Search found 65 matches

by steven
Mon Oct 14, 2019 5:24 am
Forum: PyBullet Support and Feedback
Topic: Simulating an KUKA LBR iwaa
Replies: 2
Views: 96

Re: Simulating an KUKA LBR iwaa

Could you provide a complete simple test? thanks.
by steven
Wed Sep 25, 2019 3:36 am
Forum: General Bullet Physics Support and Feedback
Topic: Why timeStep have to be this unreasonably small?
Replies: 7
Views: 1013

Re: Why timeStep have to be this unreasonably small?

This is from the assumption of linear elasticity. Similar to Hooke's Law, the torque is promotional to how much it displaces from the equilibrium position (angle). i hava an intuition that the torque of joint near the base should be larger than the joint near the end given the same delta theta, rig...
by steven
Mon Sep 16, 2019 1:26 pm
Forum: General Bullet Physics Support and Feedback
Topic: Why timeStep have to be this unreasonably small?
Replies: 7
Views: 1013

Re: Why timeStep have to be this unreasonably small?

sorry, i still don't understand why this function be written like that. i have some questions as below. 1. where do these constants come from such as -1.5e-3, 1.5735*1e5? 2. why the joint torque only have relation with the joint delta theta(if not consider the damping)? also you can call the POSITIO...
by steven
Wed Sep 11, 2019 8:56 am
Forum: General Bullet Physics Support and Feedback
Topic: Why timeStep have to be this unreasonably small?
Replies: 7
Views: 1013

Re: Why timeStep have to be this unreasonably small?

i change your code to use the POSITION_CONTROL mode with (5e-3)/240 us timestep which is bigger than what you used and it can work well as below. if you have to use the TORQUE_CONTROL mode based on some other consideration, Could you explain your function of TorVolThe(Theta,angularVelocity,Voltage)?...
by steven
Thu Sep 05, 2019 2:27 am
Forum: General Bullet Physics Support and Feedback
Topic: Why timeStep have to be this unreasonably small?
Replies: 7
Views: 1013

Re: Why timeStep have to be this unreasonably small?

hi Could you tell me the bullet version you used? i am testing this case with the attached code but get a different result.
my bullet version is 2.5.5.
by steven
Tue Aug 27, 2019 12:58 am
Forum: General Bullet Physics Support and Feedback
Topic: unstable soft body similation
Replies: 3
Views: 593

Re: unstable soft body similation

Could you email these object files to me, shengjun89@163.com? thanks.
by steven
Mon Aug 26, 2019 6:25 am
Forum: General Bullet Physics Support and Feedback
Topic: unstable soft body similation
Replies: 3
Views: 593

Re: unstable soft body similation

Could you attach all your body object? thanks.
by steven
Mon Jul 01, 2019 12:47 pm
Forum: PyBullet Support and Feedback
Topic: What accuracy to expect for trajectory tracking using position control
Replies: 6
Views: 792

Re: What accuracy to expect for trajectory tracking using position control

in the second case, the robot collides with the ground which will impact the links and joints of the robot.
by steven
Sun Jun 30, 2019 5:45 am
Forum: PyBullet Support and Feedback
Topic: What accuracy to expect for trajectory tracking using position control
Replies: 6
Views: 792

Re: What accuracy to expect for trajectory tracking using position control

thanks for your sharing. why did you said "maximum of 0.01 for some joint"? i add the following to print the max delta, the value is about 0.006. how much tracking accuracy do you need? the accuracy is very high if don't care about the velocity. print("max value=", np.max(robotlog[mask,17:23] - qeva...
by steven
Fri Jun 28, 2019 1:39 am
Forum: PyBullet Support and Feedback
Topic: What accuracy to expect for trajectory tracking using position control
Replies: 6
Views: 792

Re: What accuracy to expect for trajectory tracking using position control

Could you provide a complete simple test? i can work with you to find the root cause.
by steven
Wed May 29, 2019 11:51 am
Forum: General Bullet Physics Support and Feedback
Topic: Incorrect results when simulating multiple bodies
Replies: 8
Views: 923

Re: Incorrect results when simulating multiple bodies

hi tgreif,
sorry, it is hard for me to reproduce your issue. hope next time i can help you. good luck!
by steven
Mon May 27, 2019 12:21 pm
Forum: General Bullet Physics Support and Feedback
Topic: Incorrect results when simulating multiple bodies
Replies: 8
Views: 923

Re: Incorrect results when simulating multiple bodies

Could you tell me the initial postion of these two meshes, as well as some parameters, such as the initial velocity, friction, mass or other values? thanks.
by steven
Mon May 27, 2019 11:19 am
Forum: General Bullet Physics Support and Feedback
Topic: Incorrect results when simulating multiple bodies
Replies: 8
Views: 923

Re: Incorrect results when simulating multiple bodies

Could you attach your stl files and code snippet of how did you create your world? i want to reproduce it and then debug it to find the root cause.
thanks!
by steven
Sun May 26, 2019 2:12 pm
Forum: PyBullet Support and Feedback
Topic: Issues with velocity control
Replies: 5
Views: 919

Re: Issues with velocity control

update the procedure of this case. 1. apply the gravity to the multibody then will change the velocity, 2. apply the constraints, including 1> jointMotor constraint that will try to change the velocity back to the targetVelocity, 0 for your case; 2> Fixed constraint 3> contact constraint and frictio...