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Webots physics4/3/2023 ![]() ![]() I believe that other people using Bullet for simulating robotic or mechanical systems will also be interested. There is definitely interest on our side for porting the Danzig solver to Bullet. I look forward for any info, good or bad. Have anyone encountered the sames problems as me ? Has anyone been able to program a realistic humanoid robot model using an unmodified version of Bullet ? Is Bullet suitable to simulate mechanical systems with several actuated joints such as humanoid/quadruped robots, articulated arms/hands, wheeled robots, etc. So we are currently stuck in our transition to Bullet and would appreciate some advice: We have also tried the btGeneric6DofConstraint with similar results. must again be ruled out because this unfortunately makes the values unrealistic. improves things, unfortunately this also decreases the performance to a level that is finally slower than ODE.Īnd 3. increasing a lot (up to 100) the number of iterations of the solverĪlthough 1. decreasing the time step (stepSimulation())Ģ. We noticed that the weakness about the btHingeConstraint can be counter-balanced by:ġ. For example we need to simulate wheeled robots, in which the wheels typically weight 30 times less than the robot's bodys, or robotic hands, where the fingers weight much less than the arm. Of course Bullet's User Manual recommend to avoid large mass ratios, but we need to simulate something physically plausible. a chain of btRigidBodys linked with btHingeConstraints where the btRigidBodys use small and large btShapes alternatively. Similarly Bullet has a hard time to cope with large ratios of moment of inertia, e.g. ![]() ![]() Bullet hinges move off the axis and become unstable and relaxed with smaller mass ratio than ODE. The problem we have noticed is that Bullet's btHingeConstraint seems to be much less capable to cope with large mass ratios compared to ODE's hinges. This is different from video games where the physics engine must only yield visually plausible results. Our simulator is also used to validate mechanical prototypes before the real robots are built, hence we need accurate physical values. In a robot simulator we need to work with physically plausible values, because our simulations are used in experiments where people want to measure accurate forces or torques through simulated force/pressure sensors, etc. However after a substantial amount of work in porting our software to Bullet we came across some of Bullet's limitations. We thought that from Bullet we would benefit from more reliable and complete collision detection, soft bodies and many other features that ODE does not have. Recently we decided to evaluate the option of switching our application from ODE to Bullet. We have developed for many years a commercial robot simulator using ODE. ![]()
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