Aerial work vehicle and its control unit

Abstract

An aerial work vehicle includes: an upper vehicle, an arm supported by the upper vehicle, a lifting platform supported by the arm, a variable amplitude cylinder for controlling the arm angle, a telescopic cylinder for controlling the arm length, a hydraulic pump for supplying hydraulic oil to the variable amplitude cylinder and the telescopic cylinder through a variable amplitude valve and a telescopic valve, respectively, and a control unit, wherein the control unit is configured to: determine a desired angle and a desired length of the arm at each of a plurality of selected points in a desired trajectory based on a desired desired trajectory of the lifting platform; obtain a current actual angle and a current actual length of the arm; for each point in the desired trajectory, determine a variable amplitude valve control current based on the desired angle and the current actual angle, and control the opening of the variable amplitude valve with the determined variable amplitude valve control current, thereby implementing open-loop control of the arm angle to achieve arm variable amplitude; and at the same time, implementing control of the arm length based on the desired length, the current actual length and the current actual angle to achieve arm telescoping.

Description

Technical Field

[0001] The present application relates to a control unit for an aerial work vehicle, which can realize the automatic movement of a lifting platform according to an input trajectory. The present application also relates to an aerial work vehicle comprising such a control unit. Background Art

[0002] An aerial work platform (AWP) is a device used for aerial work, primarily in construction sites, power projects, streetlight maintenance, and other municipal applications. Aerial work platforms typically consist of two main components: a lower section and a lower section. The lower section allows the AWP to move on the ground, while the upper section uses a telescopic boom to move the platform to the desired position in the air. The boom of an aerial work platform typically has both variable amplitude and telescopic functions. The variable amplitude function changes the boom's angle, while the telescopic function changes its length. By simultaneously controlling the boom's angle and length, the platform can be moved vertically, horizontally, or along other paths.

[0003] In some usage scenarios, such as installing glass and painting walls, vertical or horizontal movement is often required. In these cases, the working trajectory should usually be a vertical or horizontal straight line. However, due to the immaturity of existing technologies or poor control accuracy, most aerial work vehicles currently cannot automatically control the lifting platform to automatically move along the desired trajectory, especially a straight trajectory. In order to achieve movement along the desired trajectory to a target position, the operator needs to perform complicated operations and repeatedly control the amplitude and extension of the straight arm to try, resulting in a waste of time and energy. Summary of the Invention

[0004] One object of the present application is to provide a control unit for an aerial work vehicle, which can control a lifting platform to automatically move along a desired trajectory to reach a target position.

[0005] To achieve this objective, the present application provides, in one aspect, a control unit for an aerial work vehicle, the aerial work vehicle comprising: an upper vehicle, an arm supported by the upper vehicle, a lifting platform supported by the arm, a luffing cylinder for controlling the arm angle, a telescopic cylinder for controlling the arm length, and a hydraulic pump for supplying hydraulic oil to the luffing cylinder and the telescopic cylinder through a luffing valve and a telescopic valve, respectively; the control unit is configured to:

[0006] determining a desired angle and a desired length of the arm at each of a plurality of selected points in the desired trajectory based on the desired desired trajectory of the lift;

[0007] Obtaining the current actual angle and the current actual length of the arm;

[0008] For each point in the desired trajectory, a luffing valve control current is determined based on the desired angle and the current actual angle, and the opening of the luffing valve is controlled according to the determined luffing valve control current, thereby implementing open-loop control of the arm angle to achieve arm luffing; at the same time, the arm length is controlled based on the desired length, the current actual length and the current actual angle to achieve arm extension and retraction.

[0009] In one embodiment, the control unit stores a pre-calibrated correspondence between each angle or angular velocity of the arm and the luffing valve control current, and determines the luffing valve control current using the correspondence between the angle or angular velocity and the luffing valve control current.

[0010] In one embodiment, the control unit is configured to store a pre-calibrated angular velocity limit at each angle of the arm, and the control unit determines the desired angular velocity based on the desired angle at each determined point and the expected time to reach each point, and if the angular velocity required to reach a certain point exceeds the corresponding angular velocity limit, the control current of the variable amplitude valve is reduced so that the angular velocity of the arm does not exceed the angular velocity limit.

[0011] In one embodiment, for each point in the desired trajectory, the control of the arm length by the control unit is an open loop control.

[0012] In one embodiment, the control unit stores a pre-calibrated correspondence between each length or linear velocity of the arm and the telescopic valve control current, and determines the telescopic valve control current using the correspondence between the length or linear velocity and the telescopic valve control current.

