Control system and control method for reducing drive shaft vibrations of an environmentally friendly vehicle

Abstract

This disclosure relates to a control system for reducing drive shaft vibration in environmentally friendly vehicles. The control system includes: a drive shaft speed extraction unit for extracting the actual speed of the drive shaft of the motor and extracting the drive shaft speed after removing the forced vibration component transmitted from the engine to the drive shaft; a model speed calculation unit for calculating the model speed of the drive shaft; a free vibration calculation unit for calculating the free vibration component based on the deviation between the drive shaft speed and the calculated model speed; and a first torque compensation unit for calculating a free vibration reduction compensation torque from the free vibration component to reduce drive shaft vibration.

Description

Technical Field

[0001] This disclosure relates to a control system and method for reducing drive shaft vibration in environmentally friendly vehicles. More particularly, this disclosure relates to a control system and method for reducing drive shaft vibration in environmentally friendly vehicles, wherein the control system and method use a motor mechanically connected to the drive shaft to simultaneously reduce free vibration generated in the drive shaft and forced vibration generated by the engine. Background Technology

[0002] Environmentally friendly vehicles, such as electric vehicles (EVs) and hybrid vehicles (HEVs), use electric motors as their drive source. Electric vehicles operate solely on the power of an electric motor powered by battery electricity. Hybrid vehicles operate by effectively combining the power of an engine and the power of an electric motor.

[0003] On the other hand, a drawback of the aforementioned environmentally friendly vehicles is that they cannot achieve the mechanical damping effect of traditional torque converters. Therefore, when the driver shifts gears or suddenly accelerates / decelerates (tip-in / out), or when the engine clutch engages, vibrations occur in the drive shaft, resulting in vibration phenomena such as jolts and jerks (sudden, momentary movements). In other words, because the damping mechanisms existing between each torque source (engine and motor) and the drive system are eliminated or reduced, there is a problem of not effectively attenuating vibrations from the torque sources or from external sources. To reduce this vibration generated in the drive shaft, it is necessary to extract the vibration components of the drive shaft. Since vibration damping performance varies depending on the accuracy of vibration component extraction, accurate extraction of vibration components is crucial.

[0004] The factors affecting the drive shaft can be broadly categorized into free vibration caused by the shaft's rotation and forced vibration transmitted from the engine to the motor. While separate controls exist to reduce free and forced vibrations, these separate controls can cause mutual interference. In particular, the torque derived to reduce free vibrations affects the torque derived to reduce forced vibrations. This results in a weakening of the overall control performance used to reduce vibrations. Summary of the Invention

[0005] The purpose of this disclosure is to provide a control system and method for reducing drive shaft vibration in environmentally friendly vehicles, which prevents interference between free vibration compensation torque for reducing free vibration and forced vibration compensation torque for reducing forced vibration.

[0006] According to one aspect of this disclosure, a control system for reducing drive shaft vibration in an environmentally friendly vehicle is provided. The control system for reducing drive shaft vibration in an environmentally friendly vehicle includes: a drive shaft speed extraction unit for extracting the actual speed of the drive shaft of the motor and extracting the drive shaft speed after removing the forced vibration component transmitted from the engine to the drive shaft; a model speed calculation unit for calculating the model speed of the drive shaft; a free vibration calculation unit for calculating a free vibration component based on the deviation between the drive shaft speed and the calculated model speed; and a first torque calculation unit for calculating a free vibration reduction compensation torque from the free vibration component to reduce drive shaft vibration.

[0007] According to one aspect of this disclosure, in a control system, a drive shaft speed extraction unit can extract the drive shaft speed after removing the forced vibration component based on a forced vibration frequency derived from the engine shaft speed.

[0008] According to one aspect of this disclosure, in the control system, the forced vibration frequency can be the vibration frequency of the engine, which is calculated based on the number of cylinders and the engine's revolutions per minute.

[0009] According to one aspect of this disclosure, in a control system, a drive shaft speed extraction unit may include: a filtering unit for extracting a forced vibration component from the actual speed of the drive shaft based on a forced vibration frequency; an amplitude compensation unit for compensating the amplitude of the forced vibration component; and a forced vibration removal unit for calculating the drive shaft speed, the drive shaft speed being a value obtained by subtracting the compensated amplitude of the forced vibration component from the actual speed of the drive shaft.

[0010] According to one aspect of this disclosure, in the control system, the filtering unit is configured with a combination of a low-pass filter and a high-pass filter that sets the forced vibration frequency to the cutoff frequency.

[0011] According to one aspect of this disclosure, in a control system, low-pass filters and high-pass filters can be designed to not change the phase of the actual speed of the drive shaft.

[0012] According to one aspect of this disclosure, in a control system, the model speed calculation unit may include: a drive shaft output required torque calculation unit, which calculates the drive shaft output required torque based on the torque transmitted to the drive shaft; a drive shaft input torque estimation unit, which estimates the drive shaft input torque input to the drive shaft using the actual speed of the drive shaft; a disturbance torque calculation unit, which estimates the disturbance torque by combining the drive shaft output required torque and the drive shaft input torque; and a speed calculation unit, which calculates the drive shaft model input torque obtained by adding the disturbance torque to the drive shaft output required torque using the calculated disturbance torque, and calculates the model speed using the drive shaft model, wherein the drive shaft model input torque is set as the input in the drive shaft model.

