Hydraulic cylinder and method for hydraulic cylinder position self-sensing

Abstract

The application discloses a hydraulic cylinder and a hydraulic cylinder position self-sensing method. The hydraulic cylinder comprises a cylinder barrel, a piston rod, a hydraulic medium, a light-emitting assembly and a light transmission assembly. The piston rod is movably arranged in the cylinder barrel along a first direction. The hydraulic medium is filled in a containing chamber, and the hydraulic medium comprises a mixture of a light-transmitting fluid and a colorant. The hydraulic medium is configured as a transmission medium for the movement of the piston rod and a filtering medium for filtering the polychromatic light. The light-emitting assembly moves synchronously with the piston rod, and the light-emitting assembly is used for emitting the polychromatic light. The light transmission assembly is connected to the cylinder barrel. The piston rod is configured to move along the first direction under the hydraulic drive, so as to change the optical path length of the hydraulic medium between the light-emitting assembly and the light transmission assembly, and then the spectral characteristics of the transmitted light are changed correspondingly with the displacement of the piston rod. The application can realize the structural integration and medium multiplexing of the hydraulic actuating element and the displacement sensing function.

Description

Technical Field

[0001] This application relates to the field of hydraulic transmission technology, and in particular to a hydraulic cylinder and a hydraulic cylinder position self-sensing method. Background Technology

[0002] Hydraulic actuators, as core power components in fields such as engineering machinery, intelligent manufacturing, and aerospace, play a crucial role in converting hydraulic energy into mechanical energy and driving load motion. With the continuous improvement of industrial automation, higher demands are placed on the control precision, response speed, and intelligence level of hydraulic systems. Accurate position sensing of actuators is a fundamental prerequisite for achieving high-precision closed-loop control. Traditional hydraulic cylinders mainly rely on externally installed displacement sensors to obtain piston position information. While this approach can achieve position feedback, it suffers from inherent defects such as structural redundancy, low integration, and poor environmental adaptability, making it difficult to meet the compact and highly reliable requirements of modern intelligent equipment.

[0003] In existing technologies, the position detection of hydraulic cylinders generally employs external measuring devices such as magnetostrictive sensors or optical scales. These sensors need to be coupled to the piston rod via mechanical connectors, which not only increases the axial dimensions and assembly complexity of the system, but also introduces mechanical transmission backlash that reduces detection accuracy and dynamic response characteristics. In particular, external sensors are prone to signal distortion or device failure under harsh conditions such as strong electromagnetic interference, high temperature and pressure, or dust pollution. Their electrical transmission lines also face challenges in sealing and wiring. Summary of the Invention

[0004] The main objective of this application is to propose a hydraulic cylinder and a hydraulic cylinder position self-sensing method, which can realize the structural integration and media reuse of hydraulic actuators and displacement sensing functions.

[0005] To achieve the above objectives, some embodiments of this application propose a hydraulic cylinder, comprising: The cylinder defines the receiving chamber; A piston rod is movably disposed in the cylinder along a first direction, with part of the piston rod located inside the receiving chamber and part of the piston rod located outside the receiving chamber, and the piston rod divides the receiving chamber into a first chamber and a second chamber; Hydraulic medium, filling the containment chamber, comprises a mixture of a light-transmitting fluid and a colorant, and is configured to serve both as a transmission medium for piston rod movement and as a filtering medium for filtering polychromatic light; The light-emitting component is connected to the piston rod. The light-emitting component moves synchronously with the piston rod and is used to emit polychromatic light. The optical transmission component is connected to the cylinder and is used to receive and transmit transmitted light filtered by the hydraulic medium. The piston rod is configured to move along a first direction under hydraulic drive to change the optical path length of the hydraulic medium between the light-emitting component and the light transmission component, thereby causing the spectral characteristics of the transmitted light to change accordingly with the displacement of the piston rod.

[0006] In some embodiments, the light-emitting component includes a light-emitting body and a first light-forming component. The first light-forming component has a first light-inlet plane and a first light-outlet plane. The first light-inlet plane and the first light-outlet plane are disposed opposite to each other and parallel. The first light-inlet plane is used to receive polychromatic light, and the first light-outlet plane is disposed facing the hydraulic medium. The first light-outlet plane is used to guide the polychromatic light to the hydraulic medium.

[0007] In some embodiments, the optical transmission component includes an optical fiber and a second optical rectifier. The second optical rectifier has a second light-incoming plane and a second light-outgoing plane. The second light-incoming plane and the second light-outgoing plane are arranged opposite to each other and parallel. The second light-incoming plane faces the hydraulic medium. The second light-incoming plane is used to receive transmitted light, and the second light-outgoing plane is used to guide the transmitted light to the optical fiber.

[0008] In some embodiments, the piston rod has a first end and a second end opposite to each other along a first direction, the light-emitting component is disposed at the first end, and the light transmission component is connected to the end wall of the cylinder. In this configuration, between the first end and the end wall, the first light-emitting plane, the hydraulic medium, and the second light-entering plane are arranged sequentially along the first direction to form an optical path that propagates along the first direction.

[0009] In some embodiments, the hydraulic cylinder further includes an oil supply assembly, which includes a first oil nozzle and a second oil nozzle, the first oil nozzle communicating with a first chamber and the second oil nozzle communicating with a second chamber; The oil supply assembly is configured to drive the piston rod to move in a first direction by adjusting the volume of the hydraulic medium in the first and second chambers.

[0010] In some embodiments, the hydraulic medium is configured to have high transmittance for a first wavelength of light in the polychromatic light and low transmittance for a second wavelength of light in the polychromatic light.

[0011] In some embodiments, the cylinder barrel is provided with a light-transmitting portion located on the side wall of the cylinder barrel, and the light-transmitting portion is configured to allow transmitted light received by the light transmission component to be emitted from the hydraulic medium.

[0012] In some embodiments, the hydraulic cylinder further includes a processing module, which is communicatively connected to an optical transmission component, and the processing module is configured to: Obtain the spectral signal of the transmitted light; The displacement of the piston rod relative to the cylinder is calculated based on the power ratio of different wavelengths of light in the spectral signal.

