KR101337903B1 - Motor control method for decreasing vibration during operation of anti-lock brake system - Google Patents

Abstract

The present invention relates to a motor control method for reducing vibration during ABS operation, in which an electric vehicle employing a drive system composed of a direct connection structure of a motor-reduction gear-drive shaft-wheel rapidly attenuates the torsional vibration of the drive system during ABS operation. The purpose of the present invention is to provide a motor control method that can improve the time and reliability of electric vehicles while solving abnormal operation problems. In order to achieve the above object, when the ABS operation signal indicating the ABS operation in the electric vehicle is detected, the vibration damping torque value of the braking direction in the reverse direction of the motor rotation direction is calculated, and the ABS according to the calculated vibration damping torque value Disclosed is a motor control method for driving system vibration reduction during ABS operation, wherein a torque for vibration damping is applied to the motor during operation.

Description

Motor control method for reducing vibration during operation of ACS {Motor control method for decreasing vibration during operation of anti-lock brake system}

The present invention relates to a motor control method of an electric vehicle, and more particularly, to a motor control method capable of rapidly attenuating torsional vibration during ABS operation in a drive system of an electric vehicle having a direct connection structure of a motor-reduction gear-drive shaft-wheel. It is about.

In general, in a hydraulic brake of a vehicle, braking hydraulic pressure is applied from the master cylinder by the operation of the brake pedal, and when the braking force is applied to the tire that is greater than the static friction force between the road surface and the tire, the tire slips on the road surface. This happens.

Since the motion friction coefficient is smaller than the static friction coefficient, in order to achieve the best braking, this slip phenomenon must be prevented, and the handle locking phenomenon that the handle control becomes impossible during brake operation must be prevented.

Therefore, ABS (Anti-lock Brake System) is used to control the braking hydraulic pressure applied by the hydraulic brake of each wheel and to secure a stable braking force. It consists of a hydraulic control device such as a plurality of solenoid valves, an accumulator and a hydraulic pump for controlling, and an ECU for controlling electrical elements.

This ABS senses the wheel slip caused by brake operation during braking or on slippery roads, thereby reducing, maintaining, or boosting braking hydraulic pressure to secure proper cornering force and maintain steering stability while stopping the vehicle in the shortest distance. Will be controlled.

Typically, the ABS is operated when the slip value of the wheel calculated on the basis of the wheel speed detected by the sensor and the body speed estimated from the wheel speed reaches a preset slip value.

On the other hand, in the case of an electric vehicle using a motor as a driving source, the application of ABS has been attempted similarly to an internal combustion engine vehicle (general engine vehicle).

However, in applying ABS to an electric vehicle, the following problems occur.

First, when braking in a low friction road, excessive vibration occurs in a drive system including a motor for driving a vehicle, and thus ABS may not operate normally.

The excessive vibration of the drive system is due to the friction and damping elements such as the engine, which is a power generator, the transmission, the clutch, and the torque converter, which are different from general engine cars. This is due to the lack of components.

To describe the detailed causal relationship in more detail, first, the drive system of the electric vehicle is directly connected to the motor 10-reducer 20-drive shaft 30-wheel 40 as shown in FIG. It is structured.

In Fig. 1, reference numeral 51 denotes a brake disc mounted on a wheel in a vehicle brake device, 52 denotes a caliper assembly of a hydraulic brake, 50 denotes ABS, 53 denotes an ABS ECU, and 54 denotes an ABS. Each hydraulic control device is shown.

In the drive system of the electric vehicle, the drive shaft 30 is a relatively long shaft, so that the torsional vibration can be easily generated, and the spring can be modeled.

In the structure of the drive system, when the brake is applied to the ABS 50 (ABS On), torsional vibration is generated in the drive system being rotated at a high speed.

The excitation factor at this time is the brake hydraulic braking torque of the drive system's natural frequency (or multiples thereof) and the motor regenerative braking torque that is removed at the moment of ABS operation (when ABS is operated, the control authority of the drive system is transferred to ABS. Regenerative braking is stopped).

Due to the torsional vibration, the speed of the wheel 10 (wheel speed) and the speed of the wheel 10 fluctuate rapidly, resulting in a speed difference between the driving wheel and the driven wheel (front wheel and rear wheel).

When the speed difference between the front wheel and the rear wheel occurs, the ABS 50 determines to slip and temporarily releases the brake. In this state, both the hydraulic braking and the regenerative braking do not operate even though the driver presses the brake pedal. At the start of operation, regenerative braking is not performed), so the vehicle just slides on the road.

