A robot hydraulic rotary joint control system and control method

Abstract

The application discloses a kind of robot hydraulic rotary joint control system and control method, system includes: hydraulic rotary joint;Position feedback unit is set to hydraulic rotary joint;First electromagnetic switch valve and second electromagnetic switch valve;Direct current motor;Fixed displacement bidirectional plunger pump;Pressure tank;Proportional relief valve;Controller, including four respectively with direct current motor, first pressure feedback unit, second pressure feedback unit, position feedback unit connection control signal input, and four respectively with direct current motor, proportional relief valve, first electromagnetic switch valve, second electromagnetic switch valve connection control signal output;Host computer is connected with controller.The application is connected with the independent two electromagnetic switch valves of hydraulic rotary joint, module decoupling, control coordination, maintenance cost is dominant.

Description

TECHNICAL FIELD

[0001] The present application relates to a robot hydraulic rotary joint control system and a control method. BACKGROUND

[0002] Hydraulic rotary joint is a commonly used joint in robots, which is widely used in various industrial robots and mechanical arms due to its advantages of high load bearing, high power density, light weight, etc. The hydraulic rotary joint generates vibration and impact during movement, and is affected by load fluctuation and load change during static holding, which reduces the motion accuracy and service life of the robot. The traditional flow position control method is difficult to meet the requirements of good load bearing capacity and stable operation. Therefore, it is necessary to develop a new hydraulic rotary joint control system and its control method.

[0003] The prior art has made corresponding improvements in the structure design and control method of the hydraulic rotary joint, and the solution to the smooth operation is mainly based on closed-loop control strategy and its improvement method. The pressure inside the hydraulic rotary joint is one of the important factors affecting the operation state and load bearing capacity of the hydraulic rotary joint. The size of the pressure inside the hydraulic rotary joint is related to the flow and pressure change in the hydraulic system. If the pressure is insufficient, the joint may lose stability; if the pressure is too high, the system loss may increase. The prior art does not provide a good system design and control strategy for independent oil port setting, angle position control and load fluctuation resistance after positioning. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provide a robot hydraulic rotary joint control system and a control method.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] In a first aspect of the present application, a robot hydraulic rotary joint control system is provided, comprising:

[0007] A hydraulic rotary joint;

[0008] A position feedback unit is provided on the hydraulic rotary joint;

[0009] A first electromagnetic on-off valve and a second electromagnetic on-off valve are respectively connected to a first inlet and return port of the hydraulic rotary joint and a second inlet and return port of the hydraulic rotary joint, and a first pressure feedback unit is further provided on the first inlet and return port of the hydraulic rotary joint, and a second pressure feedback unit is further provided on the second inlet and return port of the hydraulic rotary joint;

[0010] A DC motor;

[0011] The constant displacement bidirectional plunger pump is connected with the direct current motor, the first inlet and return port of the constant displacement bidirectional plunger pump is connected with the first electromagnetic switch valve, and the second inlet and return port of the constant displacement bidirectional plunger pump is connected with the second electromagnetic switch valve;

[0012] The constant displacement bidirectional plunger pump is connected with the direct current motor, the first inlet and return port of the constant displacement bidirectional plunger pump is connected with the first electromagnetic switch valve, and the second inlet and return port of the constant displacement bidirectional plunger pump is connected with the second electromagnetic switch valve;

[0013] The constant displacement bidirectional plunger pump is connected with the direct current motor, the first inlet and return port of the constant displacement bidirectional plunger pump is connected with the first electromagnetic switch valve, and the second inlet and return port of the constant displacement bidirectional plunger pump is connected with the second electromagnetic switch valve;

[0014] The constant displacement bidirectional plunger pump is connected with the direct current motor, the first inlet and return port of the constant displacement bidirectional plunger pump is connected with the first electromagnetic switch valve, and the second inlet and return port of the constant displacement bidirectional plunger pump is connected with the second electromagnetic switch valve;

[0015] The constant displacement bidirectional plunger pump is connected with the direct current motor, the first inlet and return port of the constant displacement bidirectional plunger pump is connected with the first electromagnetic switch valve, and the second inlet and return port of the constant displacement bidirectional plunger pump is connected with the second electromagnetic switch valve;

[0016] Further, the controller further comprises a communication interface, and the controller is connected with the upper computer through the communication interface.

