CN102425503B - Rail pressure pre-control system and control method based on hardware constant current control - Google Patents

Abstract

The invention relates to a rail pressure pre-control system based on hardware constant-current control and a control method. The system comprises an ECU (electronic control unit) internal timing interruption module, a reference current inquiry module, a current distribution module, a constant-current drive pulse width capturing and calculation module and a PWM (pulse width modulation) drive pulsewidth calculation module; timing interruption is triggered under effects of the ECU internal timing unit; the reference current inquiring module is used for calculating the reference current of a measurement unit; the current distribution module is used for dividing the reference current into a current regulating value and a current setting value and transmitting the current regulating value and the current setting value; the constant-current drive pulse width capturing and calculation module is used for capturing constant-current drive pulses, calculating the width of the constant-current drive pulses, and simultaneously transmitting calculation results to the PWM drive pulse width calculation module; and the PWM drive pulse width calculation module is used for calculating the drive pulse width of a PWM drive unit and transmitting calculation results to the PWM drive unit. In the method, ECU internal timing interruption produced by a timer in an ECU and external interruption producedby the triggering edge of the constant-current drive pulses are implemented in operation of main programs of ECU control. Accurate control and high response speed can be achieved, the difficulty and the complexity in software control can be reduced simultaneously, and hardware resources of processors can be saved.

Description

Rail pressure pre-control system and control method based on hardware constant current control

technical field

The invention relates to a rail pressure pre-control algorithm. In particular, it relates to a rail pressure pre-control system and control method based on hardware constant current control of a common rail engine fuel injection system based on constant current control.

Background technique

Usually the rail pressure control logic mainly includes the following parts: actual rail pressure measurement and filtering, rail pressure control target value calculation, rail pressure controller PID design, rail pressure control state machine design, rail pressure control actuator output control, etc. The basic idea is: according to the actual measurement of the rail pressure value through a suitable filter algorithm as the feedback value of the closed-loop control; calculate the rail pressure control deviation as the PID input, and the output of the controller determines the output flow of the high-pressure oil pump, which is similar to the high-pressure oil pump properties are linked. The high-pressure oil pump mainly uses PWM control to control the opening (current) of the oil metering unit. Its parameters are the control period and duty cycle. The demanded oil supply flow of the common rail pipe can be directly converted into the drive current of the oil metering unit. Therefore, when the engine speed is greater than a certain value, the flow rate of the pump is directly determined by the opening (current) of the flow metering unit, and the control duty cycle of the solenoid valve can be calculated according to the required current, which is known/well known.

At present, the more advanced rail pressure control method is to combine the rail pressure pre-control and feedback control. The pre-control is to calculate the current reference according to the engine speed, cycle fuel injection volume and target rail pressure. Its main function is to reduce the rail pressure controller. delay time and keep the controller deviation small. Its essence is open-loop control. At the same time, the PID controller fine-tunes the rail pressure on this basis, so that the rail pressure control module can achieve good target rail pressure following characteristics, which is also known/well known (refer to patent literature: application number 201010601766.7)

However, considering that the actual resistance of the control valve of the oil metering unit will change with the internal temperature, the winding method and assembly process of the control valve coil, as well as the fluctuation of the power supply state during operation, will cause the actual control valve duty ratio ( The target current) and the control valve opening current (actual current) produce a large deviation, which makes the pre-control of the rail pressure controller produce a large setting deviation. Therefore, more fine control should also be added to the feedback control of the fuel metering unit control valve current to ensure that the control current ideally follows the target setting current.

In the prior art, in order to achieve high-precision control of the energizing current of the electromagnetic proportional control valve, a current closed-loop control is introduced, and integral processing is added to the energizing control. There are two ways to set the initial value of the integral term. One method is calculated by using the control valve resistance value, and the other method is obtained by using the integral gain method of the difference between the target current and the actual current (refer to patent document: application number 200880120382.4), and the latter method is an optimization of the former method. The current closed-loop control mode based on the software method is always difficult to follow the target current quickly and accurately.

Because the temperature of the control valve environment changes greatly, the ambient temperature of the control valve varies greatly from the start-up process to the high-load work process, the actual control valve resistance always deviates from the set standard resistance, and the deviation value is always fluctuating, which will inevitably affect different The performance of the rail pressure controller in the working environment. At the same time, the software closed-loop control method has a long response cycle due to the limitation of processor interrupt delay and computing power, and the response of current following control is also slow, so that the rail voltage pre-control cannot achieve the best effect.

