The Structural Optimum Design of Erected Circular Medicine-Chest Based on
Non-intervention Motion
Zhi-qiang Zhang 1,2, Chao Yun 1, Xiang-quan Liu 2,Li-yong Wang 2
1
2
.Institute of Robotics, Beijing University of Aeronautics & Astronautics, Beijing 100191
. School of Mechanical & Electrical Engineering, Beijing Information Science & Technology University, Beijing
100192
(zzqbj@sohu.com)
Abstract: In this paper, the following studies are
completed, including the analysis of the mechanical
structure of the erected circular medicine-chest as well as its
working principle, discussion of the non-intervention motion
conditions of drug containers according to their different
motion phases, establishment of the optimum functions of
the chain transmission based on the conditions of the nonintervention motion of the containers, obtention of the
minimum circular radius of drug containers by application
of Matlab as well as the obtention of the design parameters
of chain transmission, the simulation model building with
UG and ADAMS, and the accomplishment of the motion
simulation to prove the success of optimum design based on
the non-intervention motion condition of drug containers.
Key words: erected circular medicine-chest, optimum
functions, non-intervention motion conditions, motion
simulation
I.
supplementary equipment to the drug dispensing machine
for box-packed drugs as effective assisting[4].
II.
THE WORKING PRINCIPLE OF THE ERECTED
CIRCULAR MEDICINE-CHEST
In operation, after two rate reductions, one by reducer,
the other by the first chain transmission, the motor of the
erected circular medicine-chest drives the two driving
chain wheels on the synchronizing shaft, connected to
which are two driven wheels fixed on the two half axles
accordingly. Driven by the chains, the support rods and
balance bars fixed on them make all the drug containers
move circularly. Drugs in the movable containers, after
receiving the dispensing order, are conveyed along the
shortest path and reached the outlets within the shortest
time.
INTRODUCTION
Currently, with the limitation regarding technology,
the drug storing system in a hospital pharmacy mainly
consists of ordinary shelves, unable to realize the dense
storage. In most of the hospital pharmacy, the facilities
are old, working environment poor and pharmacists’
working intensity high. In addition, there are other
problems such as storage complexity, space waste, low
working efficiency, etc. The introduction of automated
pharmacy system may help to make a better overall plan
for the pharmacy, including reducing the drug storage
area, effectively carrying out the standardized and
automated management of the pharmacy, thus improving
drug dispensing and reducing patients’ waiting time. The
automated pharmacy system may be connected to HIS,
putting all the working process of the working staff under
the supervision[1-3].
The typical equipment is erected circular Medicinechest, which is originated from the digital-controlled
erected circular inventory for the management and
storage of accessories and tools in large factories. Basing
on the stereoscopic inventory, when adding safety
security, humanization design and connecting with the
HIS system of hospital, it can be sued for the pharmacy
management in the hospital. This is a semi-automatic
system, in which the drug dispensary works should be
done artificially. This type of automatic system is
adaptable to the package of drugs, and can be used as the
III. THE ANALYSIS
OF THE CONDITIONS IN
REGARD TO NONINTERVENTION MOTION
OF NEIGHBOURING
DRUG CONTAINERS
As shown in Figure
1, the pitch of chain
084A: 12.7 mm; the
span between the two
support rods connected
to the same container:
18 pitches; the span
between the support
rods
respectively
Figure 1. The structure of the
erected circular medicine-chest
connected
to
the
neighbouring
containers:4 pitches; the number of containers(evenly
arranged along the chains):12.
The pitch radiuses of both driving wheels and driven
wheels: r; the overhang of the support rods: c; the
width and height of the containers: w and h ,
respectively; the space between the centers of the pivots
of the two neighbouring drug containers: H; the fixation
range for the connection beam: A; the safety space
between the connection beam and the drug container: s.
As shown in Figure 2, with the center of driven wheel
as the origin of coordinate, the reference coordinate is
O
O
O
O
built; 1 、 2 、 3 、 4 are, respectively, the joint
points of the transmission chain with the Supporting Rods
A
1
A 2 , whose
No. 1, 2, 3 and 4 for the Drug Containers
,
x1, y1 
x2 , y2 
x3, y3 



