CN117780540A

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

Info

Publication number: CN117780540A
Application number: CN202311277177.1A
Authority: CN
Inventors: B·阿尔特; W·费舍尔
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2022-09-28
Filing date: 2023-09-28
Publication date: 2024-03-29
Also published as: DE102022210261A1

Abstract

The invention relates to a method for starting an internal combustion engine in the case of 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

Fig. 1 shows an exemplary 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 motor starting and a separate starter generator 14 that generates electrical energy during operation of the internal combustion engine. The starter generator 14 is connected to a 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. Thus, 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 is used not only for starting but also as a generator. Typically, this is a Permanent Magnet Synchronous Machine (PMSM) that achieves high efficiency and negligible wear not only in motor operation, but also in generator operation. However, in this case, in particular during starting, it is necessary to know the electrical position, which is close to the mechanical position (or position) of the ISG or of the rotor of the ISG. Since for cost reasons no sensor is present for this, the position must be estimated. Particularly in the case of cold temperatures and when the internal combustion engine is stationary shortly before top dead center (OT), it is difficult, if not almost impossible, to start.

As is known, unlike the pre-control device, the current regulator is significantly more robust, since it regulates the current in the d-axis and q-axis of the rotating frame to a predetermined setpoint value. However, at least two individual current sensors are required for this purpose for two of the three phase currents. Since these current sensors are significantly more cost effective and reliable than position sensors, the current regulation can be better implemented in the field. It is also known that the electrical position can be deduced by means of these measured current information signals. However, these so-called sensorless adjustments (i.e. adjustments without position sensors but with current sensors) require detailed knowledge of the motor characteristics. Thus, the underlying adjustment and position estimation algorithm is based on a mathematical model of the electric motor and requires that corresponding parameters be determined during the development phase. In addition, the sensorless motor control can be achieved only when the crankshaft rotates at a sufficient rotational speed, so that the regulation method cannot be operated directly from a stationary state. In the present invention we propose a concept comprising an adaptive pre-control device that brings the crankshaft to an initial rotational speed at which we can transfer to the current regulator. In order to be able to adapt the pre-control device and the current regulator, we use information from two current sensors and from a standard crankshaft speed sensor, which can of course only be used at higher speeds.

Purely exemplary reference documents US 8749090 B2 and DE 10201004433 A1 describe motor control with dq coordinate transformation, however, possibly differing from the subject matter of the present application.

Disclosure of Invention

The invention relates to a two-wheeled vehicle with an Integrated Starter Generator (ISG), the electric machine of which can be operated both motor-wise and generator-wise. In the course of the so-called sensorless control ("sensorless motorcontrol"), the electrical position of the motor should not be determined using a position sensor, but rather by means of a current sensor for measuring the phase currents of the motor and by means of a mathematical model of the motor. However, this type of regulated control of the motor is only possible when the crankshaft is in motion, 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 performed. In this process, a dq model of the motor known per se is used, in which three-phase currents and voltages are transformed into a rotor-fixed dq coordinate system by means of the known Clarke Park Transformation (Clarke Park Transformation). The mechanical system is modeled based on the motor torque Tmot, the torque Tload of the internal combustion engine and the moment of inertia J of the crankshaft according to the formula given above page 3. According to the formula given below page 2, the motor torque Tmot is determined.

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

In order to determine the parameter R, a small, progressive voltage is induced in the stationary state on the d-axis, which does not lead to a movement of the motor. By means of the current which can be measured in the steady state, the resistance value R can be determined by means of the formula on page 3 of the present application.

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

Drawings

Fig. 1 shows a drive train for a two-wheeled vehicle, in particular a motorcycle, according to the prior art;

FIG. 2 illustrates an integrated starter generator;

fig. 3 shows a decoupling network and two individual PI regulators;

FIG. 4 shows an algorithm for position estimation;

FIG. 5 shows one possible practical hardware implementation of the invention

Detailed Description

Fig. 2 shows an Integrated Starter Generator (ISG) 15, which has a pre-control device 24 and a current regulator, which is designed by means of a dq model and can be switched on and off by a trigger. For the start-up phase starting from a standstill state, a pre-control device can be used, after which, starting from a determined rotational speed, a current regulator is used. ISG15 is PMSM.

The dq model equation is:

Ld*Id＝Ud–R*Id+Lq*Iq*ω _el

and

Lq*Iq＝Uq–R*Iq–Ld*Id*ωel–Km*ωel

the model parameters for PMSM15 are here:

ld and Lq denote inductances on the d-axis and q-axis,

r represents the resistance of the PMSM15,

km represents the motor constant.