Contents of the invention

The technical problem to be solved by the present invention is to provide a rail pressure pre-control based on hardware constant current control for the purpose of improving rail pressure regulation performance, realizing rail pressure fast tracking, reducing software algorithm complexity as much as possible, and saving processor hardware resources. Control system and control method.

The technical solution adopted in the present invention is: a rail pressure pre-control system and control method based on hardware constant current control. The rail pressure pre-control system based on hardware constant current control is a rail pressure pre-control system used to drive the high-pressure oil pump-oil quantity metering unit through the constant current drive unit and the PWM drive unit respectively, including:

ECU internal timing interrupt module: under the action of ECU internal timing unit, trigger timing interrupt to generate synchronous constant current control value and PWM drive pulse;

Baseline current query module: calculate the base current of the oil quantity metering unit in this working condition through the average engine speed, cycle injection oil quantity and target rail pressure;

Current distribution module: divide the reference current calculated by the reference current query module into current adjustment value and current setting value, and send the current adjustment value to the constant current drive unit, and send the current adjustment value and current setting value to the PWM drive pulse Wide calculation module, the distribution ratio of the reference current is in the range of 5%-95%;

Constant current drive pulse width capture calculation module: triggered by the constant current drive pulse of the constant current drive unit, used to capture the constant current drive pulse, calculate the pulse width of the constant current drive pulse, and send the calculation result to the PWM drive pulse width calculation module;

PWM drive pulse width calculation module: Calculate the drive pulse of the PWM drive unit according to the current adjustment value and current set value sent by the current distribution module and the captured constant current drive pulse pulse width sent by the constant current drive pulse width capture calculation module Wide, and convert the calculation result into a timing count value, and send it to the PWM drive unit.

The calculation formula of the described PWM driving pulse width calculation module is: d=b×c/a, wherein:

a is the current adjustment value, b is the current setting value, c is the pulse width of the constant current drive pulse, and d is the drive pulse width of the PWM drive unit.

The control method of the rail pressure pre-control system based on hardware constant current control is to execute the ECU internal timing interrupt generated by the timer in the ECU and the external one generated by the constant current drive pulse trigger edge during the operation of the ECU control main program. interruption;

Described internal interrupt comprises the steps:

1) Query the reference current of rail pressure pre-control, calculate the reference current of the fuel quantity metering unit in this working condition through the average engine speed, cycle injection oil quantity and target rail pressure;

2) Calculating the ratio of the reference current, dividing the reference current calculated in step 1 into a current adjustment value and a current setting value, and sending the current adjustment value to the constant current drive unit;

3) The constant current control current value setting is triggered by the constant current drive pulse of the constant current drive unit to capture the constant current drive pulse;

4) Save the reference current ratio value, save the current adjustment value and current setting value obtained in step 2, and the constant current drive pulse captured in step 3;

5) The interrupt response of the internal timing interrupt service program is completed and returns to the main program

Described external interruption comprises the steps:

1) Calculating the pulse width of the constant current driving pulse is to calculate the pulse width of the constant current driving pulse according to the constant current driving pulse captured by the internal interrupt program;

2) PWM drive pulse width calculation, PWM drive pulse width count value conversion, and trigger drive signal are based on the current adjustment value and current setting value obtained by the internal interrupt program, as well as the constant current drive pulse width obtained in step 1, The driving pulse width of the PWM driving unit is calculated, and the calculation result is converted into a timing count value, and sent to the PWM driving unit (5).

3) The interrupt response of the external timing interrupt service program is completed, and returns to the main program.

The drive pulse width of the calculation PWM drive unit (5) described in external interrupt program and step 2 is to adopt the following formula to calculate:

d=b×c/a,

Among them: a is the current adjustment value, b is the current setting value, c is the pulse width of the constant current driving pulse, and d is the driving pulse width of the PWM driving unit.

The rail pressure pre-control system and control method based on hardware constant current control of the present invention have the characteristics of fast response time and good followability; it is completely not affected by the temperature change of the coil resistance of the oil metering unit, and has precise control and fast response Fast; at the same time, it reduces the difficulty and complexity of software control, and saves the hardware resources of the processor.

Description of drawings

Fig. 1 is a schematic diagram of the overall constituent modules of the present invention;

Fig. 2 is a synchronous drive signal timing diagram of the present invention;

Fig. 3 is the internal timing interrupt flowchart of the present invention;

Fig. 4 is a flowchart of the external interrupt of the present invention.

in:

1: Reference current query module 2: Current distribution module

3: Constant current drive unit 4: High pressure oil pump and oil quantity metering unit

5: PWM drive unit 6: External interrupt

7: PWM drive pulse width calculation module 8: Constant current drive pulse width capture calculation module

9: ECU rail pressure pre-control module 10: ECU internal timing interrupt

a: Average engine speed b: Cycle injection oil quantity

c: target rail pressure d: constant current drive pulse

e: cycle synchronization f: drive synchronization

g: PWM drive pulse m: Rising edge

n: falling edge h: pulse width capture calculation

Detailed ways

The rail pressure pre-control system and control method based on hardware constant current control of the present invention will be described in detail below with reference to the embodiments and the accompanying drawings.

