Branched chain sensing rope suspension parallel robot embedded with optical waveguide sensor

Abstract

The invention discloses a branched chain sensing rope suspension parallel robot embedded with optical waveguide sensing, and belongs to the field of parallel robots. Comprising a rack, and a lead screw nut seat capable of ascending and descending and a fixed platform fixed in position are arranged on the rack; a plurality of supporting seats which are uniformly distributed in the circumferential direction are hinged to the fixed platform, and an umbrella stand connecting rod is hinged between the lead screw nut seat and each supporting seat; a supporting seat is arranged on the fixed platform, a sliding block capable of sliding in the length direction of the supporting seat is arranged on the supporting seat, a movable platform is arranged below the fixed platform, a fiber-reinforced optical waveguide sensor is arranged between the movable platform and the sliding block, and the two ends of the fiber-reinforced optical waveguide sensor are connected with the movable platform and the sliding block through universal joints respectively. A Kevlar fiber tube is arranged on the outer side of a fiber core of the sensor, the inner side and the outer side of the Kevlar fiber tube are filled with silica gel, and an LED and a PD are arranged at the two ends of the fiber core respectively. A sensor is used for replacing a traditional rope to form an optical waveguide rope, and the parallel robot is endowed with the large-range tactile perception capacity.

Description

Technical Field

[0001] This invention belongs to the field of parallel robots, specifically relating to a branch sensing rope suspended parallel robot with embedded optical waveguide sensing. Background Technology

[0002] Rope-driven parallel robots are a subclass of parallel manipulators. Their branch structures use ropes instead of rigid rods. By adjusting the rope length and tension, the system can achieve the desired end-effector pose and the required force. Compared to parallel robots driven by rigid links, rope-driven parallel robots have advantages in interactive operations due to their lightweight structure, large workspace, and low inertia.

[0003] However, due to the wide range and dynamic nature of ropes in space, strict and precise monitoring of the robot and its environment is usually required to ensure system safety and avoid unpredictable behavior (especially preventing direct contact between the rope and the operator). This high dependence on external monitoring significantly limits the range of movement and positional flexibility of both the operator and the robot. In the field of human-rope interaction, collisions between humans and ropes have become a key challenge. Although existing research has explored rope manipulation, entanglement control, and collaborative handling, it has largely focused on issues such as tension control, path planning, or vibration suppression. System studies that truly treat ropes as a distributed tactile sensing medium are still relatively scarce. Therefore, endowing ropes with sensing capabilities and exploring the possibility of safe interaction between ropes and the environment (including humans) without completely avoiding contact will significantly improve the applicability, compliance, and collaborative capabilities of rope-driven parallel robots, and has important research significance and broad application prospects.

[0004] During collisions or interactions, the state of the rope, such as tension, bending deformation, and the condition of the rope being struck, needs to be sensed and monitored in real time to enable timely decision-making. Existing rope sensing technologies mainly focus on rope tension sensing. Specific implementations include tension sensors mounted on rope drums, tension sensors placed at the connection between the moving platform and the rope, and another common approach is to install multi-dimensional force sensors at the end of the moving platform. If further determination of the rope's force location or direction is required, a vision system must be integrated. Using multiple discrete sensors for monitoring makes it difficult to comprehensively capture the force or deformation of the entire rope. The collected data requires complex calculations and fusion processing, resulting in poor collision detection performance, limited system response speed, lack of awareness of rope-environment interactions, and high costs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a branched sensing rope suspended parallel robot with embedded optical waveguide sensing, thus solving the problems in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions: A fiber-reinforced optical waveguide sensor has a columnar structure, including a fiber core located at the center, a Kevlar fiber tube disposed on the outside of the fiber core, and silicone wrapped on the outside of the Kevlar fiber tube; the inside of the Kevlar fiber tube is also filled with silicone and wraps the fiber core; a light-emitting diode and a photodiode are respectively disposed at both ends of the fiber core; the two ends of the fiber-reinforced optical waveguide sensor are sealed with sealing silicone.

[0007] Furthermore, the number of fiber cores is 1 to 3, and they are arranged in a circular array.

[0008] Furthermore, the fiber core is made of transparent glycerin, and the diameter of the fiber core is 2mm.

[0009] Furthermore, when the number of fiber cores is 1, the outer diameter of the Kevlar fiber tube is 4 mm and the thickness is 0.6 mm; the outer diameter of the sensor is 6 mm. When the number of fiber cores is 2, the outer diameter of the Kevlar fiber tube is 8 mm and the thickness is 0.6 mm; the outer diameter of the sensor is 10 mm. When the number of fiber cores is 3, the outer diameter of the Kevlar fiber tube is 10 mm and the thickness is 0.6 mm; the outer diameter of the sensor is 12 mm.

[0010] The aforementioned fiber-reinforced optical waveguide sensor is used as a rope in the construction of rope-driven parallel robots.

[0011] A branch-chain sensing rope suspended parallel robot with embedded optical waveguide sensing includes a frame, a liftable screw nut seat and a fixed platform; multiple circumferentially evenly distributed support seats are hinged on the fixed platform, and an umbrella frame connecting rod is provided between the screw nut seat and each support seat, with the two ends of the umbrella frame connecting rod being hinged to the screw nut seat and the support seat respectively. The support base is provided with a slider that can slide along its length. A moving platform is provided below the fixed platform. The aforementioned fiber-reinforced optical waveguide sensor is provided between the moving platform and the slider. Both ends of the fiber-reinforced optical waveguide sensor are connected to the moving platform and the slider respectively through universal joints.

