Traveling control device for work vehicle

Abstract

To provide a traveling control device for a work vehicle that can improve the followability for a traveling operation.SOLUTION: When a traveling state of a vehicle transitions from turning travel to straight travel, a traveling control device for a high elevation work vehicle maintains rotation speed of the other traveling motor constant by setting acceleration of the other traveling motor to zero and sets acceleration of one traveling motor to acceleration larger than basic acceleration, during a period until rotation speed of the one traveling motor at the inside of a turning direction reaches the rotation speed of the other traveling motor at the outside in the turning direction, out of a left-side traveling motor and a right-side traveling motor, as synchronization control of the left-side traveling motor and the right-side traveling motor.SELECTED DRAWING: Figure 15

Description

[Technical field]

[0001] The present invention relates to a travel control device for a work vehicle having crawler travel devices on both the left and right sides of the vehicle body. [Background technology]

[0002] As an example of a work vehicle, a crawler type work vehicle is known that includes a travelling body having a pair of left and right crawler travelling devices and a work platform for a worker mounted on the travelling body that can be raised and lowered, and that is configured to be able to perform straight travel and turning travel (slalom turning travel, pivot turning travel, spin turning travel) by controlling the rotation direction and rotation speed of the left and right crawler travelling devices according to the operation direction and operation amount of the travel operation lever and the turning amount operation dial (see, for example, Patent Document 1). Also known are crawler type work vehicles that include two travel operation levers, one on the left and one on the right, instead of the travel operation lever and the turning amount operation dial (see, for example, Patent Document 2), crawler type work vehicles that include a travel lever that switches between forward and reverse, an accelerator pedal that sets the travel speed, and a handle that sets the turning direction and turning amount (see, for example, Patent Document 3), and crawler type work vehicles that include a joystick-type travel operation device that allows forward travel, reverse travel, travel speed, turning direction, and turning amount to be set by a single travel operation lever (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6080458 [Patent Document 2] JP 2003-343510 A [Patent Document 3] Japanese Utility Model Application Publication No. 5-24481 [Patent Document 4] JP 2002-104227 A Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional crawler-type work vehicles, when transitioning from turning to straight-line driving, there is a delay in the timing at which the rotational speed of the crawler traveling device on the inside of the turning direction synchronizes with the rotational speed of the crawler traveling device on the outside of the turning direction, which can result in the vehicle turning for longer than intended by the worker before starting straight-line driving, resulting in poor response to driving operations.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a driving control device for a work vehicle that can improve response to driving operations. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a travel control device for a work vehicle comprising a vehicle body, a left side crawler travel device and a right side crawler travel device provided on the left and right sides of the vehicle body, a left side travel motor and a right side travel motor which drive the left side crawler travel device and the right side crawler travel device, respectively, a travel operation device for performing operations to drive the left side crawler travel device and the right side crawler travel device, and a travel control unit which controls the drive of the left side crawler travel device and the right side crawler travel device by controlling the rotation direction and rotation speed of the left side travel motor and the right side travel motor in response to operation of the travel operation device, the travel control unit has a travel state determination unit which determines the travel state of the work vehicle, and an acceleration determination unit which sets the acceleration of the left side travel motor and the right side travel motor when accelerating or decelerating the work vehicle to a predetermined basic acceleration, and the travel control unit determines the acceleration of the left side travel motor and the right side travel motor when the work vehicle is being accelerated or decelerated, and determines the acceleration of the left side travel motor and the right side travel motor in response to operation of the travel operation device. The synchronization control of the running motor and the right-side running motor is characterized in that, until the rotational speed of one of the left-side running motor and the right-side running motor, which is on the inside of the turning direction, reaches the rotational speed of the other running motor, which is on the outside of the turning direction, the acceleration of the other running motor is set to zero to keep the rotational speed of the other running motor constant, and the acceleration of the one running motor is set to an acceleration greater than the basic acceleration.

[0007] Furthermore, in the driving control device for a work vehicle having the above-described configuration, when the rotational speed of one of the driving motors reaches the rotational speed of the other of the driving motors during the synchronous control, it is preferable to set the acceleration of the one and the other of the driving motors to the basic acceleration until the rotational speeds of the one and the other of the driving motors reach a predetermined target rotational speed.

[0008] Furthermore, in the driving control device for a work vehicle configured as described above, the basic accelerations include a first basic acceleration that is set when the work vehicle starts to drive, a second basic acceleration that is set when the work vehicle stops to drive, and a third basic acceleration that is set when the work vehicle accelerates or decelerates while driving (excluding when the driving starts to drive and when the driving stops), and when the driving state of the work vehicle transitions from pivot turning driving or gentle turning driving to straight driving, it is preferable that the driving control unit sets the acceleration of one of the driving motors to an acceleration greater than the third basic acceleration until the rotational speed of the one of the driving motors reaches the rotational speed of the other of the driving motors.

[0009] Furthermore, in the driving control device for a work vehicle having the above-described configuration, when the driving state of the work vehicle is transitioned from spin turning driving to straight driving, it is preferable that the driving control unit sets the acceleration of the one of the driving motors to an acceleration greater than the second basic acceleration until the rotational speed of the one of the driving motors reaches zero, and sets the acceleration of the one of the driving motors to an acceleration greater than the first basic acceleration after the rotational speed of the one of the driving motors reaches zero until it reaches the rotational speed of the other of the driving motors. Effect of the Invention

[0010] According to the driving control device for a work vehicle of the present invention, when the vehicle's driving state transitions from turning driving to straight driving, the left and right driving motors are synchronized by maintaining the rotational speed of the outside driving motor constant without accelerating it until the rotational speed of the inside driving motor in the turning direction reaches the rotational speed of the outside driving motor in the turning direction, and by changing the acceleration of the inside driving motor in the turning direction to an acceleration greater than the basic acceleration (normal acceleration), the time until the rotational speeds of the left and right driving motors are synchronized is shortened and the vehicle can start driving straight at a timing that matches the operator's operating intention (this prevents a situation where turning driving is continued for a longer period than the operator expected), thereby improving the response to driving operations and achieving safe and excellent driving performance without any discomfort that matches the operator's operating intention.

[0011] Furthermore, according to the driving control device for a work vehicle of the present invention, the rotational speeds of the left side traveling motor and the right side traveling motor can be synchronized before they reach the target rotational speed, so that the rotational speeds of the left side traveling motor and the right side traveling motor can reach the target rotational speed at the same timing. This effectively prevents the vehicle from swinging back and forth, which reduces driving stability (the worker being swayed from side to side as a result of this reaction), and ensures work safety.

[0012] In addition, according to the driving control device for a work vehicle according to the present invention, when the rotation speeds of the left and right traveling motors are synchronized when the vehicle's driving state transitions from turning to straight driving, the acceleration of the left and right traveling motors is returned to the basic acceleration (normal acceleration), thereby preventing the acceleration (straight driving) after the rotation speeds of the left and right traveling motors are synchronized. This makes it possible to suppress the acceleration during driving (the acceleration when the left and right traveling motors reach the target rotation speed and transition to steady driving (constant speed driving) and to reduce the shock that occurs when the left and right traveling motors reach the target rotation speed and transition to steady driving (constant speed driving). [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a side view showing the aerial work vehicle of the present embodiment. [Diagram 2] FIG. 2 is a block diagram showing an operating mechanism of the aerial work vehicle. [Diagram 3] 4 is a block diagram showing a control system for the crawler traveling device of the aerial work vehicle. FIG. [Figure 4] 10 is a graph showing the relationship between the amount of operation of a turning amount operation dial and a target rotation speed of a traveling motor. [Diagram 5] 13 is a flowchart of a main loop process. [Figure 6] 4 is a flowchart of a driving output control process. [Figure 7] 4 is a graph showing the relationship between the operation amount of a travel operation lever and a reference target rotation speed of a travel motor. [Figure 8] 5 is a graph showing the relationship between the amount of operation of a turning amount operation dial and the deceleration rate of a traveling motor. [Figure 9] 4 is a table for explaining a driving mode determination process. [Figure 10] 11 is a time chart illustrating a left-right synchronization determination process. [Figure 11] 11 is a table for explaining an acceleration determination process. [Figure 12] 4 is a time chart for explaining the acceleration of a traveling motor. [Figure 13] 13 is a flowchart of a rotation speed command value determination process. [Figure 14] 4 is a graph showing a schematic example of a change over time in a rotation speed command value; [Figure 15] 1A and 1B are diagrams for comparing driving control of the conventional technology with driving control of this embodiment when transitioning from spin turning driving to straight driving, in which (A) is a time chart showing driving control of the conventional technology, and (B) is a time chart showing driving control of this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Fig. 1 shows a crawler type vehicle for working at height as an example of a work vehicle according to the present invention. First, the overall configuration of the vehicle for working at height 1 will be described with reference to Fig. 1.

