JP2014103815A - Motor drive device for forklift and electric forklift using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric forklift preventing a side slip, collapse of cargo and so on and reduce unpleasantness given to an operator.SOLUTION: In an electric forklift based on a front-wheel-drive and rear-wheel-steering system, a speed distribution portion 200 calculates a speed command value according to an operation of an operator and speed command values Vrref and Vlref instructing speeds of right and left running motors M1R and M1L, respectively, on the basis of a steering angle of the steering wheel of the electric forklift. A torque command value creation portion 202 creates torque command values Trcom and Tlcom instructing torques of the right and left running motors. Acceleration acquisition means 230 acquires accelerations αry and αly in the body lateral direction at individual positions of the right and left driving wheels. A torque correction portion 240 corrects at least one of the right torque command value Trcom and the left torque command value Tlcom according to a difference between the right acceleration αry and the left acceleration αly.

Description

  The present invention relates to a motor drive device for a forklift.

  One of the industrial vehicles is an electric forklift that uses a battery as a power source. An electric forklift (hereinafter simply referred to as a forklift) is a traveling motor that transmits power to a front wheel that is a traveling wheel (driving wheel) and a hydraulic pump that controls a turning angle (steering angle) of a rear wheel that is a steered wheel. Hydraulic actuator motor (steering motor) that transmits power, hydraulic actuator motor (loading motor) that transmits power to the hydraulic pump that controls the lifting body, and power conversion that drives each of the travel motor, steering motor, and cargo handling motor Equipment.

  Forklifts, unlike ordinary vehicles traveling in a predetermined lane, are often used with a large turning angle in a free space, that is, with a small turning radius, and may also be used in fields with poor road surface conditions. is assumed. In addition to this situation, due to its structural characteristics of loading heavy loads in front of the vehicle, forklifts tend to fluctuate yaw moment around the center of gravity of the vehicle during travel, causing side slipping, load collapse, etc. , The driver may be uncomfortable.

  Patent Document 1 discloses a technique in which a yaw sensor using a gyro sensor is arranged at the center of gravity of a vehicle in a four-wheel drive vehicle, and the yaw moment is controlled based on a yaw rate signal obtained from the yaw sensor.

JP 2006-33927 A

  On the other hand, front-wheel drive and rear-wheel steering type electric forklifts, especially dual motor type electric forklifts that have independent motors for the right and left drive wheels, and the rotation speed and rotation direction of each can be controlled independently. The technique disclosed in Patent Document 1 cannot be applied as it is.

  The present invention has been made in such a situation, and one of the exemplary purposes of an aspect thereof is to provide a technique for preventing side slip, collapse of a load, etc. or reducing discomfort given to a driver in an electric forklift. It is in.

  An aspect of the present invention is a left traveling motor that is mounted on a front wheel drive and rear wheel steering type forklift and transmits power to each of the left drive wheel and the right drive wheel of the forklift based on a speed command value indicating a target speed of the forklift. The present invention also relates to a motor driving device that controls a right traveling motor. The motor drive device has a left speed command value for instructing the speed of the left travel motor and a right speed for instructing the speed of the right travel motor based on the speed command value according to the operation of the driver and the turning angle of the steered wheels of the forklift. A speed distribution unit that calculates a command value, and generates a left torque command value that indicates the torque of the left traveling motor according to an error between the left speed command value and the current speed of the left traveling motor; Torque command value generation unit for generating a right torque command value for instructing the torque of the right traveling motor according to an error in the current speed of the right traveling motor, and ground acceleration in the lateral direction of the vehicle body at the coordinates of the ground point of the left driving wheel And a left torque finger according to the difference between the left acceleration and the right acceleration according to the difference between the left acceleration and the right acceleration. It comprises a torque correcting unit for correcting at least one value and the right torque command value.

  According to this aspect, by detecting the lateral acceleration of the vehicle at the position of each of the left driving wheel and the right driving wheel, and correcting the torque of the left and right driving wheels according to the result, side slip, load collapse, etc. are prevented, Or the discomfort given to a driver | operator can be reduced.