[0012] Furthermore, a ball screw slide module is installed on the top of the frame. The ball screw slide module includes a motor A, a fixed shaft seat, a lead screw, a lead screw nut seat, and two optical shafts. The motor A and the fixed shaft seat are fixed on the top of the frame. The lead screw passes through the fixed shaft seat and is installed at the output end of the motor A through a coupling. The lead screw nut seat is fitted onto the lead screw. The two optical shafts pass through the lead screw nut seat through sleeves, and their ends are fixed to the fixed shaft seat and the fixed platform, respectively. When the motor drives the lead screw to rotate, it can drive the lead screw nut seat to move up and down along the optical shaft axis.

[0013] Furthermore, a guide rail is fixed on the support base, the slider slides on the guide rail, and a motor is provided on the support base to drive the slider to slide along the guide rail.

[0014] The above-mentioned parallel robots are used in human-computer interaction operations.

[0015] The above-mentioned parallel robots are used in shaft and hole assembly operations.

[0016] The beneficial effects of this invention are: 1. The fiber-reinforced optical waveguide sensor provided by this invention innovatively embeds Kevlar fibers into the internal structure of a silicone tube, maintaining the high flexibility of traditional optical waveguide sensors while effectively improving the tensile strength of the sensor. Simultaneously, this sensor possesses advantages such as high sensitivity, good repeatability, and strong anti-interference capability, ensuring its reliability and stability under complex operating conditions.

[0017] 2. This invention applies a fiber-reinforced optical waveguide sensor to a variable-structure rope-driven parallel robot, replacing the traditional rope to form an optical waveguide rope, thereby giving the parallel robot a wide range of tactile perception capabilities and enhancing the robot's application value in intelligence and human-computer interaction.

[0018] 3. The optical waveguide branch rope of the present invention has a sensing function itself. It can realize real-time monitoring of the rope status (including bending deformation, tension, etc.) without the need for additional external sensors. Through calibration, it can accurately determine the direction and magnitude of the collision force. In addition, the rope can directly realize contact-type force interaction and cooperation, which significantly simplifies the system structure and reduces the integration complexity.

[0019] 4. The robot in this invention has a fast response speed; by using an optical waveguide sensor as the main body / built-in sensor, it can acquire rope force data more comprehensively and evenly, thereby quickly determining the direction and magnitude of the collision force and timely adjusting the force / position control, achieving a more efficient and reliable interactive response effect. Attached Figure Description

[0020] 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, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart illustrating the preparation process of the silicone solution and fiber-reinforced silicone tube of the present invention. Figure 2 These are schematic diagrams of the single, dual, and triple-cavity fiber-reinforced optical waveguide sensor structures of the present invention; Figure 3 This is a schematic diagram of the fiber-reinforced optical waveguide sensor of the present invention; Figure 4 This is a schematic diagram illustrating the principle of force direction differentiation in the dual-cavity fiber-reinforced optical waveguide sensor of the present invention. Figure 5 These are force simulation diagrams of the single, double, and triple cavity fiber-reinforced optical waveguide sensors of the present invention; Figure 6 This invention relates to an experimental apparatus for characterizing the performance of fiber-reinforced optical waveguide sensors. Figure 7 These are performance figures of the single, double, and triple cavity fiber-reinforced optical waveguide sensors of the present invention under different force directions; Figure 8 This is an overall structural diagram of the parallel robot of the present invention; Figure 9 This is a structural diagram of the parallel robot body of the present invention; Figure 10 This is a simplified diagram of the parallel robot mechanism of the present invention; Figure 11 These are the platform structure parameters of the parallel robot of the present invention; Figure 12 This is a simplified kinematic diagram of the i-th branch of the parallel robot of the present invention; Figure 13 This is a block diagram of the parallel robot control system of the present invention; Figure 14 This is a flowchart of the collision detection method under the normal operating mode of the present invention; Figure 15 This is the interactive flowchart of the present invention.

[0022] In the picture: 1-Single-cavity fiber-reinforced optical waveguide sensor; 11-First LED; 12-First silicone tube; 13-First fiber core; 14-First PD; 121-First Kevlar fiber tube; 122-First silicone. 2-Dual-cavity fiber-reinforced optical waveguide sensor; 211-Second LED; 212-Third LED; 22-Second silicone tube; 23-Second fiber core; 241-Second PD; 242-Third PD; 221-Second Kevlar fiber tube; 222-Second silicone. 3-Triple-cavity fiber-reinforced optical waveguide sensor; 311-Fourth LED; 312-Fifth LED; 313-Sixth LED; 32-Third silicone tube; 33-Third fiber core; 341-Fourth PD; 342-Fifth PD; 343-Sixth PD; 321-Third Kevlar fiber tube; 322-Third silicone. 4-Experimental apparatus for characterizing the performance of fiber-reinforced optical waveguide sensors; 41-Perforated plate; 42-Fiber-reinforced optical waveguide sensor; 43-Base; 44-Universal joint; 45-Connector; 46-Dovetail slide; 47-Pressure sensor; 48-Indenter; 49-Servo motor. 5-Parallel robot; 51-Frame; 52-Moving platform; 53-Universal joint; 54-Three-cavity fiber-reinforced optical waveguide rope; 55-Synchronous belt drive slide module; 551-Motor B; 552-Support seat; 553-Guide rail; 554-Slider; 56-Ball screw slide module; 561-Motor A; 562-Fixed bearing seat; 563-Screw; 564-Optical axis; 565-Screw nut seat; 57-Umbrella frame connecting rod; 58-Fixed platform; 59-Hinge. Detailed Implementation

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

[0024] It should be noted that the silicone used in this application consists of Agent A (base silicone) and Agent B (curing agent), model E660, and its refractive index is approximately 1.41 after mixing, stirring, and coloring. The glycerol used has a purity of over 99.7% and a refractive index of approximately 1.48. This meets the requirement that the refractive index of the core layer (glycerol) is greater than that of the cladding material (silicone). The Kevlar fiber used is 200D, which possesses characteristics such as low elongation, high strength, and corrosion resistance, fully meeting the application requirements.

