Design of Shipborne Radar Turntable Servo System

Chao Zhao

, Jiaguo Liu

and Yu Tang

Beijing Institute of Environmental Features, Beijing 100854,China

Keywords: Servo Turntable; Triple Closed Loop; PID Control.

Abstract: In view of the high attitude stability requirements of shipborne radar turret under sea conditions, the

hardware and software of the two-axis shipborne radar turret servo control system were designed.DSP chip

TMS320F2812 and FPGA chip were used as the servo control core for controller design, and Copley motor

drivers were used to drive the motors. The control software used the "current + speed + position" triple

closed loop control method and PID control algorithm was developed with CCS3.3 development platform.

The system triple closed loop control model was established and simulated with the Simulink module of

Matlab, and the result of 30 ms response time of the system was derived. Finally, the experimental

verification shows that the design of shipborne radar turntable servo control system meets the design

specifications.

1 PREFACE

The ocean is an important battlefield for the current

global power game, and the number and

advancement of warships are concentrated

expression of its competitiveness. Shipborne radar

plays an important role in target detection and early

warning. The warship is generally equipped with

high-precision shipborne radar. The radar antenna is

installed on the servo turret, and the sway of the hull

is isolated by the movement of the turret, so that the

radar antenna obtains stable relative inertia space,

and the target is searched, positioned and tracked

under the control command. The servo control

system is an important part of modern shipborne

radar, and its performance directly affects the radar

detection and tracking accuracy (Wang Yuqian, Gu

Weijie and Li Guiqiu, 2017).

Ji Wei, from Southeast University, conducted

theoretical research and experimental verification on

the techniques of visual axis stability control and

search tracking in the gyro stabilized photoelectric

tracking system (Ji Wei, 2006). Xu Tao, from

Changchun Institute of Optics and Mechanics,

Chinese Academy of Sciences, proposed an initial

calibration method for target tracking turntable

based on coordinate transformation, which is used to

improve the tracking accuracy of the moving base

photoelectric tracking system (Xu Tao and Li Bo,

2013). Ji Dong, from Aerospace Science and

Technology Second Research Institute, adopted a

method of adding disturbance observers on the gyro

speed loop to reduce the speed deviation caused by

the frictional interference of the turret and the carrier

disturbance, ensuring the stability of the stable

platform speed (Ji Dong, 2013).

2 SYSTEM BASIC

COMPOSITION AND

WORKING PRINCIPLE

The turntable servo control system is mainly

composed of mechanical structure, servo controller,

driver, servo motor, detection component, and

display control (Liu Sheng, Peng Xiafu and Ye

Guizhen, 2001). The shipborne radar turret is a two-

axis servo turret, azimuth axis and pitch axis. The

servo control loop consists of two independent

control systems, the azimuth control system and the

pitch control system. The basic composition of the

turret is shown in Fig.1.

Zhao, C., Liu, J. and Tang, Y.

Design of Shipborne Radar Turntable Servo System.

DOI: 10.5220/0008385802990305

In Proceedings of 5th International Conference on Vehicle, Mechanical and Electrical Engineering (ICVMEE 2019), pages 299-305

ISBN: 978-989-758-412-1

299

Figure 1. Block diagram of the stable platform.

The two-axis shipborne turntable controller

controls the motion state of the servo motor by

receiving the off-target amount transmitted by the

host computer and the feedback signals of the code

wheel and the gyro to realize the search and tracking

function of the target Zheng Yanwen, Wang Yuyu,

Lin Lin, Huang Yuxin, Fan Genxin, 2013). In this

design, the radar needs to detect and locate the air

target, and the positioning accuracy of the turntable

is high. The performance requirements of the

turntable are shown in Table 1.

3 SERVO SYSTEM DESIGN

The azimuth control system is composed of a servo

controller, a driver, a servo motor, a code wheel and

a gyro. The pitch control system is composed of a

servo controller, a driver, a servo motor, a code

wheel, a gyro, and a limit switch. The overall block

diagram of the servo system is shown in Fig.2.

Figure 2. Overall block diagram of the servo system.

3.1 Servo Controller Design

The controller is based on DSP and FPGA chips.

The main functions of the servo controller include

control algorithm, signal acquisition, communication

with the terminal, and control of peripheral devices.

The DSP uses TI's TMS320F2812 with a clock

frequency of 150 MHz, an on-chip 128K×16 Flash,

integrated the motor control peripheral event

manager (EVA and EVB), serial communication

peripherals and a 12-bit 16-channel ADC with 56

general purpose I/O (GPIO). In order to achieve

high-precision control, the 12-bit ADC of DSP is

used as a backup. The 16-bit AD7656 is selected as

the sampling AD to collect the gyro signal. The 16-

bit DAC7744 is selected as the DA output to control

the Copley controller to drive the servo motor. The

servo control circuit diagram is shown in the Fig.3.

Table 1. Shipborne radar turntable performance indicators.

Structure

Type

Rotation Range

/ （）

Range of Rotation

-1

/s（（））

Maximum Angular

Acceleration

-2

/s（（））

Positioning

Accuracy

/ （）

Azimuth

Axis

0~360 0.1~25 30 0.02

Pitch

Axis

-10~100 0.1~20 30 0.02

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

300

Figure 3. Schematic diagram of servo control circuit.

