KR100507071B1 - Acceleration control method for hbrid electric vehicle - Google Patents

Abstract

It is an object of the present invention to provide an acceleration control method for a hybrid electric vehicle that enables the engine and CVT control to be performed in consideration of the CVT power transmission efficiency, hydraulic loss, and rotational inertia power, so as to improve the optimum driving and acceleration performance of the engine;

Calculating a required vehicle acceleration power by a signal transmitted from an acceleration pedal sensor; A second step of setting an optimum engine power by compensating the CVT power transmission efficiency, the CVT hydraulic loss, and the rotational inertia power caused by the change of the CVT speed ratio to the vehicle acceleration power; Calculating an optimum driving point according to an optimum engine torque and an engine speed caused by the optimum engine power; Calculating a throttle opening degree for outputting the engine torque of the optimum driving point, and calculating a CVT speed ratio for maintaining the engine speed of the optimum driving point; And a fifth step of controlling the engine and the CVT by outputting a control value of the throttle opening degree and the CVT speed ratio calculated in the fourth step.

Description

Acceleration Control Method for Hybrid Electric Vehicles {ACCELERATION CONTROL METHOD FOR HBRID ELECTRIC VEHICLE}

The present invention relates to a hybrid electric vehicle, and more specifically, by controlling the engine and the CVT in consideration of the CVT power transmission efficiency, hydraulic loss and rotational inertia power, the optimum operation and acceleration performance of the engine The present invention relates to an acceleration control method for a hybrid electric vehicle that can be improved.

For example, a hybrid vehicle refers to an efficient combination of two or more different power sources. In most cases, a hybrid vehicle is a system consisting of an engine powered by fuel and an electric motor driven by electricity. It is called a hybrid electric vehicle.

Looking at an example of such a hybrid electric vehicle configuration, as shown in FIG. 1, the stepless transmission 8 including the electric motor 4 on the output side of the engine 2 and the oscillating clutch 6 is disposed thereafter, The drive wheel 10 can be driven by the power output from the continuously variable transmission 8.

In addition, the electric motor 4 is controlled while being supplied with the power of the battery 12 through the motor control unit (MCU), the hybrid control unit (HCU) for total control of the hybrid electric vehicle as the engine control unit (ECU) and It is electrically connected to the transmission control unit (TCU), the battery management system (BMS), and the accelerator pedal sensor (APS) directly operated by the driver to control the motor control unit (MCU) by receiving the current vehicle driving state. will be.

The hybrid electric vehicle uses an electric motor when starting to minimize initial fuel consumption and exhaust gas, and during acceleration, the electric motor assists the engine for a certain speed.

In other words, the car is driven by fuel at low speed and fuel at medium and high speed, and when it exceeds a certain speed even in normal driving, the fuel is changed from electricity to gasoline, thereby improving the load and operating conditions on the engine with the help of an electric motor. There is an advantage that can greatly reduce the exhaust gas emissions.

Looking at the acceleration control process of the hybrid electric vehicle as described above, conventionally, as shown in FIG. ) Calculates the vehicle acceleration power required by the driver using the value measured from the accelerator pedal sensor APS (S200).

After calculating the vehicle acceleration power in step S200, the vehicle acceleration power is set as the optimum engine power (S210), and the optimum engine torque and the engine speed are output based on the optimum engine power (S220).

When the optimum engine torque and engine speed are output in step S220, the operating point of the engine for outputting the same is determined (S230).

The engine operating point outputs the required power and at the same time determines the fuel consumption as the lowest point, the operating point of which is determined as shown in FIG.

In other words, when a constant power output is output from a gasoline engine (iso-power curve), fuel consumption is minimized at the lowest BFC (Brake Specific Fuel Consumption).

Accordingly, the Optimal Operating Line (OOL, Optimal Operating Line) is a curve connecting these points. When a specific power is required in the engine, when the engine is operated at the intersection of the equal power line and the OOL, the required power can be output. In addition, fuel consumption can be minimized.

When the driving point of the engine is determined as described above, the only engine torque and the engine speed corresponding to the advantage are determined.

In this state, the throttle opening degree for the engine torque output of the optimum engine operating point and the CVT transmission ratio for maintaining the engine speed of the engine optimum operating point are calculated (S240).

When the throttle opening degree and the CVT speed ratio control value are determined through the above process, the control value is output and the acceleration mode is terminated after the engine and the CVT control are made (S250).

In step S240, the optimum engine throttle opening degree is calculated as the value of the isothrottle opening degree passing through the engine optimum operating point, and the CVT speed ratio is calculated by the current vehicle speed and the optimum engine speed.

