Hydraulic power constant load control method for fatigue test of contact network compensation device

Abstract

The invention relates to the technical field of railway catenary part simulation tests, in particular to a hydraulic power constant load control method for a fatigue test of a catenary compensation device, which comprises the steps that a pressure sensor is integrated on the end face of a piston of a hydraulic cylinder, the end face is located in a rodless cavity of the hydraulic cylinder, and the pressure sensor detects the actual pressure of the end face in real time; a proportional overflow valve is connected with an oil way of the hydraulic cylinder, and a viscosity sensor is arranged in the oil tank to monitor the oil state; the opening degree of the proportional overflow valve is dynamically adjusted according to detection data of the pressure sensor; and the rotating speed of the oil pump motor is adjusted based on the opening degree adjusting result of the proportional overflow valve and the oil state data. Through end face direct measurement pressure and closed-loop control over the rotating speed of the oil pump motor, the problem that output load force is unstable is solved, uniform and stable movement is achieved through accurate pressure control, telescoping of the overhead line system is truly simulated, meanwhile, hydraulic impact is reduced through self-adaptive adjustment of the rotating speed of the oil pump, and the service life of key components of testing equipment is prolonged.

Description

Technical Field

[0001] This invention relates to the field of simulation testing technology for railway catenary components, and in particular to a hydraulic power constant load control method for fatigue testing of catenary compensation devices. Background Technology

[0002] In the rail transit sector, fatigue testing of overhead contact line compensation devices is crucial for ensuring equipment reliability. In existing technologies, hydraulic cylinders are commonly used as the power source for testing, driving the load structure in reciprocating motion to meet the testing requirements of the overhead contact line compensation devices.

[0003] During the test, the hydraulic cylinder is affected by changes in oil temperature, internal leakage and frictional resistance, resulting in unstable output load force and distorted test data. At the same time, under typical low-speed conditions, the hydraulic cylinder is prone to displacement jerking, which disrupts the smoothness of movement. All of these factors make it impossible to accurately assess the fatigue life of the compensation device. Summary of the Invention

[0004] This invention provides a hydraulic power constant load control method for fatigue testing of contact wire compensation devices, which can effectively solve the problems in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A hydraulic power constant load control method for fatigue testing of overhead contact line compensation devices includes:

[0007] A pressure sensor is integrated on the piston end face of the hydraulic cylinder, the end face being located within the rodless chamber of the hydraulic cylinder, and the pressure sensor detects the actual pressure on the end face in real time.

[0008] A proportional relief valve is installed in the oil circuit connected to the hydraulic cylinder, and a viscosity sensor is installed in the oil tank to monitor the oil condition;

[0009] The opening degree of the proportional relief valve is dynamically adjusted based on the detection data from the pressure sensor.

[0010] Based on the opening adjustment result of the proportional relief valve and the oil state data, the speed of the oil pump motor is adjusted.

[0011] Furthermore, the wiring harness of the pressure sensor is threaded through an axial channel inside the piston rod of the hydraulic cylinder and connected to the controller via a sealing joint located at the end of the piston rod.

[0012] Furthermore, the wiring harness of the pressure sensor is a twisted-pair shielded cable, and the shielding layer of the twisted-pair shielded cable is grounded through the sealed connector.

[0013] Furthermore, the twisted-pair shielded cable is connected to a signal conditioning module, which performs differential amplification and filtering on the pressure signal.

[0014] Furthermore, an elastic conductive bushing is provided inside the axial channel, and the inner wall of the elastic conductive bushing is in contact with the shielding layer of the twisted pair shielded cable.

[0015] A conductive magnetic layer is filled between the outer wall of the elastic conductive bushing and the inner wall of the axial channel.

[0016] Furthermore, based on the opening adjustment result of the proportional relief valve and the oil state data, the speed of the oil pump motor is adjusted, including:

[0017] Dynamically generate speed correction coefficient α: And when α is less than the set threshold, α takes the set threshold.

[0018] in, This represents the relative deviation between the current viscosity of the oil and the reference viscosity. The real-time opening degree of the proportional relief valve is given by k1, which is the first weighting coefficient, and k2, which is the second weighting coefficient.

