JP2011134184A - Motor control device for driving automatic traveling vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control device for driving an automatic traveling vehicle, which stably drives the automatic traveling vehicle while preventing slip of wheels of the automatic traveling vehicle. <P>SOLUTION: The motor control device includes: a motor speed detection means 11 which obtains a motor speed of a motor 4 for driving the automatic traveling vehicle; a vehicle body speed detection means 12 which obtains a vehicle body speed of the automatic traveling vehicle; a speed control means 10 which controls the motor 4 so that the motor speed follows a command corresponding to a speed command for controlling the motor speed; and a speed command limiting means 13 which receives the speed command from a host and, when the speed commanded by the speed command is within a predetermined speed range, outputs the speed command to the speed control means as it is and, when the speed commanded by the speed command is outside the predetermined speed range, corrects the speed command to fall within the speed range and outputs the corrected speed command to the speed control means as a limited speed command. The speed command limiting means 13 calculates an upper limit value and a lower limit value of the speed range on the basis of the vehicle body speed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a motor control device that drives an automatic traveling vehicle, and more particularly to a motor control device that stably drives an automatic traveling vehicle while suppressing slippage of wheels of the automatic traveling vehicle.

Among automatic traveling vehicles, it is desired to reduce the transport time of an automatic guided vehicle that transports goods unattended, in order to improve transport efficiency. For this reason, it is required to increase the moving speed and shorten the acceleration / deceleration time.
However, in order to shorten the acceleration / deceleration time, if the automatic guided vehicle is operated with increased acceleration and deceleration, the automatic guided vehicle wheels may slip depending on the condition of the traveling surface such as the floor and rails, and the traveling may become unstable. There was a problem to say.

  For this reason, for example, Patent Document 1 detects whether or not a wheel is slipping. If it is determined that the wheel is slipping, acceleration and deceleration are reduced, and if it is determined that the slip has been resolved, acceleration is detected. A method for returning the deceleration to the original value has been proposed.

Japanese Patent Laid-Open No. 2002-202816 (pages 7-8, FIGS. 4 and 5)

  However, in the technique described in Patent Document 1, it is necessary to provide means for detecting the slip state between the wheel of the transport vehicle and the traveling surface, and to constantly monitor the slip state. Moreover, since acceleration and deceleration are reduced after detecting an excessive slip state, the excessive slip state itself cannot be avoided in advance. Furthermore, if the wheel is slipping excessively, the acceleration and deceleration are reduced to eliminate the excessive slip condition, but since the acceleration and deceleration were increased thereafter, an excessive slip condition occurs again. There is a problem that there is a fear that an excessive slip state may repeatedly occur or be resolved.

  The present invention has been made to solve such a problem, and is an automatic traveling vehicle drive motor capable of stably traveling an automatic traveling vehicle by suppressing slippage between wheels and a traveling surface of the automatic traveling vehicle. The purpose is to obtain a control device.

  The motor controller for driving an automatic vehicle according to the present invention includes a motor speed detecting means for obtaining and outputting a motor speed of a motor for driving the automatic vehicle, and a vehicle speed detecting for obtaining and outputting the vehicle speed of the automatic vehicle. A command according to a speed command for controlling the motor speed, a speed control unit for controlling the motor so that the motor speed follows the command, and the speed command from a higher order. When the speed commanded by the speed command is within a predetermined speed range, the speed command is output as it is to the speed control means, and when the speed commanded by the speed command is not within the speed range, A speed command limiting means for correcting the command speed to a speed within the speed range and outputting the corrected speed command to the speed control means as a speed limit command, the speed command limiting means The upper and lower limits of the speed range, and calculates on the basis of the vehicle speed input from the vehicle speed detecting means.

