FAULT DETECTION AND FAULT DIAGNOSIS OFPNEUMATIC ACTUATORS:A CASE STUDY REPORT ON PMFD Submitted by: Anand Kumar 11RE60R04 Vikram Singh 11EE64R03
CONTENTS1. Introduction2. Faults of Pneumatic valves3. Results4. Conclusions5. References
1 INTRODUCTION Pneumatic actuator for linear motion with power supply: a) schematic; b) energy flow scheme; c) two-port representation. 1: AC motor, 2: air compressor, 3: pressure-relief valve, 4: air filter with water trap, 5: air storage (accumulator), 6: 4/3 proportional valve, electrical solenoid actuation, spring return, 7: double-rod cylinder; 8: diaphragm drive with spring return
CONTD..Pneumatic actuators consist of an airflow valve and an actuatingdevice transforms the pneumatic energy into mechanical energy.The valve is connected to the pneumatic pressure line manipulatesthe pressurized air flow to the actuating device.The valves are either proportional-acting valves or switchingvalves.Proportional acting valves allow a continuous manipulation of theairflow either electrically by two solenoids or pneumatically withone air flow modulator and return spring.Switching valves are electromagnetic devices and operate withPWM at high frequencies to generate actuator position.
2 FAULTS OF PNEUMATIC VALVES Faults of pneumatic valves may arise in the air supply air supply line piston or diaphragm actuators valve stem sealing and plug–seat combination Cross-sectional view of a pneumatic valve with an electro-pneumatic position controller
Typical faults of pneumatic flow valves and fault-detectioncoverage in dependence on instrumentation- x:yes, 0: no
2.1 MODELS OF PNEUMATIC VALVES The parameters for the chamber pressure are time-variant and depend on the motion and the position of the diaphragm.
The dynamics of the mechanical part of the valve, the diaphragm, the valve stem and the plug are governed by the balance of forces:where mv :mass of the stem and connected parts, cs : spring constant, dv ,fc :coefficients of the viscous and dry friction of the stuffing box and guidance Fext: external forces, mainly the force through the flowing fluid
RESULTS Sensor Fault on intake air flowSensorFault onManifoldpressureFault inManifoldDue to airleak
CONCLUSIONS • The fault detection strategy is designed for threeimportant faults as from manufacturer point ofview. • Observed that after initial transient effect theperformance of each residual is effective.
REFERENCES 1. J. A. F. Vinsonneaut, D. N. Shieldst, K. J. Bumhamt. Improved SIengine modeling techniques with application to fault detection .Pages 719-724, Proceedings of 2002 IEEE international Conferenceon Control Applications, September 18-20.2002 Glasgow, U.K. 1. R. Iserman. Fault Diagnosis Systems An introduction from faultdetection to fault tolerance, Chapter 11 Fault detection with stateobservers and state estimation, Springer, Berlin. 1. Graham C. Goodwin, Stefan F. Graebe, Mario E. Salgado,Control system design, Chapter V Advanced SISO control,Prentice Hall, New Jersey 1990. 1. K.P. Mohandas. Modern control engineering, Sanguine TechnicalPublishers. Bengaluru. 2006.