A hydraulic system for an AGV drive component and its control method

Abstract

The present invention belongs to the technical field of unmanned transport vehicles, and specifically relates to a hydraulic system for an AGV drive assembly and a control method thereof. By providing a third reversing valve for a hydraulic cylinder that can conduct or disconnect at least two hydraulic devices, the controller can selectively control the opening and closing of each third reversing valve according to the actual driving conditions and load conditions, so that the interconnected hydraulic devices are combined into a connected suspension, and the non-conducting hydraulic devices remain independent, dynamically adapting to the road conditions. Therefore, the hydraulic system provided by the present invention can actively switch the suspension mode, enabling the AGV to better adapt to road conditions and load conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of automated guided vehicles (AGVs), and particularly relates to a hydraulic system for an AGV drive assembly and a control method thereof. Background Art

[0002] An AGV refers to an automated guided vehicle, which carries the weight of goods by itself through the AGV vehicle body and is mostly used in fields such as assembly and logistics. Existing AGVs usually include a vehicle frame and a plurality of drive units provided at the bottom of the vehicle frame. Each drive unit is respectively provided with a hydraulic device for supporting the vehicle frame. During the driving process of the AGV, the hydraulic device adaptively adjusts the pressure value according to the road surface and load conditions. However, the current hydraulic control method is relatively single, and the hydraulic cylinders of each hydraulic device cannot be actively connected or disconnected, that is, it is impossible to actively switch between the connection suspension mode, the independent suspension mode, and the coexistence mode of connection suspension and independent suspension. Therefore, there are strict restrictions on the weight coverage range of the load and the position of the center of gravity. Otherwise, it will damage the vehicle frame and even cause the AGV to roll over. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiency of the single suspension mode of the existing AGV drive assembly hydraulic system, and provide a hydraulic system that can change the suspension mode by switching the connection relationship between each hydraulic cylinder.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A hydraulic system for an AGV drive assembly, the drive assembly involved includes a plurality of drive units provided at the bottom of the AGV vehicle frame. The hydraulic system includes a plurality of hydraulic devices respectively provided between each drive unit and the AGV vehicle frame, and a controller communicatively connected to each hydraulic device.

[0006] The hydraulic device includes a directional valve assembly, an accumulator, a second directional valve, and a hydraulic cylinder. The directional valve assembly is provided with an oil supply port P, an oil return port T, and an interface A. The oil supply port P and the oil return port T are respectively connected to a power station. The interface A is connected to the cylinder body of the hydraulic cylinder through an oil circuit X. The piston rod of the hydraulic cylinder is connected to the drive unit. The oil inlet of the second directional valve is connected to the interface A. The accumulator is connected to the oil outlet of the second directional valve. A third directional valve is connected between at least two hydraulic devices. The hydraulic cylinders of the at least two hydraulic devices can be controllably conducted with each other when the third directional valve is opened or disconnected when the third directional valve is closed. The second directional valves of the at least two hydraulic devices can be controllably disconnected from the accumulators of the at least two hydraulic devices when the third directional valve is opened and conduct the accumulators of the at least two hydraulic devices when the third directional valve is closed.

[0007] Compared with the prior art, the hydraulic system provided by the present invention is provided with a third reversing valve for a hydraulic cylinder that can conduct or disconnect at least two hydraulic devices between at least two hydraulic devices. Therefore, the controller can selectively control the opening and closing of each third reversing valve according to the actual driving conditions and load conditions, so that the mutually conducting hydraulic devices are combined into a connection suspension, and the non-conducting hydraulic devices remain independent. For example, when the load is unloaded or light, some adjacent hydraulic devices are selectively connected, and the accumulators of these hydraulic devices are closed, so as to realize dynamic compensation between the oil circuits of these hydraulic devices to dynamically adapt to the road conditions. And when the AGV has a heavy load, a partial load, or is about to enter a section with poor road conditions such as a depression, each third reversing valve is closed, and the accumulators of each hydraulic device are opened to absorb pressure by the accumulators, so that the oil circuits of each hydraulic device are kept independent to realize an independent suspension mode. Therefore, the hydraulic system provided by the present invention can actively switch the suspension mode, so that the AGV can better adapt to the road conditions and load conditions.

[0008] Further, the third reversing valve is provided between every two adjacent hydraulic devices, and two oil ports of the third reversing valve are respectively connected to the oil circuit X of the corresponding hydraulic device through oil pipes.

[0009] Further, it further includes a sensor that is communicatively connected to the controller and is used to detect the oil pressure data of the hydraulic cylinders of each hydraulic device.

[0010] Further, the accumulator is a gas-type accumulator.

[0011] Further, the reversing valve assembly includes a valve body, a first reversing valve, a pilot-operated check valve, and an overflow valve respectively connected to the valve body. The valve body is provided with the oil supply port P, the oil return port T, and the interface A; the first reversing valve is a three-position four-way electromagnetic reversing valve, the second reversing valve and the third reversing valve are electric two-position two-way reversing valves, and the first reversing valve, the second reversing valve, and the third reversing valve are respectively communicatively connected to the controller.