As shown in Figure 1, the rail pressure pre-control system based on hardware constant current control of the present invention is a rail pressure pre-control system for driving the high-pressure oil pump and the oil metering unit 4 through the constant current drive unit 3 and the PWM drive unit 5 respectively. The system mainly realizes the closed-loop control of the target reference current, so that the rail voltage control responds quickly and follows the target rail voltage, and is mainly used to generate synchronous constant current control values and PWM drive pulses. Including:

ECU internal timing interrupt 10: When the ECU control main program is executed, it is generated by the timer in the ECU, which is used to set the sending cycle of the constant current drive adjustment value, that is, under the action of the internal timing unit of the ECU, the timing interrupt is triggered to generate Synchronous constant current control value and PWM drive pulse;

External interrupt 6: generated by the trigger edge of the constant current drive pulse, used to synchronize the constant current drive pulse and PWM drive pulse;

Reference current query module 1: Calculate the reference current of the oil quantity metering unit in this working condition through the average engine speed a, the circulating injection oil quantity b and the target rail pressure c;

Current distribution module 2: Divide the reference current calculated by the reference current query module 1 into current adjustment value and current setting value, and send the current adjustment value to the constant current drive unit 3 through the communication mechanism, and assign the current adjustment value and current setting value through variable assignment The current setting value is sent to the PWM drive pulse width calculation module 7, and the distribution ratio of the reference current can be freely set according to actual needs, and can be within the range of 5%-95%;

Constant current drive pulse width capture calculation module 8: The constant current drive pulse width capture calculation module 8 is triggered by the constant current drive pulse of the constant current drive unit 3 through hardware connection input. The trigger edge (falling edge) of the constant current drive pulse is mainly used to generate the synchronization mechanism of the constant current drive pulse and the PWM drive pulse, so that the PWM drive pulse is always synchronized with the constant current drive pulse cycle and drive synchronization (as shown in Figure 2 ). The constant current drive pulse width capture calculation module 8 captures the constant current drive pulse and calculates the constant current drive pulse width. The calculation is to capture and accumulate the high level of the constant current drive pulse through the ECU internal timing unit, and capture and accumulate the count Value × clock frequency of the timing unit, i.e. the pulse width of the constant current drive pulse, and the calculation result is sent to the PWM drive pulse width calculation module 7;

PWM drive pulse width calculation module 7: Calculate the PWM drive unit according to the current adjustment value and current set value sent by the current distribution module 2 and the captured constant current drive pulse pulse width sent by the constant current drive pulse width capture calculation module 8 The driving pulse width of 5, and the calculation result is converted into a timing count value, specifically according to the timer frequency, that is, the driving pulse width of the PWM driving unit 5/timer frequency, and sent to the PWM driving unit 5.

The calculation formula of the described PWM driving pulse width calculation module 7 is: d=b×c/a, wherein:

a is the current adjustment value, b is the current setting value, c is the pulse width of the constant current drive pulse, and d is the drive pulse width of the PWM drive unit.

Since the constant current drive unit 3 is a current closed-loop control based on hardware, its control precision is high and its response is fast. Calculation 8 captures the calculated parameters with good real-time performance. At the same time, the constant current drive unit 3 and the PWM drive unit 5 drive the solenoid valve of the oil metering unit in parallel, and the hardware environment where the two are located is consistent (including power supply, solenoid valve of the oil metering unit, drive circuit, etc.). Therefore, the same cycle and the same driving pulse width can ensure that the current flowing through the solenoid valve of the oil metering unit is the same, and the ratio of the constant current driving pulse width to the PWM driving pulse width in the same cycle is the ratio of the current distribution between the two.

