Control methods and control systems for construction machinery and construction machinery

Abstract

This invention relates to the field of hydraulic technology, and provides a control method, a control system, and the engineering machinery. The control method for the engineering machinery includes: inputting a desired boom rotation angular velocity ω; the controller acquiring the current angle parameter θ of the boom; and the controller acquiring the theoretical flow rate Q of the hydraulic cylinder exiting the rodless chamber based on the angular velocity ω and the angle parameter θ. 缸 The controller obtains the pressure difference ΔP across the balancing valve; based on the flow rate Q passing through the balancing valve... 缸 The differential pressure ΔP is used to obtain the pilot pressure of the balance valve. Based on the pilot pressure and the characteristics of the solenoid valve, the controller determines the control current to be input to the solenoid valve, and inputs the corresponding control current to control the boom to rotate at an angular velocity ω. This invention's engineering machinery control method achieves uniform boom lowering by controlling the valve core opening of the balance valve, avoiding significant hydraulic shock and thus preventing the deterioration of operating comfort caused by natural lowering.

Description

Technical Field

[0001] This invention relates to the field of hydraulic technology, and in particular to a control method, control system, and engineering machinery for construction machinery. Background Technology

[0002] In boom luffing operations of pump trucks, cranes, and aerial work platforms, hydraulic cylinders are typically used to drive the boom's luffing motion. During boom lowering, the boom's working angle is generally changed by its own weight; this working angle refers to the angle between the boom and the horizontal plane. During lowering, the gravitational torque exerted on the hydraulic cylinder varies depending on the boom's lowering angle; the smaller the angle between the boom and the horizontal plane, the greater the torque on the cylinder. Near the end of the lowering process (especially when the boom is fully extended), the boom's angular velocity becomes excessive, leading to significant changes in the hydraulic cylinder load and causing hydraulic shock. This hydraulic shock results in poor operator comfort. Summary of the Invention

[0003] This invention provides a control method, control system, and engineering machinery for construction machinery, in order to solve the problem in the prior art that hydraulic shock occurs when the boom naturally drops near the end of the drop, resulting in poor operating comfort.

[0004] This invention provides a control method for construction machinery, which includes a boom and a hydraulic cylinder connected to the boom. The control method comprises the following steps: inputting the desired boom rotation angular velocity ω; the controller acquiring the current angle parameter θ of the boom; and the controller acquiring the theoretical flow rate Q of the hydraulic cylinder exiting the rodless chamber based on the angular velocity ω and the angle parameter θ. 缸 That is, the flow rate Q through the balancing valve 缸 The controller obtains the pressure difference ΔP across the balancing valve; based on the flow rate Q passing through the balancing valve... 缸 The differential pressure ΔP is used to obtain the pilot pressure of the balance valve. The controller determines the control current to be input to the solenoid valve based on the pilot pressure and the characteristics of the solenoid valve, and inputs the corresponding control current to the solenoid valve to control the boom to rotate at an angular velocity ω.

[0005] According to the present invention, a control method for engineering machinery is provided, wherein the flow rate Q flowing through the balancing valve is... 缸 The step of obtaining the pilot pressure of the balancing valve based on the pressure difference ΔP further includes: determining the flow rate Q through the balancing valve. 缸 After obtaining the pressure difference ΔP, the pilot pressure of the balancing valve is obtained by interpolation.

[0006] According to a control method for engineering machinery provided by the present invention, the step after the controller acquires the pressure difference ΔP across the balance valve further includes: selecting a characteristic curve of the balance valve at a pre-measured temperature based on the temperature in the hydraulic circuit; and then, based on the characteristic curve of the balance valve at the corresponding temperature, determining the flow rate Q through the balance valve...缸 The pressure difference ΔP is used to obtain the pilot pressure of the balancing valve.