[0015] The high-altitude work vehicle 1 is composed of a travelling body 10, a vertically extending mast 20 provided on the upper front side of the travelling body 10, and a work platform 30 for a worker to ride on provided on the top of the mast 20.

[0016] The traveling body 10 has a traveling body frame 11, and a left crawler traveling device 12L and a right crawler traveling device 12R provided on both the left and right sides of the traveling body frame 11 (see FIG. 3). Each of the crawler traveling devices 12L, 12R has a driving wheel 13 rotatably provided on the front side of the traveling body frame 11, a driven wheel 14 rotatably provided on the rear side of the traveling body frame 11, a plurality of rollers 15 rotatably provided between the driving wheel 13 and the driven wheel 14, and a rubber crawler belt (track) 16 wound around the driving wheel 13, the driven wheel 14, and the plurality of rollers 15. Each of the crawler traveling devices 12L, 12R has a left traveling motor 50L and a right traveling motor 50R (see FIG. 3) that rotate the left and right driving wheels 13, respectively, and a left braking device 52L and a right braking device 52R (see FIG. 2) that brake the rotation of the left and right driving wheels 13, respectively. The left and right brake devices 52L, 52R are electromagnetic brakes that are driven by command signals from a controller 60, which will be described later. The left and right brake devices 52L, 52R are what are called negative brakes, and are configured to fully operate when there is no command signal, and to adjust the braking force by operating electromagnetic force in response to a command signal.

[0017] The left and right traveling motors 50L and 50R are connected to the back wheels 11 and 12 of the traveling body 10 as shown in FIG. The left and right traveling motors 50L and 50R are driven by power supplied from the terry 90 via the left and right traveling inverters 51L and 51R, respectively. The traveling motors 50L and 50R are induction motors (AC motors) driven by AC power converted by the traveling inverters 51L and 51R. The outputs of the left and right traveling motors 50L and 50R are transmitted to the left and right driving wheels 13 and 13 via speed reducers (not shown), respectively, so that the left and right driving wheels 13 and 13 rotate. The left and right traveling motors 50L and 50R also have a function of generating regenerative electricity by being rotated by the left and right driving wheels 13 and 13 during deceleration traveling, etc. The left and right traveling motors 50L and 50R are controlled in rotation direction and rotation speed according to the operation direction and operation amount of a traveling operation lever 47 and a turning amount operation dial 48 provided in the operation box 40 described later. In the following description, when there is no need to particularly distinguish between the left-side traveling motor 50L and the right-side traveling motor 50R, they will simply be referred to as "traveling motors 50."

[0018] As shown in Figure 1, the mast 20 is configured to be vertically telescopic by combining a base mast 21 attached to the upper front side of the traveling body 10, a lower intermediate mast 22, an upper intermediate mast 23, and a tip mast 24 in a nested manner. The mast 20 is provided with a telescopic cylinder 25 (see Figure 2) therein, and is configured so that the entire mast 20 can be telescopically moved in the vertical direction by telescoping the telescopic cylinder 25. The tip mast 24 is provided with a work platform 30 that moves up and down in response to the telescopic movement of the mast 20.

[0019] As shown in Fig. 2, the telescopic cylinder 25 is driven by hydraulic oil discharged from a hydraulic pump 70 provided on the traveling body 10 and supplied through a telescopic control valve 71 to extend and retract the mast 20. The hydraulic pump 70 is driven by a pump drive motor 75. The pump drive motor 75 is rotated by power supplied from a battery 90 through a mast operation inverter 76. The drive direction and drive speed of the telescopic cylinder 25 are controlled according to the operation direction and operation amount of a mast operation lever 41 provided in an operation box 40, which will be described later.

[0020] As shown in Fig. 1, an operation box 40 equipped with various operation means is provided on the work platform 30 (or on the top of the tip mast 24). The operation box 40 is provided with a mast operation lever 41 for performing the extension and contraction operation of the mast 20 (the raising and lowering operation of the work platform 30). The mast operation lever 41 can be tilted forwards and backwards from a neutral position extending vertically, and is configured so that when the lever is released from the tilted state, it automatically returns to the neutral position by the force of a built-in spring. When the mast operation lever 41 is tilted, a mast operation signal is output corresponding to the tilt direction and operation amount with respect to the neutral position, and is input to a mast operation control section 60a of the controller 60.

[0021] The mast operation control unit 60a electromagnetically drives the spool of the extension / retraction control valve 71 in a drive direction and drive amount according to the input mast operation signal, thereby controlling the amount of hydraulic oil supplied from the hydraulic pump 70 to the telescopic cylinder 25, thereby controlling the drive direction and drive speed of the telescopic cylinder 25. Furthermore, the mast operation control unit 60a controls the power supplied from the battery 90 to the pump drive motor 75 via the mast operation inverter 76 in response to the input mast operation signal, thereby controlling the amount of hydraulic oil discharged from the hydraulic pump 70. Therefore, a worker on the work platform 30 can extend and retract the mast 20 by operating the mast operation lever 41, thereby raising and lowering the work platform 30 to a desired height position.

[0022] The operation box 40 is also provided with a travel control lever 47 and a turning amount control dial 48 for controlling the travel of the left and right crawler travel devices 12L, 12R. As shown in Fig. 3, the travel control lever 47 can be tilted forwards and backwards from a neutral position extending vertically, and is configured so that when released from a tilted state, it automatically returns to the neutral position by the force of a built-in spring. When the travel control lever 47 is tilted, A travel operation signal corresponding to the operation direction and operation amount based on the neutral position is output and input to the travel control unit 60b of the controller 60. The forward tilt operation of the travel operation lever 47 from the neutral position corresponds to a forward travel command for the left and right crawler travel devices 12L, 12R, and the larger the operation amount, the larger the target travel speed (target rotation speed of the travel motors 50L, 50R) of the crawler travel devices 12L, 12R during forward travel is set in the travel control unit 60b. The rearward tilt operation of the travel operation lever 47 corresponds to a backward travel command for the left and right crawler travel devices 12L, 12R, and the larger the operation amount, the larger the target travel speed (target rotation speed of the travel motors 50L, 50R) of the crawler travel devices 12L, 12R during backward travel is set in the travel control unit 60b. The operation of returning the travel control lever 47 to the neutral position corresponds to a command to stop the left and right crawler travel devices 12L, 12R.