[0013] According to one aspect of this disclosure, in a control system, the model velocity may refer to the ideal drive shaft velocity excluding the free vibration component, and the value obtained by subtracting the model velocity from the drive shaft velocity may refer to the free vibration component after removing the forced vibration component.

[0014] According to another aspect of this disclosure, a control method for reducing drive shaft vibration in an environmentally friendly vehicle is provided. The control method for reducing drive shaft vibration in an environmentally friendly vehicle includes: extracting the actual speed of the drive shaft of the motor; removing the forced vibration component transmitted from the engine to the drive shaft from the actual speed of the drive shaft; calculating a model speed of the drive shaft; calculating a free vibration component based on the deviation between the drive shaft speed after removing the forced vibration component and the calculated model speed; and calculating a free vibration reduction compensation torque from the free vibration component for reducing drive shaft vibration.

[0015] According to one aspect of this disclosure, in the control method, removing the forced vibration component from the actual speed of the drive shaft may include: filtering the actual speed of the drive shaft based on a forced vibration frequency derived from the speed of the engine shaft. Therefore, the drive shaft speed after removing the forced vibration component can be extracted.

[0016] According to one aspect of this disclosure, in the control method, removing the forced vibration component from the actual speed of the drive shaft may include: setting the forced vibration frequency to a cutoff frequency and extracting the forced vibration component from the actual speed of the drive shaft; compensating for the amplitude of the forced vibration component; and calculating the drive shaft speed, which is a value obtained by subtracting the compensated amplitude of the forced vibration component from the actual speed of the drive shaft.

[0017] According to one aspect of this disclosure, in the control method, the model velocity may refer to the ideal drive shaft velocity excluding free vibration components. The value obtained by subtracting the model velocity from the drive shaft velocity may be the free vibration component after removing the forced vibration component.

[0018] The control system for reducing drive shaft vibration of an environmentally friendly vehicle according to embodiments of the present disclosure prevents interference between the free vibration compensation torque for reducing free vibration and the forced vibration compensation torque for reducing forced vibration. Attached Figure Description

[0019] Figure 1 A diagram illustrating the system configuration of a hybrid vehicle according to an embodiment of the present disclosure;

[0020] Figure 2 A block diagram illustrating a control system for reducing drive shaft vibration in an environmentally friendly vehicle according to an embodiment of the present disclosure;

[0021] Figure 3 A block diagram illustrating the drive shaft speed extraction unit according to an embodiment of the present disclosure;

[0022] Figure 4 A block diagram illustrating the model velocity calculation unit according to an embodiment of the present disclosure;

[0023] Figure 5 A flowchart illustrating a control method for reducing drive shaft vibration in an environmentally friendly vehicle according to embodiments of the present disclosure; and

[0024] Figure 6 A graph illustrating the application effect of a control system for reducing drive shaft vibration in an environmentally friendly vehicle according to an embodiment of this disclosure. Detailed Implementation

[0025] The advantages and features of this disclosure, as well as the methods for achieving said advantages and features, will become clear from the following detailed description of the embodiments and in conjunction with the accompanying drawings. However, this disclosure is not limited to the embodiments disclosed below. Various different embodiments of this disclosure can be implemented. The embodiments are provided to fully disclose the concepts of this disclosure and to enable those skilled in the art to fully understand the scope of this disclosure. However, the scope of this disclosure should be defined only by the claims. Throughout the specification, the same reference numerals refer to the same components.

[0026] The terms "unit," "module," etc., used in this specification refer to a single component that performs at least one function or operation and can be implemented as hardware, software, or a combination of hardware and software. When a component, device, controller, unit, element, etc., of this disclosure is described as having a purpose or performing an operation, function, etc., that component, device, controller, or element should be considered herein as "configured to" satisfy that purpose or perform that operation or function. Furthermore, the controllers, units, modules, etc., described herein may include processors programmed to satisfy the stated purpose or perform the stated operation or function.

[0027] Furthermore, to distinguish components with the same name, the terms "first," "second," etc., are used in this specification. In the following description, there is no need to restrict this order.

[0028] This disclosure is described in detail by way of illustration. Furthermore, the foregoing description pertains to embodiments of this disclosure. This disclosure can be implemented in various environments and with various modifications and combinations. Modifications or substitutions to the disclosure can be made within the scope of the inventive concept disclosed herein, the equivalents of the content described herein, and / or the scope of the technology or knowledge in the art. Optimization requirements for implementing the technical ideas of this disclosure are described with reference to embodiments. Various modifications required in the field of applying this disclosure, as well as various modifications required for using this disclosure, are feasible. Therefore, the detailed description of this disclosure above is not intended to impose any limitation on the claimed embodiments. Furthermore, the claims should also be construed as covering other embodiments.

[0029] Figure 1 A diagram illustrating the system configuration of a hybrid vehicle according to an embodiment of the present disclosure.

[0030] Reference Figure 1 The diagram shows the structure of a transmission system in the form of a transmission-mounted electric device (TMED) with the gearbox 14 located on the output side of the drive motor 13.

