A Study on the Improvement of the Control Circuit Design of Controllable Pitch Propeller

가변피치프로펠러의 제어회로 설계 개선에 관한 연구

Abstract

The control circuit of the CPP applied to FFX Batch-I and LST-II may be capable of generating a backward pitch even when the grounding phenomenon occurs in the other system. The purpose of this study was to improve the CPP control circuit to maintain the pitch even in the event of grounding. Since the CPP control circuit changes the propeller angle with the voltage difference input, it has a design structure that can be vulnerable if the input voltage fluctuates instantaneously. In order to solve the above problem, a terminating resistor is applied to the end of the control wire and a signal converter is applied between the control wires, as a way to improve the CPP control circuit design. In order to verify that there is no problem in improving the CPP control circuit design, the CPP pitch change control was tested in the actual sailing commissioning with LST-II. Since the command pitch value and the feedback pitch value are very similar to each other, it is confirmed that the CPP control circuit is suitable for the control signal transmission because there is no problem in transmitting the control signal.

차기${\bigcirc}{\bigcirc}$함(FFX) Batch-I 및 차기${\bigcirc}{\bigcirc}$함(LST-II)에 적용된 가변피치프로펠러(CPP) 제어회로는 타 계통에서 접지 현상 발생 시 후진피치 발생이 가능할 수 있으므로, 접지 현상 발생 시에도 피치를 유지할 수 있도록 CPP 제어회로를 개선하는 것이 본 연구의 목적이었다. CPP 제어회로는 전압차이입력으로 프로펠러 각도를 변화시키므로 입력전압이 순간적으로 변동이 생기는 경우 취약할 수 있는 설계구조를 가지고 있었다. 위의 문제를 해결하기 위해서 CPP 제어회로 설계 개선 방안으로 제어전선의 끝단에 종단저항을 적용하고, 제어전선 사이에 Signal Converter를 적용하였다. 그리고 CPP 제어회로 설계 개선에 문제가 없는지 검증하기 위해, 차기${\bigcirc}{\bigcirc}$함(LST-II)으로 실제 항해 시운전에서 CPP 피치 변화 제어를 테스트 하였다. Command 피치 값과 Feedback 피치 값 사이는 매우 유사한 값을 보여주고 있으므로, CPP 제어회로의 제어신호 전달에는 문제가 없기에 적합한 개선방안으로 확인되었다.

Fig. 1. Propeller Pitch

Fig. 2. Formula between propeller pitch and angle

Fig. 3. Controllable pitch propeller

Fig. 4. Blade cross section according to propeller pitch angle

Fig. 5. Control system diagram for propulsion

Fig. 6. System circuit diagram between IMCS and CPP LOP

Fig. 7. Control description between IMCS and CPP LOP

Fig. 8. Op-Amp circuit diagram inside MDSD

Fig. 9. Analysis of Op-Amp circuit diagram inside MDSD

Fig. 10. Ground loop caused by leakage current of electrical equipment

Fig. 11. Assuming input voltage cable is grounded

Fig. 12. Circuit analysis if the input voltage cable is grounded

Fig. 13. Assuming current flows from outside to the ground line

Fig. 14. Circuit analysis if current flows from outside to the ground line

Fig. 15. Installation of the terminating resistor at the end of the control wire

Fig. 16. Concept of application of signal converter to CPP control circuit

Fig. 17. Installation of the signal converter

Fig. 18. Signal converter installed in the CPP LOP for LST-II

Fig. 19. Propulsion sea trial test in LST-II

Fig. 20. CPP control signal ID trend

Table 1. Classification of results about the causes of CPP control circuit malfunction

Table 2. Cause and solution about problem

Table 3. Signal converter specification

Table 4. Signal ID list for CPP control signal trend identification

Table 5. Speed table according to lever

Table 6. Command and feedback pitch according to the speed lever