JP2014128117A - Motor drive device for electric forklift and electric forklift using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive device of a running motor of a forklift.SOLUTION: A first operation part 230, based on a speed directing value Vref and a steering angle δr of a steering wheel corresponding to operation of a driver, calculate a synthesized speed directing value Vxref directing a synthesized speed Vx of the left running motor M1L and the right running motor M1R, and a speed difference directing value Vyref for directing a speed difference Vy between those. A second operation part 232 calculates a synthesized speed detecting value Vxfb representing a present synthesized speed Vx of the left running motor M1L and the right running motor M1R and a speed difference detecting value Vyfb representing those present speed difference Vy. A torque directing value generating part 202 generates a torque directing value Txcom (Tycom) corresponding to the error of the synthesized speed directing value Vxref (Vyref) and the synthesized speed detecting value Vxfb (Vyfb) and generates torque directing values Tlcom, Trcom for directing each torque of the left running motor M1L and the right running motor M1R, respectively.

Description

  The present invention relates to a motor drive device for an electric 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.

  FIG. 1 is a block diagram showing a configuration of a motor driving device mounted on a dual motor type electric forklift examined by the present inventors. The dual motor type electric forklift is provided with an independent motor for each of the right drive wheel and the left drive wheel, and is configured such that the rotation speed and rotation direction of each can be controlled independently.

  1 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, a steered wheel. An angle sensor 222 is provided.

  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 according to the tire circumference, the reduction gear ratio, and the like, so that the wheel speed (left speed detection value) Vl of the left drive wheel 610L. The wheel speed (right speed detection value) Vr of the right drive wheel 610R is calculated. The turning angle sensor 222 detects the turning angle δr.

  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.

  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 an error between the left speed command value Vlref and the current left speed detection value Vl. 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 right speed detection value Vr.

  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 the upper limit value Tlim of the torque command values Tlcom and Trcom 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 nl 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).

  Inverters 210L and 210R drive travel motors M1L and MIR based on torque command values Tlref and Trref from torque limit unit 208.

JP 2005-184978 A

  In the motor drive device 300r of FIG. 1, PI control is performed for the left and right drive wheels. The control characteristics of the motor drive device 300r depend on the type of control (P control, PI control, PID control, etc.), the proportional term coefficient of the PID control, the integral term coefficient, the differential term coefficient, etc. The type and each coefficient must be complete. This is because if the left and right coefficients do not match, the vehicle behavior becomes asymmetrical.

  In other words, if the left and right wheel speeds are controlled, the same control characteristics must be set for the left and right drive wheels, so the degree of freedom in designing the control characteristics is low.

  The present invention has been made in such a situation, and one of exemplary purposes of an embodiment thereof is to provide a driving device for a travel motor of a forklift that can realize a high degree of freedom by an approach different from the conventional one. .

  An aspect of the present invention includes a left traveling motor and a right traveling motor that are mounted on an electric forklift and transmit power to each of a left driving wheel and a right driving wheel of the electric forklift based on a speed command value indicating a target speed of the electric forklift. The present invention relates to a motor drive device to be controlled. The motor drive device instructs (i) a combined speed defined as a speed at a predetermined position of the vehicle body of the electric forklift based on a speed command value according to a driver's operation and a turning angle of a steered wheel of the electric forklift. A first calculation unit that calculates a combined speed command value and (ii) a speed difference command value that indicates a speed difference defined according to a difference between the speed of the left traveling motor and the right traveling motor; A left speed detection value indicating the current speed of the motor, a right speed detection value indicating the current speed of the right traveling motor, and a turning angle; and (i) a combined speed detection value indicating the current combined speed; , (Ii) a second calculation unit for calculating a speed difference detection value indicating the current speed difference, and (i) generating a first torque command value according to an error between the combined speed command value and the combined speed detection value (Ii) Depending on the error between the speed difference command value and the speed difference detection value, A torque command value is generated. (Iii) Based on the first torque command value and the second torque command value, a left torque command value for instructing the torque of the left traveling motor and a right torque command value for instructing the torque of the right traveling motor are obtained. A torque command value generation unit for generating.