[0025] Furthermore, all the light-emitting diodes (LEDs) used have the same parameters: specifically, they emit emerald green light, have a luminous intensity of 20,000 mcd, a wavelength of 525 nm, a diameter of 3 mm, and are edgeless round-headed. All the photodiodes (PDs) used also have the same parameters: specifically, a peak wavelength of 550 nm, a diameter of 3 mm, and are edgeless round-headed. By using photodiodes with wavelengths close to those of the LEDs and emitting light at maximum power, the signal strength of the light in a longer cavity can be enhanced.

[0026] Fiber-reinforced optical waveguide sensors with single-cavity structures can only determine whether a force has been applied and whether bending deformation has occurred. Determining the direction of force requires combining the results from multiple single-cavity fiber-reinforced optical waveguide sensors, making the algorithm quite complex. Dual-cavity fiber-reinforced optical waveguide sensors can only distinguish between two directions on a single plane; similarly, determining the direction of force requires comprehensive analysis. In contrast, triple-cavity fiber-reinforced optical waveguide sensors can theoretically deduce bending in any direction, reducing algorithm complexity and offering better anti-interference capabilities.

[0027] Therefore, three types of fiber-reinforced optical waveguide sensors with cavity structures were fabricated for comparison or reference. Their fabrication processes are the same, but the corresponding molds need to be printed according to the diameter of the sensor and the cavity hole position.

[0028] Example 1 This embodiment provides a method for preparing fiber-reinforced silicone tubing, the process of which is as follows: Figure 1 As shown, it includes: like Figure 1 As shown in a, when preparing the silica gel solution, agent A and agent B are poured into beakers in a 1:1 mass ratio, and stirred thoroughly along the bottom edge of the beaker with a flat depressor for 1 minute.

[0029] Add black silica gel colorant to the silica gel solution at a mass ratio of 20:1 and continue stirring for 1 minute. Next, place the beaker containing the well-mixed silica gel solution into a vacuum-sealed container and let it stand for 3 minutes under a negative pressure of -100 kPa. When removing it, observe whether the air bubbles have been completely eliminated. Finally, slowly extract the de-air-forming silica gel solution with a syringe for later use.

[0030] For the preparation of single-cavity fiber-reinforced silicone tubing, the end of a round rod with a diameter of 2 mm and a length of 520 mm, and the end of a Kevlar fiber tube with an outer diameter of 4 mm, a length of 520 mm, and a thickness of 0.6 mm are first positioned at the bottom of the mold using positioning components. The round rod helps the silicone form the cavity, while the Kevlar fiber tube enhances tensile strength.

[0031] For the preparation of dual-cavity fiber-reinforced silicone tubes, the ends of two round rods with a diameter of 2 mm and a length of 520 mm, and the end of a Kevlar fiber tube with an outer diameter of 8 mm, a length of 520 mm, and a thickness of 0.6 mm are first positioned at the bottom of the mold using positioning parts.

[0032] For the preparation of the three-cavity fiber-reinforced silicone tube, the ends of three round rods with a diameter of 2 mm and a length of 520 mm, and the end of a Kevlar fiber tube with an outer diameter of 10 mm, a length of 520 mm, and a thickness of 0.6 mm are first positioned at the bottom of the mold using positioning parts.

[0033] Figure 1 Figure b illustrates the silicone tube molding process. After bottom positioning, the silicone solution is slowly injected into the mold along the top edge using a syringe to prevent air from being trapped during injection. Finally, the mold is sealed with a printed top positioning part, ensuring the fiber tube is taut. Furthermore, to prevent the mixed silicone solution from solidifying and causing injection failure, the injection must be completed within 20 minutes. After the mold filled with silicone solution is left to stand at 25°C for 4 hours, the round rod is slowly withdrawn to prevent damage to the inner wall of the cavity. Finally, the mold is disassembled, and the finished silicone tube is removed.

[0034] Example 2 This embodiment provides three fiber-reinforced optical waveguide sensors with different cavity structures: single-cavity, dual-cavity, and triple-cavity fiber-reinforced optical waveguide sensors.

[0035] like Figure 2 As shown in Figure a, a first fiber core 13 is disposed at the center of the fiber-reinforced optical waveguide sensor 1 with a single cavity structure. The first fiber core 13 is made of transparent glycerin, and a first silicone tube 12 is wrapped around the outside of the first fiber core 13. The first silicone tube 12 includes a first Kevlar fiber tube 121, and first silicone 122 is disposed on both the inner and outer sides of the first Kevlar fiber tube 121. A first LED 11 and a first PD 14 are respectively disposed at both ends of the fiber core 13. In this embodiment, the diameter of the first fiber core 13 is 2 mm; the outer diameter of the first Kevlar fiber tube 121 is 4 mm and the thickness is 0.6 mm; the outer diameter of the fiber-reinforced optical waveguide sensor 1 with a single cavity structure is 6 mm.

[0036] The specific fabrication process of the single-cavity fiber-reinforced optical waveguide sensor 1 is as follows: First, use a syringe to draw a sufficient amount of transparent glycerin and inject it into the cavity of the first silicone tube 12 until it overflows and expels air. Insert the head end of the first LED 11 with soldered wires into one end of the first silicone tube 12, and then insert the head end of the first PD 14 with soldered wires into the other end, with both ends penetrating 3-5mm into the first silicone tube. Finally, seal both ends with black sealing silicone. like Figure 2As shown in b, the dual-cavity fiber-reinforced optical waveguide sensor 2 includes two second fiber cores 23 (made of transparent glycerol) that are symmetrical about the center. A second Kevlar fiber tube 221 is disposed on the outside of the two second fiber cores 23. The outside of the second Kevlar fiber tube 221 is wrapped with a second silicone 222. The inside of the second Kevlar fiber tube 221 is also filled with a second silicone 222 and wraps the two second fiber cores 23 (the second Kevlar fiber tube 221 and the second silicone 222 constitute the second silicone tube 22). A second LED 211 and a third LED 212 are respectively disposed on one side of the two second fiber cores 23, and a second PD 241 and a third PD 242 are respectively disposed on the other side.