[0019] Calculate the target rotational speed N of the oil pump: ;

[0020] Wherein, N0 is the preset reference speed.

[0021] Furthermore, the first weight coefficient k1 and the second weight coefficient k2 are dynamically optimized through reinforcement learning, including:

[0022] A reward function is constructed using the standard deviation of pressure fluctuation and energy consumption per unit test cycle.

[0023] The reward function is maximized by iteratively updating k1 and k2 in consecutive tests using the Q-learning algorithm.

[0024] Furthermore, it also includes:

[0025] When a decrease in the opening degree of the proportional relief valve is detected, a positive compensation factor β is generated: ;

[0026] Wherein, γ is the compensation coefficient, which is positively correlated with the proportion of reduction in opening degree;

[0027] Correct the target rotational speed N: .

[0028] Furthermore, the target rotational speed is subject to a safety limit:

[0029] The lower limit threshold for the speed is set to 40%-60% of the rated speed of the oil pump, and the upper limit threshold for the speed is set to 105%-110% of the rated speed of the oil pump.

[0030] If the target rotational speed is lower than the lower limit threshold, the actual output rotational speed is taken as the lower limit threshold.

[0031] If the target rotational speed is higher than the upper limit threshold, the actual output rotational speed is taken as the upper limit threshold.

[0032] Otherwise, the actual output speed is taken as the target speed.

[0033] Furthermore, it also includes emergency switching under extreme operating conditions;

[0034] When the absolute value of the real-time opening change rate of the proportional relief valve simultaneously exceeds 25% / s-35% / s, and, More than 10%-30%;

[0035] The calculation of the speed correction coefficient α is paused, and the oil pump motor is switched to a safe operating speed, which is 60%-70% of the rated speed of the oil pump.

[0036] The technical solution of this invention can achieve the following technical effects:

[0037] This invention solves the problem of unstable output load force by directly measuring the pressure at the end face and controlling the closed-loop speed of the oil pump motor. Precise pressure control enables uniform and stable movement, realistically simulating the expansion and contraction of the contact network. At the same time, the adaptive adjustment of the oil pump speed also reduces hydraulic shock and extends the life of key components of the testing equipment. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present 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 only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A flowchart of a hydraulic power constant load control method for fatigue testing of overhead contact line compensation devices;

[0040] Figure 2 The flowchart shows the dynamic optimization of the first weight coefficient k1 and the second weight coefficient k2 through reinforcement learning.

[0041] Figure 3 A flowchart for applying a safety limit to the target rotational speed. Detailed Implementation

[0042] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0043] The fatigue test object in this embodiment of the invention includes two test wheel sets and a test compensating rope. The compensating rope is sequentially wound around the two test wheel sets, with one end connected to the load structure and the other end connected to the power output end of the hydraulic cylinder. The two test wheel sets are fixed to the main frame of the testing equipment. During the reciprocating power output of the hydraulic cylinder, the movement of the test compensating rope and the rotation of the test wheel sets are driven, thereby realizing the fatigue test of the test compensating rope and the test wheel sets. Of course, the above structural form is only an example of a fatigue testing scheme and is not intended to limit the scope of protection of this invention. Other testing methods that can realize power output through a hydraulic cylinder are also applicable to this invention.

[0044] like Figure 1 As shown, in an embodiment of the present invention, a hydraulic power constant load control method for fatigue testing of a contact network compensation device includes:

[0045] A pressure sensor is integrated into the piston end face of the hydraulic cylinder. The end face is located in the rodless chamber of the hydraulic cylinder, and the pressure sensor detects the actual pressure on the end face in real time.

[0046] A proportional relief valve is installed in the oil circuit connection with the hydraulic cylinder, and a viscosity sensor is installed in the oil tank to monitor the oil condition.

[0047] The opening degree of the proportional relief valve is dynamically adjusted based on the detection data from the pressure sensor.

[0048] Based on the opening adjustment results of the proportional relief valve and the oil condition data, the speed of the oil pump motor is adjusted.

