CN104029671A - Method for controlling shutdown position of automobile engine - Google Patents

Abstract

The invention discloses a method for controlling the shutdown position of an automobile engine. The method comprises the following steps that whether the current rotating speed omega of the engine is lower than the minimum ignition rotating speed omega Max of the engine or not is judged; if the current rotating speed of the engine is lower than the minimum ignition rotating speed, that is, omega<omega Max, whether the rotating speed of the engine is 0 or not continues to be judged; if the rotating speed of the engine is 0, the engine shutdown position control procedure is executed. Compared with the prior art, the method has the advantages that due to the fact that an ISG motor and the engine are coaxial, and the ISG motor has high position precision, when the engine is shut down, the engine is driven and controlled by the ISG motor to be shut down at the position with the minimum resisting moment, and the high success rate of starting the engine by an ISG system can be guaranteed.

Description

Automotive engine stop position control method

Technical field

The present invention relates to hybrid electric vehicle engine stop position control field, refer to particularly a kind of automotive engine stop position control method.

Background technology

The severe situation of global energy and environment, the particularly international financial crisis enormous impact to automobile industry; promote countries in the world and accelerate transportation and energy's strategic transformation, the new-energy automobile that hybrid vehicle, pure electric automobile and fuel cell powered vehicle be representative of take becomes the important directions of future automobile development.

Because electronlmobil is in the current difficulties such as continual mileage is short, battery price, Infrastructure imperfection that are but faced with, need the effort of quite a while just may progressively to solve; And hybrid vehicle possesses better Industrialized conditions in present stage, hybrid vehicle is of great significance to China's development of automobile industry.This just means that new-energy automobile dynamic assembly consists of driving engine and the motor driver of lower-wattage within one quite long period.

Restriction due to cost and weight, size, service conditions, makes the restriction of ISG system dynamic capacity of cell, causes its output characteristic softer, causes the low speed torque of ISG system limited, makes the success ratio of ISG system fire an engine limited; Add that electrokinetic cell is when low temperature and high temperature, the horsepower output of its horsepower output during than normal temperature is low, causes the success ratio of ISG system fire an engine when low temperature lower.

In working cycle of driving engine, the resisting moment of driving engine is along with engine crankshaft position is different and different, a certain four cylinders are in a working cycle, and the engine drag curve that driving engine changes with crank position is (fulcrum on 0 ° of corresponding engine cylinder) as shown in Figure 1.Driving engine can be parked near the position of resisting moment maximum conventionally; be on engine cylinder near fulcrum; these point; power drive system need to be exported larger moment of torsion just can overcome engine resistance torque; drag engine starting, because the power-handling capability of power drive system is certain, make near fulcrum, to start success ratio limited on engine cylinder; during low temperature, the success ratio of fire an engine is lower.

Evidence: at engine crankshaft diverse location, because the resisting moment of driving engine is different, make under identical power drive system, starting success ratio is different, is in the position that engine resistance torque is less, engine starting success ratio is also higher, be near near bent axle while being in engine cylinder lower fulcrum (90 ° of multiple positions, being no more than 5 degree in Fig. 1), starting success ratio is the highest, during normal temperature, approach 100%.

Retrieve existing patent, the method of control engine stop position (CN101180897A) in hybrid electric vehicle, the method will comprise a) when described driving engine will be shut down, in the situation of the fuel cut-off providing to described driving engine, with described motor, according to the first engine speed reduction rate, reduce engine speed; B) at engine speed, be decreased to after the first engine speed, use described motor according to the second engine speed reduction rate, and monitor current crank position, the number of times conforming to given target engine stop position to calculate described current crank position by processing the signal of crankshaft sensor and cam sensor; And c), if described number of times is greater than predetermined number, and if practical engine speeds is equal to or less than the second reference rotation velocity, when described current crank position conforms to described target engine stop position, use described motor to stop described driving engine so.

This invention, by entire car controller (HCU), by CAN, gather the brake torque that engine speed and crank position calculate ISG power drive system, by CAN, brake torque is issued to electric machine controller, by electric machine controller, by given brake torque, driving engine is stopped to assigned address.Due to the restriction of CAN communication speed, so the method in document has larger control time delay, and engine stop position belongs to angle position and controls, the realtime control of having relatively high expectations, the poor effect in working control of the method in document.

Summary of the invention

Object of the present invention will provide a kind of automotive engine stop position control method exactly.