[0037] In this embodiment, the diameter of the second fiber core 23 is 2 mm; the outer diameter of the second Kevlar fiber tube 221 is 8 mm and the thickness is 0.6 mm; the outer diameter of the fiber-reinforced optical waveguide sensor 2 with dual cavity structure is 10 mm.

[0038] The specific fabrication process of the dual-cavity fiber-reinforced optical waveguide sensor 2 is as follows: First, use a syringe to draw a sufficient amount of transparent glycerin and inject it into the two cavities of the second silicone tube 22 until air overflows and is expelled. Insert the ends of the second LED 211 and the third LED 212 with soldered wires into one end of the second silicone tube 22, and then insert the ends of the second PD 241 and the third PD 242 with soldered wires into the other end, with both ends penetrating 3-5mm into the silicone tube; finally, seal both ends with black sealing silicone.

[0039] like Figure 3 As shown in c, the three-cavity fiber-reinforced optical waveguide sensor 3 includes: three third fiber cores 33 (made of transparent glycerin) located at the center and arranged in a circular array; a third Kevlar fiber tube 321 is disposed on the outside of the three third fiber cores 33; a third silicone 322 is wrapped on the outside of the third Kevlar fiber tube 321, and the inside of the third Kevlar fiber tube 321 is also filled with third silicone 322 and wrapped around the three third fiber cores 33 (the third Kevlar fiber tube 321 and the third silicone 322 constitute the third silicone tube 32); a fourth LED 311, a fifth LED 312 and a sixth LED 313 are respectively disposed on one side of the three third fiber cores 33, and a fourth PD 341, a fifth PD 342 and a sixth PD 343 are respectively disposed on the other side.

[0040] In this embodiment, the diameter of the third fiber core 33 is 2 mm; the outer diameter of the third Kevlar fiber tube 321 is 10 mm and the thickness is 0.6 mm; the outer diameter of the three-cavity fiber-reinforced optical waveguide sensor 3 is 12 mm.

[0041] The specific fabrication process of the three-cavity fiber-reinforced optical waveguide sensor 3 is as follows: First, use a syringe to draw a sufficient amount of transparent glycerin 33 and inject it into the three cavities of the third silicone tube 32 until it overflows and expels air. Insert the ends of the fourth LED 311, fifth LED 312, and sixth LED 313 (with soldered wires) into one end of the silicone tube, and then insert the ends of the fourth PD 341, fifth PD 342, and sixth PD 343 (with soldered wires) into the other end, with both ends penetrating 3-5 mm into the silicone tube. Finally, seal both ends with black sealing silicone.

[0042] Example 3 This embodiment illustrates the working principle and finite element simulation analysis of a fiber-reinforced optical waveguide sensor. The sensor's optoelectronic structure consists of a light source, a flexible optical waveguide (with an inner silicone cavity), and a light receiver. An LED serves as the light source, and a photodiode (PD) acts as the receiver, converting the optical signal into an electrical signal. A transparent glycerol liquid channel forms the fiber core, and the silicone tube body serves as the cladding, thus forming the flexible optical waveguide structure. When the sensor is subjected to external excitation, the shape of the flexible optical waveguide changes, causing a corresponding change in light intensity / loss.

[0043] Deformation loss in optical waveguides is mainly divided into macro-bending loss and micro-bending loss, with macro-bending loss having the greatest impact on signal strength. Micro-bending loss refers to energy loss caused by minute distortions in the waveguide axis; while macro-bending loss arises when the waveguide bends, causing some light rays to have an incident angle less than the critical angle, preventing total internal reflection and resulting in leakage to the cladding or radiation into external space, thus causing optical energy loss, such as... Figure 3 As shown.

[0044] Single-cavity fiber-reinforced waveguide sensors are sensitive to bending deformation but cannot distinguish the direction of force. In contrast, multi-cavity fiber-reinforced sensors can not only sense bending deformation but also effectively distinguish the direction of force. Their working principle is as follows: On the sensor's cross-section, a "neutral layer" can be assumed, which is neither stretched nor compressed during bending. Above the neutral layer (outer arc side), the area is under tension, with an increased bending radius and decreased curvature. This increases the amount of light that does not undergo total internal reflection, and the light propagation path in this cavity becomes longer, leading to increased loss. Below the neutral layer (inner arc side), the area is under compression, with a decreased bending radius and increased curvature. This reduces the amount of light that does not undergo total internal reflection, and the light propagation path shortens, resulting in relatively less loss. Therefore, the signal attenuation amplitude of the outer cavity is always greater than that of the inner cavity. Further summary shows that when the sensor cavity is at the same distance from the force-bearing side, the signal attenuation amplitude is roughly the same; the farther the distance from the force-bearing side, the more significant the signal attenuation.

