Forward kinematics symbolic (fkine) computes different notation when compared to actual research paper #134
Description
Hi,
I was working on creating a 4DOF anthromorphic exoskeleton model using the DH Link. I have attached the arm model below. I face discrepancy between what robotic tool box symbolically computes the forward kinematics for end effector using fkine to that of the analytic equations as provided by the paper Link . Below the code, I have compared both the symbolic expressions for forward kinematics as computed by (a) robotics tool box fkine method (b) analytical from paper
# Dynamic Parameters:
mass = [1.38, 0.88]
I = [0.015, 0.013]
length = [0.33, 0.37]
L = [
RevoluteDH(
d = 0,
a = 0,
alpha = pi/2,
offset = pi/2,
flip = True,
),
RevoluteDH(
d = length[0],
a = 0,
alpha = pi/2,
offset = pi,
),
RevoluteDH(
d = 0,
a = 0,
alpha = -pi/2,
),
RevoluteDH(
d = length[1],
a = 0,
alpha = 0,
),
]
super().__init__(
L,
name="human_arm_4DOF",
manufacturer="",
keywords=("dynamics", "symbolic", "mesh"),
symbolic=symbolic,
meshdir="",
)Robotics tool box fkine:
1st rotation term : T[0] = (sin(q_0)*cos(q_1)*cos(q_2) + sin(q_2)*cos(q_0))*cos(q_3) - sin(q_0)*sin(q_1)*sin(q_3)
Analytical paper equation:
cos(q3) * (sin(q0) * sin(q2) + cos(q0) * cos(q1) * cos(q2)) − cos(q0) * sin(q1) * sin(q3)
can anyone help me with this query, Do I need to modify the D-H table from what the paper presents when I use that in roboticstoolbox, because I have faced similar issues with other models as well ?
Regards
Anshul