  According to this aspect, since the feedback control is performed using the speed at a predetermined position of the vehicle body and the speed difference between the left and right traveling motors as a monitoring amount, the feedback control characteristics of the combined speed and the speed difference can be independently designed. Higher degree of freedom.

  The synthesized speed detection value may be defined as one of the left speed detection value and the right speed detection value corresponding to the outer ring or the inner ring.

  The predetermined portion may be one of an outer wheel or an inner wheel. The synthesized speed detection value may be one of the left speed detection value and the right speed detection value corresponding to the outer driving wheel or the inner driving wheel.

The combined speed detection value may be calculated by a weighted average of the left speed detection value and the right speed detection value when the turning angle is included in a predetermined range near zero.
Thereby, it can prevent that control becomes discontinuous.

  The speed difference detection value may be a difference between the left speed detection value and the right speed detection value.

  The speed difference command value is a value corresponding to the difference between the speed assumed for the left travel motor and the speed assumed for the right travel motor when the predetermined part of the vehicle travels at a speed corresponding to the combined speed command value. May be defined as

  The torque command value generation unit sets one of the left torque command value and the right torque command value as an addition value of the first torque command value and the second torque command value, and sets the other of the left torque command value and the right torque command value as the first torque command value. It is good also as a difference of 1 torque command value and 2nd torque command value.

  In a drive device according to a certain aspect, a first speed limit curve that defines an upper limit of a combined speed command value is defined as a function of a turning angle, and the combined speed command value is converted into a first speed limit curve and a turning angle. You may further provide the 1st turning speed limit part restrict | limited below the upper limit determined according to it.

  In one aspect of the drive device, the second speed limit curve that defines the upper limit of the speed difference command value is defined as a function of one of the synthesized speed detection value and the synthesized speed command value and the turning angle, and the speed difference command value May be further provided with a second turning speed limit unit that restricts the second speed limit curve, one of the combined speed detection value and the combined speed command value, and an upper limit value determined according to the turning angle.

  Another aspect of the present invention relates to a forklift. The 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 any one of the motors described above that drives the left traveling motor and the right traveling motor. A driving device.

  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.

  According to the present invention, a forklift can be controlled.

It is a block diagram which shows the structure of the motor drive device mounted in the dual motor type electric forklift which the present inventors examined. It is a perspective view which shows the external view of a forklift. 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. 5A and 5B 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. It is a figure which shows a weighting coefficient. It is a block diagram which shows the structure of a part of motor drive device which concerns on a modification.

  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. 2 is a perspective view showing an external view of the forklift. The forklift 600 includes a vehicle body (chassis) 602, a fork 604, a lifting body (lift) 606, a mast 608, and wheels 610 and 612. 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. 2, 116 in FIG. 4) and moves up and down along the mast 608. A fork 604 for supporting a load is attached to the elevating body 606.

  FIG. 3 is a view showing an example of the control panel 700 of the 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 user adjusting the amount of depression. When the user 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. 4 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.

  FIGS. 5A and 5B are diagrams schematically showing a dual motor type forklift 600. L is the wheel base, Trf is the front tread, Trr is the rear tread, nl (rpm) is the speed of the left driving wheel 610L, nr (rpm) is the speed of the right driving wheel 610R, and Vl (m / s) is the left driving. The speed of the wheel 610L and Vr (m / s) indicate the speed of the right drive 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. 5A and negative when turning left as shown in FIG. 5B.
ρx is the distance between the rotation center O and the midpoint (referred to as the vehicle body representative point X) 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. 6 is a block diagram illustrating a configuration of a motor drive device 300 (first power conversion device 100) according to the embodiment. The motor drive device 300 includes a first calculation unit 230, a torque command value generation unit 202, a torque limit unit 208, an inverter 210, a speed sensor 220, an n / V converter 221, a turning angle sensor 222, and a second calculation unit 232. Prepare.

  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 (left speed detection value) Vlfb of the left drive wheel 610L. The wheel speed (left speed detection value) Vrfb of the right drive wheel 610R is calculated. The turning angle sensor 222 detects the turning angle δr.

