JP7513371B2 - Control method for electric vehicle and control device for electric vehicle - Google Patents

Description

The present invention relates to a method for controlling an electric vehicle and a control device for an electric vehicle.

A method for controlling an electric vehicle is known in which a first torque target value is calculated based on vehicle information such as the amount of accelerator pedal operation and the motor rotation speed, and a second torque target value, which is a feedback component, is calculated based on the difference between the actual and estimated motor rotation speed, and the sum of the first and second torque target values is used as a torque command value to control the motor.

However, in this type of control method, when the first torque target value is small, disturbances such as unevenness of the road surface on which the vehicle is traveling can cause the second torque target value to fluctuate, which can cause the torque command value to reverse its positive and negative values, resulting in abnormal noise in the reducer.

Therefore, according to the technology disclosed in Patent Document 1, the second torque target value is limited by limit values (upper limit value and lower limit value) corresponding to the first torque target value, so that the sum of the first torque target value and the second torque target value has the same sign as the first torque target value. In this way, the torque command value does not reverse between positive and negative, and the occurrence of abnormal noise is suppressed.

JP 2012-075257 A

However, in a vehicle that is stopped without creeping when the accelerator pedal is not depressed, the first torque target value becomes zero on a flat road, and the second torque target value is also limited to zero. Therefore, when the first torque target value is zero, feedback control is not performed, and so even if torque ripple occurs on the motor output shaft, the ripple cannot be suppressed. The torque caused by the torque ripple is transmitted to the tires via the drive shaft, causing fluctuations in the motor rotation speed and therefore fluctuations in the motor torque. When this motor torque fluctuation is transmitted to the electric vehicle, there is a problem in that it generates vibrations that are uncomfortable for the occupants.

The present invention was made with an eye on these issues, and aims to provide a method for controlling an electric vehicle that suppresses fluctuations in motor torque.

One aspect of the control method for an electric vehicle of the present invention is a control method for an electric vehicle that calculates a torque command value according to vehicle information and controls a motor according to the torque command value. The control method for an electric vehicle includes a first torque target value calculation step of calculating a first torque target value that is a target value of the output torque of the motor based on the vehicle information, a second torque target value calculation step of calculating a second torque target value used for feedback control based on the rotation speed of the motor, a third torque target value calculation step of setting a limit value to a value according to the first torque target value and generating a third torque target value based on the second torque target value, and a torque command value calculation step of calculating a torque command value by adding the first torque target value and the third torque target value. In the limit step, if the absolute value of the first torque target value falls below a predetermined torque value, the setting of the limit value according to the first torque target value is interrupted.

According to one aspect of the present invention, it is possible to suppress fluctuations in motor torque.

FIG. 1 is a block diagram of an electric vehicle controlled by a control method according to a first embodiment. FIG. 2 is a block diagram showing the vibration suppression control unit and the motor. FIG. 3 is an explanatory diagram showing the equation of motion of the driven torsional vibration system. FIG. 4 is a graph showing the characteristics of H(s). FIG. 5 is a block diagram showing a vibration suppression control unit and a motor of a comparative example. FIG. 6 is a graph showing the torque limiting characteristic. FIG. 7 is a graph showing the torque limiting characteristic of the comparative example. FIG. 8A is a timing chart showing the relationship between the torque command value, the rotation speed, and the vehicle longitudinal G in the comparative example. FIG. 8B is a timing chart showing the relationship between the torque command value, the rotation speed, and the vehicle longitudinal G in this embodiment. FIG. 9 is a block diagram showing a vibration damping control unit and a motor according to the second embodiment.

The following describes an embodiment of the present invention with reference to the drawings.

First Embodiment
FIG. 1 is a schematic configuration diagram of an electric vehicle 100 according to the first embodiment.

The electric vehicle 100 has an accelerator opening sensor 1, a motor torque setting unit 2, a vibration control unit 3, a motor torque control unit 4, a motor 5, a motor rotation angle sensor 6, a drive shaft 7, and drive wheels 8 and 9.

The accelerator opening sensor 1 is a sensor that detects the accelerator opening A according to the accelerator pedal operation by the user of the electric vehicle 100, and transmits the detected accelerator opening A to the motor torque setting unit 2.

