Transport vehicle

Abstract

To provide a transport vehicle that can travel at a stable speed. [Solution] The differential control unit 53a in the transport vehicle 1 calculates a differential control value Cd by multiplying the differential value of the input differential velocity ΔV by the differential gain Kd. Here, the differential value of the differential velocity ΔV represents the amount of change of the differential velocity ΔV per unit time. The differential control value Cd calculated based on such a differential value of the differential velocity ΔV can be set to a value that suppresses large changes in the differential velocity ΔV and suppresses repeated large increases and decreases in the differential velocity ΔV, i.e., the actual speed Vr. By operating the engine 13, hydraulic pump 14 and hydraulic motor 10 using a rotation command Cr based on such differential control value Cd, repeated large increases and decreases in the actual speed Vr can be suppressed, so the transport vehicle 1 can travel at a stable speed.

Description

Technical Field

[0001] The present invention relates to a transport vehicle, particularly to a transport vehicle capable of traveling at a stable speed.

Background Art

[0002] Patent Document 1 discloses a vehicle that includes an engine 9, a hydraulic pump 36 driven by the engine 9 to supply pressurized oil, and a hydraulic motor 38 rotated by the pressurized oil supplied from the hydraulic pump 36, and travels by driving wheels 2 and 4 to rotate via the hydraulic motor 38. In this vehicle, an operator operates an accelerator pedal 8C to change the rotational speed of the engine 9, or change the tilt displacement of the hydraulic pump 36 or the hydraulic motor 38, so as to perform speed control of the vehicle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] In recent years, automation of vehicle speed control has been desired to achieve labor saving in vehicle operation. Accordingly, the applicant of the present application has attempted to automate speed control by controlling the rotational speed of the engine 9 and the tilt displacement of the hydraulic pump 36 or the hydraulic motor 38 through proportional control in which a predetermined coefficient is multiplied by a differential speed that is the difference between a reference speed which is the target traveling speed of the vehicle and an actual speed which is the actual traveling speed of the vehicle (non-public).

[0005] However, with such a method, it is impossible to suppress the situation where the actual speed repeatedly increases and decreases significantly even when the reference speed is constant, so there is a problem that the vehicle cannot travel at a stable speed.

[0006] This invention was made to solve the above-mentioned problems and aims to provide a transport vehicle that can travel at a stable speed. [Means for solving the problem]

[0007] To achieve this objective, the present invention provides a transport vehicle comprising wheels, an engine, a hydraulic pump driven by the engine and supplied with pressurized oil, and a hydraulic motor that rotates using the pressurized oil supplied from the hydraulic pump, and which moves by rotating the wheels with the hydraulic motor, and includes a reference speed acquisition means for acquiring a reference speed which is the target travel speed of the transport vehicle, an actual speed acquisition means for acquiring the actual travel speed which is the actual travel speed of the transport vehicle, a difference speed calculation means for calculating a difference speed which is the difference between the reference speed acquired by the reference speed acquisition means and the actual speed acquired by the actual speed acquisition means, a differential value calculation means for calculating a differential value which is the derivative of the difference speed calculated by the difference speed calculation means, a control value calculation means for calculating a control value that controls the rotation speed of the engine based on the differential value calculated by the differential value calculation means, and a control value output means for reflecting the control value calculated by the control value calculation means to the engine. The system includes a motor tilt maximization means that maximizes the tilt of the hydraulic motor when the reference speed acquired by the reference speed acquisition means is the second speed or lower and the actual speed acquired by the actual speed acquisition means is the third speed or lower, and a hydraulic pump tilt instruction means that controls the tilt of the hydraulic pump to a tilt based on the control value calculated by the control value calculation means. It is equipped with. [Effects of the Invention]

[0008] According to the transport vehicle described in claim 1, the difference in speed between the target travel speed of the transport vehicle (reference speed) and the actual speed is calculated, and the derivative of this difference in speed is calculated. Based on the calculated derivative, a control value is calculated to control the engine speed and is reflected in the engine. Here, the derivative of the difference in speed represents the amount of change of the difference in speed per unit time. By reflecting such a derivative of the difference in speed in the control value, the control value can be made a value that suppresses large changes in the difference in speed, i.e., changes in the difference in speed, i.e., the actual speed. As a result, the actual speed can be suppressed from repeatedly increasing and decreasing significantly, so the transport vehicle can maintain a stable speed. in It has the effect of making it possible to drive. Furthermore, when the reference speed is below the second speed and the actual speed is below the third speed, the tilt of the hydraulic motor is maximized, and the tilt of the hydraulic pump is adjusted to a control value. In other words, when the transport vehicle moves at a low speed to stop, the tilt of the hydraulic motor is maximized and the tilt of the hydraulic pump is adjusted to a control value, allowing the rotation of the hydraulic motor to be controlled more precisely by the engine. This also has the effect of enabling more accurate positioning when the transport vehicle stops at a predetermined location.

[0009] According to the transport vehicle described in claim 2, in addition to the effects of the transport vehicle described in claim 1, a feedforward value based on the reference speed is calculated, and a control value is calculated based on the differential value and the feedforward value. The feedforward value reflected in the control value allows the actual speed to approximate the reference speed early, and the differential value reflected in the control value suppresses repeated large increases and decreases in the actual speed. As a result, the transport vehicle can travel at a stable speed while keeping its actual speed closer to the reference speed.

[0010] According to the vehicle described in claim 3, in addition to the effects achieved by the transport vehicle described in claim 2, a step-wave-like travel speed is obtained as the reference speed, where the travel speed continues for a certain period of time. This step-wave-like reference speed is corrected so that the rising edge gradually increases and the falling edge gradually decreases, and a feedforward value is calculated based on the corrected reference speed. As a result, sudden acceleration and deceleration of the transport vehicle are suppressed, and the transport vehicle can travel at a stable speed.

[0011] According to the transport vehicle described in claim 4, in addition to the effects achieved by the transport vehicle described in claim 2, a proportional value based on the differential speed is calculated, and a control value is calculated based on the differential value, the feedforward value, and the proportional value. Since the proportional value is a value based on the differential speed, i.e., the difference between the reference speed and the actual speed, it can be a value that eliminates the difference between the reference speed and the actual speed. Therefore, the actual speed is approximated to the reference speed early by the proportional value, the difference between the reference speed and the actual speed is eliminated by the proportional value, and the repeated large increases and decreases in the actual speed are suppressed by the differential value, so that the transport vehicle can travel at a more stable speed.

[0012] According to the transport vehicle described in claim 5, in addition to the effects achieved by the transport vehicle described in any of claims 2 to 4, if the magnitude of the differential speed is less than or equal to the first speed, the control value is calculated using the derivative value, and if the magnitude of the differential speed is greater than the first speed, the derivative value is excluded from the calculation of the control value. As a result, when a transport vehicle with a differential speed of less than or equal to the first speed is traveling at a speed close to the reference speed, the repeated large increases and decreases in the actual speed due to the derivative value are suppressed, so that the transport vehicle can travel at a more stable speed.

