CUSTOMISED SUSPENSION TEMPLATE IN ADAMS CAR

OBJECTIVE:

To create a suspension template using the template builder in ADAMS Car and run a Kinematic Analysis on it.

THEORY:

MSC ADAMS is one of the most powerful tools in Multibody Dynamics, which focuses more on automobiles, especially on the suspension design.

ADAMS Car provides us with a Template builder option, where we can customise and create a suspension subsystem based on our own customised geometry like pre-loaded templates.

Though there are several hybrid suspension geometries, Macpherson strut is selected to have an easy understanding of the construction and the procedure.

PROCEDURE:

The first step to do is to open Template builder in ADAMS Car. Click on File->New to create a new template.

The template window is shown in the above figure.

Before going into the detailed procedure, the following major components must be designed to create a suspension template

1. Hardpoints
2. Geometries
3. Parts
4. Links
5. Mounts
6. Bushings
7. Hub
8. Markers
9. Joints
10. Springs and Dampers
11. Force specifications
12. Communicators

DETAILED PROCEDURE:

HARDPOINTS:

Hardpoints are created in the state space representation of the template. In case of Macpherson strut, the following hardpoints are required

1. Position of the lower control arm (triangle)
2. Position of a lower suspension mount
3. Position of top mount
4. Position of the tie-rod (inner and outer)
5. Wheel centre point
6. Wheel spindle point
7. Position of the hub
8. Position of the knuckle

The hardpoints mark the locations of the individual links, parts and other geometries in every suspension subsystem.

PARTS:

Parts are components in the template which merges two or more links to unify them and make them behave as a single unit in dynamic conditions. Parts are of two kinds:

1. General Parts which deal with the links and unified dynamic response
2. Mount Parts to form fixed portions of the templates, so that they do not undergo any motion

General parts are hub, control arm, tie-rods and wheel knuckle assembly. Mount parts are used to form the fixture of a specific geometry. Mount parts are essentially hardpoints which are fixed during dynamic study of the subsystem.

WHEEL HUB

CONTROL ARM

TIEROD

KNUCKLE/CARRIER

CREATION OF PART:

Parts are created by going to the Build option in the menu0 and selecting the Parts option. From thereon, select the specific type of part which is needed to be constructed.

GENERAL PART

MOUNT PART

LINKS AND GEOMETRIES:

Links are used to join two hardpoints in order to obtain a suspension mechanism. For example the control arm hardpoints are connected via links to form a lower control arm. In the same way, the knuckle of the vehicle is created along with the tie-rod.

CONTROL ARM

TIEROD

KNUCKLE

JOINTS:

Joints determine the motion between two links. ADAMS Car provides a variety of joints to enable the motion of the subsystem. The different joints ADAMS can provide are listed below:

1. Translational 9. Perpendicular
2. Rotational 10. Inplane
3. Revolute 11. Hooke
4. Cylindrical
5. Spherical
6. Planar
7. Fixed
8. Inline

JOINT WIZARD

BUSHINGS:

After creating the mount parts, bushings are to be added for the control arm. Parameters such as preload and offset that define bushings are to be specified. In this example, the default values that Adams Car provides are used. Modification of the bushing properties can also be done as per the requirement. You can also set its inactive status to kinematic, so that during a kinematic analysis Adams Car can deactivate bushings.

CONTROL ARM BUSHING

DAMPER BUSHING

SPRINGS AND DAMPERS:

The most important components of a suspension subsystem are spring and damper setup. ADAMS has pre-built spring and damper files. They can also be customised as per the details in the given dialog box

SPRING CONSTRUCTION

DAMPER CONSTRUCTION

If required, stoppers can also be provided in the same way to avoid buckling and loss of elasticity of the springs

COMMUNICATORS:

Adams Car uses communicators to correctly assemble the model for analysis. Communicators are the Adams Car elements that allow the subsystems and test rigs to exchange information about topological data, array parameter variables, location and orientation data.

Every subsystem or test rig in Adams Car has input communicators that need information from other subsystems to function correctly. Similarly, the corresponding subsystem or test rig need a correctly named output communicator that will send the required information. For example, an input communicator needs information on the location of a hardpoint. A corresponding output communicator provides the location information.

During the assembly process, Adams Car scans the model for subsystems with minor roles. It then looks through those subsystems for any input communicators that require information. It then tries to find an output communicator, of the same entity type, with the same matching name. If it can’t find one, it won’t match the communicators and the model may be incorrectly assembled.

Whenever a mount part is created in a template, Adams Car automatically creates a corresponding input communicator. During assembly, this input communicator should match the correct output mount communicator located in the test rig. If Adams Car finds no matching output communicator, it replaces the mount part with the ground part.

These input and output communicators must have the exact same name for Adams Car to know which communicators to use. This is explained in detail in Defining Communicators section.

DEFINING COMMUNICATORS:

For the assembly process to work correctly, the connection between the suspension and the suspension test rig test rig (_MDI_SUSPENSION_TESTRIG) must be specified. To do this, define the communicators that attach the hub to the suspension test rig at the wheel center. When the suspension is analysed in static mode, the hub should be constrained to the wheel carrier. If not, the assembly will have a rotational degree of freedom that prevents the analysis from converging to a solution. Adams Car creates the actuator between the hub and the upright wheel carrier automatically based on the communicators mentioned above.

COMMUNICATOR INFORMATION

FINAL TEMPLATE:

Thus after providing all the necessary parameters the final template is created. The final view of the template is given above. An assembly should created out of this template to check its feasibility. The procedure for assembly creation is explained as follows:

ASSEMBLY CREATION:

From the Standard Interface you can create the suspension subsystem using the template you have customised From this template, an assembly can be created.

Note:

In this case we have included the tie rods to the template, select front suspension in the minor role, while creating the subsystem.

ASSIGNING STATIC VALUES:

The term static values refers to the paramters to be provided when the vehicle is at rest

PERFORMING PARALLEL WHEEL TRAVEL ANALYSIS:

Click on Simulate->Suspension Analysis-> Parallel Wheel Travel. An analysis dialog box appears. Fill in all the necessary parameters required

SIMULATION WINDOW

POST-PROCESSING:

Animation:

ANIMATION WINDOW

The link to the animation generated is

https://youtu.be/0edh5lblI6c

https://www.youtube.com/watch?v=S7L_s9HWvQc

RESULT:

Thus a customised template is created in the template builder and kinematic analysis is performed on the standard interface.