The servo controller sends the generated control

quantity to the driver through the DA port, and the

driver power-amplifies the signal to drive the servo

motor to drive the platform to perform

corresponding motion. The photoelectric encoder is

installed as the speed sensor and the position sensor

at the end of the platform swing mechanism. The

gyro measurement base motion information is

installed on the platform base. The positioning

orientation system is installed to obtain the angle

information of the stable platform in the inertial

space, and the limit function is realized by the

photoelectric switch.

3.2 Servo Drver Selection

The servo drive is one of the cores of the servo

control. Copley's industrial servo driver is selected.

The analog signal output from DA is transmitted as a

control command to the Copley servo driver, and the

position information and speed information returned

by the drive are accepted. The main interface is the

motor control interface, RS232 communication

interface, CAN communication interface, dual

encoder interface, 9 IO input interface, 4 IO output

interface, and its characteristics are as follows:

1) It has a dual encoder interface (motor encoder

interface and load encoder interface);

2)The drive control system adopts triple closed

loop structure (current loop, speed loop and position

loop), each closed-loop system parameter can be set,

and the maximum value of the parameter can be

limited to facilitate safe debugging;

3) It has strong environmental adaptability, and

the working environment temperature is -25 °C ~ 70

°C.

3.3 Servo Control Software Design

The software design of the controller mainly

includes the communication software of the upper

computer and the control software of the lower

computer (Wu Tianzhu, 2010). In this study, the PID

control algorithm is used to realize the “current+

speed+ position” triple closed loop control, so that

the response speed and tracking accuracy of the

turntable control system meet the performance

requirements.

The servo control software is based on DSP

system development, and the development tool

software is CCS3.3. The main program mainly

includes two parts of initialization and loop running

program. The initialization includes hardware and

system initialization and servo running environment

initialization. The main flow chart of the servo

control program is shown in Fig.4. It mainly

includes the main function modules such as serial

communication module, motor control module and

servo control module.

Design of Shipborne Radar Turntable Servo System

301

Figure 4. Servo control software main program flow char.



Figure 5. Schematic diagram of segmentation variable parameter PID control.

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302

3.4 Code Disk Position Loop Control

Strategy Design

The position and position control adopts the

segmentation variable parameter PID control

algorithm in Fig. 5, which has the advantages of

simple algorithm, good robustness, and the ability to

balance both fast performance and stability

performance.

In order to achieve precise positioning of the

turntable, a segmentation variable parameter PID

control algorithm is adopted in the positioning

control, and the error is divided into three segments

according to different sizes of position errors during

positioning.

(1) When







, the P controller is used at

this time,

1pp

k

, so that the response time of the

system is faster and the overshoot is small.

(2) When







, use the PD

controller,

2pp

k

ii2

Kk

, to speed up the

system adjustment speed, shorten the system

adjustment time, and reduce the steady state error.

(3) When







, use PID controller,

3pp

k

3ii

Kk

3dd

Kk

,to improve the

overall control accuracy of the system.

Among them,

123

pp p

kkk

kk

k 

4 SYSTEM SIMULATION AND

ANALYSIS

In order to facilitate the analysis of the relevant

performance of the shipborne servo radar turntable

control system, the motor model and the three closed

loop control model of the azimuth axis are

established, and the model is simulated and

analyzed.

4.1 Motor Model

According to the selected servo motor, driver

parameters and the magnitude of the received

torque, the transfer function of the azimuth motor

current and angular velocity is:

(s)

0.0015 10





(1)

4.2 Triple Closed Loop Control Model

Simulation

The step response model of "current + speed +

position" triple closed loops and the sinusoidal

signal tracking curve are established in the Simulink

module of Matlab software. The sinusoidal signal

tracking simulink simulation model is shown in Fig.

Set the input signal to a sinusoidal signal with a

magnitude of 1



, a frequency of 0.5 Hz, and a

simulation time of 6 s. The sinusoidal signal tracking

curve of the system can be obtained through

simulation, and the sinusoidal signal tracking curve

is shown in Fig. 7. According to the image display,

the system tracking performance is good.

Set the input step signal to 1

/s

, and perform

mathematical simulation on the system. The step

response diagram is shown in Fig.8. It can be seen

that the speed loop response time is 30 ms, the rise

time is 3 ms, the peak time is 6 ms, the transition

time is 25 ms, and the overshoot is 2.25%.

Figure 6. Sinusoidal signal tracking simulink simulation model

Design of Shipborne Radar Turntable Servo System

303

Figure 7. Sinusoidal signal tracking curve

Figure 8. Step signal response curve.

5 CONCLUSION

This paper introduces the hardware and software

design of the shipborne radar servo turntable control

system, adopts the "current + speed + position" triple

closed-loop control mode, and uses the

"TMS320F2812+FPGA" chip as the servo control

core to design the controller through Copley. The

selection of the motor driver realizes the driving of

the motor; through the segmentation variable

parameter PID control algorithm, the high-precision

positioning requirements of the shipborne radar

turntable are realized, and the relevant control

software design is carried out by using the CCS3.3

development platform.

The mathematical model of the servo system of

the turntable is established. In the simulink module

of Matlab, the three-closed control model of the

system is simulated mathematically, and the

response time of the step signal of the system is 30

ms. by simulating the tracking of the sinusoidal

signal, the tracking performance of the system is

verified.

At the same time, the relevant indicators are

verified through experiments, and the actual

indicators meet the requirements of the design

indicators.

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2123.

Liu Sheng, Peng Xiafu and Ye Guizhen, Modern servo

system design, (Harbin Engineering University Press,

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Control System of Shipborne Radar Two-Axis

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

304

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