[0049] During implementation, the pressure sensor is directly integrated into the end face of the hydraulic cylinder piston located in the rodless chamber. This allows for real-time detection of the direct pressure applied by the piston, thus eliminating pressure fluctuations caused by frictional fluctuations in the sealing structure within the rodless chamber. In this embodiment, specifically, the pressure sensor's detection data and the opening degree of the proportional relief valve form a dynamic negative feedback closed loop. When the pressure is lower than the target value, the proportional relief valve reduces its opening degree to increase the system pressure. When the pressure is higher than the target value, the proportional relief valve increases its opening degree to decrease the system pressure. By adjusting the proportional relief valve, sudden load fluctuations can be quickly suppressed.

[0050] In this embodiment, the speed of the oil pump motor is synchronously referenced to the proportional relief valve opening adjustment result and the oil state data. The opening adjustment result reflects the short-term pressure demand. If the proportional relief valve remains at a high opening, the motor speed is reduced. The oil viscosity data is used to address long-term thermal drift. If the viscosity increases at low temperatures, the speed is increased to compensate for the flow loss.

[0051] This invention solves the problem of unstable output load force by directly measuring the pressure at the end face and controlling the closed-loop speed of the oil pump motor. Precise pressure control enables uniform and stable movement, realistically simulating the expansion and contraction of the contact network. At the same time, the adaptive adjustment of the oil pump speed also reduces hydraulic shock and extends the life of key components of the testing equipment.

[0052] As a preferred embodiment, the pressure sensor wiring harness is routed through an axial channel inside the hydraulic cylinder piston rod and connected to the controller via a sealing joint located at the end of the piston rod. This preferred embodiment achieves fully enclosed protection along the physical path; specifically, the built-in design prevents wiring harness breakage caused by external pulling or oil corrosion, and the sealing joint maintains effective protection during the reciprocating motion of the piston rod.

[0053] To further address the electromagnetic interference problem of pressure signals, as a preferred embodiment of the above scheme, the pressure sensor's wiring harness is a twisted-pair shielded cable, and the shielding layer of the twisted-pair shielded cable is grounded through a sealed connector. In this preferred scheme, the two conductors of the twisted-pair shielded cable are spirally wound with a fixed pitch, ensuring that the interference currents induced by the external electromagnetic field on the two conductors have equal amplitudes and opposite phases, which can be canceled out by differential input. The shielding layer used in the twisted-pair shielded cable can often achieve multi-layer shielding. Specifically, an aluminum foil layer can cover high-frequency interference, while a copper mesh braided layer can absorb medium and low-frequency magnetic fields. Grounding the shielding layer of the twisted-pair shielded cable forms a low-impedance path, thereby eliminating some of the electromagnetic noise in the hydraulic system, such as motor magnetic field interference.

[0054] In some embodiments of the present invention, a twisted-pair shielded cable is connected to a signal conditioning module. The signal conditioning module performs differential amplification and filtering on the pressure signal. Differential amplification suppresses common-mode interference, and filtering removes high-frequency fluctuations, thereby improving the signal-to-noise ratio of the pressure signal.

[0055] As a further optimization of the electromagnetic barrier, based on the above embodiments, an elastic conductive bushing is provided inside the axial channel, and the inner wall of the elastic conductive bushing contacts the shielding layer of the twisted-pair shielded cable; a conductive magnetic layer is filled between the outer wall of the elastic conductive bushing and the inner wall of the axial channel. In this preferred embodiment, the elastic conductive bushing absorbs the vibration energy of the piston rod, reducing cable fretting wear; in some embodiments of the present invention, the elastic conductive bushing preferably adopts a silver-plated silicone composite structure, the silicone matrix provides resistance to oil corrosion and elastic deformation capability, and the silver plating layer on the surface ensures continuous low-resistance contact with the shielding layer of the twisted-pair shielded cable.