This occurs regardless of road conditions, but for longer periods on low friction or rough roads, which results in longer braking distances, spin outs that prevent the vehicle from standing upright, skew to the left or right, or turn around. Phenomenon occurs.

The above-mentioned vibration occurrence problem also occurs in a general engine vehicle, but the torsional vibration of the drive system is attenuated in a short time by a sufficiently large friction force of the engine and the transmission and a damping element such as a clutch or a torque converter. Abnormal operation of ABS due to torsional vibration does not have a great effect on the quality in time.

On the other hand, electric vehicles have no engine, no transmission, and since the rotor of the motor has an air gap with the stator, the structure is floating in the air under bearing support, so there is little frictional force.

For this reason, the torsional vibration that occurs once in the electric vehicle is not easily attenuated, and the abnormal operation problem of ABS is a serious threat to the seriousness of the vehicle.

2 is a view showing a conventional problem, showing the vibration of the motor and the occurrence of ABS abnormal operation during the ABS operation while the driver stepped on the brake pedal in the low friction road.

In the abnormal operation section at the beginning of ABS operation, shock is transmitted to the motor by the wheel slip, and afterwards, excessive vibration of the motor / wheel occurs, which makes normal control of the ABS impossible.

Subsequently, when the vibration of the motor is reduced, the normal operation of the ABS is performed, but in order to solve the abnormal operation problem of the ABS in the electric vehicle, there is an urgent need for a method of rapidly attenuating the vibration of the drive system.

Accordingly, the present invention has been made to solve the above problems, in the electric vehicle employing a drive system consisting of a direct connection structure of a motor-reduction gear-drive shaft-wheel to quickly attenuate the torsional vibration of the drive system during ABS operation ABS abnormality The purpose is to provide a motor control method that can improve the timeliness and commerciality of electric vehicles while solving operational problems.

In order to achieve the above object, the present invention, when the ABS operation signal indicating the ABS operation is detected in the electric vehicle, calculates the vibration damping torque value of the braking direction in the reverse direction of the motor rotation direction, the calculated vibration damping torque According to the present invention, there is provided a motor control method for reducing vibration of a drive system during an ABS operation, wherein a vibration damping torque is applied to a motor during an ABS operation.

Here, when the vehicle controller receives the ABS operation signal from the ABS ECU, it calculates the vibration damping torque value, generates and outputs a corresponding motor torque command, and the motor controller passes through the inverter according to the motor torque command applied from the vehicle controller. It is characterized by controlling the motor torque.

In addition, the vibration damping torque is characterized in that it is determined by the sum of the active damping torque of the pulse form and the cost regenerative torque applied continuously.

In addition, the active damping torque is characterized in that the rotational acceleration of the motor is calculated from the change in the rotational speed of the motor detected by the speed detector is applied in the form of a pulse when the rotational acceleration of the motor exceeds a set reference value.

In addition, the pulse amplitude of the active damping torque is set to be determined by the value according to the motor rotational speed detected by the speed detector, wherein the pulse application time of the active damping torque is a predetermined time according to the natural vibration frequency of the drive system do.

The cost regenerative torque may be set to be determined according to a motor rotation speed detected by the speed detector and a shift lever position.

In addition, at the beginning of the transition from the regenerative braking operation state to the ABS operating state during vehicle braking, the cost regenerative torque is set so that the change rate according to the previous regenerative braking torque or cost regenerative torque value and the motor rotational speed is determined as an applied value. It features.

In addition, the cost regenerative torque is set so as to be determined as a larger value of the torque value to which the rate of change is applied during the ABS operation, and the torque value according to the motor rotation speed and the shift lever position.

Accordingly, in the motor control method of the electric vehicle according to the present invention, by applying the vibration damping motor torque in the braking direction during ABS operation, it is possible to quickly attenuate the torsional vibration generated in the drive system, and solve the abnormal operation problem of the ABS. This will improve the vehicle's timeliness and marketability.

1 is a configuration diagram schematically showing a drive system of an electric vehicle.
2 is a view showing a conventional problem.
3 is a block diagram of a control system for performing a motor control process according to the present invention.
4 is a diagram schematically showing an example of vibration damping torque in a motor control process according to the present invention.
5 is an exemplary view for explaining the application timing determination and torque value calculation of the active damping torque in the present invention.
6 is a diagram illustrating cost regenerative torque in the present invention.
7 is a diagram illustrating that the torque command is determined by the sum of the active damping torque and the cost regenerative torque in the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be easily understood by those skilled in the art.