coordinates are
、
、
、
 x4, y4 
A
accordingly.
1
is the center of the pivot of
A
Container 1 and Supporting Rods No. 1 & 2, while 2 is
the center of the pivot of Container 2 and Supporting
A
A
Rods No. 3 & 4. The coordinates of 1 、 2 are
 X1,Y1  、  X2,Y2  respectively. The wheels do
counterclockwise rotation.
Suppose located in the pitch circle is Point B, which
is on the same horizontal line with Center O of the
O
O
O
O
chain wheel, coinciding with 1 , 2 , 3 , 4 are on the
same vertical line. At the beginning of the container
O
motion,
1
moves unclockwise along the circle with r
as the radius, while
O
When
and
O
2
2
O
2
,
O
3
,
O
4
move upward vertically.
reaches the same height as that of Point O ,
move along the same circle.
OO
OO

0
1 and
2 when
angle between
along the same circle simultaneously;
between OB and X

axis;
included
2
between
OO3
is
O
1
is the included
O
1
1
O
、 2 move
is the angle
OO2
and
O
O
space and the vertical space of the Centers of Pivots

A. The mathematical model of the optimum design of
chain transmission
1) The idea of the optimum design of chain
transmission.
The floor area of the erected circular medicine-chest
refers to the projected area of the outline of the steelwork,
whose length is affected by such factors as the length of
the drug containers, while whose width by such factors as
the turning radius and the width of the drug containers.
After the design of the drug containers, the following
references may be given, including the width wand
height h of the container, as well as the pitch of the
chain. In the design of the chain transmission, available
are the best overhang of the support rods c and the pitch
radius of the chain wheel r based on the optimum
design, thus also available is the minimum turning radius
of the container, whose outline of the steelwork is
smallest in width. If the length remains the same, the
floor area will be reduced, also reduced will be the
mechanical deformation of the steelwork.
2) The design variables and objective functions
Based on the analysis of the condition of
nonintervention motion, 1 is a independent variable, if
,then
the coefficient
is introduced,and
and will be variables, so:

X

x


 r1

1 xx
2 3
T
T
Lcr

r


1

 Y are the horizontal
A
THE OPTIMUM DESIGN OF CHAIN TRANSMISSION
BASED ON NON-INTERVENTION MOTION

（）
Based on the above, the expression of the objective
function of the optimum design is:
f
x
x
1

x


2
1
3) Constraints
① The vertical nonintervention motion of the
containers on the left and those on the right:
2
L

w

A

2
s
In the practical design, selected are the following data:
 X and
and 2 , the condition
of
nonintervention
motion is[5]:


Xw
if 0
,
IV.
To make available the smallest width of the outline of
the steelwork, the Turning Radius L is taken as the
objective function, then:
the
angle
2 ,
3
when
move along the same
circle simultaneously.
Suppose, at the
motion of Containers
1 and 2,
Xw, there must be no intervention
When 
between the two drug containers.
A
1
Figure2. The motion initial positions
of the two neighbouring drug
containers
Y  h

w

4
2
0
m
m
,
A

3
0
m
m
,
s

8
7
m
m
∵
Lcr

r


1

,
r
1


0
.3
1
2
m

∴
②Since the container forces on the support rods, the
overhang of the support rod should not be too long in
order to ensure the enough strength of the chain. In the
design:
0
.
1
5
m

c

0
.
2
5
m
.
1
5
m

r
0
.
2
5
m
 0

③The diameter of the chain pitch circle:

p
d 
180
sin
z 

1
2
.7
m
m
:the pitch of the chain, here p
, z :40～60,
p
60,
.
0
8
1
m

r

0
.
1
2
1
m
 0

④The space between the centers of the pivots of the
two neighbouring drug containers:
1
2
.7
m
m
∵ p
,
H
∴
(the space between the centers of the pivots of
the two neighbouring drug containers moving vertically)
must meet the following condition:
Hhh0
h
0
: the gap between the two neighbouring drug
h 3mm.
containers moving vertically, generally 0
Then, according to the structure of the chain,
H  np .
n :the number of the pitches whose total length
amounts to h , i.e. the height of the container.