[0013] In one embodiment, for each point in the desired trajectory, the control unit implements PID closed-loop control on the arm length, wherein the control unit corrects the arm extension and retraction amount based on the arm length acquired in real time.

[0014] In one embodiment, the control unit stores lifting platform movements for the operator to select, and the lifting platform movements at least include: horizontal linear movement; vertical linear movement.

[0015] In one embodiment, the control unit is configured to automatically determine the lift platform trajectory based on the lift platform target position input by the operator.

[0016] In one embodiment, the arm includes multiple arm segments, each arm segment is equipped with its own amplitude-changing cylinder, each amplitude-changing cylinder is equipped with a corresponding amplitude-changing valve, and the end arm segment is equipped with the telescopic cylinder, and the control unit is configured to: determine the expected angle of each arm segment at each point in the expected trajectory and the expected length of the end arm segment based on the expected trajectory of the expected lifting platform, and determine the control current of each amplitude-changing valve based on the expected angle and the current actual angle of each arm segment; and control the opening of each amplitude-changing valve at each point with the determined amplitude-changing valve control current, thereby implementing open-loop control of the arm angle to achieve arm amplitude change, and at the same time, determine the telescopic valve control current based on the expected length and the current actual length of the end arm segment and the current actual angle of each arm segment, and control the opening of the telescopic valve with the determined telescopic valve control current, thereby implementing control on the arm length to achieve arm extension and retraction.

[0017] In one embodiment, the control unit is configured to optimize the desired angle of each arm segment at each point with an optimization objective.

[0018] The present application also provides an aerial work vehicle, which includes: an upper vehicle; an arm supported by the upper vehicle, the arm including a straight arm or a curved arm; a lifting platform supported by the arm; a variable amplitude cylinder for controlling the angle of the arm; a telescopic cylinder for controlling the length of the arm; a hydraulic pump that supplies hydraulic oil to the variable amplitude cylinder and the telescopic cylinder through a variable amplitude valve and a telescopic valve respectively; and a control unit of the present application, which is configured to automatically control the movement of the arm based on the desired trajectory of the desired lifting platform.

[0019] The control unit of this application enables efficient aerial work platform operation, eliminating complex operator operations and saving time. It also achieves excellent control accuracy, with minimal deviation between the actual movement trajectory and the input desired trajectory. Furthermore, the primary action is the boom's luffing, allowing for more efficient use of hydraulic energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present application may be further understood by reading the following detailed description with reference to the accompanying drawings, in which:

[0021] Figure 1 This is the architecture of an aerial work vehicle according to a feasible implementation method of the present application;

[0022] Figure 2 is a block diagram of the control logic executed by the control unit of the aerial work vehicle according to the present application;

[0023] Figure 3 、 Figure 4 It is the architecture of an aerial work vehicle according to other feasible embodiments of the present application;

[0024] Figure 5-Figure 8 It is a graph of experimental data showing the control effect of the control unit of the present application. DETAILED DESCRIPTION

[0025] The present application generally relates to a vehicle for aerial work (or aerial work platform) and its control unit. A feasible structure of the aerial work vehicle is Figure 1 is shown in a highly simplified form. Figure 1 As shown, the boom of a telescopic aerial work vehicle includes a telescopic arm 3 mounted on an upper vehicle 1. The lower end of the telescopic arm 3 is hinged to rotate relative to the upper vehicle 1, and the upper end of the telescopic arm 3 supports a lifting platform (also known as a platform, work platform, etc.) 4. The upper vehicle 1 is horizontally rotatably supported on the lower vehicle 2. The lower vehicle 2 has multiple wheels and can move on the ground.

[0026] The straight arm 3 has a luffing function and a telescopic function. The luffing function is achieved by a luffing cylinder 5 installed on the upper vehicle 1. The lower end of the luffing cylinder 5 is supported by a bracket on the upper vehicle 1 through a hinge, and the upper end of the luffing cylinder 5 supports the main body of the straight arm 3 through a hinge. The extension or shortening of the luffing cylinder 5 can change the angle A (measured relative to the horizontal direction) of the straight arm 3, thereby achieving the luffing of the straight arm 3. A telescopic cylinder 6 is provided on the main body of the straight arm 3, and the end of the telescopic cylinder 6 carries the lifting platform 4. The extension or shortening of the telescopic cylinder 6 can change the length L of the straight arm, thereby achieving the extension and retraction of the straight arm 3. The power source of the luffing cylinder 5 and the telescopic cylinder 6 is a hydraulic pump (not shown), which supplies hydraulic oil to the luffing cylinder 5 and the telescopic cylinder 6 through the luffing valve and the telescopic valve (both not shown) to actuate the luffing cylinder 5 and the telescopic cylinder 6. Both the luffing valve and the telescopic valve are three-position electro-proportional valves. Their opening is determined by the magnitude of the input control current, thereby determining the extension and retraction speed of the luffing cylinder 5 and the telescopic cylinder 6. The valve position determines the flow direction of the hydraulic oil, thereby determining the movement direction of the luffing cylinder 5 and the telescopic cylinder 6. Such hydraulic pumps and main valves in aerial work platforms are well known in the art and will not be described in detail.

