CN109795470B - Active vibration reduction method of power system based on engine instantaneous torque observer - Google Patents

Abstract

The invention provides an active vibration reduction method for a power system based on an engine instantaneous torque observer, which belongs to the field of electronic control of an engine, a motor or a hybrid power system. The method makes the engine run according to the set working conditions; in each working condition, the vehicle control unit collects the engine state parameters and control parameters to add sensor signals; the engine instantaneous torque observer is estimated based on the above parameters and signals and the crankshaft signal. The instantaneous torque fluctuation signal of the engine is sent to the motor controller; the motor controller calculates the target harmonic torque and generates a control signal to send to the motor; the motor generates the corresponding harmonic torque according to the received control signal; the instantaneous torque of the engine and The harmonic torque generated by the motor acts on the transmission shaft at the same time to realize the vibration reduction of the power system. The invention does not need to install additional hardware on the power system, and adds high-frequency harmonic torque on the motor to suppress the vibration of the transmission system and improve the driving comfort of the vehicle.

Description

An Active Vibration Reduction Method for Power System Based on Engine Instantaneous Torque Observer

technical field

The invention belongs to the field of electronic control of an engine, a motor or a hybrid power system, and particularly proposes an active vibration reduction method for a power system based on an engine instantaneous torque observer.

Background technique

The starting process of the engine is a key factor affecting the comfort of the driving process. Especially in the hybrid system, the high fuel consumption condition of the engine (usually low speed, light load) and idle speed are canceled, and the electric motor can realize the quick start of the engine. Therefore, during the driving of the hybrid vehicle, the engine is frequently started and stopped. Therefore, reducing the vibration during starting is the key to ensuring the comfort of hybrid vehicles. During the starting process, the vibration of the engine mainly comes from two aspects. First, before the engine ignites (fuel injection for diesel engines and spark plug ignition for gasoline engines), pure compression and inertial force will cause vibration of the shaft system; second, the engine The sudden change of torque caused by ignition can also cause vibration of the shafting. Similarly, in the process of engine load change, the change of the fuel injection amount (diesel engine) or the charge of the combustible mixture (gasoline engine) will cause the gas force of each cylinder of the engine to change, which will lead to the fluctuation of the shafting speed. Comfort is a threat.

The existing power system vibration reduction methods mainly solve the vibration problem in the starting process by designing the optimal starting speed curve. In this method, the dynamic modeling of the engine and the starter motor system is firstly carried out, and the vibration characteristics of the shafting during the engine reverse towing process are studied. Then extract the indicators that can characterize the vibration level, such as the rotation non-uniformity coefficient, and design the optimal starting speed curve of the engine through the optimization algorithm, so that the vibration index can be optimized. Finally, through the closed-loop control of the optimal starting speed, let the motor reversely drag the engine to start along the optimal starting speed curve to verify the effectiveness of the algorithm. However, this method requires the establishment of a complex physical model, and the optimization result is only to achieve the optimal vibration index. Not only that, after the engine fires, the motor is usually no longer involved, making it difficult to handle vibrations caused by sudden changes in combustion torque. In conventional engine powertrains, the vibration energy can also be cut by installing flywheels and/or torsional dampers. There are also methods to limit the maximum rate of pressure rise in the cylinder for smooth starts or load changes by changing control parameters in the dynamic process, such as injection timing and exhaust gas recirculation rate. Although the above-mentioned method for solving the vibration during starting and load changing can reduce the vibration to a certain extent and improve the comfort of the driving process, it does not grasp the essential problem that causes the rotational speed fluctuation, that is, the torque fluctuation during the working process of the engine. In the hybrid system, the engine and the motor are mechanically coupled, and the fast response speed of the motor makes it possible to reduce the engine work through the active intervention of the motor, especially the speed fluctuation in the dynamic process.

The control system of the engine adopts a torque-based control system, that is, the torque demand of the engine is obtained by looking up a table according to the driver's accelerator pedal position and the engine speed. Other control parameters are obtained by looking up the table based on the torque demand and speed of the engine. The torque demand is the average torque of the engine, not the fluctuations in the instantaneous torque of the engine. At the same time, the average torque does not solve the high frequency problems of the hybrid system, such as vibration problems.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for active vibration reduction of a power system based on an engine instantaneous torque observer in order to overcome the shortcomings of the prior art. The present invention does not need to install additional hardware on the power system, and estimates the instantaneous torque fluctuation of the engine through the engine instantaneous torque observer. The additional high-frequency harmonic torque suppresses the vibration of the transmission system and improves the comfort of the vehicle driving process.

