Parallel Joint Research Articles

Mixed distortion image enhancement method based on joint of deep residuals learning and reinforcement learning

The images distortion leads to the loss of image information and the degradation of perceptual quality. To solve this problem, we investigate a novel mixed distortion image enhancement method based on the parallel network combines deep residual and reinforcement learning. The no-reference image quality assessment algorithm is used to determine the type and level of distorted images accurately. According to the type of distortion, the mixed distortion images enter one of the subsequent parallel joint learning networks automatically. In the joint learning framework, we prepare different residual networks to handle specialized restoration assignments including deblurring, denoising, or JPEG compression. Simultaneously, reinforcement learning then learns a policy to select the next best restoration tasks to progressively restore the quality of a corrupted image. Our method is capable of restoring images corrupted with complex mixed distortions in a more parameter-efficient manner in comparison to conventional networks. The extensive experiments on synthetic and real-world images validate the superior performances of the proposed method.

Numerical Investigation on the Hydraulic Fracture Evolution of Jointed Shale

Joints are a common structure of heterogeneous shale rock masses, and in situ stress is the environment in which heterogeneous rock masses can be found. The existence of joint plane and confining pressure difference influences the physical properties of shale and propagation of fractures. In this study, jointed shale specimens were simulated under different confining pressures to explore the failure patterns and fracture propagation behavior of hydraulic fracturing. Different from the common research of hydraulic fracturing on signal parallel joint rock mass, the simulations in this study considered three points (parallel joint, multi‐dip angle joint, and no‐joint points). The effects of the single‐dip angle joint, multi‐dip angle joint, and confining pressure difference on the hydraulic fracture evolution and stress evolution of the jointed shale were studied comprehensively. The confining pressure difference coefficient proposed in this study was used to accurately describe the confining pressure difference. Results indicate that the larger is the confining pressure difference, the stronger is the control of the maximum principal stress on fracture evolution; by contrast, the smaller is the confining pressure difference, the stronger is the control of the joint plane on fracture evolution. Under the same confining pressure difference, the hydraulic fracture propagates more easily along the small dip angle joint plane. As the value of the confining pressure difference coefficient moves closer to zero, the hydraulic fracture propagates randomly, the tensile stress region around the fracture tip widens, and the joint planes fractured by tensile increase. This study can offer valuable guidance to the design of unconventional reservoir reconstruction.

Malicious URL Detection Based on a Parallel Neural Joint Model

A parallel neural joint model algorithm is proposed for the analysis and detection of malicious Uniform Resource Locator (URL). By detecting and analyzing malicious URL's characteristics, the semantic and visual information will be extracted. First, a visualization algorithm is used to realize the visualization of the URL mapping to a gray image with texture characteristics. Second, the lexical feature and character feature of URL are extracted and further processed through word vector technology. These extracted features are transformed into lexical embedding vectors and character embedding vectors. To combine the texture features with text features, a parallel joint neural network combining capsule network (CapsNet) and independent recurrent neural network (IndRNN) is utilized to capture multi-modal vectors of visual and semantic information synchronously. The last layer utilizes the attention mechanism to further filter the deep features extracted from the overall network while concentrating on effective features improving the classification accuracy and analyzing and detect malicious URLs. Based on the experimental results, it is demonstrated that this algorithm has higher accuracy compared to the traditional algorithms.

Study on S-wave propagation through parallel rock joints under in situ stress

In situ stress is an important feature of underground rock masses. This paper extends the time-domain recursive method to the study of S-wave propagation through in situ stressed rock masses containing parallel joints. A linear elastic model and hyperbolic nonlinear slip model (HNSM) are first used to establish equations for wave propagation across jointed rock masses under a combination of gravitational and tectonic stress. Then, a comparison is made of the waveforms generated using the HNSM and Mohr–Coulomb slip model. Their differences are investigated and the wave propagation equation verified. Finally, parametric studies are conducted to investigate the effect of joint angle, joint number, in situ stress, and lateral pressure coefficient. The results show that the HNSM can describe the dynamic changes in the stress and their effect on the deformation behavior of the joint during the propagation of the S-wave. The effect of in situ stress on wave propagation is related to the joint angle and lateral pressure coefficient, which determine the initial stress state and contact state of the joint.

Residual varus alignment can reduce joint awareness, restore joint parallelism, and preserve the soft tissue envelope during total knee arthroplasty for varus osteoarthritis.