[0027] The aerial work vehicle has a control unit (not shown), which controls the operation of various control elements of the aerial work vehicle, including the pump of the hydraulic system (which may include a main pump and a sub-pump) and various control valves, and obtains signals from sensors equipped to detect the movement of each action element, including an angle sensor and a length sensor (not shown) of the straight arm 3, so as to know the actual position and posture of each action element.

[0028] The hinge at the lower end of the straight arm 3 and the hinges at both ends of the boom cylinder 5 are parallel to each other and are arranged along the horizontal direction (left and right direction) of the aerial work vehicle. Therefore, the actuation of the boom cylinder 5 will change the longitudinal (front and back direction) and vertical (up and down direction) positions of the lifting platform 4. On the other hand, the actuation of the telescopic cylinder 6 will also change the longitudinal and vertical positions of the lifting platform 4. If it is necessary to change the lateral position of the lifting platform 4, it is necessary to rotate the upper vehicle 1 relative to the lower vehicle 2. If it is necessary to achieve the precise lateral position of the lifting platform 4, it is necessary to simultaneously rotate the upper vehicle 1 relative to the lower vehicle 2 and actuate the telescopic cylinder 6. In the following, the longitudinal direction is referred to as the X direction, the vertical direction is referred to as the Z direction, and the lateral direction is referred to as the Y direction.

[0029] The present application mainly relates to a controller automatically controlling the movement of the lifting platform 4 based on an input expected trajectory or target position of the lifting platform 4 .

[0030] To this end, a human-machine interface, such as a touch panel, can be provided in the operator's cab of the aerial work vehicle for the operator to input the desired trajectory or position of the lifting platform 4. The control unit can pre-store movement modes that the lifting platform 4 can automatically execute, and various automatic movement modes can be displayed on the human-machine interface.

[0031] As described above, the actuation of the luffing cylinder 5 (corresponding to the luffing of the straight arm 3) and the actuation of the telescopic cylinder 6 (corresponding to the telescoping of the straight arm 3) can change the X- and Z-direction positions of the lifting platform 4. To this end, one aspect of the control unit of the present application is that the control unit can achieve the movement of the lifting platform 4 along any trajectory in the XZ plane by simply controlling the movement of the straight arm 3. Typical motion trajectories in the XZ plane that the control unit can automatically achieve include:

[0032] Horizontal and vertical movement, where only the X coordinate changes, and the Z coordinate remains unchanged;

[0033] Vertical movement, in which only the Z coordinate is changed and the X coordinate remains unchanged;

[0034] Movement along a specific trajectory, such as a curved (e.g., circular) segment or a straight line segment, or a curved-curved, curved-straight, or straight-line segment combination, wherein both the X and Z coordinates change.

[0035] The control unit can store various XZ-plane motion trajectories and display them on the human-machine interface for the operator to select. Furthermore, the human-machine interface allows for input of a desired absolute or relative target position (possibly with one or more intermediate positions) of the lifting platform 4, or a desired movement distance in one or more directions relative to the current position.

[0036] According to the motion trajectory and target position (possibly intermediate position) or moving distance input by the operator, the control unit can automatically control the straight arm 3, so that the variable amplitude cylinder 5 and the telescopic cylinder 6 are actuated to bring the lifting platform 4 to the position desired by the operator.

[0037] The control unit can also automatically plan the motion trajectory of the lift platform 4 in the XZ plane based solely on the operator's input of the target position in the XZ plane (and possibly one or more intermediate positions). For example, if the operator's input target position changes in the X and Z coordinates relative to the current position, the control unit can calculate the trajectory (straight line or broken line, etc.) from the current position to the target position. The change in the X and Z coordinates can be positive or negative. For example, +X indicates forward longitudinally, -X indicates backward longitudinally; +Z indicates vertically upward, and -Z indicates vertically downward.