[0012] The present invention also provides a control method applied to the above hydraulic system, and the controller stores the following control strategies:

[0013] Preset strategy;

[0014] Strategy ①: The controller closes all the third reversing valves, opens the second reversing valve to conduct the accumulator and the hydraulic cylinder of the corresponding hydraulic device, and reduces the driving speed of the AGV.

[0015] Strategy ②: The controller selectively opens the corresponding third reversing valve to form a connection suspension between several interconnected hydraulic devices, and closes the second reversing valve of each hydraulic device in the connection suspension to close the accumulator, so that the interconnected hydraulic cylinders can obtain mutual feedback pressure compensation during walking.

[0016] The control method includes the following steps:

[0017] Step 1: Detect the load condition of the AGV. When there is a load, obtain the center of gravity position of the load on the AGV frame.

[0018] Step 2: Select the corresponding control strategy:

[0019] (1) When the AGV is unloaded, execute the preset strategy;

[0020] (2) When the load weight of the AGV is within the first weight range, execute Strategy ②, and make the center of gravity position of the load located between the equivalent support points of several connected suspensions, or within the support surface enclosed by the equivalent support points of several connected suspensions and the support points of several independent hydraulic devices;

[0021] (3) When the load weight of the AGV is within the second weight range, execute Strategy ①, where the weight of the first weight range is less than the weight of the second weight range.

[0022] The above equivalent support point refers to the midpoint of the plane or straight line formed by the projection of each interconnected hydraulic device on the AGV frame, and the support point of the independent hydraulic device refers to the central position of the hydraulic device.

[0023] When executing Strategy ②, adjust the interconnected hydraulic devices according to the dynamic situation of the piston rod stroke data of the hydraulic cylinders of each hydraulic device and the load distribution situation to re-form the connection suspension, so as to cope with the preset walking path and the specified load to be carried.

[0024] When the length of the AGV frame exceeds the preset length threshold, or the center of gravity position of the load is located in the offloading area of the frame, or the AGV is about to enter a concave section, Strategy ① is preferably selected.

[0025] Further, in order to reduce the computing load of the controller, the controller divides the frame of the AGV into a preset loading range and a non-preset loading range, and correspondingly sets a first control scheme group and a second control scheme group. Multiple control schemes for forming a support surface within the preset loading range are stored in the first control scheme group, and multiple control schemes for forming a support surface within the non-preset loading range are stored in the second control scheme group. When selecting Strategy ②, if the load center of gravity is located within the preset loading range, control schemes are sequentially selected from the first control scheme until the support surface of the selected control scheme covers the center of gravity of the load. If the load center of gravity is located within the non-preset loading range, control schemes are sequentially selected from the second control scheme until the support surface of the selected control scheme covers the center of gravity of the load, or when the support surfaces formed by all the control schemes in the second control scheme group cannot cover the center of gravity of the load, an alarm signal is issued.

[0026] Further, the controller obtains the load condition of the AGV by analyzing the difference between the real-time pressure value of the hydraulic cylinder of each hydraulic device and its initial pressure value; and sets the preset strategy according to the initial pressure value. Obtaining the initial pressure value includes the following steps of initial value setting before performing Step 1:

[0027] Place the AGV on a horizontal plane and make it unloaded, and perform initialization processing on the data; make the hydraulic cylinders of each hydraulic device return oil by switching the state of the first reversing valve, and lower each hydraulic cylinder to the lowest position; close the third reversing valve to make each hydraulic device maintain an independent state; close the accumulator of each hydraulic device; make the hydraulic cylinders of each hydraulic device enter oil by switching the state of the first reversing valve, and raise each hydraulic cylinder to a preset initial height; obtain the pressure value of each hydraulic cylinder at this time and store it as the corresponding initial pressure value.

[0028] Further, for the initial value setting step, the actual lifting height and the initial pressure value of the hydraulic cylinder of each hydraulic device are respectively compared with their corresponding standard values, and it is analyzed whether the deviation value is within a reasonable range. If it exceeds the reasonable range, an alarm signal is issued.

[0029] Further, when detecting the load condition of the AGV, if the real-time pressure value of the hydraulic cylinder of each hydraulic device exceeds the safety threshold, an alarm signal is issued, thereby further ensuring the reliability of the AGV operation.