The present invention provides a method for active vibration reduction of a power system based on an engine instantaneous torque observer, characterized in that the method comprises the following steps:

1) Make the engine run according to the set working conditions under the control of the engine control unit;

2) Under each working condition, the vehicle control unit collects the state parameters, control parameters and additional sensor signals of the engine;

3) The engine instantaneous torque observer receives the engine state parameters, control parameters, additional sensor signals and the crankshaft signal measured by the encoder installed at the crankshaft output end collected in step 2), and estimates the instantaneous torque fluctuation of the engine to obtain the engine Instantaneous torque fluctuation signal and sent to the motor controller;

4) The motor controller calculates the target harmonic torque through the instantaneous torque fluctuation signal of the engine and generates a corresponding control signal to send to the motor;

5) The motor generates the corresponding harmonic torque according to the received control signal;

6) The instantaneous torque of the engine and the harmonic torque generated by the motor act on the transmission shaft at the same time to realize the vibration reduction of the power system.

The characteristics and beneficial effects of the present invention are:

1) The present invention does not need to add additional hardware, and the engine instantaneous torque observer can estimate the instantaneous torque fluctuation of the engine to ensure the accurate response of the motor to the engine torque change.

2) The MCU adds high-frequency harmonic torque to the motor by processing the instantaneous torque fluctuation estimated by the torque observer. The harmonic torque and the instantaneous torque fluctuation of the engine act together on the drive train. Domain to achieve vibration reduction.

3) The present invention realizes the active vibration reduction of the drive train through the estimation of instantaneous torque fluctuation and the high frequency control of the motor, which can be used in more engine application scenarios and has high practical value.

Description of drawings

FIG. 1 is an overall flow chart of the method of the present invention.

FIG. 2 is a schematic diagram of the implementation effect of the method of the present invention in an embodiment of the present invention.

Detailed ways

The present invention proposes an active vibration reduction method for a power system based on an engine instantaneous torque observer, which is further described in detail below with reference to the accompanying drawings and specific embodiments.

The present invention proposes a method for active vibration reduction of a power system based on an engine instantaneous torque observer. The overall process is shown in Figure 1, and the method includes the following steps:

1) Make the engine run according to the set working condition under the control of the ECU (engine control unit) (in the present invention, the set working condition can be any working condition, including starting, stopping, acceleration and deceleration, etc., and the application scenario is not limited ).

2) Under each working condition, the VCU (Vehicle Control Unit) collects data including but not limited to engine state parameters (air intake, cooling parameters), control parameters (fuel injection, exhaust gas recirculation rate parameters) and additional sensor signals ( In this embodiment, the additional sensor is a cylinder pressure sensor installed in each cylinder of the engine, and the cylinder pressure sensor collects the pressure signal in the cylinder; in actual operation, sensor types can be added as needed).

3) The engine instantaneous torque observer programmed in the VCU receives the engine state parameters, control parameters, additional sensor signals and the crankshaft signal measured by the encoder installed at the output end of the crankshaft (the encoder is used to obtain the crankshaft signal) collected in step 2). The position of each electronically controlled engine has an encoder, no additional installation is required), the instantaneous torque fluctuation of the engine is estimated, and the instantaneous torque fluctuation signal of the engine is obtained and sent to the motor controller MCU.

4) The MCU calculates the target harmonic torque that can reduce the vibration of the shaft system through the instantaneous torque fluctuation signal of the engine, and generates a corresponding control signal to send to the motor.

5) The motor generates the corresponding harmonic torque according to the received control signal;

6) The instantaneous torque of the engine and the harmonic torque generated by the motor act on the transmission shaft at the same time. Through the mutual cancellation of the output torque fluctuation of the two power sources, the fluctuation of the engine speed is reduced, the smoothness of the power system is improved, and the realization of Vibration damping of the powertrain.

In the present invention, the engine, motor and ECU can all use conventional components. In order to realize high frequency application, the CAN (Controller Area Network, controller area network) transmission rate of VCU and MCU should be in the order of 1ms.