The motor torque setting unit 2 determines a first torque target value T*, which is a target value of the motor torque, based on the accelerator opening A detected by the accelerator opening sensor 1 and the rotation speed y detected by a motor rotation angle sensor 6, which will be described ^{later. Then, the motor torque setting unit 2 outputs the determined first torque target value T* to} the vibration damping control unit 3.

As a specific example, the motor torque setting unit 2 prestores a map in which the accelerator opening A and the rotation speed y, which are vehicle information, correspond to the ideal torque target value _Td ^* . The motor torque setting unit 2 uses the map to read out the ideal torque target value _Td ^* that corresponds to the input accelerator opening A and the rotation speed y. Furthermore, the motor torque setting unit 2 performs a filter process having a transfer characteristic of Gm(s)/Gp(s) determined by a vehicle model described below on the read out ideal torque target value _Td ^* to determine the first torque target value T ^* .

As will be explained later, Gm(s) is a transfer characteristic in an ideal model of the electric vehicle 100, in which the torque command value is the input value and the motor rotation speed is the output value. Gp(s) is a transfer characteristic in an actual vehicle model, in which the torque command value is the input value and the motor rotation speed is the output value.

As another example, the electric vehicle 100 may have a host controller, and the host controller may determine the first torque target value T ^* instead of the motor torque setting unit 2. In such a case, the first torque target value T ^* is input from the host controller to the vibration damping control unit 3.

As will be described later with reference to FIG. 2 , the vibration damping control unit 3 calculates a motor torque command value T ^'* in response to inputs of the first torque target value T ^* and the rotation speed y, and outputs the motor torque command value T ^'* to the motor torque control unit 4.

The motor torque control unit 4 determines an applied voltage so that the output torque of the motor 5 coincides with or follows the motor torque command value T ^′* , and outputs the determined applied voltage to the motor 5 .

The motor 5 generates torque according to the applied voltage from the motor torque control unit 4, and transmits the generated torque to the drive wheels 8 and 9 via the drive shaft 7.

The functions of the motor torque setting unit 2, the vibration damping control unit 3, and the motor torque control unit 4 may be realized by, for example, one or more microcomputers. In such a case, the control is performed by executing a program stored in the microcomputer. The motor 5 may also include an inverter, which is driven by a PWM signal generated in the motor torque control unit 4 according to the motor torque command value T ^'* .

Figure 2 is a block diagram of a configuration including the vibration control unit 3.

The vibration suppression control unit 3 outputs a motor torque command value T ^'* to an adder 110 in response to an input of a first torque target value T ^* . The adder 110 receives an input of a disturbance torque d, calculates the sum of the motor torque command value T ^'* and the disturbance torque d, and outputs the sum as a command value to a control block 120. The control block 120 outputs the rotation speed y of the motor 5 in response to the input command value.

The vibration control unit 3 has a motor rotation speed estimation block 30, a subtractor 31, a second torque target value setting block 32, a third torque target value setting block 33, and a motor torque command value calculation block 34.

The motor speed estimation block 30 processes the transfer characteristic Gp(s) of the motor torque command value T ^'* , which is the first torque target value T ^* plus the third torque target value _T3 ^* , which is a feedback component, to calculate the rotation speed command value y^. The motor speed estimation block 30 outputs the rotation speed command value y^ to the subtractor 31.

The subtractor 31 calculates the deviation e between the rotation speed command value y^ output from the motor rotation speed estimation block 30 and the motor rotation speed y output from the control block 120.

The second torque target value setting block 32 processes the deviation e obtained by the subtractor 31 using H(s)/Gp(s), which is made up of the transfer characteristic Gp(s) and the transfer characteristic H(s), to calculate the second torque target value _T2 ^* .

The transfer characteristic H(s) is set so that the difference between the denominator order and the numerator order is equal to or greater than the difference between the denominator order and the numerator order of the transfer characteristic Gp(s). This makes it possible to stabilize the control system.

The third torque target value setting block 33 performs torque limitation on the second torque target value _T2 ^* in accordance with the first torque target value T ^* . Specifically, the third torque target value setting block 33 performs limitation processing based on a limit value on the second torque target value _T2 ^* input from the second torque target value setting block 32, and outputs the limited target value as the third torque target value _T3 ^* to the motor torque command value calculation block 34. As described later, the limit value is set to a value corresponding to the first torque target value T ^* , and under certain conditions, the setting to a value corresponding to the first torque target value T ^* is interrupted.