[0038] The control unit can perform position control on some selected points in the trajectory based on the movement trajectory of the lifting platform 4 input by the operator or calculated by the control unit itself, that is, determine the length and angle of the straight arm 3 at each selected point in the trajectory, and thereby control the action of the variable amplitude cylinder 5 and the telescopic cylinder 6, so that the lifting platform 4 passes through each point in sequence according to the predetermined time during the movement.

[0039] When the control unit controls the movement of the boom 3, it also controls the extension and retraction of the luffing and telescopic cylinders 5 and 6 by controlling the position and opening of the luffing and telescopic valves. The position of the luffing and telescopic valves depends on which control terminal is energized, while the opening depends on the amount of control current supplied to that control terminal.

[0040] Since the boom cylinder 5 and the telescopic cylinder 6 are supplied with hydraulic oil by the same pump, for one or some points in the trajectory, due to the limitation of the pump's output flow rate, it may not be possible to simultaneously meet the desired movements of the boom cylinder 5 and the telescopic cylinder 6. To this end, the present application regards the boom 3's boom movement achieved by the boom cylinder 5 as the main movement, implements open-loop control on the boom movement, and regards the telescopic movement of the telescopic cylinder 6 as the auxiliary movement. The telescopic movement can adopt open-loop, but preferably closed-loop control, to follow the boom movement to achieve the final target position. In other words, for the intermediate points that are limited by the pump's output flow rate, it is not required that the boom movement of the intermediate points precisely reach the desired boom angle, thereby ensuring the feasibility of reaching the target position through the motion trajectory.

[0041] The control unit of this application executes a logic of this control strategy in Figure 2 As shown in Figure 2 As shown in , the control unit includes a first module Ma, a second module Mb, a third module Mc, and a fourth module Md, and the control unit collects measurement data of the angle sensor Bas and the length sensor Bls of the straight arm 3.

[0042] The first module Ma receives the input instructions C from the operating lever J of the aerial work vehicle and the human-machine interface S, as well as the current actual angle Aa of the straight arm 3 detected by the angle sensor Bas of the straight arm 3. It should be pointed out that the operating lever J is used to determine the start and stop of the automatic action. After the operator inputs the motion instruction through the human-machine interface S, the corresponding operating lever J is started, and the control unit executes the automatic control consciousness to automatically move the straight arm 3, and stops the movement after the lifting platform 4 reaches the target position. During the movement process, once the operator releases the operating lever J, the lifting platform 4 will stop immediately regardless of whether it reaches the target position. Alternatively, a button on the human-machine interface can be used to control the start and stop of the automatic action.

[0043] The first module Ma determines the desired angle of the boom 3 at the next selected point in the desired trajectory based on the information about the desired trajectory of the lifting platform 4 contained in the received input command C. The first module Ma also receives the current actual angle Aa of the boom 3. Based on the change in the desired angle of the boom 3 at the next point relative to the current actual angle Aa of the boom 3, the first module Ma determines the required luffing angle to reach the next point. Based on the determined required luffing angle and the estimated time required to reach the next selected point, the luffing angular velocity of the luffing valve can be determined. The first module Ma stores a pre-calibrated correspondence, such as a curve or data table, between each angle or angular velocity in the movement of the boom 3 and the luffing valve control current. Based on this correspondence and the required luffing angle or angular velocity, the first module Ma determines the required luffing valve control current Ca to reach the next point and transmits the luffing valve control current Ca to the fourth module Md. The fourth module Md controls the position and opening of the luffing valve based on the luffing valve control current Ca to control the angle of the luffing cylinder 5 and, thereby, the luffing of the boom 3.

[0044] The amplitude variation control of the straight arm 3 is an open-loop control, and there is no need to correct the amplitude variation using the deviation of the current actual angle Aa of the straight arm 3 detected by the angle sensor Bas relative to the desired angle at each point in the trajectory.

[0045] The second module Mb receives input commands C from the aerial work vehicle's joystick J and the human-machine interface S, as well as the current actual angle Aa of the straight arm 3 detected by the angle sensor Bas of the straight arm 3 and the current actual length La of the straight arm 3 detected by the length sensor Bls of the straight arm 3. Based on the geometric positional relationship between the lifting platform 4 and the straight arm 3 and the current actual angle Aa and current actual length La of the straight arm 3, the second module Mb determines the expected length Lt of the straight arm 3 at the next point in the expected trajectory, and sends the determined expected length Lt to the third module Mc.