The control method of the present invention using the rail pressure pre-control system based on hardware constant current control is to sequentially execute the transmission of the constant current drive adjustment value generated by the timer in the ECU during the operation of the ECU control main program. Periodic ECU internal timing interrupt 10 and external interrupt 6 for synchronous constant current drive pulse and PWM drive pulse generated by the trigger edge of the constant current drive pulse;

As shown in Figure 3, the internal timing interrupt service routine includes the following steps after the interrupt response:

1) Query the reference current of rail pressure pre-control, calculate the reference current of the fuel quantity metering unit in this working condition through the average engine speed, cycle injection oil quantity and target rail pressure;

2) Calculating the ratio of the reference current, dividing the reference current calculated in step 1 into a current adjustment value and a current setting value, and sending the current adjustment value to the constant current drive unit 3;

3) The constant current control current value setting is triggered by the constant current drive pulse of the constant current drive unit 3 to capture the constant current drive pulse;

4) Save the reference current ratio value, save the current adjustment value and current setting value obtained in step 2, and the constant current drive pulse captured in step 3;

5) The interrupt response of the internal timing interrupt service program is completed, and returns to the main program.

As shown in Figure 4, the external interrupt service routine includes the following steps after the interrupt response (triggered by the falling edge of the constant current drive pulse):

1) Calculating the pulse width of the constant current driving pulse is to calculate the pulse width of the constant current driving pulse according to the constant current driving pulse captured by the internal interrupt program;

2) PWM drive pulse width calculation, conversion of PWM drive pulse width count value, and trigger drive signal are based on the current adjustment value and current setting value obtained by the internal interrupt program, as well as the constant current drive pulse width obtained in step 1, Calculate the driving pulse width of the PWM driving unit 5, and convert the calculation result into a timing count value (according to the timer frequency, i.e. the driving pulse width/timer frequency of the PWM driving unit (5)), and send to the PWM driving unit 5 .

The drive pulse width of the calculation PWM drive unit 5 described in the external interrupt program and step 2 is to adopt the following formula to calculate:

d=b×c/a，       (1)

Among them: a is the current adjustment value, b is the current setting value, c is the pulse width of the constant current drive pulse, and d is the drive pulse width of the PWM drive unit;

3) The interrupt response of the external timing interrupt service program is completed, and returns to the main program.

As shown in Figure 2, the pulse width of the constant current drive pulse is the high-level time period of each pulse of the constant current drive accumulated by the specific timer of the ECU; the falling edge n of the constant current drive pulse d is used to ensure that the PWM drive pulse g is synchronous with the constant current drive pulse d period. After the falling edge n arrives, the set PWM drive pulse g starts to work, and the freewheeling flow ensures that the reference current of the solenoid valve of the oil metering unit reaches the pre-control target.

Here, it is set that the part sent to the constant current drive unit 3 is 3/4 pre-control current value, and the part allocated to PWM duty ratio calculation 7 is 1/4 pre-control current value.

The timer in the ECU generates periodic interrupt triggers, and the internal timer interrupt service program interrupts the response and enters the corresponding interrupt service program.

The rail pressure pre-control system and control method based on hardware constant current control of the present invention have the characteristics of fast response time and good followability; it is completely not affected by the temperature change of the coil resistance of the oil metering unit, and has precise control and fast response Fast; at the same time, it reduces the difficulty and complexity of software control, and saves the hardware resources of the processor.

As shown in Fig. 1, Fig. 3 and Fig. 4, the working process of the rail pressure pre-control system and control method based on hardware constant current control of the present invention is: the reference current query module 1 starts to check the engine average speed, cycle injection oil quantity and the target rail pressure to calculate the reference current of the oil quantity metering unit in this working condition, and then obtain the current adjustment value of the constant current drive unit 3 and the current setting value of the PWM drive unit 5 through the current distribution module 2, and then the current distribution module 2 passes through The communication mechanism sends the adjustment value to the constant current drive unit 3 , and saves the current adjustment value and the current setting value through variable assignment and sends them to the PWM driving pulse width calculation module 7 .

The internal timing interrupt service routine interrupt response ends and returns to the main program.

In order to realize the set target current, the constant current drive unit 3 starts its hardware closed-loop control mechanism to generate a constant current drive pulse. The falling edge of the constant current drive pulse triggers an external interrupt and enters the external interrupt service program.

First, the program calls out a specific timer to capture the high-level count value of the constant current drive pulse, and calculates the pulse width of the constant current drive pulse through the system clock frequency.

Then, calculate the PWM driving pulse width by formula 1, and set the PWM driving signal. Its high level is the calculated PWM driving pulse width, and the driving signal remains low after the high level, until the next interrupt service response, the PWM driving pulse is refreshed, and a new round of driving setting is started.

The external timing interrupt service program interrupt response ends and returns to the main program.

As shown in FIG. 1 , the constant current drive unit 3 and the PWM drive unit 5 work together on the high-pressure oil pump-oil quantity metering unit 4 .

