The Research on Control System of Pipeline Dredging Robot based

on Simulink

Jiman Luo

, Lulu Dai

Shenyang Jianzhu University, Shenyang, China

Keywords: Pipe dredging robot, PI algorithm, double closed loop control, control system

Abstract: In order to control the new pipe dredging robot more accurately and ensure the stable operation of the

robot in the harsh environment, the motion control system of the robot is designed and the PI algorithm

based on double closed-loop speed control system for walking unit of wheeled mechanism is studied.

According to the Simulations by Simulink and experimentations of the above control methods, it was

indicated that the motor speed can be stabilized at the set speed value under the disturbance of load

change, and the dynamic performance is also stable. Finally, a double closed-loop speed control system

with strong anti-load fluctuation capability is adopted. The control method satisfied the requirements of

the working condition of the robot in a complex environment and realized that the precise control of the

motion state of the robot.

1. INTRODUCTION

At present, many universities and companies are

working on the study of pipeline robots and have

made considerable achievements. However, there are

still few robots that can dredge automatically, and the

control system of dredging robots is still not perfect.

A dredging robot that its core controller is 51 MCU

was developed in Changzhou University. The

pressure value is automatically adjusted to its own

size to adapt to different diameter pipes, which

improves the adaptability of dredging robots. A

detailed study on the pipeline inspection robot control

and navigation system is studied in Shanghai Jiao

tong university. The intelligent control of pipeline

robot autonomous path planning, navigation and

action is realized. Those dredging robots only have

the function of checking the internal damage of the

pipeline and replacing the staff to complete the cable-

carrying operation (Chen Li Gang, 2016), the self-

cleaning ability is poor. Therefore, the research of the

dredging robot control system still needs to be further

to improve the automation level of the dredging robot.

According to the mechanical structure and

working requirements of the robot, the design of the

whole control system is carried out to enhance the

controllability of the robot and achieve independent

dredging. In order to ensure the smooth and reliable

movement of the robot, it is necessary to research on

the motor control algorithm and the speed control

system deeply.

2. THE ROBOT STRUCTURE

AND CONTROL SYSTEM

2.1 The Mechanical System

Structure of Pipeline Dredging Robot

The structure of the dredging robot is shown in Figure

1. Considering drainage pipe is mostly circular, the

shape of the robot is designed with a cylindrical

structure. The mechanical body is mainly composed

of three parts, which are a wheeled walking

mechanism, a step-push mechanism and dredging

mechanism. The step pushing mechanism is an

auxiliary mechanism for the pipeline robot. When the

three walking units are all in a slipping state, the step

pushing mechanism starts to assist robot to advance.

The dredging mechanism is the core component of

the pipeline dredging robot to remove the sludge from

the pipeline.

Luo, J. and Dai, L.

The Research on Control System of Pipeline Dredging Robot based on Simulink.

DOI: 10.5220/0008480803290335

In Proceedings of 5th International Conference on Vehicle, Mechanical and Electrical Engineering (ICVMEE 2019), pages 329-335

ISBN: 978-989-758-412-1

329

1. Wheeled walking mechanism 2. step-push mechanism

3. Dredging mechanism

Figure 1. The picture of robot structure.

It can be seen from Fig.1 that the wheeled

traveling mechanism is in the middle position of the

whole machine, and is the main driving mechanism

for the robot. The structure of the wheeled walking

mechanism is shown in Figure 2. It is mainly

composed of three groups of walking units, and the

three walking units are evenly distributed on the

circumference, each walking unit is controlled by a

motor. In an ideal state, the speed of the three

independent drive motors should be same, so the

control system needs to have better speed regulation

capability, so that the robot can move smoothly and

reliably.

Figure 2. Wheeled walking mechanism.

2.2 The Hardware Configuration of

Control System

According to the purpose and requirements of the

design, a system diagram as shown in Figure 3. The

robot control system is divided into the following

parts according to functions, including control

module, input module, output module and

communication module. STM32 microcontroller is

control module; the input module is composed of a

detecting module, a speed measuring module and a

photoelectric module; the output module is composed

of a motor drive module, a drive motor and an electric

push rod; the communication module is the blue-tooth

module (Qian Xiao Long, 2017). As the core control

device of the system, STM32 MCU is responsible for

the precise control of each motor, the identification of

the host computer commands and the transmission of

data (Xie Shao Chun, 2018). The motor drive module

amplifies the small signal generated by the controller

to a high power voltage level and current level

sufficient to drive the motor. The host computer sends

commands to the lower computer through the blue-

tooth module. At the same time, the information

collected by various sensors and video modules is

also fed back to the host computer.

