Medical

Communication

Biosci. Biotech. Res. Comm. 9(3): 546-552 (2016)

An adaptive controller for motion control of

nanorobots inside human blood vessels

Amir Farahani*

and Ali Farahani

Ashtian Branch, Islamic Azad University, Ashtian, Markazi, Iran

Kharazmi University, Tehran, Iran

ABSTRACT

The rise of nanorobots for medical diagnostics and treatments is arriving in the near future. In this study, a control

method is designed so that the motion of a nanorobot can be controlled inside the blood vessel of the human body

when we use them for medical therapies. A kinematic model of nanorobot in MATLAB/SIMULINK is used for dem-

onstrating the movement of nanorobots to examine the performance of proposed control mechanism. The nanorobot

system used in this study is a nanorobot with very small dimensions (0.5 m) with a rigid body. It was assumed that

the damaged part of the vessel wall is detected by the nanorobot with the help of the signals transmitted from the

part. We applied an adaptive control algorithm and with this type of controller, the nanorobot motion was optimized.

Our results showed that by using the proposed method, the system was controlled such that the nanorobot moved

towards the damaged area and reached the target destination with an improved accuracy. Simulations indicated the

ef ciency of this control method with respect to the nonlinear velocity equation of the nanorobot.

KEY WORDS: MEDICAL THERAPY, NANOROBOTS, NAVIGATION, OPTIMIZATION, CONTROL SYSTEM, ADAPTIVE METHOD

546

ARTICLE INFORMATION:

*Corresponding Author: amirfarahani2080@gmail.com

Received 21

Aug, 2016

Accepted after revision 25

Sep, 2016

BBRC Print ISSN: 0974-6455

Online ISSN: 2321-4007

Thomson Reuters ISI ESC and Crossref Indexed Journal

NAAS Journal Score 2015: 3.48 Cosmos IF : 4.006

reserved.

Online Contents Available at: http//www.bbrc.in/

INTRODUCTION

Platelets are plasma elements which are spherical or

oval shaped with 2-5 microns in diameter (Warkentin,

2009). Blood platelets are blood cells which exist in our

blood. When they recognize a part of the blood vessel is

damaged, they intertwine to stop the bleeding. In other

words, when there is a wound in the body, the platelets

stick together, and create a blood clot; as result, it cause

a hemostaticprocess.Platelets also are called thrombo-

cytes because a clot also is called a thrombus. Thrombo-

cytopenia is a condition in which the platelets count is

Amir Farahani and Ali Farahani

less than 150,000 per microliter which causes excessive

bleeding. In this case, the patient may enter the shock

from blood loss. Or it may occur inside the brain causing

intracranial hemorrhage which causes death or paralysis

of the patient. There are many ways to treat thrombo-

cytopenia. One common method is the Platelet trans-

fusions. Normal platelet count in an adult is 150000-

400000/µL. After the transfusion, platelets remain only

about ten days, and then, they are destroyed. Thus, the

patient needs the transfusion of platelets about two to

three times per month. One of recent techniques that is

used to heal the wounds is the use of nanorobots which

within the human body, acts like arti cial platelets. They

are expected to enable diagnosis, medical therapies, and

surgery (Montemagno and Bachand, 1999; Freitas 1998,

1999 and 2005; Cavalcanti, 2003).

Nanorobots can travel inside the body. They can

detect different patterns of chemicals in the body, moni-

tor their biochemical and biomechanical characteristics

and store the observations based on an internal clock

in their memories (Hogg and Kuekes, 2006). With the

help of nanomedicine diseases can be easily cured with

no side effects and no surgery is required (Yadav et al.

2011).There are many studies that have investigated the

use of nanorobots for medical treatment (Abeer , 2012;

Kharwade et al. 2013;Manjunath and Kishore, 2014).

Most researches on nanorobots have been done for

different type of automated and accurate medical tar-

get identi cation (Cavalcanti et al. 2008). Nanorobots

are increasingly important in today’s world, but there is

still no good framework to design these kinds of robots,

although in this  eld recently some studies have been

carried out (e.g. Behkam and Sitti, 2006; Arora and

Saini, 2013 and Farr et al. 2014).

Cavalcanti et al. (2009) presented a method to release

nanorobots inside the blood vessels to identify aneurysm

in the brain. Al-Arif et al. (2011) investigated the pos-

sibility of using Nanorobots in  nding damaged nerve

and delivering medicine to cure the demyelination. Due

to the small size of these robots, the designed robots are

very complicated and consist of very small components.

Boonrong and Kaewkamnerdpong (2011) proposed a

swarm intelligence based control mechanism for swarm

nanorobots that operate as arti cial platelets to search

for wounds. For both industrial and medical applications

such as microsurgery, Pan et al. (2011) developed a pro-

totype with a rotatable head and a body that has legs

and  ns. Douglas et al. (2012) described a DNA nanobot

shaped like a hexagonal tube, with its two halves con-

nected by a latched hinge. When the little device rec-

ognizes a target cell based on its surface proteins, the

two halves swing open like a clam to deliver a tiny but

deadly cargo of drugs or nanoparticles.

