JP2004120879A - Motor control method of electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dispense with switching operation of motor control method by an operator and to reduce the number of components of a brake system part of an electric vehicle. <P>SOLUTION: A torque command value is calculated based on a speed command value corresponding to the step-in amount of an accelerator pedal and a travel speed of the electric vehicle, and a motor for travelling is driven according to the torque command value. When the accelerator pedal is off with the sign of the torque command value being positive, the torque command value is changed down to zero following an attenuation pattern (steps S102-S106). If the torque command value is below zero when the accelerator pedal is off, the torque command value is limited to zero or below while the accelerator pedal is off (steps S107-S110). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a motor control for an electric vehicle that calculates a torque command value based on a speed command value corresponding to an accelerator operation amount and a traveling speed of the electric vehicle, and drives a driving motor in accordance with the torque command value. About the method.
[0002]
[Prior art]
The main methods for controlling the traveling motor of an electric vehicle include torque control and speed control.
[0003]
In an electric vehicle that employs torque control, even when the operation amount of the accelerator pedal is constant, the load applied to the motor changes when moving from a slope to a flat surface or when traveling on an uneven road surface, It is difficult to control the speed of the electric vehicle.
[0004]
In an electric vehicle employing speed control, the traveling speed is controlled in accordance with the amount of depression of an accelerator pedal. However, when the vehicle is decelerated by a mechanical brake, the traveling speed command value must be naturally reduced. Therefore, it is necessary to perform control in cooperation with the control unit that performs speed control and the mechanism of the mechanical brake. For example, if there is no detecting means for detecting the depression state of the brake, when the speed of the electric vehicle decreases, it is not possible to determine whether the cause is deceleration due to operation of a mechanical brake or deceleration due to load fluctuation such as climbing a slope. . For this reason, it is said that when speed control is performed, it is necessary to notify the operating state of the mechanical brake to a speed control unit using a brake sensor.
[0005]
In order to ensure stable traveling performance without being affected by a change in load applied to an electric vehicle, a technique has been proposed in which a driver selects either torque control or speed control by a switch (for example, see Patent Reference 1).
[0006]
Further, in an electric vehicle that adopts speed control, a technique using an electromagnetic brake instead of a mechanical brake has been proposed (for example, see Patent Document 2). In this technique, the control of the electromagnetic brake and the speed control are controlled by the same controller, so that it is easy to determine the brake state.
[0007]
[Patent Document 1]
JP-A-6-14404 (paragraph [0021])
[Patent Document 2]
JP-A-9-130913 (paragraphs [0012] to [0015])
[0008]
[Problems to be solved by the invention]
By the way, in the technique of Patent Literature 1, there is an annoyance that a driver has to judge a traveling state and operate a switch during driving. Further, some drivers do not sufficiently recognize the difference between the speed control and the torque control, and such a driver cannot perform stable traveling.
[0009]
Further, in the technique of Patent Document 2, an electromagnetic brake and a brake switch are required, and it is necessary to control the electromagnetic brake based on a signal of the brake switch, resulting in an increase in cost.
[0010]
Even if a mechanical brake is used in the example shown in Patent Document 2, the detection means for detecting the depression state of the brake is still required. In particular, when there are two braking systems, a brake pedal and a hand brake, it is necessary to provide a brake switch on both the brake pedal and the hand brake.
[0011]
The present invention has been made in view of such a problem, and a motor control method for an electric vehicle that does not require a driver to switch the motor control method and that can reduce the number of parts of a braking system unit. The purpose is to provide.
[0012]
[Means for Solving the Problems]
A motor control method for an electric vehicle according to the present invention calculates a torque command value based on a speed command value corresponding to an operation amount of an accelerator and a traveling speed of the electric vehicle, and a motor for traveling according to the torque command value. In the motor control method for an electric vehicle for driving the vehicle, when the operation amount of the accelerator is returned to 0 and the sign of the torque command value is positive, the torque command value is set to 0 along a predetermined attenuation pattern. When the operation amount of the accelerator is 0 and the sign of the torque command value is 0 or less, the torque command value is limited to a value of 0 or less even if the speed command value becomes larger than the traveling speed. It is characterized by the following.