However, in the control method as described above, it is possible to perform the optimum engine operation for obtaining the lowest fuel consumption while outputting the power required by the vehicle without considering the transient response performance of the vehicle. This implies that the acceleration performance is greatly reduced due to the decrease of.

Therefore, the present invention has been invented to solve the above problems, the object of the present invention is to achieve the engine and CVT control in consideration of the CVT power transmission efficiency and hydraulic loss and rotational inertia power, the optimum operation and acceleration of the engine The present invention provides an acceleration control method for a hybrid electric vehicle to improve performance.

In order to realize this, the present invention provides a hybrid electric vehicle that uses a fuel-powered engine and an electric motor at the same time as a power source, and applies CVT (stepless transmission),

Calculating a required vehicle acceleration power by a signal transmitted from an acceleration pedal sensor;

A second step of setting an optimum engine power by compensating the CVT power transmission efficiency, the CVT hydraulic loss, and the rotational inertia power caused by the change of the CVT speed ratio to the vehicle acceleration power;

Calculating an optimum driving point according to an optimum engine torque and an engine speed caused by the optimum engine power;

Calculating a throttle opening degree for outputting the engine torque of the optimum driving point, and calculating a CVT speed ratio for maintaining the engine speed of the optimum driving point;

And a fifth step of controlling the engine and the CVT by outputting a control value of the throttle opening degree and the CVT speed ratio calculated in the fourth step.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

FIG. 1 is a block diagram illustrating a hybrid electric vehicle to which the present invention is applied, and the detailed description thereof will be omitted.

2 is an operation flowchart of a control method according to the present invention, when a driver presses an accelerator pedal for acceleration, a signal thereof is transmitted to a hybrid control unit (HCU).

Then, the hybrid control unit HCU calculates the vehicle acceleration power required by the driver using the value measured from the accelerator pedal sensor APS transmitted thereto (S100).

After the vehicle acceleration power is calculated in the step S100, the CVT power transmission efficiency, the CVT hydraulic loss, and the rotational inertia power are calculated (S110), and the most recent engine power considering the three factors is set (S120).

That is, in the power transmission system consisting of an engine-CVT-drive system, the power loss of the CVT should be taken into consideration. The CVT power loss consists of a slip loss between the belt and the pulley of the CVT and a hydraulic system loss, and a slip loss between the CVT valve and the pulley. Is generated by the shear force of the oil film formed between the belt and the pulley.

The actual friction between the belt and the pulley is the boundary friction of the metal-to-metal contact and the oil contact, and the shear friction is caused by the relative sliding of the belt and the pulley, which is the speed transfer efficiency of the CVT (η _ωcvt ) and engine power (P _{e optimal)} considering the torque transmission efficiency (η _tcvt) are calculated by P _{v desird} / (η η _{ωcvt tcvt).}

Thus CVT hydraulic system power loss (P _hydless) may by line pressure the engine is formed by the flow rate and the line pressure control valve supplied by the pump as a generation loss to drive the oil pump shown as follows.

When P _line is the line pressure, Q _pump is the pump discharge flow rate, η _pump is the pump efficiency, and D _pump is the pump displacement, the CVT hydraulic system power loss (P _hydless ) becomes P _line * Q _pump . Q _pump ) becomes η _{pump *} D _pump * ω _e .

Accordingly, the engine power _{Pe optimal} considering the CVT power transmission efficiency and hydraulic system loss power becomes P _{v desird} / (η _ωcvt η _tcvt ) + (P _hydless ).

In addition, the rotational inertia torque caused by the change of the CVT speed ratio reduces the acceleration force when the vehicle is accelerated, and reduces the deceleration force when the vehicle is decelerated, thus causing a delay in the vehicle speed change. The control considering the inertia torque is required.

The rotational inertia power (P _inertia ) caused by the change of CVT speed ratio is _defined as {η _{tcvt *} N _frg i (di / dt) * J _eq / η _ωcvt } ω _{e *} ωv Becomes

In the above, i is the transmission ratio of CVT, and is defined as the ratio (Wp / Ws) of the driving pulley rotational speed (Wp) and the driven pulley rotational speed (Ws), and i (di / dt) means the transmission ratio and the speed ratio change rate. , J _eq means equivalent inertia (Equivalealent Inertia).

The optimum engine power (P _{e optimal)} considering the three elements in the step S120 is in accordance with the _{P v desird / (η ωcvt η} tcvt) + (P hydless) + (P inertia).