[0013] On the other hand, if the magnitude of the differential velocity is greater than that of the first velocity, the differential value is excluded from the calculation of the control value. This prevents the differential value from interfering with the approximation of the actual velocity to the reference velocity using the feedforward value, which has the effect of allowing the actual velocity to be approximated to the reference velocity earlier when the difference between the reference velocity and the actual velocity is large.

[0014]

[0015] Claim 6 According to the described transport vehicle, in addition to the effects achieved by the transport vehicle described in any of claims 1 to 4, the control value is corrected according to the load on the loading platform. As a result, the time required for the actual speed to reach the reference speed can be kept constant regardless of the load on the loading platform, thereby suppressing delays caused by the transport vehicle's movement and enabling efficient operation of the transport vehicle.

[0016] Claim 7 According to the described transport vehicle, in addition to the effects achieved by the transport vehicle described in any of claims 1 to 4, a rotation command specifying the engine speed is calculated as a control value, and this rotation command is converted into a tilt command specifying the tilt of the hydraulic pump. The calculated engine rotation command is then applied to the engine, and the tilt command, which is the result of the rotation command conversion, is applied to the hydraulic pump.

[0017] That is, since the tilt command changes in conjunction with the change in the rotation command, the change in the engine speed and the change in the supply amount of pressure oil by the hydraulic pump are linked. As a result, the change in the engine speed is directly reflected by the change in the rotation of the hydraulic motor rotated by the hydraulic pump, so there is an effect that the speed control of the transport vehicle can be performed with higher accuracy. [Brief Description of the Drawings]

[0018] [Figure 1] It is a side view of the transport vehicle of the present invention. [Figure 2] It is a block diagram showing the electrical configuration of the transport vehicle. [Figure 3] It is a block diagram for explaining speed control of the transport vehicle. [Figure 4] (a) is a diagram for explaining a reference speed, (b) is a diagram for explaining a corrected reference speed, and (c) is a diagram for explaining the engine speed for making the actual speed equal to the reference speed for each reference speed and each load on the cargo bed. [Figure 5] It is a flowchart of main processing. [Figure 6] (a) is a flowchart of change processing, and (b) is a flowchart of control value calculation processing. [Figure 7] It is a diagram showing the transition of the reference speed and the actual speed. [Modes for Carrying Out the Invention]

[0019] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. First, the transport vehicle 1 will be described with reference to FIG. 1. FIG. 1 is a side view of the transport vehicle 1. The left side, right side, near side of the paper surface, and far side of the paper surface in FIG. 1 are defined as the front, rear, left, and right of the vehicle, respectively. In the present embodiment, the same numbers are used for the reference numerals of the corresponding configurations on the vehicle front side and the vehicle rear side, F is appended to the configuration on the vehicle front side, and B is appended to the configuration on the vehicle rear side, and part of the description is omitted. In addition, the same numbers are used for the reference numerals of the corresponding configurations on the left side and the right side of the vehicle, L is appended to the configuration on the left side of the vehicle, R is appended to the configuration on the right side of the vehicle, and part of the description is omitted.

[0020] The transport vehicle 1 is a hydraulically driven vehicle used to transport heavy loads such as steel materials within the premises of a factory or other facility. The transport vehicle 1 is equipped with a loading platform 2 on which the load is placed, a running gear 3 positioned below the loading platform 2 to move the transport vehicle 1, and control room units 4F and 4B located at the front and rear of the loading platform 2, respectively.

[0021] The running gear 3 supports the cargo bed 2 so that it can move via wheels 6 through link members 5. A steering device, which is a hydraulic device, rotates the link members 5 around a steering shaft 8 that extends vertically to change the direction of the wheels 6, and a lifting device 9, which is a hydraulic cylinder, changes the distance between the cargo bed 2 and the wheels 6 to raise or lower the cargo bed 2.

[0022] The running gear 3 is provided in two rows in the left-right direction of the vehicle and six rows in the front-rear direction of the vehicle. The running gears 3L1 to 3L6 are arranged from the front of the left row, and the running gears 3R1 to 3R6 are arranged from the front of the right row, and the wheels 6 of running gears 3L1 to 3L6 and 3R1 to 3R6 are designated as wheels 6L1 to 6L6 and 6R1 to 6R6, respectively.

[0023] The travel devices 3L2, 3R2, 3L5, and 3R5 drive the transport vehicle 1 by rotating the wheels 6L2, 6R2, 6L5, and 6R5, respectively, using hydraulic motors 10FL, 10FR, 10BL, and 10BR. Hereafter, unless otherwise specified, the hydraulic motors 10FL, 10FR, 10BL, and 10BR will be referred to as "hydraulic motor 10". The hydraulic motor 10 is rotated by pressurized oil supplied from a hydraulic pump 14, which will be described later. In this process, the amount of pressurized oil discharged is adjusted steplessly by controlling the tilt, thereby controlling the rotation of the hydraulic motor 10.

[0024] Control room units 4F and 4B are each equipped with control rooms 11F and 11B, respectively, which house control devices such as the CPU 20 described later. On the rear side (travel device 3 side) of control rooms 11F and 11B, although not shown in the figures, there is an engine 13, which is a diesel engine, and a hydraulic pump 14. The hydraulic pump 14 is operated by the engine 13 and is capable of discharging pressurized oil in one direction with a rotational driving force in one direction. By controlling the tilt, the amount of pressurized oil discharged can be adjusted steplessly.

[0025] When the transport vehicle 1 obtains a reference speed Vf from a speed output unit 50 (see Figure 2), which mainly consists of accelerator pedals (not shown) located in control rooms 11F and 11B, it controls the engine 13, hydraulic pump 14, and hydraulic motor 10 of the travel device 3 so that the actual travel speed Vr becomes the obtained reference speed Vf. Here, the reference speed Vf is the target travel speed of the transport vehicle 1.

[0026] Next, the electrical configuration of the transport vehicle 1 will be explained with reference to Figure 2. Figure 2 is a block diagram showing the electrical configuration of the transport vehicle 1. The transport vehicle 1 has a CPU 20, a flash ROM 21, and a RAM 23, which are connected to input / output ports 25 via a bus line 24. The input / output ports 25 are connected to the aforementioned traveling device 3, engine 13, and hydraulic pump 14, as well as a speed sensor 26 that detects the actual speed Vr of the transport vehicle 1 and a load sensor 27 that detects the load on the loading platform 2. Although multiple traveling devices 3 are installed on the transport vehicle 1, they are shown as a single unit in Figure 2.

[0027] The CPU 20 is an arithmetic unit that controls the various parts connected to the bus line 24 and input / output port 25. The flash ROM 21 is a rewritable, non-volatile memory that stores the control program 21a and coefficient data 21b. When the control program 21a is executed by the CPU 20, the main process shown in Figure 5 is executed.