[0013] The second aspect of this application provides a hydraulic cylinder position self-sensing method, applied to the hydraulic cylinder of any of the above claims. The hydraulic cylinder position self-sensing method includes: Hydraulic medium is injected into the cylinder. The hydraulic medium consists of a mixture of light-transmitting fluid and colorant. The hydraulic medium serves as both a transmission medium and a light filtering medium. Activate the light-emitting component to make it emit polychromatic light, which passes through the hydraulic medium to form transmitted light; Receive transmitted light and acquire its spectral signal; Adjusting the volume of hydraulic medium in different chambers within the cylinder drives the piston rod to move relative to the cylinder, thereby changing the optical path length of polychromatic light in the hydraulic medium and thus altering the spectral characteristics of the transmitted light. The displacement of the piston rod is obtained based on the change in spectral characteristics.

[0014] In some embodiments, activating the light-emitting component includes: emitting polychromatic light comprising a first wavelength and a second wavelength through the light-emitting component; and / or, The steps for acquiring the spectral signal include: detecting the power ratio of the first wavelength light to the second wavelength light in the transmitted light; and / or, The steps for calculating the displacement include: calculating the displacement of the piston rod based on the linear relationship between the natural logarithm of the power ratio and the optical path length.

[0015] According to the above embodiments, the beneficial effects of this application are: The hydraulic cylinder of this application includes a cylinder barrel, a piston rod, a hydraulic medium, a light-emitting component, and a light-transmitting component. The cylinder barrel defines a receiving chamber, and the piston rod is movably disposed within the cylinder barrel along a first direction. The piston rod is partially located inside and partially outside the receiving chamber, dividing the receiving chamber into a first chamber and a second chamber. The hydraulic medium fills the receiving chamber and comprises a mixture of a light-transmitting fluid and a colorant. The hydraulic medium is configured to serve both as a transmission medium for piston rod movement and as a filtering medium for filtering polychromatic light. The light-emitting component is connected to the piston rod and moves synchronously with the piston rod, emitting polychromatic light. The light-transmitting component is connected to the cylinder barrel and receives and transmits transmitted light filtered by the hydraulic medium. The piston rod is configured to move along the first direction under hydraulic drive to change the optical path length of the hydraulic medium between the light-emitting component and the light-transmitting component, thereby causing the spectral characteristics of the transmitted light to change accordingly with the displacement of the piston rod. Specifically, by fixing the light-emitting component to a piston rod driven by hydraulic pressure, the piston rod reciprocates along the first direction under the pressure of the transmission medium, simultaneously changing the axial distance between the light-emitting component and the light transmission component stationary in the cylinder, thereby adjusting the propagation path length of the polychromatic light in the hydraulic medium. Based on the selective absorption characteristics of the hydraulic medium for different wavelengths of light, the change in optical path length will cause differences in the attenuation degree of each wavelength component in the transmitted light, ultimately resulting in a definite correspondence between the spectral characteristics of the transmitted light and the displacement of the piston rod, realizing the conversion of mechanical displacement into optical signal.

[0016] The hydraulic cylinder of this application fixes the light-emitting component to the piston rod, allowing the light-emitting element to move synchronously with the piston. Simultaneously, the hydraulic medium filled within the cylinder serves as the light propagation medium, constructing an optical sensing path embedded within the hydraulic cylinder body. Because the hydraulic medium is configured to function as both a transmission and filtering medium—serving as the force transmission medium driving the piston rod and as a filtering medium selectively attenuating polychromatic light—deep coupling between the actuator and the sensing unit is achieved. This eliminates the need for additional linear displacement sensors or magnetostrictive sensors installed outside the cylinder, simplifying the system structure, improving integration and compactness, and reducing the risk of failure due to complex external sensor installation and wiring.

[0017] During operation, as the piston rod moves along the first direction under hydraulic drive, the relative position between the light-emitting component and the light-transmitting component changes, causing a corresponding change in the propagation path length of the polychromatic light in the hydraulic medium. This, in turn, results in a measurable change in the spectral characteristics of the transmitted light related to the displacement. This displacement detection method based on optical path modulation directly converts mechanical displacement into a change in optical signal. It not only avoids the impact of electromagnetic interference and electrostatic coupling on measurement accuracy and improves operational reliability in strong electromagnetic environments, but also achieves real-time and continuous monitoring of the piston position through the optical properties of the hydraulic medium. Closed-loop control can be completed without relying on external coding equipment, effectively improving the intelligence level and response speed of the hydraulic system.

[0018] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or from practice of this application. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application 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 of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a three-dimensional structural diagram of the hydraulic cylinder as viewed from a first perspective in one embodiment of this application; Figure 2 This is a three-dimensional structural diagram of the hydraulic cylinder as viewed from a second perspective in one embodiment of this application; Figure 3 This is a three-dimensional structural diagram of the hydraulic cylinder as viewed from a third-person perspective in one embodiment of this application; Figure 4 This is a cross-sectional structural diagram of a hydraulic cylinder in one embodiment of this application; Figure 5 This is a schematic cross-sectional view of the piston rod in one embodiment of this application; Figure 6 This is a flowchart of a hydraulic cylinder position self-sensing method in one embodiment of this application.

[0021] Explanation of icon numbers: Optical transmission component 1; second optical rectifier component 2; first oil nozzle 3; cylinder 4; piston rod 5; piston rod front end cap 501; second end face sealing ring 502; first optical rectifier component 503; light emitter 504; insulating sealing plug 505; piston support frame 506; second oil nozzle 6; guide sleeve 7; pressure ring sleeve 8; cylinder end cap 9; dustproof ring 10; rod end sealing ring 11; cylinder body sealing ring 12; first piston sealing ring 13; guide ring 14; second piston sealing ring 15; hydraulic medium 16; first end face sealing ring 17; optical fiber 18.

