Hi 
I am implementing a IMU Kinematic Model, in that the rotation was represented as unit quaternion.
the navigation equations was implemented like the blow code
q_dot = 0.5 * quatmultiply_casadi(q, vertcat(0, gyroMeas - b_omega - n_omega))
def quatmultiply_casadi(q1, q2):
# Multiply two quaternions using CasADi symbolic variables.
q = SX(4, 1)
q[0] = q1[0]*q2[0] - q1[1]*q2[1] - q1[2]*q2[2] - q1[3]*q2[3]
q[1] = q1[0]*q2[1] + q1[1]*q2[0] + q1[2]*q2[3] - q1[3]*q2[2]
q[2] = q1[0]*q2[2] - q1[1]*q2[3] + q1[2]*q2[0] + q1[3]*q2[1]
q[3] = q1[0]*q2[3] + q1[1]*q2[2] - q1[2]*q2[1] + q1[3]*q2[0]
return q
the right side of the q_dot will return a 4D vector. Can the ERK integrator solve the equation? Is the results also a 4D vector?
the 4D vector was stored in state vector, but I think they should be handled as one quaternion.
how to formulate a quaternion, when the casadi expression are used?
Kind Regards
Lingbing