[0028] The coefficient data 21b stores the following parameters used for speed control of the transport vehicle 1: acceleration α, deceleration β, first FF coefficient P1, second FF coefficient P2, differential gain Kd, difference gain Kp, and proportional gain K, each distinct for each load on the loading platform 2. Details of these parameters will be described later in Figure 3. Note that "FF" in the first FF coefficient P1 and second FF coefficient P2 is an abbreviation for "feedforward," and all subsequent use of "FF" will also refer to "feedforward."

[0029] RAM23 is memory used by the CPU20 to store various work data, flags, etc., in a rewritable format when executing control programs such as control program 21a.

[0030] Next, the speed control of the transport vehicle 1 will be explained with reference to Figures 3 and 4. Figure 3 is a block diagram illustrating the speed control of the transport vehicle 1. The speed control of the transport vehicle 1 is provided with a speed output unit 50, a feedforward control unit 52 (hereinafter abbreviated as "FF control unit 52"), a proportional-differential control unit 53 (hereinafter abbreviated as "PD control unit 53"), a proportional-differential control unit 54, and a conversion unit 55. The speed output unit 50 is a module that acquires the reference speed Vf, and is processed by the accelerator pedal and CPU 20 described above. In the following, "PD" is an abbreviation for "proportional-differential".

[0031] The FF control unit 52, PD control unit 53, and proportional difference control unit 54 are modules that calculate a rotation command Cr (control value) that specifies the rotational speed of the engine 13 in order for the transport vehicle 1 to travel at the reference speed Vf, based on the reference speed Vf input from the speed output unit 50 and the actual speed Vr input from the speed sensor 26.

[0032] First, the FF control unit 52 will be explained. The FF control unit 52 is a module that calculates a feedforward control value Cf (hereinafter abbreviated as "FF control value Cf") based on the input reference speed Vf, and is processed by the CPU 20 described above. The FF control unit 52 calculates the FF control value Cf in order to reflect the reference speed Vf in the rotation command Cr. The FF control unit 52 is provided with a reference speed correction unit 52a that corrects the input reference speed Vf.

[0033] The reference speed correction unit 52a is a module that calculates a corrected reference speed Vfa by correcting the input reference speed Vf based on acceleration α and deceleration β. The reference speed Vf and corrected reference speed Vfa will be explained here with reference to Figures 4(a) and (b).

[0034] Figure 4(a) is a diagram illustrating the reference speed Vf. In Figure 4(a), the horizontal axis represents time, and the vertical axis represents the travel speed. The same applies to Figures 4(b) and 7, which will be described later. The reference speed Vf acquired by the speed output unit 50 is exemplified by a case where its time progression is in the shape of a "step waveform". Specifically, in Figure 4(a), at time T1, the reference speed Vf changes from 0 to V1 (rising point), and then at the following time T2, the reference speed Vf changes from V1 to 0 (falling point).

[0035] If such a reference speed Vf is used directly to calculate the rotation command Cr for the engine 13, the transport vehicle 1 will accelerate or decelerate rapidly. Such driving would cause the load on the cargo bed 2 to move on the cargo bed 2 due to the law of inertia, and in some cases, the load may even fall from the cargo bed 2, making it impossible for the transport vehicle 1 to travel stably and potentially compromising the safety of the area around the transport vehicle 1. Therefore, in this embodiment, the stepped waveform reference speed Vf is corrected using acceleration α and deceleration β to suppress rapid acceleration or deceleration of the transport vehicle 1.

[0036] Figure 4(b) is a diagram illustrating the corrected reference speed Vfa. The reference speed correction unit 52a corrects the input step waveform reference speed Vf so that it gradually accelerates with acceleration α and gradually decelerates with deceleration β. Specifically, when the rising edge of the reference speed Vf is detected at time T1, a corrected reference speed Vfa is calculated such that the speed V1 becomes the speed V1 with acceleration α from the speed before acceleration (i.e., 0 km / h).

[0037] Similarly, if a falling edge of the reference speed Vf is detected at time T2, a corrected reference speed Vfa is calculated so that the speed before deceleration (i.e., V1) becomes 0 km / h due to the deceleration β.

[0038] The acceleration α and deceleration β are set based on the results of a prior simulation of the transport vehicle 1's movement, and are stored in the coefficient data 21b described above in Figure 2. In this embodiment, the corrected reference speed Vfa is accelerated linearly (a linear function) by the acceleration α, and decelerated linearly (a linear function) by the deceleration β. Note that the relationship between the acceleration and deceleration of the corrected reference speed Vfa is not limited to linear, but may be nonlinear, such as a quadratic function, cubic function, exponential function, or trigonometric function.

[0039] In this way, the corrected reference speed Vfa is corrected to gradually accelerate and decelerate the acquired reference speed Vf. As a result, sudden acceleration and deceleration of the transport vehicle 1 are suppressed, and the transport vehicle 1 can travel at a stable speed.

[0040] Returning to Figure 3, the corrected reference speed Vfa calculated by the reference speed correction unit 52a is multiplied by the first FF coefficient P1, and the second FF coefficient P2 is added to the resulting multiplied value to calculate the FF control value Cf. The first FF coefficient P1 and the second FF coefficient P2 are also coefficients that have been set in advance based on the results of a simulation of the transport vehicle 1's movement, and are stored in the coefficient data 21b described above in Figure 2.

[0041] Next, the PD control unit 53 and the proportional difference control unit 54 will be described. The PD control unit 53 and the proportional difference control unit 54 calculate a control value for correcting the FF control value Cf (i.e., the rotation command to the engine 13) calculated by the FF control unit 52, and a control value is calculated to suppress the increase in the difference speed ΔV between the reference speed Vf and the actual speed Vr. In this embodiment, if the absolute value (magnitude) of the difference speed ΔV is 2 km / h (first speed) or less, the control value is calculated by the PD control unit 53 and the proportional difference control unit 54, and if the absolute value of the difference speed ΔV is greater than 2 km / h, the control value is calculated by the proportional difference control unit 54 only.

[0042] In the PD control unit 53 and the proportional difference control unit 54, the difference speed ΔV, which is the difference between the reference speed Vf and the actual speed Vr, is used. First, the difference speed ΔV is calculated by subtracting the reference speed Vf input from the speed output unit 50 by the actual speed Vr input from the speed sensor 26.

[0043] The PD control unit 53 will now be described. The PD control unit 53 is a module that calculates a PD control value Cpd based on the derivative and proportional values ​​of the input differential velocity ΔV, and is processed by the CPU 20 described above. The PD control unit 53 is provided with a derivative control unit 53a and a proportional control unit 53b.

[0044] The differential control unit 53a is a module that calculates a differential control value Cd based on the change in differential velocity ΔV (hereinafter abbreviated as "differential"). Specifically, in the differential control unit 53a, the differential control value Cd is calculated by multiplying the value obtained by subtracting the previously input differential velocity ΔV from the input differential velocity ΔV (i.e., the differential value) by the differential gain Kd. The differential gain Kd is also a gain set in advance based on the results of a simulation of the transport vehicle 1's movement, and is stored in the coefficient data 21b described above in Figure 2.