  The torque correction unit may add or subtract a correction value obtained by multiplying a difference between the left acceleration and the right acceleration by a predetermined coefficient to at least one of the left torque command value and the right torque command value.

  The torque correction unit may subtract a correction value corresponding to the difference from the torque command value of the driving wheel serving as the outer wheel.

The torque correction unit may correct at least one of the left torque command value and the right torque command value when the difference is larger than a predetermined threshold value.
In this case, excessive yaw moment control can be suppressed by appropriately setting the threshold value.

  The acceleration acquisition means is provided on the vertical line of the grounding point of the left driving wheel, and is provided on the vertical line of the left speed sensor for detecting the ground speed in the lateral direction of the vehicle and the grounding point of the right driving wheel. You may include the right speed sensor which detects the ground speed of a direction, and the calculator which differentiates the output of each of the left speed sensor and the right speed sensor. A primary high-pass filter may be used for the differentiation process.

  The acceleration acquisition means is provided at a predetermined position of the vehicle, detects a ground speed in each of the lateral direction of the vehicle and the longitudinal direction of the vehicle body at the position, a ground speed in the lateral direction of the vehicle at the predetermined position, And a computing unit that calculates the lateral acceleration in the vehicle lateral direction at the coordinates of the grounding point of the left driving wheel and the ground acceleration in the lateral direction of the vehicle at the coordinate of the grounding point of the right driving wheel based on the ground speed.

  Another aspect of the present invention relates to an electric forklift. The electric forklift includes a left driving wheel and a right driving wheel, a left traveling motor and a right traveling motor that transmit power to the left driving wheel and the right driving wheel, and the motor driving device described above that drives the left traveling motor and the right traveling motor. And comprising.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the side slip of an electric forklift, load collapse, etc. can be prevented, or the discomfort given to a driver | operator can be reduced.

It is a perspective view which shows the external view of the electric wheel forklift of a front wheel drive and a rear-wheel steering type. It is a figure which shows an example of the control panel of a forklift. It is a block diagram which shows the structure of the electric system of a dual motor type forklift, and a mechanical system. FIGS. 4A and 4B are views schematically showing a dual motor type forklift. It is a block diagram which shows the structure of the motor drive device (1st power converter device) which concerns on embodiment. FIG. 6A is a block diagram illustrating a configuration example of the acceleration acquisition unit, and FIG. 6B is a diagram illustrating the arrangement of the sensors. FIG. 7A is a block diagram showing the configuration of the acceleration acquisition means according to the first modification, and FIG. 7B is a diagram showing the arrangement of the sensors.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, “the state in which the member A is connected to the member B” means that the member A and the member B are electrically connected to each other in addition to the case where the member A and the member B are physically directly connected. It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.
Similarly, “the state in which the member C is provided between the member A and the member B” refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as their electric It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.

  FIG. 1 is a perspective view showing an external view of a front wheel drive and rear wheel steering type electric forklift. The forklift 600 includes a vehicle body (chassis) 602, a fork 604, an elevating body (lift) 606, a mast 608, a front wheel 610 as a driving wheel, and a rear wheel 612 as a steering wheel (steering wheel). The mast 608 is provided in front of the vehicle body 602. The lifting body 606 is driven by a power source such as a hydraulic actuator (not shown in FIG. 1, 116 in FIG. 3) and moves up and down along the mast 608. A fork 604 for supporting a load is attached to the elevating body 606.

  FIG. 2 is a view showing an example of a control panel 700 of a forklift. The control panel 700 includes an ignition switch 702, a steering wheel 704, a lift lever 706, an accelerator pedal 708, a brake pedal 710, a dashboard 714, and a forward / reverse lever 712.

  The ignition switch 702 is a switch for starting the forklift 600. The steering wheel 704 is an operation means for steering the forklift 600. The lift lever 706 is an operation means for moving the elevating body 606 up and down. The accelerator pedal 708 is an operating means that controls the rotation of the traveling wheels, and the travel of the forklift 600 is controlled by the driver adjusting the amount of depression. When the driver depresses the brake pedal 710, the brake is applied. The forward / reverse lever 712 is a lever for switching the traveling direction of the forklift 600 between forward and reverse. In addition, an inching pedal (not shown) may be provided.