[0023] The turning amount operation dial 48 can be twisted in the left and right directions from a neutral position (the position shown in FIG. 3), and is configured to automatically return to the neutral position by the force of a built-in spring when the hand is released from the twisted state. When the turning amount operation dial 48 is twisted, a turning operation signal corresponding to the operation direction and operation amount based on the neutral position is output and input to the traveling control unit 60b. A twisting operation of the turning amount operation dial 48 to the right from the neutral position corresponds to a turning travel command to the right of the left and right crawler traveling devices 12L, 12R, and the larger the operation amount to the right from the neutral position, the larger the target turning amount to the right is set in the traveling control unit 60b. A twisting operation of the turning amount operation dial 48 to the left from the neutral position corresponds to a turning travel command to the left of the left and right crawler traveling devices 12L, 12R, and the larger the operation amount to the left from the neutral position, the larger the target turning amount to the left is set in the traveling control unit 60b. The operation of returning the turning amount operation dial 48 to the neutral position corresponds to a command (straight running command) to set the turning amount of the left and right crawler traveling devices 12L, 12R to zero. In the following description, the "inner side of the turning direction" means the inner wheel side (the side with a relatively slow running speed) when the vehicle is turned, and the "outer side of the turning direction" means the outer wheel side (the side with a relatively fast running speed) when the vehicle body is turned. Therefore, when the vehicle body is turned to the right, the right traveling motor 50R corresponds to the "inner traveling motor 50 of the turning direction", and the left traveling motor 50L corresponds to the "outer traveling motor 50 of the turning direction". Also, when the vehicle body is turned to the left, the left traveling motor 50L corresponds to the "inner traveling motor 50 of the turning direction", and the right traveling motor 50R corresponds to the "outer traveling motor 50 of the turning direction".

[0024] When the driving control unit 60b receives an operation signal (driving operation signal, turning operation signal) from the driving operation lever 47 and the turning amount operation dial 48, it calculates a target rotation speed according to the operation signal, and controls the rotation speed command value (command frequency of AC power supplied to the left and right driving motors 50L, 50R by controlling the driving inverters 51L, 51R) output to the left and right driving inverters 51L, 51R so that the rotation speed of the left and right driving motors 50L, 50R follows the target rotation speed, thereby controlling the rotation speed of the left and right driving motors 50L, 50R. In this embodiment, as will be described in detail later, the vehicle can travel straight by synchronizing the rotation speeds (rotation speed command values) of the left and right driving motors 50L, 50R, and the vehicle can travel in a turning direction (slalom turning, pivot turning, spin turning) by applying a rotation speed difference to the rotation speeds (rotation speed command values) of the left and right driving motors 50L, 50R.

[0025] Here, Fig. 4 is a graph showing the relationship between the amount of operation of the turning amount operation dial 48 and the target rotation speeds of the left and right traveling motors 50L, 50R when the travel operation lever 47 is tilted forward a specified angle from the neutral position. In other words, Fig. 4 shows the transition of the target rotation speeds that are set when the amount of operation of the turning amount operation dial 48 is changed from 0 degrees to 60 degrees (maximum operation angle) while the amount of operation of the travel operation lever 47 is kept constant. In the figure, the horizontal axis shows the amount of operation of the turning amount operation dial 48, and the vertical axis shows the target rotation speeds of each traveling motor 50L, 50R. In the following, the rotation direction of the traveling motors 50L, 50R when the vehicle is traveling forward is defined as the "forward direction", and the rotation direction of the traveling motors 50L, 50R when the vehicle is traveling backward is defined as the "reverse direction". Therefore, in the target rotation speed on the vertical axis shown in the figure, a positive value (sign) of the target rotation speed indicates the target rotation speed in the forward direction, and a negative value (sign) of the target rotation speed indicates the target rotation speed in the reverse direction. In the following explanation, the traveling control when the turning amount operation dial 48 is twisted to the right is illustrated, but the traveling control when the turning amount operation dial 48 is twisted to the left is the same as the basic traveling control except that the traveling motor 50 on the inside of the turning direction and the traveling motor 50 on the outside of the turning direction are reversed on the left and right.

[0026] In the following description, the target rotation speed of the travel motors 50L, 50R during straight travel is referred to as the "reference target rotation speed." This reference target rotation speed is a target rotation speed determined according to the amount of operation of the travel operation lever 47 during straight travel, and is the same target rotation speed for both the left and right travel motors 50L and 50R during straight travel. The figure shows an example of the reference target rotation speed (V x 100%) when the travel operation lever 47 is tilted forward by a predetermined angle. Although details will be described later, the target rotation speeds of the left and right travel motors 50L, 50R are calculated by multiplying the reference target rotation speed determined according to the amount of operation of the travel operation lever 47 by a predetermined deceleration rate determined according to the amount of operation of the turning amount operation dial 48 (target rotation speed = reference target rotation speed x deceleration rate).

[0027] First, when the amount of operation of the turning amount operation dial 48 is 0 degrees, the target rotation speeds of the left and right traveling motors 50L, 50R are both set to a reference target rotation speed (V×100%) according to the amount of operation of the traveling operation lever 47. As a result, the left traveling motor 50L and the right traveling motor 50R are controlled to have the same rotation direction (forward rotation direction) and the same rotation speed (reference target rotation speed), so that the vehicle travels straight (forward traveling). Note that in this embodiment, when the amount of operation of the turning amount operation dial 48 to the right is 5 degrees or less, the vehicle is controlled to travel straight (forward traveling).

[0028] Next, when the turning amount operation dial 48 is turned to the right by 30 degrees, the target rotation speed of the left traveling motor 50L on the outside of the turning direction is reduced to "V x 100% - ΔV1", and the target rotation speed of the right traveling motor 50R on the inside of the turning direction is reduced to "V x 100% - (ΔV1 + ΔV2)". As an example, V1 = V x 50%, V2 = V x 20%. As a result, the left and right traveling motors 50L, 50R are rotated in the same rotation direction (forward direction), and the rotation speed of the right traveling motor 50R is controlled to be slower than the rotation speed of the left traveling motor 50R, so that the vehicle performs a slalom turning in the right direction. In this embodiment, when the operation amount of the turning amount operation dial 48 in the right direction is more than 5 degrees and less than 40 degrees, the vehicle is controlled to perform a slalom turning (gentle turning) in the right direction.

[0029] Next, when the turning amount operation dial 48 is turned 45 degrees to the right, the target rotation speed of the left traveling motor 50L on the outside of the turning direction drops to "V x 100% - ΔV3" (ΔV3>ΔV1), and the target rotation speed of the right traveling motor 50R on the inside of the turning direction drops to "0". As a result, the left traveling motor 50L on the outside of the turning direction is rotated in the forward direction, and the right traveling motor 50R on the inside of the turning direction is controlled to a state of stopping rotation, so that the vehicle pivots to the right. In this embodiment, when the operation amount of the turning amount operation dial 48 is 40 degrees or more and 45 degrees or less, the vehicle is controlled to pivot to the right.

[0030] Next, when the turning amount control dial 48 is turned rightward by 55 degrees or more, the target rotation speed of the left traveling motor 50L on the outside of the turning direction is reduced to "V×100%-ΔV4" ( The target rotation speed of the right-side traveling motor 50R on the inside of the turning direction is reduced to "-(V×100%-ΔV4)". As a result, the left-side traveling motor 50L on the outside of the turning direction and the right-side traveling motor 50R on the inside of the turning direction are controlled to rotate at a constant speed in the reverse and forward directions, respectively, so that the vehicle makes a spin turn to the right.

[0031] [Main loop processing] Next, the main loop process of this embodiment will be described. Fig. 5 is a flowchart of the main loop process of this embodiment. The control routine of this main loop process is repeatedly executed at a control period of, for example, several ms to several tens of ms (a control period of "50 ms" in this embodiment).

[0032] First, in step S1, the controller 60 determines whether a predetermined time has passed since the previous process execution (previous control cycle). The predetermined time is a time value corresponding to the current control cycle (50 ms). If the predetermined time has not passed since the previous process execution (step S1: NO), the controller 60 waits until the predetermined time has passed since the previous process execution.

[0033] When the controller 60 determines that a predetermined time has elapsed since the previous process execution (step S1: YES), the controller 60 proceeds to the input process of step S2. In this input process, signals currently being output from the operation box 40 and various detectors are input.

[0034] Next, in various control processes in step S3, various control processes are executed based on the input information acquired in the input process in step S2 described above, such as a mast output control process for determining an output command for controlling the mast 20, and a traveling output control process for determining an output command for controlling the crawler traveling devices 12L, 12R. The details of the traveling output control process will be described later (see FIG. 6).

[0035] Next, in a total output determination process in step S4, the total outputs (total output signals) to be output in the current control cycle are determined based on the information determined in the various control processes in step S3 described above.