[0022] The realization of the purpose, functional features and advantages of this application will be further explained with reference to the accompanying drawings and embodiments. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0025] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or," "and / or," or "and / or" throughout the text implies three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0026] The following is for reference. Figures 1 to 6 This application describes a hydraulic cylinder and a hydraulic cylinder position self-sensing method according to embodiments thereof. (Refer to...) Figures 1 to 4The first aspect of this application provides a hydraulic cylinder. In some embodiments, the hydraulic cylinder includes a cylinder barrel 4, a piston rod 5, a hydraulic medium 16, a light-emitting component, and a light transmission component 1. The cylinder barrel 4 defines a receiving chamber. The piston rod 5 is movably disposed within the cylinder barrel 4 along a first direction, partially located inside and partially outside the receiving chamber, dividing the receiving chamber into a first chamber and a second chamber. The hydraulic medium 16 fills the receiving chamber and comprises a mixture of a light-transmitting fluid and a colorant. The hydraulic medium 16 is configured to serve both as a transmission medium for the movement of the piston rod 5 and as a filtering medium for filtering polychromatic light. The light-emitting component is connected to the piston rod 5 and moves synchronously with the piston rod 5. The light-emitting component is used to emit polychromatic light. The light transmission component 1 is connected to the cylinder barrel 4 and is used to receive and transmit transmitted light filtered by the hydraulic medium 16. The piston rod 5 is configured to move along a first direction under hydraulic drive to change the optical path length of the hydraulic medium 16 between the light-emitting component and the light transmission component 1, thereby causing the spectral characteristics of the transmitted light to change accordingly with the displacement of the piston rod 5. Specifically, by fixing the light-emitting component to the hydraulically driven piston rod 5, the piston rod 5 reciprocates along the first direction under the pressure of the transmission medium, simultaneously changing the axial distance between the light-emitting component and the light transmission component 1 stationary in the cylinder 4, thereby adjusting the propagation path length of the polychromatic light in the hydraulic medium 16. Based on the selective absorption characteristics of the hydraulic medium 16 for different wavelengths of light, the change in optical path length will cause differences in the attenuation degree of each wavelength component in the transmitted light, ultimately resulting in a definite correspondence between the spectral characteristics of the transmitted light and the displacement of the piston rod 5, realizing the conversion from mechanical displacement to optical signal.

[0027] The hydraulic cylinder of this application fixes the light-emitting component to the piston rod 5, causing the light-emitting element 504 to move synchronously with the piston. Simultaneously, the hydraulic medium 16 filled within the cylinder 4 serves as the light propagation medium, constructing an optical sensing path embedded within the hydraulic cylinder body. Since the hydraulic medium 16 is configured to have both transmission and filtering functions—serving as both the force transmission medium driving the piston rod 5 and the filtering medium selectively attenuating polychromatic light—deep coupling between the actuator and the sensing unit is achieved. This eliminates the need for additional linear displacement sensors or magnetostrictive sensors installed outside the cylinder, simplifying the system structure, improving integration and compactness, and reducing the risk of failure due to complex external sensor installation and wiring.

[0028] During operation, as the piston rod 5 moves along the first direction under hydraulic drive, the relative position between the light-emitting component and the light transmission component 1 changes, causing a corresponding change in the propagation path length of the polychromatic light in the hydraulic medium 16. This, in turn, results in a measurable change in the spectral characteristics of the transmitted light related to the displacement. This displacement detection method based on optical path modulation directly converts mechanical displacement into changes in optical signals. It not only avoids the impact of electromagnetic interference and electrostatic coupling on measurement accuracy and improves operational reliability in strong electromagnetic environments, but also achieves real-time and continuous monitoring of the piston position through the optical properties of the hydraulic medium 16. Closed-loop control can be completed without relying on external coding equipment, effectively improving the intelligence level and response speed of the hydraulic system.

[0029] In some embodiments, the hydraulic cylinder of this application can be applied to the mold closing mechanism of an injection molding machine. When the hydraulic system drives the piston rod 5 to push the template to perform mold opening and closing actions, the light-emitting component integrated at the end of the piston rod 5 moves synchronously. The polychromatic light passes through the dyed hydraulic oil and is received by the light transmission component 1 on the side wall of the cylinder 4. Since the displacement of the piston rod 5 during the mold closing process directly determines the size of the mold gap, the piston position can be accurately determined by monitoring the change of the transmitted light spectrum in real time. There is no need to install an additional magnetostrictive sensor or grating ruler on the outside of the injection molding machine body, avoiding the risk of failure of external sensors under high temperature and high pressure conditions. At the same time, the hydraulic oil itself is used as a filter medium to achieve deep integration of execution and perception, improving the reliability of mold closing accuracy control and the compactness of system integration.

[0030] In some embodiments, the cylinder 4 is a stationary component constituting the main structure of the hydraulic cylinder. It defines an accommodating chamber to fill the hydraulic medium 16, which has both transmission and filtering functions, and provides guidance support for the reciprocating motion of the piston rod 5. At the same time, it serves as a container for the optical path, allowing the polychromatic light emitted by the light-emitting component to be transmitted through the hydraulic medium 16 and then received by the light transmission component 1.

[0031] In some embodiments, the cylindrical cylinder 4 has a light-transmitting portion on its side wall for the light transmission assembly 1 to receive transmitted light, and the internal light signal is transmitted outward through the transparent window.

[0032] In some embodiments, the hydraulic medium 16 is a functional fluid that fills the cavity of the cylinder 4. The hydraulic medium 16 is a mixture of a light-transmitting fluid and a colorant, and has both transmission and filtering properties. It can transmit power under pressure to drive the piston rod 5 to reciprocate, and can selectively attenuate the polychromatic light emitted by the light-emitting component, so that the spectral characteristics of the transmitted light change with the optical path length, thereby realizing the coupling conversion of mechanical displacement and optical signal.

[0033] In some embodiments, the hydraulic medium 16 is a water-soluble liquid-based medium mixed with light-selective transparent components, suitable for environmentally friendly hydraulic systems. In some embodiments, the hydraulic medium 16 is an ester-based medium formulated with broad-spectrum responsive components, suitable for operating environments with a wide temperature range. The hydraulic medium 16 maintains a balance between light transmittance and coloring properties, ensuring stable optical filtering performance while transmitting hydraulic power.

[0034] In some embodiments, the light-emitting component is an active light-emitting unit connected to and moving synchronously with the piston rod 5, used to emit polychromatic light into the hydraulic medium 16. The relative distance between this component and the stationary end light transmission component 1 is changed by the displacement of the piston rod 5, thereby adjusting the filtering length of the polychromatic light in the hydraulic medium 16. The light-emitting component can be directly integrated into the polychromatic light source module at the end of the piston rod 5, achieving rigid synchronous movement with the piston through a compact layout. Alternatively, the light-emitting component can be a split light source with fiber optic transmission, guiding the polychromatic light from the fixed light source to the emission window at the end of the piston rod 5 through a flexible beam transmission, keeping the light-emitting body 504 stationary while ensuring that the emission end moves accordingly.

