Reference Guide for a 2-Axis Robot Arm with 2-Phase Stepping
Motors Incorporating Resolvers
2.4.3 Joint Angle Calculation
Calculate the angle of each joint from the tip coordinates of the arm by using successive Jacobian
calculations.
• Successive Jacobian calculations
Y
θ
2
θ
1
L
1
Calculate the tip coordinates (x, y) from
x =
sin
+
1
1
y =
cos
+
1
1
̇ = {
cos
Differentiate them by time.
1
1
̇ = {
sin
1
1
cos
̇
Change them into a matrix.
�
� = �
̇
1
−
sin
1
Change the matrix into a form to obtain
1
cos
�
� = �
1
−
2
1
=
−
and
−1
Add the difference of the angle to the joint angle in the previous cycle and assume the result as the
current joint angle.
�
� = �
� + �
1
1−1
2
2−1
R01AN5644EJ0100 Rev.1.00
Jan 22, 2021
P(x,y)
L
2
X
sin (
+
)
2
1
2
cos (
+
)
2
1
2
̇ +
+
cos (
+
)}
2
1
2
1
̇ +
+
sin (
+
)}
2
1
2
1
+
cos (
+
)
1
2
1
2
sin (
) −
−
+
1
2
1
2
cos (
)
+
+
1
2
1
2
sin
−
sin (
+
1
2
1
2
=
−
−1
are assumed.
cos (
cos
+
1
1−1
2
sin (
−
sin
−
1
1−1
2
and
1
2
.
̇
cos (
+
)
2
1
2
2
̇
sin (
+
)
2
1
2
2
̇
cos (
+
)
� �
�
2
1
2
1
sin (
)
̇
+
2
1
2
2
and
1
2
, and differentiate both sides by time.
cos (
)
+
−1
�
2
1
2
) −
sin (
+
)
2
1
2
)
cos (
+
1−1
2−1
2
) −
sin (
+
1−1
2−1
2
RX24T, RX72M,
RAA3064002GFP/RAA3064003GFP
�
�
)
+
−1
�
�
1−1
2−1
)
+
1−1
2−1
�
Page 45 of 62