  Next, the configuration of the forklift 600 will be described for traveling, cargo handling, and steering. FIG. 3 is a block diagram showing a configuration of an electric system and a mechanical system of the dual motor type forklift 600. The ECU (electronic control controller) 110 is a processor for controlling the forklift 600 as a whole.

Battery 106 outputs battery voltage V _BAT between P line and N line.
The first power conversion device 100, the second power conversion device 102, and the third power conversion device 104 constitute a motor drive device 300. Motor drive device 300 drives travel motors M1L, M1R, cargo handling motor M2, and steering motor M3 based on first control command value S1 to third control command value S3 from ECU 110, respectively. The first power conversion device 100, a second power converter 102, respectively the third power converter 104 receives the battery voltage _{V BAT,} is converted into three-phase alternating current signal, the corresponding motor M1L, the M1R, M2, M3 Supply.

(Running)
The ECU 110 receives a signal for instructing forward and backward from the forward / reverse lever 712 and a signal indicating a travel operation amount corresponding to the depression amount from the accelerator pedal 708, and receives a first control command value S1 corresponding to the first control command value S1 as a first value. It outputs to the power converter 100. The first power conversion device 100 controls the power supplied to each of the left traveling motor M1L and the right traveling motor M1R according to the first control command value S1. The first control command value S1 has a correlation with the speed command value that instructs the target speed of the traveling motor M1. The left front wheel (left drive wheel) 610L, which is a drive wheel, is rotated by the power of the left travel motor M1L, and the right front wheel (right drive wheel) 610R is rotated by the power of the right travel motor M1R.

(Handling)
The vertical movement of the elevating body 606 is controlled by the inclination of the lift lever 706. The ECU 110 detects the tilt of the lift lever 706 and outputs a second control command value S <b> 2 indicating a cargo handling operation amount corresponding to the tilt to the second power conversion device 102. The second power converter 102 supplies power corresponding to the second control command value S2 to the cargo handling motor M2, and controls its rotation. The elevating body 606 is connected to the hydraulic actuator 116. The hydraulic actuator 116 converts the rotary motion generated by the cargo handling motor M2 into a linear motion and controls the lifting body 606.

(steering)
The encoder 122 detects the rotation angle of the steering wheel 704 and outputs a signal indicating the rotation angle to the ECU 110. ECU 110 outputs third control command value S3 corresponding to the rotation angle to third power conversion device 104. The third power converter 104 supplies power corresponding to the third control command value S3 to the steering motor M3, and controls the number of rotations thereof. A rear wheel 612 that is a steered wheel is connected to a gear box 124 via a tie rod 126. The rotational motion of the steering motor M3 is transmitted to the tie rod 126 via the hydraulic actuator 118 and the gear box 124, and the steering is controlled.

  4 (a) and 4 (b) are diagrams schematically showing a dual motor type forklift 600. FIG. L is the wheel base, Trf is the front tread, Trr is the rear tread, nl (rpm) is the rotation speed of the left drive wheel 610L, nr (rpm) is the rotation speed of the right drive wheel 610R, and Vl (m / s) is The speed detection value (wheel speed) of the left driving wheel 610L and Vr (m / s) indicate the speed detection value (wheel speed) of the right driving wheel 610R.

The turning angles of the rear wheels 612L and 612R which are steered wheels can be controlled by the Ackerman steering mechanism. The intersection of the axles of the rear wheels 612L and 612R becomes the rotation center O of the vehicle body, and the rotation center O moves left and right on the axes of the front wheels 610L and 610R in accordance with the turning angle δr. In the present embodiment, the turning angle δr is defined as the rotation angle of the right rear wheel, but those skilled in the art understand that the definition of the turning angle δr is not limited thereto. The steered angle δr is positive when turning left as shown in FIG. 4A and negative when turning left as shown in FIG. 4B.
ρx is the distance between the rotation center O and the midpoint of the front wheels 610L and 610R.

  The steering mechanism of the forklift 600 allows the rotation center O to move between the front wheels 610L and 610R. In this case, the left and right drive wheels 610L and 610R are controlled to rotate in the reverse direction.

