error normal force of sphere to plane force (3D contact model)

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superman on 7 Sep 2020
Answered: Steve Miller on 29 Nov 2021
Now I am doing the simulation of biped walking robot. six actuated joints
Values of contact parameters are as follow:
  • Mass: 74 kg
  • Contact stiffness: 70000 N/m
  • Contact damping: 4000 N/m/s
  • Penetration exponent: 0.01 mm
  • contact_point_radius: 0.01 mm
When the simulation was running, the value of normal force (ground reaction force) is very large and having sluggish rise, which causes the robot to fly off the ground.
Could you give me some advices? Thanks very much.
Attachments is my simulink model.

Answers (1)

Steve Miller
Steve Miller on 29 Nov 2021
Hi - I was not able to run your model because many files are missing, including F:\biped ankle pushOff simulation\biped_DataFile.m
However, from the pictures you posted and the settings in the model, it is clear you are using solver settings that are not great for models with contact forces. ode23 is an explicit solver and it will likely not capture the start and finish of contact forces well. Please try using ode23t.

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