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Fix jacobian computation

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This commit is contained in:
Hervé Audren
2018-03-26 18:40:42 +09:00
parent 680ce39e96
commit a2e9ecd957
2 changed files with 78 additions and 18 deletions
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46
examples/pybullet/examples/jacobian.py
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@@ -8,6 +8,15 @@ def getJointStates(robot):
joint_torques = [state[3] for state in joint_states]
return joint_positions, joint_velocities, joint_torques
def getMotorJointStates(robot):
joint_states = p.getJointStates(robot, range(p.getNumJoints(robot)))
joint_infos = [p.getJointInfo(robot, i) for i in range(p.getNumJoints(robot))]
joint_states = [j for j, i in zip(joint_states, joint_infos) if i[3] > -1]
joint_positions = [state[0] for state in joint_states]
joint_velocities = [state[1] for state in joint_states]
joint_torques = [state[3] for state in joint_states]
return joint_positions, joint_velocities, joint_torques
def setJointPosition(robot, position, kp=1.0, kv=0.3):
num_joints = p.getNumJoints(robot)
zero_vec = [0.0] * num_joints
@@ -20,47 +29,60 @@ def setJointPosition(robot, position, kp=1.0, kv=0.3):
"Expected torque vector of "
"length {}, got {}".format(num_joints, len(torque)))
def multiplyJacobian(jacobian, vector):
def multiplyJacobian(robot, jacobian, vector):
result = [0.0, 0.0, 0.0]
i = 0
for c in range(len(vector)):
for r in range(3):
result[r] += jacobian[r][c] * vector[c]
if p.getJointInfo(robot, c)[3] > -1:
for r in range(3):
result[r] += jacobian[r][i] * vector[c]
i += 1
return result
clid = p.connect(p.SHARED_MEMORY)
if (clid<0):
p.connect(p.DIRECT)
time_step = 0.001
gravity_constant = -9.81
p.resetSimulation()
p.setTimeStep(time_step)
p.setGravity(0.0, 0.0, gravity_constant)
p.loadURDF("plane.urdf",[0,0,-0.3])
kukaId = p.loadURDF("kuka_iiwa/model.urdf",[0,0,0])
kukaId = p.loadURDF("TwoJointRobot_w_fixedJoints.urdf", useFixedBase=True)
#kukaId = p.loadURDF("TwoJointRobot_w_fixedJoints.urdf",[0,0,0])
#kukaId = p.loadURDF("kuka_iiwa/model.urdf",[0,0,0])
#kukaId = p.loadURDF("kuka_lwr/kuka.urdf",[0,0,0])
#kukaId = p.loadURDF("humanoid/nao.urdf",[0,0,0])
p.resetBasePositionAndOrientation(kukaId,[0,0,0],[0,0,0,1])
kukaEndEffectorIndex = 6
numJoints = p.getNumJoints(kukaId)
if (numJoints!=7):
exit()
kukaEndEffectorIndex = numJoints - 1
# Set a joint target for the position control and step the sim.
setJointPosition(kukaId, [0.1] * p.getNumJoints(kukaId))
setJointPosition(kukaId, [0.1] * numJoints)
p.stepSimulation()
# Get the joint and link state directly from Bullet.
pos, vel, torq = getJointStates(kukaId)
mpos, mvel, mtorq = getMotorJointStates(kukaId)
result = p.getLinkState(kukaId, kukaEndEffectorIndex, computeLinkVelocity=1, computeForwardKinematics=1)
link_trn, link_rot, com_trn, com_rot, frame_pos, frame_rot, link_vt, link_vr = result
# Get the Jacobians for the CoM of the end-effector link.
# Note that in this example com_rot = identity, and we would need to use com_rot.T * com_trn.
# The localPosition is always defined in terms of the link frame coordinates.
zero_vec = [0.0] * numJoints
jac_t, jac_r = p.calculateJacobian(kukaId, kukaEndEffectorIndex, com_trn, pos, zero_vec, zero_vec)
zero_vec = [0.0] * len(mpos)
jac_t, jac_r = p.calculateJacobian(kukaId, kukaEndEffectorIndex, com_trn, mpos, zero_vec, zero_vec)
print ("Link linear velocity of CoM from getLinkState:")
print (link_vt)
print ("Link linear velocity of CoM from linearJacobian * q_dot:")
print (multiplyJacobian(jac_t, vel))
print (multiplyJacobian(kukaId, jac_t, vel))
print ("Link angular velocity of CoM from getLinkState:")
print (link_vr)
print ("Link angular velocity of CoM from angularJacobian * q_dot:")
print (multiplyJacobian(jac_r, vel))
print (multiplyJacobian(kukaId, jac_r, vel))