3. RESEARCH AND SIMULATION

OF SPEED CONTROL SYSTEM

The robot driving control system is the core of

completing the operation successfully, and ensure

that it has an excellent capability of passivity anti-

overturning and obstacle resistance.

Now the motor control system mostly adopts the

method of closed-loop feedback to improve the

performance indexes. The single-closed loop control

with negative speed feedback and double closed-loop

control of current and speed are widely used. Both of

these control methods can make the output speed

follow-up and stable without static error. In this

paper, the simulation of these two control systems are

carried out by Simulink, and compared effects of the

two control systems (Li Xian, 2015).

3.1 PID Control Algorithm

PID is a control method with stable effects and wide

application (Hung Ping, 2017). It is widely used in

control systems with clear mathematical models. The

proportional link can play a role in speeding up the

adjustment; the integral link can weaken the steady-

state error; although the differential link helps to

overcome the system oscillation and reduce the

system overshoot, it is sensitive to the noise of the

input signal, making the control system susceptible to

the high frequency electromagnetic interference.

ICVMEE 2019 - 5th International Conference on Vehicle, Mechanical and Electrical Engineering

330

micro-computer

STM32

Reset

circuit

3.3V

Crystal

oscillator

circuit

Wireless

PC-software

GPS

Onboard

software

Pressure

detection

Photoelectric 5V

Speed

measuring

Motor

drive

12V

Motor5

（dredging mechanism）

Motor1、2、3

（wheeled mechanism）

Electric putter

（step-push mechanism）

Motor4

（

step-push mechanism）

Figure 3. System block diagram.

In practical applications, the three links of

proportional, integral and differential can be

combined according to the needs. In order to achieve

a fast and stable control effect, the proportional and

integral links are finally selected for motor speed

control. The PI controller is consisted of three parts:

measurement, comparison and execution. As shown

in Figure 4, firstly setting a command value, then it is

compared with the feedback value to get the system

deviation. After the PI operation, the control quantity

is output.

e(t)

Controlled object

u(t)

y(t)

Figure 4. Schematic diagram of PI control.

3.2 The Control System Speed of

Single Closed Loop

It can be seen from Figure 5 that the single closed-

loop control system with the negative speed feedback

can obtain the deviation speed (e) by comparing the

commanded speed value (n*) with the feedback speed

value (n). After the corresponding operation is

performed by the PI controller, the output signal

adjusts the PWM duty cycle to provide an appropriate

driving voltage to the motor, and finally adjusts the

motor speed (Wang Gui Yu, 2018) .The control

system can quickly and smoothly make the motor

reach the commanded speed value and maintain the

ability of follow-up; and it will weaken the

fluctuation caused by the load change.

According to Figure 5, established the simulation

model as Figure 6. Setting the given speed is

200r/min, then compared it with the motor feedback

speed, and obtain the deviation speed. After the PI

regulator calculates, the PWM control signal is

applied to the corresponding switch tube, and finally

achieves the purpose of speed regulation (Wang Dian

Jun, 2008).

The Research on Control System of Pipeline Dredging Robot based on Simulink

331

PIDcontroller PWM driver Motor

Speed measurement

Figure 5. Speed control system with speed feedback.

Figure 6. The picture of simulation model.

To simulate motor load changes, the load torque

(TL) outputs in step pulse. The initial load torque is

set to 4 N. m, and then changes every 0.5 s, as shown

in Figure 7.

Figure 7. The change of load torque.

Figure 8 is the result of the speed closed loop

control system simulation, where in Fig. 8(a) is the

torque of the system Fig. 8(b) is the speed of the

system changing with simulation time.

The analysis of simulation results:

As can be seen from Figure 8 (a), the torque at the

start of the motor is large, reaching 7.8 N. m, and then

stabilized near the set value. And the actual output

torque of the motor follows the setting value. At the

point of a, the set value jumps from 4 N. m to 6 N. m,

the actual output torque of the motor fluctuates

greatly.

It can be seen from Figure 8 (b) that the speed of

the motor is obviously overshoot when the motor

starts, and is stable at the set value in 0.2s; When the

load torque changes, the motor speed fluctuates

greatly, after a certain beating, it can return to the set

speed valve.