[0013]
By doing so, a sudden change in torque can be prevented, and the electric vehicle can be smoothly decelerated. Further, when the brake is applied to decelerate, the electric vehicle can be surely decelerated.
[0014]
In this case, if the damping pattern is a pattern in which the damping rate of the torque command value increases as time passes, it is possible to shift to a deceleration operation without vibration of the electric vehicle.
[0015]
Further, when the attenuation pattern is expressed by connecting a plurality of straight lines by a section based on a torque command value when the application of the attenuation pattern is started and a section of time, the torque command value is determined along the attenuation pattern. Is simplified to 0.
[0016]
Furthermore, the number of executions of the process of changing the torque command value to 0 along the damping pattern may be limited so that the process is executed only once while the operation amount of the accelerator is 0. .
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of a motor control method for an electric vehicle according to the present invention will be described with reference to FIGS.
[0018]
The motor control method for an electric vehicle according to the present embodiment is mainly executed by an ECU (Electric Control Unit) 12 in electric vehicle 10 shown in FIG.
[0019]
As shown in FIG. 1, the electric vehicle 10 travels using a motor 14 as a power source, and a rotating shaft of the motor 14 is connected to a differential gear 16 having a shifting function. The rotational power of the motor 14 is transmitted to the front wheels 20 via the differential gear 16 and the axle 18. A brake drum 24 is connected to each of the front wheel 20 and the rear wheel 22. When a brake pedal 26 is depressed, hydraulic pressure is applied to the brake drum 24 from a master cylinder (not shown) to brake the front wheel 20 and the rear wheel 22.
[0020]
The ECU 12 performs processing under the control of the CPU 30 that operates according to the program 28. The ECU 12 is supplied with a signal of a volume 34 for detecting the amount of depression of the accelerator pedal 32. The ECU 12 calculates a control signal value for the motor 14 based on the signal of the volume 34 and supplies it to an output interface (output I / F) 36. The output interface 36 supplies a control signal to the inverter 38, which controls the electric power supplied from the battery 40 and drives the motor 14 based on the command signal.
[0021]
The motor 14 is provided with a rotation speed detection sensor 42, which detects the rotation speed of the magnetic pole. The signal of the rotational speed detection sensor 42 is supplied to the ECU 12 via an input interface (input I / F) 44.
[0022]
The signal of the rotation speed detection sensor 42 supplied via the input interface 44 is multiplied by the gear ratio of the differential gear 16 to become the vehicle speed v (see FIG. 2).
[0023]
As is clear from FIG. 1, each brake drum 24 is operated by hydraulic pressure, and is a kind of a so-called mechanical brake. Therefore, the brake pedal 26 and the brake drum 24 can generate a braking force independently of the electric system such as the ECU 12. Further, a means (for example, a volume) for supplying the depression amount of the brake pedal 26 to an electric system such as the ECU 12 is not provided.
[0024]
As shown in FIG. 2, the ECU 12 performs control based on a signal of a volume 34 indicating a depression amount (operation amount) of an accelerator pedal 32 and a signal of a rotation speed detection sensor 42.
[0025]
In the ECU 12, the on / off determining unit 50 compares the signal of the volume 34 with a predetermined small threshold value, and determines whether the accelerator pedal 32 is on or off (the operation amount is 0) based on the magnitude relationship. Further, the speed command converter 52 calculates a speed command value c from the signal of the volume 34. That is, as shown in FIG. 3, the signal of the volume 34 and the speed command value c substantially correspond to each other, and when the signal of the volume 34 changes, the speed command value c changes so as to have a predetermined slope 72. .
[0026]
Returning to FIG. 2, the ECU 12 subtracts the speed command value c and the vehicle speed v at a subtraction point 54. The torque command value T is generated by multiplying the speed deviation ε as a result of the subtraction by a predetermined gain in the torque command unit 56.
[0027]
That is, the depression amount of the accelerator pedal 32 becomes the speed command value c via the speed command conversion unit 52, and the control is performed while feeding back the vehicle speed v. Therefore, the vehicle speed control is basically performed.
[0028]
By performing the vehicle speed control, the speed can be delicately controlled even when the load fluctuates or under heavy load, and unexpected behavior such as sudden acceleration when the accelerator pedal 32 is depressed does not occur.