Jaiswal et al. (2013) studied the use of an arti cial

nano-medical erythrocyte which duplicates all of the

important functions of the red blood cell by providing

treatment for anaemia, heart attack, choking, lung dis-

eases, asphyxia, and other respiratory problems. These

nano-robots are able to keep a patient’s tissues safely

oxygenated for up to about 4 hours (at maximum dos-

age) if their heart has stopped beating in case of a heart

attack.

In this study, a method is proposed to control the

nanorobot motion inside the human blood vessel by

performing an adaptive control algorithm. The impor-

tance of the nanorobot motion control within the vessel

is revealed when the nanorobot wants to move towards

the wall to detect and treat the wounds and in amma-

tion of the blood vessel wall. The structure of this paper

is as follows:  rst we introduce the kinematic model of

our nanorobot system, and present its governing equa-

tions; next, nanorobot control system is designed and its

control algorithm is provided; next section reports the

results of the simulation to evaluate the performance of

the system; and in the  nal section we present our con-

clusions according to the results of stimulation

MATERIAL AND METHODS

NANOROBOT SYSTEM

In this paper we tried to optimize the movement of a

nanorobot inside human blood vessel. The nanorobot

system used in this study is a nanorobot with very small

dimensions (0.5 m) with a rigid body. Figure 1 shows

the kinematic model of this system.

In this  gure,  is the rotational angle of the tip of

the nanorobot,  is the angel between the body axis and

the axis x,  is the nanorobot length, k denotes the cur-

vature of the reference trajectory, and O is the center of

rotation. Considering the rigid body of nanorobots, we

will have:

(1)

(2)

By deriving from equation (1) and (2), we will have:

(3)

(4)

According to  gure 1, we have:

(5)

BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS ADAPTIVE CONTROLLING OF NANOROBOTS INSIDE HUMAN BLOOD VESSELS 547

Amir Farahani and Ali Farahani

(6)

(7)

Equations (5), (6) and (7) express nanorobots kinematic

equations. These equations are used to calculate the next

state of the robot moving forward to the destination

which is the vessel wall.

In this study, it is assumed that the damaged part

of the vessel wall is detected by the nanorobot with

the help of the signals transmitted from the part. The

path to the damaged part is determined as a  fth-order

equation which is presented as a reference trajectory in

equation (8).

(8)

The reference path is shown in  gure 2.

To  nd the coef cients of the equation for the refer-

ence trajectory, the following boundary conditions are

used:

(9)

Where, X

= horizontal component of the initialpoint, Y

= vertical component of the initial point, X

= horizontal

component of the terminal point, and Y

= vertical com-

ponent of the terminal point. According to the reference

trajectory, the nanorobot follows the path. To achieve

this goal, we designed a controller that with determining

the angle of , it be able to control the angle  in such

a way that the nanorobot motion can move according

to the reference trajectory. With this algorithm, nanoro-

bot can reach the affected area with high accuracy after

traveling in the motion path, arrive the damaged part.

System error is calculated using equations (10) and (11)

which are appropriate criteria for evaluating the system

performance. Equation (10) computes the error of the

horizontal component of nanorobot motion relative to

the horizontal component of the reference trajectory:

(10)

While, equation (11) calculates the error of the vertical

component of nanorobot motion relative to the vertical

component of the reference trajectory.

(11)

DESIGN OF THE CONTROLLER

The controller designed for this purpose is an adaptive

controller. The basis for using adaptive controller is to

control the system with the presence of uncertainty.

Although uncertainty means the presence of the ano-

nymity of parameters and system dynamics, but an

adaptive controller generally requires parameters esti-

mation to limit the system output error. In other words,

the expectation of an adaptive controller is not the esti-

mation of system’s unknown parameter but controller

parameter estimation in a way that the error remains

FIGURE 1. Nanorobot system kinematic design

548 ADAPTIVE CONTROLLING OF NANOROBOTS INSIDE HUMAN BLOOD VESSELS BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS ADAPTIVE CONTROLLING OF NANOROBOTS INSIDE HUMAN BLOOD VESSELS 549

Amir Farahani and Ali Farahani

FIGURE 2. Reference trajectory of the nanorobot system

limited and acceptable. However, in case of persistent

irritation in the system, we can estimate the parameters

of the system.

The adaptive control of non-linear systems generally

has no same rules and procedures. However, in this sys-

tem, we can  nd out that because of the structure of the

state space equations, the third equation of the nanoro-

bot system’s kinematic equations can be used. In other

words, by the state control of in equation (12), x and y

can be controlled in equations (13) and (14):

(12)

(13)

Where, L = nanorobot length, v = nanorobot velocity, 



= derived reference angle between the body axis and

the axis x, = controller parameter, and 

= the refer-

ence angle between the body axis and the axis x. Now,

by having all the values, the system tracking error will

tend to zero with the appropriate choice of . As it was

mentioned before, the motion mechanism of nanorobot

is such that the blood  ow in vessels is the only driv-

ing force or thrust. The blood velocity in the vessel is

obtained as:

(14)

Where = pressure gradient, µ = viscosity coef cient,

= vessel diameter, and = longitudinal location of nanoro-

bot. We assumed that nanorobot is located between the

end of the arterial and venous vessels.

