CN117780540A - Method for starting an internal combustion engine of a two-wheeled vehicle - Google Patents

Abstract

The invention relates to a method for starting an internal combustion engine in a two-wheeled vehicle.

Description

Method for starting an internal combustion engine of a two-wheeled vehicle

Technical field

The invention relates to a method for starting an internal combustion engine of a two-wheeled vehicle.

Background technique

FIG. 1 schematically shows a drive train 10 for a two-wheeled vehicle, in particular a motorcycle, according to the prior art. The internal combustion engine has a separate electric motor 12 for starting the motor and a separate starter generator 14 that generates electrical energy during operation of the internal combustion engine. The starter generator 14 is connected to the crankshaft 18 of the internal combustion engine. The DC starter 18 acts via an additional transmission on a crankshaft 18 which is connected to a sprocket 20 . Therefore, the electric motor 12 and the starter generator 14 are independent of each other and can be optimized independently of each other. In order to save costs, an integrated starter generator (ISG) can be used, which serves not only for starting but also as a generator. Typically this is a permanent magnet synchronous machine (PMSM), which achieves high efficiency and negligible wear not only in motor operation but also in generator operation. However, here, especially when starting, it is necessary to know the electrical position, which is close to the mechanical position (or position) of the ISG or the rotor of the ISG. Since sensors for this do not exist for cost reasons, this position must be estimated. Especially at cold temperatures, and when the internal combustion engine comes to a standstill shortly before top dead center (OT), it is difficult, if not almost impossible, to start.

It is known that, unlike a pilot control device, a current controller is significantly more robust since it sets the currents in the d- and q-axes of the rotary frame to predetermined setpoint values. However, this requires at least two individual current sensors for two of the three phase currents. Since these current sensors are significantly cheaper and more reliable than position sensors, this current regulation can be better implemented in the field. Furthermore, it is known that the electrical position can be deduced using these measured current information signals. However, these so-called sensorless controls (ie controls without position sensors but with current sensors) require detailed knowledge of the characteristics of the electric machine. The underlying control and position estimation algorithm is therefore based on a mathematical model of the electric motor and the corresponding parameters need to be determined during the development phase. In addition, this sensorless motor control is only possible when the crankshaft rotates at a sufficient speed, so this regulation method cannot be operated directly from a standstill. In the present invention we present a concept that consists of an adaptive precontrol device that brings the crankshaft to an initial speed at which we can transfer to the current regulator . In order to be able to adapt the precontrol device and the current controller, we use the information from the two current sensors and the standard crankshaft speed sensor, which of course can only be used at higher speeds. .

Reference is made purely by way of example to the documents US 8749090 B2 and DE 102010040433 A1, which describe a motor control with a dq coordinate transformation, which may however differ from the subject matter of the present application.

Summary of the invention

The invention relates to a two-wheeled vehicle with an integrated starter-generator (ISG), the electric machine of which is capable of operating as a motor and as a generator. In the process of so-called sensorless (position) sensorless control ("sensorless motor control"), the electrical position of the motor should not be determined using a position sensor, but rather with the aid of a current sensor for measuring the phase currents of the motor and with the aid of The mathematical model of the motor is used to determine. However, this type of regulated control of the electric machine is only possible when the crankshaft is moving, so that regulation is generally not possible in a stationary state.

The present application therefore proposes an adaptive control device for motor starting which first brings the crankshaft to a determined speed from which sensorless motor control can be carried out. In this process, a known dq model of the electric machine is used, in which the three-phase currents and voltages are transformed into the rotor-fixed dq coordinate system by means of the known Clarke-Park transformation. The mechanical system is modeled based on the motor torque Tmot, the internal combustion engine's torque Tload and the crankshaft's moment of inertia J according to the formula given at the top of page 3. Determine the motor torque Tmot according to the formula given at the bottom of page 2.

In the framework of the application of the present invention, the unknown parameters R and KM required for the model are determined once and saved in the controller for future startup processes. The parameter R describes the resistance of the motor, and the parameter KM is the motor constant.

To determine the parameter R, in the stationary state a small, gradual voltage is induced on the d-axis which does not cause any movement of the motor. Using the current that can be measured in the steady state, the resistance value R can be determined with the help of the formula on page 3 of the present application.

During the rotational movement of the internal combustion engine, in the case of steady-state current, the motor constant KM is determined online with the help of the crankshaft sensor using the formula on page 3 of the present application.

Description of drawings

FIG1 shows a drive train for a two-wheeled vehicle, in particular a motorcycle, according to the prior art;

Figure 2 shows an integrated starter generator;

FIG3 shows a decoupling network and two individual PI regulators;

Figure 4 shows the algorithm for position estimation;

Figure 5 shows a possible actual hardware implementation of the present invention.

Detailed ways

FIG. 2 shows an integrated starter generator (ISG) 15 which has a precontrol device 24 and a current regulator which is designed using a dq model and can be switched on and off via a trigger. Break. For the starting phase from standstill, a precontrol device can be used, and then, starting from a determined rotational speed, a current regulator can be used. ISG15 is PMSM.

The equation for the dq model is:

Ld*Id＝Ud–R*Id+Lq*Iq*ω _el

and

Lq*Iq＝Uq–R*Iq–Ld*Id*ωel–Km*ωel

The model parameters of PMSM15 are here:

Ld and Lq represent the inductance on the d-axis and q-axis,

·R represents the resistance of PMSM15,

·Km represents the motor constant.

