Driving force control device

Abstract

To provide a driving force control device that can suppress resonance of a vehicle in a state where a motor is driven.SOLUTION: A driving force control device, which determines whether or not resonance occurs in a vehicle on a running path on the basis of the rotation speed of a motor mounted on the vehicle and restricts torque of the motor when determining that resonance occurs in the vehicle, is configured to: extract only a fluctuation component of the rotation speed from the rotation speed of the motor, using a band-pass filter; and when restricting torque of the motor, start torque-down at a timing of 270 degrees in a phase of a waveform in which the extracted fluctuation component is regarded as a COS waveform.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a driving force control device.

Background Art

[0002] Patent Document 1 discloses a driving force control device that determines whether resonance occurs in a vehicle body based on a change amount of a motor rotation speed, and restricts motor torque when it is determined that resonance occurs in the vehicle body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration described in Patent Document 1, a resonance counter is added when the change amount of the motor rotation speed is large, and the motor torque is restricted when the resonance counter value exceeds a predetermined value. When the timing for starting torque restriction is based on the resonance counter, the phase of rotational fluctuation is not considered, so there is a possibility that resonance cannot be suppressed depending on the timing.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a driving force control device capable of suppressing resonance of a vehicle in a state where a motor is driving.

Means for Solving the Problems

[0006] The present invention relates to a drive force control device that determines whether resonance occurs in a vehicle with respect to a road surface based on the rotational speed of a motor mounted on the vehicle, and limits the torque of the motor when it is determined that resonance occurs in the vehicle, characterized in that, when limiting the torque of the motor, only the rotational speed fluctuation component is extracted from the rotational speed of the motor using a bandpass filter, and the torque reduction is started at a timing of 270 degrees in the phase of the waveform obtained by considering the extracted fluctuation component as a COS waveform.

[0007] In this configuration, when the motor is running, the timing at which the motor torque reduction begins is controlled based on the phase of the waveform, which is obtained by considering the fluctuation component of the motor rotation speed as a cosine (COS) waveform. This makes it possible to suppress resonance in the vehicle.

[0008] Furthermore, if the timing at which resonance is determined to occur in the vehicle is such that the phase of the waveform obtained by considering the fluctuating component as a COS waveform is 0 degrees or greater and less than 270 degrees, the torque reduction may be started at the timing when the phase becomes 270 degrees.

[0009] With this configuration, the timing of the torque reduction initiation is at a phase that is effective in suppressing torsional vibrations of the rotating members, thus suppressing resonance in the vehicle.

[0010] Furthermore, the present invention relates to a drive force control device that determines whether resonance occurs in a vehicle with respect to a road surface based on the rotational speed of a motor mounted on the vehicle, and limits the torque of the motor when it is determined that resonance occurs in the vehicle, wherein the device extracts only the rotational speed fluctuation component from the rotational speed of the motor using a bandpass filter, and when limiting the torque of the motor, controls the timing of starting the torque reduction based on the phase of the waveform obtained by considering the extracted fluctuation component as a COS waveform, and if the timing at which it is determined that resonance occurs in the vehicle is between 270 degrees and 360 degrees in phase of the waveform obtained by considering the fluctuation component as a COS waveform, it immediately starts the torque reduction.

[0011] With this configuration, vehicle resonance can be suppressed by immediately reducing torque when the phase of the vibration is effective in suppressing torsional vibration of the rotating member. [Effects of the Invention]

[0012] In this invention, the timing at which the motor torque reduction begins is controlled based on the phase of a waveform in which the fluctuation component of the motor rotation speed is considered as a cosine (COS) waveform while the motor is running. This makes it possible to suppress resonance in the vehicle. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram illustrating a vehicle in an embodiment. [Figure 2] This diagram illustrates the waveform, which considers the motor rotation speed fluctuation component as a cosine (COS) waveform, and the timing of the start of torque reduction. [Figure 3] This time chart illustrates the case where the timing of torque reduction is controlled by considering the phase of the waveform obtained by treating the motor rotation speed fluctuation component as a cosine waveform. [Figure 4] This is a magnified view of the area around the peak in the torque fluctuation of the drive shaft shown in Figure 3. [Figure 5] This diagram illustrates the timing of the start of torque reduction. [Figure 6] This time chart illustrates the case where the timing of torque reduction is controlled by considering the phase of the waveform obtained by treating the motor rotation speed fluctuation component as a cosine waveform. [Figure 7] This is a magnified view of the area around the peak in the torque fluctuation of the drive shaft shown in Figure 6. [Figure 8] This time chart illustrates the case where the timing of torque reduction is controlled by considering the phase of the waveform obtained by treating the motor rotation speed fluctuation component as a cosine waveform. [Figure 9]It is a diagram showing an enlarged view of the vicinity of the peak in the torque fluctuation of the drive shaft in FIG. 8.