For achieving the above object, automotive engine stop position control method provided by the present invention, comprises the following steps:

Step 1) by electric machine controller, judge that present engine rotational speed omega is whether lower than the minimum ignition rotational speed omega of driving engine _max;

Step 2) if present engine rotating speed lower than minimum ignition rotating speed, i.e. ω < ω _max, continue to judge whether engine speed is 0;

Step 3) if engine speed is 0, enter engine stop position control flow;

Compared with prior art; the invention has the advantages that: because ISG motor and driving engine are coaxial; and ISG motor has higher positional precision; when engine shutdown; by ISG drive and control of electric machine driving engine, stop the position (90 ° of odd-multiple positions in Fig. 1) to resisting moment minimum, and can guarantee higher ISG system fire an engine success ratio.

Have following different from the method > > (claiming afterwards: retrieval is invented) of control engine stop position in patent of invention < < hybrid electric vehicle:

1, for object different:

(1) retrieval invention: controlling stop position, is for when the engine starting, reduces the torque ripple and the vibration that produce in air inlet, compression and expansion stroke procedure.

(2) the present invention: be by ISG power drive system, driving engine to be parked in to the position of engine resistance torque minimum, when next fire an engine, with minimum electric flux, the shortest cranking time, drags to fire speed fast by driving engine; Thereby (comprising low temperature) starting success ratio that improves the various operating modes of driving engine, shortens cranking time.

2, the target of controlling is different:

(1) retrieval invention: each shutdown is controlled and all driving engine stopped to identical point.

(2) the present invention: for multi-cylinder engine, in driving engine one circle, engine resistance torque minimum bit is equipped with multiple spot, and each shutdown is parked in the point of engine resistance torque minimum nearby;

3, control thinking difference:

(1) retrieval invention: when engine speed < the first rotating speed, engine speed reduces with fixed slope, and floor time is longer; By crank position, conform to number of times and engine speed with target stop position as the Rule of judgment stopping to target location, due to engine inertia, there is deviation in stop position and target location.

(2) the present invention: when engine speed < the first rotating speed; poor with target stop position and driving engine current location in real time; as ISG electric system brake torque control inputs amount; closed loop control engine speed reduction rate; can driving engine be stopped to target location with the shortest time; actual stop position can overlap completely with target stop position in theory, accomplishes floating.

4, mode is different

(1) retrieval invention: gather by CAN the brake torque that engine speed and crank position calculate ISG power drive system by entire car controller (HCU), by CAN, brake torque is issued to electric machine controller, by electric machine controller, by given brake torque, driving engine is stopped to assigned address.Due to the restriction of CAN communication speed, so the method in document has larger control time delay, and engine stop position belongs to angle position and controls, the realtime control of having relatively high expectations, the poor effect in working control of the method in document.

(2) the present invention: coaxial and ISG motor driven systems has the feature of higher position precision and torque precision according to ISG motor and driving engine, by electric machine controller directly according to current motor speed, angle and the engine indicated torque that prestores, by angle position closed loop control algorithm, driving engine is stopped to target location.There is higher real-time and control accuracy.Control algorithm is clear, has higher feasibility.

Accompanying drawing explanation

Fig. 1 is engine drag curve.

Fig. 2 is the engine stop position angle control principle block diagram based on ISG system.

Fig. 3 is the engine stop position angle control system block diagram based on ISG system

Fig. 4 is that the engine stop position based on ISG system is controlled decision flowchart.

Fig. 5 is the engine stop position control flow chart based on ISG system.

Fig. 6 is engine stop position angle control flow chart.

The specific embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail.

The present invention is in electric machine controller master cpu, and the driving engine that prestores is with angle and the mapping table of resisting moment and the point (corresponding angle) of a Machine cycle intrinsic motivation resisting moment minimum.

When driving engine, naturally shut down after (being that rotating speed is zero), by the inquiry of driving engine rotation direction, from the nearest controlling point of engine resistance torque minimum position, be decided to be target stop position, by controlling ISG motor, driving engine is stopped to assigned address subsequently.The control principle block diagram of the hybrid electric vehicle engine stop position control setup based on ISG system and control system block diagram are respectively as shown in Figures 2 and 3.

The method control method is simple, is easy to realize in ISG control system; Can in a cycle of engine, driving engine be stopped to target stop position, angle control precision is high.