[0036] Next, in the output process of step S5, the output signal (command signal) determined in the total output determination process of step S4 described above is output to control devices such as the expansion / contraction control valve 71 and the traveling inverters 51L, 51R. After that, the processes from steps S1 to S5 described above are repeatedly executed at intervals of a predetermined time (control period).

[0037] [Running output control process] Next, the running output control process of this embodiment will be described. Fig. 6 is a flowchart of the running output control process of this embodiment. The running output control process is a process that is called and executed as a subroutine every time various control processes (step S3) of the main loop process are executed. In other words, the control routine of this running output control process is also repeatedly executed at a control period of, for example, several ms to several tens of ms (a control period of "50 ms" in this embodiment).

[0038] This driving output control process is a control that is mainly executed by the driving control unit 60b of the controller 60. As shown in Fig. 2, the driving control unit 60b includes a rotation speed calculation unit 61 that calculates the target rotation speed and the rotation speed command value of the left and right driving motors 50L, 50R, a driving mode determination unit 62 that determines the driving mode of the vehicle, and a synchronization determination unit 63 that determines the execution state of left and right synchronization control described later. The driving control unit 60 includes an acceleration determining unit 64 that determines the acceleration (rotational acceleration) of the left and right driving motors 50L, 50R, and a storage unit (memory) 65 that stores various information required for this driving control.

[0039] <1. Target rotation speed determination process> First, in step S11, the rotation speed calculation unit 61 executes a target rotation speed determination process. This target rotation speed determination process is a process for determining the target rotation speeds of the left and right traveling motors 50L, 50R. The "target rotation speed" is calculated by multiplying a reference target rotation speed set according to the operation amount of the traveling operation lever 47 by a deceleration rate set according to the operation amount of the turning amount operation dial 48 (target rotation speed = reference target rotation speed x deceleration rate).

[0040] As described above, the "reference target rotation speed" is the target rotation speed during straight-ahead driving. Here, FIG. 7 is a graph showing the relationship between the operation amount of the travel operation lever 47 and the reference target rotation speed. In the figure, the horizontal axis shows the operation amount of the travel operation lever 47, and the vertical axis shows the reference target rotation speed. As shown in FIG. 7, this reference target rotation speed is approximately proportional to the operation amount of the travel operation lever 47, so that the smaller the operation amount of the travel operation lever 47, the smaller the reference target rotation speed becomes, and the larger the operation amount of the travel operation lever 47, the larger the reference target rotation speed becomes. Note that FIG. 7 shows a case where the travel operation lever 47 is operated forward (forward direction), but if the travel operation lever 47 is operated backward (reverse direction), the positive and negative of the reference target rotation speed will be reversed.

[0041] The "deceleration rate" is a ratio for correcting the target rotation speed (a percentage when the reference target rotation speed is a deceleration rate of "100%": %), and is variably set according to the amount of operation of the turning amount operation dial 48. Here, FIG. 8 is a graph showing the relationship between the amount of operation of the turning amount operation dial 48 and the deceleration rate. In the figure, the horizontal axis indicates the amount of operation of the turning amount operation dial 48, and the vertical axis indicates the deceleration rate. For example, when the deceleration rate is 100%, the target rotation speed is the same as the reference target rotation speed (reference target rotation speed x 100%), when the deceleration rate is 50%, the target rotation speed is half the reference target rotation speed (reference target rotation speed x 50%), when the deceleration rate is 0%, the target rotation speed is 0 (reference target rotation speed x 0%), and when the deceleration rate is -A%, the target rotation speed is a target rotation speed in the opposite direction to the reference target rotation speed (reference target rotation speed x -A%). Note that FIG. 8 illustrates an example in which the travel operation lever 47 is tilted forward (in the forward direction); however, if the travel operation lever 47 is tilted backward (in the reverse direction), the positive and negative deceleration rates will be reversed.

[0042] Here, when the amount of operation of the turning amount operation dial 48 is 5 degrees or less, the deceleration rate of the left traveling motor 50L and the deceleration rate of the right traveling motor 50R are both set to 100% (target rotation speed = reference target rotation speed). When the amount of operation of the turning amount operation dial 48 is in the range of more than 5 degrees and less than 40 degrees, the deceleration rates of the left and right traveling motors 50L, 50R are both set to positive values, but the deceleration rate of the traveling motor 50 on the inside of the turning direction is smaller than the deceleration rate of the traveling motor 50 on the outside of the turning direction. When the amount of operation of the turning amount operation dial 48 is 40 degrees or more and 45 degrees or less, the deceleration rate of the traveling motor 50 on the outside of the turning direction is a positive value, and the deceleration rate of the traveling motor 50 on the inside of the turning direction is 0%. When the amount of operation of the turning amount operation dial 48 exceeds 45 degrees, the deceleration rate of the traveling motor 50 on the outside of the turning direction and the deceleration rate of the traveling motor 50 on the inside of the turning direction are opposite values.

[0043] <2. Driving mode determination process> Next, in step S12, the driving mode determination unit 62 executes a driving mode determination process. The driving mode determination process is a process for determining a current driving mode and a previous driving mode, which will be described later.

[0044] As shown in FIG. 9, the "driving mode" includes a straight driving mode, a slalom turning driving mode (gentle turning driving mode), a pivot turning driving mode, and a spin turning driving mode. The running mode is a driving mode in which the vehicle travels straight ahead. The slalom turning driving mode is a driving mode in which the vehicle travels in a slalom manner (gentle turning). The pivot turning driving mode is a driving mode in which the vehicle travels in a pivot manner. The spin turning driving mode is a driving mode in which the vehicle travels in a spin manner. Hereinafter, the slalom turning driving mode, pivot turning driving mode, and spin turning driving mode may be collectively referred to as the "turning driving modes."

[0045] (Current driving mode) The travel mode determination unit 62 determines the current travel mode based on the target rotation speed and the target rotation direction of the left and right travel motors 50L, 50R determined in the current control cycle. The current travel mode is a travel mode that conforms to the operator's current operation intention, and is determined based on the target rotation speed and the target rotation direction that are set according to the operation amount of the travel operation lever 47 and the turning amount operation dial 48 input in the current control cycle. The target rotation direction of each travel motor 50L, 50R is specified by the sign of the target rotation speed (positive is the forward rotation direction, negative is the reverse rotation direction). As described above, if the sign of the target rotation speed is positive, it indicates that the target rotation direction is the forward rotation direction, and if the sign of the target rotation speed is negative, it indicates that the target rotation direction is the reverse rotation direction.

[0046] The travel mode determination unit 62 determines that the current travel mode is the straight travel mode when the target rotation directions of the left and right travel motors 50L, 50R are the same and the difference in the target rotation speeds of the left and right travel motors 50L, 50R is equal to or less than a predetermined value (5% of the reference target rotation speed). The travel mode determination unit 62 also determines that the current travel mode is the slalom turning travel mode when the target rotation directions of the left and right travel motors 50L, 50R are the same and the difference in the target rotation speeds of the left and right travel motors 50L, 50R exceeds a predetermined value (5% of the reference target rotation speed). The travel mode determination unit 62 also determines that the current travel mode is the pivot turning travel mode when the target rotation speed of one of the left and right travel motors 50L, 50R is 0 (the target rotation speed is a speed at which rotation is stopped). In addition, the driving mode determination unit 62 determines that the current driving mode is the spin turning driving mode when the target rotation directions of the left and right driving motors 50L, 50R are opposite (when the target rotation direction of one driving motor 50 is the forward direction and the target rotation direction of the other driving motor 50 is the reverse direction).