FIG. 5 is a block diagram showing a configuration of the motor drive device 300 (first power conversion device 100) according to the embodiment.
The motor driving device 300 includes a speed distribution unit 200, a torque command value generation unit 202, a torque limit unit 208, an inverter 210, a speed sensor 220, a rotation speed / speed (n / V) converter 221L, 221R, and a turning angle sensor 222. , Acceleration acquisition means 230, and torque correction unit 240.

  The turning angle sensor 222 detects the turning angle δr shown in FIG. The speed sensor 220 is also called a resolver, and detects the rotational speeds nl and nr of the left traveling motor M1L and the right traveling motor M1R. The n / V converters 221L and 221R multiply the rotational speeds nl and nr by a coefficient corresponding to the tire circumference, the reduction gear ratio, and the like, so that the wheel speed Vl of the left drive wheel 610L and the right drive wheel 610R The wheel speed Vr is calculated.

  The speed distribution unit 200 receives a speed command value Vref corresponding to the accelerator operation amount. The speed distribution unit 200 calculates a left speed command value Vlref that is a target speed of the left traveling motor M1L and a right speed command value Vrref that is a target speed of the right traveling motor M1R according to the current turning angle δr as follows. Calculate based on the formula.

1. δr = 0 (straight)
Vlref = Vrref = Vref

2. δr> 0 (turn left)
Vrref = Vref
Vlref = (ρx−Trf / 2) / (ρx + Trf / 2) × Vref
However, ρx = L / tan (δr) −Trr / 2.

3. δr <0 (turn right)
Vrref = (ρx−Trf / 2) / (ρx + Trf / 2) × Vref
Vrref = Vref
However, when δr ≠ −π / 2, ρx = −L / tan (δr) + Trr / 2, and when δr = −π / 2, ρx = Trr / 2.

  The speed distribution unit 200 may use a known technique, and its configuration and calculation algorithm are not limited to those described above.

  The torque command value generation unit 202 generates a left torque command value Tlcom that indicates the torque of the left traveling motor M1L according to the error between the left speed command value Vlref and the current detected speed value Vl of the left traveling motor M1L. Similarly, a right torque command value Trcom instructing the torque of the right travel motor M1R is generated according to the error between the right speed command value Vrref and the current speed detection value Vr of the right travel motor M1R.

  Torque command value generation unit 202 performs subtractor 204L that generates an error between left velocity command value Vlref and left velocity detection value Vl, and PI control that generates a left torque command value Tlcom by performing PI (proportional, integral) control on the error. Part 206L. The same applies to the right wheel.

  In the torque limit unit 208, a torque limit curve Tlim (n) that defines an upper limit value Tlim of the torque command values Tcoml and Tcomr is defined as a function of the motor speed n.

  The torque limit unit 208 limits the left torque command value Tlcom to an upper limit value Tllim which is determined according to the current speed nr of the left traveling motor M1L and the torque limit curve Tlim (n). Similarly, the torque limit unit 208 limits the right torque command value Trcom to an upper limit value Trlim determined according to the current speed nr of the right traveling motor M1R and the torque limit curve Tlim (n). The torque limit curve Tlim (n) may be held as a table or may be held as an approximate expression.

  The acceleration acquisition means 230 is a left acceleration αly that is an acceleration in the vehicle body lateral direction (y direction) at the coordinates of the ground contact point of the left driving wheel 610L and a vehicle body lateral acceleration at the coordinates of the ground contact point of the right drive wheel 610R. Acceleration αry is acquired.

  The torque correction unit 240 is provided in front of the torque limit unit 208 and corrects at least one of the left torque command value Tlcom and the right torque command value Trcom in accordance with the difference Δαy between the left acceleration αly and the right acceleration αry, and after the correction. Torque command values Tlcom and Trcom are output to the torque limit unit 208.

  More specifically, the torque correction unit 240 adds or subtracts a correction value ΔT obtained by multiplying the difference Δαy by a predetermined coefficient K to at least one of the left torque command value Tlcom and the right torque command value Trcom. The subtractor 242 of the torque correction unit 240 calculates a difference Δαy between the left acceleration αly and the right acceleration αry. The multiplier 244 multiplies the difference Δαy by a coefficient K to generate a correction value ΔT.

