forward-dynamics-derivatives.py

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import pinocchio as pin
import numpy as np



# Create model and data

model = pin.buildSampleModelHumanoidRandom()
data = model.createData()

# Set bounds (by default they are undefinded for a the Simple Humanoid model)

model.lowerPositionLimit = -np.ones((model.nq,1))
model.upperPositionLimit = np.ones((model.nq,1))

q = pin.randomConfiguration(model) # joint configuration
v = np.random.rand(model.nv,1) # joint velocity
tau = np.random.rand(model.nv,1) # joint acceleration

# Evaluate the derivatives

pin.computeABADerivatives(model,data,q,v,tau)

# Retrieve the derivatives in data

ddq_dq = data.ddq_dq # Derivatives of the FD w.r.t. the joint config vector
ddq_dv = data.ddq_dv # Derivatives of the FD w.r.t. the joint velocity vector
ddq_dtau = data.Minv # Derivatives of the FD w.r.t. the joint acceleration vector