[0030] Further, in order to further improve the reliability of the control method, it also includes a self-check step before detecting the load condition of the AGV:

[0031] When the AGV receives a running command, it makes the hydraulic cylinders of each hydraulic device return oil by switching the state of the first reversing valve, causing each hydraulic cylinder to descend to the lowest position; closes the third reversing valve to keep each hydraulic device in an independent state; closes the accumulators of each hydraulic device; makes the hydraulic cylinders of each hydraulic device intake oil by switching the state of the first reversing valve, causing each hydraulic cylinder to rise to a preset height; determines whether the actions and dynamic pressure values during the rising process of the hydraulic cylinder are normal. If normal, it determines the load condition of the AGV, otherwise it issues an alarm signal.

[0032] The control method provided by the present invention can selectively change the suspension mode according to the load and road conditions. Thus, when the AGV is unloaded or the load is within a preset range, some hydraulic devices are connected to achieve connected suspension. Through the connection between the hydraulic cylinders in the connected suspension, dynamic compensation is achieved, and it is ensured that the center of gravity position of the load is always within the support surface formed by the support points of the suspension, improving the driving stability of the AGV and reducing the probability of rollover. And when the load is overweight, the center of gravity position is in the offloading area of the AGV frame, that is, when serious offloading occurs, or when the AGV is about to enter a concave road section, all the third reversing valves are closed to achieve the independent suspension mode, and at the same time, the vehicle speed is reduced and the pressure is dynamically absorbed by the accumulators of each hydraulic device. Since the accumulator can only adapt to a certain range of pressure, when the pressure exceeds the range, the buffering effect of the accumulator will be greatly reduced. Therefore, it is necessary to reduce the vehicle speed and drive slowly. At the same time, since when the independent suspension mode is adopted, the number of support points increases, and at this time the frame is in an over-positioning state, the impact introduced by the drive unit during fast walking will have a greater negative impact on the AGV frame. Therefore, it is necessary to reduce the vehicle speed. However, by conducting the hydraulic device through the third reversing valve, the support points can be simplified and the number of support points can be reduced. Therefore, the AGV can travel quickly. Therefore, the hydraulic system control method provided by the present invention can adaptively adopt corresponding control strategies according to the actual situation to cope with different driving situations. Description of the Drawings

[0033] Figure 1 is a schematic structural diagram of the AGV;

[0034] Figure 2 is a schematic structural diagram of the hydraulic system;

[0035] Figure 3 is a schematic flow diagram of the hydraulic system control method;

[0036] Figure 4 is a schematic flow diagram of the initial value setting step;

[0037] Figure 5 is a schematic diagram of the independent suspension mode;

[0038] Figure 6 and Figure 7It is a schematic diagram of a connecting suspension. The dotted lines in the figure indicate that the corresponding hydraulic devices are interconnected.

[0039] Figure 8 and Figure 9 It is a schematic diagram of a composite suspension. The dotted lines in the figure indicate that the corresponding hydraulic devices are interconnected.

[0040] Figures 10 to 12 It is a schematic diagram of the suspension modes of the same AGV under different driving conditions. The dotted lines in the figure indicate that the corresponding hydraulic devices are interconnected. Specific Embodiments

[0041] The following describes the specific embodiments of the present invention with reference to the accompanying drawings. In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "front" and "rear" is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0042] Refer to Figure 1 and Figure 2 , this embodiment provides a hydraulic system for an AGV drive assembly. The drive assembly includes a plurality of drive units 2 provided at the bottom of the AGV frame 1. The hydraulic system includes a plurality of hydraulic devices 3 respectively provided between each drive unit 2 and the AGV frame 1, and a controller (not shown in the figure) communicatively connected to each hydraulic device 3.

[0043] Refer to Figure 2 , the hydraulic device 3 includes a power station 31, a directional valve assembly, an accumulator 35, a second directional valve 36, a hydraulic cylinder 37, and a filter assembly 38. The directional valve assembly includes a valve body, and a first directional valve 33, a pilot check valve 34, and a relief valve 41 connected to the valve body. The valve body is provided with an oil supply port P, an oil return port T, and an interface A. The oil supply port P is connected to the power station 31 through the filter assembly 38 and an oil pump 32, its oil return port T is connected to the power station 31, the interface A is connected to the cylinder body of the hydraulic cylinder 37 through an oil circuit X, the piston rod of the hydraulic cylinder 37 is connected to the drive unit 2, the inlet port of the second directional valve 36 is connected to the interface A, the accumulator 35 is connected to the outlet port of the second directional valve 36. A third directional valve 39 is connected between at least two hydraulic devices 3. The hydraulic cylinders 37 of the at least two hydraulic devices 3 can be controllably interconnected when the third directional valve 39 is opened or disconnected when the third directional valve 39 is closed. The second directional valves 36 of the at least two hydraulic devices 3 can be controllably disconnected from the accumulators 35 of the at least two hydraulic devices 3 when the third directional valve 39 is opened, and connect the accumulators 35 of the at least two hydraulic devices 3 when the third directional valve 39 is closed.

[0044] In another setting mode, different from the mode where each of the above hydraulic devices 3 is respectively provided with a power station 31, in this setting mode, in order to simplify the structure, a common power station 31 is shared among the hydraulic devices 3.