[0045] Here, the derivative of the differential velocity ΔV represents the rate of change of the differential velocity ΔV per unit time (i.e., acceleration or deceleration). The differential control unit 53a calculates a differential control value Cd based on this derivative of the differential velocity ΔV, thereby setting the differential control value Cd to a value that suppresses large changes in the differential velocity ΔV (i.e., reduces acceleration or deceleration) and suppresses repeated large increases and decreases in the differential velocity ΔV, i.e., the actual velocity Vr. By operating the engine 13, hydraulic pump 14, and hydraulic motor 10 using a rotation command Cr based on such a differential control value Cd, repeated large increases and decreases in the actual velocity Vr can be suppressed, allowing the transport vehicle 1 to travel at a stable speed.

[0046] The proportional control unit 53b is a module that calculates a proportional control value Cp based on the differential speed ΔV. Specifically, in the proportional control unit 53b, the value obtained by multiplying the input differential speed ΔV by the differential gain Kp is calculated as the proportional control value Cp. The differential gain Kp is also a gain set in advance based on the results of a simulation of the transport vehicle 1's movement, and is stored in the coefficient data 21b described above in Figure 2. By operating the engine 13, hydraulic pump 14, and hydraulic motor 10 using the rotation command Cr based on the calculated proportional control value Cp, the difference between the differential speed ΔV, i.e., the reference speed Vf and the actual speed Vr, can be eliminated early.

[0047] The differential control value Cd and the proportional control value Cp, calculated by the differential control unit 53a and the proportional control unit 53b, are added together and integrated to calculate the PD control value Cpd.

[0048] Next, the proportional difference control unit 54 will be described. The proportional difference control unit 54 is a module that calculates a proportional difference control value Ce based on the difference velocity ΔV and the proportional difference velocity Dv, and is processed by the CPU 20. Specifically, the proportional difference control unit 54 calculates the proportional difference control value Ce by multiplying the value obtained by subtracting the proportional difference velocity Dv from the difference velocity ΔV by the proportional gain K.

[0049] In this embodiment, "2 km / h" is given as an example of the proportional differential speed Dv, but other values ​​may be set. The proportional gain K is a gain set based on the results of a simulation of the transport vehicle 1's movement in advance, and is stored in the coefficient data 21b shown in Figure 2.

[0050] The proportional difference control value Ce calculated by the proportional difference control unit 54 is based on the difference speed ΔV, which is the difference between the reference speed Vf and the actual speed Vr, minus the proportional difference speed Dv. Therefore, the difference between the reference speed Vf and the actual speed Vr is eliminated, and the proportional difference control value Ce can be prevented from becoming excessively large. This prevents the transport vehicle 1 from accelerating or decelerating suddenly.

[0051] Then, based on the sum of the FF control value Cf calculated by the FF control unit 52, the PD control value Cpd calculated by the PD control unit 53, and the proportional difference control value Ce calculated by the proportional difference control unit 54, a rotation command Cr to be reflected in the engine 13 is calculated. When calculating the rotation command Cr, predetermined coefficients may be added, subtracted, multiplied, or divided as needed. The calculated rotation command Cr for the engine 13 is then input to the engine 13, and the engine 13 operates to the rotation speed specified by the input rotation command Cr.

[0052] The rotation of the engine 13 drives the hydraulic pump 14, which supplies pressurized oil to the hydraulic motor 10. At this time, the tilt command Cq, which is output to the hydraulic pump 14 and specifies the tilt of the hydraulic pump 14, is set by the conversion unit 55 based on the rotation command Cr reflected in the engine 13. Specifically, the conversion unit 55 is a module that converts the rotation command Cr to the tilt command Cq, and is processed by the CPU 20.

[0053] In the conversion unit 55, for example, the rotation command Cr, which sets the rotational speed of the engine 13 to 800-2000 rpm, and the tilt command Cq, which sets the tilt of the hydraulic pump 14 to 45-100%, are scaled to a one-to-one correspondence. However, this scaling is not limited to a one-to-one correspondence between the rotation command Cr and the tilt command Cq; for example, the relationship between the rotation command Cr and the tilt command Cq may be weighted and then scaled.

[0054] In this way, the conversion unit 55 calculates the tilt command Cq based on the rotation command Cr, so that the tilt command Cq changes in conjunction with the change in the rotation command Cr. As a result, the change in the rotational speed of the engine 13 and the change in the amount of pressurized oil supplied by the hydraulic pump 14 are linked, so that the change in the rotational speed of the engine 13 is directly reflected in the change in the rotation of the hydraulic motor 10 rotated by the hydraulic pump 14, and the speed control of the transport vehicle 1 can be performed with greater precision.

[0055] Pressurized oil from the hydraulic pump 14 is supplied to the hydraulic motors 10 of each travel device 3, causing the hydraulic motors 10 to rotate. Here, when it is confirmed that the differential speed ΔV is 1.0 km / h (second speed) or less and the actual speed Vr is 1.2 km / h (third speed) or less, the hydraulic motor 10 is given a maximum motor tilt command Ps, which is a command to maximize the tilt. That is, when the transport vehicle 1 is traveling at a low speed to stop, with a reference speed Vf of 1.0 km / h or less and an actual speed Vr of 1.2 km / h or less, the tilt of the hydraulic motor 10 is maximized. By maximizing the tilt of the hydraulic motor 10, the rotation of the hydraulic motor 10 can be precisely controlled by the engine 13 or the hydraulic pump 14. This allows for accurate positioning when the transport vehicle 1 stops.

[0056] As described above, the rotation command Cr and tilt command Cq for controlling the travel speed of the transport vehicle 1 are calculated based on the FF control value Cf calculated by the FF control unit 52, the PD control value Cpd calculated by the PD control unit 53, and the proportional difference control value Ce calculated by the proportional difference control unit 54.

[0057] Of these, the FF control value Cf is calculated based on the reference speed Vf, and is therefore a value that approximates the actual speed Vr to the reference speed Vf as early as possible. Also, the proportional difference control value Ce is a value based on the difference speed ΔV, and is therefore a value that resolves the difference between the difference speed ΔV, i.e., the actual speed Vr, and the reference speed Vf as early as possible. As mentioned above, the differential control value Cd in the PD control value Cpd is a value that suppresses repeated large increases and decreases in the actual speed Vr.

[0058] Based on the FF control value Cf, PD control value Cpd, and proportional difference control value Ce, the rotation command Cr and tilt command Cq are calculated, allowing the transport vehicle 1 to travel at a stable speed while keeping its actual speed Vr in line with the reference speed Vf.