The objectives were to compare the coronal joint configuration of the knee joints, coronal gap imbalances requiring substantial medial release, and patient-reported outcomes, including the forgotten joint score, between knees in which residual varus alignment was intentionally allowed according to an individualised lower limb analysis and those with mechanical alignment in total knee arthroplasty for varus osteoarthritis. Consecutive primary navigated total knee arthroplasty procedures for varus osteoarthritis were retrospectively reviewed. The study cohort was stratified based on whether residual varus alignment was intentionally allowed. Propensity-score matching was performed based on the baseline characteristics, including demographic characteristics, preoperative radiological measurements, and the Western Ontario and McMaster University Osteoarthritis Index (mechanical alignment group vs residual varus group). The patient-reported outcomes and coronal joint line orientation of the knee (relative to the ground) and ankle were evaluated. Coronal gap differences and coronal gap imbalances were analysed using intraoperative gap measurements. Relative to the ground and ankle, the postoperative knee joint line orientation slanted down laterally in the mechanical alignment group (-3.05˚ ± 1.62, relative to the ground; -2.65˚ ± 1.56, relative to the ankle joint), but was parallel in the residual varus group (-0.75˚ ± 1.59, relative to the ground; -0.95˚ ± 1.71, relative to the ankle joint). Coronal gap differences at extension and the proportion of coronal gap imbalances requiring substantial medial release were 1.27 ± 1.53 and 6% in the residual varus group and 2.32 ± 1.24 and 15% in the mechanical alignment group. Postoperatively, the residual varus group showed higher Western Ontario and McMaster University Osteoarthritis Index scores and total forgotten joint scores than the mechanical alignment group (6.97 ± 4.75 vs. 10.31 ± 5.74 and 56.42 ± 12.85 vs. 45.69 ± 14.49, respectively). Intentionally allowed residual varus alignment with individualised analysis of lower limb alignment restored the parallel joint line of the knees, preserved the soft tissue envelope, and reduced joint awareness after total knee arthroplasty for varus osteoarthritis. Therapeutic, Level III retrospective case-control study.

To the problem of determining the deformation characteristics of jointed rock mass

sThe article considers the results of the study of a fragment of rock mass weakened by a system of parallel joints. Using numerical modelling, its deformation characteristics at different ratios of the characteristic size of the fragment to the characteristic size of its structural element (layer) are studying. The conditions for the representativeness of a fragment are discussed. The results of numerical calculations are compared with the results of the previously proposed analytical calculation method and the conditions for their convergence are discussed.

Direct shear tests of artificial jointed rock specimens with parallel joints

The shear behavior of artificial jointed rock samples with parallel joints is studied using direct shear tests. The effects of the number (N) of parallel joints, the angle (β) between the parallel joints and the horizontal loading direction, and the length (l) of the parallel joints on the shear characteristics and the damage morphologies of artificial jointed rock specimens were studied. The test results indicate that (1) under forward shearing (β 90°), the entire shear process of parallel joints can be mainly represented by the following stages: the linear elastic stage, the crack initiation and expansion stage of the intermittent joints, the fracture and failure stage of the rock bridges, the frictional sliding stage of the fractured section, and the residual friction stage of the fractured section. The frictional sliding force of the fractured section under reverse shearing is less than that under forward shearing. (2) When l = 20 mm and β is fixed (15° < β < 165°), as N increases from 2 to 5, the total lengths of the rock bridges between the joints increase, the coalescence path of the cracks increases, the frictional sliding force between the crack surfaces increases, and the shear strength and cohesion c of the specimen increase. (3) When N = 2 and β is fixed (15° < β < 165°), as l increases from 20 to 50 mm, both shear strength and cohesion c of the specimen increase.

Effects of a set of parallel joints with unequal close-open behavior on stress wave energy attenuation

Rock joints with unequal close-open behavior have significant influences on stress wave propagation across them. A stress wave of sufficiently large amplitude does not only mobilize the nonlinear deformation of joints, but also force the joints to close and open. In the present study, the Bandis-Barton model and the Coulomb-slip model are adopted to describe the normal and tangential behavior, respectively, of the closed joints. However, when the joints are open, both sides of the joints behave as two free surfaces. The improved time-domain recursive method is employed to derive wave propagation equations for three cases, i.e. the joint is closed but does not slide, the joint is closed and slides, and the joint is open. Then, the normal and tangential relative displacements of joints, as well as the energy attenuation coefficient, are calculated. A comparison of transmitted waves based on different methods is conducted to verify the validity of the present approach. Eventually, parametrical studies show that the higher in-situ stress causes the smaller energy attenuation coefficient, and the wave energy attenuation is also dependent on the frequency and amplitude of the incident wave, the incident angle, the joint spacing and the joint number.

