
7.2 Problem Set: Robots 291
7.2 Problem Set: Robots
Schematic representations of a robot arm consisting of three links 1, 2, and 3 are
shown in Figs. 7.16–7.25. The mass centers of links 1, 2, and 3 are C
1
, C
2
, and C
3
,
respectively. The generalized coordinates (quantities associated with the instanta-
neous position of the system) are q
1
(t), q
2
(t), and q
3
(t).
The central principal axes of link p, p = 1,2,3 are parallel to ı
p
, j
p
, k
p
and the
associated moments of inertia have the values I
px
, I
py
, I
pz
, respectively. The central
inertia dyadic of link p is
¯
I
p
=(I
px
ı
p
)ı
p
+(I
py
j
p
)j
p
+(I
pz
k
p
)k
p
.
If the joint between link p and link p + 1isa
rotational joint consider a control vector moment
T
p,p+1
= T
(p,p+1)x
ı
p+1
+ T
(p,p+1)y
j
p+1
+ T
(p,p+1)z
k
p+1
,
translational joint consider a control vector force
F
p,p+1
= F
(p,p+1)x
ı
p+1
+ F
(p,p+1)y
j
p+1
+ F
(p,p+1)z
k
p+1
.
Select suitable numerical values for the input numerical data.
1. Find the transformation matrices R
ij
.
2. Calculate the angular velocities and accelerations of the links,
ω
ij
and α
ij
.
3. Determine the position vectors, r
C
i
, the velocities, v
C
i
, and the accelerations, a
C
i
of the mass centers C
i
.
4. Find the generalized (active) forces Q
i
.
5. Write a MATLAB program for the symbolical calculation of Lagrange’s equa-
tions of motion or/and Kane’s dynamical equations.
6. Find the numerical solutions for inverse dynamics and direct dynamics.