[0029]
The positive torque limiting unit 58 generates a limited torque command value T1 in which the torque command value T supplied from the torque command unit 56 is limited to a negative value range. That is, when the sign of the torque command value T is positive, the limit torque command value T1 is set to “0”, and when the sign of the torque command value T is negative, the torque command value T is substituted into the limit torque command value T1. .
[0030]
When the accelerator pedal 32 is turned off, the torque command damping unit 60 generates a damping torque command value T2 based on the torque command value T according to the pattern shown in FIG. Specifically, as shown in FIG. 4, the time and the torque command value T are each divided into four regions, and individual attenuation processing is performed on each region. The point in time when the accelerator pedal 32 is turned off is defined as a reference time t0, the area U1 is up to the first time t1, the area U2 is up to the second time t2, the area U3 is up to the third time t3, and the area is after the third time t3. Classified as U4. Further, a portion where the torque command value T is p1 or less is divided into a region V1, a portion between p1 and p2 is a region V2, a portion between p2 and p3 is a region V3, and a portion where the torque command value T is p3 or more is divided into a region V4. . Further, four types of damping rates D1, D2, D3, and D4 are prepared in descending order of the torque command value T, and are selectively set from these. The attenuation rates D2, D3, and D4 may be set to, for example, D2 = 0.75 × D1, D3 = 0.5 × D1, and D4 = 0.25 × D1, based on the attenuation rate D1. In the example of FIG. 4, the attenuation rate D1 is represented by a solid line, the attenuation rate D2 is represented by an alternate long and short dash line, the attenuation rate D3 is represented by a dotted line, and the attenuation rate D4 is represented by a double line.
[0031]
When the accelerator pedal 32 is turned off, that is, when the torque command value T is within the range of the region V4 at the reference time t0, the damping ratio D4 in the region U1, the damping ratio D3 in the region U2, and the damping ratio D2 in the region U3. In the area U4, the damping torque command value T2 is generated by applying the damping rate D1.
[0032]
At the reference time t0, when the torque command value T is within the range of the area V3, the damping rate D3 is applied in the area U1, the damping rate D2 is applied in the area U2, and the damping rate D1 is applied in the areas U3 and U4. Generate
[0033]
When the torque command value T is within the range of the area V2 at the reference time t0, the damping torque command value T2 is generated by applying the damping rate D2 in the area U1 and the damping rate D1 in the areas U2, U3, and U4.
[0034]
When the torque command value T is within the range of the region V1 at the reference time t0, the damping torque command value T2 is generated by applying the damping rate D1 in the regions U1 to U4.
[0035]
Thus, the torque command damping unit 60 generates the damping torque command value T2 based on the torque command value T at the time when the accelerator pedal 32 is turned off. The damping torque command value T2 gradually attenuates and eventually becomes "0". The damping rate is a small value at the beginning when the accelerator pedal 32 is turned off, and is gradually increased with time. Further, the smaller the torque command value T, the larger the value of the damping rate. By generating the damping torque command value T2 in this way, the oscillation phenomenon of the motor 14 can be prevented.
[0036]
Further, the damping pattern, that is, the damping torque command value T2 can be divided by the initial torque command value T and the passage of time, and can be represented by connecting straight lines set for each section, so that complicated calculations are unnecessary. is there.
[0037]
Returning to FIG. 2, the switch unit 62 has a switch function that enables any one of the three input units 62a, 62b, and 62c. The torque command value T output by the torque command unit 56 is supplied to the input unit 62a of the switch unit 62. The limited torque command value T1 output from the positive torque limiting section 58 is supplied to an input section 62b of the switch section 62. The damping torque command value T2 output from the torque command damping unit 60 is supplied to the input unit 62c of the switch unit 62.
[0038]
The switch switching determining unit 64 performs a process based on the ON / OFF state of the accelerator pedal 32 and the torque command value T, and has a function of selecting and outputting one of the input units 62a, 62b, and 62c of the switch unit 62. Have. When the accelerator pedal 32 is on, the input switch 62a of the switch unit 62 is enabled. When the torque command value T is positive when the accelerator pedal 32 is off, the switch switching determination unit 64 determines whether the input of the switch unit 62 is valid. After the processing by the torque command attenuating section 60 is enabled, the input section 62b of the switch section 62 is enabled. If the torque command value T is 0 or less when the accelerator pedal 32 is turned off, the input section 62b of the switch section 62 is made valid.