[0007] A control method for engineering machinery according to the present invention includes: inputting a desired constant speed of the boom end in the vertical direction; obtaining a desired boom rotation angular velocity ω based on the desired constant speed; obtaining the current angle parameter θ of the boom based on the desired boom rotation angular velocity ω and the controller; and obtaining the theoretical flow rate Q of the hydraulic cylinder exiting the rodless chamber based on the angular velocity ω and the angle parameter θ. 缸 The controller obtains the pressure difference ΔP across the balancing valve; based on the flow rate Q passing through the balancing valve... 缸 The differential pressure ΔP is used to obtain the pilot pressure of the balancing valve. The controller determines the control current to be input to the solenoid valve based on the pilot pressure and the characteristics of the solenoid valve, and inputs the corresponding control current to the solenoid valve to achieve the desired constant speed drop of the boom end.

[0008] According to the present invention, a control method for engineering machinery includes: in the step of inputting the desired boom rotation angular velocity ω and the controller obtaining the current angle parameter θ of the boom, the angular velocity ω is a constant value, thereby controlling the boom to rotate at a constant angular velocity.

[0009] This invention also provides a control system for engineering machinery, comprising: a hydraulic cylinder, wherein the rod chamber of the hydraulic cylinder is connected to a first oil tank via a first oil circuit, and the rodless chamber of the hydraulic cylinder is connected to the first oil tank via a second oil circuit, wherein a hydraulic pump is provided on the second oil circuit; a balance valve, wherein the balance valve is provided on the second oil circuit, the balance valve including a first directional valve having different working positions to realize oil inlet or outlet of the rodless chamber of the hydraulic cylinder; a solenoid valve, wherein the solenoid valve is connected to the pilot end of the balance valve, and the input end of the solenoid valve is connected to a regulated oil source; a control valve group, wherein the control valve group is connected to the solenoid valve and the second oil circuit; multiple sensors, wherein the multiple sensors are used to detect multiple data of the hydraulic system; and a controller, wherein the controller determines the magnitude of the control current input to the solenoid valve based on the input data, thereby controlling the valve core opening of the balance valve.

[0010] According to a control system for engineering machinery provided by the present invention, the control valve group further includes: a pilot valve, the pilot valve being connected to the pilot end of the second directional valve; and a servo pump, the oil outlet of the servo pump being connected to the oil inlet of the pilot valve.

[0011] According to a control system for engineering machinery provided by the present invention, the plurality of sensors include: a pressure sensor disposed on the pilot valve, the pressure sensor being used to detect the pressure value of hydraulic oil passing through the pilot valve; a plurality of displacement sensors disposed on the boom, the displacement sensors being used to detect the boom length; and a plurality of angle sensors disposed on the boom, the angle sensors being used to detect the boom angle.

[0012] According to the control system of engineering machinery provided by the present invention, the plurality of sensors further include: a temperature sensor, used to detect the temperature of hydraulic oil in the control system and input the measured data into the controller.

[0013] The present invention also provides an engineering machinery, including a vehicle body and a boom mounted on the vehicle body, characterized in that it further includes a control system of the engineering machinery as described above, for controlling the boom to rotate at a constant angular velocity or the boom end to rotate at a constant speed in the vertical direction.

[0014] The control method for construction machinery provided by this invention can calculate the input current value of the solenoid valve based on the hydraulic oil flow rate required by the rodless chamber of the cylinder when the boom is lowered, thereby controlling the valve core opening of the balance valve, realizing uniform boom lowering, avoiding large hydraulic shock, and thus avoiding the problem of reduced operating comfort caused by natural lowering. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a structural diagram of the crane when it is lifting its wings;

[0017] Figure 2 This is a structural diagram of the crane lowering its boom.

[0018] Figure 3 This is a schematic diagram of the control system for engineering machinery provided by the present invention;

[0019] Figure 4 It is a diagram showing multiple data points for the boom and hydraulic cylinders;

[0020] Figure 5 This is a graph showing the existing trend of boom angular velocity variation;

[0021] Figure 6 This is the characteristic curve of the balancing valve;

[0022] Figure 7 It is a flow curve of hydraulic oil at different temperatures in the balance valve;

[0023] Figure label:

[0024] 10: Hydraulic cylinder; 20: Balance valve; 21: Throttle valve; 22: First check valve; 23: Second check valve; 30: Solenoid valve; 40: Second directional valve; 50: Pilot valve; 61: Servo pump; 62: Hydraulic pump; 70: Relief valve; 81: First oil tank; 82: Second oil tank; 90: Pressure sensor; 100: Controller. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0026] The terms "first" and "second" in the specification and claims of this invention may explicitly or implicitly include one or more of those features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0027] On construction machinery, the boom is mounted on the vehicle body, and the movement of the vehicle body drives the movement of the boom. For example, a concrete pump truck folds its multi-section boom and places it on top of the vehicle body. Aerial work platforms retract their boom sections by folding them together, and then lower them onto the vehicle body.