[0035] In some embodiments, the light transmission component 1 is a stationary optical receiving unit fixedly connected to the cylinder 4, used to capture the transmitted light filtered by the hydraulic medium 16 and transmit it to an external processing unit. By maintaining a relatively stationary relationship with the light-emitting component that moves with the piston rod 5, a stable optical receiving reference is established, so that the spectral changes of the transmitted light can accurately reflect the displacement of the piston rod 5.

[0036] In some embodiments, the optical transmission component 1 directly integrates a receiving module with spectral detection function, realizing on-site acquisition and transmission of optical signals through a built-in photoelectric conversion element. In some embodiments, the optical transmission component 1 adopts a remote transmission structure of flexible optical fiber 18, guiding the transmitted light to a processing device far away from the cylinder 4 through a coupling interface, thus avoiding the influence of high temperature and high pressure environment on the detection element.

[0037] Reference Figure 4 and Figure 5In some embodiments, the light-emitting component includes a light emitter 504 and a first light-aligning component 503. The first light-aligning component 503 has a first light-entry plane and a first light-exit plane, which are arranged opposite to each other and parallel. The first light-entry plane is used to receive polychromatic light, and the first light-exit plane faces the hydraulic medium 16 and is used to guide the polychromatic light to the hydraulic medium 16. By configuring the first light-aligning component 503 in the light-emitting component, the hydraulic cylinder constructs a standardized optical interface using its oppositely arranged and parallel first light-entry plane and first light-exit plane. This allows the polychromatic light emitted by the light emitter 504 to be incident perpendicularly onto the hydraulic medium 16 in the form of a collimated beam, effectively reducing light energy loss and interface reflection caused by light divergence or oblique propagation. This ensures the regularity of the propagation path of the polychromatic light in the hydraulic medium 16, thereby improving the certainty of the correspondence between optical path length and spectral characteristics, and enhancing the accuracy and repeatability of displacement detection.

[0038] Meanwhile, the first optical component 503 serves as the optical coupling interface between the light emitter 504 and the hydraulic medium 16. It protects the light emitter 504 from potential erosion or pressure shocks from direct contact with the hydraulic medium 16, and achieves stable optical contact with the hydraulic medium 16 through its planar light-emitting structure. This avoids interference with the optical path stability caused by liquid surface fluctuations or bubble disturbances due to the reciprocating motion of the piston rod 5, providing structural assurance for reliable acquisition of spectral signals and further enhancing the stability and robustness of the hydraulic cylinder's position self-sensing under dynamic operating conditions. For example, the hydraulic cylinder can be applied to the crystallizer vibration system of a metallurgical continuous casting machine. The light-emitting component is integrated at the end of the vibrating piston rod 5, and the quartz optical plane of the first optical component 503 collimates the polychromatic light emitted by the light emitter 504 into a parallel beam that is perpendicularly incident on the dyeing hydraulic oil. Because the piston rod 5 drives the crystallizer with high-frequency, small-amplitude reciprocating vibration during continuous casting, the liquid surface fluctuates violently and there is a risk of corrosion from high-temperature metal vapor. The first light-emitting component 503 maintains stable optical contact with the hydraulic medium 16 through a planar light-emitting structure, ensuring that the real-time spectral monitoring of vibration displacement is not affected by bubble disturbance. It also protects the light-emitting body 504 from chemical corrosion and thermal shock of the oil through physical isolation, thereby improving the position feedback accuracy and component lifespan of continuous casting vibration control under extreme conditions.

[0039] Reference Figure 4 and Figure 5In some embodiments, the optical transmission component 1 includes an optical fiber 18 and a second optical rectifier 2. The second optical rectifier 2 has a second light-entry plane and a second light-exit plane, which are arranged opposite to and parallel to each other. The second light-entry plane faces the hydraulic medium 16 and is used to receive transmitted light, while the second light-exit plane is used to guide the transmitted light to the optical fiber 18. By configuring the second optical rectifier 2 in the optical transmission component 1, and utilizing its oppositely arranged and parallel second light-entry plane and second light-exit plane, an optical receiving interface corresponding to the first optical rectifier 503 is constructed. This allows the transmitted light filtered by the hydraulic medium 16 to be efficiently coupled into the optical fiber 18 in the form of a collimated beam, effectively reducing light energy loss and coupling efficiency reduction caused by light divergence or incident angle deviation. This ensures the integrity and fidelity of the spectral signal during transmission, thereby improving the reliability and stability of the optical signal transmission from inside the hydraulic cylinder to the external processing unit. The second optical aligning component 2 serves as the optical coupling interface between the hydraulic medium 16 and the optical fiber 18. Its planar light-inlet structure ensures stable optical contact with the hydraulic medium 16, guaranteeing that the received transmitted light is unaffected by liquid surface fluctuations or medium disturbances. Furthermore, its planar light-outlet structure achieves precise alignment with the end face of the optical fiber 18, preventing coupling mismatch caused by mechanical vibration or thermal deformation. This provides structural assurance for accurate acquisition and long-distance transmission of spectral signals. In addition, the fixed connection of the second optical aligning component 2 keeps it relatively stationary with the cylinder 4, forming a stable optical path measurement reference with the first optical aligning component 503, which moves with the piston rod 5. This further enhances the accuracy and repeatability of displacement detection.