The present invention relates to a motor control method capable of rapidly attenuating torsional vibration of a drive system during ABS operation in an electric vehicle employing a drive system having a direct connection structure of a motor-reduction gear-drive shaft-wheel.

3 is a block diagram of a control system for performing a motor control process according to the present invention.

First, the motor control method of the present invention is a motor control method which is applied during ABS operation in which a torsional vibration may occur in a drive system of an electric vehicle in the absence of physical friction and damping elements, which may occur during the operation of a driver's brake pedal. The main feature is that the motor torque for rapid vibration attenuation based on the rotational speed of the municipal motor 10 is applied.

In a typical motor torque control process of an electric vehicle, the vehicle controller (VCU) 60 generates and outputs a torque command so that the required motor torque output is made based on various information collected while driving, and thus the motor controller (MCU; 71). According to the motor torque command of the vehicle controller 61, the motor torque through the inverter 70 is controlled (three-phase current control) to generate the required torque.

The motor control process for vibration attenuation of the present invention is also performed by cooperative control between an upper controller and a lower controller. The motor control process for vibration attenuation is started from the vehicle controller detecting the ABS operation signal.

That is, when the ABS ECU 54 determines that the ABS operation condition is in accordance with normal logic to start ABS operation and outputs a signal (ABS operation signal) indicating that the ABS is activated (ABS On), the ABS ECU ( The vehicle controller 60 receives the signal of 54 to start the motor control process for vibration attenuation.

At this time, when the vehicle controller 60 receives a signal from the ABS ECU 54, the vehicle controller 60 calculates a vibration attenuation torque value, generates and outputs a corresponding motor torque command, and the motor controller 71 outputs the vehicle controller 60 from the vehicle controller 60. The motor torque is controlled through the inverter 70 according to the applied motor torque command.

Referring to FIG. 3, a drive system of an electric vehicle having a direct connection structure of a motor 10, a speed reducer 20, a drive shaft 30, and a wheel as a vehicle driving source, an ABS ECU 54 outputting a signal during ABS operation, and ABS The motor controller 60 generates a motor torque command for vibration attenuation based on the rotational speed of the motor 10 during operation, and the motor performs motor torque application for vibration attenuation according to the motor torque command of the vehicle controller 60. Controller 71 is shown.

In addition, the battery 1, the inverter (INV) 70 that converts the DC power of the battery 1 into three-phase AC power and supplies the motor 10 to the motor 10, and the rotational speed of the motor 10. A speed detector 12 is shown for detecting.

The speed detection unit 12 may be a conventional resolver. In the present invention, the vehicle controller 60 vibrates a rotation speed of the motor 10 detected by the speed detection unit 12 during ABS operation. It is used to generate the torque command.

4 is a diagram schematically showing an example of vibration damping torque in a motor control process according to the present invention.

As shown in FIG. 4, when the driver presses the brake pedal (2 in FIG. 3), regenerative braking ('A' section) is performed according to the pedal input, and ABS operation is started by satisfying the ABS operating condition. The vehicle controller 60 then generates a motor torque command for vibration attenuation during ABS operation ('B' section).

Conventionally, after the brake pedal is pressed, regenerative braking (battery charging) is generated based on the pedal input value and the like, and the regenerative braking is stopped when the ABS is operated. In this case, the regenerative braking is performed by the motor. Torque vibrations are generated in the drive system as the torque is removed momentarily.

In order to solve this problem, in the present invention, when the ABS is operated to apply a motor torque for vibration attenuation to quickly attenuate the vibration of the drive system including the motor, in this case the motor for vibration reduction generated and output from the vehicle controller 60 The torque command is shown in the ABS operation section ('B' section) of FIG. 4.

As shown in FIG. 4, the motor torque is applied for vibration attenuation during the period in which the vehicle speed decreases from the point of time when the regenerative braking (the 'A' section of FIG. 4) is switched to the ABS operation (the 'B' section of FIG. 4). The controller 60 generates and outputs a torque command for vibration attenuation based on the rotational speed of the motor 10, and the motor controller 70 generates the motor torque for vibration attenuation according to the torque command of the vehicle controller 60. Will be authorized.

As the engine and the transmission reduce the vibration by using the friction force, the torque is generated in the vibrating motor 10 so as to quickly reduce the vibration.