[0045] As a specific implementation manner, the third reversing valve 39 is provided between every two adjacent hydraulic devices 3, and two oil ports of the third reversing valve 39 are respectively connected to the oil circuit X of the corresponding hydraulic device 3 through oil pipes.

[0046] As a specific implementation manner, it further includes sensors that are communicatively connected to the controller and are used to detect the oil pressure data and the piston rod stroke of the hydraulic cylinders 37 of the hydraulic devices 3.

[0047] As a specific implementation manner, the accumulator 35 is a gas accumulator, such as a diaphragm accumulator.

[0048] In a specific implementation manner, the first reversing valve 33 is a three-position four-way electromagnetic reversing valve, the second reversing valve 36 and the third reversing valve 39 are mechanical two-position two-way reversing valves, and the first reversing valve 33, the second reversing valve 36 and the third reversing valve 39 are respectively communicatively connected to the controller.

[0049] Compared with the prior art, the hydraulic system provided by the present invention is provided with a third reversing valve 39 that can conduct or close the hydraulic cylinders 37 of at least two hydraulic devices 3 between at least two hydraulic devices 3. Therefore, the controller can selectively control the opening and closing of each third reversing valve 39 according to the actual driving conditions and load conditions, so that the mutually conductive hydraulic devices 3 are combined into a connection suspension, and the non-conductive hydraulic devices 3 remain independent. For example, when the load is light or unloaded, some adjacent hydraulic devices 3 are selectively connected, and the accumulators 35 of these hydraulic devices 3 are closed, so as to realize dynamic compensation between the oil circuits of these hydraulic devices 3 to dynamically adapt to the road conditions. And when the AGV has a heavy load, uneven load or is about to enter a section with poor road conditions such as a depression, each third reversing valve 39 is closed, and the accumulators 35 of each hydraulic device 3 are opened to absorb the pressure by the accumulators 35, so that the oil circuits of each hydraulic device 3 remain independent to realize the independent suspension mode. Therefore, the hydraulic system provided by the present invention can actively switch the suspension mode, so that the AGV can better adapt to the road conditions and load conditions.

[0050] As Figure 5 shown, in a specific implementation scenario of realizing the independent suspension mode, the AGV is provided with hydraulic devices numbered 1-6, and a third reversing valve is provided between every two adjacent hydraulic devices. When each third reversing valve is closed, the oil circuits of each hydraulic device remain independent, so as to realize the independent suspension mode.

[0051] As Figure 6As shown, in a specific implementation scenario of the connection suspension mode, the AGV is provided with hydraulic devices numbered 1-6, and a third reversing valve is provided between every two adjacent hydraulic devices. When the corresponding third reversing valves are respectively turned on between No. 1 and No. 3, between No. 2 and No. 4, and between No. 5 and No. 6, the turned-on hydraulic devices form a connection suspension.

[0052] As Figure 7 shown, in another specific implementation scenario of the connection suspension mode, the AGV is provided with hydraulic devices numbered 1-10. A third reversing valve is provided between every two adjacent hydraulic devices among No. 1, No. 3, and No. 5. A third reversing valve is provided between every two adjacent hydraulic devices among No. 2, No. 4, and No. 6. A third reversing valve is provided in the middle of hydraulic devices No. 7, No. 8, No. 9, and No. 10. When the corresponding hydraulic devices are turned on by the third reversing valve, the turned-on hydraulic devices form a connection suspension.

[0053] As Figure 8 shown, in a specific implementation scenario of a composite suspension mode that realizes both connection suspension and independent suspension, the AGV is provided with hydraulic devices numbered 1-6, and a third reversing valve is provided between every two adjacent hydraulic devices. When the third reversing valves between No. 1, No. 3, and No. 5 are turned on, the turned-on hydraulic devices form a connection suspension. The third reversing valve between No. 2 and No. 4 remains closed, and the third reversing valve between No. 4 and No. 6 is opened, so that No. 2 forms an independent suspension, and the combination of No. 4 and No. 6 forms a connection suspension.

[0054] See Figures 1 to 9 , This embodiment also provides a hydraulic control method applied to the above hydraulic system , the controller stores the following control strategies:

[0055] Preset strategy;

[0056] Strategy ①: The controller closes all the third reversing valves 39, opens the second reversing valve 36 to turn on the accumulator 35 and the hydraulic cylinder 37 of the corresponding hydraulic device 3, and reduces the traveling speed of the AGV; As Figure 5 shown, in a specific implementation scenario of the independent suspension mode, the AGV is provided with hydraulic devices numbered 1-6, and a third reversing valve is provided between every two adjacent hydraulic devices. When each third reversing valve is closed, the oil circuits of each hydraulic device remain independent, thus realizing the independent suspension mode.