The signals Id, iq represent currents on the d-axis and q-axis, ud and Uq represent voltages on the d-axis and q-axis, and ωel represents an electrical speed. The electrical speed is directly proportional to the mechanical speed. The gain depends on the number of pole pairs of PMSM 15. The motor torque is calculated as follows, ignoring the detent torque:

Tmot＝3/2*Np*(Km*iq+(Ld-Lq)*id*iq)

the mechanical system is modeled by means of a torque balance between motor torque and load torque. Therefore, low viscous friction and local compression torque peaks of the internal combustion engine are considered. Both values can be approximated in a rather uncertain and difficult way. Additionally, the inertia of the crankshaft must be considered.

The model equation thus derived is given by:

Jnmech＝Tmot-Tload

wherein Jnmech represents the moment of inertia of the crankshaft. The transformation from a three-phase tributary system (strangasystem) to a rotating dq system is performed by means of the well-known clark park transformation.

The transformation depends on the electrical position of the motor.

For regulating the motor, a decoupling network 26 and two individual PI regulators 28, 30 are used, as shown in fig. 3.

A common scheme for the position determination algorithm is the Phase-Locked-Loop algorithm, which depends on the induced voltage in the stator fixed frame. These so-called alpha-induced voltages and beta-induced voltages are calculated by means of:

Uind,α＝Uα-RIα-LIα

and

U_ind,β＝Uβ-RIβ-LIβ

here Ia and I beta represent the time derivatives of the alpha and beta currents and L represents the average value of the inductances on the d and q axes.

The transformation from the rotating frame to the stator-fixed frame is achieved by means of the clark transformation.

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

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

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 PMSM15 is greater than a determined threshold, the internal combustion engine can be started. The speed regulator then takes over the regulation of the internal combustion engine. Here, the current regulator 24 can be used for backward rotation first, and then can be switched to forward rotation.

In the feed forward regulator and the current regulator of the motor, the resistance and the motor constant are unknown. To avoid false starts, the parameters are estimated.

In the first scheme, two parameters are estimated independently of each other. In the rest state, a small step voltage is induced on the d-axis. However, this voltage does not result in 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 with the following moments: with this torque, the motor rotates and the current is in steady state. Additionally, a crankshaft sensor measures the rotational speed of the internal combustion engine.

The calculation of the motor constant is performed in an on-line manner by means of:

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 that need to be determined during development.

The two calculated model parameters are buffered in the controller and used in the feed forward regulator during the next start-up.

One possible practical hardware implementation 40 of the present invention is shown in fig. 5. An Electronic control unit (Electronic ControlUnit, ECU) 42 is connected to the vehicle battery 44. A control algorithm is implemented in the ECU42, which mainly takes over the control of the internal combustion engine of the two-wheeled vehicle and the control of the ISG described.

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

ECU42 contains information of at least two of the three phase currents of inverter 48. The two phase currents can be a current from the low side switches 50a, 50b to ground, a current from the low side switches 50b, 50c to ground, or a current from the low side switches 50a, 50c to ground.

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

Alternatively, all three currents of the low side switches 50a, 50b, 50c to ground or all three phases of the generator 46 can also be measured. For this purpose, additional pins are required at the controller.

The inverter 48 is operated by: the control signals from the control algorithm are transmitted from the controller 42 having three separate lines to the inverter 48 in order to control the three half-bridges. A signal from the controller steers 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

1. Method for starting an internal combustion engine in the case of a two-wheeled vehicle, in particular a motorcycle, wherein an Integrated Starter Generator (ISG) is used for starting, wherein the ISG is rotated backwards until shortly before top dead center is reached and then immediately before the ISG is rotated forwards, the method having at least the following steps:

activating a pre-control device (24) when starting the two-wheeled vehicle,

switching to a current regulator and then to a speed regulator of the internal combustion engine if a defined threshold value is greater than the mechanical speed of the ISG (15).

2. The method of claim 1, wherein the resistance and motor constant are estimated in the pre-control device.

3. The method according to claim 2, characterized in that the resistance and the motor constant are estimated independently of each other in the pre-control means.

4. A method according to claim 2 or 3, characterized in that in a stationary state a small step voltage is induced at the d-axis, wherein the resulting steady state value of the current response represents a measure of the resistance of the motor.

5. Hardware (40) having an electronic control unit (42) and having a three-phase generator (46) connected to a vehicle battery (44), said three-phase generator being connected to an inverter (48), wherein the inverter (48) is connected to the battery (44) and to a vehicle electrical system, wherein the inverter (48) has three high-side switches (50 a, 50b, 50 c) and three low-side switches (52 a, 52b, 52 c).