  This motor drive device 300 uses the combined speed Vx of the vehicle and the speed difference Vy between the left and right drive wheels as feedback control targets. Specifically, the motor driving device 300 adjusts the detected value of the speed difference Vy so that the detected value of the combined speed Vx (the combined speed detected value Vxfb) matches the target value (the combined speed command value Vxcom). The rotational speeds of the left and right traveling motors M1L and M1R are adjusted by feedback so that the speed difference detection value Vyfb) matches the target value (speed difference command value Vycom).

  The combined speed Vx is defined as the speed of a predetermined part of the vehicle body, and the speed difference Vy is defined as a value corresponding to the difference between the speeds of the outer ring and the inner ring. More specifically, in the present embodiment, the predetermined portion is the outer drive wheel, and the combined speed Vx is defined as the speed of the outer drive wheel.

  Based on the speed command value Vref according to the driver's operation and the turning angle δr of the steered wheels of the forklift 600, the first calculation unit 230 (i) the speed Vl of the left traveling motor M1L and the speed Vr of the right traveling motor M1R. And (ii) a speed difference command value Vyref indicating the speed difference Vy between the speed Vl of the left traveling motor M1L and the speed Vr of the right traveling motor M1R is calculated. .

In the present embodiment, the combined speed command value Vxref is the speed command value Vref.
Vxref = Vref

The speed difference command value Vyref is the speed Vl assumed for the left travel motor M1L and the right travel motor when a predetermined portion of the vehicle (in this case, the outer drive wheel) travels at a speed corresponding to the combined speed command value Vxref. It is defined as a value corresponding to the speed difference Vr assumed in M1R.
Vyref = Vr−Vl

  A person skilled in the art understands that Vyref = Vl−Vr may be defined. In this case, the sign of other variables may be appropriately reversed for other variables.

  With reference to FIGS. 5A and 5B, the speed difference command value Vyref will be described.

1. δr = 0 (straight)
When traveling straight, ideally, the speeds of the left traveling motor M1L and the right traveling motor M1R are equal. Therefore, the speed difference command value Vyref when traveling straight is zero.
Vyref = 0

2. δr ≠ 0 (when turning)
At the time of turning, there is a speed difference between the outer ring speed Vo and the inner ring speed Vi. Each of the right turn and the left turn will be specifically described.

2.1. δr> 0 (turn left)
At this time, the right traveling motor corresponds to the outer ring, and the left traveling motor corresponds to the inner ring.
Vo = Vr
Vi = Vl = η × Vo
However, the coefficient η is given by (ρx−Trf / 2) / (ρx + Trf / 2). ρx = L / tan (δr) −Trr / 2.

Therefore, the speed difference command value Vyref when turning left is
Vyref = Vr−Vl = (1−η) × Vo
= Trf / (ρx + Trf / 2) × Vo
It becomes. In the present embodiment, the outer wheel speed Vo is a combined speed command value Vxref = Vref. Accordingly, the speed difference command value Vyref at the time of turning left is calculated by the following equation.
Vyref = Trf / (ρx + Trf / 2) × Vref

2.2. δr <0 (turn right)
At this time, the right travel motor corresponds to the inner ring and the left travel motor corresponds to the outer ring.
Vo = Vl
Vi = Vr = η × Vl

  However, when δr ≠ −π / 2, ρx = −L / tan (δr) + Trr / 2, and when δr = −π / 2, ρx = Trr / 2.

Therefore, the speed difference command value Vyref when turning right is
Vyref = Vr−Vl = (η−1) × Vo
= −Trf / (ρx + Trf / 2) × Vo
It becomes. In the present embodiment, the outer wheel speed Vo is a combined speed command value Vxref = Vref. Therefore, the speed difference command value Vyref at the time of turning right is calculated by the following formula.
Vyref = Trf / (ρx + Trf / 2) × Vref

  Returning to FIG. The second calculation unit 232 calculates a left speed detection value Vlfb indicating the current speed Vl of the left travel motor M1L, a right speed detection value Vrfb indicating the current speed Vr of the right travel motor M1R, and the turning angle δr. receive. The second calculation unit 232 includes (i) a combined speed detection value Vxfb indicating a combined speed Vx of the current speed Vl of the left traveling motor M1L and the speed Vr of the right traveling motor M1R, and (ii) the current left traveling motor M1L. A speed difference detection value Vyfb indicating a speed difference Vy between the speed Vl and the speed Vr of the right traveling motor M1R is calculated.