[0059] By the way, the ground pressure on the wheels 6 changes depending on the load of the cargo loaded on the cargo bed 2. In other words, even if the reference speed Vf is the same, the rotational speed of the engine 13 required to bring the actual speed Vr to that reference speed Vf will differ depending on the ground pressure on the wheels 6 (= load of the cargo = mass of the cargo).

[0060] Figure 4(c) is a diagram illustrating the rotational speed of the engine 13 required to bring the actual speed Vr to the reference speed Vf for each reference speed Vf and load on the cargo bed 2. In Figure 4(c), the relationship between the reference speed Vf and the rotational speed of the engine 13 when the load on the cargo bed 2 is 75 tons is shown by a solid line, the relationship between the reference speed Vf and the rotational speed of the engine 13 when the load on the cargo bed 2 is 35 tons is shown by a dashed line, and the relationship between the reference speed Vf and the rotational speed of the engine 13 when the load on the cargo bed 2 is 0 tons (empty) is shown by a dashed line.

[0061] As shown in Figure 4(c), the rotational speed of the engine 13 required to bring the actual speed Vr to the reference speed Vf is higher the larger the load on the cargo bed 2, even if the reference speed Vf is the same. Therefore, in this embodiment, for each load on the cargo bed 2, the acceleration α, deceleration β, first FF coefficient P1, second FF coefficient P2, differential gain Kd, difference gain Kp, and proportional gain K are calculated and stored in the coefficient data 21b.

[0062] Specifically, parameters such as acceleration α, which are used to calculate the rotation command Cr that increases the engine speed 13 as the load on the cargo bed 2 increases, are stored in the coefficient data 21b. In this embodiment, the parameters such as acceleration α are set based on the results of a simulation of the transport vehicle 1's movement when the load on the cargo bed 2 is changed in increments of 1 ton or the like.

[0063] For example, if the load on cargo bed 2 is 0 tons, the acceleration α will be "0.4 m / s²". 2 ”, deceleration β is “0.2m / s 2 The first FF coefficient P1 is set to "920", the second FF coefficient P2 to "82.5", the differential gain Kd to "43", the difference gain Kp to "15", and the proportional gain K to "45".

[0064] Furthermore, if the load on cargo bed 2 is 20 tons, the acceleration α will be "0.35 m / s²". 2 ", deceleration β is "0.1 m / s 2 The first FF coefficient P1 is set to "1096", the second FF coefficient P2 to "82.5", the differential gain Kd to "160", the difference gain Kp to "15", and the proportional gain K to "50".

[0065] Then, acceleration α, deceleration β, first FF coefficient P1, second FF coefficient P2, differential gain Kd, difference gain Kp, and proportional gain K corresponding to the load sensor 27 (see Figure 2) are obtained from coefficient data 21b and used to calculate the rotation command Cr and tilt command Cq. In other words, appropriate rotation command Cr and tilt command Cq are calculated based on the load on the loading platform 2. As a result, the time required for the actual speed Vr to reach the reference speed Vf can be kept constant regardless of the load on the loading platform 2 (=mass of the load), so that delays in the transport vehicle 1 are suppressed and the transport vehicle 1 can be operated efficiently.

[0066] Next, we will explain the processes executed by the CPU 20 with reference to Figures 5 and 6. Figure 5 is a flowchart of the main process. The main process is executed after the power is turned on to the transport vehicle 1. The main process first checks whether the reference speed Vf has been acquired by the speed output unit 50 described above (S1).

[0067] If it is confirmed in the process of S1 that the reference speed Vf has been obtained (S1: Yes), the load on the loading platform 2 is obtained from the load sensor 27 (S2). After the process of S2, the acceleration α, deceleration β, first FF coefficient P1, second FF coefficient P2, differential gain Kd, difference gain Kp, and proportional gain K corresponding to the obtained load are obtained from the coefficient data 21b (S3).

[0068] After processing in S3, the actual speed Vr is obtained from the speed sensor 26 (S4), and the differential speed ΔV is calculated by subtracting the actual speed Vr obtained in processing S4 from the reference speed Vf obtained in processing S1 (S5). After processing in S5, a modification process (S6) is executed, and then a control value calculation process (S7) is executed. The modification process and the control value calculation process will be explained with reference to Figure 6.

[0069] Figure 6(a) is a flowchart showing the modification process. The modification process involves changing parameter values ​​such as the first FF coefficient P1 and proportional gain K according to the magnitude of the actual speed Vr and differential speed ΔV, or changing the tilt command reflected in the hydraulic motor 10.

[0070] The modification process first checks if the differential velocity ΔV is 2 km / h or greater, i.e., greater than or equal to the proportional differential velocity Dv (S20). If the process in S20 confirms that the differential velocity ΔV is 2 km / h or greater (S20: Yes), the proportional gain K is set to "40" (S21). On the other hand, if the process in S20 confirms that the differential velocity ΔV is less than 2 km / h (S20: No), the proportional gain K is set to "0" (S22).

[0071] In other words, when the differential velocity ΔV is 2 km / h, i.e., greater than or equal to the proportional differential velocity Dv, the proportional gain K is set to "40". As a result, the proportional differential control value Ce is set to a value of 0 or greater in absolute value (magnitude), and the proportional differential control value Ce is included in the rotation command Cr and the tilt command Cq, so the difference between the actual velocity Vr and the reference velocity Vf can be eliminated early.

[0072] On the other hand, when the differential speed ΔV is less than 2 km / h, the proportional gain K is set to "0", which in turn sets the proportional differential control value Ce to 0. In other words, when the difference between the actual speed Vr and the reference speed Vf is small, the effect of the proportional differential control value Ce in resolving the difference between the actual speed Vr and the reference speed Vf is excluded, so that the actual speed Vr of the transport vehicle 1 stabilizes and the transport vehicle 1 can run smoothly.

[0073] In addition, in the S20 process, the speed at which the differential velocity ΔV is compared is not limited to 2 km / h; it may be greater than or equal to 2 km / h, or less than or equal to 2 km / h.

[0074] After processing S21 and S22, it is checked whether the reference speed Vf is 1.0 km / h (second speed) or less and the actual speed Vr is 1.2 km / h (third speed) or less (S23). If it is confirmed in processing S23 that the differential speed ΔV is 1.0 km / h or less and the actual speed Vr is 1.2 km / h or less (S23: Yes), the above motor maximum tilt command Ps is applied to the hydraulic motor 10 (S24). After processing S24, the first FF coefficient P1 is set to "900" and the second FF coefficient P2 is set to "300" (S25), the differential gain Kp is set to "15" and the differential gain Kd is set to "0" (S26).

[0075] Specifically, the maximum motor tilt command Ps is reflected in the hydraulic motor 10, and the first FF coefficient P1 is set to "900", the second FF coefficient P2 to "300", the differential gain Kp to "15", and the differential gain Kd to "0". Therefore, the rotation command Cr and tilt command Cq are calculated using the FF control value Cf, proportional control value Cp, and proportional-differential control value Ce, while the differential control value Cd is excluded.