[0045] Figure 4Taking the double-channel fiber-reinforced sensor as an example, the principle will be more clearly explained. This principle also applies to sensors with three or more channels. In the figure, the curvature of the channel where LED1–PD1 is located is k1, the curvature of the channel where LED2–PD2 is located is k2, and the curvature of the "neutral layer" between the two channels is k3. When the bending direction is A, the channel where LED1–PD1 is located is on the outside, and the curvature satisfies k1 < k2 < k3. The number of non-total-reflection light rays increases, the optical propagation path is longer, and the signal attenuation amplitude is greater. When the bending direction is B, the channel where LED2–PD2 is located is on the outside, and the curvature satisfies k1 > k2 > k3. The number of non-total-reflection light rays increases, the optical propagation path is longer, and the signal attenuation amplitude is greater. When the bending direction is C (inward), the curvature satisfies k1 = k2 = k3, and the signal attenuation amplitudes of the two channels are basically the same.

[0046] To characterize and predict the response characteristics of fiber-reinforced optical waveguide sensors to forced bending, in this embodiment, finite element simulation (FEA) is used to analyze it, and COMSOL Multiphysic software is used for multi-physics simulation. To simplify the simulation model, only the tubular silica gel body and glycerol liquid channel of the sensor are three-dimensionally modeled. The optoelectronic signal simulation uses geometric optics in ray optics and solid mechanics in structural mechanics for multi-physics simulation. The simulation results are normalized according to the initial values, that is, the first point (initial power) in each group of data is used as the benchmark and forced to scale to 1W, and the remaining points are scaled according to the same ratio in each group. The simulation results are as Figure 5 shown. As can be seen from Figure 5 a in it, the optoelectronic signal has high sensitivity to the bending deformation of the sensor; as can be seen from Figure 5 b in it, the double-channel sensor is not only sensitive to bending deformation, but can also effectively distinguish two directions (left and right); as can be seen from Figure 5 c in it, the three-channel sensor is not only sensitive to bending deformation, but can also effectively distinguish four directions (up, down, left, and right), which is consistent with the above theory.

[0047] Example 4 This embodiment provides an experimental device 4 for characterizing the performance of fiber-reinforced optical waveguide sensors. Its structure is as Figure 6 shown, and it includes: a perforated board 41, a fiber-reinforced optical waveguide sensor 42, a base 43, a universal joint 44, a connecting member 45, a燕尾滑台 46, a pressure sensor 47, a pressing head 48, and a servo motor 49.

[0048] The fiber-reinforced optical waveguide sensor 42 has universal joints 44 at both ends, which are fixed together by set screws and silicone adhesive. The other end of the universal joint 44 is fixed to a connector 45, which is mounted on a base 43, which is fixed to a perforated plate 41. The dovetail slide 46 is driven by a servo motor 49, and both are fixed to the perforated plate 41 by printed parts. The pressure sensor 47 has a pressure head 48 at its front end, and its rear end is mounted on the dovetail slide 46 by printed parts, with its axis pointing towards the middle of the fiber-reinforced optical waveguide sensor 42.

[0049] Before characterizing its performance, the fiber-reinforced optical waveguide sensor 42 needs to be set with a reference direction (single-cavity fiber-reinforced optical waveguide sensor does not need to, dual-cavity fiber-reinforced optical waveguide sensor has the reference direction when the two cavities are side by side, and triple-cavity fiber-reinforced optical waveguide sensor has the reference direction when the two cavities are side by side on top and the third cavity is below), and the universal joint 44 with different inner diameters needs to be replaced according to the outer diameter of the different cavity sensor.

[0050] When characterizing its performance (such as minimum detection limit, sensitivity, repeatability, etc.), the host computer controls the servo motor 49 to drive the dovetail slide 46, which synchronously drives the pressure head 48 to apply a precise force to the fiber-reinforced optical waveguide sensor 42 and cause it to bend and deform. If it is necessary to test the performance of the sensors with different bending directions of the three cavity structures, simply rotate the universal joints 44 at both ends together by a certain angle (such as 90° or 180°) and fix them again, and then apply the same magnitude of force with the pressure sensor 47 as a reference.

[0051] Figure 7 This describes the performance of optical waveguide sensors with different cavity structures when subjected to the same force (2N) but in different directions. Figure 7 As can be seen from 'a' in the diagram, under the same force, the signal decrease trend of the single-cavity fiber-reinforced sensor is roughly the same regardless of the direction of the force, making it impossible to effectively distinguish the direction of the force. From Figure 7 As shown in b, when the dual-cavity fiber-reinforced sensor is subjected to force, the signal drop is smaller in the cavity closer to the force point; if the two cavities are equidistant from the force point (e.g., side-by-side, vertically distributed), the signal drop is roughly the same for both. This structure can effectively distinguish two force directions (e.g., left-right), but cannot distinguish the other two directions (e.g., up-down). Figure 7 As shown in 'c', the signal change pattern of the three-cavity fiber-reinforced sensor is clearer when subjected to force: the signal of the cavity closer to the force point decreases less, while the signal of the middle cavity decreases to a degree between "closer" and "farther"; when two cavities are equidistant from the force point and the third cavity is far from the force point, the signal of the farthest cavity decreases the most, and the signal decrease trend of the two equidistant cavities is consistent. Based on this characteristic, the three-cavity structure has the potential to effectively distinguish three or even omnidirectional deformation sensing capabilities.

[0052] Example 5 This embodiment provides a branched self-sensing rope driven parallel robot based on a fiber-reinforced optical waveguide sensor, including a frame and a robot body mounted on the frame. The robot body includes a seat and an arm mounted on the seat.

[0053] like Figure 8 and Figure 9 As shown, a branched self-sensing rope driven parallel robot based on a fiber-reinforced optical waveguide sensor includes a frame 51, a moving platform 52, a universal joint 53, a three-cavity fiber-reinforced optical waveguide rope 54, a synchronous belt drive slide module 55, a ball screw slide module 56, an umbrella frame connecting rod 57, a fixed platform 58, and a hinge 59.