Specifically, the speed difference detection value Vyfb corresponds to the difference Vlfb−Vrfb between the right speed detection value Vrfb and the left speed detection value Vlfb.
Vyfb = Vrfb−Vlfb

  The combined speed detection value Vxfb is one of the left speed detection value Vlfb and the right speed detection value Vrfb that corresponds to the outer ring.

  Most simply, Vxfb = Vrfb when δr ≧ 0, and Vxfb = Vlfb when δr <0. Alternatively, Vxfb = Vrfb when δr> 0, and Vxfb = Vlfb when δr ≦ 0. However, in these controls, there is a problem that the control becomes discontinuous when traveling straight (δr = 0) and when turning (δr ≠ 0).

In order to solve this problem, when δr is within a predetermined range near zero (−α <δr <α), the left speed detection value Vlfb and the right speed detection value Vrfb are weighted and averaged by coefficients Kl and Kr. Thus, it is desirable to calculate the composite speed detection value Vxfb.
Vxfb = Vlfb × Kl + Vrfb × Kr

  FIG. 7 is a diagram illustrating weighting coefficients.

The coefficients Kl and Kr are defined as a function of the turning angle δr.
Kl = 1 (δr <−α)
K1 = 0 (δr> α)
In the range of −α <δr <α, Kl is determined to increase monotonously according to δr. For example, Kl varies linearly with δr.
K1 = − (δr / 2α) +0.5 (−α <δr <α)

Kr = 1 (δr> α)
Kr = 0 (δr <α)
Kr = (δr / 2α) +0.5 (−α <δr <α)

Therefore, in the range of −α <δr <α, the following equation is given.
Vxfb = {− (δr / 2α) +0.5} × Vlfb + {(δr / 2α) +0.5} × Vrfb

  By performing the weighted average processing, discontinuity of control can be prevented and the system can be stabilized.

  Returning to FIG. The torque command value generation unit 202 (i) generates a first torque command value Txcom according to an error between the combined speed command value Vxref and the combined speed detection value Vxfb, and (ii) detects the speed difference command value Vyref and the speed difference. A second torque command value Tycom is generated according to the error of the value Vyfb. Then, the torque command value generation unit 202 (iii) generates the torque of the left torque command value Tlcom and the torque of the right travel motor M1R for instructing the torque of the left travel motor M1L based on the first torque command value Txcom and the second torque command value Tycom. A right torque command value Trcom to be instructed is generated.

  The torque command value generation unit 202 generates a torque command value by PI control, for example. The torque command value generator 202 includes adders / subtractors 204x and 204y, PI controllers 206x and 206y, adders / subtractors 205L and 205R, and coefficient circuits 207L and 207R.

  The adder / subtractor 204x calculates a difference ΔVx between the combined speed command value Vxref and the combined speed detection value Vxfb. The PI control unit 206x performs PI (proportional, integral) control on the error ΔVx to generate a first torque command value Txcom. The adder / subtractor 204y calculates a difference ΔVy between the speed difference command value Vyref and the speed difference detection value Vyfb. The PI control unit 206y performs PI (proportional, integral) control on the error ΔVy to generate a second torque command value Tycom.

  The control method of the PI control units 206x and 206y is not limited to PI control, and other control (PID control or the like) may be used.

The torque command value generation unit 202 sets one of the left torque command value Tlcom and the right torque command value Trcom as an addition value of the first torque command value Txcom and the second torque command value Tycom, and sets the other one as the first torque command value. The difference between the value Txcom and the second torque command value Tycom is used. In the present embodiment, the adders / subtractors 205L and 206R generate the left and right torque command values Tlcom and Trcom by the following calculation.
Tlcom = Txcom + Tycom
Trcom = Txcom-Tycom

  The coefficient circuits 207L and 207R respectively multiply the torque command values Tlcom and Trcom by a predetermined coefficient. The positions of the coefficient circuits 207L and 207R are not limited to those in FIG. 6, and may be provided at different positions.