[0039]
Each function in the ECU 12 shown in FIG. 2 is actually a process recorded in the program 28, and is executed by the CPU 30.
[0040]
Next, a method of controlling the motor 14 using the accelerator pedal 32, the ECU 12, the inverter 38, and the like configured as described above will be described with reference to FIGS. The flowchart in FIG. 5 is mainly executed by the CPU 30 based on the contents of the program 28, and is repeatedly executed at a predetermined minute time period.
[0041]
First, in step S1 of FIG. 5, it is determined whether the accelerator pedal 32 is on or off. This process is performed by the on / off determining unit 50. While the accelerator pedal 32 is off, the powering prohibition process of step S2 is continuously executed by an infinite loop. When the accelerator pedal 32 is on, the process proceeds to the next step S3. Here, power running refers to an operating state in which the motor 14 generates a positive torque. The powering prohibition process in step S2 will be described later.
[0042]
In step S3, the flag Fg is set to “0”. This flag Fg is referred to or reset in the powering prohibition process described later. It is assumed that the flag Fg is set to “0” even in the initial state.
[0043]
Next, in step S4, power running permission processing is performed. Here, the power running permission process is a process of enabling the input unit 62a of the switch unit 62 by the switch switching determination unit 64. Thus, the torque command value T is supplied to the motor 14 via the output interface 36 and the inverter 38, and the motor 14 rotates. At this time, the torque generated by the motor 14 is a torque corresponding to the speed deviation ε. As a result, the electric vehicle 10 runs at a speed corresponding to the speed command value c of the accelerator pedal 32.
[0044]
Next, in step S5, it is determined whether the accelerator pedal 32 is on or off. While the accelerator pedal 32 is on, the determination in step S5 is continuously performed. When the accelerator pedal 32 is off, the power running prohibition process of step S6 is performed, and then the current process ends.
[0045]
Next, the powering prohibition process will be described with reference to FIG. The powering prohibition process shown in the flowchart of FIG. 6 is executed in step S2 or step S6.
[0046]
First, in step S101 of FIG. 6, it is determined whether the torque command value T is positive and the flag Fg is “0”. If the torque command value T is positive and the flag Fg is “0”, the process proceeds to step S102, and if the torque command value T is negative or the flag Fg is “1”, Move to step S107. That is, in step S101, the processing is divided according to the torque command value T, and the execution of the processing after step S102 is restricted by the flag Fg.
[0047]
In step S102, the switch unit 62 is switched by the switch switching determination unit 64 to enable the input unit 62c.
[0048]
Next, in step S108, the torque command attenuator 60 generates a damping torque command value T2 along the pattern shown in FIG. Specifically, any one of the areas U1 to U4 is determined by measuring the time from the time t0 when the accelerator pedal 32 is turned off. Further, any one of the damping rates D1 to D4 is selected based on the areas U1 to U4 to generate the damping torque command value T2. For example, when the damping rate is D1, the amount by which the damping torque command value T2 decreases at one time is large, and when the damping rate is D4, the amount by which it decreases at one time is small.
[0049]
Next, in step S104, the speed command value c is forcibly made to match the vehicle speed v, and the speed deviation ε and the torque command value T are set to “0”. The result of this processing is used in steps S107 to S110.
[0050]
Next, in step S105, the positive / negative sign of the torque command value T output from the torque command attenuator 60 is confirmed. When the torque command value T is positive, the process returns to step S103, and the generation processing of the damping torque command value T2 is continued. When the damping torque command value T2 has become "0", the process proceeds to the next step S106.
[0051]
In step S106, the flag Fg is set to "1".
[0052]
Steps S102 to S106 are executed when the accelerator pedal 32 changes from on to off and the torque command value T is positive, as shown in FIG. At this time, the attenuation torque command value T2 gradually attenuates as shown by the attenuation line 70.