[0057] Strategy ②: The controller selectively opens the corresponding third reversing valve 39 so that a connection suspension is formed between several mutually connected hydraulic devices 3, and closes the second reversing valve 36 of each hydraulic device 3 in the connection suspension to close the accumulator 35 so that the mutually connected hydraulic cylinders 37 can obtain mutual feedback pressure compensation during walking.

[0058] See Figure 2 and Figure 3 , the control method includes the following steps:

[0059] Step 01:

[0060] When the AGV receives a running command, for example, a command to receive a loading task, it first performs a self-check operation: by switching the state of the first reversing valve 33, the hydraulic cylinders 37 of each hydraulic device 3 achieve oil return, causing each hydraulic cylinder 37 to descend to the lowest position; closing the third reversing valve 39 keeps each hydraulic device 3 in an independent state, and closing the accumulators 35 of each hydraulic device 3; by switching the state of the first reversing valve 33, the hydraulic cylinders 37 of each hydraulic device 3 achieve oil inlet, causing each hydraulic cylinder 37 to rise to a preset height; determine whether the actions and dynamic pressure values during the rising process of the hydraulic cylinder 37 are normal. If normal, proceed to Step 02, otherwise, send an alarm signal.

[0061] Step 02: The controller detects the load condition of the AGV; when there is a load, obtain the center of gravity position of the load on the AGV frame 1. In a specific embodiment, the above method of obtaining the center of gravity position can be obtained by analyzing the real-time pressure values of the hydraulic cylinders 37 of each hydraulic device 3. The method of obtaining the center of gravity position is prior art and is not the technical problem to be solved by the present invention, so it will not be described in detail here.

[0062] As a specific embodiment, the controller obtains the load condition of the AGV by analyzing the difference between the real-time pressure value and the initial pressure value of the hydraulic cylinder 37 of each hydraulic device 3. For example, when the difference between the real-time pressure value and the initial pressure value of at least one hydraulic cylinder 37 of the hydraulic device 3 is within a preset range, it is determined that the AGV is loaded with a load, otherwise it is unloaded. When detecting the load condition of the AGV, if the real-time pressure values of the hydraulic cylinders 37 of each hydraulic device 3 exceed the safety threshold, an alarm signal is sent.

[0063] See Figure 3 and Figure 4 obtaining the initial pressure value includes an initial value setting step before performing Step 01:

[0064] Place the AGV on a horizontal plane and unloaded, perform initialization processing on the data; by switching the state of the first reversing valve 33, the hydraulic cylinders 37 of each hydraulic device 3 achieve oil return, causing each hydraulic cylinder 37 to descend to the lowest position; close the third reversing valve 39 to keep each hydraulic device 3 in an independent state; close the accumulators 35 of each hydraulic device 3; by switching the state of the first reversing valve 33, the hydraulic cylinders 37 of each hydraulic device 3 achieve oil inlet, causing each hydraulic cylinder 37 to rise to a preset initial height; obtain the pressure value of each hydraulic cylinder 37 at this time and store it as the corresponding initial pressure value.

[0065] In order to further improve the reliability of the hydraulic system control method, when performing the initial value setting step, the actual lifting height and the initial pressure value of each hydraulic cylinder 37 of the hydraulic device 3 are respectively compared with their corresponding standard values, and it is analyzed whether the deviation value is within a reasonable range. If it exceeds the reasonable range, an alarm signal is issued.

[0066] See Figures 1 to 3 , Step 03: Select the corresponding control strategy:

[0067] (1) When the AGV is unloaded, execute the preset strategy.

[0068] (2) When the load weight of the AGV is within the first weight range, execute Strategy ② to form a connection suspension between several mutually connected hydraulic devices 3, so that the center of gravity position of the load is located between the equivalent support points of several connection suspensions, or within the support surface enclosed by the equivalent support points of several connection suspensions and the support points of several independent hydraulic devices 3. The above equivalent support points refer to the midpoints of the planes or connecting lines formed by each hydraulic device 3 after mutual conduction on the projection of the AGV frame 1, and the support point of the independent hydraulic device 3 refers to the center position of the hydraulic device 3.

[0069] The following provides a specific implementation scenario of the suspension mode implemented when executing the above Strategy ②:

[0070] (1) Connection suspension mode:

[0071] As Figure 6 shown, in a specific implementation scenario of implementing the connection suspension mode, the AGV is provided with hydraulic devices numbered 1 - 6, and a third reversing valve is provided between each adjacent hydraulic device. When the 1st and 3rd, 2nd and 4th, and 5th and 6th are respectively conducted through the corresponding third reversing valves, the conducted hydraulic devices form a connection suspension, and the equivalent support points of the connection suspension are A, B, and C respectively, and the support points of each connection suspension form a triangular support surface.