[0017] The second aspect of the application provides a control method of the robot hydraulic rotary joint control system, which comprises a hydraulic rotary joint rotation control step and a hydraulic rotary joint pressure maintaining control step performed in a position maintaining stage after the hydraulic rotary joint rotation control step is completed.

[0018] The static load acting section is judged, when the hydraulic rotary joint position is maintained, if the load is a vertical downward load inertia, the second inlet and return port of the hydraulic rotary joint is a positive load, at this time, the relief pressure setting value P of the proportional relief valve is set as the loop section pressure value P2 plus the pressure value upper offset value Pes, wherein the loop section pressure value P2 is obtained through the second pressure feedback unit, and the pressure value upper offset value Pes is _d Δp, Δp, is a gain coefficient, and Δp is a pressure difference, i.e., the pressure value of the first pressure feedback unit minus the pressure value of the second pressure feedback unit; when the hydraulic rotary joint position is maintained, if the load is a vertical upward load inertia, the opposite is set;

[0019] The electromagnetic switch valve of the positive load acting section is opened, and the electromagnetic switch valve of the negative load acting section remains closed, so that the constant displacement bidirectional plunger pump is communicated with the side of the positive load acting section electromagnetic switch valve as the oil return port to set the motor rotation direction; the closed loop control of the direct current motor, and the closed hydraulic circuit forms a local stable value under the action of the proportional overflow valve, and when the pressure feedback unit of the positive load acting section reaches the overflow pressure setting value P_ d , the electromagnetic switch valve of the positive load acting section is closed.

[0020] Further, the hydraulic rotary joint rotation control step includes the following sub-steps:

[0021] The controller receives the upper computer signal, including the target position information of the hydraulic rotary joint;

[0022] The controller reads the position feedback signal of the position feedback unit, compares it with the target position information to determine the rotation direction and angle of the hydraulic rotary joint, and forms a specific direction rotation instruction;

[0023] The controller outputs the specific direction rotation instruction to the direct current motor, proportional overflow valve, first electromagnetic switch valve and second electromagnetic switch valve respectively for control operation;

[0024] When the specific direction rotation instruction is a clockwise direction rotation instruction, the control operation includes: the constant displacement bidirectional plunger pump is driven to rotate by the direct current motor, the constant displacement bidirectional plunger pump is provided with oil source and initial pressure by the second one-way valve of the constant displacement bidirectional plunger pump through the second one-way valve of the constant displacement bidirectional plunger pump as the oil inlet, and the first inlet and outlet port of the constant displacement bidirectional plunger pump as the oil return port flows out fluid; the shuttle valve is opened at the first end and closed at the second end under the action of the oil path pressure, and the overflow pressure setting value of the proportional overflow valve acts on the path formed by the constant displacement bidirectional plunger pump and the first electromagnetic switch valve; the first electromagnetic switch valve and the second electromagnetic switch valve are opened, and the system oil path is the first inlet and outlet port of the constant displacement bidirectional plunger pump, the first electromagnetic switch valve, the first inlet and outlet port of the hydraulic rotary joint, the second inlet and outlet port of the hydraulic rotary joint, the second electromagnetic switch valve and the second inlet and outlet port of the constant displacement bidirectional plunger pump; when the specific direction rotation instruction is a counterclockwise direction rotation instruction, the operation is opposite;

[0025] When the position feedback signal of the position feedback unit is consistent with the target position information, the hydraulic rotary joint reaches the set target value, at this time the first electromagnetic switch valve and the second electromagnetic switch valve are closed at the same time through the controller, the hydraulic rotary joint stops rotating, and the position closed loop is completed.

[0026] Further, in the hydraulic rotary joint rotation control step, the overflow pressure setting value of the proportional overflow valve is set as the maximum protection pressure Pmax of the system.

[0027] Further, in the hydraulic rotary joint rotation control step, when the position of the hydraulic rotary joint is controlled by the outer loop, the inner loop is controlled by the rotation speed of the direct current motor at the same time, so that the hydraulic rotary joint runs at a smooth speed under different loads and output torques.

[0028] The present application has the following advantages:

[0029] (1) In an exemplary embodiment of the present application, two independent electromagnetic on-off valves (i.e., a first electromagnetic on-off valve and a second electromagnetic on-off valve) connected with the hydraulic rotary joint are adopted, the modules are decoupled, the control is coordinated, and the maintenance cost is optimal.