Then, the torque correction unit 240 subtracts the correction value ΔT corresponding to the difference Δαy from the torque command value of the driving wheel serving as the outer wheel. That is, when the steering wheel is turned to the left and the vehicle body is turning left (δr> 0), the correction value ΔTr for the right front wheel 610R as the outer wheel becomes K × ΔT, and the correction for the left front wheel 610L as the inner wheel. The value ΔTl becomes zero.
Conversely, when the steering wheel is turned to the right and the vehicle body is turning right (δr <0), the correction value ΔTl for the left front wheel 610L as the outer wheel becomes K × ΔT, and the right front wheel 610R as the inner wheel. The correction value ΔTr for is zero.

  The subtracters 246L and 246R subtract the correction amounts ΔTl and ΔTr from the torque command values Tlcom and Trcom, respectively. The torque command values Tlcom and Trcom corrected by the torque correction unit 240 are input to the torque limit unit 208 at the subsequent stage.

  Preferably, the torque correction unit 240 corrects the left torque command value Tlcom and the right torque command value Trcom when the difference Δαy is larger than the predetermined threshold value Δth, and corrects the correction value when the difference Δαy is smaller than the threshold value Δth. ΔTl and ΔTr are set to zero and no correction is performed.

  6A is a block diagram illustrating a configuration example of the acceleration acquisition unit 230, and FIG. 6B is a diagram illustrating the arrangement of sensors.

As shown in FIG. 6A, the acceleration acquisition unit 230 includes a left speed sensor 232L, a right speed sensor 232R, and a calculator 234.
As shown in FIG. 6B, the left speed sensor 232L is provided on the vertical line of the grounding point 236L of the left driving wheel 610L, in other words, at substantially the same coordinates as the grounding point of the left driving wheel 610L in the xy plane. And the vehicle lateral direction (y direction) speed Vly is detected. Similarly, the right speed sensor 232R is provided on the vertical line of the ground contact point 236R of the right drive wheel 610R, in other words, at substantially the same coordinates as the ground contact point of the right drive wheel 610R on the xy plane, and the vehicle lateral speed Vry. Is detected.

  The calculator 234 differentiates the outputs Vly and Vry of the left speed sensor 232L and the right speed sensor 232R, respectively. For example, the arithmetic unit 234 can be configured by a differentiator, and a first-order high-pass filter having a transfer function H (s) = s · τ / (1 + s · τ) can be preferably used. τ is a time constant of the filter.

  According to the acceleration acquisition means 230, the ground acceleration on the vertical line of the grounding points 236L and 236R of the left driving wheel 610L and the right driving wheel 610R can be acquired.

  The above is the configuration of the motor driving device 300. Next, the operation will be described.

(1) δr> 0 (when turning left)
In this case, the speed of the right driving wheel 610R as the outer wheel is larger than that of the left driving wheel 610L as the inner wheel, and nl <nr (Vl <Vr) is established. At this time, when the lateral acceleration | αry | on the grounding point vertical line of the outer driving wheel 610R is larger than the lateral acceleration | αly | on the grounding point vertical line of the inner driving wheel 610L, the difference Δαy = (| αry | − | Αly |), a correction value ΔTr is calculated, and the correction value ΔTr is subtracted from the right torque command value Trcom.

(2) δr <0 (when turning right)
In this case, the speed of the left driving wheel 610L that is the outer wheel is larger than that of the right driving wheel 610R that is the inner wheel, and nl> nr (Vl> Vr) holds. At this time, when the lateral acceleration | αly | on the contact point vertical line of the outer drive wheel 610L is larger than the lateral acceleration | αry | on the contact point vertical line of the inner drive wheel 610R, the difference Δαy = (| αly | − | Αry |), a correction value ΔTl is calculated, and the correction value ΔTl is subtracted from the left torque command value Tlcom.