[0031] The drive source for driving the vehicle includes: an engine 11 and a drive motor 13 arranged in series; an engine clutch 12 disposed between the engine 11 and the drive motor 13 to allow or disable power transmission between the engine 11 and the drive motor 13; a gearbox 14 that changes the speed of the power from the engine 11 and the drive motor 13 and transmits it to the drive shaft; and a starter generator 15 directly connected to the engine 11 to enable power transmission.

[0032] The engine clutch 12 allows or disables power transmission between the two drive sources used to drive the vehicle, namely the engine 11 and the drive motor 13, by engaging or disengaging the clutch.

[0033] The battery 18, which serves as the vehicle's power source (electrical power supply), is connected to the drive motor 13 and the starter generator 15 via an inverter 16, enabling it to be charged and discharged. The battery 18 is connected to a battery management system (BMS) 19. The inverter 16 converts the direct current from the battery 18 into a three-phase alternating current for driving the drive motor 13 and the starter generator 15, and applies the generated alternating current to the drive motor 13 and the starter generator 15.

[0034] The starter generator 15 is a device that performs the functions of a starter motor and a generator. When starting the vehicle, the starter generator 15 transmits its own power to the engine 11 via a power transmission mechanism (e.g., a belt or pulley), or receives rotational force from the engine 11 to generate electricity. In addition, the starter generator 15 uses the electrical energy generated during power generation to charge the battery 18.

[0035] Figure 2 A block diagram illustrating a control system for reducing drive shaft vibration in an environmentally friendly vehicle according to an embodiment of this disclosure.

[0036] Reference Figure 1 and Figure 2 The control system 1 for reducing drive shaft vibration in an environmentally friendly vehicle includes a free vibration compensation torque calculation unit 100 for calculating a free vibration compensation torque to reduce free vibration. The control system 1 also includes a forced vibration compensation torque calculation unit 200 for calculating a forced vibration compensation torque to reduce forced vibration. According to an embodiment of this disclosure, the control system 1 for reducing drive shaft vibration in an environmentally friendly vehicle reduces both free vibration generated in the drive shaft of the motor 13 and forced vibration transmitted from the engine to the drive shaft of the motor 13. The control system 1 also prevents interference between the free vibration compensation torque for reducing free vibration and the forced vibration compensation torque for reducing forced vibration. Therefore, in the control system 1 for reducing drive shaft vibration in an environmentally friendly vehicle, the forced vibration frequency is considered when calculating the free vibration compensation torque.

[0037] The free vibration compensation torque calculation unit 100 calculates the free vibration compensation torque for reducing the free vibration generated in the drive shaft of the drive motor 13. The drive shaft is the shaft that outputs the torque of the drive motor 13. Therefore, the drive shaft can be the output shaft of the drive motor and the input of the gearbox. In this case, the drive shaft speed is the same as the drive motor speed; therefore, the free vibration compensation torque calculation unit 100 extracts the free vibration component based on the drive shaft speed rather than the drive motor speed. The drive shaft speed sensor 51 measures the actual speed of the drive shaft that rotates due to the drive of the drive motor. The actual speed of the drive shaft is used as a variable in the process of calculating the model speed and in the process of extracting the free vibration component. The free vibration compensation torque calculation unit 100 includes a drive shaft speed extraction unit 110, a model speed calculation unit 120, a free vibration calculation unit 130, and a first torque calculation unit 140.

[0038] The drive shaft speed extraction unit 110 extracts the forced vibration component from the actual speed of the drive shaft. Vibration of the drive shaft transmitted from the engine to the drive motor is defined as forced vibration. Vibration generated by the rotation of the drive shaft via the drive motor is defined as free vibration. However, since the compensation torque derived for control purposes to reduce free vibration includes torque for reducing forced vibration generated by the engine, this compensation torque interferes with the compensation torque calculated by separate control for reducing forced vibration. In other words, the free vibration compensation torque derived by each control process interferes with the forced vibration compensation torque. Therefore, according to an embodiment of this disclosure, the drive shaft speed extraction unit 110 uses the forced vibration frequency extracted from the forced vibration signal to remove the forced vibration component from the free vibration compensation torque. The drive shaft speed extraction unit 110 receives the forced vibration frequency of the forced vibration signal extracted from the forced vibration extraction unit 210, which will be described below. Specifically, the forced vibration frequency refers to the cutoff frequency used in the forced vibration extraction unit 210 to extract only the forced vibration component. In this case, the forced vibration frequency refers to the engine vibration frequency calculated based on the number of engine cylinders and engine speed. For example, in the case of a four-cylinder, four-stroke internal combustion engine, two power strokes occur for every one rotation of the engine. Therefore, a power stroke component at twice the engine speed can be observed, and this can be taken into account to determine the cutoff frequency. The signal obtained by removing the forced vibration component from the actual speed signal of the drive shaft is the drive shaft speed signal. In other words, the drive shaft speed is defined as the signal obtained by subtracting the forced vibration component from the actual speed of the drive shaft.

[0039] The model speed calculation unit 120 uses vehicle signals to calculate a model speed, excluding vibration components, as the speed of a virtual drive shaft. Vehicle signals include at least one of vehicle speed, accelerator pedal position sensor (APS) value, and brake pedal sensor (BPS) value. An ideal model of the drive shaft is designed, i.e., a model capable of calculating an ideal drive shaft speed (model speed) that ignores vibration, in order to extract the free vibration components of the drive shaft. The designed model is used to calculate the model speed as the drive shaft speed excluding free vibration components. The difference between the calculated model speed and the drive shaft speed is used to extract the free vibration components.