[0056] In some embodiments of the present invention, the conductive magnetic layer may specifically be a soft magnetic ferrite sleeve, with both its inner and outer walls plated with nickel to achieve conductivity. The inner wall of the conductive magnetic layer matches the outer diameter of the elastic conductive bushing, and the outer wall matches the inner diameter of the axial channel, satisfying the following conductive contact relationship: the inner wall of the conductive magnetic layer is directly attached to the silver-plated outer wall of the elastic conductive bushing, forming a continuous conductive path; the outer wall of the conductive magnetic layer is interference-fitted with the inner wall of the piston rod axial channel, establishing a grounding connection for the equipment. Through this structure, the conductive magnetic layer can absorb low-frequency magnetic field noise in the hydraulic system, while its nickel plating layer conducts induced charges to the ground through the piston rod, completely avoiding signal drift caused by static electricity accumulation.

[0057] The use of the above combined structure ensures the physical stability and electrical continuity of the grounding connection through the elastic bushing, while the conductive magnetic layer extends the effective frequency band of the shield, especially for low and medium frequency magnetic fields that are difficult to handle by ordinary shielding layers. Both of these factors ultimately ensure the signal purity and long-term reliability of the pressure sensor in harsh hydraulic environments.

[0058] As a preferred embodiment of the above, adjusting the speed of the oil pump motor based on the opening adjustment result of the proportional relief valve and the oil state data includes:

[0059] Dynamically generate speed correction coefficient α: Furthermore, when α is less than the set threshold, α is taken as the set threshold, which can be selected from 0.2 to 0.4 according to actual needs;

[0060] in, This is the relative deviation between the current viscosity and the reference viscosity of the oil. Specifically, it is the difference between the current viscosity and the reference viscosity, and then the ratio of the difference to the reference viscosity. The unit is %, and the value can be positive or negative. The reference viscosity can be the viscosity value at 25℃. The value represents the real-time opening degree of the proportional relief valve, in %; k1 is the first weighting coefficient. The first weight is assigned as a dimensionless constant; k2 is the second weight coefficient. A second weight is assigned, which is a dimensionless constant; both k1 and k2 achieve sensitivity adjustment.

[0061] Calculate the target speed N of the oil pump: ;

[0062] Wherein, N0 is the preset reference speed.

[0063] In this preferred scheme, the algorithmic control strategy of dynamically generating the speed correction coefficient α can improve the load stability of the hydraulic system under varying working conditions; the real-time opening change of the proportional relief valve and the oil viscosity deviation are quantified as complementary control quantities.

[0064] During operation, when the proportional relief valve opening increases (when the pressure is higher than the target value), α decreases, driving the oil pump to slow down; when the proportional relief valve opening decreases (when the pressure is lower than the target value), α increases, driving the oil pump to speed up. When the oil thickens at low temperatures... At the same time, α is negatively corrected, automatically reducing speed to avoid motor overload, and high-temperature thinning is also achieved. At that time, speed increases are allowed to compensate for traffic loss.

[0065] As a preferred embodiment of the above, such as Figure 2 As shown, the first weight coefficient k1 and the second weight coefficient k2 are dynamically optimized through reinforcement learning, including: constructing a reward function based on the standard deviation of stress fluctuation and energy consumption per unit test cycle; and iteratively updating k1 and k2 in continuous tests using the Q-learning algorithm to maximize the reward function.

[0066] In this preferred scheme, the standard deviation of pressure fluctuation directly reflects the accuracy and stability of load control, while the energy consumption per unit test cycle measures the economic efficiency of system operation. By constructing the two together as a reward function, the optimization objective does not solely pursue extreme stability or the lowest energy consumption, but seeks the optimal balance point.

[0067] During implementation, the system continuously collects pressure fluctuation data and energy consumption data during continuous fatigue testing, and calculates the real-time reward value. In some embodiments of the present invention, the calculation process of the pressure fluctuation standard deviation includes continuously collecting the actual pressure value fed back by the pressure sensor at a set frequency within a statistical time period, and calculating the standard deviation based on the collected actual pressure value to obtain the pressure fluctuation standard deviation; while the energy consumption per unit test cycle refers to the total energy consumed by the hydraulic system during the fatigue test cycle within the statistical time period, which is then averaged over the time used for that cycle.