Kinematik Forward dan Analisis Kesalahan Pada Kesejajaran Sumbu Join Mekanisme Paralel Rotasi Murni 3-URU

In this paper we discussed the forward kinematic and constrain error of 3-URU parallel mechanism. The mechanism was composed of URU kinematic chain consisting of three parallel joint axes and two intersecting joint axes. The direction of parallel joint axis representing direction of force constraints acting on center of platform rotation. In this research was investigated the effect of error of direction of parallel joint exes on kinematic chains to the platform orientation and position of center of platform rotation. It is also developed the formulation of forward kinematic of the mechanism. The forward kinematic was carried out by taking account geometric constraint of platform motion which is derived analytically by using software Maple 16. On the other hand, the constraint error was evaluated using the CAD simulation Autodesk Inventor. Based on the result, it can be summarized that error of parallel joint axes produced significant effect on error of platform motion especially for location of the center of platform rotation which is classified as uncompensated error. The formulation of forward kinematic was successfully derived which is confirmed with inverse kinematic and CAD simulation.

Модели регионального лидерства в Евразии: к новой исследовательской повестке

One of the important tasks in the study of international politics today is the elaboration and empirical verification of new theoretical models for the coexistence of several regional leadership projects, simultaneously implemented by various countries and international organizations. Until now, the existing models, as a rule, have described this kind of leadership at the international arena in fundamentally hierarchical terms: either as a unipolar world with a hegemonic country dominating global politics, or as a bipolar system. These models unambiguously assume that the world either “belongs” to one hegemon, or is divided between two superpowers. In the latter case, there are practically no regions where both leadership projects would be carried out simultaneously, since such a geographical “overlap” would inevitably provoke conflict. Meanwhile, the task of understanding and explaining the internal mechanics of the simultaneous coexistence of several potential leaders on the same geographic territory for a fairly long time remains unsolved. In the modern world, such parallel (joint or competitive) leadership can no longer be regarded as an anomaly or a temporary phenomenon, it becomes a “new normality”, creating additional opportunities for international players, but at the same time imposing more substantial constraints on them. Thus, the relevance of the agenda put forward in the article is determined by a number of circumstances, the most fundamental of which is the crisis of the global governance system and the neoliberal model of globalization. Today, macro-regions become “building blocks” for the multipolar structure of the world, and the role of individual states or their groups, which begin to play a structure-forming role in “their” macro-regions, is increasing. These are potential leaders with special characteristics and special relations with their “followers”. The problem of leadership is most interestingly actualized in the Eurasian region, the internationalization of which is rapidly growing. In this region, several leaders are observed (such as Russia, China, the European Union) who compete for the same followers, offering them different agendas and using a wide range of power tools – from “soft” to “hard” power. It is in Eurasia that the variability of relations connecting the leader and followers is extremely high. In this article, the authors put forward and ground the possibility and necessity of developing a research agenda on regional leadership based on the material of modern Eurasia – the most important world macro-region where three leadership projects are being successfully implemented at the same time, the description and analysis of which in their interconnection go beyond the Eurasian theme only and can help advance our understanding of the nature of multipolarity in modern international relations.

Analysis of kinematic dexterity and stiffness performance based on Spring’s wire-driven 4-SPS/U rigid‒flexible parallel trunk joint mechanism