[0040] At this point, when the model velocity is accurately calculated as the ideal drive shaft velocity excluding vibration components, the accurate vibration components are extracted by calculating the difference between the two values. However, the actually calculated model velocity has an error component compared to the ideal drive shaft velocity excluding vibration components. To eliminate this error, the difference between the model velocity and the actual drive shaft velocity is calculated, and then error cancellation control using a high-pass filter (HPF) or similar method is implemented. For this, it is necessary to determine the order of the error cancellation controller that is suitable for the form (order) of the error components. Generally, the order of the error cancellation controller increases proportionally to the order of the error components. As the order of the error cancellation controller increases, phase delays occur more frequently. Therefore, vibration components that differ from the actual vibration are extracted. In other words, the lower the order of the error components, the more accurate the free vibration components can be extracted. Furthermore, to reduce the order of the error cancellation controller, the model velocity needs to be calculated as close as possible to the ideal drive shaft velocity excluding free vibration components.

[0041] According to an embodiment of this disclosure, the model velocity calculation unit 120 observes the disturbance torque applied to the vehicle by applying a disturbance observer when calculating the model velocity. The model velocity calculation unit 120 compensates for the disturbance torque when calculating the model velocity. Therefore, the model velocity calculation unit 120 minimizes the order of the error components included in the model velocity, thereby improving the extraction accuracy of the free vibration components.

[0042] The free vibration calculation unit 130 calculates the free vibration component based on the deviation between the drive shaft speed and the model speed calculated by the model speed calculation unit 120. The free vibration calculation unit 130 applies an error cancellation controller, such as a high-pass filter, to the difference between the model speed and the drive shaft speed to calculate the free vibration component. In this case, the free vibration component is the signal after removing the forced vibration component.

[0043] The first torque calculation unit 140 calculates a free vibration reduction compensation torque for reducing drive shaft vibration based on the free vibration components. Specifically, the first torque calculation unit 140 calculates the reverse phase signal of the free vibration components extracted by the free vibration calculation unit 130. The first torque calculation unit 140 calculates the free vibration reduction compensation torque by multiplying the reverse phase signal of the free vibration components by a reference torque. The reference torque is a preset constant, or a predetermined ratio of the engine torque or the total torque applied to the drive system. Optionally, the reference torque refers to a value obtained by multiplying the engine torque or the total torque applied to the drive system by the amplitude ratio in the frequency domain.

[0044] The forced vibration compensation torque calculation unit 200 calculates the forced vibration compensation torque for reducing the forced vibration transmitted to the drive shaft of the drive motor 13 due to the rotation of the engine 11 or the rotation of the engine shaft. The forced vibration compensation torque calculation unit 200 includes a forced vibration extraction unit 210, a reference signal generation unit 220, a filter coefficient determination unit 230, a phase determination unit 240, and a second torque calculation unit 250.

[0045] The forced vibration extraction unit 210 extracts forced vibrations based on the engine shaft speed. The forced vibration extraction unit 210 is implemented as a band-pass digital filter, which only allows forced vibration components generated during the power stroke of the engine 11 to pass through. In this case, the cutoff frequency of the digital filter can be used by pre-determining a desired frequency domain, or by changing it based on the engine 11's rotational speed. For example, in the case of a four-cylinder, four-stroke internal combustion engine, two power strokes occur for every one mechanical rotation, thus the power stroke component at twice the engine 11's rotational speed is observed, and this is taken into account to determine the cutoff frequency. The determined cutoff frequency is applied so that the drive shaft speed extraction unit 110 removes the forced vibration components from the actual speed of the drive shaft.

[0046] The reference signal generation unit 220 generates a reference signal based on the rotation angle (phase) of the drive motor 13. The rotation angle of the drive motor 13 is measured by the position measuring device 52. For example, the position measuring device 52 includes a resolver. For example, the reference signal is a unit sine wave with an amplitude of 1.

[0047] As an example, the reference signal generation unit 220 generates a result that multiplies the rotation angle of the drive motor 13 by 2 (hereinafter referred to as double rotation angle). In the case of a vehicle equipped with a four-cylinder four-stroke internal combustion engine, two working strokes occur every time the crankshaft rotates once. Therefore, the rotation angle of the drive motor 13 is multiplied by 2; however, the multiplier may be different for different internal combustion engines.

[0048] The filter coefficient determination unit 230 determines filter coefficients that minimize the phase difference between the reference signal generated by the reference signal generation unit 220 and the forced vibration signal extracted by the forced vibration extraction unit 210. In this case, the reference signal generated by the reference signal generation unit 220 and the forced vibration signal extracted by the forced vibration extraction unit 210 have the same frequency. First, the filter coefficient determination unit 230 calculates the filter coefficients that minimize the phase difference between the reference signal generated by the reference signal generation unit 220 and the forced vibration signal extracted by the forced vibration extraction unit 210 using a recursive least squares (RLS) algorithm. The filter coefficient determination unit 230 uses the calculated filter coefficients to filter the reference signal generated by the reference signal generation unit 220. Furthermore, the filter coefficient determination unit 230 calculates the phase difference between the reference signal generated by the reference signal generation unit 220 and the forced vibration signal extracted by the forced vibration extraction unit 210.