As shown in Fig. 3, the reference current of 3/4 is realized and responded through the constant current drive unit 3, and a constant current drive pulse is output at the same time. By capturing and calculating the constant current drive pulse width, calculate the PWM drive pulse width required by the PWM drive unit 5 to realize 1/4 of the reference current, and simultaneously convert the PWM drive pulse width into the PWM drive pulse width count value (based on the timer clock frequency) to send the PWM drive unit 5. Under the synchronous trigger of the falling edge of the constant current drive pulse, the freewheeling effect of the PWM drive pulse width (as shown in the signal sequence in Figure 2) finally realizes the pre-control of the reference current.

Claims (4)

1. the rail pressure based on hardware constant current control is controlled system in advance, it is characterized in that, is for controlling system in advance by the rail pressure of constant current driving unit (3) and PWM driver element (5) driving high pressure oil pump-fuel gauging unit (4) respectively, comprising:

ECU internal timing interrupt module (10): under the unit effect of ECU internal timing, trigger regularly and interrupt, in order to produce synchronous constant current controlling value and PWM driving pulse;

Reference current enquiry module (1): the reference current that comes design condition fuel gauging unit by motor mean speed, cyclic spray oil mass and target rail pressure;

Electric current distribution module (2): the reference current that reference current enquiry module (1) is calculated is divided into electric current regulated value and current setting value, and the electric current regulated value sent to constant current driving unit (3), electric current regulated value and current setting value are sent to PWM driving pulsewidth computing module (7), and the allocation proportion of reference current is in the 5%-95% interval;

Constant current drives pulsewidth and catches computing module (8): the constant current driving pulse by constant current driving unit (3) triggers, be used for catching the constant current driving pulse, and calculate this constant current driving pulse pulsewidth, simultaneously result of calculation is sent to PWM and drive pulsewidth computing module (7);

PWM drives pulsewidth computing module (7): the electric current regulated value of sending according to electric current distribution module (2) and current setting value and constant current drive the driving pulsewidth that constant current driving pulse pulsewidth that pulsewidth catches the seizure that computing module (8) sends calculates PWM driver element (5), and result of calculation is converted into timing ga(u)ge numerical value, and send to PWM driver element (5).

2. the rail pressure based on hardware constant current control according to claim 1 is controlled system in advance, it is characterized in that the formula that described PWM drives pulsewidth computing module (7) is: d=b * c/a, wherein:

A is the electric current regulated value, and b is current setting value, and c is constant current driving pulse pulsewidth, and d is the driving pulsewidth of PWM driver element.

3. controlling method that adopts the described rail pressure based on hardware constant current control of claim 1 to control system in advance, it is characterized in that, be in ECU control main program running, carry out by the ECU internal timing interruption (10) of the generation of the timer among the ECU with by the constant current driving pulse and trigger along the external interrupt (6) that produces;

Described internal interrupt comprises the steps:

1) rail pressure is controlled the reference current inquiry in advance, comes the reference current of design condition fuel gauging unit by motor mean speed, cyclic spray oil mass and target rail pressure;

2) the reference current proportioning is calculated, and the reference current that step 1 is calculated is divided into electric current regulated value and current setting value, and the electric current regulated value is sent to constant current driving unit (3);

3) constant current control current value is set, and the constant current driving pulse triggering by constant current driving unit (3) catches the constant current driving pulse;

4) reference current proportioning value is preserved, and preserves electric current regulated value and current setting value that step 2 obtains, and the constant current driving pulse that captures of step 3;

5) internal timing interrupt service routine interrupt response finishes, and returns main program

Described external interrupt comprises the steps:

1) calculating constant current driving pulse pulsewidth, is the constant current driving pulse that captures according to the internal interrupt program, calculates this constant current driving pulse pulsewidth;

2) PWM drives pulsewidth calculating, PWM drives the conversion of pulsewidth count value, trigger and drive signal, be according to the resulting electric current regulated value of internal interrupt program and current setting value, and the resulting constant current driving pulse of step 1 pulsewidth, calculate the driving pulsewidth of PWM driver element (5), and result of calculation is converted into timing ga(u)ge numerical value, and send to PWM driver element (5)

3) external definition interrupt service routine interrupt response finishes, and returns main program.

4. employing according to claim 3 is controlled the controlling method of system in advance based on the rail pressure of hardware constant current control, it is characterized in that the driving pulsewidth of external interrupt program and step 2 described calculating PWM driver element (5) is to adopt following formula to calculate:

d=b×c/a，

Wherein: a is the electric current regulated value, and b is current setting value, and c is constant current driving pulse pulsewidth, and d is the driving pulsewidth of PWM driver element.

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