[0030] (2) In an exemplary embodiment of the present application, after the position control is completed, according to the control instruction requirement, the state control of the electromagnetic on-off valve and the setting of the proportional relief valve can modulate the positive load section pressure of the hydraulic rotary joint to improve the static stiffness of the joint system to adapt to the load fluctuation resistance, load bearing capacity and operation stability requirement in the working condition after rotation positioning such as lifting and grabbing.

[0031] (3) In an exemplary embodiment of the present application, double closed-loop control is adopted to realize the motion control stability and position accuracy under different output torque conditions. The functions of the bidirectional plunger pump and the electromagnetic on-off valve are fully utilized to realize the purpose of position control and pressure maintaining control through the closed-loop program. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A structural connection diagram of a robot hydraulic rotary joint control system provided in an exemplary embodiment of the present application is shown in the figure;

[0033] Figure 2 A flow chart of a control method of a robot hydraulic rotary joint control system provided in an exemplary embodiment of the present application is shown in the figure;

[0034] Figure 3 A flow chart of a hydraulic rotary joint pressure maintaining control step provided in an exemplary embodiment of the present application is shown in the figure;

[0035] Figure 4 A flow chart of a hydraulic rotary joint rotation control step provided in an exemplary embodiment of the present application is shown in the figure;

[0036] Figure 5 An inner-outer loop control schematic diagram of a hydraulic rotary joint rotation control step provided in an exemplary embodiment of the present application is shown in the figure;

[0037] In the figure, 1 - DC motor, 2 - fixed displacement bidirectional plunger pump, 3 - shuttle valve, 4 - proportional overflow valve, 5.1 - first electromagnetic on-off valve, 5.2 - first electromagnetic on-off valve, 6.1 - pressure feedback unit, 6.2 - pressure feedback unit, 7 - hydraulic rotary joint, 8 - position feedback unit, 9.1 - first check valve, 9.2 - second check valve, 10 - booster tank, 11 - controller. DETAILED DESCRIPTION

[0038] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0039] In the description of the present application, it should be noted that the directions or positional relationships indicated by "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like are described based on the directions or positional relationships described in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0040] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0041] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0042] Reference Figure 1 , Figure 1 A structural connection diagram of a robot hydraulic rotary joint control system provided by an exemplary embodiment of the present application is shown, which comprises:

[0043] Hydraulic rotary joint 7;

[0044] Position feedback unit 8 is arranged on hydraulic rotary joint 7;

[0045] The first electromagnetic switch valve 5.1 and the second electromagnetic switch valve 5.2 are connected with the first inlet and return port of the hydraulic rotary joint 7 and the second inlet and return port of the hydraulic rotary joint 7 respectively, and the first pressure feedback unit 6.1 is further arranged on the first inlet and return port of the hydraulic rotary joint 7, and the second pressure feedback unit 6.2 is further arranged on the second inlet and return port of the hydraulic rotary joint 7;

[0046] The direct current motor 1;

[0047] The constant-displacement bidirectional plunger pump 2, the driving end of the constant-displacement bidirectional plunger pump 2 is connected with the direct current motor 1, the first inlet and return port of the constant-displacement bidirectional plunger pump 2 is connected with the first electromagnetic switch valve 5.1, and the second inlet and return port of the constant-displacement bidirectional plunger pump 2 is connected with the second electromagnetic switch valve 5.2;

[0048] The pressurized oil tank 10 is connected with the first inlet and return port of the constant-displacement bidirectional plunger pump 2 through the first one-way valve 9.1 and is connected with the second inlet and return port of the constant-displacement bidirectional plunger pump 2 through the second one-way valve 9.2;

[0049] The proportional overflow valve 4 is connected with the first inlet and return port of the constant-displacement bidirectional plunger pump 2 through the first end of the shuttle valve 3 and is connected with the second inlet and return port of the constant-displacement bidirectional plunger pump 2 through the second end of the shuttle valve 3;

[0050] The controller 11 includes four control signal input ends connected with the direct current motor 1, the first pressure feedback unit 6.1, the second pressure feedback unit 6.2 and the position feedback unit 8 respectively and four control signal output ends connected with the direct current motor 1, the proportional overflow valve 4, the first electromagnetic switch valve 5.1 and the second electromagnetic switch valve 5.2 respectively;

[0051] The host computer is connected with the controller 11.