[0028] like Figure 1 and Figure 2 As shown, this invention uses a crane as an example. The boom length is variable, achieved through the extension and retraction of multiple boom sections. The base of the boom is connected to the vehicle body via a pin, and the hydraulic cylinder 10 is connected between the hydraulic cylinder hinge point below the boom and the hydraulic cylinder hinge point on the vehicle body. During operation, the boom's luffing is achieved through the extension and retraction of the hydraulic cylinder 10. That is, the angle between the boom and the horizontal plane changes through the extension and retraction of the hydraulic cylinder 10. In this invention, this angle gradually increases during the lifting process and gradually decreases during the lowering process.

[0029] Because the base of the boom is hinged to the vehicle body, and both ends of the hydraulic cylinder 10 are hinged to the boom and the vehicle body respectively, during the natural lowering of the boom (without active control of the hydraulic system of the hydraulic cylinder 10), the weight of the boom applies a force to one end of the hydraulic cylinder 10, causing the cylinder 10 to shorten and rotate simultaneously, thus gradually reducing the angle between the boom and the horizontal plane. During the natural lowering, the experimental results are used to plot the following... Figure 5The boom angular velocity trend graph shows that as time progresses, the boom angular velocity first gradually increases and then gradually decreases. However, near the end of the descent (when the angular velocity becomes 0), the angular velocity gradually increases and then decreases sharply. This phenomenon is caused by the drastic load change on cylinder 10 during the descent, resulting in impact on the hydraulic system. To avoid this impact, the boom can be controlled to descent at a constant angular velocity.

[0030] Therefore, a hydraulic system should be designed. For example... Figure 3 As shown, the hydraulic system includes a cylinder 10, inside which is a piston. One end of the piston is connected to a rod, and the other end of the rod extends outward through the top of the cylinder. The piston divides the interior of the cylinder 10 into a rod chamber (between the side of the piston with the rod and the inner wall of the cylinder 10) and a rodless chamber. In this hydraulic control system, the rod chamber of the cylinder 10 is connected to a first oil tank 81 via a first oil passage, and the rodless chamber is connected to the first oil tank 81 via a second oil passage. A hydraulic pump 62 is installed on the second oil passage, which pumps hydraulic oil to the rodless chamber of the cylinder 10, causing the hydraulic oil in the rod chamber to flow into the first oil tank 81 through the first oil passage, thereby extending the rod of the cylinder 10 and achieving boom raising. During lowering, the hydraulic oil in the rodless chamber of the cylinder 10 flows out, causing a negative pressure in the rod chamber of the cylinder 10, which causes the rod chamber of the cylinder 10 to draw hydraulic oil from the first oil tank 81 through the first oil passage. To protect the safety of the hydraulic system, the maximum pressure of the hydraulic system can be limited. That is, an relief valve (not shown in the figure) is installed at the outlet of the hydraulic pump 62, and the pressure in the second oil circuit is limited by the relief valve.

[0031] When the boom lowers, as the rod of cylinder 10 moves inward, a balance valve 20 is installed in the second oil circuit to control the flow rate of hydraulic oil out of the rodless chamber of cylinder 10. Specifically, the balance valve 20 includes a first directional valve, which comprises a throttle valve 21 and a first check valve 22. The throttle valve 21 and the first check valve 22 are located in different working positions of the first directional valve. During boom raising, the first check valve 22 can be activated, allowing hydraulic oil pumped by hydraulic pump 62 to enter the rodless chamber of cylinder 10 through the second oil circuit. The throttle valve 21 can also be activated to control the flow rate and velocity of the hydraulic oil flowing into the rodless chamber. During boom lowering, the first directional valve switches to the working position of the throttle valve 21, and the hydraulic oil flowing out of the rodless chamber passes through the throttle valve 21 into the first oil tank 81. The switching of the working positions of the throttle valve 21 and the first check valve 22 within the first directional valve is achieved through the interaction of pilot pressure and spring. By changing the magnitude of the pilot pressure while keeping the spring force acting on the valve core constant, the position of the valve core of the first directional valve can be changed. During the lowering of the span, the flow rate of hydraulic oil through the throttle valve 21 is controlled by changing the position of the valve core of the first directional valve.