[0053]
During climbing a hill, a downward force due to its own weight acts on the electric vehicle 10. Therefore, if the torque acting as a force in the upward direction suddenly disappears, the electric vehicle 10 suddenly decelerates. Become. In the present embodiment, since the damping torque command value T2 is gradually attenuated as indicated by the damping line 70, it is possible to prevent sudden deceleration. Further, since the attenuation rate of the attenuation pattern increases with time, the speed can be reduced more smoothly.
[0054]
Since the attenuation rate of the attenuation line 70 increases with time and the attenuation torque command value T2 becomes "0" relatively quickly, even if the brake pedal 26 is turned on during this time, the effect on the braking operation is not affected. Extremely small.
[0055]
When the power running prohibition process is continuously performed by the loop of steps S1 and S2 (see FIG. 5), the execution of steps S102 to S106 is restricted by the set value of the flag Fg, so that only the first one is performed. Be executed. This is because, when the accelerator pedal 32 is turned off during climbing a hill, the speed command value c does not instantly become “0” as shown by the slope 72 in FIG. 3 and the deceleration due to its own weight is large during climbing. In this case, the speed command value c becomes larger than the vehicle speed v, and the vehicle is in a power running state. Therefore, the operation of steps S102 to S106 is restricted by the action of the flag Fg, and the processing of steps S107 to S110 is performed instead.
[0056]
At this time, since the speed deviation ε and the torque command value T are previously set to “0” in step S104, no rapid acceleration / deceleration occurs when the process is switched.
[0057]
On the other hand, when the torque command value T is negative or the flag Fg is “1” in step S101, the process proceeds to step S107. In this step S107, the switch unit 62 is switched by the switch switching determination unit 64 to make the input unit 62b valid.
[0058]
Next, in step S108, the sign of the torque command value T is confirmed. When the torque command value T is positive, the process proceeds to step S109. Since the torque command value T is obtained by multiplying the speed deviation ε by the gain, the branch destination may be determined in step S108 based on the sign of the speed deviation ε. In step S109, the torque command value T is limited to "0" to generate a limited torque command value T1.
[0059]
In the next step S110, a process of substituting the vehicle speed v for the speed command value c and setting the speed deviation ε to 0 is performed.
[0060]
Steps S107 to S110 are executed when the accelerator pedal 32 changes from on to off and the torque command value T is negative, as shown in FIG. At this time, the speed command value c decreases with a predetermined slope, similarly to the slope 72 in FIG. If the driver steps on the brake pedal 26 (see FIG. 1) before the speed command value c decreases to “0”, the brake drum 24 operates and the electric vehicle 10 decelerates.
[0061]
At this time, the magnitude relationship between the speed command value c and the vehicle speed v may be reversed, and the speed command value c may be larger than the vehicle speed v. In this case, since the state of the brake pedal 26 is not detected in the ECU 12, the speed deviation ε becomes a positive value, and the torque command unit 56 outputs a positive value and supplies the output to the input unit 62a. If the motor 14 is rotated using the positive value supplied to the input unit 62a, a positive torque is generated in the motor 14, and the operation is contrary to the intention of the driver who is trying to decelerate. is there.
[0062]
In the present embodiment, the input unit 62a of the switch unit 62 is disabled and the input unit 62b is enabled by the processing in step S107. The input unit 62b is connected to the positive torque limiting unit 58 corresponding to steps S108 to S110, and supplies the limited torque command value T1 in which the positive value is limited to “0”, so that there is no inconvenience as described above. . That is, the motor 14 does not perform power running even if the speed command value c becomes larger than the vehicle speed v while the vehicle is decelerating by depressing the brake pedal 26.
[0063]
After the processing in steps S106 and S110 or when the torque command value T is negative in step S108, the current processing ends.
[0064]
When the torque command value T is negative in step S108, regenerative braking may be performed using a regenerative charging device (not shown).
[0065]
As described above, according to the motor control method for the electric vehicle according to the present embodiment, when the accelerator pedal 32 is turned off and the torque command value T is positive, the damping torque is determined according to the predetermined damping pattern. Since the command value T2 is changed to "0", it is possible to prevent a sudden change in the torque and smoothly reduce the speed.