[0047] (Previous driving mode) The traveling mode determination unit 62 determines the previous traveling mode based on the rotation speed command value and the command rotation direction determined in step S15 (rotation speed command value determination process) of the previous control period. The "rotation speed command value" is a command value (command rotation speed) of the rotation speed for rotating and driving the left and right traveling motors 50L, 50R. As shown in FIG. 14 described later, this rotation speed command value is updated so as to approach the target rotation speed for each control period (updated until the target rotation speed is reached). Here, in this embodiment, on the premise that the actual rotation speeds of the left and right traveling motors 50L, 50R follow the rotation speed command value, the rotation speed command value output to the left and right traveling motors 50L, 50R (left and right traveling inverters 51L, 51R) in the previous control period is estimated as the actual rotation speeds of the left and right traveling motors 50L, 50R at the time of the previous control period, and the previous traveling mode is determined based on this previous rotation speed command value. The commanded rotation direction of the left and right travel motors 50L, 50R is determined by the sign of the rotation speed command value (positive indicates a forward rotation direction, negative indicates a reverse rotation direction). If the sign of the rotation speed command value is positive, it indicates that the commanded rotation direction is a forward rotation direction, and if the sign of the rotation speed command value is negative, it indicates that the commanded rotation direction is a reverse rotation direction.

[0048] The driving mode determination unit 62 determines that the previous driving mode was a straight-line driving mode when the command rotation directions of the left and right driving motors 50L, 50R are the same and the difference between the rotation speed command values ​​of the left and right driving motors 50L, 50R is less than a predetermined value (5% of the reference target rotation speed). Furthermore, when the commanded rotation directions of the left and right traveling motors 50L, 50R are the same and the difference between the rotation speed command values ​​of the left and right traveling motors 50L, 50R exceeds a predetermined value (5% of the reference target rotation speed), the traveling mode determination unit 62 determines that the previous traveling mode was the slalom turning traveling mode. Furthermore, when the rotation speed command value of one of the left and right traveling motors 50L, 50R is 0 (when the rotation speed command value commands the rotation to stop), the traveling mode determination unit 62 determines that the previous traveling mode was the pivot turning traveling mode. Furthermore, when the commanded rotation directions of the left and right traveling motors 50L, 50R are opposite (when the commanded rotation direction of one traveling motor 50 is the forward direction and the commanded rotation direction of the other traveling motor 50 is the reverse direction), the traveling mode determination unit 62 determines that the previous traveling mode was the spin turning traveling mode.

[0049] <3. Left / right synchronization determination process> Next, in step S13, the synchronization determination unit 63 executes left-right synchronization determination processing. The left-right synchronization determination processing is processing for determining the execution state of left-right synchronization control described later. In this embodiment, as will be described later in detail, when the vehicle's driving mode is switched from a turning driving mode (previous driving mode) to a straight driving mode (present driving mode), control (left-right synchronization control) is executed to synchronize the rotation speed command value of the left-side driving motor 50L and the rotation speed command value of the right-side driving motor 50R. In this left-right synchronization control, the rotation speed of the driving motor 50 on the outside of the turning direction is maintained constant without being accelerated until the rotation speed command value of the driving motor 50 on the inside of the turning direction among the left and right driving motors 50L and 50R reaches the rotation speed command value of the driving motor 50 on the outside of the turning direction, and the acceleration of the driving motor 50 on the inside of the turning direction is changed to acceleration (accelerations D and E described later) greater than basic accelerations (accelerations A, B, and C described later).

[0050] FIG. 10 is a graph for explaining the left-right synchronization determination process. FIG. 10 shows the left-right synchronization control when the vehicle moves from a spin-turning motion to the right to a straight-line motion. In the figure, the horizontal axis indicates time, and the vertical axis indicates the rotation speed command value of the traveling motors 50L and 50R. The synchronization determination unit 63 determines whether the left-right synchronization control is being executed or not based on the ON / OFF of the synchronization determination flag set in the storage unit 65. The synchronization determination flag is set to ON (=1) when the vehicle's traveling mode is switched from a turning traveling mode (previous traveling mode) to a straight-line traveling mode (present traveling mode) based on the result of the above-mentioned traveling mode determination process. In addition, the synchronization determination flag is set to OFF (=0) when the rotation speed command value of the traveling motor 50 on the inside of the turning direction reaches the rotation speed command value of the traveling motor 50 on the outside of the turning direction based on the result of the previous rotation speed command value determination process (the rotation speed command value output in the previous control period). The synchronization determination unit 63 determines that the left-right synchronization control is being executed when the synchronization determination flag is set to ON. Furthermore, when the synchronization determination flag is switched from ON to OFF, the synchronization determination unit 63 determines that the left-right synchronization control is completed.

[0051] <4. Acceleration determination process> Next, in step S14, the acceleration determination unit 64 executes an acceleration determination process. The acceleration determination process is a process for determining the acceleration (rotational acceleration) of the left and right traveling motors 50L, 50R based on the operation information of the traveling operation lever 47, the operation information of the turning amount operation dial 48, the result of the traveling mode determination process (current traveling mode, previous traveling mode), the result of the left and right synchronization determination process, and the like. The "acceleration" is the change amount (addition amount) of the rotation speed command value per unit time. The unit time is the time corresponding to the control cycle (50 ms) of the traveling output process. That is, in this embodiment, the addition amount added to the rotation speed command value for each control cycle (every 50 ms) is defined as the "acceleration". Therefore, the rotation speed command value output in the current control cycle is derived by adding the acceleration determined in the current control cycle to the rotation speed command value output in the previous control cycle. The acceleration includes not only positive acceleration when accelerating in the rotation direction of the traveling motors 50L, 50R, but also negative acceleration (deceleration) when decelerating in the rotation direction of the traveling motors 50L, 50R. Here, "large acceleration" means that the absolute value of the acceleration (positive acceleration, negative acceleration) is large.

[0052] In this embodiment, as shown in Figs. 11 and 12, accelerations A, B, C, D, and E (E1, E2) are set as the accelerations of the left and right travel motors 50L and 50R. The accelerations A, B, and C are accelerations (also called "basic accelerations") used when normal travel control is performed. In the conventional travel control (see Fig. 15(A)), only the basic accelerations (accelerations A, B, and C) are set as the accelerations of the left and right travel motors 50L and 50R. On the other hand, the accelerations D and E (E1, E2) are accelerations used when the left and right synchronous control of the left and right travel motors 50L and 50R is performed. Each of the accelerations A to E is set to a unique value, but may be a value that is appropriately changed within a predetermined range.

[0053] (acceleration A) When the acceleration determination unit 64 determines that the vehicle is about to start traveling (starting time) based on the operation information from the travel operation lever 47, the acceleration determination unit 64 determines that the acceleration of the left and right travel motors 50L, 50R is the acceleration A. This acceleration A is a positive acceleration (acceleration A>0). Here, when the acceleration determination unit 64 determines that the travel start operation of the travel operation lever 47 has been performed (the travel operation lever 47 has been tilted from the stopped state of the left and right travel motors 50L, 50R), it determines that the vehicle is about to start traveling. In addition, the acceleration determination unit 64 maintains the acceleration of the left and right travel motors 50L, 50R at the acceleration A until a certain time has elapsed since the vehicle started traveling. In this embodiment, the magnitude of the acceleration A is set so that the rotation speed (rotation speed command value) of the left and right travel motors 50L, 50R reaches a target rotation speed according to the operation amount of the travel operation lever 47 and the turning amount operation dial 48 after a certain time has elapsed since the vehicle started traveling.

[0054] (acceleration B) When the acceleration determination unit 64 determines that the vehicle is at a stop based on operation information from the travel operation lever 47, etc., it determines the acceleration of the left and right travel motors 50L, 50R to be acceleration B. This acceleration B is negative acceleration (acceleration B<0). Here, when the acceleration determination unit 64 determines that the travel stop operation of the travel operation lever 47 has been performed (the travel operation lever 47 has been returned to the neutral position), it determines that the vehicle is at a stop. In addition, the acceleration determination unit 64 maintains the acceleration of the left and right travel motors 50L, 50R at acceleration B until the vehicle is at a stop (until the rotation speed command values ​​of the left and right travel motors 50L, 50R become 0).