[0054] The ball screw slide module 56 is installed above the frame 51. The ball screw slide module 56 includes a motor A561, a fixed shaft seat 562, a lead screw 563, an optical shaft 564, and a lead screw nut seat 565. The motor A561 is fixed to the upper surface of the top plate of the frame 51, the fixed shaft seat 562 is fixed to the lower surface of the top plate of the frame 51, the lead screw 563 passes through the fixed shaft seat 562 and is installed at the output end of the motor A561 through a coupling, the lead screw nut seat 565 is installed on the lead screw 563, and the two optical shafts 564 pass through the lead screw nut seat 565 through sleeves, and their two ends are fixed to the fixed shaft seat 562 and the fixed platform 58, respectively. When the motor A561 drives the lead screw 563 to rotate, it can drive the lead screw nut seat 565 to move up and down along the axial direction of the optical shaft 564.

[0055] The synchronous belt drive slide module 55 is mounted on the fixed platform 58 via a hinge 59. The synchronous belt drive slide module 55 includes multiple support seats 552 arranged in a circumferential array. The support seats 552 are hinged to the fixed platform 58 via the hinge 59. A guide rail 553 is fixed on the support seat 552, and a slider 554 is slidably fitted on the guide rail 553. The slider 554 is driven to slide along the guide rail 553 by a motor B551 set on the support seat 552.

[0056] A connecting rod 57 is provided between the lead screw nut seat 565 and each support seat 552, and the two ends of the connecting rod 57 are respectively hinged to the lead screw nut seat 565 and the support seat 552 by cylindrical pins; by controlling the rise and fall of the lead screw nut seat 565, the support seat 552 can swing up and down.

[0057] A universal joint 53 is provided in the middle of the end of the slider 554 facing away from the guide rail 553. A universal joint 53 is also provided on the moving platform 52. The two ends of the fiber-reinforced optical waveguide rope 54 are fixed to the universal joints 53 on the slider 554 and the moving platform 52, respectively. During operation, the synchronous belt drive slide module 55 and the ball screw slide module 56 work together. The ball screw slide module 56 drives the lead screw 563 via motor A561, which in turn drives the lead screw nut seat 565 to rise and fall. Simultaneously, through the umbrella frame connecting rod 57, it drives the synchronous belt drive slide module 55 (causing the support seat 552 to swing up and down), changing the angle between the synchronous belt drive slide module 55 and the fixed platform 58, thus realizing the vertical movement of the moving platform 52. Meanwhile, the motor B551 in the synchronous belt drive slide module 55 drives the slider 554 via the synchronous belt, which in turn drives the fiber-reinforced optical waveguide rope 54 to move, thereby pulling the moving platform 52. Among them, the ball screw slide module 56 only has a lifting function, while the synchronous belt drive slide module 55 has the ability to control the lifting, x, and y displacement of the moving platform (3 degrees of freedom). The cooperation of the two can expand the workspace while still maintaining 3 degrees of freedom.

[0058] In some embodiments, the parallel robot disclosed in this embodiment can complete shaft hole assembly operations based on human teaching and branch perception. Specifically, the moving platform is suspended by six three-cavity fiber-reinforced sensor ropes. The moving platform is equipped with a material picking device. Humans can complete teaching operations such as picking up materials, aligning holes, inserting, and releasing by dragging the traction ropes or the moving platform. The robot has functions such as trajectory learning and force-position composite control, and can automatically and smoothly align itself according to force feedback, taking into account both accuracy and safety.

[0059] Example 6 This embodiment provides the forward and inverse solution calculations for the position of the parallel robot as provided in Embodiment 5; 1. First, the inverse kinematics calculation of the position of the parallel robot is given: Establish a corresponding reference coordinate system on the simplified diagram of the robot structure, as follows: Figure 10 As shown. Among them. This is a static coordinate system, also known as a reference coordinate system. It is the coordinate system of the moving platform (it can only move up and down along the z-axis). Let be the coordinate system of the moving platform, and let the endpoint of the static platform be . The endpoint of the upper platform is The endpoint of the lower platform is .

[0060] The center point of the slider is The universal joint rotation point (rope fixing point) is and The limiting point of the slider on the guide rail of the linear displacement slide is: (origin), (Also the umbrella frame connection point), the angle between the guide rail and the stationary platform is... ( The universal joint on the slider rotates. Universal joint rotation point on the moving platform The distance between them is the length of the optical waveguide cable branch, and the umbrella frame connection point on the guide rail. To the upper platform endpoint The distance is the length of the umbrella frame.

[0061] Let the circumradii of the static platform, the upper moving platform, and the lower moving platform be respectively... , and The universal joint on the slider rotates To the center of the slider The distance is a, and the length of the optical waveguide rope branch is The length of the umbrella frame support chain is .

