraulic cylinders are not sufficient to lift the crane’s own weight. In this case, a warning message is displayed together with the minimum required capacity of each hydraulic cylinder to lift the crane’s own weight. This minimum required capacity of each cylinder is also highlighted if it exceeds the specified capacity of the cylinder.

Outer boom cylinder Blue

Extension cylinders Magenta

TABLE 1: CRANE PARTS

PARTS COLOR

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The Embedded Model

The model is set up using the Multibody Dynamics interface with a Stationary study. Here, all the links are assumed to be rigid and are modeled using the Rigid Domain feature. The connections between various links are set up using Hinge Joints, Prismatic Joints, and Slot Joints.

Note: This application is derived from the Truck Mounted Crane model. Refer to the documentation of this model for detailed information on the modeling process.

Notes About the Implementation

P A Y L O A D C A P A C I T Y C O M P U T A T I O N

The maximum payload that can be lifted in the specified crane configuration is limited by the capacity of one of the hydraulic cylinders. To compute the payload capacity, results are computed for two cases: with certain assumed payload and without payload. The payload capacity computed using first hydraulic cylinder is given by:

where

• Wpc1 is the payload capacity

• Fc is the cylinder capacity

• F1 is the load on the cylinder in the first case

• F2 is the load on the cylinder in the second case

• Wp is the assumed payload

Similarly, the payload capacity is computed using loads on each hydraulic cylinder. The minimum of all of them is the payload capacity of the crane:

The percent usage of each cylinder is computed using the final payload capacity:

Here UF is the percent usage.

Wpc1 Fc F1–( ) F2 F1–( )⁄ Wp⋅=

Wpc min Wpc1 Wpc2 Wpc3, ,( )=

UF F1 Wpc Wp⁄ F2 F1–( )⋅+( ) Fc⁄ 100⋅=

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If the cylinder load, F1, exceeds the specified cylinder capacity, Fc, for any of the cylinders, the payload capacity is not computed. Instead, the minimum required capacities of the hydraulic cylinders to lift the crane’s own weight, F1, are displayed.

Application Library path: Multibody_Dynamics_Module/Demo_Applications/truck_mounted_crane_analyzer

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