[0055] (acceleration C) When the acceleration determination unit 64 determines that the vehicle is accelerating or decelerating while traveling (excluding predetermined acceleration or deceleration) based on the operation information of the traveling operation lever 47, the result of the target rotation speed determination process (target rotation speed), the result of the previous rotation speed command value determination process (previous rotation speed command value), the result of the traveling mode determination process (current traveling mode, previous traveling mode), etc., it determines the acceleration of the left and right traveling motors 50L, 50R to be acceleration C. This acceleration C includes acceleration during acceleration and deceleration, and the acceleration C during acceleration is positive acceleration (C>0), and the acceleration C during deceleration is negative acceleration (C<0). Here, the acceleration determination unit 64 determines that the vehicle is accelerating or decelerating while traveling when the rotation speed command value output to the left and right traveling inverters 51L, 51R does not reach the target rotation speed while the traveling operation lever 47 is tilted. Note that "except for specified acceleration / deceleration" means excluding acceleration / deceleration of other accelerations A, B, D, E (when starting to travel, when stopping to travel, and when switching from turning to straight travel mode). The acceleration determination unit 64 maintains the acceleration C until the rotation speed command value (command rotation speed) output to the left and right traveling inverters 51L, 51R reaches the target rotation speed.

[0056] (acceleration D) When it is determined that the left-right synchronous control is being executed when the vehicle's traveling mode is switched from the slalom turning traveling mode (previous traveling mode) to the straight traveling mode (present traveling mode) or when the vehicle's traveling mode is switched from the pivot turning traveling mode (previous traveling mode) to the straight traveling mode (present traveling mode) based on the result of the traveling mode determination process (current traveling mode, previous traveling mode) and the result of the left-right synchronization determination process, the acceleration determination unit 64 determines the acceleration of the traveling motor 50 on the outside of the turning direction to be 0 and determines the acceleration of the traveling motor 50 on the inside of the turning direction to be the acceleration D. Here, the acceleration determination unit 64 maintains the acceleration of the traveling motor 50 on the outside of the turning direction to be 0 and maintains the acceleration of the traveling motor 50 on the inside of the turning direction to be the acceleration D until the left-right synchronous control is completed, that is, until the rotation speed command values ​​of the left and right traveling motors 50L, 50R become equal (until the rotation speed of the traveling motor 50 on the inside of the turning direction catches up with the rotation speed of the traveling motor 50 on the outside of the turning direction). This acceleration D is a positive acceleration (D>0). Like the above-mentioned acceleration C, the acceleration D is the acceleration during vehicle travel (excluding when the vehicle starts traveling and when the vehicle stops traveling), but in order to shorten the transition time from turning to straight traveling and improve the followability to traveling operations, the acceleration D is set to an acceleration greater than the acceleration C (for example, twice the acceleration). When the acceleration determination unit 64 determines that the left and right synchronization control is completed, it returns the accelerations of the left and right traveling motors 50L, 50R to the basic accelerations (the accelerations A to C corresponding to the traveling state at that time).

[0057] (acceleration E) When it is determined that the left-right synchronization control is being executed when the vehicle's traveling mode is switched from the spin turning traveling mode (previous traveling mode) to the straight traveling mode (present traveling mode) based on the result of the traveling mode determination process (current traveling mode, previous traveling mode) and the result of the left-right synchronization determination process, the acceleration determination unit 64 determines the acceleration of the traveling motor 50 on the outside of the turning direction to be 0 and the acceleration of the traveling motor 50 on the inside of the turning direction to be the acceleration E (E1, E2). Here, the acceleration determination unit 64 maintains the acceleration of the traveling motor 50 on the outside of the turning direction to be 0 and the acceleration of the traveling motor 50 on the inside of the turning direction to be the acceleration E (E1, E2) until the left-right synchronization control is completed, that is, until the rotation speed command values ​​of the left and right traveling motors 50L, 50R become equal (until the rotation speed of the traveling motor 50 on the inside of the turning direction catches up with the rotation speed of the traveling motor 50 on the outside of the turning direction). At this time, when the traveling mode of the vehicle shifts from the spin turning traveling mode (previous traveling mode) to the straight traveling mode (present traveling mode), the rotation speed command value of the traveling motor 50 on the inside of the turning direction changes from the rotation speed command value in the reverse direction (the rotation speed command value of a negative value) to the rotation speed command value in the forward direction (the rotation speed command value of a positive value), so that the magnitude of the acceleration E is switched around the boundary point where the rotation speed command value becomes 0. That is, the acceleration E1 is set from the start of the left-right synchronization control until the rotation speed command value of the traveling motor 50 on the inside of the turning direction becomes 0, and the acceleration E2 is set from the start of the left-right synchronization control until the rotation speed command value of the traveling motor 50 on the inside of the turning direction becomes 0 and catches up with the rotation speed of the traveling motor 50 on the outside of the turning direction. The acceleration E1 is a negative acceleration (E1<0) and is greater than the acceleration B. The acceleration E2 is a positive acceleration (E2>0) and is greater than the acceleration A. Here, the acceleration E1 is an acceleration for decelerating the vehicle until the rotational speed command value becomes 0, similar to the acceleration B described above, but it is set to an acceleration greater than the acceleration B in order to shorten the transition time from turning to straight-ahead driving and improve response to driving operations.Similarly, the acceleration E2 is an acceleration for accelerating the rotation speed command value from 0, like the acceleration A described above, but in order to shorten the transition time from turning to straight driving and improve the followability to driving operations, it is set to an acceleration greater than the acceleration A. When the acceleration determination unit 64 determines that the left and right synchronization control is completed, it returns the accelerations of the left and right driving motors 50L, 50R to the basic accelerations (the accelerations A to C corresponding to the driving state at that time).

[0058] <5. Rotational speed command value determination process> Next, in step S15, the rotation speed calculation unit 61 executes a rotation speed command value determination process. The rotation speed command value determination process is a process for determining the rotation speed command values ​​of the left and right traveling motors 50L, 50R. The rotation speed calculation unit 61 adds the acceleration determined in the acceleration determination process of the current control cycle to the rotation speed command value determined in the previous control cycle (the previous rotation speed command value stored in the storage unit 65) to determine the rotation speed command value (the current rotation speed command value) to be output in the current control cycle. The current rotation speed command value determined here is output to each traveling inverter 51L, 51R in the output process of the main loop process (the output process of the current control cycle). In addition, the current rotation speed command value is stored in the storage unit 65 as history information to be used in the next control cycle.

[0059] Here, Fig. 13 is a flowchart of the rotation speed command value determination process (step S15), and Fig. 14 is a graph showing a schematic change in the rotation speed command value over time. This rotation speed command value determination process (step S15) is a process that is called and executed as a subroutine every time the running power control process is executed.

[0060] First, in step S21, the rotation speed calculation unit 61 determines whether or not the target rotation speed determined in the target rotation speed determination process (step S11) for the current control cycle matches the rotation speed command value output in the previous control cycle (the previous rotation speed command value stored in the storage unit 65). If the target rotation speed determined in the current control cycle matches the previous rotation speed command value (step S21: YES), the process proceeds to step S22. In step S22, the rotation speed calculation unit 61 sets the target rotation speed as the rotation speed command value to be output in the current control cycle (i.e., maintains the previous rotation speed command value).

[0061] On the other hand, if the target rotation speed determined in the current control cycle does not match the previous rotation speed command value (step S21: NO), the process proceeds to step S23. In step S23, the rotation speed calculation unit 61 calculates the current rotation speed command value by adding the acceleration determined in the acceleration determination process (step S14) to the previous rotation speed command value, as shown in FIG.

[0062] Next, in step S24, the rotation speed calculation unit 61 determines whether or not the rotation speed command value calculated in step S23 exceeds the target rotation speed. If this rotation speed command value exceeds the target rotation speed (S24: YES), the process proceeds to step S25. In step S25, the rotation speed calculation unit 61 sets the target rotation speed as the current rotation speed command value. That is, if the current rotation speed command value exceeds the target rotation speed, the rotation speed calculation unit 61 determines the rotation speed command value with the target rotation speed as the upper limit value (the upper limit value of the rotation speed command value becomes the target rotation speed).

