Abstract: Proposed about machine shop truck’s automatic shift control question, gave coordinated other input output circuit with the monolithic integrated circuit to complete in the controlled process the signal changes delivers, input processing, the procedure judgment, the power amplification output concrete electric circuit and the method, introduced in the system front end the input circuit and the monolithic integrated circuit control circuit’s basic constitution and the principle of work, simultaneously has given system’s software flow chart and the initialization working routine detailed list.
2.1 front end input circuit’s constitution
This automatic shift system altogether has two speed parameter values to need to survey, respectively is the locomotive speed and the diesel engine rotational speed, Figure 1 is front end in the input circuit the locomotive speed input section, the diesel engine rotational speed and the locomotive speed input circuit is the same.
In Figure 1, locomotive’s speed first carries on the examination by the Lahuoer velocity generator, this kind of sensor’s characteristic is the work is stable, the frequency is high, compared with suitable railroad vehicles use. What the Lahuoer sensor outputs is a signal impulse, this signal’s frequency and locomotive’s speed is proportional. In order to enhance electric circuit’s reliability, the sensor outputs the pulse needs to pass through a pulse shaping electric circuit. The pulse shaping electric circuit take integrates the block 8751 as the core composition. 8751 are switching valve integrated circuits, when inputs for the high level, the output is also the high level, otherwise, the output is the low level. Because 8751 interior have their power amplification and the voltage-stabilizer circuit, and may repair and maintain in the input pulse profile the loss and the flaw, therefore may obtain one very stably in 8751 out-ports, the profile complete pulse square-wave frequency code. For makes the locomotive speed and diesel engine’s rotational speed the comparison, must transform both’s frequency code the voltage signal. Therefore the frequency code should input again to the frequency voltage switching circuit, this electric circuit take the LM331 integrated circuit as a core, its output’s voltage value is 6~8V, and the output voltage and signal impulse’s frequency is proportional. Because after transforms the voltage signal is the pulse which outputs by the initial sensor undergoes a series of processing to result, therefore this signal has represented the corresponding locomotive speed or the diesel engine rotational speed. Thus, carries on these two voltages the comparison to be possible to obtain the locomotive and diesel engine’s speed relations. But before comparison, to enhance the comparison the precision, but also needs a voltage signal input voltage amplification electric circuit, thus has an output impedance quite great voltage value to enhance electric circuit’s stability.
2.2 Schmidt voltage comparator
Through the comparison locomotive speed and the diesel engine rotational speed may determine whether the locomotive does need to carry on shifts gears, when locomotive’s speed is lower than diesel engine’s speed, locomotive movement in 1 grade, when the locomotive speed is bigger than the diesel engine speed, the locomotive shifts gears to 2 grades. Compared with represents two speeds the voltages is completes by the Schmidt voltage comparator, not only it may compare two voltage signals, but may also in time 2 grades to 1 grade of transformations produces a Schmidt to return stagnates.