[0046] The third module Mc receives the desired length Lt at the next point. The third module Mc can perform open-loop control to adjust the length of the straight arm 3. To this end, the third module Mc stores a pre-calibrated correspondence between each length or linear velocity of the straight arm 3 (or telescopic cylinder 6) and the telescopic valve control current, such as a curve or a data table. The third module Mc determines the telescopic valve control current Cl required to reach the next point based on the correspondence and the desired length Lt or the desired linear velocity (determined by the desired length and the expected time to reach the next point), and sends the telescopic valve control current Cl to the fourth module Md. The fourth module Md controls the valve position and opening of the telescopic valve based on the telescopic valve control current Cl to control the telescopic distance of the telescopic cylinder 6 and thereby control the length of the straight arm 3. The straight arm amplitude control and length control performed by the fourth module Md are preferably performed synchronously.

[0047] It can be seen that when the second module Mb calculates the expected length Lt of the straight arm 3 at the next point in the expected trajectory, the factor of the current actual angle Aa of the straight arm 3 detected by the angle sensor Bas is taken into account, which makes the telescopic action of the straight arm 3 follow its amplitude variation action.

[0048] The telescopic control of the straight arm 3 described above is open-loop control, and there is no need to correct the telescopic action of the telescopic cylinder 6 at each point in the trajectory using the deviation of the current actual length La of the straight arm 3 detected by the length sensor Bls relative to the expected length.

[0049] However, it is more preferred to design the telescopic control of the straight arm 3 into a closed-loop control, wherein for each selected point in the trajectory, it is not necessary to store the pre-calibrated correspondence between the length or linear speed of the straight arm 3 and the telescopic valve control current in the third module Mc. Instead, PID control is performed based on the current actual length La of the straight arm 3 received from real-time monitoring to determine in real time the telescopic distance that the telescopic cylinder 6 will complete at the next point, and to adjust the telescopic valve control current Cl in real time. The fourth module Md controls the valve position and opening of the telescopic valve based on the telescopic valve control current Cl determined in real time in the third module Mc to control the telescopic distance of the telescopic cylinder 6 and thereby control the length of the straight arm 3, so that the length of the straight arm is as close to the desired length as possible at each point. Closed-loop control of the telescopic extension of the straight arm 3 can improve the position accuracy of the lifting platform 4 passing through each point, and make the actual trajectory of the lifting platform 4 consistent with the desired trajectory as much as possible to avoid excessive deviation.

[0050] Furthermore, the desired angular velocity of the straight arm 3 can be determined by differentiating the desired angle of the straight arm 3 at each point with respect to time. However, due to the limited supply of hydraulic oil, the desired angular velocity of the straight arm 3 may not be achieved at some points. In order to avoid the straight arm 3 failing to reach the desired angular velocity, an angular velocity limit may be pre-set for each angular position of the straight arm 3. If the angular velocity required to reach the desired angle at a certain point exceeds the angular velocity limit corresponding to the angle, the amplitude change cylinder is controlled to drive the straight arm 3 to change amplitude at an angular velocity not exceeding (i.e., equal to or lower than) the angular velocity limit (achieved by constraining the amplitude change valve control current), so that the straight arm 3 reaches the angular position at that point at an angular velocity that is slower than expected. In this way, the actual trajectory of the lifting platform 4 can be ensured to be highly accurate.

[0051] It is understandable that the above four modules in the control unit can all be program blocks in the control program. In actual design of the control program, various designs suitable for actual applications can be made for these four modules, and it may not be necessary to strictly distinguish these four modules.

[0052] Previous reference Figure 1 The straight-arm aerial work vehicle in the embodiment describes the control scheme executed by the control unit to realize the automatic execution of the trajectory of the lifting platform 4 in the XZ plane. The principle of the control unit of this application is also applicable to the articulated-arm aerial work vehicle.

[0053] For example, in Figure 3 The figure shows a highly simplified version of a boom-type aerial work vehicle. The boom comprises a straight boom 3 and folding booms 31 and 32. The folding boom 31 is mounted on the upper vehicle 2. The folding boom 31 is driven by a first luffing cylinder 51 positioned between the upper vehicle 1 and the boom 31, changing its angle. The folding boom 32 is driven by a second luffing cylinder 52 positioned between the two arms 31 and 32. The lower end of the straight boom 3 is hinged to the upper end of the folding boom 32, which supports the lifting platform 4. The lower end of the luffing cylinder 5 is hinged to the folding boom 32, while the upper end of the luffing cylinder 5 supports the main body of the straight boom 3 via a hinge. A telescopic cylinder 6 is mounted on the main body of the straight boom 3, and the distal end of the telescopic cylinder 6 supports the lifting platform 4. The entire boom is adjusted in amplitude by the luffing cylinder 5, the first luffing cylinder 51, and the second luffing cylinder 52. Telescopic cylinder 6 also controls the extension and retraction of the entire boom.