[0052] Specifically, in the example embodiment, two independent electromagnetic switch valves (i.e., the first electromagnetic switch valve 5.1 and the second electromagnetic switch valve 5.2) connected with the hydraulic rotary joint 7 are adopted, the modules are decoupled, the control is coordinated, and the maintenance cost is superior. In the prior art, a three-position four-way valve is adopted to realize the corresponding structure, and the flow and pressure of two oil ports cannot be independently controlled, which has disadvantages in module decoupling and maintenance cost.

[0053] More preferably, in an example embodiment, the controller 11 further includes a communication interface, and the controller 11 is connected with the host computer through the communication interface.

[0054] Specifically, in the example embodiment, the communication interface can be a wired communication interface or a wireless communication interface, which can be set according to actual requirements.

[0055] Referring to Figure 2 , Figure 2A flow chart of a control method of the robot hydraulic rotary joint control system is shown in another exemplary embodiment of the present application, including a hydraulic rotary joint rotation control step, a hydraulic rotary joint pressure maintaining control step executed in a position maintaining stage after the hydraulic rotary joint rotation control step is completed; as shown in the figure, the hydraulic rotary joint pressure maintaining control step includes the following sub-steps: Figure 3

[0056] When the hydraulic rotary joint 7 is in position maintaining, if the load is a vertical downward load inertia, the second inlet and outlet port of the hydraulic rotary joint 7 is a positive load, at this time, the relief pressure setting value P _d of the proportional relief valve 4 is set to be equal to the circuit segment pressure value P2 plus a pressure value offset value Pes, wherein the circuit segment pressure value P2 is obtained through the second pressure feedback unit 6.2, and the pressure value offset value Pes Δp, is a gain coefficient, and the Δp value is a pressure difference, i.e. the pressure value of the first pressure feedback unit 6.1 minus the pressure value of the second pressure feedback unit 6.2; when the hydraulic rotary joint 7 is in position maintaining, if the load is a vertical upward load inertia, the opposite is set;

[0057] The electromagnetic on-off valve of the positive load acting segment is opened, and the electromagnetic on-off valve of the negative load acting segment remains closed, to set the motor rotation direction of the side of the constant displacement bidirectional plunger pump 2 communicating with the positive load acting segment as a return port; the DC motor 1 is closed-loop controlled, and the closed hydraulic circuit forms a local stable value under the action of the proportional relief valve 4, when the pressure feedback unit of the positive load acting segment reaches the relief pressure setting value P d of the proportional relief valve 4, the electromagnetic on-off valve of the positive load acting segment is closed.

[0058] Specifically, in the present exemplary embodiment, the hydraulic rotary joint pressure maintaining control step is executed in the position maintaining stage after the instruction action of the hydraulic rotary joint rotation control step is completed, to improve the system static stiffness and resistance to load fluctuation and load change. In the hydraulic rotary joint pressure maintaining control step, the proportional relief valve 4 plays the role of electrically controlled amplitude and amplitude limiting, for example, set to 3 MPa, the constant displacement bidirectional plunger pump 2 and the increased circuit form a closed circuit, and the pressure rises under the driving of the DC motor 1, the circuit pressure reaches 3 MPa (the setting value of the proportional relief valve 4 is the positive load acting segment setting pressure value), at the same time, the proportional relief valve 4 plays the role of amplitude limiting, to prevent system overshoot; at the same time, the static stiffness is improved, to improve the system static resistance to load fluctuation and load change:

[0059] ​The anti-load capacity refers to the ability of the hydraulic rotary joint 7 to maintain stable rotation under the condition of bearing a certain load. The internal pressure of the hydraulic rotary joint is one of the important factors affecting the operating state and bearing capacity of the hydraulic rotary joint 7. The size of the internal pressure of the hydraulic rotary joint 7 is related to factors such as flow and pressure change in the hydraulic system. If the pressure is insufficient, the joint may lose stability; if the pressure is too high, the system loss may increase. There is a certain relationship between the internal pressure of the hydraulic rotary joint 7 and its bearing capacity, and the size of the internal pressure directly affects the operating stability and bearing capacity of the hydraulic rotary joint. Generally speaking, the pressures of the oil inlet section and the oil return section are generally different. When the hydraulic rotary joint is working normally, the pressure of the oil inlet section is higher than that of the oil return section, because the inlet section of the hydraulic rotary joint 7 transmits the pressure of the main pump, while the oil return section is affected by factors such as load, hydraulic valve, pipeline, etc., resulting in pressure loss. Moreover, the bearing capacity of the hydraulic rotary joint 7 is more related to the pressure of the oil return section, because the hydraulic rotary joint 7 is mainly affected by the pressure of the oil return section when bearing load, and the size of the pressure directly affects the key parameters such as output torque and rotational speed. If the pressure of the oil return section is insufficient, it will cause the hydraulic rotary joint to lose bearing capacity or stability to decrease; if the pressure of the oil return section is too high, it may damage the hydraulic rotary joint or other components of the hydraulic system.