Purpose The purpose of this paper is to propose a two-degrees-of-freedom wire-driven 4SPS/U rigid‒flexible parallel trunk joint mechanism based on spring, in order to improve the robot’s athletic ability, load capacity and rigidity, and to ensure the coordination of multi-modal motion. Design/methodology/approach First, based on the rotation transformation matrix and closed-loop constraint equation of the parallel trunk joint mechanism, the mathematical model of its inverse position solution is constructed. Then, the Jacobian matrix of velocity and acceleration is derived by time derivative method. On this basis, the stiffness matrix of the parallel trunk joint mechanism is derived on the basis of the principle of virtual work and combined with the deformation effect of the rope driving pair and the spring elastic restraint pair. Then, the eigenvalue distribution of the stiffness matrix and the global stiffness performance index are used as the stiffness evaluation index of the mechanism. In addition, the performance index of athletic dexterity is analyzed. Finally, the distribution map of kinematic dexterity and stiffness is drawn in the workspace by numerical simulation, and the influence of the introduced spring on the stiffness distribution of the parallel trunk joint mechanism is compared and analyzed. It is concluded that the stiffness in the specific direction of the parallel trunk joint mechanism can be improved, and the stiffness distribution can be improved by adjusting the spring elastic structure parameters of the rope-driven branch chain. Findings Studies have shown that the wire-driven 4SPS/U rigid‒flexible parallel trunk joint mechanism based on spring has a great kinematic dexterity, load-carrying capacity and stiffness performance. Research limitations/implications The soft-mixed structure is not mature, and there are few new materials for the soft-mixed mixture; the rope and the rigid structure are driven together with a large amount of friction and hindrance factors, etc. Practical implications It ensures that the multi-motion mode hexapod mobile robot can meet the requirement of sufficient different stiffness for different motion postures through the parallel trunk joint mechanism, and it ensures that the multi-motion mode hexapod mobile robot in multi-motion mode can meet the performance requirement of global stiffness change at different pose points of different motion postures through the parallel trunk joint mechanism. Social implications The trunk structure is a very critical mechanism for animals. Animals in the movement to achieve smooth climbing, overturning and other different postures, such as centipede, starfish, giant salamander and other multi-legged animals, not only rely on the unique leg mechanism, but also must have a unique trunk joint mechanism. Based on the cooperation of these two mechanisms, the animal can achieve a stable, flexible and flexible variety of motion characteristics. Therefore, the trunk joint mechanism has an important significance for the coordinated movement of the whole body of the multi-sport mode mobile robot (Huang Hu-lin, 2016). Originality/value In this paper, based on the idea of combining rigid parallel mechanism with wire-driven mechanism, a trunk mechanism is designed, which is composed of four spring-based wire-driven 4SPS/U rigid‒flexible parallel trunk joint mechanism in series. Its spring-based wire-driven 4SPS/U rigid‒flexible parallel trunk joint mechanism can make the multi-motion mode mobile robot have better load capacity, mobility and stiffness performance (Qi-zhi et al., 2018; Cong-hao et al., 2018), thus improving the environmental adaptability and reliability of the multi-motion mode mobile robot.

Study on the Effects of Joint Inclination and Size Effect on the Failure Process of Rock-like Materials

To explore the effects of joint inclination angle and the size on the mechanical properties and failure process of rock-like specimens, a series of uniaxial compression tests were carried out on rock-like specimens.The specimens are consist of two sizes and contain three parallel joints with various inclination angles. During testing, the variation characteristics of apparent strain field of specimens is recorded by digital image correlation (DIC) system. Testing results reveal the uniaxial compression strength of the specimen decreases gradually with the joint inclination increases from 0° to 60°, while increasing gradually with the joint inclination increases from 60° to 90°. In addition, the peak compression strength of the large-size specimens is obviously lower than that of the small-size specimen when the joint inclination angle is 0°~30°. By contrast, the peak compression strength of the large-size specimens is the same as that of the small-size specimen when the angle is 30°~60°, approximately. But, the peak compression strength of large-size specimen is obviously higher than that of small-size specimen when the joint inclination angle is between 60° and 90°. Finally, five different types of cracks are observed in this work, i.e., tensile crack,airfoil tension crack,pull-shear mixing crack,secondary crack and far field tensile crack.

Lateral Resistance of CLT Wall Panels Composed of Square Timber Larch Core and Plywood Cross Bands