Described step 3) carries out the estimation of the instantaneous torque fluctuation of the engine, for each cylinder of the engine, the formula that can be used is as follows:

为曲拐转角，β为连杆摆角，λ＝r/l为曲柄连杆比，l为连杆大小头中心距，D为气缸直径，p_g为缸内气体绝对压力，p_b为曲轴箱气体绝对压力，I_crank为曲轴等效转动惯量。连杆摆角

为发动机的摩擦转矩，与曲轴位置和曲轴瞬时转速有关，可由经验公式或者实验手段得到；m_hz为活塞质量，m_lA为连杆小头等效质量，ω为曲轴转速；where r is the crank radius,

is the crank angle, β is the swing angle of the connecting rod, λ=r/l is the crank connecting rod ratio, l is the center distance between the large and small heads of the connecting rod, D is the cylinder diameter, p _g is the absolute pressure of the gas in the cylinder, and p _b is the crankshaft The absolute pressure of the tank gas, I _crank is the equivalent moment of inertia of the crankshaft. connecting rod swing angle

is the friction torque of the engine, which is related to the position of the crankshaft and the instantaneous speed of the crankshaft, and can be obtained by empirical formulas or experimental means; m _hz is the piston mass, m _lA is the equivalent mass of the small end of the connecting rod, and ω is the crankshaft speed;

The target harmonic torque in step 4) can be calculated by the following method, for an n-cylinder engine:

Among them, M t_i represents the estimation of the engine instantaneous torque fluctuation of the _ith cylinder of the engine, and _n is the number of cylinders of the engine. The implementation effect of the method of the present invention is shown in FIG. 2 . In Figure 2, the torque ripple of the engine during a typical starting process is shown. The gray dotted line in the figure is the rotational speed fluctuation of the transmission system during the traditional loading process, and the black solid line is the rotational speed fluctuation after the method of the present invention is adopted. A typical engine starting process consists of two parts, pre-fire and post-fire. Before the engine fires (fuel injection for diesel engines, spark plug ignition for gasoline engines), the motor drives the engine to accelerate. During the compression stroke, the piston compresses the working fluid in the cylinder, and during the expansion stroke, the working fluid in the cylinder pushes the piston to do work, and the change in torque during the pure compression process will lead to fluctuations in the rotational speed during the starting process. After the engine fires, the fuel burns to release heat, causing the pressure in the cylinder to rise suddenly, pushing the piston to output combustion torque to the outside. Therefore, the moment when the engine ignites will lead to a sudden change in torque, and the torque fluctuation range will increase significantly. It can be seen that after adopting this method, the speed fluctuation of the transmission system is significantly reduced, and the smoothness is improved.

The figures and the resulting examples of the above-described embodiments are only intended to illustrate methods and steps for reducing engine start-up vibration by additional motor harmonic torque. It should be pointed out that the starting process in the drawings is only a typical application scenario of the dynamic process, and the dynamic process should include but not be limited to starting, stopping, changing the load and changing the speed of the engine. In addition, the applied traditional power system or hybrid power configuration, the structure, model, connection method and manufacturing process of each component, and the algorithm adopted by each module can all be changed. Equivalent transformations and improvements should not be excluded from the protection scope of the present invention.

Claims (3)

1. a dynamic system active vibration reduction method based on engine instantaneous torque observer, is characterized in that, this method comprises the following steps: 1) Make the engine run according to the set working conditions under the control of the engine control unit; 2) Under each working condition, the vehicle control unit collects the state parameters, control parameters and additional sensor signals of the engine; 3) The engine instantaneous torque observer receives the engine state parameters, control parameters, additional sensor signals and the crankshaft signal measured by the encoder installed at the crankshaft output end collected in step 2), and estimates the instantaneous torque fluctuation of the engine to obtain the engine The instantaneous torque fluctuation signal is sent to the motor controller; the estimation of the instantaneous torque fluctuation of the engine is performed, and the expression is as follows:

where r is the crank radius,

is the crank angle, β is the swing angle of the connecting rod, λ=r/l is the crank connecting rod ratio, l is the center distance between the large and small heads of the connecting rod, D is the cylinder diameter, p _g is the absolute pressure of the gas in the cylinder, and p _b is the crankshaft The absolute pressure of the tank gas, I _crank is the equivalent moment of inertia of the crankshaft; the connecting rod swing angle

is the friction torque of the engine; m _hz is the piston mass, m _lA is the equivalent mass of the small end of the connecting rod, and ω is the crankshaft speed; 4) The motor controller calculates the target harmonic torque through the instantaneous torque fluctuation signal of the engine and generates a corresponding control signal to send to the motor; 5) The motor generates the corresponding harmonic torque according to the received control signal; 6) The instantaneous torque of the engine and the harmonic torque generated by the motor act on the transmission shaft at the same time to realize the vibration reduction of the power system. 2 . The method of claim 1 , wherein the additional sensor signal is an in-cylinder pressure signal obtained by installing a cylinder pressure sensor in each cylinder of the engine. 3 . 3. method as claimed in claim 1 is characterized in that, in described step 4), target harmonic torque calculation expression is as follows:

Among them, M _{t_i} represents the estimation of the engine instantaneous torque fluctuation of the ith cylinder of the engine, and n is the number of cylinders of the engine.

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