[0060] Therefore, in the present exemplary embodiment, after the position control is completed, according to the demand of the control instruction, through the state control of the electromagnetic on-off valve and the setting of the proportional relief valve 4, the positive load section pressure of the hydraulic rotary joint 7 is modulated to increase the static stiffness of the joint system to adapt to the requirements of anti-load fluctuation, bearing capacity and operating stability in the working condition of load bearing change after rotation positioning such as lifting and grabbing. At the same time, since the control part connected by the hydraulic rotary joint 7 is two independent electromagnetic on-off valves (i.e. the first electromagnetic on-off valve 5.1 and the second electromagnetic on-off valve 5.2), the modules are decoupled, so as to realize the pressure maintaining control step of the hydraulic rotary joint. If the corresponding structure is realized by using the three-position four-way valve of the prior art, the step cannot be realized.

[0061] When the position of the hydraulic rotary joint 7 is maintained, if the load is a vertical downward load inertia, the second inlet and outlet of the hydraulic rotary joint 7 is taken as an example, at this time, the relief pressure setting value P _d of the proportional relief valve 4 is the loop section pressure value P2 plus the pressure value offset value Pes, wherein the loop section pressure value P2 is obtained by the second pressure feedback unit 6.2, and the pressure value offset value Pes Δp, is the gain coefficient, and Δp is the pressure difference, i.e. the pressure value of the first pressure feedback unit 6.1 minus the pressure value of the second pressure feedback unit 6.2.

[0062] Wherein, the setting of Pes should meet the mechanical system design: if the pressure of the positive load section is insufficient, it will lead to the loss of load-carrying capacity or the decline of stability of the hydraulic rotary joint 7; if the pressure of the positive load section is too high, it will possibly damage the hydraulic rotary joint 7 or other components of the hydraulic system. According to the positive correlation between the pressure difference Δp and the load, the Pes can be set according to the size of the Δp value (i.e. the pressure difference) to adapt to the load capacity. In the pressure maintaining control process, the proportional overflow valve 4 simultaneously plays the role of modulating the local loop pressure and preventing pressure overshoot.

[0063] The second electromagnetic on-off valve 5.2 of the positive load acting section is opened, and the first electromagnetic on-off valve 5.1 of the negative load acting section remains closed, so that the fixed displacement bidirectional plunger pump 2 is communicated with the second electromagnetic on-off valve 5.2 of the positive load acting section, and the side of the oil return port is set to the motor rotation direction. The direct current motor 1 is closed-loop controlled, and the closed hydraulic circuit forms a local stable value under the action of the proportional overflow valve 4. When the pressure value of the pressure feedback unit 6.2 of the positive load acting section reaches the set value P_d of the proportional overflow valve, the second electromagnetic on-off valve 5.2 of the positive load acting section is closed.

[0064] The static stiffness refers to the proportion of the force and torque respectively acting on the hydraulic rotary joint 7 to the corresponding displacement or angle generated when the hydraulic rotary joint 7 remains unchanged in position or angle. The static stiffness does not consider dynamic effects such as speed or acceleration.

[0065] The positive load refers to the load borne by the hydraulic motor, which is positive, i.e. the direction of the load is opposite to the rotation direction of the hydraulic motor. In the positive load case, the hydraulic motor has high efficiency.

[0066] The negative load refers to the load borne by the hydraulic motor, which is also negative, i.e. the direction of the load is the same as the rotation direction of the hydraulic motor. In the negative load case, the hydraulic motor has low efficiency.

[0067] After the first electromagnetic on-off valve 5.1 is closed, the hydraulic oil cannot flow out, and the position fluctuation is only caused by the relationship between the pressure difference and the position stiffness:

[0068] Δs = Δp × V / K_s

[0069] Wherein, Δs represents the change amount of the position, V is the displacement, and K_s represents the position stiffness of the hydraulic rotary joint. By setting a proper upper offset value Pes, the position control stability will not be affected.

