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Merge pull request #3246 from Danfoa/master

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Fix Stable-PD Control bug on First Order Taylor approximation of next `q` state
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erwincoumans 2021-03-07 08:19:37 -08:00 committed by GitHub
commit 0c7ea68709
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1 changed files with 46 additions and 47 deletions
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examples/pybullet/examples/pdControllerStable.py
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@ -70,43 +70,34 @@ class PDControllerStableMultiDof(object):
Kp = np.diagflat(kps)
Kd = np.diagflat(kds)
p = Kp.dot(qError)
# Compute -Kp(q + qdot - qdes)
p_term = Kp.dot(qError - qdot*timeStep)
# Compute -Kd(qdot - qdotdes)
d_term = Kd.dot(qdoterr)
#np.savetxt("pb_qError.csv", qError, delimiter=",")
#np.savetxt("pb_p.csv", p, delimiter=",")
d = Kd.dot(qdoterr)
#np.savetxt("pb_d.csv", d, delimiter=",")
#np.savetxt("pbqdoterr.csv", qdoterr, delimiter=",")
M1 = self._pb.calculateMassMatrix(bodyUniqueId, q1, flags=1)
M2 = np.array(M1)
#np.savetxt("M2.csv", M2, delimiter=",")
M = (M2 + Kd * timeStep)
#np.savetxt("pbM_tKd.csv",M, delimiter=",")
c1 = self._pb.calculateInverseDynamics(bodyUniqueId, q1, qdot1, zeroAccelerations, flags=1)
c = np.array(c1)
#np.savetxt("pbC.csv",c, delimiter=",")
A = M
#p = [0]*43
b = p + d - c
#np.savetxt("pb_acc.csv",b, delimiter=",")
qddot = np.linalg.solve(A, b)
tau = p + d - Kd.dot(qddot) * timeStep
#print("len(tau)=",len(tau))
# Compute Inertia matrix M(q)
M = self._pb.calculateMassMatrix(bodyUniqueId, q1, flags=1)
M = np.array(M)
# Given: M(q) * qddot + C(q, qdot) = T_ext + T_int
# Compute Coriolis and External (Gravitational) terms G = C - T_ext
G = self._pb.calculateInverseDynamics(bodyUniqueId, q1, qdot1, zeroAccelerations, flags=1)
G = np.array(G)
# Obtain estimated generalized accelerations, considering Coriolis and Gravitational forces, and stable PD actions
qddot = np.linalg.solve(a=(M + Kd * timeStep),
b=p_term + d_term - G)
# Compute control generalized forces (T_int)
tau = p_term + d_term - Kd.dot(qddot) * timeStep
# Clip generalized forces to actuator limits
maxF = np.array(maxForces)
forces = np.clip(tau, -maxF, maxF)
return forces
generalized_forces = np.clip(tau, -maxF, maxF)
return generalized_forces
class PDControllerStable(object):
"""
Implementation based on: Tan, J., Liu, K., & Turk, G. (2011). "Stable proportional-derivative controllers"
DOI: 10.1109/MCG.2011.30
"""
def __init__(self, pb):
self._pb = pb
@ -121,28 +112,36 @@ class PDControllerStable(object):
q1.append(jointStates[i][0])
qdot1.append(jointStates[i][1])
zeroAccelerations.append(0)
q = np.array(q1)
qdot = np.array(qdot1)
qdes = np.array(desiredPositions)
qdotdes = np.array(desiredVelocities)
qError = qdes - q
qdotError = qdotdes - qdot
Kp = np.diagflat(kps)
Kd = np.diagflat(kds)
p = Kp.dot(qError)
d = Kd.dot(qdotError)
forces = p + d
M1 = self._pb.calculateMassMatrix(bodyUniqueId, q1)
M2 = np.array(M1)
M = (M2 + Kd * timeStep)
c1 = self._pb.calculateInverseDynamics(bodyUniqueId, q1, qdot1, zeroAccelerations)
c = np.array(c1)
A = M
b = -c + p + d
qddot = np.linalg.solve(A, b)
tau = p + d - Kd.dot(qddot) * timeStep
# Compute -Kp(q + qdot - qdes)
p_term = Kp.dot(qError - qdot*timeStep)
# Compute -Kd(qdot - qdotdes)
d_term = Kd.dot(qdotError)
# Compute Inertia matrix M(q)
M = self._pb.calculateMassMatrix(bodyUniqueId, q1)
M = np.array(M)
# Given: M(q) * qddot + C(q, qdot) = T_ext + T_int
# Compute Coriolis and External (Gravitational) terms G = C - T_ext
G = self._pb.calculateInverseDynamics(bodyUniqueId, q1, qdot1, zeroAccelerations)
G = np.array(G)
# Obtain estimated generalized accelerations, considering Coriolis and Gravitational forces, and stable PD actions
qddot = np.linalg.solve(a=(M + Kd * timeStep),
b=(-G + p_term + d_term))
# Compute control generalized forces (T_int)
tau = p_term + d_term - (Kd.dot(qddot) * timeStep)
# Clip generalized forces to actuator limits
maxF = np.array(maxForces)
forces = np.clip(tau, -maxF, maxF)
#print("c=",c)
return tau
generalized_forces = np.clip(tau, -maxF, maxF)
return generalized_forces