[0076] As a result, interference between the differential control value Cd and the speed control based on the reference speed Vf and differential speed ΔV during low-speed travel when the transport vehicle 1 is stopped can be suppressed. This allows the actual speed Vr to be accurately approximated to the reference speed Vf, and the positioning of the transport vehicle 1 can be performed with high precision.

[0077] In the process of S23, if it is confirmed that the reference speed Vf is greater than 1.0 km / h, or that the actual speed Vr is greater than 1.2 km / h (S23: No), the processes of S24 to S26 are skipped. Note that in the process of S23, the speed for which the reference speed Vf is compared is not limited to 1.0 km / h, but may be greater than or equal to 1.0 km / h, or less than or equal to 1.0 km / h. Similarly, the speed for which the actual speed Vr is compared is not limited to 1.2 km / h, but may be greater than or equal to 1.2 km / h, or less than or equal to 1.2 km / h.

[0078] After processing S23 and S26, the modification process will be terminated.

[0079] Next, the control value calculation process will be explained with reference to Figure 6(b). Figure 6(b) is a flowchart of the control value calculation process. The control value calculation process is the process of calculating the FF control value Cf, the PD control value Cpd, and the proportional difference control value Ce.

[0080] The control value calculation process first calculates the FF control value Cf using the method described above in Figure 3, with the acquired reference velocity Vf, acceleration α, deceleration β, first FF coefficient P1, and second FF coefficient P2 (S40).

[0081] After processing in S40, it is checked whether the absolute value of the differential velocity ΔV is 2 km / h (first velocity) or less (S41). If it is confirmed in processing S41 that the absolute value of the differential velocity ΔV is 2 km / h or less (S41: Yes), the PD control value Cpd is calculated using the differential velocity ΔV, the differential gain Kd, and the differential gain Kp, using the method described above in Figure 3 (S42). On the other hand, if it is confirmed that the absolute value of the differential velocity ΔV is greater than 2 km / h (S41: No), the PD control value Cpd is set to 0 (S43).

[0082] When the transport vehicle 1 is traveling at a speed close to the reference speed Vf, such that the absolute value (i.e., magnitude) of the differential speed ΔV is 2 km / h (first speed) or less, the calculation of the rotation command Cr and tilt command Cq includes the PD control value Cpd, especially the differential control value Cd. This suppresses repeated large increases and decreases in the actual speed Vr, allowing the transport vehicle 1 to travel at a stable speed.

[0083] On the other hand, when the absolute value of the differential velocity ΔV is greater than 2 km / h, the PD control value Cpd is excluded from the calculation of the rotation command Cr and the tilt command Cq. As a result, the PD control value Cpd, especially the differential control value Cd, no longer interferes with the approximation of the actual velocity Vr to the reference velocity Vf using the FF control value Cf, or with the resolution of the difference between the reference velocity Vf and the actual velocity Vr using the proportional differential control value Ce. This allows the actual velocity Vr to be approximated to the reference velocity Vf earlier. Note that in the processing of S41, the speed at which the absolute value of the differential velocity ΔV is compared is not limited to 2 km / h; it may be greater than or equal to 2 km / h, or less than or equal to 2 km / h.

[0084] After processing in S42 and S43, the proportional difference control value Ce is calculated using the differential velocity ΔV, the proportional difference velocity Dv, and the proportional gain K, according to the method described in Figure 3 (S44), and the control value calculation process is terminated.

[0085] Return to Figure 6. After the control value calculation process in S7, the rotation command Cr is calculated using the method described above in Figure 3, using the calculated FF control value Cf, PD control value Cpd, and proportional difference control value Ce (S8), and this rotation command Cr is output to the engine 13 (S9). After the process in S9, the rotation command Cr calculated in the process in S8 is converted into a tilt command Cq using the method described above in Figure 3 (S10), and this tilt command Cq is output to the hydraulic pump 14 (S11).

[0086] If it is confirmed during the S1 process that the reference speed Vf has not been obtained (S1: No), then the S2 to S11 processes are skipped. After the S1 and S11 processes, other processes for the transport vehicle 1 are executed (S12), and the processes from S1 onwards are repeated.

[0087] Finally, with reference to Figure 7, we will explain the reference speed Vf and the actual speed Vr based on that reference speed Vf. Figure 7 is a diagram showing the changes in reference speed Vf and actual speed Vr. First, at time Ta after the start of travel, the reference speed Vf is 8 km / h, and this travel speed continues until time Tc.

[0088] During the period from time Ta to Tb, the absolute value of the differential velocity ΔV is greater than 2 km / h, so the PD control value Cpd is excluded from the calculation of the rotation command Cr and tilt command Cq by the processing in S41 and S43 in Figure 6(b). This suppresses interference between the PD control value Cpd, especially the differential control value Cd, and the speed control using the reference velocity Vf and the differential velocity ΔV. In this case, the FF control value Cf uses a corrected reference velocity Vfa, in which the reference velocity Vf is corrected by the acceleration α, resulting in a gentler acceleration between time Ta and Tb, and the transport vehicle 1 accelerates smoothly.

[0089] During the subsequent period from time Tb to Tc, the reference speed Vf remains at 8 km / h, and the absolute value of the differential speed ΔV is 2 km / h or less. Therefore, the PD control value Cpd is used to calculate the rotation command Cr and tilt command Cq through the processing in S41 and S42 of Figure 6(b). As a result, the repeated large increases and decreases in the actual speed Vr are suppressed by the PD control value Cpd, particularly the differential control value Cd.

[0090] At the subsequent time Tc, the reference speed Vf is reduced from 8 km / h to 4 km / h. As a result, the absolute value of the differential speed ΔV becomes greater than 2 km / h again, so the PD control value is excluded from the calculation of the rotation command Cr and the tilt command Cq. Furthermore, since the differential speed ΔV becomes -2 km / h or less, the proportional differential control value Ce is also excluded from the calculation of the rotation command Cr and the tilt command Cq.

[0091] Therefore, between times Tc and Td, the rotation command Cr and tilt command Cq are calculated solely by the FF control value Cf. In this case, the FF control value Cf uses a corrected reference speed Vfa, which is obtained by correcting the reference speed Vf with the deceleration β. This results in a gradual deceleration between times Tc and Td, allowing the transport vehicle 1 to decelerate smoothly.

[0092] Between the following times Td and Te, the reference speed Vf is further reduced to 3 km / h, and then accelerated to 4 km / h. During this period, as between times Tb and Tc, the PD control values ​​are used to calculate the rotation command Cr and tilt command Cq, thereby suppressing repeated large increases and decreases in the actual speed Vr.

[0093] At time Te, the reference speed Vf is reduced from 4 km / h to 2 km / h. In the period from time Te to Tf thereafter, the rotation command Cr and tilt command Cq are calculated using only the FF control value Cf, similar to the period from time Tc to Td. Furthermore, the deceleration β makes the reduction between time Te and Tf more gradual, so the transport vehicle 1 is decelerated smoothly.