[0054] For example, in Figure 4The figure shows a highly simplified version of another articulated boom aerial work vehicle. The boom comprises a straight boom 3 and folding booms 31 and 32. Each folding boom 31 and 32 is a parallelogram-shaped four-bar linkage. The folding boom 31 is mounted on the upper vehicle 2, while the folding boom 32 is mounted on the upper end of the boom 31. The straight boom 3 is mounted on a bracket at the upper end of the folding boom 32. A luffing cylinder 53, positioned between the upper vehicle 1 and the folding boom 32, drives the folding boom 32 and simultaneously drives the folding boom 31. Actuation of the luffing cylinder 53 changes the height of the bracket at the upper end of the folding boom 32, i.e., its Z-axis position. The lower end of the luffing cylinder 5 is hingedly supported by the bracket at the upper end of the folding boom 32, while the upper end of the luffing cylinder 5 also hingesly supports the main body of the straight boom 3. A telescopic cylinder 6 is mounted on the main body of the straight boom 3, the distal end of which supports the lifting platform 4. The luffing cylinder 5 controls the entire boom's amplitude. The telescopic cylinder 6 also controls its extension and retraction.

[0055] Other types of articulated boom lifts can also utilize the control unit of this application. For various articulated boom lifts, the straight arm and folding arm (not necessarily limited to two) can be generally referred to as boom sections. The entire boom section changes angle via one or more corresponding luffing cylinders. The end boom section is equipped with a telescopic cylinder. The telescopic and luffing cylinders are supplied with hydraulic oil from a common hydraulic pump.

[0056] Applies to Figure 3 、 Figure 4 The control unit of the articulated boom lift shown or its form may be configured to perform Figure 2 Because there are multiple luffing cylinders, the desired arm luffing can be achieved by optimizing the angle of each arm segment or the flow distribution of each luffing cylinder (for example, with the goal of minimizing energy consumption, minimizing the total driving force of each luffing cylinder, and ensuring smooth transition between the luffing and telescopic speeds at each point).

[0057] As an example, in the first module of the control unit, based on information about the desired trajectory of the lifting platform 4 contained in the received input command, optimization is used to determine the desired angle of each boom segment at the next of multiple selected points along the desired trajectory. The first module also receives the current actual angle of each boom segment from the angle sensor equipped on each boom segment. Based on the change in the desired angle of each boom segment at the next point relative to the current actual angle of each boom segment, the first module determines the required boom angle and angular velocity to reach the next point. The first module stores pre-calibrated correspondences between each angle or angular velocity of each boom segment's movement and the boom valve control current. Based on this correspondence and the required boom angle or angular velocity, the first module determines the required boom valve control current for each boom cylinder to reach the next point and transmits the boom valve control current to the fourth module. The fourth module controls the valve position and opening of each boom valve based on the boom valve control current to control the angle of each boom cylinder and, thereby, the boom boom. In this example, the boom boom control is also open-loop control.

[0058] The second module receives the input command, the current actual angle of each arm segment as detected by the angle sensor of each arm segment, and the current actual length of the end arm segment as detected by the length sensor of the end arm segment. Based on the geometric positional relationship between the lifting platform 4 and each arm segment, the current actual angle of each arm segment, and the current actual length of the end arm segment, the second module determines the desired length of the end arm segment (or telescopic cylinder 6) at the next point in the desired trajectory, and sends the determined desired length to the third module.

[0059] The third module receives the desired length at the next point. The third module can perform open-loop control to adjust the length of the end arm segment. To this end, the third module stores the correspondence between each length or linear velocity of the end arm segment (or telescopic cylinder 6) and the telescopic valve control current that has been pre-calibrated. The third module determines the telescopic valve control current required to reach the next point based on the correspondence and the desired length or linear velocity, and sends the telescopic valve control current to the fourth module. The fourth module controls the valve position and opening of the telescopic valve based on the telescopic valve control current to control the length of the telescopic cylinder 6 and thereby control the telescopic distance of the end arm segment, that is, the length of the entire arm. The arm amplitude control and length control performed by the fourth module are preferably performed synchronously. In this open-loop control of the length of the end arm segment, there is no need to use the deviation of the current actual length of the end arm segment detected by the length sensor relative to the desired length to correct the telescopic action of the telescopic cylinder 6.