  According to this invention, in order to control an autonomous vehicle, the speed (command speed) commanded by the speed command for controlling the motor speed input from the host is set to a speed within the speed range calculated based on the vehicle body speed. Since it is limiting, the difference between the vehicle body speed and the wheel speed, that is, the slip ratio can be suppressed within a range in which the slip is suppressed. As a result, it is possible to avoid an excessive slip state without always monitoring the slip state by providing a means for detecting the slip state between the wheel of the autonomous vehicle and the traveling surface, and being always stable. It is possible to drive an autonomous vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an automatic vehicle driving motor control device showing Embodiment 1 of the present invention. It is a figure which shows the relationship between the slip ratio of the wheel which concerns on the motor controller for motor vehicles drive which shows Embodiment 1 of this invention, and the frictional force of a wheel. It is a block diagram which shows the speed command restriction | limiting means of the motor controller for motor vehicles for automatic traveling vehicles which shows Embodiment 1 of this invention. It is a block diagram which shows the speed command restriction | limiting means of the motor controller for motor vehicles for automatic traveling vehicles which shows Embodiment 2 of this invention. It is a figure which shows the relationship between the vehicle body and the speed difference of a wheel, and the frictional force of a wheel concerning the motor control apparatus for automatic vehicle driving which shows Embodiment 2 of this invention. It is a block diagram which shows the speed command restriction | limiting means of the motor controller for motor vehicles for automatic traveling vehicles which shows Embodiment 3 of this invention.

DESCRIPTION OF SYMBOLS 1 Car body, 2 Drive wheel, 3 Drive wheel, 4 Motor, 5 Encoder, 6 Drive wheel rotation detector, 10 Speed control means, 11 Motor speed detection means, 12 Car body speed detection means, 13, 13a, 13b Speed command limitation means , 20, 40 Absolute value calculation means, 21, 41 Multiplication means, 22, 31, 42 Addition means, 23, 32, 43 Subtraction means, 24, 44 limiter, 45 Maximum value calculation means.

Embodiment 1 FIG.
FIG. 1 shows an automatic vehicle driving motor control apparatus according to Embodiment 1 for carrying out the present invention. Reference numeral 1 denotes a vehicle body of an automatic traveling vehicle, 2 denotes a wheel of the automatic traveling vehicle, which is a driving wheel driven by a motor described later, and 3 is also a wheel of the automatic traveling vehicle, but is automatically driven without being driven by a motor described later. A driven wheel that is passively rotated as the traveling vehicle travels, 4 is a motor that drives the drive wheel 2, 5 is an encoder that detects the rotational position of the motor 4, and 6 is a slave that detects the rotational position of the driven wheel 3. A driving wheel rotation detector 10 is a speed control means for controlling the speed of the motor 4 by changing a value of a motor driving current (motor driving current) output to the motor 4, and 11 is a motor control signal output from the encoder 5. Motor speed detecting means 12 for determining the motor speed from the rotational position information, 12 is the speed of the driven wheel 3, that is, the speed of the vehicle body 1 (vehicle speed) from the rotational position information of the driven wheel 3 output from the driven wheel rotation detector 6. Required vehicle speed The detection means 13 inputs a speed command for controlling a motor speed given from a host controller or a position controller (not shown) in order to control the autonomous vehicle, and further determines the vehicle speed from the vehicle speed detection means 12. This is a speed command limiting means for limiting the speed (command speed) commanded by the speed command within the speed range calculated based on the vehicle body speed and outputting it as a speed limit command.

In order to explain the operation of the present invention, first, the frictional force between the wheels of the autonomous vehicle and the traveling surface will be described. FIG. 2 is a graph showing the relationship between the slip ratio between the wheel and the running surface and the frictional force. The slip ratio is a numerical value representing the magnitude of slip. The slip ratio λ is obtained by dividing the difference | Vw−Vb | between the driving wheel speed Vw and the vehicle body speed (speed of the driven wheel 3) Vb by the vehicle body speed Vb, and is expressed by the following equation (1). .
λ = | Vw−Vb | / Vb (1)

In the relationship between the slip rate and the friction force between the wheel and the running surface shown in FIG. 2, the friction force gradually increases until the slip rate reaches the value of the slip rate that causes the maximum friction force (region A). When the slip rate becomes larger than the value of the slip rate causing the maximum friction force, the friction force decreases for a while (region B).
Therefore, in the region A, even if the vehicle speed of the autonomous vehicle increases and the slip rate temporarily increases, the frictional force between the wheels and the running surface increases, so the slip rate shifts in a decreasing direction thereafter, In order to settle down to an appropriate slip rate, the autonomous vehicle can travel stably.
On the other hand, in the region B, when the vehicle speed of the autonomous vehicle increases and the slip rate temporarily increases, the frictional force between the wheels and the running surface decreases and the wheels become slippery. Therefore, the slip rate further increases. This shifts and the traveling of the autonomous vehicle becomes unstable.

