Building a Simple Suspension System in MotionView

Welcome to the Multibody Dynamics for Automotive Applications using MotionView and MotionSolve blog series. In this chapter, we take a deep dive into multibody dynamics simulation by starting with a simple suspension system. This exercise is part of a series where we progressively build a full vehicle model, incorporating front and rear suspension, body, and seating system. By using MotionView software, we will explore key concepts such as joints, hard points, and spring damper entities, which are essential for vehicle system modeling.

Exploring the Initial Model

Before adding any new entities, let's examine the existing multibody simulation software model:

1. Three bodies: Ground body (default), knuckle, and wheel.

2. Two graphics: One for the wheel and one for the knuckle.

3. Two joints:

• Wheel to knuckle (revolute joint).
• Knuckle to body (cylindrical joint).

4. Three types of motion:

• Wheel rotation.
• Steering motion.
• Static ride motion.

5. Five hard points:

• Global origin (default).
• Wheel center.
• Knuckle top.
• Knuckle center of mass.
• Damper middle.

It is important to note that hard points are created as pairs (left and right), ensuring symmetry. This multibody dynamics modeling technique allows us to parameterize the right side based on the left, optimizing the automotive engineering simulation.

Creating the Spring Damper Entity in MotionView

To add a spring damper entity, follow these steps:

Use either method:

• Right-click the spring damper icon in the toolbar.
• Go to Model > Add > Force Entity > Spring Damper.
• Select a coil spring (pair type) to generate both left and right springs.
• Enable explicit graphics to visualize the coil spring.

Set connectivity:

• Body 1 → Ground body.
• Body 2 → Knuckle.
• Point 1 → Knuckle top.
• Point 2 → Knuckle center of mass.

Once created, select "symmetric properties" and assign the left side as the master. Any changes applied to the left will automatically update the right, ensuring consistency in automotive dynamics analysis.

Adjusting Properties and Visual Representation

• Set spring stiffness to 100 N/mm and damping ratio to 10 Ns/mm.
• Modify explicit graphics to enhance visualization:
• Increase spring coil radius from 35 mm to 70 mm.
• Change color to alloy finish for clarity.

Although these changes do not affect simulation results, they improve multibody dynamics training by making components easier to identify.

Adding Explicit Graphics for the Damper

To further enhance the automotive multibody simulation, we add explicit graphics for the damper:

1. Create "Damper Top" using a cylinder:

• Parent body → Ground.
• Origin → Knuckle top.
• Direction → Damper middle.
• Increase radius from 10 mm to 60 mm.
• Set color to aluminum alloy.

2. Create "Damper Bottom" with similar steps:

• Parent body → Knuckle.
• Origin → Knuckle center of mass.
• Direction → Damper middle.
• Increase radius from 10 mm to 40 mm.

Running and Testing the Suspension System

Once the suspension system is built, follow these steps to verify it:

• Run the simulation in MotionSolve software.
• Analyze results in HyperView.

Visualize force vectors:

• Select force result type.
• Display X, Y, and Z components.
• Set vector size to 0.2.

This completes the multibody dynamics essentials of suspension system modeling. In the next blog, we will package this suspension system into a reusable module and prepare it for full vehicle integration.

This blog is part of our ongoing Multibody Dynamics blog series. If you missed the previous posts, check them out here.

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