Thinned, small larch logs have small diameters and no value-added final use, except as wood chips, pallets, or fuel wood, which are products with very low economic value; however, their mechanical strength is suitable for structural applications. In this study, small larch logs were sawed, dried, and cut into square timbers (with a 90 mm × 90 mm cross section) that were laterally glued to form core panels used to manufacture cross-laminated timber (CLT) wall panels. The surface and back of these core panels were covered with 12-mm-thick structural plywood panels, used as cross bands to obtain three-ply CLT wall panels. This attachment procedure was conducted in two different ways: gluing and pressing (CGCLT) or gluing and nailing (NGCLT). The size of the as-manufactured CLT panels was 1,220 mm × 2,440 mm, the same as that of the plywood panels. The final wall panels were tested under lateral shear force in accordance with KS F 2154. As the lateral load resistance test required 2,440 mm × 2,440 mm specimens, two CLT wall panels had to be attached in parallel. In addition, the final CLT panels had tongued and grooved edges to allow parallel joints between adjacent pieces. For comparison, conventional light-frame timber shear walls and midply wall systems were also tested under the same conditions. Shear walls with edge nail spacing of 150 mm and 100 mm, the midply wall system, and the fabricated CGCLT and NGCLT wall panels exhibited maximum lateral resistances of 6.1 kN/m (100%), 9.7 kN/m (158%), 16.9 kN/m (274%), 29.6 kN/m (482%), and 35.8 kN/m (582%), respectively.

Origin of Regular Networks of Joints: Experimental Constraints, Theoretical Background, and Numerical Modeling

AbstractExperimental data show that inelastic straining occurs even at very low pressure before and during brittle fracturing. This process is therefore investigated within the framework of elastoplasticity using 2‐D, three‐layer finite difference modeling. The constitutive model includes both tensile and shear failure mechanisms coupled at the level of the strain softening law. The modeling results show that sets of parallel joints initiate as pure dilation bands, the narrow σ3‐normal bands of localized dilatant damage (inelastic deformation). The band thickness, length, and the initial strain softening degree within it are proportional to the ductility of the material, which increases with the effective stress level (σ1) or pressure. The strength reduction within the bands is accelerated at a certain stage, and the strength locally reaches zero resulting in fracture initiation. The initial fracture then propagates in Mode I following the propagating band. The fracture (joint) appears thus as a band of damaged material with the increased porosity, which is maximum along the axial zone of the band where the material is completely broken. The damage is due to both tensile and shear mechanisms. The role of shear failure increases with the ductility (pressure) increase, which also leads to the band thickness increase. These processes can result in small (band thickness)‐scale oblique shear fractures within the band, causing the increase in the roughness of fracture walls organized in plumose patterns typical of both natural and experimentally generated joints.

Experimental and Numerical Study of the Uniaxial Compressive Stress-Strain Relationship of a Rock Mass with Two Parallel Joints

AbstractA “rock bridge”, defined as the closest distance between two joints in a rock mass, is an important feature affecting the jointed rock mass strength. Artificial jointed rock specimens with two parallel joint fractures were tested under uniaxial compression and numerical simulations were carried out to study the effects of the inclination of the rock bridge, the dip angle of the joint, rock bridge length, and the length of joints on the strength of the jointed rock mass. Research results show: (1) When the length of the joint fracture, the length of the rock bridge, and the inclination of the rock bridge stay unchanged, the uniaxial compressive strength of the specimen gradually increases as the inclination of the joint fracture increases from 0°to 90°. (2) When the length of the joint fracture, the length of the rock bridge, and the inclination of the joint fracture stay unchanged, the uniaxial compressive strength of the specimen shows variations in trends with the inclination of the rock bridge increasing from 30° to 150° (3). In the case when the joint is angled from the vertical loading direction, when the dip angle of the joint fracture, the inclination of the rock bridge, and the length of the rock bridge stay unchanged, the uniaxial compressive strength of the specimen gradually decreases with an increasing length of joint fracture. When the dip angle of the joint fracture, the inclination of the rock bridge, and the length of the joint fracture stay unchanged, the uniaxial compressive strength of the specimen does not show a clear trend with an increase of the length of the rock bridge.

Development of a Novel SMA-Driven Compliant Rotary Actuator Based on a Double Helical Structure

This paper proposes a new shape memory alloy (SMA)-driven compliant rotary actuator that can perform both passive and self-actuated motions. This SMA actuator is suitable as a redundant actuation part in a parallel robot joint to assist with singularity postures where the robot might lose the ability to maintain the position and orientation of the end effector. The double helical compliant joint (DHCJ) was chosen as a candidate mechanism; it can act in soft compliance with linear characteristics and a wide range of motion. The experimental results validated that the proposed model can be used to simulate the DHCJ behavior. The use of this mechanism exhibits advantages such as one-axis rotational motion, linear behavior even for a compliant mechanism, stiffness in the other axes of motion, and compact size. SMA leaves (strips) were used as actuation parts, and a single SMA leaf was tested before combining with the double helical frame as an SMA actuator. The prototype was fabricated, and necessary parameters such as deflection angle, temperature, torque, and stress–strain were collected to define the model for a controller. This actuator is controlled by a feedforward controller and provides rotational motion for both forward and reverse sides with a maximal range of 40 degrees.