[0068] The Q-learning algorithm automatically explores and adjusts the values ​​of the first weight coefficient k1 and the second weight coefficient k2 based on historical reward information. Its advantage lies in the fact that it does not require a precise mathematical model to be set in advance. Instead, it adaptively finds the best combination of k1 and k2 in long-term operation through trial and error and learning, so as to maximize the reward function, that is, to achieve the minimum pressure fluctuation and the lowest unit energy consumption at the same time.

[0069] As a preferred embodiment of the above embodiments, the hydraulic power constant load control method for fatigue testing of the contact wire compensation device further includes:

[0070] When a decrease in the proportional relief valve opening is detected, a positive compensation factor β is generated: ;

[0071] Wherein, γ is the compensation coefficient, which is positively correlated with the reduction ratio of the opening. The positive correlation ratio can be set according to experience.

[0072] Corrected target rotational speed N: .

[0073] This optimized solution improves the system's response speed to sudden increases in load demand, manifested as a rapid decrease in the relief valve opening. By using a positive compensation factor β, the system amplifies the reduction in opening proportionally and adds it to the original speed calculation. This is equivalent to giving the oil pump motor speed a pre-acceleration at the moment the system demand increases, forming a feedforward compensation mechanism. This effectively overcomes the inherent inertial delay and control lag of the system, enabling the oil pump to output the required flow more quickly, thereby responding to the pressure increase demand more rapidly.

[0074] During implementation, excessively low speed can cause difficulties in oil pump suction, increased flow pulsation, poor lubrication, and may even lead to cavitation damage to the pump; excessively high speed can cause pump overspeed operation, motor overload and overheating, accelerated wear, and even mechanical failure. To solve these problems, as a preferred embodiment, the target speed is subject to a safety limit: the lower speed limit is set at 40%-60% of the rated speed of the oil pump, and the upper speed limit is set at 105%-110% of the rated speed of the oil pump. Figure 3 As shown:

[0075] If the target speed is lower than the lower speed threshold, the actual output speed is taken as the lower speed threshold.

[0076] If the target speed is higher than the upper limit threshold, the actual output speed will be the upper limit threshold.

[0077] Otherwise, the actual output speed is taken as the target speed.

[0078] By setting reasonable upper and lower limit ranges, the safety limit forces the calculated target speed to be restricted within a safe physical operating range. This retains the main benefits of dynamic speed regulation while completely eliminating the risk of equipment over-limit operation due to abnormal control algorithm output or extreme operating conditions, thus ensuring the long-term reliability and safety of the testing equipment.

[0079] As another optimization of safety assurance measures, the hydraulic power constant load control method used for fatigue testing of contact wire compensation devices also includes emergency switching under extreme working conditions.

[0080] When the absolute value of the real-time opening change rate of the proportional relief valve simultaneously exceeds 25% / s-35% / s, and, If the speed exceeds 10%-30%, suspend the calculation of the speed correction coefficient α and control the oil pump motor to switch to safe speed operation, which is 60%-70% of the rated speed of the oil pump.

[0081] This preferred solution establishes a rapid protection mechanism for sudden severe failures or extreme abnormal operating conditions. Specifically, a sudden and abnormal increase in the rate of change of the relief valve opening indicates a potential sudden change in load, such as jamming, breakage, or severe internal leakage. Excessive deviation in oil viscosity may indicate uncontrolled oil temperature, severe contamination, or oil deterioration. When both conditions are met simultaneously, the system is classified as operating under extreme conditions. In this situation, conventional speed regulation based on optimization algorithms may fail or exacerbate the risk. This preferred solution immediately suspends complex adaptive calculations and forcibly switches the oil pump motor speed to a pre-set safe speed. This provides the flow rate needed to maintain basic system circulation and prevent dry friction, while ensuring that the motor and pump unit do not overload or exceed speed limits, thus improving the fault tolerance of the entire test system.