Mode for Carrying Out the Invention

[0014] Hereinafter, the drive force control device in the embodiment of the present invention will be specifically described. Note that the present invention is not limited to the embodiments described below.

[0015] FIG. 1 is a schematic diagram for explaining a vehicle in the embodiment. The vehicle 1 includes a motor 2, a transmission 3, a drive shaft 4, wheels 5, and a control device 10.

[0016] The vehicle 1 is an electric vehicle having the motor 2 as a power source. The motor 2 is a motor for traveling and is driven by electric power supplied from a battery mounted on the vehicle 1. When the motor 2 is driven, the power of the motor 2 is transmitted to the transmission 3. The transmission 3 is a power transmission mechanism provided between the motor 2 and the drive shaft 4. The drive shaft 4 is connected to the wheels 5 so as to be capable of power transmission. In the vehicle 1, the power output from the motor 2 is transmitted to the wheels 5 via the transmission 3 and the drive shaft 4. Further, when the motor 2 is rotated by an external force input from the wheels 5, the motor 2 functions as a generator. The motor 2 is a motor generator (MG) that can function as both an electric motor and a generator.

[0017] The control device 10 is an electronic control device that controls the motor 2. The control device 10 is composed of a control unit and a memory unit. The control device 10 receives a signal from the motor rotation speed sensor 20. The motor rotation speed sensor 20 is a sensor that detects the rotation speed of the motor 2 (hereinafter referred to as motor rotation speed). The motor rotation speed sensor 20 detects the rotation speed of a rotating member that rotates integrally with the rotor shaft of the motor 2 and outputs the detection signal to the control device 10. For example, the motor rotation speed sensor 20 is provided on the rotating shaft that connects the motor 2 and the transmission 3. Based on the signal input from the motor rotation speed sensor 20, the control device 10 detects the motor rotation speed and controls the torque of the motor 2 (hereinafter referred to as motor torque).

[0018] Furthermore, the control device 10 includes a bandpass filter (BPF) 11. The bandpass filter 11 is a filter circuit that allows signals in a specific frequency band to pass through. The control device 10 uses the bandpass filter 11 to extract the resonant frequency fluctuation component from the motor rotation speed. In the control device 10, the motor rotation speed sensor 20 signal is input to the bandpass filter 11, enabling the extraction of the rotation speed fluctuation component from the motor rotation speed. The control device 10 then controls the timing for initiating a torque reduction of the motor torque based on the motor rotation speed fluctuation component.

[0019] When the control device 10 detects that the vehicle 1 is running on a wavy road, it executes control to protect components by restricting the driving force (motor torque) of the motor 2. Specifically, the control device 10 determines whether resonance occurs in the vehicle 1 with respect to the traveling road based on the motor rotation speed. The control device 10 determines whether resonance occurs in the vehicle 1 by determining whether the fluctuation value of the motor rotation speed exceeds a threshold value. The threshold value is a preset value. When it is determined that resonance occurs in the vehicle 1, the control device 10 executes driving force control to restrict the driving force. In this driving force control, the control device 10 performs torque reduction of the motor torque in consideration of the phase of vibration. As a result, the peak value of the resonance torque can be reduced more effectively. Thus, the control device 10 is a driving force control device that controls the torque of the motor 2.

[0020] Specifically, the control device 10 extracts only the fluctuation component of the rotation speed from the motor rotation speed using the band-pass filter 11, and starts torque reduction at the timing when the waveform regarded as the COS waveform changes from the negative direction to the positive direction, that is, at the zero timing when the fluctuation value of the motor rotation speed in the COS waveform changes from a negative value to a positive value.

