Modeling a Four-Bar Mechanism in MotionView and MotionSolve

Welcome to the Multibody Dynamics for Automotive Applications using MotionView and MotionSolve blog series! 

In this blog, we will demonstrate how to build and analyze a four-bar mechanism in MotionView software. This exercise will cover joint creation, motion functions, and torque analysis, ensuring an optimized model for automotive engineering simulation. 

Step 1: Setting Up the Model 

We begin by modifying a simple pendulum model to include two additional bodies and three revolute joints. The goal is to: 

• Identify redundant constraints. 
• Replace unnecessary revolute joints with inline joints. 
• Use a motion function to measure torque. 

Step 2: Defining Hard Points and Bodies 

Rename and define key points: 

• Point A: (921, 580, 1124) 
• Point B: (918, 580, 114) 
• Point C: (915, 580, 1104) 

Additional points (E, F) are created for joint connections. 

Create bodies and assign properties: 

• Assign mass (1 kg) and inertia values. 
• Define center of mass at designated hard points. 
• Add graphical representations (cylinders) to improve visualization. 

Step 3: Creating Joints and Motion Functions 

Add three revolute joints: 

• Joint 1: Between Free Body and Body 0 at Point C. 
• Joint 2: Between Body 0 and Body 1 at Point E. 
• Joint 3: Between Body 1 and Ground at Point F. 

Apply motion at Joint 3: 

Define motion function:  

• Run motion solve simulation to compute results. 

Step 4: Detecting and Eliminating Redundant Constraints 

Using MotionView’s Check Model Utility, we analyze degrees of freedom: 

• A negative value indicates redundant constraints. To resolve this, we: 
• Replace middle revolute joints with inline joints, removing two translational degrees of freedom. 
• Re-run the analysis to confirm the system is now kinematically correct. 

Step 5: Output Analysis Using Motion Function 

Create an output request to measure torque. 

Define a motion function using syntax:  

• ID: Motion joint ID. 
• 0: Force/moment at I marker. 
• 7: Reports torque along Y-axis. 
• 0: Measured in global reference frame. 
• Run simulation and analyze torque in HyperGraph. 

Conclusion: Optimizing Multibody Dynamics Models 

By implementing inline joints and motion functions, we effectively eliminated redundant constraints, ensuring accurate vehicle system modeling. The torque output plotted in HyperGraph provides critical insights into system performance, enhancing multibody dynamics analysis for automotive applications. 

With these fundamentals, you can build complex automotive dynamics simulations using MotionView training and certification courses. Stay tuned for more MotionView tutorials for beginners and advanced applications in multibody simulation software!

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

Would you like to have a more interactive experience going through the Multibody Dynamics? 

Skill-Lync has released a FREE comprehensive course covering Multibody Dynamics for Automotive Applications using Motionview and Motionsolve in detail! Check it out here.

If you’re looking to go deeper into Multibody Dynamics check out Skill-Lync’s Multibody Dynamics Course.

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