  In the torque limit unit 208, a torque limit curve Tlim (n) that defines the upper limit value Tlim of the torque command values Tlcom and Trcom 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 nl 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).

  Inverters 210L and 210R drive travel motors M1L and MIR based on torque command values Tlref and Trref from torque limit unit 208.

  The above is the configuration of the motor driving device 300.

  According to this motor drive device 300, instead of setting the rotational speeds of the left and right traveling motors as feedback control targets, their combined speed and speed difference are set as control targets. As a result, the vehicle can be controlled in accordance with the operation of the driver both when traveling straight and when turning.

  In particular, in the motor drive device 300r of FIG. 1, it is necessary to match the control type and the PI control coefficient for the left and right traveling motors. On the other hand, according to the motor driving device 300 of FIG. 6, the coefficients of the proportional terms of the PI control units 206x and 206y are optimized to different values and / or the integral terms of the PI control units 206x and 206y, respectively. The coefficients can be optimized to different values, and the degree of freedom in design can be increased. Furthermore, different control methods (P control, PI control, PID control, etc.) can be selected for the PI control unit 206x and the PI control unit 206y.

  In addition, according to the motor drive device 300 of FIG. 6, the turning speed (yaw rate) can be more appropriately controlled and limited by introducing the turning speed limit unit 234 described below. Hereinafter, this advantage will be described.

FIG. 8 is a block diagram illustrating a partial configuration of a motor driving device 300a according to a modification.
The motor drive device 300a includes a turning speed limit unit 234 in addition to the motor drive device 300 of FIG.

  The turning speed limit unit 234 includes a first turning speed limit unit 234x and a second turning speed limit unit 234y. In the first turning speed limit unit 234x, a first speed limit curve fxlim that defines an upper limit Vxlim of the combined speed command value Vxref is defined as a function of the turning angle δr. The first turning speed limit unit 234x limits the combined speed command value Vxref from the first calculation unit 230 to an upper limit value Vxlim that is determined according to the first speed limit curve fxlim and the turning angle.

  In the second turning speed limit unit 234y, a second speed limit curve fylim that defines an upper limit Vylim of the speed difference command value Vyref is a function of one of the combined speed detection value Vxfb and the combined speed command value Vxref and the turning angle δr. Is defined. The second turning speed limit unit 234y reduces the speed difference command value Vyref to an upper limit value Vylim which is determined according to the second speed limit curve fylim, one of the combined speed detection value Vxfb and the combined speed command value Vxref, and the turning angle δr. Restrict.

  The combined speed command value Vxref ′ speed difference command value Vyref ′ limited by the turning speed limit units 234 x and 234 y is input to the torque command value generation unit 202.

  The above is the configuration of the motor driving device 300a according to the modification.

  Since the forklift is used in a narrow work area, the turning radius is effective compared to a general vehicle, in other words, the turning radius can be made very small. Therefore, if no restriction is applied, the vehicle posture may become unstable if the accelerator is depressed when the turning radius is small.

  By introducing the turning speed limit unit 234, the speed at the time of turning can be appropriately limited according to the turning angle δr, so that discomfort experienced by the user can be reduced.

  The speed limit curves fxlim and fylim may be defined so that the angular velocity ω with respect to the center of rotation (O in FIG. 5A) is equal to or less than a certain threshold value.

  In the above, this invention was demonstrated based on the Example. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, various modifications are possible, and such modifications are within the scope of the present invention. By the way. Hereinafter, such modifications will be described.

(Modification 1)
In the embodiment, the composite speed Vx is defined as the speed of the outer ring, but the present invention is not limited to this. For example, the combined speed Vx may be defined as a speed at a predetermined portion of the body of the electric forklift, and is not limited to the speed of the outer ring.
For example, a predetermined portion may be defined as the inner ring, and the combined speed Vx may be defined as the speed of the inner ring. Alternatively, the predetermined location is an arbitrary point on the axis of the left driving wheel and the right driving wheel, for example, the midpoint of the left driving wheel and the right driving wheel, and the combined speed Vx is an average value of the speeds of the left and right driving wheels. Also good.