2
7
5
m
m
Here h
,and it may be calculated: n 22.
n
22
If
,the total number of the pitches will be 264.
H

2
7
9
.
4
m
m
∴

⑤
0

,
2
n
3
6
0

6
.3
5


1


3
6
a
r
c
s
i
n
0
 
(6)
n
3
6
0

6
.3
5


2


8
a
r
c
s
i
n
2
 
n1
(7)
: the number of the pitches whose total length
O
n
amounts to the distance between 1 and 2 ; 2 : the
number of the pitches whose total length amounts to the
O
O
distance between 2 、 3 .
⑥ Based on Formulae (3) and (4), it may be deduced:
1
.
2
4

3
.
0
8

0


2


1
0
2
⑦The scope of :
4) The mathematical model
Omitted here are the track equations of the centers of
Pivots and that of the guide rail of the balance bars.
From the above, Variables x1 , x2 and x3 may be
1
gx
x
x
0
.
2
5

3
21
0 
1
0,
When
g
x

X

4
1
gx

X
2
0

5
1 4
g
x

2
7
5

Y

x
x
9
3
.
7


6
1
2
33





g
x

x

R
c
o
s
x


/
2

4
2
0




When 0 1 0 2,
g
x


x

R
c
o
s
x

/
2




4
2
3
0
5
2
30
gx
2
7
5

R
s
i
n


/2

x

6
2
0

x
x
3
9
3
.7
23



,
When 0 2 1
g
x

X

4
3
gx

X
2
0

5
3 4
g
x
2
7
5


Y

6
3
 



2
2
1
0
When
,
g
x



X


4
4
gx

X

4
2
0

5
4
gx
2
7
5


Y

6
4


2


0
2
,
g
x
2
7
5


Y

6
5
g
1
.2
4

x
x

7
1
r
O
gx
0
.
1
5

x
x

2
2
1
gx

X
2
0

5
5 4
r
z
s .t
g
x

0
.
3
1
2

x
1

x




1
2
1
1
When
g
x

X

4
5
:
z
the conditions of the Non-intervention Motion of the
containers may be expressed as follows[6-8]:
m
i
n
fx

x
1

x



2
1
substituted in the formula, then the optimum
mathematical model of the chain transmission based on
g
x
3
.0
8
x

8
1
gx
0
.
0
8
1

x

9
2
g
x
x

0
.
1
2
1

1
0
2
g
x3
1
1x

gx

x


2


1
2
3
0
2
B. The optimization based on Matlab
It may be seen from the mathematical model, the
optimum design belongs to that of the constrained
nonlinear optimization[9]. The Matlab functions to solve
the above problem of
the constrained nonlinear
optimization are FMINCON.
The calculation results based on Matlab are:
Lin
3
1
2
m
m

1
.7
6
0
9
1
1
3
m
m
, r
, m
.
5
.8
8, rounded for
According to formula(8), z5
z  56,then
p
d
226.5m
m
180
sin
z

1
1
3
.
2
5
m
m
i.e. r
According to Formula （ 2 ） , if
c

1
9
9
.
5
m
m
, the turning radius of the
L

3
1
2
.
7
5
m
m
container
.
The results of the optimum design include
the pitch of the chain:
,the overhang of
the support rod:
,the number of the
pitches whose total length amounts to the height
of the container:
,the total number of the
pitches:
,the
diameter
of
the
pitch:
,the teeth number of the chain
wheel:56, the length of the chain:
,the theoretical center distance:
the above mentioned structural optimum design is
established by the analysis based on modeling and
simulation.
ACKNOWLEDGEMENT
This work was completed with the support of the
project of national natural science foundation of china
(No. 51105041)
REFERENCES
[1]
[2]
[3]
V.
THE SIMULATION ANALYSIS BASED ON UG AND
ADAMS
[4]
According to the results of the optimum design, by
applying UG/Model, built up are the models of the chain
wheels, chain, containers and support rods etc. The solid
model for the analysis of the container motion is built up
as shown in Figure 3[10].
According to the test results of the motion simulation
intervention, based on the conditions of the Nonintervention Motion of the containers, feasible are the
results that the turning radius of the container
L

3
1
2
.
7
5
m
m
and the horizontal overhang of the
c

1
9
9
.
5
m
m
support rods
.
[5]
[6]
[7]
[8]
[9]
[10]
Figure 3 The solid model for the analysis of
the container motion
VI.
CONCLUSION
The analysis is made on the working principle of the
erected circular medicine-chest, built up are the
conditions in regard to non-intervention motion of
neighbouring drug containers, structure optimization is
implemented by the application of Matlab, feasibility of
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