Torque contorl doesn't work for hand loaded from MPL/MPL.xml?

Official Python bindings with a focus on reinforcement learning and robotics.
Post Reply
r9dyt
Posts: 5
Joined: Tue May 19, 2020 4:42 pm

Torque contorl doesn't work for hand loaded from MPL/MPL.xml?

Post by r9dyt » Tue Sep 08, 2020 2:32 am

I'm trying to change joint states by using torque control, but it gives me really wired behavior. However position control is totally fine. I am not sure if this is because MPL/MPL.xml is not URDF format. It will be really appreciated if somebody can provide me some info.

The following is a toy example, joint 17 is a joint from index finger based on the kinematic hand. So I simply applied a torque on joint 17 for a different hand mesh, but it seems like the torque is applied to somewhere entirely different.

Code: Select all

import numpy as np
import pybullet as p
import time
import pybullet_data

import math

physicsClient = p.connect(p.GUI)#or p.DIRECT for non-graphical version
p.setAdditionalSearchPath(pybullet_data.getDataPath()) #optionally

timeStep = 1./240.
p.setPhysicsEngineParameter(fixedTimeStep=timeStep)

planeId = p.loadURDF("plane.urdf")

target_objects = p.loadMJCF("MPL/MPL.xml")
target_hand = target_objects[0]
pd_objects = p.loadMJCF("MPL/MPL.xml")
pd_hand = pd_objects[0]

p.resetBasePositionAndOrientation(target_hand, [2.7, -2.2, 2.4], [0, 0, 0, 1])
p.resetBasePositionAndOrientation(pd_hand, [2.7, -2.2, 2.6], [0, 0, 0, 1])
p.createConstraint(pd_hand, -1, -1, -1, p.JOINT_FIXED, [0, 0, 0], [0, 0, 0], #[-0.05, 0, 0.02]
                              [2.7, -2.2, 2.6], [0, 0, 0, 1])

jointsCount = p.getNumJoints(pd_hand)
indices = []
targetPositions = []
maxForces = []
kps = []
kds = []
for i in range(jointsCount):
  indices.append(i)
  targetPositions.append(0.0)
  maxForces.append(2000000000)
  kps.append(1) #1000000000
  kds.append(10)#500000

#p.setJointMotorControl2(pd_hand, 17, p.POSITION_CONTROL, 1, 0)

from pdControllerStable_customized import PDControllerStable
#stablePD = PDControllerStable(p)
pi = 3.141592
while(1):
    #p.setJointMotorControl2(hand, 11, p.POSITION_CONTROL, pi / 4.)
    #rot = p.getQuaternionFromEuler([math.sin(time.time()*3), 0, 0])
    rot1 = math.sin(time.time() * 3)
    rot2 = math.cos(time.time() * 3)
    #kinematic
    p.resetJointState(target_hand, 17, rot1)
    p.resetJointState(target_hand, 19, rot2)
    p.resetJointState(target_hand, 21, rot1)

    #pd
    # p.setJointMotorControl2(pd_hand, 17, p.POSITION_CONTROL, targetPosition=rot1)
    # p.setJointMotorControl2(pd_hand, 19, p.POSITION_CONTROL, targetPosition=rot2)
    # p.setJointMotorControl2(pd_hand, 21, p.POSITION_CONTROL, targetPosition=rot1)
    targetPositions[17] = rot1
    targetPositions[19] = rot2
    targetPositions[21] = rot1

    #PD control
    jointStates = p.getJointStates(pd_hand, indices)

    q1 = []
    qdot1 = []
    for i in range(jointsCount):
        q1.append(jointStates[i][0])
        qdot1.append(jointStates[i][1])

    q = np.array(q1)
    qdot = np.array(qdot1)
    qdes = np.array(targetPositions)
    qError = qdes - q
    Kp = np.diagflat(kps)
    Kd = np.diagflat(kds)
    P = Kp.dot(qError)
    D = Kd.dot(qdot)
    taus = P - D

    p.setJointMotorControl2(
        pd_hand,
        17,
        controlMode=p.TORQUE_CONTROL,
        force=2
    )

    # for index in range(jointsCount):
    #     p.setJointMotorControl2(
    #         pd_hand,
    #         index,
    #         controlMode=p.TORQUE_CONTROL,
    #         force=taus[index]
    #     )

    p.stepSimulation()
    time.sleep(timeStep)

p.disconnect()

Post Reply