[0049] The phase determination unit 240 calculates the speed signal by differentiating the rotation angle of the drive motor 13 measured by the position measuring device 52. Using the calculated speed signal and the filter coefficients determined by the filter coefficient determination unit 230, the phase determination unit 240 detects the phase difference between the reference signal generated by the reference signal generation unit 220 and the forced vibration signal extracted by the forced vibration extraction unit 210. Furthermore, the phase determination unit 240 detects a compensation value for compensating the phase difference caused by the transmission delay from the forced vibration extraction unit 210 to the drive motor 13. The phase determination unit 240 also detects a compensation value for compensating the phase delay caused by the forced vibration extraction unit. In this case, the phase delay refers to the phase delay caused by the forced vibration extraction unit 210, i.e., the bandpass filter. Specifically, the phase determination unit 240 generates a synchronization signal synchronized with the forced vibration signal extracted by the forced vibration extraction unit 210 based on the compensation value for compensating the phase difference caused by the transmission delay from the forced vibration extraction unit 210 to the drive motor 13 and the compensation value for compensating the phase delay caused by the forced vibration extraction unit 210. Phase determination unit 240 generates a synchronization signal with a phase obtained by subtracting the phase difference detected by phase determination unit 240 from the phase generated by reference signal generation unit 220, and adding the compensation value detected by phase determination unit 240. In this case, phase determination unit 240 can further add the compensation value used to compensate for the phase delay caused by forced vibration extraction unit 210.

[0050] The second torque calculation unit 250 uses the phase generated by the reference signal generation unit 220, the phase difference between the reference signal and the forced vibration signal detected by the phase determination unit 240, and the compensation value detected by the phase determination unit 240 to generate a reverse phase signal. The second torque calculation unit 250 calculates the forced vibration reduction compensation torque by multiplying the generated reverse phase signal by the reference torque.

[0051] The motor controller (MCU) 17 generates the integration torque, which is the value obtained by adding the free vibration reduction compensation torque to the forced vibration reduction compensation torque. The motor controller 17 calculates the input torque applied to the drive motor 13 by adding the command torque to the integration torque. The command torque refers to the command torque from a higher-level controller (e.g., a hybrid power controller (not shown), or an accelerator pedal (not shown)). For example, the command torque is determined based on the accelerator pedal position and the vehicle speed. In other words, the command torque refers to the torque required by the drive motor 13 according to the driver's operation. In this case, the free vibration compensation torque calculated by the free vibration compensation torque calculation unit 100 is derived based on a signal after removing the forced vibration component. Therefore, the free vibration compensation torque does not interfere with the forced vibration reduction compensation torque.

[0052] The control system 1 for reducing vibration of the drive shaft of an environmentally friendly vehicle according to an embodiment of the present disclosure prevents interference between the free vibration compensation torque for reducing free vibration and the forced vibration compensation torque for reducing forced vibration. Therefore, the control system 1 prevents a decrease in the control performance for vibration compensation.

[0053] Figure 3 A block diagram illustrating the drive shaft speed extraction unit according to an embodiment of the present disclosure.

[0054] Reference Figure 2 and Figure 3 The drive shaft speed extraction unit 110 includes a filtering unit 111, an amplitude compensation unit 113, and a forced vibration removal unit 115.

[0055] The filtering unit 111 extracts the forced vibration component from the actual speed of the drive shaft measured by the drive shaft speed sensor 51 based on the forced vibration frequency. The forced vibration frequency is determined based on the speed of the engine shaft and is used as the cutoff frequency of the filtering unit 111. The filtering unit 111 is configured by combining a low-pass filter and a high-pass filter, wherein the forced vibration frequency is set as the cutoff frequency. In other words, the filtering unit 111 is a bandpass filter used to extract only the forced vibration component. The low-pass filter and the high-pass filter are designed not to change the phase of the actual speed of the drive shaft. For example, the low-pass filter and the high-pass filter have the same order, which is a second-order filter in one example. When the signal of the actual speed of the drive shaft passes through the filtering unit 111, only the amplitude of the signal decreases while its phase remains unchanged.

[0056] The amplitude compensation unit 113 compensates for the reduction in the amplitude of the signal. In this case, the signal whose amplitude reduction must be compensated is the forced vibration component signal through the filter unit 111.

[0057] The forced vibration removal unit 115 removes the forced vibration component signal with compensated amplitude from the actual speed of the drive shaft. The value obtained by subtracting the compensated forced vibration component signal from the actual speed of the drive shaft is defined as the drive shaft speed.

[0058] According to the embodiment of this disclosure, the drive shaft speed extraction unit 110 calculates the speed of the drive shaft by subtracting the forced vibration component from the actual speed of the drive shaft. Therefore, the forced vibration component does not need to be considered in the calculation of the free vibration reduction torque used to compensate for free vibration. Therefore, the calculated free vibration reduction torque does not interfere with the forced vibration reduction torque.