[0063] On the other hand, if the rotation speed command value calculated in step S23 is equal to or lower than the target rotation speed (S24: NO), the process proceeds to step S26. In other words, if the current rotation speed command value is equal to or lower than the target rotation speed, the rotation speed command value calculated in step S23 (the value obtained by adding the acceleration to the previous rotation speed command value) is determined as the current rotation speed command value.

[0064] Next, in step S26, the current rotation speed command value determined in step S22 or step S25 is stored in the storage unit 65, and this rotation speed command value determination process (S15) is terminated.

[0065] Next, the driving control at the time of switching the driving mode will be described as a characteristic function of this embodiment. Fig. 15 compares the driving control at the time of switching the vehicle driving mode from the spin turning driving mode (previous driving mode) to the straight driving mode (present driving mode) between this embodiment and the conventional technology. 1 is a diagram for explaining the control of the driving motor 50L, 50R, in which (A) shows the driving control of the conventional technology and (B) shows the driving control of this embodiment. The horizontal axis in the diagram indicates time, and the vertical axis in the diagram indicates the rotation speed command value of each of the driving motors 50L, 50R. In the following explanation, it is assumed that the operation amount (reference target rotation speed) of the driving operation lever 47 is constant.

[0066] First, the driving control of the conventional technology will be described with reference to Fig. 15(A). In the figure, the section from time T0 to T1 is the section during spin turning, the section from time T1 to T5 is the section during transition from spin turning to straight driving (during synchronization of the driving motors 50L, 50R), and the section after time T5 is the section during straight driving. Note that in the conventional technology, only basic accelerations (accelerations A, B, C) are set as the accelerations of the left and right driving motors 50L, 50R.

[0067] First, at time T0, the vehicle is making a spin turn to the right. At this time, the rotation speed command value of the left traveling motor 50L on the outside of the turning direction is set to the target rotation speed N1, and the rotation speed command value of the right traveling motor 50R on the inside of the turning direction is set to the target rotation speed -N1.

[0068] At time T1, the turning amount operation dial 48 is returned to the neutral position (0 degree operation position), and the vehicle's driving mode is switched from the spin turning driving mode (previous driving mode) to the straight driving mode (present driving mode). Also, by returning the turning amount operation dial 48 to the neutral position, the deceleration rates of the left and right traveling motors 50L, 50R are set to 100%, and the target rotation speeds of the left and right traveling motors 50L, 50R are changed to the reference target rotation speed N2 according to the operation amount of the driving operation lever 47.

[0069] Also, at this time point T1, the acceleration of the left traveling motor 50L on the outside of the turning direction is set to acceleration C, and the acceleration of the right traveling motor 50R on the inside of the turning direction is set to acceleration B. Note that the acceleration of the right traveling motor 50R is changed from acceleration B (acceleration B when traveling stops) to acceleration A (acceleration A when traveling starts) when the rotation speed command value of this right traveling motor 50R reaches 0.

[0070] Subsequently, at time T3, the rotation speed command value of the left-side traveling motor 50L, which is on the outside in the turning direction, reaches the target rotation speed (reference target rotation speed) N2. In other words, the rotation speed command value of the left-side traveling motor 50L reaches the target rotation speed N2 at an earlier timing than the rotation speed command value of the right-side traveling motor 50R. After this rotation speed command value of the left-side traveling motor 50L reaches the target rotation speed N2, the rotation speed command value of the left-side traveling motor 47 maintains the target rotation speed (reference target rotation speed) N2 as long as the operation amount of the travel operation lever 47 is not changed (as long as the reference target rotation speed N2 is not changed).

[0071] Next, at time T5, the rotation speed command value of the right-side traveling motor 50R, which is on the inside of the turning direction, reaches the target rotation speed (reference target rotation speed) N2. That is, at this time T5, the rotation speed command value of the right-side traveling motor 50R catches up with the rotation speed command value of the left-side traveling motor 50L, and the rotation speed command values ​​of the left and right traveling motors 50L, 50R become synchronized, and the vehicle starts traveling straight. As a result, the vehicle travels straight at the target traveling speed (traveling speed corresponding to the target rotation speed N2).

[0072] In this way, in the conventional driving control, when switching from the turning driving mode (previous driving mode) to the straight driving mode (present driving mode), the rotation speed command values ​​of the left and right driving motors 50L, 50R are not synchronized until both of them reach the target rotation speed (reference target rotation speed) N2. Therefore, the timing at which straight driving starts after the driving mode is switched (the timing of synchronization) is delayed from the operator's intention. This causes the vehicle to turn for a longer period than expected.

[0073] Next, the driving control of this embodiment will be described with reference to Fig. 15(B). In the figure, the section from time T0 to T1 is the section during spin turning, the section from time T1 to T2 is the section during the transition from spin turning to straight driving (during synchronization of the driving motors 50L, 50R), and the section after time T2 is the section during straight driving.

[0074] First, at time T0, the vehicle is making a spin turn to the right. At this time, the rotation speed command value of the left traveling motor 50L on the outside of the turning direction is set to the target rotation speed N1, and the rotation speed command value of the right traveling motor 50R on the inside of the turning direction is set to the target rotation speed -N1.

[0075] At time T1, the turning amount operation dial 48 is returned to the neutral position (0 degree operation position), and the vehicle's driving mode is switched from the spin turning driving mode (previous driving mode) to the straight driving mode (present driving mode). Also, by returning the turning amount operation dial 48 to the neutral position, the deceleration rate of the left and right traveling motors 50L, 50R is set to 100%, and the target rotation speeds of the left and right traveling motors 50L, 50R are changed to the reference target rotation speed N2 according to the operation amount of the traveling operation lever 47. Note that up to this point, the driving control is almost the same as that of the conventional technology.

[0076] Here, in the travel control of this embodiment, at this time point T1, left-right synchronous control is started to synchronize the rotation speeds (rotation speed command value) of the left and right traveling motors 50L, 50R. This left-right synchronous control is executed until the rotation speed (rotation speed command value) of the left traveling motor 50L on the outside of the turning direction and the rotation speed (rotation speed command value) of the right traveling motor 50R on the inside of the turning direction are synchronized. During the execution of this left-right synchronous control, the acceleration of the left traveling motor 50L on the outside of the turning direction is set to 0, so that the rotation speed command value of the left traveling motor 50L is maintained at the previous target rotation speed N1. In other words, the rotation speed command value of the left traveling motor 50L maintains the rotation speed command value (target rotation speed N1) during spin turning until the rotation speed command value of the right traveling motor 50R catches up.

[0077] On the other hand, the acceleration of the right-side traveling motor 50R on the inside of the turning direction is set to an acceleration E1 greater than the acceleration B (basic acceleration) until the rotation speed command value of this right-side traveling motor 50R becomes 0, and is set to an acceleration E2 greater than the acceleration A (basic acceleration) from when the rotation speed command value of this right-side traveling motor 50R becomes 0 until it reaches the rotation speed command value of the left-side traveling motor 50L. In other words, the rotation speed command value of the right-side traveling motor 50R on the inside of the turning direction is changed to an acceleration (accelerations E1, E2) greater than the basic accelerations (accelerations A, B) until it catches up with the rotation speed command value of the left-side traveling motor 50L on the outside of the turning direction. As a result, while this left-right synchronization control is being executed, the rotational speed (rotational speed command value) of the left-side traveling motor 50L is not accelerated, and only the rotational speed (rotational speed command value) of the right-side traveling motor 50R is rapidly accelerated. This makes it possible to eliminate the difference with the rotational speed command value of the left-side traveling motor 50 by the increase in the rotational speed command value of the right-side traveling motor 50R, and efficiently bring the difference between the two rotational speed command values ​​closer to zero.