[0032] The pilot pressure is formed by hydraulic oil acting on the pilot end of the first directional valve. The pilot end of the first directional valve is connected to the outlet of the servo pump 61. Further, to control the pilot pressure of the first directional valve, a solenoid valve 30 is provided between the servo pump 61 and the pilot end of the first directional valve. For ease of control, this solenoid valve 30 can be an electro-proportional valve. The solenoid valve 30 is electrically connected to the controller 100. The controller 100 inputs a control signal to the solenoid valve 30, and the solenoid valve 30 adjusts the hydraulic oil flow through the solenoid valve 30 in response to the control signal. This control signal controls the valve spool position of the solenoid valve 30, thereby controlling the pilot pressure at the pilot end of the first directional valve, thus adjusting the valve spool position of the first directional valve and changing the flow rate through the first directional valve. That is, during the swing cut, the solenoid valve 30 changes the hydraulic oil flow rate through the balance valve 20.

[0033] Changing the hydraulic oil flow rate of the balance valve 20 can thus adjust the movement speed of the piston and cylinder rod within the cylinder 10. Figure 1 , Figure 2 It can be seen that the cylinder rod of the hydraulic cylinder 10 is connected to the boom, and the movement speed of the cylinder rod in the hydraulic cylinder 10 will affect the speed of the boom when it is lowered, which is hinged to the cylinder rod.

[0034] Additionally, the outlet of the servo pump 61 is connected to a pressure-limiting relief valve 70, through which a portion of the hydraulic oil pumped by the servo pump 61 can be directed into the second oil tank 82. The first oil tank 81 and the second oil tank 82 can be the same oil tank.

[0035] Furthermore, in order to increase the variation range of hydraulic oil through the balance valve 20, a second check valve 23 is set in the second oil circuit. The second check valve 23 is connected in parallel with the first directional valve. The hydraulic oil pumped out by the hydraulic pump 62 can enter the rodless chamber of the cylinder 10 through the first check valve 22 and the second check valve 23.

[0036] Furthermore, to control the flow rate and velocity of the hydraulic oil in the second oil circuit between the hydraulic pump 62 and the rodless chamber of the cylinder 10, a second directional valve 40 is installed in this oil circuit. By controlling the position of the valve core within the second directional valve 40, the flow rate and velocity of the hydraulic oil passing through the second directional valve 40 can be controlled. This second directional valve 40 has multiple working positions. In one of these working positions, the hydraulic oil flowing out of the rodless chamber of the cylinder 10 can directly enter the first oil tank 81 without passing through the hydraulic pump 62.

[0037] Furthermore, a pilot valve 50 is connected between the pilot ends on both sides of the second directional valve 40 and the servo pump 61. The pilot valve 50 is connected to an operating handle, which can move left and right (from the driver's left and right when seated in the cab). The left and right directions of the operating handle correspond to the pilot ends on both sides of the second directional valve 40. If the operating handle moves to the left, the oil circuit between the servo pump 61 and the pilot end on the left side of the second directional valve 40 is opened, thereby controlling the movement of the valve core in the second directional valve 40. The amplitude and direction of the operating handle movement will correspondingly cause a pressure change between the pilot valve 50 and the pilot end of the second directional valve 40, that is, the operator's action information is converted into pressure change information. Normally, the handle is in the neutral position. This operating handle can be installed in the cab on the vehicle body.

[0038] Furthermore, in order to monitor the pressure change in the oil circuit between the pilot valve 50 and the pilot end of the second directional valve 40 in real time, a pressure sensor 90 is provided here, which can display the pressure of the oil circuit in real time.