When the optimum engine power is set by the above process, the optimum engine torque and engine speed are output based on the optimum engine power (S130).

When the optimum engine torque and engine speed is output in step S130, it is determined the operating point of the engine for outputting this (S140).

The engine operating point outputs the required power and at the same time determines that the fuel consumption is the smallest point, the operating point of which is determined as shown in FIG.

In other words, when a constant power output is output from a gasoline engine (iso-power curve), fuel consumption is minimized at the lowest BFC (Brake Specific Fuel Consumption).

Accordingly, the Optimal Operating Line (OOL, Optimal Operating Line) is a curve connecting these points. When a specific power is required in the engine, when the engine is operated at the intersection of the equal power line and the OOL, the required power can be output. In addition, fuel consumption can be minimized.

When the driving point of the engine is determined as described above, the only engine torque and the engine speed corresponding to the advantage are determined.

In this state, the throttle opening degree for the engine torque output of the optimum engine operating point and the CVT speed ratio for maintaining the engine speed of the engine optimum operating point are calculated (S150).

When the throttle opening degree and the CVT speed ratio control value are determined through the above process, the control value is output and the acceleration mode is terminated after the engine and the CVT control are made (S160).

In the step S1500, the optimum engine throttle opening degree is calculated as a value of the isothrottle opening degree diagram passing through the engine optimum operating point, and the CVT speed ratio is calculated by the current vehicle speed and the optimum engine speed.

That is, the present invention sets the optimum engine power in consideration of CVT power transmission efficiency, CVT hydraulic loss, and rotational inertia power, and calculates and controls the latest engine torque and engine speed for optimal operation of the engine. It will increase performance.

In the case of performing the acceleration control as described above, in the initial stage of acceleration, as shown in A and B of FIG. 3, the engine power and the throttle show a larger value than the conventional one, and accordingly, the driving torque is also greatly output (see FIG. 3C). It can be seen that the vehicle speed closely follows the reference vehicle speed (D in FIG. 3).

 As described above, according to the present invention, by controlling the engine and CVT in consideration of the CVT power transmission efficiency, hydraulic loss and rotational inertia power, the initial driving torque is greatly increased to improve the optimum operation and acceleration performance of the engine. It is an invention that can be.

1 is a block diagram of a hybrid electric vehicle to which the present invention is applied.

2 is an operational flowchart according to the present invention.

3 (A) (B) (C) (D) are graph diagrams for explaining the effect of the present invention.

4 is a conventional operation flowchart.

5 is a diagram for explaining an optimal curve and an optimal operating point.

Claims (2)

delete A first step of calculating a required vehicle acceleration power by a signal transmitted from an accelerator pedal sensor in a hybrid electric vehicle using a fuel-based engine and an electric motor at the same time and applying CVT (stepless transmission); A second step of setting an optimum engine power by compensating the CVT power transmission efficiency, the CVT hydraulic loss, and the rotational inertia power caused by the change of the CVT speed ratio to the vehicle acceleration power; Calculating an optimum driving point according to an optimum engine torque and an engine speed caused by the optimum engine power; A throttle opening degree calculated for the engine torque output of the optimum driving point and a control value of the throttle opening degree and the CVT speed ratio calculated in the fourth step of calculating the CVT speed ratio for maintaining the engine speed of the optimum driving point; In the acceleration control method of a hybrid electric vehicle comprising a fifth step of outputting the engine and the CVT control, In the second step, when η _ωcvt is CVT power loss efficiency, η _tcvt is torque transmission efficiency, and P _{v desird} is required acceleration power, the engine power _{Pe optimal} considering power transmission efficiency is P _{v desird} / ( η _ωcvt η _tcvt ), When P _line is the line pressure and Q _pump is the pump discharge flow rate, CVT hydraulic power loss (P _hydless ) is calculated as P _line * Q _pump . The engine power _{Pe optimal} considering power transmission efficiency and CVT hydraulic power loss is calculated as P _{v desird} / (η _ωcvt η _tcvt ) + (P _hydless ), The rotational inertia power (P _inertia ) due to the CVT shift ratio is _defined as {η _{tcvt *} N _frg i (di / dt) * J _eq / η _ωcvt } ω _{e *} ωv Is calculated as The power transmission efficiency and the hydraulic system power loss, the rotational inertia optimum engine power considering the power (P _{e optimal)} is a hybrid, it characterized in that the _{P v desird / (η ωcvt η} tcvt) + (P hydless) + (P inertia) Acceleration Control Method for Electric Vehicles.