[0082] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A hydraulic constant load control method for fatigue testing of overhead contact line compensation devices, characterized in that, include: A pressure sensor is integrated on the piston end face of the hydraulic cylinder, the end face being located within the rodless chamber of the hydraulic cylinder, and the pressure sensor detects the actual pressure on the end face in real time. A proportional relief valve is installed in the oil circuit connected to the hydraulic cylinder, and a viscosity sensor is installed in the oil tank to monitor the oil condition; The opening degree of the proportional relief valve is dynamically adjusted based on the detection data from the pressure sensor. Based on the opening adjustment result of the proportional relief valve and the oil state data, the speed of the oil pump motor is adjusted.

2. The hydraulic constant load control method for fatigue testing of contact wire compensation devices according to claim 1, characterized in that, The wiring harness of the pressure sensor is run through an axial channel inside the piston rod of the hydraulic cylinder and connected to the controller through a sealing joint located at the end of the piston rod.

3. The hydraulic constant load control method for fatigue testing of contact wire compensation devices according to claim 2, characterized in that, The wiring harness of the pressure sensor is a twisted-pair shielded cable, and the shielding layer of the twisted-pair shielded cable is grounded through the sealed connector.

4. The hydraulic constant load control method for fatigue testing of contact wire compensation devices according to claim 3, characterized in that, The twisted-pair shielded cable is connected to the signal conditioning module, which performs differential amplification and filtering on the pressure signal.

5. The hydraulic constant load control method for fatigue testing of contact wire compensation devices according to claim 3, characterized in that, An elastic conductive bushing is provided inside the axial channel, and the inner wall of the elastic conductive bushing is in contact with the shielding layer of the twisted pair shielded cable. A conductive magnetic layer is filled between the outer wall of the elastic conductive bushing and the inner wall of the axial channel.

6. The hydraulic constant load control method for fatigue testing of contact wire compensation devices according to claim 1, characterized in that, Based on the opening adjustment result of the proportional relief valve and the oil state data, the speed of the oil pump motor is adjusted, including: Dynamically generate speed correction coefficient α: And when α is less than the set threshold, α takes the set threshold. in, This represents the relative deviation between the current viscosity of the oil and the reference viscosity. The real-time opening degree of the proportional relief valve is given by k1, which is the first weighting coefficient, and k2, which is the second weighting coefficient. Calculate the target rotational speed N of the oil pump: ; Wherein, N0 is the preset reference speed.

7. The hydraulic constant load control method for fatigue testing of contact wire compensation devices according to claim 6, characterized in that, The first weight coefficient k1 and the second weight coefficient k2 are dynamically optimized through reinforcement learning, including: A reward function is constructed using the standard deviation of pressure fluctuation and energy consumption per unit test cycle. The reward function is maximized by iteratively updating k1 and k2 in consecutive tests using the Q-learning algorithm.

8. The hydraulic power constant load control method for fatigue testing of contact wire compensation devices according to claim 6, characterized in that, Also includes: When a decrease in the opening degree of the proportional relief valve is detected, a positive compensation factor β is generated: ; Wherein, γ is the compensation coefficient, which is positively correlated with the proportion of reduction in opening degree; Correct the target rotational speed N: .

9. The hydraulic constant load control method for fatigue testing of contact wire compensation devices according to claim 6, characterized in that, The target rotational speed is subject to a safety limit: The lower limit threshold for the speed is set to 40%-60% of the rated speed of the oil pump, and the upper limit threshold for the speed is set to 105%-110% of the rated speed of the oil pump. If the target rotational speed is lower than the lower limit threshold, the actual output rotational speed is taken as the lower limit threshold. If the target rotational speed is higher than the upper limit threshold, the actual output rotational speed is taken as the upper limit threshold. Otherwise, the actual output speed is taken as the target speed.

10. The hydraulic constant load control method for fatigue testing of contact wire compensation devices according to claim 6, characterized in that, It also includes emergency switching under extreme operating conditions; When the absolute value of the real-time opening change rate of the proportional relief valve simultaneously exceeds 25% / s-35% / s, and, More than 10%-30%; The calculation of the speed correction coefficient α is paused, and the oil pump motor is switched to a safe operating speed, which is 60%-70% of the rated speed of the oil pump.

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