The motor torque command value calculation block 34 is an adder that calculates a motor torque command value T _' * by adding the third torque target value T3 ^* output from the third torque target value setting block 33 and the first torque target value T ^* calculated by the motor torque setting unit 2. The motor torque command value calculation block 34 outputs the calculated motor torque command value T ^{' *} to the motor rotation speed estimation block 30 and the adder 110.

The adder 110 adds a disturbance torque d occurring in the vehicle to the motor torque command value T ^′* calculated by the motor torque command value calculation block 34 , and outputs the sum to the control block 120 .

The control block 120 controls the vibration suppression control unit 3 and the motor 5, and has a transfer function (transfer characteristic) Gp(s). The control block 120 outputs the rotation speed y of the motor 5 in response to the input of a command value obtained by addition in the adder 110. The rotation speed y is measured by the motor rotation angle sensor 6 and is fed back and output to the subtractor 31 of the vibration suppression control unit 3.

Next, we will explain the transfer characteristic Gp(s) determined by a model that has the transfer characteristic of the output of the rotation speed y relative to the input of the torque command value in the electric vehicle 100.

3A and 3B are diagrams showing a model of the driving force transmission system of the electric vehicle 100. The following parameters are shown in these drawings.
_Jm : Inertia of electric motor _Jw : Inertia of drive wheel M: Mass of vehicle KD: Torsional rigidity of drive system _KT : Coefficient related to friction between tire and road surface _N : Overall gear ratio r: Overload radius of tire _ωm : Angular velocity of electric motor _Tm : Torque of motor _TD : Torque of drive wheel _ωw : Angular velocity of drive wheel F: Force applied to vehicle V: Vehicle speed

Using these parameters, the following equation of motion can be derived from the configuration in Figure 3.

From equations (1) to (5), the transfer characteristic from the motor torque _Tm to the drive shaft torsion angle θ can be obtained as follows:

where the parameters in equation (6) are as follows:

When we examine the poles and zeros of the transfer characteristic shown in equation (6), we can approximate it to the transfer characteristic of the following equation, where one pole and one zero show extremely close values. This corresponds to α and β in this equation showing extremely close values. Therefore, equation (6) can be expressed as the following equation.

Therefore, by performing pole-zero cancellation (approximating α = β) in equation (15), it is possible to construct a (second-order)/(third-order) transfer characteristic Gp(s) as shown in the following equation.

To realize the transfer characteristic Gp(s) shown in equation (16) using microcomputer processing, for example, the following equation can be obtained by z-transforming and discretizing it using equation (17).

Here, T indicates the sampling time.

Next, we will explain the bandpass filter H(s) using Figure 4.

Since H(s) is a bandpass filter, it is a feedback element that reduces only vibration. By having H(s) have the characteristics shown in Figure 4, the effect of vibration reduction can be enhanced. In other words, it is preferable that the bandpass filter H(s) is set so that the attenuation characteristics of the lowpass side and the highpass side match, and the torsional resonance frequency of the drive system is in the center of the passband on a logarithmic axis (log scale).

For example, when H(s) is composed of a first-order low-pass filter and a high-pass filter, H(s) can be expressed by the following equation, where the torsional resonance angular frequency of Gp(s) is _ωp .

Here, in order to find the k in equation (18) that maximizes the vibration damping effect, we consider a configuration including a vibration damping control unit 3' as shown in Figure 5.

Compared to the block diagram of vibration suppression control unit 3 shown in Figure 2, third torque target value setting block 33 has been deleted from Figure 5. Therefore, the second torque target value _T2 ^* output from the second torque target value setting block 32 is output directly to the motor torque command value calculation block 34. In this block diagram, if we assume that the first torque target value T ^* is zero, which is a state in which vibration due to feedback torque is likely to occur, the following equations (19) to (22) are derived.

Note that in the following, the Laplace operator will be omitted.

By substituting equation (22) into equation (19), the response of the motor speed to the disturbance torque d is expressed by the following equation.

In equation (23), substituting equations (17) and (18) for the transfer characteristic G _p (1−H(s)) from d to y gives the following equation.

A high vibration damping effect means that no vibration is caused by disturbance torque d, so if we set 2-k=2ξp, the numerator and denominator in equation (24) cancel each other out, resulting in the following equation, which is a transmission characteristic that does not cause vibration.

