Multibody link quadruped robot modeling problems

Hi,

Im currently having problems with my quadruped robot model simulation in simscape multibody. I designed the robot in solidworks and transferred the design with mates to the matlab environment. I have differential equations that drive the joints to make the robot walk. I transferred the model on my simulink project file and when i drive the joints with ANY signal i always get singularity and kinematic constraints cannot be maintained errors after 1.1147 seconds.

I already tried lowering and tightening the solver consistency tolerances, using local solvers, different variable step solvers. Sometimes the joints dont even lock up either. I will share a couple screenshots that demos my case: (i disabled the signals in order to detect the problem)

Answer 1

[Ritika Thusoo]

Since the issue occurs even when the actuation signals are disabled, the problem is likely related to the imported CAD mechanism or constraint definition.

Please try the following troubleshooting steps:

• Review the SolidWorks mates and ensure only supported, non-redundant mate types are used before export.
• Simplify the assembly where possible by removing redundant constraints and rigidifying subassemblies.
• Try simulating the model without inputs or external forces to confirm if the mechanism itself is stable.
• Validate the initial pose and motion using “Simscape Multibody KinematicsSolver” to check for infeasible configurations or singularities.

For more information, refer to the following MathWorks documentation:

KinematicsSolver - Solve kinematics problems for a multibody model - MATLAB

• If needed, rebuild a smaller portion of the model, such as one leg, using explicit Simscape joints to isolate the issue.

For more information on Simscape Multibody, refer to the MathWorks documentation:

How to Build a Multibody in Simulink - MATLAB & Simulink

If the issue persists, please contact MathWorks Technical Support.