[0070] Therefore, simple components are used to realize the reciprocating rotation position control of the hydraulic joint, and after the position is stabilized, a larger holding pressure can be provided in the positive load section to increase the static stiffness of the system, so as to adapt to the load fluctuation and load change after positioning.

[0071] More preferably, in an exemplary embodiment, as shown in Figure 4 The hydraulic rotary joint rotation control step includes the following sub-steps:

[0072] The controller 11 receives the host computer signal, including the target position information of the hydraulic rotary joint 7;

[0073] The controller 11 reads the position feedback signal of the position feedback unit 8, and determines the rotation direction and angle of the hydraulic rotary joint 7 by comparing with the target position information, to form a specific direction rotation instruction.

[0074] The controller 11 outputs the specific direction rotation instruction to the DC motor 1, the proportional relief valve 4, the first electromagnetic on-off valve 5.1, and the second electromagnetic on-off valve 5.2 respectively, and performs control operation.

[0075] When the specific direction rotation instruction is a clockwise rotation instruction, the control operation includes: the fixed displacement bi-directional plunger pump 2 is driven to rotate by the DC motor 1, the oil tank 10 provides oil source and initial pressure to the second inlet and return port of the fixed displacement bi-directional plunger pump 2 as the oil inlet through the second check valve 6.2, and the fluid flows out of the first inlet and return port of the fixed displacement bi-directional plunger pump 2 as the oil return port; the shuttle valve 3 is opened at the first end and closed at the second end under the action of the oil passage pressure, and the relief pressure setting value of the proportional relief valve 4 acts on the passage formed by the fixed displacement bi-directional plunger pump 2 and the first electromagnetic on-off valve 5.1; the first electromagnetic on-off valve 5.1 and the second electromagnetic on-off valve 5.2 are opened, and the system oil passage is the first inlet and return port of the fixed displacement bi-directional plunger pump 2, the first electromagnetic on-off valve 5.1, the first inlet and return port of the hydraulic rotary joint 7, the second inlet and return port of the hydraulic rotary joint 7, the second electromagnetic on-off valve 5.2, and the second inlet and return port of the fixed displacement bi-directional plunger pump 2; when the specific direction rotation instruction is a counterclockwise rotation instruction, the operation is reversed.

[0076] When the position feedback signal of the position feedback unit 8 is consistent with the target position information, the hydraulic rotary joint 7 reaches the set target value, at which time the first electromagnetic on-off valve 5.1 and the second electromagnetic on-off valve 5.2 are closed simultaneously by the controller 11, the hydraulic rotary joint 7 stops rotating, and the position closed loop is completed.

[0077] Specifically, in the present exemplary embodiment, the specific implementation of the hydraulic rotary joint 7 rotation control is disclosed.

[0078] More preferably, in an exemplary embodiment, in the hydraulic rotary joint rotation control step, the relief pressure setting value of the proportional relief valve 4 is set as the maximum protection pressure Pmax of the system.

[0079] Specifically, in the present exemplary embodiment, the opening proportional relief valve 4 is initially set to the system protection pressure Pmax, where the proportional relief valve 4 is used as a safety valve to set up the system safety.

[0080] More preferably, in an exemplary embodiment, as shown in FIG. 4, the hydraulic rotary joint is controlled by a proportional relief valve 4 and a proportional pressure valve 5. Figure 5 As shown in FIG. 5, in the hydraulic rotary joint rotation control step, when the position of the hydraulic rotary joint is controlled by the outer loop, the speed of the DC motor is simultaneously controlled by the inner loop, so that the hydraulic rotary joint runs at a smooth speed under different loads and output torques.

[0081] Specifically, in the present exemplary embodiment, the relationship between the hydraulic rotary joint inlet and outlet pressures and the load can be described by the following formula:

[0082] Flow formula: Q = V x n

[0083] Where Q is the hydraulic rotary joint flow, V is the displacement, and n is the speed.

[0084] Hydraulic power formula: P = Q x Δp

[0085] Where P is the hydraulic system power, and Δp is the hydraulic system pressure difference (i.e., the hydraulic rotary joint inlet and outlet pressure difference).

[0086] Considering the internal losses of the hydraulic rotary joint, the hydraulic system pressure difference can be expressed as: Δp = Pin - Pout - Pv - Pf

[0087] Where Pin is the inlet pressure, Pout is the outlet pressure, Pv is the hydraulic rotary joint internal oil leakage loss, and Pf is the friction loss, which is usually negligible in practical applications.