[0094] During the subsequent time interval Tf to Tg, the PD control values ​​are also used to calculate the rotation command Cr and tilt command Cq, similar to the interval Tb to Tc, thereby suppressing repeated large increases and decreases in the actual speed Vr.

[0095] Furthermore, at time Tg, the reference speed Vf is reduced from 2 km / h to 1 km / h. As a result, the actual speed Vr is reduced to 1.2 km / h or less. Consequently, the process from S23 to S26 in Figure 6(a) maximizes the tilt of the hydraulic motor 10, and the differential control value Cd is excluded from the calculation of the rotation command Cr and the tilt command Cq. These measures enable the positioning of the transport vehicle 1, which is performed just before the transport vehicle 1 stops, to be performed with high accuracy.

[0096] Although the present invention has been described above based on embodiments, it can be easily inferred that the present invention is not limited in any way to the embodiments described above, and that various improvements and modifications are possible without departing from the spirit of the present invention.

[0097] In the above embodiment, the rotation command Cr was calculated using the FF control value Cf, the PD control value Cpd, and the proportional difference control value Ce, but it is not limited to this. For example, in calculating the rotation command Cr, the PD control value Cpd and the proportional difference control value Ce may be used while the FF control value Cf is excluded from the calculation of the rotation command Cr, or the FF control value Cf and the PD control value Cpd may be used while the proportional difference control value Ce is excluded from the calculation of the rotation command Cr. Furthermore, in calculating the rotation command Cr, the PD control value Cpd may be used while the FF control value Cf and the proportional difference control value Ce are excluded from the calculation of the rotation command Cr.

[0098] Furthermore, while the rotation command Cr was calculated by adding the FF control value Cf, the PD control value Cpd, and the proportional difference control value Ce, this is not the only method. For example, the rotation command Cr may be calculated by multiplying the FF control value Cf, the PD control value Cpd, and the proportional difference control value Ce, or by multiplying the sum of the FF control value Cf and the PD control value Cpd by the proportional difference control value Ce. Moreover, the rotation command Cr may be calculated after weighting the FF control value Cf, the PD control value Cpd, and the proportional difference control value Ce by multiplying each of them by a coefficient. However, in this embodiment, these control values ​​are defined so that the rotation command Cr is calculated by adding the FF control value Cf, the PD control value Cpd, and the proportional difference control value Ce. Therefore, if the rotation command Cr is calculated using a method other than adding these control values, these control values ​​must also be defined accordingly.

[0099] In the above embodiment, the PD control value Cpd was calculated by adding the differential control value Cd and the proportional control value Cp, but this is not the only method. In calculating the PD control value Cpd, the proportional control value Cp may be excluded, and the PD control value Cpd may be calculated using only the differential control value Cd. Alternatively, the PD control value Cpd may be calculated by multiplying the differential control value Cd and the proportional control value Cp, or by dividing the differential control value Cd by the proportional control value Cp. Furthermore, the PD control value Cpd may be calculated after weighting the differential control value Cd and the proportional control value Cp, such as by multiplying each of them by a coefficient. However, in this embodiment, these control values ​​are defined so that the PD control value Cpd is calculated by adding the differential control value Cd and the proportional control value Cp. Therefore, if the PD control value Cpd is calculated using a method other than adding these control values, these control values ​​must also be defined accordingly.

[0100] In the above embodiment, the reference speed correction unit 52a of the FF control unit 52 (Figure 3) corrects the step-shaped reference speed Vf input to gradually accelerate with acceleration α and gradually decelerate with deceleration β, but it is not limited to this. For example, the reference speed correction unit 52a may correct the rising edge of the reference speed Vf with acceleration α while omitting the correction of the falling edge of the reference speed Vf, or it may correct the falling edge of the reference speed Vf with deceleration β while omitting the correction of the rising edge of the reference speed Vf. Alternatively, the correction of the reference speed Vf itself may be omitted by omitting the reference speed correction unit 52a from the FF control unit 52. However, in this case, as described above, there is a concern that the transport vehicle 1 may suddenly start or decelerate, so it is desirable to ensure safety in some way.

[0101] In the above embodiment, the PD control value Cpd was set to 0 or the sum of the differential control value Cd and the proportional control value Cp depending on the magnitude of the differential velocity ΔV (Figure 6(b), S41-S43), but it is not limited to this. For example, the PD control value Cpd may be set to the sum of the differential control value Cd and the proportional control value Cp regardless of the magnitude of the differential velocity ΔV. Alternatively, the PD control value Cpd may be set to 0 or the sum of the differential control value Cd and the proportional control value Cp depending on other velocities or physical quantities such as the actual velocity Vr.

[0102] In the above embodiment, the proportional gain K was set to 40 when the magnitude of the differential velocity ΔV was 2 km / h or more, and to 0 when the magnitude of the differential velocity ΔV was less than 2 km / h (Figure 6(a), S20~S22), but it is not limited to this. For example, in addition to the above, the proportional gain K may be set to "45" when the magnitude of the differential velocity ΔV is 2.5 km / h or more, and to "50" when the magnitude of the differential velocity ΔV is 3 km / h or more, and so on, with the proportional gain K set according to multiple stages of the magnitude of the differential velocity ΔV. Alternatively, the proportional gain K may be set to 40 regardless of the magnitude of the differential velocity ΔV. The proportional gain K may be set to a value other than the above-mentioned "0", "40", "45", or "50" (a fixed value), or the proportional gain K may be set according to other velocities or physical quantities such as the actual velocity Vr, or the proportional gain K may be set by a separate method.

[0103] In the above embodiment, acceleration α, deceleration β, first FF coefficient P1, second FF coefficient P2, differential gain Kd, difference gain Kp, and proportional gain K were varied according to the magnitude of the load on the cargo bed 2 (Figure 5, S2, S3), but this is not limited to this. Acceleration α, deceleration β, first FF coefficient P1, second FF coefficient P2, differential gain Kd, difference gain Kp, and proportional gain K may be fixed values ​​regardless of the magnitude of the load on the cargo bed 2.

[0104] Alternatively, some of these parameters (e.g., acceleration α, deceleration β, first FF coefficient P1, and second FF coefficient P2) may be varied according to the magnitude of the load on the cargo bed 2, while the remaining parameters (e.g., differential gain Kd, difference gain Kp, and proportional gain K) may be kept fixed regardless of the magnitude of the load on the cargo bed 2.

[0105] In the above embodiment, the speed output unit 50 that acquires the reference speed Vf is configured as an accelerator pedal, but it is not limited to this. For example, the speed output unit 50 may be configured to store in advance the progression of the reference speed Vf required for the transport vehicle 1 to reach its destination in the flash ROM 21, and acquire the reference speed Vf from the flash ROM 21 as appropriate. In this case, in calculating the corrected reference speed Vfa in Figure 4(b), the time required for the speed to go from 0 to V1 from the current position by acceleration α may be calculated, and acceleration may be started from a timing calculated backward from the time calculated from time T1. Similarly, the time required for the speed to go from V1 to 0 from the current position by deceleration β may be calculated, and deceleration may be started from a timing calculated backward from the time calculated from time T2.