[0072] As Figure 7 shown, in another specific implementation scenario of implementing the connection suspension mode, the AGV is provided with hydraulic devices numbered 1 - 10. A third reversing valve is provided between every two adjacent hydraulic devices among the 1st, 3rd, and 5th, a third reversing valve is provided between every two adjacent hydraulic devices among the 2nd, 4th, and 6th, and a third reversing valve is provided in the middle of the 7th, 8th, 9th, and 10th hydraulic devices 3. When the third reversing valve conducts the corresponding hydraulic devices, the conducted hydraulic devices form a connection suspension, and the equivalent support points of the connection suspension are A, B, and C respectively, and the support points of each connection suspension form a triangular support surface.

[0073] (2) Composite suspension mode:

[0074] AsFigure 8 As shown, in a specific implementation scenario of a composite suspension mode in which a connected suspension and an independent suspension coexist, the AGV is provided with hydraulic devices No. 1-6, and a third reversing valve is provided between each adjacent hydraulic device. When the third reversing valve between No. 1, No. 3, and No. 5 is turned on, the turned-on hydraulic devices constitute a connected suspension, the third reversing valve between No. 2 and No. 4 remains closed, and the third reversing valve between No. 4 and No. 6 is opened, so that No. 2 constitutes an independent suspension, and the combination of No. 4 and No. 6 constitutes a connected suspension, wherein the support point of the independent suspension is C, and the equivalent support points of the two connected suspensions are A and B, and each support point constitutes a triangular support surface.

[0075] like Figure 9 As shown, in a specific implementation scenario of a composite suspension mode in which connected suspension and independent suspension coexist, the AGV is provided with hydraulic devices No. 1-8, a third reversing valve is provided between each adjacent two hydraulic devices No. 1, No. 2, and No. 3, a third reversing valve is provided between No. 4 and No. 5, and a third reversing valve is provided between each adjacent two hydraulic devices No. 6, No. 7, and No. 8. When No. 1, No. 2, and No. 3 are connected to each other, a connected suspension is formed; when No. 6, No. 7, and No. 8 are connected to each other, a connected suspension is formed; No. 5 and No. 6 remain independent to form an independent suspension, and the supporting points A, B, C, and D corresponding to the above suspensions form a quadrilateral supporting surface.

[0076] (III) When the AGV load weight is within the second weight range, strategy ① is executed, wherein the weight within the first weight range is less than the weight of the second preset weight, that is, when the AGV load is heavier, strategy ① is executed.

[0077] For step 03, when executing strategy ②, the hydraulic devices to be connected are adjusted according to the dynamic situation of the piston rod stroke data of the hydraulic cylinders of each hydraulic device and the load distribution to reconstruct the connection suspension to cope with the preset walking path and carry the specified load.

[0078] The above-mentioned preset walking path is implemented as follows: when the AGV moves horizontally over the steps, the stroke of the piston rod of the hydraulic device corresponding to the drive unit on the steps changes greatly, but its pressure value remains basically unchanged. Therefore, during the driving process of the AGV, the dynamic stroke data of the piston rod is obtained. When the stroke of some piston rods is within the preset range, all hydraulic devices corresponding to the piston rod along the driving direction of the AGV are turned on, such as Figure 10 As shown in the figure, when the No. 3 and No. 4 drive units move onto the steps, the stroke of their piston rods will change, and the hydraulic devices of the two drive units will be turned on to change the original suspension mode during driving, such as Figure 11 As shown, when the AGV is about to leave the steps and enter the straight road, it switches to the original suspension mode.

[0079] The above-mentioned handling of the specified load is as follows in the following specific implementation scenarios, such as Figure 12 As shown, when the load appears in a discrete distribution in the offloading area of the vehicle frame, the hydraulic devices at the front end of the guiding vehicle frame in the driving direction, such as the No. 7 and No. 8 hydraulic devices in the figure, and the hydraulic devices on both sides in the middle, such as the No. 3 and No. 5, and No. 4 and No. 6 in the figure, form three groups of connecting suspensions, and keep the No. 1 and No. 2 hydraulic devices at the rear end of the vehicle frame in the driving direction independent, forming an independent suspension, so as to cope with the situation of multi-point offloading of the load.

[0080] When the length of the AGV vehicle frame exceeds the preset length threshold, or the center of gravity position of the load is in the offloading area of the vehicle frame 1, or the AGV is about to enter a concave road section, strategy ① is preferentially selected. The offloading area of the vehicle frame 1 is the position on the AGV vehicle frame 1 where the load is likely to cause the AGV to roll over, such as the edge position of the vehicle frame 1.

[0081] For the setting method of the preset strategy:

[0082] See Figure 4 , in a specific implementation manner of a preset strategy, the preset strategy is manually set according to the initial pressure value.