[0039] When the increase is, such as Figure 3 As shown, hydraulic pump 62 pumps oil from the first oil tank 81, and the second directional valve 40 switches to the right position. The hydraulic oil passes through the first check valve 22 and / or the second check valve 23 in the balance valve 20 and is pumped into the cylinder 10, ultimately controlling the extension of the cylinder rod in the cylinder 10. From the above analysis, it can be seen that when the boom is raised, the speed of the boom is controlled by the displacement and rotational speed of the hydraulic pump 62.

[0040] During boom descent, when pilot valve 50 is opened, pressure sensor 90 transmits the detected pressure value to controller 100. This pressure value corresponds to the opening degree of the operating handle. A larger opening degree results in a faster boom descent speed, while a smaller opening degree results in a slower descent speed. With a fixed boom length, the handle opening degree is positively correlated with the boom's angular velocity. A boom length sensor is installed on the boom to monitor its length. This boom length sensor could be a displacement sensor.

[0041] An angle sensor is installed on the boom to transmit the detected boom angle (the angle between the boom and the horizontal plane) to the controller 100. The angular velocity of the boom can be calculated using the angle sensor. Then, by inputting the boom rotation angular velocity, the geometric parameters of the cylinder 10 (the cross-sectional diameter of the cylinder), and the boom angle to the controller 100, the theoretical rodless chamber flow rate of the current cylinder 10 can be calculated. The current rodless chamber flow rate of the current cylinder 10 refers to the flow rate through the rodless chamber, or the flow rate of hydraulic oil flowing from the rodless chamber into the first oil tank 81 through the balance valve 20.

[0042] The control system for construction machinery provided in this embodiment of the invention eliminates the phenomenon of mismatch in hydraulic cylinder balance flow and achieves constant angular velocity boom lowering.

[0043] A pressure sensor (not shown in the figure) is installed between the balance valve 20 and the oil cylinder 10, and a pressure sensor (not shown in the figure) is installed between the balance valve 20 and the first directional valve 40. The pressure difference ΔP between the front and rear of the balance valve 20 can be calculated by calculating the difference between the pressure sensor before the valve and the pressure sensor after the valve.

[0044] The existing balance valve control method involves directly inputting control current into the solenoid valve 30 via the handle, thereby controlling the valve core opening of the solenoid valve 30 and subsequently controlling the flow rate through the balance valve 20, i.e., the rodless chamber flow rate. The boom lowering speed is controlled by controlling the flow rate through the balance valve 20. Ideally, as the boom lowers to a stop, the operating handle opening decreases (the operating handle gradually approaches the neutral position), and the boom angular velocity decreases accordingly. However, with this control method, during the lowering process, especially as the boom approaches a stop, the angular velocity rapidly increases and then quickly decreases to zero. This change in angular velocity causes a noticeable impact on the operator, resulting in a poor operating experience. Direct factors contributing to this phenomenon include the boom's own weight, the load on the hook, the boom length, and the hydraulic oil temperature. Operators need to consider these factors before inputting control current into the solenoid valve 30 via the operating handle. However, experienced operators often operate based on practical experience, overlooking one or more factors, leading to a poor control experience. Operators without experience will have a worse experience with control.

[0045] The control system for construction machinery provided by this invention, by setting up solenoid valves, balance valves, control valve groups, multiple sensors and controllers, can calculate the input current value of the solenoid valve based on the hydraulic oil flow rate from the rodless chamber of the cylinder when the boom is lowered, thereby controlling the valve core opening of the balance valve, realizing uniform boom lowering, avoiding large hydraulic shocks, and thus avoiding the problem of reduced operating comfort caused by natural lowering.

[0046] This invention also provides a control method for engineering machinery, specifically including the following steps:

[0047] Step 01: Input the desired boom rotation angular velocity ω, and the controller obtains the current boom angle parameter θ; Step 02: The controller obtains the theoretical flow rate Q of the hydraulic cylinder exiting the rodless chamber based on the angular velocity ω and the angle parameter θ. 缸 That is, the flow rate Q through the balancing valve 缸 Step 03: The controller obtains the pressure difference ΔP across the balancing valve; Step 04: Based on the flow rate Q flowing through the balancing valve... 缸 1. Pressure difference ΔP, obtain the pilot pressure of the balance valve; Step 05: The controller determines the control current to be input to the solenoid valve based on the pilot pressure and the characteristics of the solenoid valve, and inputs the corresponding control current to the solenoid valve to control the boom to rotate at an angular velocity ω.

