Introduction
The airplane power supply system is the need redundant reliable complicated system, its working conditions very severe, strong vibration, varying duty, and the power source quality request is high. Some airplane uses the single Taiwan generator electrical power system, the centralized power distribution way, opens the type supply network. l 12kW cocurrent starter generator, 2 zinc silver accumulator cell and the ground supply socket directly to the power bay bus bar power supply, on the power bay bus bar meets has the large capacity current collector. At present, the power supply system only depends on the generator breakdown signal light instruction breakdown, lacks the real-time aircraft-borne failure detection and the date recording system, does not favor real-time keeps abreast of the power supply situation and carries on the ground check promptly.
1 power supply system constitution
The aircraft-borne power supply system is composed of following several parts:①Generator,②Generator exciting winding,③Reverse current cutout,④Carbon membrane type voltage regulator,⑤Stable transformer,⑥Generator electric switch,⑦Aviation accumulator cell,⑧Current collector. Its schematic diagram like chart 1.
2 aircraft-borne power supply system use present situation
The airplane current collector request power supply system provides the high grade electrical energy, guaranteed that normally and displays equipment’s performance fully, completes the predetermined task; Simultaneously must guarantee that inferior does not damage the current collector because of the power supply quality. This request power supply pulsating voltage strict control in certain scope, prevents to the wireless apparatus and other electronic installation’s conduction and the radiated interference. In the airplane launching process, the current collector works one after another, the power supply system variation of load is very this time big, causes the voltage pulsation.
At present, the aircraft-borne power supply system only depends on the trouble lamp instruction breakdown, when the bus bar voltage is lower than 24V, the breakdown lights lighten. But this time left the pilot to carry on special situation processing the time already to be very few, and could not locate the failed part accurately, brought the enormous threat for the flight safety. If can in the flight be specially in the launching process the real-time monitoring power supply system various key component’s voltage condition, when various sampling points pulsating quantity surpasses the permissible value, promptly reports the breakdown information, simultaneously in flies in the senate recording system to record these situations, can carry on the special situation processing buy time for the pilot, may also supplies the precious information for the failure predication and the fast trouble clearing.
3 fault tree analyses
This system’s typical breakdown includes: The power line voltage surpasses the stable state voltage limit, the voltage unstable and the generator does not supply power and so on. The first two kind of breakdowns may act according to the bus bar voltage judgment, the breakdown reason are obvious, may judge by the power failure indicating lamp, does not need the detailed Canadian analysis. But causes the generator not to supply power the breakdown factor to be many, like the reverse current cutout does not work, the reverse current cutout control circuit has the breakdown (i.e. electricity generation mechanical and electrical gate to have breakdown), the generator itself has the breakdown, the generator exciting winding electric circuit abruption or the carbon membrane voltage regulator coal column electric circuit abruption and so on. If divides into a breakdown reason’s electrical power system a pattern class, and does not subdivide the reverse current cutout not to put through is because its breakdown creates because its control circuit creates, then this system may divide into four pattern class s1, S2, with S3, So expressed that the normal power supply pattern class, as shown in Figure 2.
So long as if judgment electrical power system whether to supply power, so long as then examination bus bar voltage. If must carry on the fault location, should obtain more information, must increase check point F and B. When generator normal power supply, bus bar voltage in 27V~29.5V. If the generator cannot supply power normally, only supplies power by the accumulator cell to the bus bar, its loss of voltage to 24V about. When generator normal electricity generation, voltage VF is 27V~29.5V. If the voltage regulator is normal, but the generator exciting winding is not normal, then the generator end should have the residual magnetism voltage (usually to be bigger than O.5V), the exciting winding end should also have the voltage, namely UF≠O, UR≠O; If this time voltage regulator coal column electric circuit abruption, then on the exciting winding does not have voltage UB=O. When the generator has loses magnetism, breaks breakdowns and so on axis or armature coil abruption, generator voltage UF must be zero. From this may determine the system each voltage normal value scope.