[0066]
Further, when the accelerator pedal 32 is turned off and the torque command value T is negative, a limited torque command value T1 that limits the torque command value T to a value of 0 or less is supplied while the accelerator pedal 32 is off. are doing. Therefore, when the brake pedal 26 is depressed to decelerate, the electric vehicle 10 can be surely decelerated without the power running of the motor 14.
[0067]
Furthermore, according to the motor control method for the electric vehicle according to the present embodiment, the driver does not need to perform the switching operation of the motor control method, so that the switching operation is not troublesome. In addition, since an appropriate motor control method is selected according to the situation, stable operation is possible. A switch for switching the motor control method is not required.
[0068]
In the electric vehicle 10, since the braking is performed by the brake drum 24, which is one of the mechanical brakes, an electromagnetic brake and its control means are unnecessary. Further, the brake pedal 26 does not require a brake switch or a volume for detecting the depression amount. Therefore, the braking system of the electric vehicle 10 can be made inexpensive.
[0069]
The motor control method of the electric vehicle according to the present invention is not limited to the above-described embodiment, but may adopt various configurations without departing from the gist of the present invention.
[0070]
【The invention's effect】
As described above, according to the motor control method for an electric vehicle according to the present invention, it is not necessary for the driver to perform a switching operation of the motor control method, and the number of components of the braking system can be reduced. In addition, the braking system of the electric vehicle can be configured to be inexpensive.
[0071]
Further, even if the operation amount of the brake is not detected, a stable operation can be performed without generating a positive torque by the motor during the brake operation.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a driving / braking system of an electric vehicle.
FIG. 2 is a block diagram of an ECU and related devices.
FIG. 3 is a time chart showing changes in input / output signals of a speed command converter.
FIG. 4 is a time chart of a torque command value attenuated in a torque command attenuator.
FIG. 5 is a flowchart illustrating a motor control method for the electric vehicle according to the present embodiment.
FIG. 6 is a flowchart illustrating a powering prohibition processing method.
FIG. 7 is a time chart showing a torque command value, a speed command value, and a vehicle speed when the sign of the torque command value is negative when the operation amount of the accelerator pedal is returned to 0;
FIG. 8 is a time chart showing a torque command value, a speed command value, and a vehicle speed when the sign of the torque command value is positive when the operation amount of the accelerator pedal is returned to 0;
[Explanation of symbols]
10: electric vehicle 12: ECU
14 ... Motor 24 ... Brake drum 26 ... Brake pedal 28 ... Program 30 ... CPU 32 ... Accel pedal 34 ... Volume 38 ... Inverter 40 ... Battery 42 ... Rotation speed detection sensor 50 ... On / off judgment unit 52 ... Speed command conversion unit 54 ... subtraction point 56 ... torque command unit 58 ... positive torque limiting unit 60 ... torque command attenuating unit 62 ... switch units 62a, 62b, 62c ... input unit 64 ... switch switching judgment unit e ... speed deviation c ... speed command value T ... torque Command value T1: Limited torque command value T2: Damping torque command value v: Vehicle speed

Claims (4)

A motor control method for an electric vehicle that calculates a torque command value based on a speed command value corresponding to an accelerator operation amount and a traveling speed of the electric vehicle and drives a motor for traveling in accordance with the torque command value,
When the operation amount of the accelerator is returned to 0, when the sign of the torque command value is positive, the torque command value is changed to 0 along a predetermined attenuation pattern,
When the operation amount of the accelerator is 0 and the torque command value is 0 or less, the torque command value is limited to a value of 0 or less. The motor control method for an electric vehicle according to claim 1,
The motor control method for an electric vehicle, wherein the damping pattern is a pattern in which a damping rate of the torque command value increases with time with reference to the torque command value. The motor control method for an electric vehicle according to claim 2,
The motor control method for an electric vehicle, wherein the damping pattern is represented by connecting a plurality of straight lines by a section based on a torque command value at the start of application of the damping pattern and a section of time. The motor control method for an electric vehicle according to any one of claims 1 to 3,
An electric vehicle characterized in that the number of executions of the process of changing the torque command value to 0 along the damping pattern is limited so that the process is performed only once while the operation amount of the accelerator is zero. Motor control method.

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