From the above, the k that maximizes the vibration damping effect is expressed by the following formula.

By substituting equation (26) into equation (18), H(s) is expressed by the following equation.

The G(s) and H(s) obtained in this manner are used in the motor speed estimation block 30, the second torque target value setting block 32, and the control block 120.

Figure 6 shows the torque limiting characteristic. This torque limiting characteristic is used in the processing in the third torque target value setting block 33 shown in Figure 2.

If the predetermined torque is _Tx , when the first torque target value T ^* is smaller than the predetermined value _-Tx or larger than + _Tx (T ^* <- _Tx , + _Tx <T ^* ), the upper limit value _Th is set to the absolute value of the first torque target value T ^* , and the lower limit value _Tl is set to a negative value obtained by inverting the sign of the absolute value of the first torque target value T ^* . That is, in this region, the limit value used for torque limiting is set to a value corresponding to the first torque target value T ^* .

On the other hand, when the first torque target value T ^* is greater than -Tx _{and smaller than +Tx ( -Tx} < T ^* < + _Tx ), the upper limit value _Th is set to _Tx , and the lower limit value _Tl is set to _-Tx . That is, in this region, the setting of the limit value according to the first torque target value T ^* is interrupted. Note that in this embodiment, an example has been described in which the absolute value of the limit value is set to a predetermined _Tx when the setting of the limit value according to the first torque target value T ^* is interrupted, but this is not limiting. The limit value may be set to a value whose absolute value is greater than zero.

It is preferable that _Tx is equal to the torque ripple amplitude of the motor 5. By setting _Tx in this manner, it is possible to limit the interruption of setting the value according to the first torque target value T ^* , as described below. Note that the torque ripple is, for example, a torque pulsation generated in the motor 5 by the interaction between the magnet magnetic flux and the magnetic flux due to the current, and is a periodic disturbance including each mechanical angle order component (24th, 48th, 96th).

The third torque target value setting block 33 shown in FIG. 2 determines whether the second torque target value T ₂ ^* is within the range between an upper limit value T _h and a lower limit value T _l .

When the second torque target value _T2 ^* is in the range between the upper limit value _Th and the lower limit value _Tl of the torque limit value, the third torque target value setting block 33 outputs the same value as the second torque target value _T2 ^* as the third torque target value _T3 ^* .

When the second torque target value T ₂ ^* is not within the range between the upper limit value T _h and the lower limit value T _l of the torque limit value (T ₂ ^* < -T _l , +T _h < T ₂ ^* ), the second torque target value T ₂ ^* is limited by the upper limit value T _h or the lower limit value T _l . Specifically, when the second torque target value T ₂ ^* is greater than the upper limit value T _h (+T _h < T ₂ ^* ), the third torque target value setting block 33 outputs the upper limit value T _h as the third torque target value T ₃ ^* . When the second torque target value T ₂ ^* is smaller than the lower limit value T _l (T ₂ ^* < -T _l ), the third torque target value setting block 33 outputs the lower limit value T _l as the third torque target value T ₃ ^* .

The effect of the torque limiting shown in Figure 6 as in this embodiment will be described below.

Figure 7 shows the torque limiting characteristics as a comparative example.

In the comparative example shown in Fig. 7, the third torque target value setting block 33 sets an upper limit value T _h and a lower limit value T _l according to the first torque target value T ^* , regardless of the first torque target value T ^* , and limits the second torque target value T ₂ ^* by the upper limit value T _h and the lower limit value T _l . The upper limit value T _h is set to the absolute value of the first torque target value T ^* , and the lower limit value T _l is set to a negative value obtained by inverting the sign of the absolute value of the first torque target value T ^* . For example, when the first torque target value T ^* is T _1a ^* , the upper limit value of the torque limit value is the positive value of the absolute value of T _1a (+ | T _1a |), and the lower limit value of the torque limit value is the negative value of the absolute value of T _1a (- | T _1a |).

The comparative example shown in this figure differs from the torque limit characteristic of the present embodiment shown in Figure 6 in the hatched region in the figure, where the first torque target value T ^* is greater than _-Tx and smaller than + _Tx ( _-Tx < T ^* < + _Tx ). In this region, in the comparative example, the upper limit value _Th is set to _Tx and the lower limit value _Tl is set to _-Tx , that is, the limit values are set to values corresponding to the first torque target value T ^* . In contrast, in the present embodiment, the upper limit value _Th and the lower limit value _Tl are _Tx and _-Tx , respectively, and setting of the values corresponding to the first torque target value T ^* is interrupted.