  From the above, in order to drive the autonomous vehicle stably, the speed of the driving wheel 2, that is, the speed of the motor 4 is controlled so that the wheel is driven in a state where the slip ratio is in the region A shown in FIG. I understand that

The operation of the automatic vehicle driving motor control apparatus according to the first embodiment will be described.
The motor 4 is driven by the motor drive current output from the speed control means 10, and the motor 4 drives the drive wheels 2, so that the autonomous vehicle travels. At this time, the rotational position of the driven wheel 3 that is passively rotated as the autonomous vehicle travels is detected by the driven wheel rotation detector 6, and the output of the driven wheel rotation detector 6 is input to the vehicle body speed detection means 12. Thus, the speed of the driven wheel 3 is detected as the vehicle speed of the automatic traveling vehicle. The vehicle body speed is output to the speed command limiting means 13. The speed command limiting means 13 inputs the vehicle body speed output from the vehicle body speed detecting means 12 and a speed command for controlling the motor speed from a host control device in order to control the automatic traveling vehicle. The speed range is calculated based on the speed, the speed commanded by the speed command (command speed) is limited to the speed within the calculated speed range, and the limited speed command is output to the speed control means 10 as the speed limit command. . The speed control means 10 inputs a speed limit command, inputs a signal from the encoder 5 and detects the speed of the motor 4, and the motor speed input from the motor speed detection means 11 follows the command speed of the speed limit command. Thus, the motor drive current value output to the motor 4 is adjusted to control the motor 4.

Next, the speed command limiting means 13 will be described.
FIG. 3 is a block diagram showing details of the speed command limiting means 13. In FIG. 3, reference numeral 20 denotes an absolute value calculating means for inputting the vehicle body speed Vb obtained by the vehicle body speed detecting means 12, and calculating and outputting the absolute value | Vb |. A multiplication means 21 multiplies the absolute value | Vb | of the vehicle speed inputted from the absolute value calculation means 20 by a coefficient K, and outputs K | Vb |. Here, the coefficient K is a coefficient larger than a preset zero, and will be described in detail later. Further, 22 is an adding means, which adds the vehicle body speed Vb to the output of the multiplying means 21 and outputs Vb + K | Vb |. A subtracting unit 23 subtracts the output of the multiplying unit 21 from the vehicle body speed Vb and outputs Vb−K | Vb |. Reference numeral 24 denotes limiter means for inputting the output from the adding means 22 as the upper limit value of the command speed of the speed command, and inputting the output from the subtracting means 23 as the lower limit value of the command speed of the speed command. The command speed of the command is limited to a range between the upper limit value and the lower limit value, and is output as a speed limit command. Specifically, if the command speed of the speed command is within the speed range, the input speed command is output as it is, and if the command speed of the speed command is not within the speed range, the command speed is changed to a speed within the speed range. And the corrected speed command is output as a speed limit command. For example, when a speed command whose command speed exceeds the upper limit value is input to the limiter means 24, a speed command whose command speed is equal to the upper limit value is output as a speed limit command, or a speed command whose command speed is lower than the lower limit value When input to the means 24, a speed command having a command speed equal to the lower limit value is output as a speed limit command.

  The speed command limiting means 13 limits the command speed of an arbitrary speed command input from the host controller as described above to a range between Vb−K | Vb | and Vb + K | Vb | and outputs it as a speed limit command. . The speed control means 10 receives this speed limit command and controls the motor 4 so that the motor speed obtained by the motor speed detection means 11 follows the speed limit command. Therefore, the motor speed is also controlled to fall within this range. The

Here, the value of the coefficient K will be described.
Since the driving wheel speed Vw is limited by the speed command limiting means 13, it is in the following range.
Vb−K | Vb | ≦ Vw ≦ Vb + K | Vb | (2)
Therefore, the range of the coefficient K greater than zero is as follows.
K ≧ | Vw−Vb | / Vb (3)
Since the right side of the equation (3) represents the slip ratio, if the value of the coefficient K is set to a value equal to or less than the slip ratio λm when the frictional force is maximized or a value close to λm, the slip ratio is reduced. In the area A shown in FIG. 2, it can be prevented from entering the area B. As a result, the slip state of the drive wheel 2 can be stabilized.

  Since the value of λm generally exists in a range where the slip ratio is about 10 to 20%, it may be an arbitrary value within this range. In addition, a value obtained by measuring in advance the relationship between the slip ratio and the frictional force may be used for the wheels and the traveling surface of the automatic traveling vehicle that is an actual control target.