[0059] According to an embodiment of the present disclosure, the drive shaft speed extraction unit 110 removes the forced vibration component from the actual speed of the drive shaft by using the forced vibration frequency calculated from the forced vibration signal measured in order to calculate the torque reduction due to forced vibration.

[0060] Figure 4 A block diagram illustrating the model velocity calculation unit according to an embodiment of the present disclosure.

[0061] Reference Figure 2 and Figure 4 The model speed calculation unit 120 includes a drive shaft output required torque calculation unit 121, a drive shaft input torque estimation unit 123, an interference torque calculation unit 125, and a speed calculation unit 127.

[0062] The drive shaft output torque calculation unit 121 calculates the drive shaft output torque T based on the torque transmitted to the drive shaft. net' The drive shaft output requires torque T. net'Based on the torque required by the drive motor 13, engine 11, starter generator 15, and braking system (not shown) and the vehicle load torque T load To calculate. The required output torque T of the drive shaft. net' It is the torque T required from the vehicle's torque source to apply torque to the drive shaft. bake Subtract vehicle load torque T load The resulting value. The vehicle's torque source is the drive motor 13, engine 11, starter-generator 15, or braking system. For example, the load torque T... load Similarly, the torque T required by the braking system brake It is a negative torque. Therefore, the drive shaft output requires a torque T. net' Use the following equation to calculate.

[0063] T net′ =T1+T2+T3-(T brake +T load )

[0064] Here, the torque T1 required by drive motor 13 is the torque command value of drive motor 13. The torques T2, T3, and T4 required by engine 11, starter engine 15, and braking system, respectively, are... brake All torque values ​​are derived by converting them into the torque of the shaft of the drive motor MG1.

[0065] In this case, the torques T2 and T3 required by the engine 11 and starter-generator 15, respectively, are obtained by converting the values ​​of the engine torque command and starter-generator torque command into the torque of the drive motor MG1 shaft. The torque T required by the braking system... brake It is a value derived by converting it into the braking torque that needs to be generated by the braking system of the drive wheels.

[0066] The drive shaft input torque estimation unit 123 uses the measured actual speed of the drive shaft to estimate the drive shaft input torque T. acc' When the actual drive shaft input torque T is... acc When applied to the drive shaft, the drive shaft rotates. When the transfer function of the drive shaft is defined as G(s), the actual speed ω of the drive shaft and the input torque Tacc of the drive shaft are expressed by the following equations.

[0067] ω=G(s)×T acc

[0068] T acc =ω / G(s)

[0069] In the above equation, G(s) is the transfer function of the actual drive shaft. When this transfer function is defined as the transfer function of the ideal drive shaft model being modeled, i.e., the transfer function Gm(s) of the drive shaft model designed to calculate the ideal model velocity ω that ignores vibration, Gm(s) is used instead of G(s) in the above equation to estimate the drive shaft input torque T. acc' .

[0070] According to this disclosure, when it is assumed that the drive shaft is a rigid body and the estimated value of the drive shaft input torque is defined as T acc' At that time, the estimated value of the input torque of the drive shaft is expressed by the following equation.

[0071]

[0072] In the above equation, Jm is the moment of inertia of the drive shaft, which is a rigid body. The estimated value T of the drive shaft input torque applied to the drive shaft is calculated from the actual speed ω of the drive shaft. acc' In the transfer function Gm(s), the order of the numerator is higher than that of the denominator. Mathematically, a system applying the transfer function Gm(s) has a structure susceptible to noise components from the actual velocity of the drive shaft. This is because the actual velocity of the drive shaft is differentiated and multiplied by the moment of inertia during calculation. Therefore, by applying a filter Q, the numerator and denominator can have the same order. According to embodiments of this disclosure, when using a first-order low-pass filter or LPF, the drive shaft input torque T is estimated using the following equation. acc' .

[0073] T acc =Q(s)×ω / Gm(s)

[0074] Where Q(s) = 1 / (τs+1)

[0075] In the above equation, Q(s) is the transfer function of the low-pass filter. The time constant τ of the low-pass filter Q is set to be greater than the frequency of the vibration component to be attenuated. Therefore, the torque estimated by the vibration component is removed. According to this disclosure, the transfer function Q(s) of the filter is set such that the order of the numerator of Q(s) / Gm(s) is always equal to or lower than the order of the denominator. By additionally applying such a filter, the estimated value T of the drive shaft input torque used to calculate from the actual speed ω of the drive shaft is optimized. acc' The order of the numerator of the transfer function Q(s) / Gm(s) is always equal to or lower than the order of the denominator. Therefore, stability against noise components is guaranteed.

[0076] Interference torque calculation unit 125 is based on the required output torque T of the drive shaft. net' and drive shaft input torque T acc'Calculate the disturbance torque estimate d'. The disturbance torque estimate d' is defined as the drive shaft output required torque T calculated in the drive shaft output required torque calculation unit 121. net' The drive shaft input torque T calculated in the drive shaft input torque estimation unit 123 acc' The difference between them. And the required torque T for the drive shaft output. net' The same filter Q used in the previous processing is applied to the calculation of the disturbance torque estimate d'. Therefore, the phase delay and amplitude change caused by the filter will also appear in the required torque output of the drive shaft. The required torque output of the drive shaft, low-pass filtered by filter Q, is used to calculate the disturbance torque estimate d'.