[0021] The timing of torque reduction refers to the timing when torque actually occurs from the motor 2. In the vehicle 1, when communication delay or calculation delay between ECUs and phase delay due to the band-pass filter 11 occur, the control device 10 outputs a torque command in consideration of that wasted time in advance.

[0022] As shown in Figure 2, in the waveform where the motor rotation speed fluctuation component (rotational fluctuation of MG rotation speed) is considered as a COS waveform, the waveform changes from negative to positive at the timing when the phase is 270 degrees. The control device 10 sets this timing when the phase is 270 degrees as the optimal timing to start torque reduction of the motor torque. If torque reduction of the motor torque were to start at the timing when the phase is 90 degrees, the torque reduction would be stepped in at the timing that excites torsional vibration, which would have the opposite effect of resonance suppression. On the other hand, if torque reduction of the motor torque is started at the timing when the phase is 270 degrees, torsional vibration can be suppressed.

[0023] Therefore, if the control device 10 determines that resonance is occurring in the vehicle 1, it starts reducing the motor torque at the timing when the phase of the waveform, which is calculated by considering the fluctuating component of the motor rotation speed as a COS waveform, becomes 270 degrees. As shown in Figure 2, at time t10, the phase of the waveform, which is calculated by considering the fluctuating component of the motor rotation speed as a COS waveform, becomes 270 degrees, so the control device 10 starts reducing the motor torque at this timing. This 270-degree phase is an effective phase for suppressing torsional vibration, and thus resonance can be suppressed.

[0024] Figure 3 is a diagram illustrating the timing at which the motor torque reduction begins. Figure 3 shows the rotational speed of the wheel 5 (wheel speed), the motor rotational speed (MG rotational speed), the fluctuation component of the motor rotational speed (rotational fluctuation of MG rotational speed), the motor torque (MG torque), and the torque fluctuation of the drive shaft 4. The graph of the rotational fluctuation of the MG rotational speed shows the motor rotational speed extracted using a bandpass filter 11 at the resonant frequency. Figure 3 also shows a comparative example where torque reduction is performed by threshold determination only, without considering phase, as indicated by the dashed lines in the graphs of MG torque and drive shaft 4 torque fluctuation. Embodiments of the control device 10 are shown by the solid lines in the graphs of MG torque and drive shaft 4 torque fluctuation.

[0025] As shown in Figure 3, from time t1 onward, when the motor torque begins to increase in response to the acceleration request, torsional vibration occurs in the drive shaft 4 as the vehicle 1 travels on the wavy road, causing rotational fluctuations in the motor rotation speed. When the control device 10 determines that resonance is occurring in the vehicle 1, it starts to reduce the motor torque at a timing where the phase of the fluctuation component of the motor rotation speed, considered as a COS waveform, is 270 degrees (time t10). On the other hand, in the comparative example, the reduction in motor torque starts at time t2, which is earlier than time t10. Time t2 is the timing when the waveform, considered as a COS waveform of the fluctuation component of the motor rotation speed, changes from positive to negative, that is, the timing just before zero when the fluctuation value of the motor rotation speed in the COS waveform changes from a positive value to a negative value.

[0026] Furthermore, comparing the control by the control device 10 (Example) with the control by the comparative example (Comparative Example), as shown in Figure 4, the Example can reduce the peak torque of the drive shaft 4 by 5 to 10% compared to the Comparative Example.

[0027] Furthermore, as shown in Figure 5, the control device 10 immediately performs torque reduction even if the optimal timing for starting torque reduction has passed, as long as the fluctuation value of the motor rotation speed does not reach a positive peak value. If it has passed any other positive peak value, it starts torque reduction at the timing when the fluctuation value changes from a negative value to a positive value next, which is zero.

[0028] If the control device 10 determines that resonance occurs in the vehicle 1, and this timing falls within a period when the phase of the waveform, which is calculated by considering the motor rotation speed fluctuation component as a COS waveform, is 0 degrees or greater and less than 270 degrees, the control device 10 will start torque reduction when the phase reaches 270 degrees. If the timing that causes resonance in the vehicle 1 is determined falls within a period when the phase is 0 degrees or greater and less than 270 degrees, the control device 10 will wait until the phase reaches 270 degrees before starting torque reduction. This results in a phase that is effective in suppressing torsional vibration of the drive shaft 4, thereby suppressing resonance in the vehicle 1.