[0078] Subsequently, at time T2, the rotation speed command value of the right-side traveling motor 50R reaches the rotation speed command value of the left-side traveling motor 50L, and the rotation speed command values ​​of the left and right traveling motors 50L, 50R are synchronized (left and right synchronization control is completed), and the vehicle starts traveling straight ahead. In this embodiment, by completing synchronization at the rotation speed command value (previous target rotation speed N1) at the stage before the rotation speed command values ​​of the left and right traveling motors 50L, 50R reach the target rotation speed (reference target rotation speed) N2 in this way, the rotation speed command values ​​of the left and right traveling motors 50L, 50R are synchronized. This makes it possible to significantly shorten the time until the vehicle reaches its target position (the time until the vehicle starts traveling straight ahead).

[0079] At time T2, the rotation speed command values ​​of the left and right traveling motors 50L, 50R are synchronized, and the acceleration of the left and right traveling motors 50L, 50R is changed to the normal acceleration C (basic acceleration). After time T2, the left and right traveling motors 50L, 50R are rotated at the same rotation speed (rotation speed command value).

[0080] Next, at time T4, the rotational speed command values ​​of the left and right driving motors 50L, 50R reach the target rotational speed (reference target rotational speed) N2, causing the vehicle to travel straight at the target driving speed (the driving speed corresponding to the target rotational speed N2).

[0081] As described above, according to this embodiment, when the vehicle's driving state is transitioned from turning to straight driving, the left and right driving motors 50L, 50R are synchronously controlled such that the rotational speed of the outside driving motor 50 in the turning direction is kept constant without acceleration until the rotational speed of the inside driving motor 50 in the turning direction reaches the rotational speed of the outside driving motor 50 in the turning direction, and the acceleration of the inside driving motor 50 in the turning direction is changed to an acceleration (acceleration D, E) greater than the basic acceleration (acceleration A, B, C). This shortens the time until the rotational speeds of the left and right driving motors 50L, 50R are synchronized, and the vehicle can start driving straight at a timing that matches the operator's operating intention (this prevents a situation in which the vehicle continues turning for a longer period of time than the operator expects), thereby improving the response to driving operations and achieving safe and excellent driving performance that matches the operator's operating intention without any sense of discomfort.

[0082] Furthermore, according to this embodiment, the rotational speeds of the left and right traveling motors 50L, 50R can be synchronized before they reach the target rotational speed, so that the rotational speeds of the left and right traveling motors 50L, 50R can reach the target rotational speed at the same timing. This effectively prevents the vehicle from swinging back and forth, which reduces driving stability (the worker being swayed from side to side as a result of this reaction), thereby ensuring work safety.

[0083] Furthermore, according to this embodiment, when the rotational speeds of the left and right driving motors 50L, 50R become synchronized when the vehicle's driving state transitions from cornering to straight-line driving, the acceleration of the left and right driving motors 50L, 50R is returned to the basic acceleration (normal accelerations A to C), thereby suppressing the acceleration (acceleration during straight-line driving) after the rotational speeds of the left and right driving motors 50L, 50R become synchronized, and it becomes possible to mitigate the impact when the left and right driving motors reach the target rotational speed and transition to steady driving (constant speed driving).

[0084] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the gist of the present invention.

[0085] In the above embodiment, the current driving mode is determined based on the target rotation speeds of the left and right traveling motors 50L, 50R, but this is not limited to the configuration. For example, the current driving mode may be determined based on the amount of operation of the travel operation lever 47 and the turning amount operation dial 48.

[0086] In the above embodiment, the previous driving mode was determined based on the rotation speed command values ​​of the left and right traveling motors 50L, 50R. However, this is not limited to the above configuration. For example, a rotation detector may be provided to detect the actual rotation speeds of the traveling motors 50L, 50R, and the previous driving mode may be determined based on the actual rotation speeds detected by this rotation detector.

[0087] In the above embodiment, when the left and right synchronous control is completed, the left and right traveling motors 50L, Although the acceleration of 50R is changed from accelerations D, E to accelerations A, B, C, this is not limited to this configuration, and when left and right synchronization control is completed, the accelerations of the left and right traveling motors 50L, 50R may be maintained at accelerations D, E.

[0088] In the above embodiment, induction motors (AC motors) are used as the left and right travel motors 50L, 50R, but the invention is not limited to this configuration, and other travel motors such as DC motors or hydraulic motors may also be used.

[0089] In addition, in the above embodiment, a configuration including the travel operation lever 47 and the turning amount operation dial 48 was exemplified as the travel operation device, but for example, a travel operation device including an accelerator pedal that sets the travel speed and a handle that sets the turning direction and turning amount, or a joystick-type travel operation device that can set forward, reverse, travel speed, turning direction and turning amount with a single travel operation lever may also be applied.

[0090] In addition, in the above embodiment, a high-altitude work vehicle having a mast 20 and a work platform 30 on the running body 10 has been described, but the present invention can also be applied to a high-altitude work vehicle having a boom or a scissor-link type high-altitude work device on the running body, or a work vehicle having a crane device or the like on the running body. [Explanation of symbols]

[0091] 1. Aerial work vehicle (work vehicle) 10 Running body 11 Running frame (body) 12L left side crawler running device 12R Right side crawler running device 47 Travel control lever (travel control device) 48 Turn amount control dial (travel control device) 50L Left side travel motor 50R Right side travel motor 51L Left-hand drive inverter 51R Right-side drive inverter 60 Controller 60a Mast operation control unit 60b Driving control unit 61 Rotational speed calculation unit 62 Driving mode determination unit 63 Synchronization judgment unit 64 Acceleration determination section 65 Storage section

Claims

1. The car body and a left crawler traveling device and a right crawler traveling device provided on the left and right sides of the vehicle body; a left travel motor and a right travel motor for driving the left crawler travel device and the right crawler travel device, respectively; a travel operation device for operating the left crawler traveling device and the right crawler traveling device; and a travel control unit that controls drive of the left crawler travel device and the right crawler travel device by controlling a rotation direction and a rotation speed of the left travel motor and the right travel motor in response to an operation of the travel operation device, the travel control unit has a travel state determination unit that determines a travel state of the work vehicle, and an acceleration determination unit that sets accelerations of the left side travel motor and the right side travel motor during acceleration / deceleration of the work vehicle to a predetermined basic acceleration, When the driving state of the work vehicle is transitioned from turning driving to straight-ahead driving, the driving control unit synchronizes the left side driving motor and the right side driving motor by setting the acceleration of the other driving motor to zero to maintain the rotational speed of the other driving motor constant until the rotational speed of one of the left side driving motor and the right side driving motor, which is on the inside of the turning direction, reaches the rotational speed of the other driving motor, which is on the outside of the turning direction, and by setting the acceleration of the one driving motor to an acceleration greater than the basic acceleration.

2. 2. The travel control device for a work vehicle according to claim 1, characterized in that, when the rotational speed of the one travel motor reaches the rotational speed of the other travel motor during the synchronous control, the acceleration of the one and the other travel motors is set to the basic acceleration until the rotational speeds of the one and the other travel motors reach a predetermined target rotational speed.

3. The basic acceleration includes a first basic acceleration that is set when the work vehicle starts traveling, a second basic acceleration that is set when the work vehicle stops traveling, and a third basic acceleration that is set when the work vehicle is accelerating or decelerating while traveling (excluding the start of traveling and the stop of traveling), 3. The driving control device for a work vehicle as described in claim 1 or 2, characterized in that, when the driving state of the work vehicle is transitioned from pivot turning driving or gentle turning driving to straight driving, the driving control unit sets the acceleration of the one of the driving motors to an acceleration greater than the third basic acceleration until the rotational speed of the one of the driving motors reaches the rotational speed of the other of the driving motors.

4. The travel control device for a work vehicle as described in claim 3, characterized in that, when the travel state of the work vehicle is transitioned from spin turning travel to straight travel, the travel control unit sets the acceleration of the one of the travel motors to an acceleration greater than the second basic acceleration until the rotational speed of the one of the travel motors reaches zero, and sets the acceleration of the one of the travel motors to an acceleration greater than the first basic acceleration after the rotational speed of the one of the travel motors reaches zero until it reaches the rotational speed of the other of the travel motors.

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