[0077] According to embodiments of this disclosure, when using a first-order low-pass filter, the interference torque estimate d' is estimated using the following equation.

[0078]

[0079] As described above, when estimating the disturbance torque estimate d', the speed calculation unit 127 uses the estimated disturbance torque estimate d' and the required output torque T of the drive shaft. net' Calculate the input torque T of the drive shaft model used for model velocity calculation. m The speed calculation unit 127 uses the estimated disturbance torque estimate d' to calculate the ratio of the disturbance torque estimate d' to the required output torque T of the drive shaft. net' The input torque T of the drive shaft model obtained by summing them up m In this case, the drive shaft model input torque T used for model speed calculation is... m The calculation equation is expressed by the following equation.

[0080] T m =T net′ +d′

[0081] Speed ​​calculation unit 127 uses the drive shaft model to input torque T m The drive shaft model is set as the input to calculate the model speed ω, as described above, when calculating the input torque T of the drive shaft model. m At that time, the speed calculation unit 127 calculates the model speed ω. In this case, the torque T is input from the drive shaft model using the transfer function Gm(s) of the drive shaft model according to the following equation. m Calculate the model velocity ω.

[0082]

[0083] Figure 5This is a flowchart illustrating a control method for reducing the drive shaft size of an environmentally friendly vehicle according to an embodiment of this disclosure. For brevity, descriptions repeated above will be omitted.

[0084] Reference Figure 5 The drive shaft speed extraction unit extracts the actual speed of the drive shaft and removes the forced vibration component from it. The actual speed of the drive shaft after removing the forced vibration component is defined as the drive shaft speed. In this case, a bandpass filter is applied to the drive shaft speed extraction unit to remove the forced vibration component. The bandpass filter is designed as a combination of a low-pass filter and a high-pass filter or HPF of the same order. The bandpass filter has a cutoff frequency, which is determined by the forced vibration signal extracted based on the engine shaft speed. In other words, the cutoff frequency is the frequency of the forced vibration signal (S110).

[0085] To extract the free vibration component from only the drive shaft speed signal, the model speed calculation unit calculates a model speed, excluding the vibration component, as the virtual drive shaft speed. The vehicle signal includes at least one of the vehicle speed, the value of the accelerator pedal position sensor (APS), and the value of the brake pedal sensor (BPS). An ideal model of the drive shaft is used, i.e., a model capable of calculating an ideal drive shaft speed (model speed) that ignores vibration, in order to extract the free vibration component of the drive shaft. The model speed, excluding the free vibration component, is calculated using the designed model (S120).

[0086] The free vibration calculation unit uses the difference between the calculated model velocity and the drive shaft velocity to calculate the free vibration component. The free vibration calculation unit applies an error cancellation controller, such as a high-pass filter, to the difference between the drive shaft velocity and the model velocity to calculate the free vibration component (S130).

[0087] The first torque calculation unit calculates the reverse phase signal of the free vibration component. The first torque calculation unit calculates the free vibration reduction compensation torque by multiplying the reverse phase signal of the free vibration component by the reference torque. The free vibration reduction compensation torque is the value of the command torque required by the unloaded vehicle (S140).

[0088] The forced vibration extraction unit extracts the forced vibration signal based on the speed of the engine shaft (S210).

[0089] The reference signal generation unit generates a reference signal based on the rotation angle of the motor (S220).

[0090] The phase determination unit synchronizes the phases of the reference signal and the forced vibration signal. The phase determination unit also detects the phase difference between the reference signal and the forced vibration signal. The phase determination unit detects a compensation value to compensate for the phase difference caused by the transmission delay from the forced vibration extraction unit to the drive motor, and detects a compensation value to compensate for the phase delay generated by the forced vibration extraction unit. Based on the phase difference and the compensation value, the phase determination unit generates a synchronization signal (S230 and S240) that is synchronized with the forced vibration signal extracted by the forced vibration extraction unit.

[0091] The second torque calculation unit generates a reverse phase signal using the phase generated by the reference signal generation unit, the phase difference between the reference signal and the forced vibration signal detected by the phase determination unit, and the compensation value detected by the phase determination unit. The second torque calculation unit calculates the forced vibration reduction compensation torque by multiplying the generated reverse phase signal by the reference torque (S250).

[0092] The motor controller generates a composite torque, which is the value obtained by adding the free vibration reduction compensation torque to the forced vibration reduction compensation torque. The motor controller calculates the input torque applied to the motor by adding the command torque to the composite torque; this command torque is the torque required to drive the vehicle. The command torque is a value that changes in real time based on the accelerator pedal position and the vehicle speed (S300).

[0093] According to the control method for reducing drive shaft vibration in environmentally friendly vehicles according to embodiments of this disclosure, the calculation for reducing free vibration is performed based on the speed of the drive shaft after removing the forced vibration component. Therefore, the final derived free vibration reduction compensation torque does not interfere with the forced vibration reduction compensation torque derived through a separate calculation process. In summary, the control method for reducing drive shaft vibration in environmentally friendly vehicles improves the performance of control for reducing motor vibration.

[0094] Figure 6 A graph illustrating the application effect of a control system for reducing the drive shaft of an environmentally friendly vehicle according to an embodiment of this disclosure.