  According to the automatic vehicle driving motor control apparatus shown in this embodiment, the speed command limit means 13 calculates the range of the command speed of the speed command based on the vehicle body speed, and is inputted arbitrarily from the host controller. Since the command speed of the speed command is limited within the calculated speed range, an excessive slip state does not occur. Therefore, it is possible to prevent an excessive slip state without always monitoring the slip state by providing a means for detecting the slip state between the wheel of the autonomous vehicle and the traveling surface, and always running automatically and stably. It is possible to drive the car.

Embodiment 2. FIG.
FIG. 4 is a block diagram showing details of speed command limiting means in the motor controller for an automatic traveling vehicle drive according to Embodiment 2 of the present invention. In the automatic vehicle driving motor control apparatus according to the second embodiment, the configuration other than the speed command limiting means is the same as the configuration shown in FIG.

The speed command limiting means 13a according to the second embodiment will be described.
In FIG. 4, ΔV is a constant larger than zero set in advance in the speed command limiting means 13a, and is an allowable speed that indicates a speed difference between the allowable vehicle body speed and the motor speed. Reference numeral 31 denotes addition means for adding ΔV to the vehicle body speed Vb and outputting Vb + ΔV as an upper limit value of the command speed of the speed command. A subtracting means 32 subtracts ΔV from the vehicle body speed Vb and outputs Vb−ΔV as a lower limit value of the command speed of the speed command. A limiter means 33 limits the command speed of the speed command between an upper limit value and a lower limit value, and outputs the limited speed command as a speed limit command. Specifically, if the command speed of the speed command is within the speed range, the input speed command is output as it is, and if the command speed of the speed command is not within the speed range, the command speed is changed to a speed within the speed range. And the corrected speed command is output as a speed limit command. For example, when a speed command whose command speed exceeds the upper limit value is input to the limiter means 33, a speed command whose command speed is equal to the upper limit value is output as a limit speed command, or a speed command whose command speed is lower than the lower limit value When input to the means 33, a speed command having a command speed equal to the lower limit value is output as a speed limit command.

  Here, in FIG. 2 in the first embodiment, the frictional force between the wheel and the running surface is expressed as a function of the slip ratio. However, depending on the floor surface and the wheel material as the running surface, the frictional force is a function of the slip rate. Instead, it may be a function of the speed difference between the vehicle body and the wheel as shown in FIG.

In the relationship between the speed difference between the vehicle body and the wheel and the friction force between the wheel and the running surface shown in FIG. 5, the speed difference between the vehicle body and the wheel is smaller than the speed difference between the vehicle body and the wheel when the maximum friction force is generated. In the range (A ′ region), the frictional force increases as the speed difference between the vehicle body and the wheel increases. In the range where the speed difference between the vehicle body and the wheel is larger than the speed difference between the vehicle body and the wheel where the maximum frictional force is generated (B ′ region), the friction force decreases as the speed difference between the vehicle body and the wheel increases.
Therefore, in the region A ′, even if the vehicle speed of the automatic traveling vehicle increases and the speed difference between the vehicle body and the wheel temporarily increases, the frictional force between the wheel and the traveling surface increases. Since the difference shifts in the direction of decreasing and settles to an appropriate speed difference between the vehicle body and the wheels, the autonomous vehicle can travel stably.
On the other hand, in the region B ′, if the vehicle speed of the automatic traveling vehicle increases and the speed difference between the vehicle body and the wheel temporarily increases, the frictional force between the wheel and the traveling surface decreases and the wheel becomes slippery. It shifts in the direction in which the speed difference of the wheels increases, and the traveling of the autonomous vehicle becomes unstable.

  From the above, in order to drive the automatic traveling vehicle stably, the speed of the driving wheel 2, that is, the motor 4 is driven in order to drive the wheel in a state where the speed difference between the vehicle body and the wheel is in the region A 'shown in FIG. It can be seen that it is sufficient to control the speed.