[0060] However, it is more preferred to design the telescopic control of the arm as a closed-loop control, wherein for each selected point in the trajectory, it is not necessary to store the pre-calibrated correspondence between the end arm segment length or linear speed and the telescopic valve control current in the third module. Instead, PID control is performed based on the current actual length of the end arm segment received from real-time monitoring to determine in real time the telescopic distance to be completed by the telescopic cylinder 6 at the next point, and the telescopic valve control current of the telescopic cylinder 6 is adjusted in real time. The fourth module controls the valve position and opening of the telescopic valve of the telescopic cylinder 6 based on the telescopic valve control current determined in real time in the third module to control the telescopic distance of the telescopic cylinder 6 and thereby control the length of the end wall segment, so as to make the length of the end arm segment as close to the desired length as possible at each point.

[0061] The arm control performed by the control unit described above involves changes in the X and Z coordinates of the lifting platform 4. If a desired trajectory of the lifting platform 4 requires a change in the Y coordinate, the control unit needs to synchronously control the rotation of the upper vehicle 1 relative to the lower vehicle 2.

[0062] It should be noted that the arm's amplitude and angle control do not involve changes in the Y coordinate, while the control of the vehicle's rotation does involve changes in the Y coordinate and also involves a small change in the X coordinate. Therefore, when the control unit performs arm control, the X coordinate change caused by the rotation of the vehicle should be taken into account.

[0063] In order to verify the effect of the control unit of this application, Figure 1 The straight arm aerial work vehicle shown in the figure was subjected to a straight arm control experiment. The experimental results are shown in Figure 5-Figure 8 In display.

[0064] exist Figure 5-Figure 8 In the example, the horizontal axis represents the change in time. Figure 5 、 Figure 7 In the diagram, the vertical axis represents the length of the straight arm (unit: mm, value range: 15000-25000) and the angle of the straight arm (unit: °, vertical range: 0-60). Figure 6 、 Figure 8 In FIG. 1 , the vertical axis represents the X and Z coordinates of the lifting platform 4 (unit: mm, numerical range: 0 to 20,000).

[0065] Figure 5 、 Figure 6 Yes Figure 1 The result shown is that the aerial work vehicle performs the control of the vertical lifting of the lifting platform 4, wherein the boom amplitude change adopts open loop control and the boom extension and retraction adopts closed loop control. Figure 5 The curve S1 in FIG. 1 represents the straight arm length measured during the entire lifting process, and the curve S2 represents the straight arm angle measured. Figure 6 The curve S3 in FIG. 5 represents the X coordinate measured during the entire lifting process, and the curve S4 represents the Z coordinate measured.

[0066] from Figure 6 It can be seen that during the vertical lifting process, the X coordinate remains basically unchanged, with an error within the range of ±100mm.

[0067] Figure 7 、 Figure 8 Yes Figure 1 The result shown is that the aerial work vehicle executes the control of the horizontal forward and backward movement of the lifting platform 4, wherein the boom amplitude change adopts open loop control and the boom extension and retraction adopts closed loop control. Figure 7 The curve S5 in FIG. 5 represents the straight arm length measured during the entire horizontal movement process, and the curve S6 represents the straight arm angle measured. Figure 8 The curve S7 in FIG. 5 represents the X coordinate measured during the entire horizontal movement process, and the curve S8 represents the Z coordinate measured.

[0068] from Figure 8 It can be seen that during the forward and backward horizontal movement, the Z coordinate remains basically unchanged, with an error within the range of ±100mm.

[0069] It can be seen from the above experimental results that the control unit of the present application can achieve high-precision automatic trajectory control of the aerial work vehicle.

[0070] The aerial work vehicle control unit of the present application is configured to determine the position that the lifting platform will reach at each moment based on the input movement trajectory, with the amplitude change of the straight arm as the main action, and open-loop control is implemented on the amplitude change action, with the telescopic action of the straight arm as the auxiliary action, and the telescopic action follows the amplitude change action to achieve the final target position. The control of the telescopic action is preferably closed-loop control. The present application makes the aerial work vehicle highly efficient in operation, does not require complicated operations by the operator, and can save time. At the same time, excellent control accuracy can be achieved, and the deviation between the actual movement trajectory and the input expected trajectory is very small. In addition, with the amplitude change of the straight arm as the main action, hydraulic energy can be used more efficiently.

[0071] Although the present application is described herein with reference to specific embodiments, the scope of the present application is not limited to the details shown. Various modifications may be made to these details without departing from the basic principles of the present application.