[0088] The relationship between the pressure difference Δp and the load can be expressed as:

[0089] Δp ∝ Q² ∝ (load)²

[0090] This relationship shows that the pressure difference Δp increases with the increase of the load, and the rate of increase is faster than the rate of increase of the load, because the change of Q is the change of Q². This also explains why the hydraulic rotary joint needs more torque to maintain rotation when the load increases.

[0091] Hydraulic rotary joint torque and speed formula P x 9550 = (n x V x ηm) T

[0092] Wherein, P is the input hydraulic power (unit: W), 9550 is a constant for converting power from unit W to unit hp (horsepower, commonly used to describe the power of the hydraulic system), n is the rotation speed of the hydraulic motor (unit: rpm), V is the volume of the rotary joint (unit: m³), and ηm is the mechanical efficiency, representing the mechanical conversion efficiency of the hydraulic rotary joint. The physical meaning of this formula is that the output torque T of the hydraulic rotary joint is equal to the energy input to the hydraulic rotary joint P divided by the product of the output rotation speed n, the volume V of the hydraulic rotary joint, and the mechanical efficiency ηm.

[0093] Therefore, it is shown that using the motor speed as the inner loop of closed-loop control can achieve the stability of the system control process. That is, in the present exemplary embodiment, double closed-loop control is adopted to achieve motion control stability and position accuracy under different output torque conditions. The functions of the bidirectional plunger pump and the electromagnetic on-off valve are fully utilized to achieve the purpose of position control and pressure maintenance control through closed-loop programs.

[0094] In addition, it should be noted that the load observation method of the prior art is the same as the present exemplary embodiment (both observe the Δp value), but the control logic is different. The prior art determines the load according to the Δp value, and the PWM duty cycle is set according to D=k*Δp, which is an open-loop control. The output power is set according to the load, but during the rotation of the hydraulic rotary joint, the load and the total power can only be approximately linear, not linear. For example, during the switching between acceleration start and stable operation and stop stages, and during the process of being affected by load fluctuations and the conversion of positive load / negative load and inertia, the control method will cause the system to be unstable and jitter. The control process of the present exemplary embodiment is a speed closed loop as an inner loop, which achieves relatively stable flow output to the rotary joint and higher stability in the dynamic operation process of the system under different loads and rotation processes.

[0095] At the same time, the present exemplary embodiment sets an upper bias according to the Δp value, and the Δp value is only a reference. Within the range, it can meet the stability of the system static stiffness to load fluctuation and load change. The Δp value of the prior art is used as a control parameter, which lacks accuracy.