Due to the torque limiting characteristic of the comparative example, the torque target value becomes the following value. For example, consider the case where the first torque target value T ^* is a negative value and the second torque target value _T2 ^* is a positive value greater than the absolute value of the first torque target value T ^* . In such a case, since the third torque target value _T3 ^* is limited to the absolute value of the first torque target value T ^* , the sum of the first torque target value T ^* and the third torque target value _T3 ^* is not positive, and the sign of the sum does not differ from that of the first torque target value T ^* .

That is, due to the limitations of this comparative example, the absolute value of the third torque target value T ₃ ^* is smaller than the absolute value of the first torque target value T ^* . As a result, the signs of the first torque target value T ^* and the motor torque command value T ^{' *} are the same before and after the motor torque command value calculation block 34 shown in FIG. 2. Therefore, the direction of the torque generated by the motor 5 is the same for the motor torque command value T ^{' *} and the first torque target value T ^* . Therefore, the generation of rotational torque in the direction opposite to the rotation direction is suppressed, and noise caused by gear meshing can be reduced.

However, in the comparative example, when the electric vehicle 100 is stopped on a flat road without creeping, the first torque target value T ^* is zero and the second torque target value _T2 ^* that suppresses vibration is also small, so that if the torque limit shown in Fig. 7 is performed, the third torque target value _T3 ^* output from the third torque target value setting block 33 is limited to zero. Therefore, the feedback control does not function effectively, and if torque ripple occurs in the electric vehicle 100, the ripple cannot be suppressed.

6 is performed, so that when the first torque target value T ^* is zero and the second torque target value _T2 ^* is a relatively small value, setting of the limit value according to the first torque target value T ^* is interrupted and the limit value is set to a predetermined _Tx whose absolute value is greater than zero. Therefore, the third torque target value _T3 ^* , which is the value obtained by limiting the second torque target value _T2 ^* by the limit value, does not become zero, so that feedback control functions and torque ripple can be suppressed.

Below, we explain the effects derived from this embodiment using simulation results.

Figure 8A shows the comparative example, and Figure 8B shows the present embodiment.

In each of Figures 8A and 8B, from the top, the torque command value, the rotation speed of the motor 5, and the longitudinal G of the electric vehicle 100 are shown over time. In the case of the electric vehicle 100 shown in Figure 1, the torque ripple is dependent on the rotation speed and is synchronized with the torsional resonance of the drive shaft.

As shown in Fig. 8A, in the comparative example, the feedback control is suppressed, so that the motor torque command value changes while pulsating, and vibrations with a large pulsation width are generated as shown in the rotation speed and forward and backward G. In contrast, in the present embodiment shown in Fig. 8B, the feedback control functions to reduce the pulsation width of the motor torque command value, so that the generation of vibrations can be suppressed. Furthermore, since the predetermined torque _Tx in Fig. 6 is set to be equal to the torque ripple amplitude of the motor 5, when torque ripples are generated, the setting of the limit value according to the first torque target value T ^* is interrupted within the range required for feedback control. Therefore, the necessary feedback control is performed, so that the effect of suppressing the vibration of the torque ripple can be improved.

The first embodiment provides the following advantages:

According to the vehicle control method of the first embodiment, the third torque target value setting block 33 performs torque limitation on the second torque target value _T2 ^* used in feedback control. Then, in the motor torque command value calculation block 34, the first torque target value T ^* and the third torque target value _T3 ^* , which is the torque-limited second torque target value _T2 ^* , are added, and the sum is used to control the motor 5. In the third torque target value setting block 33, as shown in Fig. 6, when the absolute value of the first torque target value T ^* exceeds a predetermined torque _Tx , the upper limit value _Th and the lower limit value _Tl are set to values corresponding to the first torque target value T ^* , but when the absolute value of the first torque target value T ^* falls below the predetermined torque _Tx , the setting of the upper limit value _Th and the lower limit value _Tl to values corresponding to the first torque target value T ^* is interrupted.