[0040] Reference Figure 4 and Figure 5In some embodiments, the piston rod 5 has a first end and a second end opposite to each other along a first direction. The light-emitting component is disposed at the first end, and the light transmission component 1 is connected to the end wall of the cylinder 4. Between the first end and the end wall, a first light-emitting plane, a hydraulic medium 16, and a second light-entering plane are arranged sequentially along the first direction to form an optical path propagating along the first direction. By placing the light-emitting component at the first end of the piston rod 5, connecting the light transmission component 1 to the end wall of the cylinder 4, and sequentially arranging the first light-emitting plane, the hydraulic medium 16, and the second light-entering plane along the first direction between the first end and the end wall, a linear optical path extending axially along the piston rod 5 is constructed. This ensures that the propagation direction of the polychromatic light remains coaxial with the movement direction of the piston rod 5, guaranteeing a strict linear correspondence between the change in optical path length and the displacement of the piston rod 5. This simplifies the displacement calculation model and improves the accuracy and real-time performance of position detection. The arrangement of this optical path fully utilizes the inherent axial structural space of the hydraulic cylinder, integrating the light-emitting component, hydraulic medium 16, and light transmission component 1 along the first direction within the receiving cavity of the cylinder 4. This eliminates the need for additional radial dimensions or external optical accessories, achieving a high degree of spatial integration between the sensing function and the actuator. Furthermore, since the first light-emitting plane and the second light-entry plane, serving as the start and end interfaces of the optical path, are both perpendicular to the first direction, optical axis deviation caused by radial offset or deflection of the piston rod 5 is effectively suppressed. This ensures the stability and consistency of the optical path during the reciprocating motion of the piston rod 5, providing a reliable structural foundation for high-precision displacement self-sensing.

[0041] Reference Figure 4 and Figure 5 In some embodiments, the hydraulic cylinder further includes an oil supply assembly, which includes a first nozzle 3 and a second nozzle 6. The first nozzle 3 connects to a first chamber, and the second nozzle 6 connects to a second chamber. The oil supply assembly is configured to drive the piston rod 5 to move along a first direction by adjusting the volume of hydraulic medium 16 in the first and second chambers. By configuring the oil supply assembly and using the first nozzle 3 and the second nozzle 6 to connect the first and second chambers respectively, a bidirectional hydraulic drive circuit is constructed, enabling the hydraulic medium 16 to act as both an optical filtering medium and a force transmission medium to achieve active driving and position adjustment of the piston rod 5. By adjusting the volume ratio of the hydraulic medium 16 in the two chambers, the displacement and direction of movement of the piston rod 5 along the first direction can be precisely controlled, realizing the reuse of media and coordinated action of optical sensing and hydraulic actuation functions. This eliminates the need for a separate drive mechanism or media circulation system for the sensing system, significantly simplifying the system architecture and reducing energy consumption and maintenance costs.

[0042] Meanwhile, the oil supply configuration of this application deeply embeds the position self-sensing capability of the hydraulic cylinder into the inherent control logic of the hydraulic system. Each displacement of the piston rod 5 is driven by the capacity adjustment of the hydraulic medium 16, and the detection of the displacement depends on the change in the optical properties of the same medium, forming a closed-loop coupling between driving and sensing. This intrinsic correlation ensures a high degree of synchronization between position feedback and execution, eliminates the phase difference between external sensors and the actuator caused by signal transmission delay or mechanical connection gaps, improves the real-time performance and stability of closed-loop control, and provides a structural foundation for the intelligent upgrade of high-precision servo hydraulic systems.

[0043] In some embodiments, the hydraulic cylinder of this application can be applied to the blade pitch control system of a wind turbine generator. The oil supply assembly connects to the two chambers on both sides of the piston through the first oil nozzle 3 and the second oil nozzle 6, respectively. The colored hydraulic oil drives the piston rod 5 to drive the blade bearing to adjust the pitch angle, and also acts as a filter medium to change the optical path between the light-emitting component and the light transmission component 1 with the pitch. When the wind speed changes suddenly and emergency feathering is required, the hydraulic system quickly adjusts the oil volume of the two chambers to drive the piston to move throughout its full stroke. At the same time, the spectral signal provides real-time feedback on the pitch position. There is no need to install easily failing rotary encoders or slip ring actuators in the rotating hub, which realizes the media reuse and closed-loop coordination of pitch drive and position sensing, improving the control response speed and operational reliability of the wind turbine generator under extreme wind conditions.

[0044] Reference Figure 4 and Figure 5 In some embodiments, the hydraulic medium 16 is configured to have high transmittance for the first wavelength of polychromatic light and low transmittance for the second wavelength of polychromatic light. By configuring the hydraulic medium 16 to selectively transmit different wavelength components of polychromatic light, the first wavelength of light maintains high transmittance in the medium while the second wavelength of light is significantly attenuated, thereby forming a discernible spectral difference in the transmitted light. This wavelength-dependent attenuation characteristic provides an optical contrast basis for displacement detection, allowing small changes in optical path length to be translated into significant changes in the power spectrum distribution of transmitted light, improving displacement resolution sensitivity and detection signal-to-noise ratio. Simultaneously, it avoids the shortcomings of single-wavelength light intensity detection, which is susceptible to interference from light source fluctuations or medium turbidity, enhancing the robustness and reliability of position self-sensing under complex working conditions. The selective filtering characteristic of this application enables the decoupling design of the optical and hydraulic functions of the hydraulic medium 16. While maintaining the viscosity and lubrication characteristics required for hydraulic transmission, the medium's spectral response characteristics can be flexibly optimized by adjusting the type and concentration of colorant to adapt to application scenarios with different ranges or accuracy requirements. The dual-wavelength contrast detection mode effectively suppresses the impact of chromaticity drift caused by temperature changes in the hydraulic medium 16 or long-term cyclic use on measurement accuracy. It also offsets the common-mode error of the system through power ratio calculation, providing an optical mechanism to ensure that the hydraulic cylinder maintains stable position detection performance throughout its entire life cycle.

[0045] For example, in the gate lifting system of a large sluice gate hoist, the hydraulic medium 16 uses dyed hydraulic oil that has high transmittance of red light and strong absorption of blue light. When the hoist drives the piston rod 5 to lift the gate for flood discharge, the change in optical path causes a change in the ratio of red to blue light power. By using dual-wavelength comparison detection, the influence of changes in water turbidity during the flood season or the color drift of the medium caused by high summer temperatures is effectively offset. There is no need to install easily corroded magnetic scales or pull rope sensors in the damp and corrosive gate channel, realizing real-time accurate monitoring of the gate position and reliable closed-loop control of flood control scheduling under long stroke and harsh environments.