The above is the operation of the motor driving device 300.
According to this motor drive device 300, the deviation of the lateral acceleration in the left and right drive wheels is calculated and used to correct the left and right torque balance. Such control does not necessarily give the same result as yaw moment control based on yaw rate, but it can be understood as yaw moment control in a broad sense, preventing side slip and load collapse, or reducing discomfort to the driver. it can.

  In addition, the left speed sensor 232L and the right speed sensor 232R are arranged on the vertical line of the grounding point of the left and right drive wheels, and the lateral speed at those positions is acquired, so that it is more accurate than using the yaw sensor. Lateral acceleration (lateral G) can be acquired.

  Further, according to the motor driving device 300, an expensive yaw sensor (gyro sensor) is not required, and thus the cost of the motor driving device 300 can be reduced.

  Further, forklifts generally operate while the left and right torque command values are always subjected to torque limits during traveling. Therefore, by subtracting the correction value ΔT from the torque command value of the driving wheel that is on the outside during turning, the torque correction can be reliably reflected as compared with the case where the torque correction value is added to the inner driving wheel. In a forklift in which the motor operates in a region where no torque limit is applied, a torque correction value may be added to the inner drive wheel. Alternatively, the torque correction value may be subtracted from the torque command value of the outer drive wheel, and the torque correction value may be added to the torque command value of the inner drive wheel.

  Side slipping, cargo collapse, or driver discomfort tends to occur when the difference Δαy exceeds a certain threshold. Therefore, the threshold value is obtained in advance by experiment or simulation, and when the difference Δαy of the lateral acceleration αy is larger than the predetermined threshold value, by correcting the torque, only when necessary. Torque control is executed, and unnecessary or excessive torque correction control can be prevented.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. is there. Hereinafter, such modifications will be described.

(First modification)
In the embodiment, the case where the speed sensor is arranged on the vertical lines of the grounding points 236L and 236R of the left driving wheel 610L and the right driving wheel 610R has been described, but the present invention is not limited to this. FIG. 7A is a block diagram showing the configuration of the acceleration acquisition means 230a according to the first modification, and FIG. 7B is a diagram showing the arrangement of the sensors.

  The speed sensor 232 is provided at a predetermined position of the vehicle and detects the speeds vy and vx in the vehicle lateral direction (y direction) and the vehicle body longitudinal direction (x direction). For example, the speed sensor 232 may be provided directly below the driver's seat.

  The computing unit 234 determines the coordinates of the contact point 236L of the left driving wheel 610L based on the vehicle lateral speed vy, the vehicle body longitudinal speed vx, and the turning angle δr detected by the speed sensor 232. The lateral acceleration αly in the vehicle lateral direction and the ground acceleration αry in the lateral direction of the vehicle at the coordinates of the contact point 236R of the right drive wheel 610R are calculated.

  According to those skilled in the art, when the coordinates of the speed sensor 232, the contact point 236L of the left drive wheel 610L, and the contact point 236R of the right drive wheel 610R are known, the coordinates of the rotation center O are calculated based on the turning angle δr. Further, it is understood that the speed (or acceleration) at an arbitrary coordinate can be calculated based on the outputs vy and vx of the speed sensor 232.

  Also by this modification, the same effect as the embodiment can be obtained. In this modification, an acceleration sensor may be provided instead of the speed sensor 232.

(Second modification)
In the embodiment, the case where the speed sensor is arranged on the vertical lines of the grounding points 236L and 236R of the left driving wheel 610L and the right driving wheel 610R has been described, but the present invention is not limited thereto. Instead of the speed sensor, an acceleration sensor may be provided, and the calculator (differentiator) 234 may be omitted.