4 ADS8O3 and TMS32OF2O6 chip synopsis
TI Corporation’s 16 fixed-point DSP TMS32OF2O6, is one kind of low power loss component, has used the improvement Harvard structure, some 1 program bus and 3 data buses, the stream line operation, has the highly parallel 32 arithmetic logic unit, 1 6×1 6 bit parallel hardware multiplier, the internal memory, the internal outside data and highly the specialized set of instructions. The F2O6 performance characteristic is as follows①The instruction cycle is 5Ons;②Addressable 224K the storage space 164 K procedures, the data and the I/O space as well as 32K may expand the data space;③The internal integration has 4.5K RAM and 32K Flash;④A rich internal peripheral device synchronization serial port, asynchronous serial port, phase-locked loop, software waiting status generator;⑤Sound code downward compatible TMS32OC25, upward compatible TMS32OC5X;⑥The formidable set of instructions - monocycle while/Canada, the block moves the multi-conditional transfer and the reassignment, the position inverted order addressing.
BB Corporation promotes the ADS8O3 chip is 12, 5MHz, the parallel high speed A/D switches, has the high signal-to-noise ratio, the low degree of distortion, the low power loss, the input range change to be nimble and merits and so on input overflow alarm. The ADS8O3 internal integration has the wide band linear sampling retainer, has guaranteed under the Naikuisite frequency chip fine performance [2] ‘. ADS8O3 internal structure including sampling retainer 12 bit parallel modulus switch, error correction logic, reference source and working pattern choice and so on. The ADS8O3 switching time for 2OOns~100μs, the data which the sampling maintains after 5 action cycles transforms completes. Succession as shown in Figure 3. Figure 3 mark meaning and value like table 1 arrange in order.
5 aircraft-borne power supply diagnosis system circuit design
For the real-time monitoring aircraft-borne power supply system various key component’s voltage pulsation, may know by the fault tree analysis, may in the bus bar, the accumulator cell positive electrode, F spot and B spot takes the voltage sampling, carries on the real-time processing after high speed a/d conversion evacuation DSP. This delivers at the same time the sampled data flies the senate memory to carry on the memory: On the other hand carries on various times sampling voltage pulsating quantity and the normal value the comparison. If surpasses the permissible value system to carry on reports an emergency and instructs the trouble location.
ADS803 and the F206 connection, forms a high speed data gathering system, for the following processing gathering data. Refers to ADS803 the work succession chart, the ADS803 switching cycle may for 200ns~100μs, therefore may have the 10kHz~5MHz any sampling frequency. F206 CLKOUTl output clock signal, after the frequency division meets person ADS803 CLK, takes the sampling clock. ADS803 and F206 coordination’s succession as shown in Figure 4, CLKOUTl is the DSP work clock, takes is the 20MHz, ADS803 work clock is passes through 4 frequency divisions by CLKOUTl to come, is 5MHz, their rise along maintains a synchronization. Regarding each ADS803, in each clock has 5 cyclical sampling data conversion to complete in advance, and retains effectively. F206 reads the data from the memory only to need a CLKOUT1 cycle, therefore F206 only need every other 4 CLKOUTl cycles from the identical ADS803 read data, like this then fully use ADS803 the conversion rate, may also avoid the sampled data being redundant. According to the succession, F206 may in t12, read the bus bar place sampled data, reads the accumulator cell extreme sampled data in t13, reads F spot place sampled data in t14, reads B spot place sampled data in f15, reads the bus bar place sampled data in f16, so repeat in cycles. Diagnosis system’s electric circuit diagram as shown in Figure 5. In Figure 5 shows logic, BR earths effectively, chooses the exterior global data space. In this electric circuit ADS803 is mapped the data area, may use reads the data to result in the instruction to read A/D. This method instruction are few, may with every effort using a/D speed, reduce the time which, because the interrupt mode response interrupt needs (F206) from to have the external interrupt to request the read interrupt vector needs 8 clock cycles at least), can thus further raise the sampling speed. F206 reads 4 sampling points in turn the voltage sampled data, carries on the analysis to the obtained data, and delivers the data flies the senate memory to take the historical data retention.
Conclusion
This article has analyzed the aircraft-borne power supply diagnosis system’s characteristic with the fault tree, has analyzed the ADS803 high speed a/d conversion characteristic and the DSP TMS320F206 parallel characteristic. Applies them during the aircraft-borne power supply system failure diagnosis. Selects the appropriate sampling point, undergoes high speed data gathering, may through fly the senate to interpret the software, real-time diagnoses the aircraft-borne power supply system’s breakdown precisely. This system may apply in some airplane power supply system performance monitoring and the fault repairing, after improvement may also apply in other model airplane.