[0096] Obviously, the above embodiments are only examples for clarity and do not limit the implementation. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all implementation methods. The obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A robotic hydraulic rotary joint control system, characterized by: The hydraulic rotary joint comprises: a hydraulic rotary joint; a position feedback unit arranged on the hydraulic rotary joint; a first electromagnetic on-off valve and a second electromagnetic on-off valve, which are respectively connected to a first inlet and outlet port of the hydraulic rotary joint and a second inlet and outlet port of the hydraulic rotary joint, and a first pressure feedback unit is arranged on the first inlet and outlet port of the hydraulic rotary joint, and a second pressure feedback unit is arranged on the second inlet and outlet port of the hydraulic rotary joint; a direct current motor; a constant-displacement bidirectional plunger pump, a driving end of the constant-displacement bidirectional plunger pump being connected to the direct current motor, a first inlet and outlet port of the constant-displacement bidirectional plunger pump being connected to the first electromagnetic on-off valve, and a second inlet and outlet port of the constant-displacement bidirectional plunger pump being connected to the second electromagnetic on-off valve; a pressurized oil tank, the pressurized oil tank being connected to the first inlet and outlet port of the constant-displacement bidirectional plunger pump through a first one-way valve and being connected to the second inlet and outlet port of the constant-displacement bidirectional plunger pump through a second one-way valve; a proportional overflow valve, the proportional overflow valve being connected to the first inlet and outlet port of the constant-displacement bidirectional plunger pump through a first end of a shuttle valve and being connected to the second inlet and outlet port of the constant-displacement bidirectional plunger pump through a second end of the shuttle valve; a controller, the controller comprising four control signal input ends connected to the direct current motor, the first pressure feedback unit, the second pressure feedback unit and the position feedback unit respectively, and four control signal output ends connected to the direct current motor, the proportional overflow valve, the first electromagnetic on-off valve and the second electromagnetic on-off valve respectively; a host computer connected to the controller; the control method of the control system comprises a hydraulic rotary joint rotation control step and a hydraulic rotary joint pressure maintaining control step performed in a position maintaining stage after the hydraulic rotary joint rotation control step is completed; the hydraulic rotary joint pressure maintaining control step comprises the following sub-steps: When the hydraulic rotary joint position is kept, if the load is vertical downward load inertia, the second inlet and return port of the hydraulic rotary joint is positive load, at this time the relief pressure setting value P of the proportional relief valve _d The circuit segment pressure value P2 is added to the pressure value offset value Pes, wherein the circuit segment pressure value P2 is obtained by the second pressure feedback unit, and the pressure value offset value Pes is Δp, is a gain coefficient, and Δp is a pressure difference, i.e., the pressure value of the first pressure feedback unit minus the pressure value of the second pressure feedback unit; when the hydraulic rotary joint position is kept, if the load is vertical upward load inertia, the opposite is set; The electromagnetic switch valve of the positive load acting section is opened, and the electromagnetic switch valve of the negative load acting section remains closed, so that the motor rotating direction is set for the communication side of the constant displacement bidirectional plunger pump and the positive load acting section electromagnetic switch valve; the closed hydraulic circuit forms a local stable value under the action of the proportional overflow valve, and when the pressure feedback unit of the positive load acting section reaches the overflow pressure setting value P of the proportional overflow valve d , the electromagnetic switch valve of the positive load acting section is closed; the hydraulic rotary joint rotation control step comprises the following sub-steps: the controller receives a host computer signal, the host computer signal comprising target position information of the hydraulic rotary joint; the controller reads a position feedback signal of the position feedback unit, compares the position feedback signal with the target position information to determine a rotation direction and an angle of the hydraulic rotary joint, and forms a direction rotation instruction; the controller outputs the direction rotation instruction to the direct current motor, the proportional overflow valve, the first electromagnetic on-off valve and the second electromagnetic on-off valve respectively, and performs a control operation; when the direction rotation instruction is a clockwise direction rotation instruction, the control operation comprises: the constant-displacement bidirectional plunger pump is driven to rotate by the direct current motor, the pressurized oil tank provides an oil source and an initial pressure to the second inlet and outlet port of the constant-displacement bidirectional plunger pump as an inlet through the second one-way valve, and the first inlet and outlet port of the constant-displacement bidirectional plunger pump as an outlet flows out fluid; the shuttle valve is opened at the first end and closed at the second end under the action of an oil passage pressure, and an overflow pressure set value of the proportional overflow valve acts on a passage formed by the constant-displacement bidirectional plunger pump and the first electromagnetic on-off valve; the first electromagnetic on-off valve and the second electromagnetic on-off valve are opened, and a system oil passage is formed by the first inlet and outlet port of the constant-displacement bidirectional plunger pump, the first electromagnetic on-off valve, the first inlet and outlet port of the hydraulic rotary joint, the second inlet and outlet port of the hydraulic rotary joint, the second electromagnetic on-off valve and the second inlet and outlet port of the constant-displacement bidirectional plunger pump; when the direction rotation instruction is a counterclockwise direction rotation instruction, the operation is opposite. When the position feedback signal of the position feedback unit is consistent with the target position information, the hydraulic rotary joint reaches the set target value, at which time the first electromagnetic on-off valve and the second electromagnetic on-off valve are simultaneously closed by the controller, the hydraulic rotary joint stops rotating, and the position closed loop is completed.

2. The control system for a robotic hydraulic rotary joint according to claim 1, wherein: The controller further comprises a communication interface, and the controller is connected to an upper computer through the communication interface.

3. The control system for a robotic hydraulic rotary joint according to claim 1, wherein: In the hydraulic rotary joint rotation control step, the overflow pressure set value of the proportional overflow valve is set as the system maximum protection pressure Pmax.

4. The control system for a robotic hydraulic rotary joint according to claim 1, wherein: In the hydraulic rotary joint rotation control step, when the position of the hydraulic rotary joint is controlled by the outer loop, the speed of the direct current motor is simultaneously controlled by the inner loop, so that the hydraulic rotary joint runs at a stable speed under different loads and output torques.

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