In the present invention, the torque value for damping the drive system torsional vibration, that is, the motor torque command for vibration damping of the vehicle controller 60 may include an active damping torque applied in a pulse form and a cost regenerative torque applied continuously. It is determined by the sum of coast regen.torque. First, the active damping torque is explained as follows.

5 is an exemplary diagram for describing an application timing determination and torque value calculation of an active damping torque.

As shown in the drawing, the active damping torque is the vibration damping torque in the braking direction applied when the vibration occurs during the ABS operation. The vehicle controller 60 determines the timing of applying the active damping torque, calculates the active damping torque, and calculates the motor torque. It will be reflected in the order.

At this time, the vehicle controller 60 calculates the rotational acceleration a_mot (hereinafter abbreviated as motor acceleration) of the motor from the change in the rotation speed (hereinafter, abbreviated as motor speed) of the motor 10 detected by the speed detector 12. If the motor acceleration exceeds a preset threshold, the controller determines the time when the active damping torque is applied.

That is, the time point at which the active damping torque is applied is a point at which the motor acceleration> reference value (a_mot> Threshold), and the active damping torque in the form of pulse can be applied when the motor speed is rapidly increased or decreased above a certain level.

Here, when the shift lever position of the electric vehicle is the forward stage (for example, D / E / L stage) in consideration of brake hydraulic interference and intermittent fidelity, torque is applied at a positive acceleration (state in which the motor speed is increased). In the case of the reverse stage (R stage), torque is applied at a negative acceleration (a state in which the motor speed decreases).

In the process of calculating the active damping torque value, the amplitude and the duration should be determined because the torque is a pulse. The amplitude is the motor speed (or motor speed) which is a detection value of the speed detector as shown in Equation (1) below. Can be set as a function of vehicle speed calculated from

Amplitude = f (motor speed) (1)

In addition, the application time may be a value set in advance according to the natural vibration frequency of the drive system, or may be a value set through a prior test considering the communication speed between controllers, various amplitude conditions, etc. in addition to the natural vibration frequency.

In addition, the active damping torque for the purpose of vibration attenuation is torque in the braking direction, that is, reverse torque in the motor rotation direction, which is a negative direction torque when the shift lever position is forward, and a positive direction torque when reverse.

As such, the vibration damping torque includes the active damping torque component together with the regenerative braking torque (coast regenerative torque), and thus, may be referred to as a torque acting in a braking direction opposite to the motor rotation direction.

The information about the forward stage and the reverse stage is received and used by the vehicle controller from the transmission controller (not shown) (TCU) as in the normal case.

Next, FIG. 6 is a diagram illustrating cost regen torque. Referring to this, the cost regen torque will be described below.

Regenerative braking is performed during vehicle braking. When the ABS operation is started, the cost regenerative torque is applied, and as shown in FIGS. 4 and 6, the vehicle speed is reduced during the ABS operation to gradually reduce the cost regenerative torque.

That is, in the present invention, the regenerative braking torque is not instantaneously removed after ABS operation, but the control is gradually reduced.

In the present invention, the cost regenerative torque value may be set to be determined as a function of the motor speed (or vehicle speed calculated from the motor speed) which is a detection value of the speed detector.

At this time, the regenerative braking torque value before ABS operation is different according to the shift lever position, so the cost regenerative torque value also needs to be differentiated according to the shift lever position.

That is, the cost regenerative torque value differentiated according to the shift lever position should be calculated in consideration of the driving characteristics (separate torque applied for each D / E / L / R stage). Therefore, the cost regenerative torque value depends on the motor speed and the shift lever position. It is preferably set to determine the value.

In addition, when the cost regenerative torque is equally obtained and applied as a function of the motor speed in all sections of the ABS operation, in particular, the regenerative braking (the 'A' section in FIG. 4) to the ABS operation (the 'B' section in FIG. 4) After the conversion, a large torque step may occur in the initial section (initial of the 'B' section), which may cause an unexpected vibration.

There is a big difference in the magnitude of the regenerative braking torque determined according to the brake pedal input value and the vibration regenerative cost regenerative torque (resilient running regenerative braking torque for the purpose of damping vibration after ABS operation). If the regenerative braking torque is removed immediately after ABS operation and the cost regenerative torque is applied, vibration may occur in the motor due to the large torque step.

For example, if the regenerative braking torque is 500 Nm before the ABS operation, and the cost regenerative torque determined as a function of the motor speed immediately after the ABS operation (and by the shift lever position) is 50 Nm, the vibration may be caused by a sudden torque step at the time of ABS operation switching. This will occur.

