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B.2 System Data Case Study Details Name Imin Imax Iact Iset Vact Vset Pset Pact State Note Error(s) found Description minimum motor current towards the hardware in milliampere maximum motor current towards the hardware in milliampere. actual motor current from the hardware in milliampere actual set motor current from the hardware in milliampere actual speed from the hardware derived by emk sensing of the motor in 0.1°/s or 0.1mm/s set speed towards the hardware in 0.1°/s or 0.1mm/s. actual position from hardware in 0.1°or 0.1mm. the set position of the motion controller in 0.1°or 0.1mm. the movement state of the motion controller. indicates whether the units are 0.1°or mm. This is a readable representation of the error status register. Table B.1: The meaning of the system data that can be found in an error 11 entry. a LUC the pair is made specific for a certain task. Each pair forms the control unit of some movements. The MVR is part of the actuator path and is used to amplify the electronic signal from the processing boards to the motor and brake. SPR: The unit that contains the motor, brake, potentiometer and encoder. The former two are the actuators of the movement. The latter two are used as sensors and constitute the start of the sensor feedback path of the control loop. Frontal Stand: The mechanical body that has the collimator and flat detector on its far ends. It can be positioned relative to the patient in order to transmit X-ray through the patient. B.2 System Data Table B.1 shows the meaning of the system data that Philips Cardio-Vascular X-Ray Systems produce in case error 11 occurred. B.3 Behavior Below follows a description of the behavior of the system in natural language. A formal specification is the corresponding Lydia code that is listed in appendix C. The desired behavior is realized by three nested control loops. The writing below follows the convention to use this font for all referenced names of signals and FRUs (also shown in Figure 5.3). The first control loop controls the position. The setpoint for the position (Pset) is determined by integrating the requested speed (V_user). The (nominal) error (e_pos) is calculated by subtracting the actual position (Pact). This error is used by position controller CTR_pos to calculate a setpoint for the speed (Vset) in such a way that that the stand passes position Pset at the requested speed. Therefore, Vset depends on e_pos, V_user and Vfw. The latter is a feed forward variable that is determined during calibration. The next control loop controls the speed. Figure B.2 shows the dynamics that should be thought of when controlling the speed. It can be divided in a left and right part, both parts representing a lever. 86
Case Study Details B.4 Full List of Examined Fault Scenarios Legend Fz1 : Gravity on the left lever. d1 : Arm of the left lever. t1 : Torque exerted by Fz1 * d1. Fz2 : Gravity on the right lever. d2 : Arm of the right lever. t2 : Torque exerted by Fz2 * d2. Fm : Force caused by the motor. dm : Arm of the motor. tm : Torque exerted by the motor (Fm * dm). Figure B.2: Forces and torques on the frontal stand. Gravity exerts torques on both the left (torque t1) and right (torque t2) lever of the frontal stand (Stand). These two torques should be complemented with a third torque exerted by the motor in order to control the angular acceleration of the stand. This acceleration is used by the speed controller CTR_speed to enable the controlling of the speed. This controller uses a table to determine what current it has to set (Iset) in order to achieve a certain acceleration at a particular position 1 . So, the difference between the speed setpoint (Vset) and the actual speed (Vact) results in a certain desired acceleration (e_sp). This acceleration is combined with the current position (Pact) in order to lookup the associated current setpoint Iset. Here starts the third and final control loop. It is responsible for controlling the current at setpoint Iset. In order to do so it requests a certain current of the MVR(forward) 2 that has a circuit with the Motor/Brake. The actual current (Iact) on this circuit is measured by means of a ampere meter and led back to the current controller CTR_current. Because the current is flowing on this circuit the motor exerts a torque (Tm). The torque resultant makes that the stand will rotate at a certain speed to a certain position. The speed can be measured by the MVR(feedback). And by leading the signal Vact_analog back to the controller (Vact) the speed control loop has been closed. The closing of the outer position loop is done by measuring the real position. For this purpose a potentiometer and encoder (Potmeter/Encoder) have been assembled upon the rotating axle. When rotated, these components output a voltage. The signals of the potentiometer and encoder are combined in order to achieve a certain accuracy (and to do error detection). The LUC_extension(feedback) contains a AD-converter to digitize the analog signal and lead it back to the controller (LUC_extension(controller)). The position controller will use this value (Pact) once again to calculate the (nominal) position error. B.4 Full List of Examined Fault Scenarios Table B.2 shows the fault scenarios that are considered in the work for this thesis: S1-S11: presented in the thesis, table 5.4 and table 5.6. 1 Note that when the Stand rotates the arms of the left and right gravitational torques change. In order to keep the speed constant the torque that the motor has to generate has to change likewise. 2 Note that both occurrences of MVR denote the same FRU. It is only a logical decomposition. The same holds for the LUC Extension FRU. 87
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Automated Fault Diagnosis at Philip
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© 2006 W.M. Lindhoud. Document gen
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Preface The work presented in this
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CONTENTS 4.4 Modeling . . . . . . .
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List of Tables 3.1 Evaluation appro
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1.1 Fault Diagnosis Introduction Fi
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1.2 Automated Fault Diagnosis Intro
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1.5 Outline of the Thesis Introduct
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Chapter 2 State-of-the-Practice Fau
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State-of-the-Practice Fault diagnos
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Chapter 3 Automated Fault Diagnosis
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Automated Fault Diagnosis 3.1 Overv
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Automated Fault Diagnosis 3.3 Off-l
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Automated Fault Diagnosis 3.5 Model
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Automated Fault Diagnosis 3.6 Evalu
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4.1 Fundamentals Model-Based Fault
Page 50 and 51: 4.2 Model-Based Diagnosis with LYDI
Page 52 and 53: 4.3 Basic Assumptions Model-Based F
Page 54 and 55: 4.4 Modeling Model-Based Fault Diag
Page 56 and 57: 4.4 Modeling Model-Based Fault Diag
Page 58 and 59: 4.5 Entropy Gain Model-Based Fault
Page 60 and 61: 4.6 MBD on the Power Supply Model-B
Page 63 and 64: Chapter 5 Diagnosing the Beam Prope
Page 65 and 66: Diagnosing the Beam Propeller Movem
Page 83 and 84: Chapter 6 Conclusions and Recommend
Page 85: Conclusions and Recommendations 6.2
Page 88 and 89: BIBLIOGRAPHY [12] Johan de Kleer an
Page 91 and 92: Appendix A Glossary of terms In thi
Page 93 and 94: Glossary of terms • Diagnostic Pe
Page 95 and 96: Glossary of terms • Model: an abs
Page 97: Glossary of terms • System: an en
Page 102 and 103: B.4 Full List of Examined Fault Sce
Page 104 and 105: B.5 Discretization of Implementatio
Page 106 and 107: C.1 The Synthetic Models that are U
Page 108 and 109: C.2 Model of the Power Supply Examp
Page 114 and 115: C.3 The Models Constructed for the
Page 131 and 132: Appendix D State-of-the-Future Faul
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