Shown in Figure 2 is shifts gears the signal concrete electric circuit the locomotive speed and the diesel engine velocity voltage signal conversion. In the chart, Ua and Ub respectively are represent the locomotive speed and the diesel engine speed voltage signal. Two operational amplifier F1 and F2 meet the voltage comparator’s form. Two out-ports input monostable trigger’s S and the R end separately, the monostable trigger’s output passes through an electro-optic to isolate component’s processing then to turn shifts gears the signal. In Figure 2, the F1 two input voltage and the F2 opposition end input voltage directly meets Ua or Ub. But F2 synchronism input end by R1 and R2 after the Ub differential pressure inputs, because R1 is 560Ω, but R2 is 10kΩ, the actual input voltage is 0.95Ub. Usually locomotive’s initial files position is 1 grade, increases gradually along with the locomotive speed, when its speed is bigger than the diesel engine rotational speed (i.e. Ua>Ub), F1 outputs the high level and joins to the monostable trigger’s S end, regarding F2, by U2=0.95Ub, may result in Ua>U2, therefore F2 outputs the low level to the list steady trigger’s R end. Thus, the trigger will output the high level, the control circuit outputs trades 2 grades of signals, thus causes the following monolithic integrated circuit electric circuit to carry on shifts gears. When the locomotive speed drops to is smaller than the diesel engine rotational speed, namely Ua<Ub, but time Ua>0.95Ub, F1 outputs the low level, but as a result of this time F2 synchronism input end U2=0. the 95Ub, F2 out-port was still the low level, like this, because list steady trigger’s S and the R end inputs the low level, therefore its out-port still maintained the original condition, but does not output shifts gears the signal. When Ua<0. when 95Ub, the F2 out-port transforms into the high level, this time list steady trigger’s input end S end for low level, but the R end is the high level, thus causes trigger’s output is the low level, thought that the locomotive provides from 2 grades to 1 grade shifts gears the signal. May see by the above-mentioned electric circuit work process: When from 1 grade to 2 grades, once the locomotive the speed arrives at the shift point, then shifts gears immediately, but from time 2 grades to 1 grade, is the locomotive arrives shifts gears time spot speed 95% only then carries on shifts gears. This delay time may avoid the locomotive being possible, because vibrates or other factors causes shifts gears frequently and is unstable.
3 monolithic integrated circuit electric circuits
What the Schmidt voltage comparator outputs is shifts gears the signal after front end input circuit processing, but after that the monolithic integrated circuit electric circuit’s function is according to shifts gears the signal to unify locomotive’s other parameters to decide whether the locomotive does carry on shifts gears.
3.1 monolithic integrated circuit electric circuit’s constitution
The monolithic mechanical and electrical route 80C31 chip, 6264 composition’s non-erasable storage ROM, display lamp (locomotive status indicator electric circuit) and is composed of 74HC373 the actuation LED based on 8155 input output circuit. Is quite complex as a result of the complete monolithic integrated circuit electric circuit, therefore has only given the participation automatic shift control part, its electric circuit connection as shown in Figure 3.
When this electric circuit works, the locomotive shifts gears the signal to pass through electro-optical coupler 4N26 to input to monolithic integrated circuit P1 the mouth P1.5 foot, the use electro-optic coupler’s goal avoids the unwanted signal which passes on from the power source. By integrated block 74HC373 actuation 8 LED, may demonstrate the locomotive locates the files position as well as is moving segment, thus causes the pilot and the technology servicemen understands locomotive’s condition. 8155 functions are the output control shift valve work signals, this signal after passing through the output enlargement chip the power amplification may the direct drive shift gears the functional element to realize automatic shift. Monolithic integrated circuit P2.5~P2.7SAN pin signal after the 74HC138 decoding, may take the non-erasable storage, 8155 input/output chip as well as 74HC373 separately selects patches or strips of land as worth saving for seed the signal, these three pins constituted visited time these three component’s high three bit address.
3.2 software designs
After receiving shifts gears the signal, according to the program directive, the monolithic integrated circuit will unify several other locomotive parameter to decide whether to carry on shifts gears, these parameters including shift gears to permit the signal to be whether effective, whether to have the parameter to surpass the locomotive warning value and so on. If does not have the question, the locomotive will carry on shifts gears.
Shown in Figure 4 is this locomotive shifts gears system’s software flow chart. Its software initialization routine is as follows:
START:mov a,#03H establishment condition character, causes 8155
4 output amplifying circuit
The output amplifying circuit is mainly composed of some power amplification switching valve, may use in completing to the monolithic integrated circuit output signal further enlargement, shifts gears by the direct drive functional elements and so on solenoid valve. This electric circuit is quite simple, here no longer relates in detail.
Reference
1. Ji Zongna .8031 monolithic integrated circuit practical connection technology. Beijing University of Aeronautics and Astronautics Publishing house
2. He Limin .MCS51 series monolithic integrated circuit application system design. Beijing University of Aeronautics and Astronautics Publishing house
3. Linde is outstanding. Electrical test technology. Mechanical industry publishing house