[0046] Reference Figure 4 and Figure 5 In some embodiments, the cylinder 4 is provided with a light-transmitting section located on the side wall of the cylinder 4. The light-transmitting section is configured to allow transmitted light received by the light transmission component 1 to exit from the hydraulic medium 16. By providing a light-transmitting section on the side wall of the cylinder 4, an optical coupling channel is constructed between the internal optical path of the hydraulic medium 16 and the external light transmission component 1, allowing transmitted light to exit laterally from the hydraulic medium 16 and be received by the light transmission component 1. This lateral light-emitting structure overcomes the limitation that the optical path must coincide with the axial direction of the piston rod 5, allowing the installation position of the light transmission component 1 to be flexibly adjusted according to the system spatial layout, without being limited to the end wall of the cylinder 4. This improves the integration adaptability and assembly convenience of the hydraulic cylinder in complex mechanical structures, while avoiding the adverse effects on sealing performance and structural strength caused by opening optical path interfaces at the end of the piston rod 5 or the end wall of the cylinder 4.

[0047] Furthermore, the light-transmitting configuration of this application allows the light-emitting component and the light transmission component 1 to be arranged in different positions on the cylinder 4, shortening the necessary propagation distance of the optical path in the hydraulic medium 16. This allows for the use of higher concentrations of colorant to enhance filtering contrast while maintaining displacement detection accuracy, or allows the hydraulic medium 16 to have higher turbidity tolerance, broadening the range of optional medium formulations and operating conditions. The sidewall light-transmitting structure facilitates rigid connection and protective encapsulation between the light transmission component 1 and the external processing module, reducing bending loss and breakage risk of the flexible fiber optic lead in dynamic environments, and improving the long-term stability of optical signal transmission and the convenience of system maintenance.

[0048] In some embodiments, the hydraulic cylinder further includes a processing module, which is communicatively connected to the optical transmission component 1. The processing module is configured to: acquire the spectral signal of the transmitted light; and calculate the displacement of the piston rod 5 relative to the cylinder 4 based on the power ratio of different wavelengths of light in the spectral signal.

[0049] The processing module acquires the spectral signal of transmitted light and extracts the power ratio of different wavelengths. Using the deterministic relationship between this ratio and the optical path length, it calculates the displacement of piston rod 5. This effectively eliminates the impact of common-mode factors such as light source intensity fluctuations, medium temperature changes, and optical component aging on measurement accuracy, improving the long-term stability and anti-interference capability of position detection. Simultaneously, it simplifies the signal processing burden of the external control system, enabling the hydraulic cylinder to independently output position information. Furthermore, the configuration of the processing module allows the displacement information output by the hydraulic cylinder to be directly used for closed-loop control without relying on complex calculations by external encoders or host computers. Through the calculation and processing of the spectral power ratio, the system has adaptive compensation capability for initial deviations or long-term decay of the colorant concentration in the hydraulic medium 16, broadening the allowable range of medium maintenance cycles and reducing calibration and maintenance costs throughout the entire lifecycle.

[0050] Reference Figure 6 The second aspect of this application provides a hydraulic cylinder position self-sensing method, applied to the hydraulic cylinder of any of the preceding claims. The hydraulic cylinder position self-sensing method includes: S101: Inject hydraulic medium 16 into cylinder 4. Hydraulic medium 16 includes a mixture of light-transmitting fluid and colorant. Hydraulic medium 16 serves as both a transmission medium and a light filtering medium. S103: Activate the light-emitting component to make it emit polychromatic light, which passes through the hydraulic medium 16 to form transmitted light; S105: Receives transmitted light and acquires its spectral signal; S107: Adjust the capacity of the hydraulic medium 16 in different chambers of the cylinder 4 to drive the piston rod 5 to move relative to the cylinder 4, so as to change the optical path length of the polychromatic light in the hydraulic medium 16, thereby changing the spectral characteristics of the transmitted light. S109: Obtain the displacement of piston rod 5 based on the change in spectral characteristics.

[0051] Specifically, in step S101, a hydraulic medium 16 with both light transmittance and coloring properties is injected into the cylinder 4, achieving physical multiplexing of the transmission medium and the optical filtering medium. This allows a single medium to simultaneously perform the dual functions of force transmission and optical modulation, eliminating the need for an additional sealed cavity and circulation maintenance system required for a separate sensing medium. This significantly simplifies the structural complexity and manufacturing cost of the hydraulic cylinder and provides a functional basis for subsequent optical detection built into the actuator. In step S103, the light-emitting component is activated to generate polychromatic light. This polychromatic light serves as an information carrier entering the hydraulic medium 16, providing a broad-spectrum optical reference for displacement detection. This enables subsequent spectral analysis to have a computational basis for multi-wavelength comparison, enhancing the information redundancy and anti-interference capability of the detection system. In step S105, the transmitted light is received and its spectral signal is acquired. The optical information is converted into processable electrical signal data, establishing a data interface between the internal physical state of the hydraulic cylinder and the external information system, realizing the digital extraction and transmission of displacement information. Step S107 drives the piston rod 5 to move by adjusting the capacity of the hydraulic medium 16 in different chambers. This action not only embodies the function of the hydraulic cylinder but also simultaneously changes the propagation path length of polychromatic light in the medium, coupling mechanical displacement with optical changes. This ensures real-time synchronization between the driving action and the sensing feedback, eliminating signal delay and mechanical gap errors between traditional external sensors and actuators. Step S109 calculates the displacement based on the change in spectral characteristics, converting the change in optical signal into quantifiable position information. This completes the information processing stage of the self-sensing closed loop, enabling the hydraulic cylinder to independently complete position monitoring and feedback output without external coding equipment, thus improving the system's integration, response speed, and intelligence level.

[0052] In some embodiments, activating the light-emitting component includes: emitting polychromatic light comprising a first wavelength and a second wavelength through the light-emitting component; Acquiring spectral signals includes: detecting the power ratio of the first wavelength light to the second wavelength light in the transmitted light; The displacement calculation includes: calculating the displacement of piston rod 5 based on the linear relationship between the natural logarithm of the power ratio and the optical path length.