3.3 The Control System of Current

and Speed Double Closed Loop

As shown in Fig.9, the current loop is an inner loop,

and the speed loop is an outer loop. The output of the

speed regulator (ASR) is the given of current

regulator (ACR). The output of the ACR is used to

adjust the duty cycle of the PWM signal, thus forming

a double closed-loop control system. In this system

the set value of the load torque is the same as the

single-loop simulation model, as shown in Figure 9.

ICVMEE 2019 - 5th International Conference on Vehicle, Mechanical and Electrical Engineering

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(a) Torque diagram of the system.

(b) The speed of the system.

Figure 8. The picture of simulation result.

Figure 9. The picture of simulation Model.

Figure 9 is the result of the double closed loop

control system simulation, where in Figure 10(a) is

the torque of the system Figure 10(b) is the speed of

the system changing with simulation time.

The Research on Control System of Pipeline Dredging Robot based on Simulink

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(a) Torque diagram of the system.

(b) The speed of the system.

Figure 10. The picture of simulation result.

As can be seen from Figure 10 (a), compared with

the speed closed-loop control system, the actual

output torque is more quickly stabilized at 4 N.m. The

motor output torque varies with load torque and there

is a small amount of fluctuation.

It can be seen from Figure 10 (b) that during the

starting process of the motor, the motor speed hardly

has overshoot and is relatively stable compared with

the speed closed loop control system; when the load

torque fluctuates up and down, the influence on the

motor speed is small.

In summary, the double closed-loop control

system has good advantage in speed -following and

strong resistance to load fluctuations. The system

runs smoothly, with excellent static and dynamic

performance. And the PWM pulse width modulation

technology directly regulates the magnitude and

polarity of the output voltage, which can realize the

smooth speed regulation of the system. Considering

that the load will change when the dredging robot is

working, the control method with double closed-loop

is used to weaken the fluctuation caused by the load

change, and the speed control of the robot wheel drive

system is realized.

4. EXPERIMENT

The test platform is mainly composed of the

prototype of pipeline robot, a control system and a

simulated pipeline environment, as shown in Figure

12. This experiment has two steps, such as the test of

whole machine function and the speed test of the

wheel drive mechanism motor.

Figure 11. The experiment platform of robot.

4.1 The Test of Machine Function

In order to verify the stability of the control system

and test functional modules of the robot are working

properly, the function test of the whole machine is

carried out firstly. When the robot is placed in the

horizontal pipeline, sent the corresponding

instruction to test the function realization of the three

parts of the robot. Tested that the robot moved stably

and each function is according to the design; there is

no significant jitter at the moment of start and stop,

indicating that the control system is effective and

reliable.

4.2 The Speed Test of the Wheel

Drive Mechanism Motor

As shown in Figure 5, the wheel drive mechanism

motor adopts a double closed-loop control system

based on PID algorithm. In order to test whether the

motor speed can follow a given change, it sets five

values. The speed feedback time interval is 1ms. The

actual measurement results are shown in Table 1.

Table 1. The results of measurement.

set

r/min

measurement results

r/min

error

160 157 161 163 162 1.8

180 176 181 183 183 1.6

200 196 199 205 203 1.5

220 215 221 224 223 1.3

240 239 241 243 240 1.2

It can be seen that the motor speed average error

is 1.48%, and the overshoot is small. The system has

good follow-up and dynamic steady-state

performance. With the increase of the set speed, the

error of the speed is gradually reduced. It can be

explained that the double closed-loop speed control

system designed has good dynamic-state and steady-

state performance. The system can achieve a response

fast and a stable output.

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5. CONCLUSION

According to the walking mode of the dredging robot,

the design of robot control system and the wheel drive

motor speed control system was carried out. the

simulation analysis and experimental verification

were also carried out, the following conclusions were

obtained.

(1) It has been verified by experiments that the

dredging robot control system has good

controllability and autonomy, and can achieve precise

control of the robot's operation in the pipeline.

(2) The model of two systems are established in

Simulink, which are the control system with single

closed loop and double closed loop, and compared the

effects of the two control systems. The results show

that the double closed-loop control system has good

speed follow-ability, strong resistance to load

fluctuation and excellent, dynamic performance. It is

verified by experiments.

The results show that the control method and

speed control system meet the design requirements

and can realize the precise control of the speed of the

robot wheel drive system.

ACKNOWLEDGEMENT

Thank the support of provincial natural science fund

guidance program (201602620) and general scientific

research project of Liaoning provincial education

department (LJZ2016018).

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