Below in conjunction with control flow chart, the present invention is described in further detail.

Realize engine stop position and control, first will judge whether driving engine shuts down, and only has after engine shutdown, the engine stop position based on ISG system is controlled and could be started to carry out, and concrete engine stop position is controlled determination flow as shown in Figure 4.

Step 1) by electric machine controller, judge that present engine rotational speed omega is whether lower than the minimum ignition rotational speed omega of driving engine _max;

Step 2) if present engine rotating speed lower than minimum ignition rotating speed, i.e. ω < ω _max, continue to judge whether engine speed is 0;

Step 3) if engine speed is 0, enter engine stop position control flow;

As shown in Figure 5, it comprises the following steps engine stop position control flow:

Step 1) according to the rotation direction of present engine, determine the target stop position θ * of driving engine;

Step 2) according to determined target stop position, calculate the maximum speed of revolution ω in stop position control process _max, concrete computation process is as shown in formula (7);

Step 3) driving engine is accelerated to flag set, i.e. F=1;

Step 4) ISG system is exported maximum power torque Te _max;

Step 5) judge whether engine speed reaches the maximum speed of revolution that stop position is controlled, i.e. ω>=ω _max; If do not reach the maximum speed of revolution that stop position is controlled, i.e. ω < ω _max, continue step 4, export maximum power torque Te _max; If ω>=ω _max, enter step 6;

Step 6) driving engine accelerates sign zero clearing, i.e. F=0;

Step 7) entering engine stop position angle controls;

As shown in Figure 6, it comprises the following steps engine stop position angle control flow:

Step 1) judge whether engine speed is not 0; If engine speed is 0, control flow finishes, and returns; If engine speed is not 0, enter step 2;

Step 2) according to working as the residing position θ of front motor and target stop position θ ^*, calculate differential seat angle Δ θ;

Step 3) judge whether driving engine is parked in target stop position, whether Δ θ is 0; If Δ θ=0, control flow finishes, and returns; If Δ θ ≠ 0, enters step 4;

Step 4), according to the current rotational speed omega of driving engine and differential seat angle Δ θ, calculate brake torque Te, and export brake torque.

Maximum speed of revolution ω in the stop position control process of mentioning in the step 2 of above-mentioned engine stop position control flow _maxmethod of calculating be:

In electric machine controller master cpu, the driving engine that prestores is with angle and the mapping table of resisting moment and the point (corresponding angle) of a Machine cycle intrinsic motivation resisting moment minimum.

During ISG system output maximum torque, the minimum angular acceleration of power system is as shown in formula (5).

${\mathrm{\&beta;}}_1=\frac{{\mathrm{Te}}_{\max }-M_{\max }}{J}---\left(5\right)$

Wherein: β ₁---the minimum angular acceleration (rad/s of power system ²)

Te _max---ISG system output maximum torque (Nm)

M _max---driving engine maximum resistance square (Nm)

J---driving engine and ISG motor synthesize rotor inertia (kgm ²)

Under minimum acceleration, driving engine is stopped to required time of assigned address as shown in formula (6), in position adjustments control process, corresponding engine peak speed is ω _max.

$t=\sqrt{\frac{J\&CenterDot;\mathrm{\&Delta;\&theta;}}{{\mathrm{Te}}_{\max }-M_{\max }}}---\left(6\right)$

Wherein: t---driving engine was stopped to the required time of assigned address (s)

The differential seat angle (rad) of Δ θ---current stop position and target stop position

J---driving engine and ISG motor synthesize rotor inertia (kgm ²)

Te _max---ISG system output maximum torque (Nm)

M _max---driving engine maximum resistance square (Nm)

${\mathrm{\&omega;}}_{\max }=\sqrt{\frac{({\mathrm{Te}}_{\max }-M_{\max })\&CenterDot;\mathrm{\&Delta;\&theta;}}{J}}---\left(7\right)$

Wherein: ω _max---shut down the maximum motor speed (rad/s) in control process

The differential seat angle (rad) of Δ θ---current stop position and target stop position

J---driving engine and ISG motor synthesize rotor inertia (kgm ²)

Te _max---ISG system output maximum torque (Nm)

M _max---driving engine maximum resistance square (Nm)

The method of calculating of the brake torque Te of the needs output of mentioning in the step 4 of above-mentioned engine stop position angle control flow is:

Due to, upper limit revolution ratio when stop position is controlled is lower, ignores movement resistor moment.