The signals Id, Iq represent the current on the d-axis and q-axis, Ud and Uq represent the voltage on the d-axis and q-axis, and ωel represents the electrical speed. The electrical speed is directly proportional to the mechanical speed. The gain depends on the number of pole pairs of the PMSM 15. Neglecting the locking torque, the motor torque is calculated as follows:

Tmot＝3/2*Np*(Km*iq+(Ld-Lq)*id*iq)

Model mechanical systems with the torque balance between motor torque and load torque. Therefore, the low viscous friction of the internal combustion engine as well as local compression torque peaks are taken into account. Both values can be approximated in a rather uncertain and difficult way. Additionally, the inertia of the crankshaft must be taken into account.

The resulting model equation is given by:

Jnmech＝Tmot-Tload

Among them, Jnmech represents the inertia moment of the crankshaft. The known Clark-Parker transformation is used to transform the three-phase branch system into a rotating dq system.

The transformation depends on the electrical position of the motor.

To regulate the motor, a decoupling network 26 and two individual PI regulators 28, 30 are used, as shown in Figure 3.

A common solution for a position determination algorithm is a phase-locked loop algorithm, which depends on the induced voltage in the fixed frame of the stator. These so-called α-induced voltages and β-induced voltages are calculated as follows:

Uind,α=Uα-RIα-LIα

and

U_ind,β＝Uβ-RIβ-LIβ

Here, Ia and Iβ represent the time derivatives of the α current and the β current, and L represents the average value of the inductance on the d-axis and the q-axis.

The transformation from a rotating frame to a stator-fixed frame is achieved with the aid of Clark-Park transformation.

The algorithm used for position estimation is shown in Figure 4. The parameters of the included PI regulator need to be determined during development.

The simplified schematic diagram of a positive feedback regulator contains the static relationship between the reference torque and the input voltage on the q-axis and is given with the help of:

u_q,ffwd＝2/(3Np*R/Km*Mmot,ref

and

ud,ffwd＝0

When starting the two-wheeled vehicle, the current regulator 24 is activated. If the mechanical speed of the PMSM 15 is greater than a certain threshold value, the internal combustion engine can be started. The speed regulator then takes over control of the internal combustion engine. Here, the current regulator 24 can first be used for rearward rotation and then can be switched to forward rotation.

In feedforward regulators and current regulators of motors, the resistance and motor constants are unknown. To avoid false starts, parameters are estimated.

In the first approach, the two parameters are estimated independently of each other. In the stationary state, a small step voltage is induced on the d-axis. However, this voltage does not cause movement of the motor. The resulting steady-state value of the current response represents an online measure of the resistance of the motor:

R＝u_d,steady/i_d,steady

The calculation of the motor constant is performed at a torque at which the motor rotates and the current is in steady state. Additionally, a crankshaft sensor measures the rotational speed of the internal combustion engine.

The motor constants are calculated online using the following:

K_m=(u_q-Ri_q)/(k·n_mot)-L_d i_d

k, L_d, L_q and K_m are free calibration parameters which need to be determined during development.

The two calculated model parameters are cached in the controller and used in the feedforward regulator during the next start.

One possible practical hardware implementation 40 of the invention is shown in Figure 5 . An electronic control unit (ECU) 42 is connected to the vehicle battery 44 . A control algorithm is implemented in the ECU 42 which essentially takes over the control of the internal combustion engine of the two-wheeled vehicle and the described control of the ISG.

The three-phase generator 46 is connected to the inverter 48 . The inverter 48 is connected to the battery 44 and the vehicle electrical system. Inverter 48 has three high-side switches 50a, 50b, 50c and three low-side switches 52a, 52b, 52c.

ECU 42 contains information on at least two of the three phase currents of inverter 48 . The two phase currents can be the current from the low-side switches 50a, 50b to ground, the current from the low-side switches 50b, 50c to ground, or the current from the low-side switches 50a, 50c to ground.

An alternative solution could be to measure the two phase currents of the generator 46 .

Alternatively, it is also possible to measure all three currents with the low-side switches 50a, 50b, 50c connected to ground or all three phases of the generator 46. For this, additional pins are required at the controller.

The inverter 48 is actuated in such a way that actuating signals resulting from the control algorithm are transmitted to the inverter 48 from a controller 42 with three separate lines in order to actuate the three half-bridges. A signal from the controller operates a half-bridge, that is, if the signal is high, the high-side switch is on and the low-side switch is off. If the signal is low, the low-side switch is on and the high-side switch is off.

Claims (5)

1. A method for starting an internal combustion engine in the case of a two-wheeled vehicle, especially a motorcycle, wherein an integrated starter generator (ISG) is used for starting, wherein the ISG is caused to rotate backwards until shortly before reaching top dead center, And then immediately rotate the ISG forward, the method has at least the following steps: · When starting the two-wheeler, activate the pre-control device (24), • Switching to the current regulator and subsequently to the speed regulator of the internal combustion engine, if the mechanical speed is greater than the ISG (15) by a certain threshold value in each case. 2 . The method according to claim 1 , characterized in that the resistance and the motor constant are estimated in the pilot control device. 3. Method according to claim 2, characterized in that the resistance and the motor constant are estimated independently of each other in the precontrol device. 4. Method according to claim 2 or 3, characterized in that in the stationary state, a small step voltage is induced at the d-axis, wherein the resulting steady-state value of the current response represents said A measure of the electrical resistance of a motor. 5. Hardware (40) having an electronic control unit (42) connected to the vehicle battery (44) and having a three-phase generator (46) connected to the inverter (48) Connection, wherein the inverter (48) is connected to the battery (44) and the vehicle power grid, wherein the inverter (48) has three high-side switches (50a, 50b, 50c) and three low-side switches (52a, 52b, 52c).