[0053] Specifically, by limiting the emission of polychromatic light containing both a first wavelength and a second wavelength from the activated light-emitting component, an optical basis for dual-wavelength contrast detection is established. This allows the first wavelength to serve as a reference standard, while the second wavelength acts as a sensitive variable in displacement calculation. This effectively overcomes the shortcomings of single-wavelength light intensity detection, which is susceptible to interference from light source fluctuations, medium turbidity, and stray light from the environment, thus improving the signal-to-noise ratio and long-term stability of displacement detection. By detecting the power ratio of the first and second wavelengths in the transmitted light, absolute light intensity measurement is converted into a relative ratio calculation. This eliminates the influence of common-mode factors such as light source aging, power supply voltage fluctuations, and optical window contamination on the measurement results, enabling the system to adaptively compensate for unavoidable changes in operating conditions during hydraulic cylinder operation. By calculating the displacement based on the linear relationship between the natural logarithm of the power ratio and the optical path length, an analytical mathematical model was established. This transformed complex spectral changes into simple linear operations, reducing the algorithm complexity and computational load of the processing module. This enabled the displacement calculation to be completed in real time within the embedded system, meeting the stringent requirements of high-speed hydraulic servo control for feedback delay. At the same time, the determinism of this linear relationship ensured the consistency of displacement detection accuracy across the entire range, avoiding the piecewise errors and calibration workload caused by nonlinear calibration. This provided a standardized technical interface for the large-scale manufacturing and application maintenance of hydraulic cylinders.

[0054] Below, refer to Figures 1 to 6 This paper systematically illustrates the hydraulic cylinder and its self-sensing position method according to a specific embodiment. The hydraulic cylinder of this application deeply integrates dual-wavelength spectrophotometry with hydraulic transmission technology, achieving structural integration and functional reuse of the actuator and sensing unit. The hydraulic cylinder utilizes the hydraulic medium 16 simultaneously as both a force transmission medium and a light filtering medium. By changing the optical path length through the displacement of the piston rod 5, a deterministic correspondence is established between the spectral characteristics of the transmitted light and the displacement, thereby achieving real-time self-sensing of the piston position without relying on external sensors.

[0055] The hydraulic cylinder includes core components such as a cylinder barrel 4, a piston rod 5, a hydraulic medium 16, a light-emitting component, a light transmission component 1, and a processing module. The cylinder barrel 4 defines a receiving chamber, providing a structural boundary for the storage of the hydraulic medium 16 and the movement of the piston rod 5. The piston rod 5 is movably inserted through the cylinder barrel 4 along a first direction, dividing the receiving chamber into a first chamber and a second chamber, achieving bidirectional hydraulic drive. The hydraulic medium 16, filled within the receiving chamber, is a mixture of a light-transmitting fluid and a colorant. It serves both as the transmission medium driving the piston rod 5 and as a filter medium selectively attenuating polychromatic light, embodying the core design concept of functional reuse. The light-emitting component is connected to the piston rod 5 and moves synchronously with it, emitting polychromatic light containing both a first wavelength and a second wavelength. The light transmission component 1 is connected to the light-transmitting portion of the end wall or side wall of the cylinder barrel 4, receiving and transmitting the transmitted light filtered by the hydraulic medium 16. The processing module is communicatively connected to the light transmission component 1, acquiring spectral signals and calculating displacement based on the power ratio of the two wavelengths.

[0056] The optical path of the hydraulic cylinder in this application is arranged along the axial direction of the piston rod 5. The first light-emitting component 503 in the light-emitting assembly has a first light-entry plane and a first light-exit plane that are relatively parallel. The second light-emitting component 2 in the light transmission assembly 1 has a second light-entry plane and a second light-exit plane that are relatively parallel. The first light-exit plane, the hydraulic medium 16, and the second light-entry plane are arranged sequentially between the two light-emitting components along the first direction to form a standardized linear optical path. The oil supply assembly connects the first chamber and the second chamber through the first oil nozzle 3 and the second oil nozzle 6, respectively. By adjusting the capacity of the hydraulic medium 16 in the two chambers, the piston rod 5 is driven to reciprocate, thereby synchronously changing the optical path length between the light-emitting assembly and the light transmission assembly 1.

[0057] Specifically, in some embodiments, the cylinder 4 serves as the main load-bearing component, forming a cylindrical receiving chamber inside. One end of the cylinder 4 is closed by a cylinder end cap 9, and the other end allows the piston rod 5 to extend. A cylinder sealing ring 12 is provided between the cylinder end cap 9 and the cylinder 4 to ensure the sealing of the receiving chamber. The piston rod 5 penetrates the cylinder 4 along a first direction, and the portion of the piston rod 5 located within the receiving chamber is connected to a piston support frame 506. A first piston sealing ring 13 and a second piston sealing ring 15 are installed on the piston support frame 506 to achieve pressure isolation between the first and second chambers. A guide ring 14 is also provided on the outer edge of the piston support frame 506 to ensure the coaxiality and stability of the reciprocating motion of the piston rod 5. A guide sleeve 7 is fitted onto the portion of the piston rod 5 extending out of the cylinder 4. The guide sleeve 7 is embedded in a pressure ring sleeve 8, and the pressure ring sleeve 8 is fixedly connected to the end of the cylinder 4. A rod end sealing ring 11 is provided between the guide sleeve 7 and the piston rod 5 to prevent the hydraulic medium 16 from leaking out. A dustproof ring 10 is also provided on the outside of the rod end sealing ring 11 to prevent the intrusion of external particles. The front end cap of the piston rod 5 is connected to the end of the piston rod 5 located in the receiving chamber. A first light-aligning component 503 is installed on the surface of the front end cap facing the hydraulic medium 16. The first light-emitting plane of the first light-aligning component 503 faces the hydraulic medium 16, and the first light-entry plane faces the light-emitting element 504 installed in the front end cap. The light-emitting element 504 is encapsulated and fixed by an insulating sealing plug 505 to ensure electrical safety and optical alignment accuracy. A second end face sealing ring 502 is provided between the front end cap of the piston rod 5 and the piston support frame 506 to maintain the pressure boundary between the chambers.

[0058] The optical transmission assembly 1 is mounted on the other end wall of the cylinder 4, and includes a second light-guiding component 2 and an optical fiber 18. The second light-entry plane of the second light-guiding component 2 faces the hydraulic medium 16, and the second light-exit plane is connected to the incident end face of the optical fiber 18. The optical fiber 18 transmits the transmitted light to a processing module outside the cylinder 4. A first end face sealing ring 17 is disposed between the second light-guiding component 2 and the end wall of the cylinder 4 to ensure the sealing reliability at the optical interface.