According to kinematics relative theory:

Te(t)-M(θ)＝J·β (1)

Wherein: Te (t)---the current electromagnetic torque of ISG motor (Nm)

M (θ)---engine system resisting moment (Nm)

θ---ISG locus angle/crank position angle (rad)

J---driving engine and ISG motor synthesize rotor inertia (kgm ²)

β---angular acceleration (rad/s ²)

ω(t)＝ω ₀+β·t (2)

Wherein: ω (t)---current time power system cireular frequency (rad/s)

ω ₀---stop position is controlled power system initial angle speed (rad/s)

β---angular acceleration (rad/s ²)

T---shut down and control elapsed-time standards (s)

dθ＝ω(t)dt (3)

Wherein: d θ---angle variable quantity (rad)

ω (t)---current time power system cireular frequency (rad/s)

Dt---time variation amount

Stop position is controlled angular velocity omega=0 of finishing rear power system, and the angle variable quantity of establishing from current location to stop position is Δ θ (t), associating (1), (2), (3) formula, solve:

$\mathrm{Te}\left(t\right)=M\left(\mathrm{\&theta;}\right)-\frac{J\&CenterDot;{{\mathrm{\&omega;}}_0}^2}{2\mathrm{\&Delta;\&theta;}\left(t\right)}---\left(4\right)$

Wherein: Te (t)---the current electromagnetic torque of ISG motor (Nm)

M (θ)---engine system resisting moment (Nm)

θ---ISG locus angle/crank position angle (rad)

J---driving engine and ISG motor synthesize rotor inertia (kgm ²)

ω ₀---stop position is controlled power system initial angle speed (rad/s)

Δ θ (t)---the angle variable quantity (rad) from current location to stop position

What above-mentioned side adopted is that angle closed loop is followed the tracks of control, and angle control precision is high, after adopting engine stop position to control, can improve the success ratio of ISG system fire an engine, shortens the time of fire an engine.

Above-described embodiment is preferably embodiment of the present invention; but embodiments of the present invention are not restricted to the described embodiments; other any do not deviate from change, the modification done under Spirit Essence of the present invention and principle, substitutes, combination, simplify; all should be equivalent substitute mode, within being included in protection scope of the present invention.

Claims (3)

1. an automotive engine stop position control method, is characterized in that comprising the following steps:

Step 1) by electric machine controller, judge that present engine rotational speed omega is whether lower than the minimum ignition rotational speed omega of driving engine _max;

Step 2) if present engine rotating speed lower than minimum ignition rotating speed, i.e. ω < ω _max, continue to judge whether engine speed is 0;

Step 3) if engine speed is 0, enter engine stop position control flow.

2. automotive engine stop position control method according to claim 1, is characterized in that, the engine stop position control flow in described step 3 comprises the following steps:

Step 1) according to the rotation direction of present engine, determine the target stop position θ * of driving engine;

Step 2) according to determined target stop position, calculate the maximum speed of revolution ω in stop position control process _max, concrete computation process is as shown in formula (7);

Step 3) driving engine is accelerated to flag set, i.e. F=1;

Step 4) ISG system is exported maximum power torque Te _max;

Step 5) judge whether engine speed reaches the maximum speed of revolution that stop position is controlled, i.e. ω>=ω _max; If do not reach the maximum speed of revolution that stop position is controlled, i.e. ω < ω _max, continue step 4, export maximum power torque Te _max; If ω>=ω _max, enter step 6;

Step 6) driving engine accelerates sign zero clearing, i.e. F=0;

Step 7) entering engine stop position angle controls.

3. automotive engine stop position control method according to claim 2, is characterized in that, the engine stop position angle control flow of sending out in described step 7 comprises the following steps:

Step 1) judge whether engine speed is not 0; If engine speed is 0, control flow finishes, and returns; If engine speed is not 0, enter step 2;

Step 2) according to working as the residing position θ of front motor and target stop position θ ^*, calculate differential seat angle Δ θ;

Step 3) judge whether driving engine is parked in target stop position, whether Δ θ is 0; If Δ θ=0, control flow finishes, and returns; If Δ θ ≠ 0, enters step 4;

Step 4), according to the current rotational speed omega of driving engine and differential seat angle Δ θ, calculate brake torque Te, and export brake torque.