[0048] Now Figure 1 , Figure 2 The hydraulic cylinders, the hinge points between the boom and the vehicle body, and the connection points between the hydraulic cylinders and the boom in the construction machinery are simplified as follows: Figure 4 The model is described below. In this model, the length of the line connecting the hinge point between the boom and the vehicle body and the hinge point between the cylinder and the vehicle body is set as b (a constant), the real-time length of the boom is set as f, the real-time length of the cylinder 10 is set as a, the distance between the hinge point of the cylinder 10 and the boom and the hinge point of the boom and the vehicle body is set as c (a constant), the angle between the boom and the cylinder 10 is α, the angle between the cylinder 10 and the boom hinge point perpendicular to the boom direction and the cylinder 10 is set as β, the angle between the boom and the horizontal plane is set as ψ, and the angle between b and c is set as θ.

[0049] This invention differs from existing technologies by directly inputting the expected angular velocity value ω to the controller 100. The angle between ψ and the horizontal plane is measured in real time by an angle sensor; since the angle is constant, the angle θ between the boom and the line connecting them can be obtained in real time. The velocity V1 at the hinge point between the cylinder 10 and the boom is V1 = ω·c. And V 缸 =V1·cos(β)=V1·sin(α), that is, sin(α)=b·sin(θ) / a. According to the cosine theorem, the real-time length of cylinder 10 is... Thus,

[0050]

[0051] The flow rate Q of the rodless chamber of cylinder 10 缸 =V 缸 • A (where A is the cross-sectional area of ​​the hydraulic cylinder, which is a constant), i.e., the theoretical flow rate Q of the rodless chamber. 缸 The flow rate through the balancing valve can be determined based on the real-time included angle θ and the input expected angular velocity value ω.

[0052] The pressure difference ΔP detected by the upstream pressure sensor and the downstream pressure sensor is input to the controller 100 to obtain the characteristic curve of the balancing valve 20 in advance. This characteristic curve is as follows: Figure 6 As shown. Figure 6 The curve contains multiple lines representing the relationship between the flow rate and differential pressure of the balancing valve under pilot pressure. However, the pre-measured data is limited and cannot include all data. When the flow rate Q of the balancing valve is determined... 缸 After the pressure difference ΔP, the coordinate point may fall between two curves. Therefore, the interpolation method is used between two adjacent curves to determine the pilot pressure, so as to reduce the error between the obtained pilot pressure and the actual pilot pressure and improve the accuracy.

[0053] The characteristic curve can be used to determine the theoretical flow rate Q of the rodless cavity at a given pressure difference ΔP and a given value. 缸The pilot pressure at the pilot end of the lower balance valve 20. Based on the pre-obtained correspondence between the pilot pressure of the balance valve 20 and the control current of the solenoid valve 30, the current input to the controller 100 can be adjusted. The included angle θ can be measured in real time by the angle sensor on the boom and input to the controller. The pressure difference ΔP can be measured in real time by the pressure sensors set before and after the balance valve 20. Therefore, based on the boom rotation, the real-time pressure required at the pilot end of the balance valve 20 can be obtained, and the current input to the solenoid valve 30 can be adjusted according to the real-time pressure. This reduces the operator's intervention and judgment process, thereby reducing the possibility of human error and improving the operability of the hydraulic control system. At the same time, it can be seen from the above formula derivation process that the direct factors affecting the boom speed control, such as the boom length, hook load, and boom self-weight, are transformed into the fundamental influencing factors, namely the real-time included angle θ of the boom and the input expected angular velocity value ω.

[0054] Controller 100 receives the theoretical Q input 缸 The pilot pressure at the pilot end of the balance valve 20 is determined by looking up a table (for the rodless chamber flow rate and pressure difference ΔP). The pilot pressure at the pilot end of the balance valve 20 corresponds to the current input to the solenoid valve 30 by the controller 100. If the solenoid valve 30 is an electro-proportional pressure reducing valve, the correspondence between the pilot pressure and the input current can be derived based on the characteristics of the electro-proportional pressure reducing valve.