[0029] As shown in Figure 6, in the comparative example, the motor torque was reduced at various timings during the period when the phase was greater than or equal to 0 degrees and less than 270 degrees. On the other hand, the control device 10 determined that resonance occurred in the vehicle 1 during the period when the phase was greater than or equal to 0 degrees and less than 270 degrees, and started the torque reduction at the next 270-degree timing. As a result, as shown in Figure 7, the peak value was lowest when the torque reduction was started after waiting until the 270-degree timing (example) compared to when the torque reduction was started immediately during the period when the phase was greater than or equal to 0 degrees and less than 270 degrees (comparative example).

[0030] Furthermore, if the control device 10 determines that resonance occurs in the vehicle 1, and the timing falls within a period when the phase of the waveform, which is calculated by considering the fluctuating component of the motor rotation speed as a cosine waveform, is 270 degrees or more and less than 360 degrees, the control device 10 immediately starts torque reduction. The control device 10 controls the timing at which it starts torque reduction of the motor torque based on the phase of the waveform, which is calculated by considering the fluctuating component of the motor rotation speed as a cosine waveform, while the motor 2 is in operation.

[0031] The control device 10 immediately starts torque reduction if the timing at which resonance is determined to occur in the vehicle 1 falls within a period in which the phase of the waveform, which considers the motor rotation speed fluctuation component as a COS waveform, is 270 degrees or more and less than 360 degrees. The control device 10 immediately starts torque reduction if the timing at which resonance is determined to occur in the vehicle 1 falls within a period in which the phase is 270 degrees or more and less than 360 degrees. If the phase is 270 degrees or more and less than 360 degrees, it is better to immediately reduce the torque rather than waiting for the next 270 degrees. After that, it waits until the next 270 degrees before starting the torque reduction. This makes it possible to lower the peak torque of the drive shaft 4 and effectively suppress torsional vibration, thereby suppressing resonance in the vehicle 1.

[0032] As shown in Figure 8, the control device 10 immediately initiated a torque reduction of the motor torque at three timings during a period when the phase was between 270 degrees and less than 360 degrees. As a result, as shown in Figure 9, when the immediate torque reduction was initiated within a period when the phase was between 270 degrees and less than 360 degrees (Examples 1-3), the peak value was kept low.

[0033] As described above, according to the embodiment, the peak value of the resonant torque can be suppressed more effectively by implementing torque limiting while considering the phase of vibration.

[0034] Vehicle 1 may be any electric vehicle equipped with a motor 2 as a power source, and may be a battery electric vehicle (BEV) or a hybrid electric vehicle (HEV). [Explanation of Symbols]

[0035] 1 vehicle 2 motors 3. Transmission 4 drive shafts 5 wheels 10 Control device 11 Bandpass filter 20 Motor rotation speed sensor

Claims

1. A drive force control device that determines whether resonance occurs in the vehicle with respect to the road surface based on the rotational speed of the motor mounted on the vehicle, and limits the torque of the motor if it is determined that resonance occurs in the vehicle, The rotational speed fluctuation component of the aforementioned motor is extracted using a bandpass filter. When limiting the torque of the motor, the torque reduction is initiated at a timing of 270 degrees in the phase of the waveform obtained by considering the extracted fluctuating component as the COS waveform. If the timing at which resonance is determined to occur in the vehicle is such that the phase of the waveform, when the fluctuating component is considered as a COS waveform, is 0 degrees or greater and less than 270 degrees, then torque reduction will be initiated at the timing when the phase reaches 270 degrees. A drive force control device characterized by the following:

2. A drive force control device that determines whether resonance occurs in the vehicle with respect to the road surface based on the rotational speed of the motor mounted on the vehicle, and limits the torque of the motor if it is determined that resonance occurs in the vehicle, The rotational speed fluctuation component of the aforementioned motor is extracted using a bandpass filter. When limiting the torque of the motor, the timing at which the torque reduction begins is controlled based on the phase of the waveform obtained by considering the extracted fluctuating component as a COS waveform. If the timing at which resonance is determined to occur in the vehicle is such that the phase of the waveform, when the fluctuating component is considered as a COS waveform, is 270 degrees or more and less than 360 degrees, then torque reduction will be initiated immediately. A drive force control device characterized by the following:

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