[0059] In practical use, the hydraulic cylinder is first injected into the cylinder 4 through the first nozzle 3 and the second nozzle 6, filling the entire receiving chamber. The light emitter 504 is activated, ensuring that the polychromatic light it generates propagates through the first light-emitting plane of the first light-forming component 503 into the hydraulic medium 16. The light rays exit from the boundary of the hydraulic medium 16, forming transmitted light. This transmitted light travels from the second light-entry plane of the second light-forming component 2 to the optical fiber 18, where the corresponding spectral signal is acquired by the light transmission component 1. Adjusting the volume of the hydraulic medium 16 in the first and second chambers of the cylinder 4 causes relative movement between the piston rod 5 and the cylinder 4, extending the driving end of the hydraulic cylinder to drive an external load. This relative movement alters the optical path length of the hydraulic medium 16 between the first light-emitting plane and the second light-entry plane, resulting in a change in the spectral characteristics acquired by the optical fiber 18. By coupling displacement and optical signals, a self-sensing hydraulic cylinder design is achieved.

[0060] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural transformations made based on the content of the specification and drawings of this application under the concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A hydraulic cylinder characterized by, include: The cylinder defines the receiving chamber; A piston rod is movably disposed in the cylinder along a first direction, the piston rod being partially located inside the receiving chamber and partially located outside the receiving chamber, the piston rod dividing the receiving chamber into a first chamber and a second chamber; A hydraulic medium is filled in the receiving cavity. The hydraulic medium comprises a mixture of a light-transmitting fluid and a colorant. The hydraulic medium is configured to serve both as a transmission medium for moving the piston rod and as a filtering medium for filtering polychromatic light. A light-emitting component is connected to the piston rod, and the light-emitting component moves synchronously with the piston rod. The light-emitting component is used to emit polychromatic light. An optical transmission component is connected to the cylinder, and the optical transmission component is used to receive and transmit transmitted light filtered by the hydraulic medium. The piston rod is configured to move along the first direction under hydraulic drive to change the optical path length of the hydraulic medium between the light-emitting component and the light transmission component, thereby causing the spectral characteristics of the transmitted light to change accordingly with the displacement of the piston rod.

2. The hydraulic cylinder according to claim 1, characterized in that, The light-emitting component includes a light-emitting body and a first light-forming component. The first light-forming component has a first light-inlet plane and a first light-outlet plane. The first light-inlet plane and the first light-outlet plane are arranged opposite to each other and parallel. The first light-inlet plane is used to receive the polychromatic light. The first light-outlet plane is arranged facing the hydraulic medium and is used to guide the polychromatic light to the hydraulic medium.

3. The hydraulic cylinder according to claim 2, characterized in that, The optical transmission component includes an optical fiber and a second optical rectifier. The second optical rectifier has a second light-inlet plane and a second light-outlet plane. The second light-inlet plane and the second light-outlet plane are arranged opposite to each other and parallel. The second light-inlet plane faces the hydraulic medium. The second light-inlet plane is used to receive the transmitted light, and the second light-outlet plane is used to guide the transmitted light to the optical fiber.

4. The hydraulic cylinder according to claim 3, characterized in that, The piston rod has a first end and a second end opposite to each other along the first direction, the light-emitting component is disposed at the first end, and the light transmission component is connected to the end wall of the cylinder. Specifically, between the first end and the end wall, the first light-emitting plane, the hydraulic medium, and the second light-entering plane are arranged sequentially along the first direction to form an optical path that propagates along the first direction.

5. The hydraulic cylinder according to claim 1, characterized in that, The hydraulic cylinder further includes an oil supply assembly, which includes a first oil nozzle and a second oil nozzle, wherein the first oil nozzle is connected to the first chamber and the second oil nozzle is connected to the second chamber. The oil supply assembly is configured to drive the piston rod to move along the first direction by adjusting the capacity of the hydraulic medium in the first chamber and the second chamber.

6. The hydraulic cylinder according to claim 1, characterized in that, The hydraulic medium is configured to have high transmittance for the first wavelength of the polychromatic light and low transmittance for the second wavelength of the polychromatic light.

7. The hydraulic cylinder according to claim 1, characterized in that, The cylinder is provided with a light-transmitting part, which is located on the side wall of the cylinder. The light-transmitting part is configured to allow the transmitted light received by the light transmission component to be transmitted out from the hydraulic medium.

8. The hydraulic cylinder according to any one of claims 1 to 7, characterized in that, The hydraulic cylinder further includes a processing module, which is communicatively connected to the optical transmission component. The processing module is configured to: Obtain the spectral signal of the transmitted light; The displacement of the piston rod relative to the cylinder is calculated based on the power ratio of different wavelengths of light in the spectral signal.

9. A method for self-sensing the position of a hydraulic cylinder, characterized in that, The hydraulic cylinder position self-sensing method, applied to any one of claims 1 to 8, comprises: Hydraulic medium is injected into the cylinder, the hydraulic medium comprising a mixture of a light-transmitting fluid and a colorant, the hydraulic medium serving as both a transmission medium and a light filtering medium; The light-emitting component is activated, causing it to emit polychromatic light, which passes through the hydraulic medium to form transmitted light. Receive the transmitted light and acquire its spectral signal; Adjusting the volume of the hydraulic medium in different chambers within the cylinder drives the piston rod to move relative to the cylinder, thereby changing the optical path length of the polychromatic light in the hydraulic medium and thus altering the spectral characteristics of the transmitted light. The displacement of the piston rod is obtained based on the change in the spectral characteristics.

10. The hydraulic cylinder position self-sensing method according to claim 9, characterized in that, The step of activating the light-emitting component includes: emitting polychromatic light comprising a first wavelength and a second wavelength through the light-emitting component; and / or, The step of acquiring the spectral signal includes: detecting the power ratio of the first wavelength light to the second wavelength light in the transmitted light; and / or, The step of calculating the displacement includes: calculating the displacement of the piston rod based on the linear relationship between the natural logarithm of the power ratio and the optical path length.

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