[0095] Reference Figure 2 and Figure 6The free vibration reduction torque calculated by the free vibration compensation torque calculation unit 100 and the forced vibration reduction torque calculated by the forced vibration compensation torque calculation unit 200 have different frequencies and amplitudes. However, by observing the phases of the free vibration reduction torque and the forced vibration reduction torque, it can be seen that the peak times of the free vibration reduction torque and the forced vibration reduction torque are close to each other. In other words, the free vibration reduction torque and the forced vibration reduction torque do not interfere with each other. Therefore, the amplitude of the composite torque, which is the sum of the free vibration reduction torque and the forced vibration reduction torque, is greater than the amplitude of the forced vibration reduction torque. When the free vibration reduction torque and the forced vibration reduction torque interfere with each other, the amplitude of the composite torque is lower than the amplitude of the forced vibration reduction torque.

[0096] According to embodiments of this disclosure, interference between the free vibration reduction torque and the forced vibration reduction torque is prevented, thus the amplitude of the forced vibration of the drive shaft can be reduced by about 20%.

[0097] Embodiments of this disclosure have been described above with reference to the accompanying drawings. It will be apparent to those skilled in the art that this disclosure can be implemented in other ways without altering its technical concept and key features. Therefore, it should be understood that the various aspects of the embodiments described above are exemplary and not restrictive.

Claims

1. A control system for reducing drive shaft vibration in environmentally friendly vehicles, comprising: The drive shaft speed extraction unit extracts the actual speed of the drive shaft of the drive motor, and also extracts the drive shaft speed after removing the forced vibration component transmitted from the engine to the drive shaft. The model speed calculation unit calculates the model speed of the drive shaft; The free vibration calculation unit calculates the free vibration components based on the deviation between the drive shaft speed and the calculated model speed; as well as The first torque calculation unit calculates the free vibration reduction compensation torque from the free vibration components to reduce the vibration of the drive shaft. in, The drive shaft speed extraction unit extracts the drive shaft speed after removing the forced vibration component based on the forced vibration frequency, which is derived from the engine shaft speed.

2. The control system according to claim 1, wherein, The forced vibration frequency is the vibration frequency of the engine, and the forced vibration frequency is calculated based on the number of cylinders of the engine and the engine speed.

3. The control system according to claim 1, wherein, The drive shaft speed extraction unit includes: The filtering unit extracts the forced vibration component from the actual speed of the drive shaft based on the forced vibration frequency; An amplitude compensation unit compensates for the amplitude of the forced vibration component; and The forced vibration removal unit calculates the speed of the drive shaft, which is a value obtained by subtracting the forced vibration component that compensates for the amplitude from the actual speed of the drive shaft.

4. The control system according to claim 3, wherein, The filtering unit is configured with a combination of a low-pass filter and a high-pass filter that sets the forced vibration frequency as the cutoff frequency.

5. The control system according to claim 4, wherein, The low-pass filter and the high-pass filter are designed to not change the phase of the actual speed of the drive shaft.

6. The control system according to claim 1, wherein, The model velocity calculation unit includes: The drive shaft output required torque calculation unit calculates the drive shaft output required torque based on the torque transmitted to the drive shaft; A drive shaft input torque estimation unit estimates the drive shaft input torque input to the drive shaft using the actual speed of the drive shaft. The interference torque calculation unit estimates the interference torque using the required output torque of the drive shaft and the input torque of the drive shaft; and The speed calculation unit uses the estimated disturbance torque to calculate the drive shaft model input torque obtained by adding the disturbance torque to the required output torque of the drive shaft, and uses the drive shaft model to calculate the model speed, in which the drive shaft input torque is set as the input.

7. The control system according to claim 1, wherein, The model velocity refers to the ideal drive shaft velocity excluding the free vibration component, and The value obtained by subtracting the model speed from the drive shaft speed refers to the free vibration component after removing the forced vibration component.

8. A control method for reducing drive shaft vibration in environmentally friendly vehicles, comprising: Extract the actual speed of the drive shaft of the drive motor; Remove the forced vibration component transmitted from the engine to the drive shaft from the actual speed of the drive shaft; Calculate the model velocity of the drive shaft; The free vibration component is calculated based on the deviation between the drive shaft speed after removing the forced vibration component and the calculated model speed; as well as The free vibration reduction compensation torque for reducing the vibration of the drive shaft is calculated from the free vibration components. in, Removing the forced vibration component from the actual speed of the drive shaft includes: The actual speed of the drive shaft is extracted by filtering the forced vibration frequency to remove the forced vibration component. The forced vibration frequency is derived based on the speed of the engine shaft.

9. The control method according to claim 8, wherein, Removing the forced vibration component from the actual speed of the drive shaft includes: The forced vibration frequency is set to the cutoff frequency, and the forced vibration component is extracted from the actual speed of the drive shaft; Compensation for the amplitude of the forced vibration component; and The drive shaft speed is calculated by subtracting the forced vibration component that compensates for the amplitude from the actual speed of the drive shaft.

10. The control method according to claim 8, wherein, The model velocity refers to the ideal drive shaft velocity excluding the free vibration component, and The value obtained by subtracting the model speed from the drive shaft speed is the free vibration component after removing the forced vibration component.

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