[0083] See Figure 2 , in another specific implementation manner of the preset strategy, the preset strategy reduces the support points on the AGV by connecting some of the hydraulic devices 3, avoiding the over-positioning state of the AGV, and thus can improve the driving speed of the AGV. Preferably, the preset strategy is specifically: the controller opens the corresponding third reversing valve 39 to make several mutually conducting hydraulic devices 3 form a connecting suspension, so that a triangular support surface as shown in Figure 6 or Figure 8 is enclosed between the equivalent support points of the connecting suspension, or between the equivalent support points of several connecting suspensions and the support points of several independent hydraulic devices 3, and closes the second reversing valve 36 of each hydraulic device 3 in the connecting suspension to close the accumulator 35. Or, as another specific setting method of the preset strategy, the controller opens all the third reversing valves 39 to make the hydraulic cylinders 37 of all the hydraulic devices 3 mutually conducting.

[0084] See Figure 3, in order to reduce the computing load of the controller, the controller divides the frame 1 of the AGV into a preset loading range and a non-preset loading range, and correspondingly sets a first control scheme group and a second control scheme group. A variety of control schemes for forming a support surface located within the preset loading range are stored in the first control scheme group, and a variety of control schemes for forming a support surface located within the non-preset loading range are stored in the second control scheme group. When selecting Strategy ②, if the load center of gravity position is within the preset loading range, control schemes are sequentially selected in the first control scheme until the support surface of the selected control scheme covers the center of gravity of the load. If the load center of gravity position is within the non-preset loading range, control schemes are sequentially selected in the second control scheme until the support surface of the selected control scheme covers the center of gravity position of the load, or when the support surfaces formed by all the control schemes in the second control scheme group cannot cover the center of gravity position of the load, an alarm signal is issued. This way of area division can improve the controller's judgment ability on whether it can perform the handling task.

[0085] The control method provided by the present invention can selectively change the suspension mode according to the load and road conditions, so as to connect certain hydraulic devices 3 to achieve connected suspension when the vehicle is unloaded or the load is within the preset range. Dynamic compensation is achieved through the connection between the hydraulic cylinders 37 in the connected suspension, and it is ensured that the center of gravity position of the load is always within the support surface formed by the support points of the suspension, improving the driving stability of the AGV and reducing the probability of rollover. And when the load is overweight, the center of gravity position is in the offloading area of the frame 1 of the AGV frame 1, that is, when the offloading is serious, or when the AGV is about to enter a concave road section, all the third reversing valves 39 are closed to achieve the independent suspension mode, and at the same time, the vehicle speed is reduced and the pressure is dynamically absorbed by the accumulators 35 of each hydraulic device 3. Since the accumulator 35 can only adapt to a certain range of pressure, when the pressure exceeds the range, the buffering effect of the accumulator 35 will be greatly reduced. Therefore, it is necessary to reduce the vehicle speed and drive slowly. At the same time, since when the independent suspension mode is adopted, the number of support points increases, and at this time the frame 1 is in an over-positioning state, the impact introduced by the drive unit 2 during fast walking will have a greater negative impact on the AGV frame 1. Therefore, it is necessary to reduce the vehicle speed. However, by conducting the hydraulic device 3 through the third reversing valve 39, the support points can be simplified and the number of support points can be reduced. Therefore, the AGV can drive quickly. Therefore, the hydraulic system control method provided by the present invention can adaptively adopt corresponding control strategies according to the actual situation to cope with different driving situations.

[0086] Based on the disclosure and teachings of the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A hydraulic system for an AGV drive assembly. The drive assembly involved includes a plurality of drive units provided at the bottom of the AGV frame. The hydraulic system includes a plurality of hydraulic devices respectively provided between each drive unit and the AGV frame, and a controller communicatively connected to each hydraulic device. It is characterized in that: The hydraulic device includes a directional valve assembly, an accumulator, a second directional valve, and a hydraulic cylinder. The directional valve assembly is provided with an oil supply port P, an oil return port T, and an interface A. The oil supply port P and the oil return port T are respectively connected to a power station. The interface A is connected to the cylinder block of the hydraulic cylinder through an oil circuit X. The piston rod of the hydraulic cylinder is connected to the drive unit. The oil inlet of the second directional valve is connected to the interface A. The accumulator is connected to the oil outlet of the second directional valve. A third directional valve is connected between at least two hydraulic devices. The hydraulic cylinders of the at least two hydraulic devices can be controllably conducted with each other when the third directional valve is opened or disconnected when the third directional valve is closed. The second directional valves of the at least two hydraulic devices can be controllably disconnected from the accumulators of the at least two hydraulic devices when the third directional valve is opened and conduct the accumulators of the at least two hydraulic devices when the third directional valve is closed; The directional valve assembly includes a valve body and a first directional valve, a pilot-operated check valve, and a relief valve respectively connected to the valve body. The valve body is provided with the oil supply port P, the oil return port T, and the interface A. The first directional valve is a three-position four-way electromagnetic directional valve. The second directional valve and the third directional valve are electric two-position two-way directional valves. The first directional valve, the second directional valve, and the third directional valve are respectively communicatively connected to the controller.