In this way, when the first torque target value T ^* becomes zero while the vehicle is stopped, for example, setting of the limit values (upper limit value T _h and lower limit value T _l ) according to the first torque target value T ^* is interrupted. Therefore, the second torque target value T ₂ ^* is not limited to zero according to the first torque target value T ^* . As a result, feedback control is performed even when the first torque target value T ^* is zero, so torque ripple can be suppressed.

According to the vehicle control method of the first embodiment, when the absolute value of the first torque target value T ^* falls below the predetermined torque _Tx , limit values (upper limit value _Th and lower limit value _Tl ) whose absolute values are greater than zero are set.

In this way, even if the first torque target value T ^* is zero, the limit values (upper limit value T _h and lower limit value T _l ) do not become zero, and the third torque target value T ₃ ^* does not become zero. As a result, even if the first torque target value T ^* is zero, the feedback control functions, so that the torque ripple can be suppressed.

According to the vehicle control method of the first embodiment, the predetermined torque Tx is approximately equal to the amplitude of the torque ripple generated in the electric vehicle 100. Here, when the first torque target value T ^* is in a certain region (-Tx<T ^* <Tx), the setting of the upper limit value T _h and the lower limit value T _l according to the first torque target value T ^* is interrupted, so that feedback control functions in this region. Therefore, by making the predetermined torque Tx approximately equal to the amplitude of the torque ripple, the setting of the upper limit value T _h and the lower limit value T _l according to the first torque target value T ^* is interrupted in the region where the torque ripple occurs (-Tx<T* ^< Tx), so that feedback control is performed. In this way, the torque ripple can be suppressed.

In addition, when vibrations greater than the torque ripple occur, the limit value is set to a value corresponding to the first torque target value T ^* , so that the motor torque command value T ^'* and the first torque target value T ^* have the same sign and rotate in the same direction, as in the comparative example. This suppresses the generation of torque in the reverse rotation direction, thereby reducing noise caused by gear meshing.

Second Embodiment
In the first embodiment, an example has been described in which the predetermined torque _Tx, which is the threshold value at which the setting of the limit value according to the first torque target value T ^* is interrupted as shown in Fig. 6. In the present embodiment, an example will be described in which the predetermined torque _Tx is variable.

Figure 9 is a block diagram of a configuration including the vibration control unit 3 of the second embodiment.

This embodiment differs from the configuration of the first embodiment shown in FIG. 2 in that the rotation speed y output from the control block 120 is input to the third torque target value setting block 33.

The third torque target value setting block 33 switches between using the torque limiting characteristics as shown in FIG. 6 and setting the limiting value as shown in FIG. 7, depending on the magnitude of the rotation speed y.

Here, in the low rotation range of the motor 5, vibration of the torque ripple is likely to occur due to resonance between the drive shaft and the torque ripple order components. In addition, because the rotation speed fluctuation is small, the oscillatory torque pulsation is small when there is a detection error in the motor rotation angle sensor 6, which is the rotation speed detection means. Note that an error in the motor rotation angle sensor 6, for example, is a relatively inexpensive resolver that is generally used as the motor angle detection means, and therefore an error that occurs when the angle detected by this resolver is converted to detect the rotation speed.

When the rotation speed y is smaller than a predetermined rotation speed, it can be determined that the rotation speed is in the low rotation range. Therefore, the third torque target value setting block 33 limits the torque using the torque limit characteristic shown in Fig. 6, and the setting of the limit value according to the first torque target value T ^* is interrupted, so that the torque ripple can be suppressed by feedback control.

When the rotation speed y is greater than a predetermined rotation speed, it can be determined that the rotation speed is in the high rotation speed region. In the high rotation speed region, the frequency of occurrence of resonance of torque ripple is extremely low, but since the rotation speed fluctuation is large, oscillatory torque pulsation due to detection error of the motor rotation angle sensor 6 is likely to occur. Therefore, the third torque target value setting block 33 performs the torque limiting shown in Fig. 7, so that the limiting value is set to a value corresponding to the first torque target value T ^* , and oscillatory torque pulsation can be suppressed.

The predetermined rotation speed is set to a rotation speed at which the torsional frequency and the torque ripple order component resonate when the motor torque is transmitted to the drive shaft. By setting in this manner, only when the rotation speed y is lower than the predetermined rotation speed and there is a high possibility of torque ripple occurring due to resonance, the setting of the limit value according to the first torque target value T ^* as shown in Figure 6 is interrupted, so that feedback control is performed to suppress the vibration of the torque ripple. On the other hand, when the rotation speed y is higher than the predetermined rotation speed and the oscillatory torque pulsation is large, the limit value is set to a value according to the first torque target value T ^* as shown in the torque limit characteristic of Figure 7, and the oscillatory torque pulsation is suppressed.