Claims

1. A control unit for an aerial work vehicle, the aerial work vehicle comprising: An upper vehicle (1), an arm supported by the upper vehicle (1), a lifting platform (4) supported by the arm, a luffing cylinder (5) for controlling the angle of the arm, a telescopic cylinder (6) for controlling the length of the arm, and a hydraulic pump for supplying hydraulic oil to the luffing cylinder (5) and the telescopic cylinder (6) through a luffing valve and a telescopic valve, respectively; The control unit is configured to: determining a desired angle and a desired length of the arm at each of a plurality of selected points in the desired trajectory based on the desired desired trajectory of the lift; Obtaining the current actual angle and the current actual length of the arm; For each point in the desired trajectory, a luffing valve control current is determined based on the desired angle and the current actual angle, and the opening of the luffing valve is controlled according to the determined luffing valve control current, thereby implementing open-loop control on the arm angle to achieve arm luffing; simultaneously, the arm length is controlled based on the desired length, the current actual length, and the current actual angle to achieve arm extension and retraction; Among them, the amplitude change action is the main action, and the telescopic action is the auxiliary action; for the intermediate point in the desired trajectory where the output flow of the hydraulic pump cannot simultaneously meet the desired actions of the amplitude change cylinder (5) and the telescopic cylinder (6), it is not required that the amplitude change action of the intermediate point accurately reach the desired arm angle, but only ensures that the target position is reached through the motion trajectory; The control unit is configured to store a pre-calibrated angular velocity limit at each angle of the arm, and determine the desired angular velocity based on the desired angle at each determined point and the expected time to reach each point. If the angular velocity required to reach a certain point exceeds the corresponding angular velocity limit, the control current of the variable amplitude valve is reduced so that the angular velocity of the arm does not exceed the angular velocity limit.

2. The control unit according to claim 1, wherein: The control unit stores a pre-calibrated correspondence between each angle or angular velocity of the arm and the luffing valve control current, and determines the luffing valve control current using the correspondence between the angle or angular velocity and the luffing valve control current.

3. The control unit according to claim 1, wherein: For each point in the desired trajectory, the control of the arm length by the control unit is an open loop control.

4. The control unit according to claim 3, wherein: The control unit stores a pre-calibrated correspondence between each length or linear velocity of the arm and the telescopic valve control current, and determines the telescopic valve control current using the correspondence between the length or linear velocity and the telescopic valve control current.

5. The control unit according to claim 1, wherein: For each point in the desired trajectory, the control unit implements PID closed-loop control on the arm length, wherein the control unit corrects the arm extension and contraction amount based on the arm length acquired in real time.

6. The control unit according to any one of claims 1 to 5, wherein: The control unit stores the lifting platform movements for the operator to select, and the lifting platform movements include at least: Horizontal straight line movement; Vertical straight line movement.

7. The control unit according to any one of claims 1 to 5, wherein: The control unit is configured to automatically determine the lift platform trajectory based on the lift platform target position input by the operator.

8. The control unit according to any one of claims 1 to 5, wherein: The arm comprises a plurality of arm sections, each arm section is equipped with its own luffing cylinder, each luffing cylinder is equipped with a corresponding luffing valve, and the end arm section is equipped with the telescopic cylinder, and the control unit is configured to: Based on the expected trajectory of the lifting platform, the expected angle of each arm segment at each point in the expected trajectory and the expected length of the end arm segment are determined, and the control current of each variable amplitude valve is determined based on the expected angle and the current actual angle of each arm segment; and at each point, the opening of each variable amplitude valve is controlled by the determined variable amplitude valve control current, so as to implement open-loop control of the arm angle to achieve arm amplitude variation, and at the same time, the telescopic valve control current is determined based on the expected length and the current actual length of the end arm segment and the current actual angle of each arm segment, and the opening of the telescopic valve is controlled by the determined telescopic valve control current, so as to implement control on the arm length to achieve arm telescoping.

9. The control unit according to claim 8, wherein: The control unit is configured to optimize the desired angle of each arm segment at each point according to an optimization objective.

10. An aerial work vehicle comprising: Get on the bus (1); An arm supported by the upper vehicle (1), the arm comprising a straight arm or a curved arm; a lifting platform (4) supported by the arm; A luffing cylinder (5) for controlling the arm angle; a telescopic cylinder (6) for controlling the length of the arm; a hydraulic pump for supplying hydraulic oil to the luffing cylinder (5) and the telescopic cylinder (6) through the luffing valve and the telescopic valve, respectively; as well as The control unit according to any one of claims 1 to 9, wherein the control unit is configured to automatically control the movement of the arm based on a desired trajectory of the lifting platform.

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