  The present invention is not limited to an electric forklift, and can be applied to various industrial vehicles having a similar mechanism.

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, adder / subtractor, 206, PI control unit, 208, torque limit unit, 210, inverter, 220, speed sensor, 221, n / V converter, 222, turning angle sensor, 230, first calculation unit, 232 ... 2nd calculating part, 234 ... Turning speed limit part, 234x ... 1st turning speed limit part, 234y ... 2nd turning Degree limit unit, M1 ... travel motor, M1L ... left travel motor, M1R ... right travel motor, M2 ... loading motor, M3 ... steering motor, 300 ... motor drive device, 700 ... control 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 (10)

A motor drive device that is mounted on an electric forklift and controls a left traveling motor and a right traveling motor that transmit power to each of the left driving wheel and the right driving wheel of the electric forklift based on a speed command value indicating a target speed of the electric forklift Because
Based on the speed command value according to the operation of the driver and the turning angle of the steered wheels of the electric forklift, (i) a composite speed command for instructing a composite speed defined as a speed at a predetermined position of the vehicle body of the electric forklift A first calculation unit that calculates a value and (ii) a speed difference command value that indicates a speed difference defined according to a difference between the speed of the left traveling motor and the speed of the right traveling motor;
The left speed detection value indicating the current speed of the left travel motor, the right speed detection value indicating the current speed of the right travel motor, and the turning angle, and (i) the current combined speed A second calculation unit that calculates a combined speed detection value to be displayed and (ii) a speed difference detection value indicating the current speed difference;
(I) generating a first torque command value according to an error between the synthesized speed command value and the synthesized speed detection value; and (ii) changing a first torque command value according to an error between the speed difference command value and the speed difference detected value. (Iii) Based on the first torque command value and the second torque command value, the left torque command value for instructing the torque of the left traveling motor and the torque of the right traveling motor are instructed. A torque command value generator for generating a right torque command value;
A motor drive device comprising: The predetermined portion is one of an outer wheel or an inner wheel.
2. The motor drive device according to claim 1, wherein the combined speed detection value is one of the left speed detection value and the right speed detection value corresponding to an outer drive wheel or an inner drive wheel. .   The combined speed detection value is calculated by a weighted average of the left speed detection value and the right speed detection value when the turning angle is included in a predetermined range near zero. 2. The motor drive device according to 2.   4. The motor driving apparatus according to claim 1, wherein the speed difference detection value is a difference between the left speed detection value and the right speed detection value. 5.   The speed difference command value is defined as a value corresponding to a difference in speed between the left travel motor and the right travel motor when the predetermined portion of the vehicle body travels at a speed corresponding to the combined speed command value. The motor driving device according to claim 1, wherein the motor driving device is a motor driving device.   The torque command value generation unit uses one of the left torque command value and the right torque command value as an addition value of the first torque command value and the second torque command value, and the left torque command value and the right torque 6. The motor drive device according to claim 1, wherein the other of the command values is a difference between the first torque command value and the second torque command value.   A first speed limit curve that defines an upper limit of the combined speed command value is defined as a function of the turning angle, and the combined speed command value is determined according to the first speed limit curve and the turning angle. The motor drive device according to claim 1, further comprising a first turning speed limit unit that limits the value to a predetermined upper limit value or less.   A second speed limit curve that defines an upper limit of the speed difference command value is defined as a function of one of the synthesized speed detection value and the synthesized speed command value and the turning angle, and the speed difference command value is The vehicle further comprises a second turning speed limit unit configured to limit the second speed limit curve, one of the combined speed detection value and the combined speed command value, and an upper limit value determined according to the turning angle. Item 8. The motor driving device according to any one of Items 1 to 7.   The motor drive apparatus according to claim 1, wherein the combined speed command value is the speed command value. 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 driving device according to any one of claims 1 to 9, which drives the left traveling motor and the right traveling motor;
A forklift characterized by comprising:

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