[0062] Figure 11 To determine the platform structure parameters, for The angle with the X-axis. Based on trigonometric relationships, the endpoints of the static platform... In the reference coordinate system The coordinates in the equation can be represented as: (1) Similarly, the endpoints of the upper platform In the moving coordinate system The coordinates in the middle are: (2) Lowering the platform endpoints In the moving coordinate system The coordinates in the middle are: (3) Depend on Figure 12 Knowing the angle between the linear slide and the stationary platform The universal joint on the slider rotates The position within the meditation system can be represented as: (4) umbrella frame connection point on the guide rail The position within the meditation system can be represented as: (5) Assuming vector exist Represented in a coordinate system as: (6) vector exist Represented in a coordinate system as: (7) Based on the mapping relationship between the moving coordinate system and the static coordinate system, the positions of each vertex of the upper and lower moving platforms are represented as follows: (8) (9) umbrella frame chain Vector coordinates can be represented as: (10) Optical waveguide rope Vector coordinates can be represented as: (11) Since the length of the umbrella frame support chain is fixed, it can be set as follows: If the rope length is fixed, then This leads to two expressions for the robot's kinematic equations: (13) Equation (13) simplifies to: (15) We can obtain the following using the universal trigonometric formula: (16) in From equations (15) and (16), we can obtain: (17) The solution is: (18) Depend on Figure 11 It can be seen that the vertices of the static platform The line connecting the origin to the coordinate system is in the same coordinate system. The angular relationship between the axes can be summarized as follows: (19) For equation (14), let , , , , Substituting and simplifying, we obtain the general expression: (20) in: (twenty one) The general solution to this equation is: (twenty two) There are two possible inverse kinematics solutions, resulting in two corresponding positions for the slide. However, we only consider the case where all the optical waveguide cable branches are located at the bottom of the stationary platform. In this case, the robot's kinematic chains will not interfere with each other. The expression is: (twenty three) 2. Next, based on the inverse solution, we will provide an analysis of the forward solution for the parallel robot; Since the upper moving platform only moves along the z-axis Therefore, when solving for the position of the moving platform, only the solution needs to be found. Known driving variables It can be obtained directly from equation (15): (twenty four) Since the six-branch parallel robot provided in Example 5 is a redundant drive system, the number of constraint equations is greater than the number of unknowns when solving for the position of the lower moving platform, forming an overdetermined nonlinear equation system. Therefore, the Newton-Raphson iterative method is used to solve this problem. The known driving variables... Constraint equations can be established: (25) in Indicates the first The equations that satisfy the geometric length constraints of the branches.

[0063] Write it in vector form: (26) in For the position vector of the moving platform Based on the mechanism's geometric parameters or the solution from the previous moment, set... Calculate the Jacobian matrix. (27) Update and iteration formula: (28) Iteration stops when the following condition is met: or (29) in and This is the set convergence threshold.

[0064] This embodiment also establishes the mapping relationship between the end-effector dynamics model and external forces for interaction of optical waveguide cable branch sensing. The control system block diagram is as follows: Figure 13 As shown. The parallel robot proposed in Example 5 consists of n=6 branches and has m=3 platform degrees of freedom. Let the Cartesian pose vector of the end effector be... The active driving variable (slide position) is The rope tension vector is According to Lagrange's second kind equation and the principle of virtual work, the dynamic equation of Cartesian space can be obtained as follows: (30) in, It is a symmetric positive definite inertial matrix. For centrifugal and Coriolis terms, For gravity, The resistance is caused by friction from the slide rails, ropes, etc. The Cartesian force generated by the actuator and transmitted to the end via the mechanism. It is caused by external forces (collision, interaction).

[0065] The relationship between driving force and rope tension is as follows: (31) in, Let be the Jacobian matrix from the end effector to the active joint.

[0066] If an external force is applied at the middle position of an optical waveguide cable, the force mapped to the end coordinate system is as follows: (32) in, This is the Jacobian matrix of the stress point relative to the end of the link. Therefore, the signal variation of the optical waveguide cable can be converted into an equivalent external force at the end. To ensure safe and smooth human-machine collaboration, Cartesian impedance control is employed to ensure that the interaction between the end effector and the external environment conforms to the desired second-order spring-damped-mass model. (33) in, , , These represent the expected mass, damping, and stiffness matrices, respectively. , , These are the desired position, velocity, and acceleration of the end effector, respectively. , , These are the actual position, velocity, and acceleration of the end effector. By setting appropriate parameters and adding velocity / displacement limits, singularity clearance, and virtual wall constraints, the end effector's motion is ensured to be smooth and controllable, without any undesirable large displacements or high-speed movements.

[0067] The desired Cartesian acceleration is obtained through inverse kinematics. The acceleration command is converted to a slide-driven acceleration command and combined with a tension distribution strategy to ensure that the tension of each rope is positive and does not fall below the safety lower limit. This control strategy allows the end to deflect according to the set spring-damping characteristics under the action of external forces without immediate rigid resistance, thereby improving interaction safety and compliance.

[0068] Example 7 This embodiment presents the interaction scheme of the parallel robot in Embodiment 5, which is divided into two modes: normal operation mode and interactive operation mode.

[0069] In normal operating mode, the operating process is as follows: Figure 14 As shown, the robot moves according to the task trajectory given by the host computer. If the real-time algorithm detects that the optical waveguide rope is under force or touches an obstacle, it immediately triggers protection: stops moving, and displays the stressed rope, the magnitude of the force, and the direction of the force mapping on the host computer to ensure safety.

[0070] In interactive operation mode, the user actively applies a push / pull force to the middle section of the waveguide rope. The system uses a Jacobian matrix to map the force changes of the multiple ropes into the resultant force direction and magnitude of the moving platform, triggering motion within a set threshold to ensure smooth platform movement along the force direction. To avoid false triggering, a start threshold, force limit, and speed limit are set, and the movement range is restricted through virtual walls and singularity zone detection to prevent the robot from making undesirable large displacements or high speeds. Mode switching requires double confirmation, and the system automatically returns to standby mode if there is no continuous input during interaction.