  As described above, the speed command limiting means 13a limits an arbitrary speed command input from the host controller to a range between Vb−ΔV and Vb + ΔV, and outputs it as a speed limit command. The speed control means 10 receives this speed limit command and controls the motor 4 so that the motor speed obtained by the motor speed detection means 11 follows the speed limit command. Therefore, the motor speed is also controlled to fall within this range. The

Here, the allowable speed difference ΔV will be described.
Since the driving wheel speed Vw is limited by the speed command limiting means 13, it is in the following range.
Vb−ΔV ≦ Vw ≦ Vb + ΔV (4)
Therefore, the range of ΔV that is greater than zero is as follows.
ΔV ≧ | Vw−Vb | (5)
Since the right side of equation (5) represents the speed difference between the vehicle body and the wheel, if the value of ΔV is set to a value equal to or less than the speed difference ΔVm at which the frictional force is maximum, And the speed difference between the wheels is in the area A ′ shown in FIG. 5 and can be prevented from entering the area B ′. As a result, the slip state of the drive wheel 2 can be stabilized.

  As the value of ΔVm, a value obtained by measuring in advance the relationship between the speed difference between the vehicle body and the wheel and the frictional force on the wheel and the running surface of the automatic traveling vehicle that is the actual control target is used.

  According to the automatic vehicle driving motor control device shown in this embodiment, even if the frictional force between the wheel and the running surface is not a function of the slip ratio but a function of the speed difference between the vehicle body and the wheel, The effect similar to the form 1 of this can be acquired. In other words, the speed command limiting means 13a calculates the speed command range of the speed command based on the vehicle body speed, and limits the command speed of any speed command input from the host control device within the calculated speed range. Therefore, an excessive slip state does not occur. Therefore, it is possible to prevent an excessive slip state without always monitoring the slip state by providing a means for detecting the slip state between the wheel of the autonomous vehicle and the traveling surface, and always running automatically and stably. It is possible to drive the car.

Embodiment 3 FIG.
FIG. 6 is a block diagram showing details of speed command limiting means in the motor controller for driving an automatic traveling vehicle according to Embodiment 3 of the present invention. In the motor control device for driving an automatic traveling vehicle according to the third embodiment, the configuration other than the speed command limiting means is the same as the configuration shown in FIG.

The speed command limiting means 13b according to Embodiment 3 will be described.
In FIG. 6, reference numeral 40 denotes an absolute value calculating means for obtaining and outputting the absolute value | Vb | of the vehicle body speed Vb obtained by the vehicle body speed detecting means 12. Reference numeral 41 denotes multiplication means for multiplying the absolute value | Vb | of the vehicle body speed by a preset coefficient K greater than zero and outputs K | Vb |. 45 is a maximum value calculating means for comparing K | Vb |, which is the output of the multiplying means 41, with a preset allowable speed difference ΔV greater than zero and outputting the larger of both as ΔVn. An adding means 42 adds ΔVn to the vehicle body speed Vb, and outputs Vb + ΔVn as the upper limit value of the speed command. A subtracting means 43 subtracts ΔVn from the vehicle body speed Vb and outputs Vb−ΔVm as a lower limit value of the command speed of the speed command. 44 is a limiter means for limiting the command speed of the speed command between the upper limit value and the lower limit value, and outputting the limited speed command as a speed limit command. Specifically, if the command speed of the speed command is within the speed range, the input speed command is output as it is, and if the command speed of the speed command is not within the speed range, the command speed is changed to a speed within the speed range. And the corrected speed command is output as a speed limit command.

  The speed command limiting means 13b shown in FIG. 6 has both the function of the speed command limiting means 13 shown in FIG. 3 and the function of the speed command limiting means 13a shown in FIG. That is, in the speed command limiting means 13, a maximum value calculating means is provided between the multiplying means 21, the adding means 22 and the subtracting means 23. The maximum value calculating means compares K | Vb |, which is the output of the multiplying means, with a preset allowable speed difference ΔV greater than zero, and outputs the larger of them as ΔVn, and the vehicle speed using ΔVn. Based on Vb, an upper limit value and a lower limit value of the command speed of the speed command are calculated.

If the value of the coefficient K is set to a value equal to or less than the slip rate λm when the frictional force is maximum or a value close to λm, the slip rate is in the region A shown in FIG. Can be. As a result, the slip state of the drive wheel 2 can be stabilized.
Further, if the value of ΔV is set to a value less than or equal to the speed difference ΔVm at which the frictional force is maximum, the speed difference between the vehicle body and the wheel is in the region A ′ shown in FIG. You can avoid entering the area. As a result, the slip state of the drive wheel 2 can be stabilized.