The specified value may also have hysteresis or a slope when the state transition is variable.

The second embodiment provides the following advantages:

According to the control method for an electric vehicle of the second embodiment, when the rotation speed y is smaller than a predetermined rotation speed, the third torque target value setting block 33 is in the low rotation range and torque ripple due to resonance is likely to occur, so when the second torque target value _T2 ^* is close to zero as shown in Figure 6, the setting of the limit value corresponding to the first torque target value T ^* is interrupted, and torque ripple can be suppressed by feedback control.

On the other hand, when the rotation speed y is greater than the predetermined rotation speed, a relatively large oscillatory torque pulsation occurs due to the detection error of the motor rotation angle sensor 6. Therefore, even if the torque is limited by the torque limiting characteristic of FIG. 7 and feedback control is restricted, the oscillatory torque pulsation due to the detection error of the motor rotation angle sensor 6 can be suppressed.

In this way, in the low rotation range, feedback control can be performed by interrupting the setting of the limit value according to the first torque target value T ^* , so that torque ripple can be suppressed. On the other hand, in the high rotation range, even if torque is limited using a limit value according to the first torque target value T ^* , it is possible to suppress the occurrence of relatively large vibration-like torque pulsation caused by detection errors of the motor rotation angle sensor 6. In this way, the longitudinal G generated in the electric vehicle 100 can be efficiently suppressed by selectively switching the control.

According to the control method for an electric vehicle of the second embodiment, the third torque target value setting block 33 sets the rotation speed at which the torsional vibration frequency generated when the torque of the motor 5 is transmitted to the drive shaft and the torque ripple order component resonate as the predetermined rotation speed, which is the threshold value used for switching between the torque limits in FIG. 6 and FIG. 7.

By setting it in this way, when there is a high possibility of resonance, the torque ripple vibration can be suppressed by implementing the torque limit shown in FIG. 7. On the other hand, when there is a low possibility of resonance, the torque limit shown in FIG. 6 can be implemented to suppress the occurrence of oscillatory torque pulsation caused by detection errors of the motor rotation angle sensor 6.

(Modification)
In the second embodiment, an example has been described in which the torque limiting characteristics shown in Fig. 6 and Fig. 7 are switched. In this modified example, an example in which the predetermined torque _Tx is configured to be variable will be described.

In this modified example, the third torque target value setting block 33 decreases the predetermined torque _Tx as the rotation speed y increases, and increases the predetermined torque _Tx as the rotation speed y decreases.

When the rotation speed y is small, the rotation speed is in a low rotation range and torque ripple is likely to occur, so the predetermined torque _Tx is increased so that the torque ripple is easily suppressed by feedback control, thereby widening the range where the setting of the limit value according to the first torque target value T ^* is interrupted. On the other hand, when the rotation speed y is large, the rotation speed is in a high rotation range and torque ripple is unlikely to occur, so the predetermined torque _Tx is decreased to narrow the range where the setting of the limit value according to the first torque target value T ^* is interrupted, thereby suppressing the occurrence of oscillatory torque pulsation.

This modified example provides the following advantages:

According to this modified example, the third torque target value setting block 33 decreases the predetermined torque _Tx as the rotation speed y increases, and increases the predetermined torque _Tx as the rotation speed y decreases.

By setting in this manner, when the rotation speed y is small and in a low rotation range where torque ripple is likely to occur, the predetermined torque _Tx is increased to make it easier to interrupt the setting of the limit value according to the first torque target value T ^* . This makes it easier to suppress torque ripple by feedback control. On the other hand, when the rotation speed y is large and in a high rotation range where torque ripple is unlikely to occur, the predetermined torque _Tx is decreased to make it harder to interrupt the setting of the limit value according to the first torque target value T ^* , so that torque is limited and the sum of the first torque target value and the second torque target value has the same sign as the first torque target value, thereby suppressing the generation of abnormal noise.

The predetermined torque _Tx is changed in accordance with the rotation speed y, taking into consideration the frequency of torque ripple occurrence, so as to change the region in which feedback control for suppressing torque ripple is performed. In this way, by changing the region in which setting of the limit value according to the first torque target value T ^* is interrupted, it becomes easier to suppress torque ripple when the frequency of torque ripple occurrence is relatively high.