[0106] Furthermore, although the above embodiment exemplified a step waveform as the reference speed Vf, it is not limited to this, and other shapes are also possible, such as when the rising or falling edge of the reference speed Vf is a quadratic function, a cubic function, an exponential function, or a trigonometric function.

[0107] In the above embodiment, the hydraulic pressure of the pressurized oil supplied from the hydraulic pump 14 is excluded from the parameters for the sake of simplifying the control, but this is not the only option. For example, the hydraulic pressure may be added to the parameters when determining the tilt command Cq in the conversion unit 55, or the hydraulic pressure may be added to the parameters when calculating the PD control value Cpd in the PD control unit 53 or the proportional difference control value Ce in the proportional difference control unit 54.

[0108] In the above embodiment, the tilt control of the hydraulic motor 10 was omitted in the modification process shown in Figure 6(a) when it was confirmed that the reference speed Vf was greater than 1.0 km / h or the actual speed Vr was greater than 1.2 km / h (S23: No). However, the embodiment is not limited to this, and in such cases, tilt control of the hydraulic motor 10 may be performed according to, for example, the actual speed Vr or the reference speed Vf.

[0109] In the above embodiment, a transport vehicle 1 driven by a hydraulic motor 10 was illustrated, but the present invention is not limited to this, and for example, the present invention may be applied to a transport vehicle driven by an electric motor. In this case, the calculated rotation command Cr can be converted to a value corresponding to the electric motor, and then that rotation command Cr can be used to control the electric motor.

[0110] In the above embodiment, the invention was described using a transport vehicle 1, but it is not necessarily limited to this, and for example, the present invention may be applied to other vehicles such as automated guided vehicles (AGVs), unit carriers, and automobiles. When the present invention is configured as an AGV, the transition of the reference speed Vf required for the AGV to reach its destination may be stored in advance in flash ROM or the like, and the reference speed Vf may be obtained from the flash ROM or the like as appropriate. In this case as well, in the calculation of the corrected reference speed Vfa in Figure 4(b), the time required for the speed to go from 0 to V1 from the current position by acceleration α may be calculated, and acceleration may be started from a timing calculated backward from the time calculated from time T1. Similarly, the time required for the speed to go from V1 to 0 from the current position by deceleration β may be calculated, and deceleration may be started from a timing calculated backward from the time calculated from time T2. [Explanation of symbols]

[0111] 1. Transport vehicle 2. Cargo bed 6 wheels 10 Hydraulic motor 13 Engine 14. Hydraulic pump 26 Speed ​​sensor (part of the means for acquiring actual speed) 27. Load sensor (part of load acquisition means) Cd Differential control value (derivative value) Ce Proportional difference control value (proportional value) Cf Feedforward control value (feedforward value) Cq Tilt command Cr rotation command (control value) Vf reference speed VR actual speed ΔV differential velocity S1 Reference speed acquisition means S2 Part of the load acquisition method S4 Part of the method for obtaining actual speed S5 Differential speed calculation means S8 Control value calculation means S9 Control value output means S10 Conversion means , part of the hydraulic pump tilting instruction means S11 Part of a hydraulic pump tilting instruction mechanism S23, S24 Motor tilt maximization means S40 Feedforward value calculation means, reference speed correction means S42 Differential value calculation means S44 Proportional value calculation means

Claims

1. A transport vehicle comprising wheels, an engine, a hydraulic pump driven by the engine and supplied with pressurized oil, and a hydraulic motor rotated by the pressurized oil supplied from the hydraulic pump, wherein the vehicle moves by rotating the wheels with the hydraulic motor, A reference speed acquisition means for acquiring a reference speed which is the target travel speed of the transport vehicle, A means for acquiring the actual speed, which is the actual travel speed of the transport vehicle, A differential speed calculation means calculates the differential speed, which is the difference between the reference speed obtained by the reference speed acquisition means and the actual speed obtained by the actual speed acquisition means. A differential value calculation means for calculating a differential value which is the derivative of the differential velocity calculated by the differential velocity calculation means, A control value calculation means calculates a control value for controlling the rotational speed of the engine based on the differential value calculated by the differential value calculation means, A transport vehicle characterized by comprising a control value output means for reflecting the control value calculated by the control value calculation means to the engine.

2. The system includes a feedforward value calculation means that calculates a feedforward value which is a value based on the reference speed acquired by the reference speed acquisition means, The transport vehicle according to claim 1, characterized in that the control value calculation means calculates a control value based on the differential value calculated by the differential value calculation means and the feedforward value calculated by the feedforward value calculation means.

3. The aforementioned reference speed acquisition means acquires the aforementioned travel speed as a reference speed in the form of a step waveform, where the same travel speed continues for a certain period of time. The system includes a reference speed correction means that corrects the step waveform reference speed acquired by the reference speed acquisition means by gradually increasing the rising edge and gradually decreasing the falling edge of the travel speed, The transport vehicle according to claim 2, characterized in that the feedforward value calculation means calculates the feedforward value based on the reference speed corrected by the reference speed correction means.

4. The system includes a proportional value calculation means for calculating a proportional value which is a value based on the differential velocity calculated by the differential velocity calculation means, The transport vehicle according to claim 2, characterized in that the control value calculation means calculates a control value based on the differential value calculated by the differential value calculation means, the feedforward value calculated by the feedforward value calculation means, and the proportional value calculated by the proportional value calculation means.

5. If the magnitude of the differential velocity calculated by the differential velocity calculation means is less than or equal to the first velocity, the control value calculation means calculates a control value using the differential value calculated by the differential value calculation means. The transport vehicle according to any one of claims 2 to 4, characterized in that if the magnitude of the differential speed is greater than the first speed, the differential value is excluded from the calculation of the control value.

6. A transport vehicle according to any one of claims 1 to 4, characterized in that it is equipped with a motor tilt maximization means that maximizes the tilt of the hydraulic motor when the reference speed acquired by the reference speed acquisition means is the second speed or lower and the actual speed acquired by the actual speed acquisition means is the third speed or lower.

7. A cargo bed for loading cargo, It is equipped with a load acquisition means for acquiring the load on the cargo bed, The control value calculation means further comprises a control value correction means that corrects the control value according to the load acquired by the load acquisition means. The transport vehicle according to any one of claims 1 to 4, characterized in that the control value output means reflects the control value corrected by the control value correction means to the engine.

8. The control value calculation means calculates a rotation command that specifies the rotation speed of the engine as the control value, The system includes a conversion means that converts the rotation command into a tilt command specifying the tilt of the hydraulic pump, The transport vehicle according to any one of claims 1 to 4, characterized in that the control value output means reflects the calculated rotation command to the engine and reflects the tilt command converted from the rotation command to the hydraulic pump.

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