  By configuring the speed command limiting means 13b as shown in FIG. 6, even when the frictional force between the wheel and the running surface can be expressed as a function of the slip ratio as shown in FIG. 2, the speed difference between the vehicle body and the wheel as shown in FIG. Even if it can be expressed as a function of, both cases can be handled. Further, if the coefficient K is set to zero or a value close to zero, control equivalent to that in the first embodiment can be realized. If ΔV is set to zero or a value close to zero, control equivalent to that in the second embodiment can be realized. This makes it possible to stabilize the slip state of the drive wheels 2 in accordance with various floor conditions and wheel materials.

  According to the motor controller for driving an autonomous vehicle shown in this embodiment, even when the frictional force between the wheel and the running surface is a function of the slip ratio, it is a function of the speed difference between the vehicle body and the wheel. Even so, the same effect as in the first embodiment can be obtained. That is, the speed command limit means 13b calculates the speed command speed range based on the vehicle body speed, and limits the speed command speed input from the host controller to the calculated speed range. Therefore, an excessive slip state does not occur. Therefore, it is possible to prevent an excessive slip state without always monitoring the slip state by providing a means for detecting the slip state between the wheel of the autonomous vehicle and the traveling surface, and always running automatically and stably. It is possible to drive the car.

  The motor controller for driving an autonomous vehicle according to the present invention is suitable for stably running an autonomous vehicle.

Claims (6)

Motor speed detecting means for obtaining and outputting a motor speed of a motor for driving the automatic traveling vehicle;
Vehicle body speed detecting means for obtaining and outputting a vehicle body speed of the autonomous vehicle;
A speed control means for inputting a command according to a speed command for controlling the motor speed, and controlling the motor so that the motor speed follows the command;
When the speed command is input from the host and the speed commanded by the speed command is within a predetermined speed range, the speed command is output as it is to the speed control means, and the speed commanded by the speed command is If not within the range, the command speed is corrected to a speed within the speed range, and the corrected speed command is output to the speed control means as a speed limit command;
A motor control device for driving an automatic vehicle equipped with
The motor control device for driving an automatic vehicle, wherein the speed command limiting means calculates an upper limit value and a lower limit value of the speed range based on the vehicle body speed input from the vehicle body speed detection means.   When the vehicle body speed is Vb, the absolute value of the vehicle body speed is | Vb |, and a coefficient larger than a preset zero is K, the speed command limiting means sets the lower limit value of the speed range to Vb−K. 2. The motor controller for driving an automatic vehicle according to claim 1, wherein | Vb | and an upper limit value of the speed range are calculated as Vb + K | Vb |. When the vehicle body speed is Vb, a value larger than a preset zero, and a permissible differential speed which is a speed difference between the allowable vehicle body speed and the motor speed is ΔV,
2. The motor controller for driving an automatic vehicle according to claim 1, wherein the speed command limiting means calculates the lower limit value of the speed range as Vb- [Delta] V and the upper limit value of the speed range as Vb + [Delta] V. The vehicle body speed is Vb, the absolute value of the vehicle body speed is | Vb |, a coefficient larger than a preset zero is K, and a value larger than a preset zero, and the allowable vehicle body speed and the motor are allowed. When the tolerance speed, which is the speed difference from the speed, is ΔV, and the larger value of ΔV and K | Vb | is ΔVn,
2. The motor controller for driving an automatic vehicle according to claim 1, wherein the speed command limiting means calculates the lower limit value of the speed range as Vb- [Delta] Vn and the upper limit value of the speed range as Vb + [Delta] Vn.   The motor speed is Vw, the absolute value of the difference between the motor speed and the vehicle body speed is | Vw−Vb |, the slip ratio λ between the autonomous vehicle and the traveling surface is | Vw−Vb | / Vb, and the drive wheel 3. The automatic traveling vehicle according to claim 2, wherein the speed command limiting means sets the coefficient K to λm or less when a slip ratio when the frictional force between the vehicle and the traveling surface becomes maximum is λm. Drive motor control device.   The speed of the driving wheel driven by the motor is Vw, the absolute value of the difference between the speed of the driving wheel and the vehicle body speed is | Vw−Vb |, and the frictional force between the driving wheel and the running surface is maximized. 4. The motor controller for driving an automatic traveling vehicle according to claim 3, wherein when the difference between the speed of the driving wheel and the vehicle body speed is ΔVm, the allowable speed difference ΔV is equal to or less than ΔVm. .

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