Although the embodiments of the present invention have been described above, the above embodiments merely show some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. Furthermore, the above embodiments can be combined as appropriate.

REFERENCE SIGNS LIST 1 Accelerator opening sensor 2 Motor torque setting section 3, 3' Vibration damping control section 4 Motor torque control section 5 Motor 6 Motor rotation angle sensor 7 Drive shaft 8, 9 Drive wheel 30 Motor rotation speed estimation block 31 Subtractor 32 Second torque target value setting block 33 Third torque target value setting block 34 Motor torque command value calculation block 36 Block 100 Electric vehicle 110 Adder 120 Control block

Claims (6)

A method for controlling an electric vehicle, comprising: calculating a torque command value according to vehicle information; and controlling a motor according to the torque command value,
a first torque target value calculation step of calculating a first torque target value that is a target value of an output torque of the motor based on the vehicle information;
a vibration suppression control step of calculating the torque command value based on the first torque target value and a rotation speed of the motor;
a motor torque control step of controlling a torque output by the motor based on the torque command value,
The vibration suppression control step includes:
a second torque target value calculation step of calculating a second torque target value used in feedback control based on a deviation between a rotation speed of the motor estimated based on the torque command value and a rotation speed of the motor obtained by measurement;
a third torque target value calculation step of limiting the second torque target value by using a predetermined limit value to set the third torque target value;
a torque command value calculation step of calculating the torque command value by adding the first torque target value and the third torque target value,
the limit value is a value such that the torque command value has the same sign as the first torque target value,
a third torque target value calculation step of calculating a third torque target value from the first torque target value and a predetermined torque value that is substantially equal to an amplitude of a torque ripple of the motor, the third torque target value being calculated by interrupting the limiting of the second torque target value using the limit value, and setting a value limited using a predetermined value having an absolute value greater than zero as the third torque target value. A method for controlling an electric vehicle according to claim 1, comprising:
In the third torque target value calculation step, when the absolute value of the first torque target value is lower than the predetermined torque value, the limit value is set to a value whose absolute value is greater than zero.
A method for controlling an electric vehicle. A method for controlling an electric vehicle according to claim 1 or 2, comprising:
A control method for an electric vehicle, wherein the predetermined torque value is set to be larger as the rotation speed of the motor is smaller. A method for controlling an electric vehicle according to any one of claims 1 to 3, comprising:
When the rotation speed of the motor exceeds a predetermined rotation speed, in the third torque target value calculation step, a value obtained by limiting the second torque target value using the limit value is set as a third torque target value;
a third torque target value calculation step of calculating a third torque target value when the rotation speed of the motor falls below the predetermined rotation speed, the third torque target value calculation step is performed by interrupting the limiting of the second torque target value using the limit value, and setting a value limited using the predetermined value as the third torque target value. A method for controlling an electric vehicle according to claim 4, comprising:
The control method for an electric vehicle, wherein the predetermined rotation speed is a rotation speed at which a torsional vibration frequency generated when torque of the motor is transmitted to a drive shaft resonates with a torque ripple order component. A control device for an electric vehicle having a sensor for acquiring vehicle information, a motor as a drive source, and a controller for controlling the motor,
The controller:
calculating a first torque target value that is a target value of an output torque of the motor based on the vehicle information;
performing vibration suppression control to calculate a torque command value based on the first torque target value and the rotation speed of the motor;
controlling the torque output by the motor based on the torque command value;
In the vibration damping control,
calculating a second torque target value to be used in feedback control based on a deviation between a rotation speed of the motor estimated based on the torque command value and a rotation speed of the motor obtained by measurement;
a value obtained by limiting the second torque target value using a predetermined limit value is set as a third torque target value;
Calculating the torque command value by adding the first torque target value and the third torque target value;
A control device for controlling the motor in response to the torque command value,
the limit value is a value such that the torque command value has the same sign as the first torque target value,
a control device for an electric vehicle, wherein, when an absolute value of the first torque target value falls below a predetermined torque value that is approximately equal to an amplitude of a torque ripple of the motor, limiting the second torque target value using the limit value is discontinued, and a value limited using a predetermined value whose absolute value is greater than zero is set as the third torque target value.

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