[0071] Specifically, in normal operation mode, communication connections with the six optical waveguide sensing branches are first established via an initialization command. The signal sequences of each optical waveguide cable are then collected, and their average values ​​are calculated and used as the initial state reference values. The upper-level control system sends task parameters such as the motion target and pose information. Internally, the system calls the forward and inverse kinematics modules to calculate the trajectory and outputs target position commands for each slide and the lead screw nut seat. Each actuator drives the optical waveguide ropes according to the path planning commands, causing the moving platform to run along the planned trajectory. During the robot's task execution, the system continuously monitors and samples the real-time signals of the six optical waveguide ropes at a frequency of 1kHz. Simultaneously record the signal from the previous moment. Calculate the deviation between the real-time signal and the reference signal. and the deviation of signals at adjacent times. And define the collision coefficient: .in, , These are weighting factors used to balance the effects of long-term drift and transient mutations. A collision threshold is set. ,when When a collision is detected, the system immediately triggers protection: interrupting the current task, issuing an emergency stop or reversal command, stopping all drives, and displaying the force-bearing chain number, force magnitude, and direction to the host computer, while simultaneously logging the anomaly. Furthermore, each waveguide cable sensing system on the robot must be configured with "wired-AND" logic; that is, if the collision coefficient calculated by any waveguide cable sensing system exceeds a threshold, a collision is determined to have occurred. If no collision occurs, the system continues to operate; if the detected signal returns to the baseline range, the collision marker is cleared, and the robot can continue operating after user confirmation.

[0072] If the user has pre-enabled the "interactive operation mode" on the host computer, the system will enter the "perception-follow" process, such as... Figure 15 As shown. Specifically, after the robot starts, it remains stationary. A person actively pushes or pulls the middle section of the optical waveguide ropes, and the system continuously monitors and samples the real-time signals of the six optical waveguide ropes at a frequency of 1kHz. Based on the sensor voltage-force calibration value, it is converted into an equivalent force, and the force branches and force directions determined by the real-time algorithm are mapped into spatial forces. The force is then compared with a set starting threshold (e.g., 0.2N). Once the applied force exceeds the threshold, the slide is controlled by a distribution algorithm to perform corresponding coordinated actions, achieving "manual traction" or "guided movement".

[0073] When the input signals from the six optical waveguide ropes stabilize for a period of time (e.g., no significant signal fluctuations within 3 seconds) or the user actively releases the ropes (i.e., the signal returns to its initial value), the system automatically ends the interactive state. The user can choose to record this interaction path as a teaching trajectory and store it as a trajectory template via the host computer's interactive function buttons for repeated use. The user can also configure trigger conditions and response actions to achieve various perception-based interactive behaviors, such as touching symmetrical ropes to return to zero, rapidly pulling to trigger an emergency stop, or touching multiple specific ropes to trigger a preset path.

[0074] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0075] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present 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 the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A fiber-optic enhanced waveguide sensor in a cylindrical structure, characterized by, The fiber reinforced optical waveguide sensor comprises a core located at a center position, an outer side of the core is provided with a Kevlar fiber tube, and an outer side of the Kevlar fiber tube is wrapped with silica gel; an inner side of the Kevlar fiber tube is also filled with silica gel and wraps the core; two ends of the core are respectively provided with a light emitting diode and a photodiode; and two ends of the fiber reinforced optical waveguide sensor are sealed through sealing silica gel.

2. A fiber-optic waveguide sensor of claim 1, wherein, The number of the cores is 1-3, and the cores are distributed in a circumferential array.

3. The fiber-optic waveguide sensor of claim 1, wherein, The core is transparent glycerol, and the diameter of the core is 2 mm.

4. The fiber-optic sensor according to claim 1, wherein, When the number of the cores is 1, the outer diameter of the Kevlar fiber tube is 4 mm, and the thickness is 0.6 mm; and the outer diameter of the sensor is 6 mm. When the number of the cores is 2, the outer diameter of the Kevlar fiber tube is 8 mm, and the thickness is 0.6 mm; and the outer diameter of the sensor is 10 mm. When the number of the cores is 3, the outer diameter of the Kevlar fiber tube is 10 mm, and the thickness is 0.6 mm; and the outer diameter of the sensor is 12 mm.

5. Use of the fiber reinforced optical waveguide sensor according to any one of claims 1-4 as a rope in constructing a rope-driven parallel robot.

6. A branched sensing rope suspended parallel robot embedded with optical waveguide sensing, comprising a frame, characterized in that, The upper part of the frame is provided with a lifting screw nut seat and a fixed platform; a plurality of support seats are hingedly connected to the fixed platform and are uniformly distributed in a circumferential direction; an umbrella frame connecting rod is arranged between the screw nut seat and each support seat, and the two ends of the umbrella frame connecting rod are hingedly connected to the screw nut seat and the support seat, respectively. A sliding block is arranged on the support seat and can slide along the length direction of the support seat; a movable platform is arranged below the fixed platform; the fiber reinforced optical waveguide sensor according to any one of claims 1-4 is arranged between the movable platform and the sliding block; and the two ends of the fiber reinforced optical waveguide sensor are connected to the movable platform and the sliding block through universal joints, respectively.

7. The branched sensing rope suspended parallel robot embedded with optical waveguide sensors of claim 6, wherein, A ball screw sliding table module is installed on the top of the frame; the ball screw sliding table module comprises a motor A, a fixed shaft seat, a screw, a screw nut seat and two optical shafts; the motor A and the fixed shaft seat are fixed on the top of the frame; the screw penetrates through the fixed shaft seat and is installed on the output end of the motor A through a coupling; the screw nut seat is installed on the screw; the two optical shafts penetrate through the screw nut seat through sleeves and are fixed at the two ends to the fixed shaft seat and the fixed platform, respectively; when the motor drives the screw to rotate, the screw nut seat can be driven to ascend and descend along the optical shafts.

8. The branched sensing rope suspended parallel robot embedded with optical waveguide sensors of claim 6, wherein, A guide rail is fixed on the support seat, the sliding block is in sliding cooperation with the guide rail, and a motor is arranged on the support seat to drive the sliding block to slide along the guide rail.

9. Use of the parallel robot according to any one of claims 6-8 in human-machine interaction work.

10. Use of the parallel robot according to any one of claims 6-8 in shaft hole assembly work.

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