A Simplified Inverse Dynamics Modelling Method for a Novel Rehabilitation Exoskeleton with Parallel Joints and Its Application to Trajectory Tracking

In this paper, a new modular upper limb rehabilitation exoskeleton, which is actuated by a parallel mechanical structure, is designed to help stroke patients. For analysing the relationship between motor torque and joint torque of the novel exoskeleton, a conversion algorithm mapping motor motion to joint motion is developed here. Then, to simplify the dynamics model of exoskeleton with parallel actuated joints, the serial equivalence configuration dynamics of the exoskeleton is established to be equivalent to the parallel joints dynamics. Afterwards, a torque controller used for our exoskeleton is designed based on the proposed conversion algorithm and the inverse dynamics of exoskeleton. It should be noted that the controller mentioned above combines both conversion algorithm and joint position decoupling. At last, for verifying the effectiveness of the proposed algorithms, a trajectory tracking simulation is given, and the simulated results show the proposed algorithms are valid.

Strength of composite plate with parallel offset misalignment double-bolted joint under bending moment

The connection concept of placing only two bolts in offset misalignment against the bending load along the wing span was used for an aerobatic airplane designed in Thailand as a KIT plane to minimize the impact of drilling numerous holes. This concept can deviate the force direction on the holes. The two suitable drilling positions should have the lowest resultant force and highest strength of fiber reinforcement structure. To investigate the strength of the fastener hole when the force deviated from the original orientation, specimens, made from twill weave carbon fiber-epoxy and laid up at ±45-degree orientation, were tested under bearing load according to ASTM D5961 standard. The experimental results revealed that the bearing strength of CFRP material decreases when the force deviation angle increases, so zero-angle deviation of the resultant force on the drilling hole is the most suitable orientation to absorb bolt bearing load. The most suitable pattern of two offset misalignment holes is the greatest horizontal distance at zero vertical distance when it was considered only the effect of the bearing strength and the deviation angle. Moreover, the failure pattern begins to deviate along the fiber orientation when the inclination angle increased.

Inference search algorithm for optimizing scheduling and minimizing mean tardiness in parallel joint robots

The issue of scheduling identical parallel joint robots to reduce the mean tardiness is one of the most important challenges in industrial parallel robots. Precedence and job inconsistency are the constraint of this challenging issue. Indeed, due to the precedence constraint and inconsistencies among jobs, achieving best solution to schedule a number of jobs in a number of robots is highly difficult. This problem is regarded as one of the NP-hard class issues. In this study, despite the constraints of precedence and inconsistency among jobs, a new method based on inference search (IS) algorithm was proposed for scheduling and minimizing mean tardiness in identical parallel joint robots. Results of the simulations conducted in this study indicate that the proposed method, unlike genetic algorithms (GA), tabu search (TS) algorithms and hybrid intelligent solution system (HISS) is scalable and it optimized the parameters of mean tardiness and system solution time.

Inverse kinematic solution of 6R robot manipulators based on screw theory and the Paden–Kahan subproblem

The traditional Denavit–Hatenberg method is a relatively mature method for modeling the kinematics of robots. However, it has an obvious drawback, in that the parameters of the Denavit–Hatenberg model are discontinuous, resulting in singularity when the adjacent joint axes are parallel or close to parallel. As a result, this model is not suitable for kinematic calibration. In this article, to avoid the problem of singularity, the product of exponentials method based on screw theory is employed for kinematics modeling. In addition, the inverse kinematics of the 6R robot manipulator is solved by adopting analytical, geometric, and algebraic methods combined with the Paden–Kahan subproblem as well as matrix theory. Moreover, the kinematic parameters of the Denavit–Hatenberg and the product of exponentials-based models are analyzed, and the singularity of the two models is illustrated. Finally, eight solutions of inverse kinematics are obtained, and the correctness and high level of accuracy of the algorithm proposed in this article are verified. This algorithm provides a reference for the inverse kinematics of robots with three adjacent parallel joints.