  Although the present invention has been described using specific terms based on the embodiments, the embodiments only illustrate the principles and applications of the present invention, and the embodiments are defined in the claims. Many variations and modifications of the arrangement are permitted without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 600 ... Forklift, 602 ... Car body, 604 ... Fork, 606 ... Lifting body, 608 ... Mast, 610 ... Front wheel, 612 ... Rear wheel, 106 ... Battery, 100 ... First power converter, 102 ... Second power converter, DESCRIPTION OF SYMBOLS 104 ... 3rd power converter, 110 ... ECU, 116, 118 ... Hydraulic actuator, 120 ... Steering shaft, 122 ... Resolver, 124 ... Gear box, 126 ... Tie rod, 200 ... Speed distribution part, 202 ... Torque command value generation part , 204 ... subtractor, 206 ... PI control unit, 208 ... torque limit unit, 210 ... inverter, 220 ... speed sensor, 222 ... turning angle sensor, 230 ... acceleration acquisition means, 232L ... left speed sensor, 232R ... right speed Sensor, 234... Arithmetic unit, 236 .. ground point, 240... Torque correction unit, 242. DESCRIPTION OF SYMBOLS 4 ... Multiplier, M1 ... Travel motor, M1L ... Left travel motor, M1R ... Right travel motor, M2 ... Cargo handling motor, M3 ... Steering motor, 300 ... Motor drive device, 700 ... Steering panel, 610L ... Left drive wheel, 610R ... right drive wheel, 702 ... ignition switch, 704 ... steering wheel, 706 ... lift lever, 708 ... accelerator pedal, 710 ... brake pedal, 712 ... forward / reverse lever, 714 ... dashboard.

Claims (7)

A left traveling motor and a right motor mounted on an electric forklift of a front wheel drive and rear wheel steering type and transmitting power to each of the left drive wheel and the right drive wheel of the electric forklift based on a speed command value indicating a target speed of the electric forklift A motor driving device for controlling a traveling motor,
A left speed command value for instructing the speed of the left travel motor and a right speed command for instructing the speed of the right travel motor based on a speed command value according to a driver's operation and a turning angle of the steered wheels of the electric forklift A speed distribution unit that calculates a value;
According to an error between the left speed command value and the current speed of the left travel motor, a left torque command value indicating the torque of the left travel motor is generated, and the right speed command value and the current current of the right travel motor are generated. A torque command value generation unit that generates a right torque command value that indicates the torque of the right traveling motor according to the speed error of
Acceleration acquisition means for acquiring left acceleration that is ground acceleration in the lateral direction of the vehicle body at the coordinates of the ground contact point of the left drive wheel and right acceleration that is ground acceleration in the lateral direction of the vehicle body at the coordinate of the ground contact point of the right drive wheel. When,
A torque correction unit that corrects at least one of the left torque command value and the right torque command value according to a difference between the left acceleration and the right acceleration;
A motor drive device comprising:   The torque correction unit, wherein a correction value obtained by multiplying the difference by a predetermined coefficient is added to or subtracted from at least one of the left torque command value and the right torque command value. The motor drive device according to 1.   3. The motor drive device according to claim 1, wherein the torque correction unit subtracts a correction value corresponding to the difference from a torque command value of a drive wheel serving as an outer wheel. 4.   The said torque correction part correct | amends at least one of the said left torque command value and the said right torque command value, when the said difference is larger than a predetermined | prescribed threshold value. Motor drive device. The acceleration acquisition means includes
A left speed sensor provided on a substantially vertical line of the grounding point of the left drive wheel and detecting a ground speed in a lateral direction of the vehicle;
A right speed sensor provided on a substantially vertical line of the grounding point of the right drive wheel for detecting a ground speed in a lateral direction of the vehicle;
An arithmetic unit for differentiating outputs of the left speed sensor and the right speed sensor;
5. The motor driving apparatus according to claim 1, comprising: The acceleration acquisition means includes
A speed sensor that is provided at a predetermined position of the vehicle and detects ground speeds in the vehicle lateral direction and the vehicle body longitudinal direction at the position;
Based on the ground speed in the vehicle lateral direction and the ground speed in the longitudinal direction of the vehicle body at the predetermined position, the ground acceleration in the vehicle lateral direction and the coordinates of the ground point of the right drive wheel in the coordinates of the ground point of the left drive wheel A computing unit for calculating the ground acceleration in the vehicle lateral direction at
5. The motor driving apparatus according to claim 1, comprising: Left drive wheel and right drive wheel,
A left travel motor and a right travel motor that transmit power to each of the left drive wheel and the right drive wheel;
The motor drive device according to any one of claims 1 to 6, which drives the left travel motor and the right travel motor;
An electric forklift characterized by comprising:

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