[0055] Furthermore, an oil temperature sensor is installed in the oil circuit between the rodless chamber and the balance valve 20. Figure 3 (Not shown), this oil temperature sensor detects the temperature of the hydraulic oil in the oil circuit. In actual use, the temperature of the hydraulic oil in the hydraulic control system will rise. Changes in hydraulic oil temperature affect its viscosity; higher temperatures decrease the viscosity. The characteristics of the balance valve 20 were tested beforehand at different temperatures, such as a first preset temperature and a second preset temperature. The test data are shown below. Figure 7 As a result, the balancing valve 20 is significantly affected by temperature changes. Optionally, in this embodiment, the first preset temperature is 30°C and the second preset temperature is 50°C.

[0056] Therefore, the balance valve 20 was tested at different temperatures beforehand, and multiple results were obtained. Figure 6 When actually looking up the corresponding table, first use the temperature of the hydraulic oil detected by the temperature sensor to lock multiple tables. Figure 6The process involves taking one of the following parameters: ΔP (measured in real-time) and the theoretical flow rate of the rodless chamber (flow through the balance valve 20). Then, based on this measured ΔP and the theoretical flow rate through the rodless chamber (flow through the balance valve 20), the corresponding pilot pressure at the pilot end of the balance valve 20 is determined. Based on the pre-measured relationship between the control current input from the controller 100 to the solenoid valve 30 and the change in pressure at the pilot end of the balance valve 20, the required control current for the solenoid valve 30 is obtained. This process takes temperature into account during the acquisition of the control current, thus avoiding the impact of temperature changes on the boom rotation speed at the same handle opening.

[0057] Furthermore, this invention enables constant angular velocity rotation of the boom. Simply inputting the desired angular velocity value ω to the controller via the handle's opening allows the boom to rotate at the desired angular velocity ω. Of course, the desired angular velocity value ω input to the controller can also be adjusted in stages as needed to achieve variable angular velocity rotation of the boom.

[0058] Furthermore, this invention enables the boom head to drop at a constant speed in the vertical direction. According to V 臂 =V·cosψ=ω·f·cosψ, from which we can derive ω=V 臂 / f·cosψ. That is, to achieve a constant vertical drop amplitude of the boom tip, calculate the real-time ω. Then, based on Q... 缸 =V 缸 ·A, and

[0059]

[0060] At a certain temperature, the controller 100 operates at the desired V. 臂 Under constant conditions, the Q of the balance valve 20 can be calculated. 缸 Then, based on the characteristic table of the pre-obtained balance valve 20, the pilot pressure at the pilot end of the balance valve 20 is found, and the current that the controller 100 needs to input to the solenoid valve 30 is obtained.

[0061] Furthermore, by controlling the flow of Q through the balancing valve 20 缸 When the boom is lowered to near a stop, the boom angular velocity will not change abruptly, thus not reducing the operator's experience.

[0062] This invention also provides an engineering machine, including a vehicle body, a boom mounted on the vehicle body, and a control system for the engineering machine to control the boom to rotate at a constant angular velocity or the boom end to rotate at a constant speed in the vertical direction.