Therefore, it is necessary to gradually reduce the torque by limiting the torque change rate in the initial section of the transition from regenerative braking to ABS operation, thereby reducing the torque step that may occur at the beginning of the conversion and minimizing the effect of vibration.

In the initial section, when ABS operation starts, the previous torque calculated value (regenerative braking torque value at the time of switching or the previously calculated cost regenerative torque value) and the motor speed (or vehicle speed calculated from the motor speed) are expressed as in Equation (2) below. Cost change torque is determined by applying the rate of change calculated as a function.

Rate of change = f (old torque calculated value, motor speed) (2)

In other words, according to the change rate reflecting the previous torque calculation value, the cost regenerative torque is smoothly reduced without step.

However, from the time when the torque value (cost regen torque value calculated by reflecting the change rate) reduced by the change rate reaches the torque value determined according to the motor speed and the shift lever position described above, the cost regenerative torque is smoothly without a large step. Since the state can be reduced, the cost regenerative torque according to the motor speed and the shift lever position is applied as it is.

At this time, in order that the change rate can be applied only at the beginning of the switching, when the ABS operation is started, a method of determining a larger value among the torque value determined according to the change rate and the torque value determined according to the motor speed and the shift lever position may be applied.

Through this, as shown in FIG. 6, the cost regenerative torque may be gradually reduced without a large step as the vehicle speed decreases during the ABS operation, and the vibration effect due to the torque step in the initial operation of the ABS may be minimized.

Thus, in the present invention, when the ABS operation is started, the torque for attenuating the torsional vibration of the drive system, i.e., the vibration damping torque determined by the sum of the active damping torque and the cost regenerative torque as shown in Figs. Applied to the motor.

As a result, in the present invention, by applying a torque for vibration attenuation to the motor during ABS operation in the electric vehicle having a drive system of the direct connection structure, it is possible to quickly attenuate the vibration, thereby solving the abnormal operation problem of the ABS at the same time In the meantime, it will be able to greatly improve the reliability and marketability.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. Modified forms are also included within the scope of the present invention.

10: motor 12: speed detection unit
20: reducer 30: drive shaft
50: ABS 54: ABS ECU
60: vehicle controller 70: inverter
71: motor controller

Claims (9)

When the ABS operation signal indicating the ABS operation is detected in the electric vehicle, the vibration damping torque value in the braking direction opposite to the motor rotation direction is calculated, and the vibration damping torque during the ABS operation is calculated according to the calculated vibration damping torque value. Licensed to,
The vibration damping torque is determined by the sum of a pulse-type active damping torque and a continuously applied cost regenerative torque.
The method according to claim 1,
When the vehicle controller receives the ABS operation signal from the ABS ECU, it calculates the vibration damping torque value, generates and outputs a corresponding motor torque command, and the motor controller sends the motor torque through the inverter according to the motor torque command applied from the vehicle controller. Motor control method for driving system vibration reduction during ABS operation, characterized in that for controlling.
delete The method according to claim 1,
The active damping torque is calculated by applying the rotational acceleration of the motor from the change in the rotational speed of the motor detected by the speed detector to apply a pulse at the time when the rotational acceleration of the motor exceeds a set reference value drive system during ABS operation Motor control method for vibration reduction.
The method of claim 4,
The active damping torque is applied in positive direction acceleration when the shift lever position is forward, and in negative direction acceleration when reverse speed is applied.
The method according to claim 1 or 4,
A pulse amplitude of the active damping torque is set to be determined according to a motor rotational speed detected by a speed detector, and a pulse application time of the active damping torque is preset according to a natural vibration frequency of a drive system. Motor control method for driving system vibration reduction during operation, characterized in that the value.
The method according to claim 1,
And the cost regenerative torque is set to be determined according to a motor rotational speed detected by the speed detector and a shift lever position.
The method of claim 7,
In the initial stage of switching from the regenerative braking operation state to the ABS operating state during vehicle braking, the cost regenerative torque is set to be determined as a value applied to a previous regenerative braking torque or cost regenerative torque value and a change rate according to the motor rotation speed. Motor control method for driving system vibration reduction during ABS operation.
The method according to claim 8,
And the cost regenerative torque is set to be determined by a larger value of a torque value to which a change rate is applied during ABS operation and a torque value according to a motor rotation speed and a shift lever position.

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