2. The hydraulic system according to claim 1, wherein, The third directional valve is provided between every two adjacent hydraulic devices. The two oil ports of the third directional valve are respectively connected to the oil circuit X of the corresponding hydraulic device through oil pipes.

3. The hydraulic system according to claim 1, wherein It further includes sensors communicatively connected to the controller and used for detecting the oil pressure data of the hydraulic cylinders of each hydraulic device and the stroke of the piston rod; And / or, the accumulator is a gas-type accumulator.

4. A control method applied to the hydraulic system according to any one of claims 1 to 3, characterized in that, The controller stores the following control strategies: A preset strategy; Strategy ①: The controller closes all the third directional valves, opens the second directional valve to conduct the accumulator and the hydraulic cylinder of the corresponding hydraulic device, and reduces the driving speed of the AGV; Strategy ②: The controller selectively opens the corresponding third directional valve to form a connection suspension between several mutually conducted hydraulic devices, and closes the second directional valves of each hydraulic device in the connection suspension to close the accumulator; The control method includes the following steps: Step 1: Detect the load condition of the AGV. When there is a load, obtain the center of gravity position of the load on the AGV frame; Step 2: Select the corresponding control strategy: (1) When the AGV is unloaded, execute the preset strategy; (2) When the load weight of the AGV is within the first weight range, execute Strategy ②, and make the center of gravity position of the load located between the equivalent support points of several connected suspensions or within the support surface enclosed by the equivalent support points of several connected suspensions and the support points of several independent hydraulic devices; (3) When the load weight of the AGV is within the second weight range, execute Strategy ①, where the weight in the first weight range is less than the weight in the second weight range.

5. The control method of the hydraulic system according to claim 4, characterized in that, When executing Strategy ②, adjust the hydraulic devices to be turned on according to the dynamic situation of the piston rod stroke data of the hydraulic cylinders of each hydraulic device and the load distribution situation, so as to reconstitute the connection suspension. When the length of the AGV frame exceeds the preset length threshold, or the center of gravity position of the load is in the offloading area of the frame, or the AGV is about to enter a concave section, give priority to selecting Strategy ①.

6. The control method of the hydraulic system according to claim 4, wherein, The controller divides the frame of the AGV into a preset loading range and a non-preset loading range, and correspondingly sets a first control scheme group and a second control scheme group. A variety of control schemes for forming a support surface within the preset loading range are stored in the first control scheme group, and a variety of control schemes for forming a support surface within the non-preset loading range are stored in the second control scheme group. When selecting Strategy ②, if the load center of gravity position is within the preset loading range, sequentially select control schemes in the first control scheme until the support surface of the selected control scheme covers the center of gravity of the load. If the load center of gravity position is within the non-preset loading range, sequentially select control schemes in the second control scheme until the support surface of the selected control scheme covers the center of gravity position of the load, or when the support surfaces formed by all the control schemes in the second control scheme group cannot cover the center of gravity position of the load, send an alarm signal.

7. The control method of the hydraulic system according to claim 4, characterized in that, The controller obtains the load situation of the AGV by comparing the real-time pressure values of the hydraulic cylinders of each hydraulic device with their initial pressure values; and sets the preset strategy according to the initial pressure value. Obtaining the initial pressure value includes an initial value setting step before executing Step 1: Place the AGV on a horizontal plane and in an unloaded state, and perform initialization processing on the data. By switching the state of the first reversing valve, the hydraulic cylinders of each hydraulic device are made to return oil, and each hydraulic cylinder descends to the lowest position. Close the third reversing valve to keep each hydraulic device in an independent state. Close the accumulators of each hydraulic device. By switching the state of the first reversing valve, the hydraulic cylinders of each hydraulic device are made to intake oil, and each hydraulic cylinder rises to the preset initial height. Obtain the pressure values of each hydraulic cylinder at this time and store them as the corresponding initial pressure values.

8. The control method of the hydraulic system according to claim 7, characterized in that When detecting the load situation of the AGV, if the real-time pressure values of the hydraulic cylinders of each hydraulic device exceed the safety threshold, send an alarm signal.

9. The control method of the hydraulic system according to claim 4, characterized in that, It also includes a self-check step before detecting the load situation of the AGV: When the AGV receives a running command, by switching the state of the first reversing valve, the hydraulic cylinders of each hydraulic device are made to return oil, and each hydraulic cylinder descends to the lowest position. Close the third reversing valve to keep each hydraulic device in an independent state. Close the accumulators of each hydraulic device. By switching the state of the first reversing valve, the hydraulic cylinders of each hydraulic device are made to intake oil, and each hydraulic cylinder rises to the preset height. Judge whether the actions and dynamic pressure values during the rising process of the hydraulic cylinders are normal. If normal, judge the load situation of the AGV, otherwise send an alarm signal.

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