[0063] The engineering machinery provided in this embodiment of the invention can precisely control the boom lowering speed during boom lowering operations, avoiding the problem of hydraulic shock occurring when the boom is about to stop, which would lead to a decrease in operating comfort.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A control method for construction machinery, the construction machinery having a boom and a hydraulic cylinder connected to the boom, characterized in that, The control method is carried out according to the following steps: Input the desired boom rotation angular velocity ω, and the controller obtains the current boom angle parameter θ; The controller obtains the theoretical flow rate Q of the rodless chamber from the hydraulic cylinder based on the angular velocity ω and the angle parameter θ. 缸 That is, the flow rate Q through the balancing valve 缸 ; The controller acquires the pressure difference ΔP across the balancing valve and inputs the pressure difference ΔP to the controller to obtain the characteristic diagram of the balancing valve; According to the flow rate Q through the balancing valve 缸 The pilot pressure of the balance valve is obtained by considering the pressure difference ΔP and the characteristic diagram of the balance valve. Based on the correspondence between the pilot pressure and the control current of the solenoid valve, the control current to be input to the solenoid valve is determined, and the corresponding control current is input to the solenoid valve to control the boom to rotate at an angular velocity ω. Input the desired constant vertical speed at the boom tip; Based on the desired constant speed, obtain the desired boom rotation angular velocity ω; The boom's current angle parameter θ is obtained based on the desired boom rotation angular velocity ω and the controller. The controller obtains the theoretical flow rate Q of the rodless chamber from the hydraulic cylinder based on the angular velocity ω and the angle parameter θ. 缸 ; The controller obtains the pressure difference ΔP across the balancing valve; According to the flow rate Q through the balancing valve 缸 The pressure difference ΔP is used to obtain the pilot pressure of the balancing valve; The controller determines the control current to be input to the solenoid valve based on the pilot pressure and the characteristics of the solenoid valve, and inputs the corresponding control current to the solenoid valve to control the boom end to drop at the desired constant speed.

2. The control method for engineering machinery according to claim 1, characterized in that, The flow rate Q flowing through the balancing valve is... 缸 The step of obtaining the pilot pressure of the balancing valve based on the pressure difference ΔP further includes: Determine the flow rate Q through the balancing valve 缸 After obtaining the pressure difference ΔP, the pilot pressure of the balancing valve is obtained by interpolation.

3. The control method for engineering machinery according to claim 1, characterized in that, The steps following the controller acquiring the pressure difference ΔP across the balance valve also include: Based on the temperature in the hydraulic circuit, select the characteristic diagram of the balance valve at the corresponding temperature that was measured in advance; Based on the characteristic diagram of the balancing valve at the corresponding temperature, and then according to the flow rate through the balancing valve... Q 缸 The pressure difference ΔP is used to obtain the pilot pressure of the balancing valve.

4. The control method for engineering machinery according to claim 1, characterized in that, include: The angular velocity ω in the steps of inputting the desired boom rotation angular velocity ω and the controller obtaining the current angle parameter θ of the boom is a constant value, so as to control the boom to rotate at a constant angular velocity.

5. A control system for engineering machinery implementing the control method for engineering machinery according to any one of claims 1-4, characterized in that, include: The hydraulic cylinder has a rod chamber connected to a first oil tank via a first oil passage, and a rodless chamber connected to the first oil tank via a second oil passage, wherein a hydraulic pump is provided on the second oil passage. A balance valve is provided in the second oil circuit. The balance valve includes a first directional valve, which has different working positions to realize oil inlet or return to the rodless chamber of the oil cylinder. A solenoid valve is connected to the pilot end of the balance valve, and a pressure-stabilizing oil source is connected to the input end of the solenoid valve. A control valve assembly, which is connected to the solenoid valve and the second oil circuit; Multiple sensors, wherein the multiple sensors are used to detect multiple data of the hydraulic system; The controller determines the magnitude of the control current input to the solenoid valve based on the input data, and then controls the valve core opening of the balance valve.

6. The control system for engineering machinery according to claim 5, characterized in that, The control valve assembly also includes: A pilot valve, wherein the pilot valve is connected to the pilot end of the second directional valve; A servo pump, wherein the oil outlet of the servo pump is connected to the oil inlet of the pilot valve.

7. The control system for engineering machinery according to claim 5, characterized in that, The plurality of said sensors include: A pressure sensor is disposed on the pilot valve and is used to detect the pressure value of the hydraulic oil passing through the pilot valve; Multiple displacement sensors are mounted on the boom and are used to detect the boom length. Multiple angle sensors are disposed on the boom and are used to detect the boom angle.

8. The control system for engineering machinery according to claim 7, characterized in that, The plurality of said sensors also include: Temperature sensors are used to detect the temperature of the hydraulic oil in the control system and input the measured data into the controller.

9. An engineering machine, comprising a vehicle body and a boom mounted on the vehicle body, characterized in that, It also includes a control system for the engineering machinery according to any one of claims 5 to 8, for controlling the boom to rotate at a constant angular velocity or the boom end to rotate at a constant speed in the vertical direction.

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