Re: setJointMotorControl2 won't assign correct force value to certain joints

2020-07-08T00:05:09+00:00

Don't enable 'realtime' simulation, but stepSimulation instead, when applying forces like this.
Also, best to keep using a small time step (1./240. is default), not 1 second.
Watch the various examples/gym environments, for example
https://github.com/bulletphysics/bullet ... t/examples

Statistics: Posted by Erwin Coumans — Wed Jul 08, 2020 12:05 am

Re: setJointMotorControl2 won't assign correct force value to certain joints

2020-07-05T07:59:42+00:00

I see.

Thanks for the help.

Statistics: Posted by sakura_hana — Sun Jul 05, 2020 7:59 am

Re: setJointMotorControl2 won't assign correct force value to certain joints

2020-07-05T07:07:05+00:00

thanks for you reply.
this issue is caused by that the mass of the lower legs are too small, so far i don't know how to fix this. i just increase the mass to workaound this.

Statistics: Posted by steven — Sun Jul 05, 2020 7:07 am

Re: setJointMotorControl2 won't assign correct force value to certain joints

2020-07-05T04:10:58+00:00

Here is a zip for the files.

Run on Python 3.6.8

Thanks.

Quadruped PyBullet Files.zip

Statistics: Posted by sakura_hana — Sun Jul 05, 2020 4:10 am

Re: setJointMotorControl2 won't assign correct force value to certain joints

2020-07-05T03:18:42+00:00

Can't reproduce your issue? Could you provide all the files? thanks.

cannot find 'MQ_SIM_ASEM/meshes/Chassis.STL' in any directory in urdf path

Statistics: Posted by steven — Sun Jul 05, 2020 3:18 am

setJointMotorControl2 won't assign correct force value to certain joints

2020-07-03T23:51:35+00:00

Hello,

I am loading a quadruped model into the simulation environment using a URDF file. The model loads in correctly, however, when applying POSITION_CONTROL via setJointMotorControl2 to the robots lower leg joints, the joints are unable to maintain their position under the weight of the robot.

When applying POSITION_CONTROL to the upper leg and shoulder joints of the robot, they maintain their set position without issue. Its only the lower legs that can't maintain, even though I am applying a higher force to them then any other joint.

When reducing the simulation gravity to around -2 instead of -9.81, they lower leg joints are able to somewhat maintain the set position.

I am relitively new to pybullet, and this problem baffles me, so I would appreciate some help.

Here is my main code:

Code:

import pybullet as pimport timeimport pybullet_dataphysicsClient = p.connect(p.GUI) # or p.DIRECT for non graphical versionp.setAdditionalSearchPath(pybullet_data.getDataPath()) #optionally#p.setTimeStep(1.0)planeID = p.loadURDF("plane.urdf")p.resetDebugVisualizerCamera( cameraDistance=0.5, cameraYaw=75, cameraPitch=-20, cameraTargetPosition=[0.0, 0.0, 0.25])baseStartPos = [0,0,0.5]baseStartOrientation = p.getQuaternionFromEuler([1,0,0])quadrupedID = p.loadURDF("MQ_SIM_ASEM/urdf/MQ_SIM_ASEM.urdf",baseStartPos, baseStartOrientation)#p.changeDynamics(sphereUid,-1,spinningFriction=0.001, rollingFriction=0.001,linearDamping=0.0)# Set Joints to home positionfor joint in range (p.getNumJoints(quadrupedID)):p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=0.0,force=10,maxVelocity=5)# Set Shoulder Jointsjoint = 0p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=-0.125,force=5,maxVelocity=5)joint = 3p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=0.125,force=5,maxVelocity=5)joint = 6p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=-0.125,force=5,maxVelocity=5)joint = 9p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=0.125,force=5,maxVelocity=5)# Set Upper Jointsjoint = 1p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=-0.75,force=5,maxVelocity=5)joint = 4p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=-0.75,force=5,maxVelocity=5)joint = 7p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=-0.75,force=5,maxVelocity=5)joint = 10p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=-0.75,force=5,maxVelocity=5)# Set Lower Jointsjoint = 2p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=-0.2,force=1000,maxVelocity=5)joint = 5p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=-0.2,force=1000,maxVelocity=5)joint = 8p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=-0.2,force=1000,maxVelocity=5)joint = 11p.setJointMotorControl2(quadrupedID,joint,p.POSITION_CONTROL,targetPosition=-0.2,force=1000,maxVelocity=5)#Set Link Dynamicsjoint = 2p.changeDynamics(quadrupedID,joint,lateralFriction=0.1,spinningFriction=0.001, rollingFriction=0.001)joint = 5p.changeDynamics(quadrupedID,joint,lateralFriction=0.1,spinningFriction=0.001, rollingFriction=0.001)joint = 8p.changeDynamics(quadrupedID,joint,lateralFriction=0.1,spinningFriction=0.001, rollingFriction=0.001)joint = 11p.changeDynamics(quadrupedID,joint,lateralFriction=0.1,spinningFriction=0.001, rollingFriction=0.001)p.getNumJoints(quadrupedID)for i in range (p.getNumJoints(quadrupedID)):print(p.getJointInfo(quadrupedID,i))p.setGravity(0,0,-9.81)p.setRealTimeSimulation(1)while (1):keys = p.getKeyboardEvents()#print(keys)basePos, baseOrn = p.getBasePositionAndOrientation(quadrupedID) # Get model positionp.resetDebugVisualizerCamera( cameraDistance=0.35, cameraYaw=75, cameraPitch=-20, cameraTargetPosition=basePos) # fix camera onto modeltime.sleep(0.01)basePos, baseOrn = p.getBasePositionAndOrientation(quadrupedID)print(basePos, baseOrn)p.disconnect()

and my urdf code:

Code:

Thanks.

Statistics: Posted by sakura_hana — Fri Jul 03, 2020 11:51 pm

Real-Time Physics Simulation Forum

Re: setJointMotorControl2 won't assign correct force value to certain joints

Re: setJointMotorControl2 won't assign correct force value to certain joints

Re: setJointMotorControl2 won't assign correct force value to certain joints

Re: setJointMotorControl2 won't assign correct force value to certain joints

Re: setJointMotorControl2 won't assign correct force value to certain joints

setJointMotorControl2 won't assign correct force value to certain joints