According to Sembulingam and Sembulingam (2012),

pressure gradient in this area is 15 mm hg. Also, accord-

ing to Hogg and Kuekes (2006), the blood viscosity coef-

 cient is 0.04. The vessel diameter varies in different parts

of the body.In this study, the vessel diameter was consid-

ered as 30 µm and nanorobot length as 0.5 µm. Therefore,

considering the provided values for the parameters, the

blood velocity which is equal to the velocity of nanorobot

motion can be obtained. In equation (14), with smaller

y, we will have less  uid velocity. In other words, when

nanorobot gets closer to the vessel wall, its movement

speed is reduced. The velocity of blood has the highest

value in the center of the vessel, and with higher distance

from the center, its velocity is decreased.

We assumed that nanorobot is in motion with the

highest speed in the center of vessel, and by recogniz-

ing the damaged blood vessel wall, it begins to move

from the center to the wall. By substituting equation (12)

into equation (11), the is controlled, and by substituting

the controlled into the motion equations of (5) to (7),

Nanorobot path can be controlled well with respect to

the reference path. Figure 3 illustrates the overall block

diagram of the system with the controller.

RESULTS AND DISCUSSION

In this study, MATLAB/ SIMULINK software was used

to simulate Nanorobot motion within the blood vessel.

By using equation (5) to (7), nanorobot motion from the

center of the vessel to the damaged part was plotted as

shown in  gure 4.

By comparing the reference trajectory path with

nanorobot motion path (Fig.5), we can see that the

550 ADAPTIVE CONTROLLING OF NANOROBOTS INSIDE HUMAN BLOOD VESSELS BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

Amir Farahani and Ali Farahani

FIGURE 4. Nanorobot motion

FIGURE 5. Reference trajectory path vs. nanorobot motion path

FIGURE 3. Block diagram of the proposed system

BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS ADAPTIVE CONTROLLING OF NANOROBOTS INSIDE HUMAN BLOOD VESSELS 551

Amir Farahani and Ali Farahani

FIGURE 6. Motion error of nanorobot in vertical direction

FIGURE 7. Motion error of nanorobot in horizontal direction

FIGURE 8. Nanorobot motion along the blood vessel length

motion path curve of the nanorobot is largely matches

the trajectory path curve, and there have little difference

with each other. This ensures the nanorobots to reach

the desired destination.

Motion error graph of nanorobot in two vertical

and horizontal directions are shown in Figure 6 and 7,

respectively. In vertical direction, it can be clearly seen

that most error rate at the beginning of the movement

and the time it starts, the amount of which is equal to

1.6 µm which is negligible. After 0.001 seconds, its error

rate is drastically reduced and approaches to zero (Fig.

6). In horizontal direction, the greatest amount of error

is 0.02 µm which is negligible (Fig. 7). Given the results

of simulation, it can be well observed that the proposed

controller can properly navigate the nanorobot, and

by using this controller, we can control the motion off

nanorobot to the location of the damaged vessel wall by

controlling its movement angle.

552 ADAPTIVE CONTROLLING OF NANOROBOTS INSIDE HUMAN BLOOD VESSELS BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

Amir Farahani and Ali Farahani

Nanorobot motion within the vessel is shown in  gure

8. The red section represents the blood vessel wall; the

blue lines show the nanorobot motion path, and the black

lines are the damaged parts on the blood vessel wall. We

can see that the nanorobot moves from the center of the

vessel, and after moving in a given direction provided by

the controller, it reaches the damaged part.

CONCLUSION

In this study we attempted to design an adaptive control-

ler to optimize the motion of nanorobots within the within

the blood vessel. The results of the simulation showed

that the proposed control method, by identifying the

functional characterization of nano-robots such as trans-

port capability, biocompatibility, planning, receiving sig-

nals and its generation, had good performance in control-

ling the nanorobot motion, and its ef ciency is high. The

experimental results and simulations which were based

on considering the blood vessel as a rigid pipe, showed

that with the help of the adaptive controller, nanorobot

followed the determined reference trajectory path by the

signal received from the damaged area, and was moved to

the target destination with an error of about 0.01 µm. The

design of this controller makes it possible for us to be able

to use nanorobots for e.g. venous injury treatment, cancer

treatment, treatment of damaged cells, or laparoscopy with

great accuracy. We suggest that a study to be conducted by

considering the blood vessel as a  exible tube to examine

nanorobot motion inside the vessel and the relationship

among several nanorobots in the body to enhance their

ef ciency.

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