Orthogonal Joint Research Articles

An active SLAM with multi-sensor fusion for snake robots based on deep reinforcement learning

Snake-like robots can imitate the movement patterns of animals in nature and enter the space that traditional robots cannot enter, which adapt to environments that humans cannot reach, and expand the field of human exploration. However, it is often challenging to realize autonomous navigation and simultaneously avoid obstacles under an unknown environment, that is, active SLAM (Simultaneous Localization and Mapping). This paper proposes an autonomous obstacle avoidance method combined with SLAM based on deep reinforcement learning for a wheeled snake robot by using a multi-sensor. Firstly, we design a modular wheeled snake robot structure with lightweight materials based on orthogonal joints and build a three-dimensional model of a snake robot in Gazebo. Secondly, the SLAM based on two-dimensional LiDAR and IMU is used to realize autonomous navigation under an unknown environment and detect obstacles. At the same time, a Deep Q-Learning-based path planning method of the snake robot is proposed to realize obstacles avoidance during navigation. Finally, simulation studies and experiments show that the designed snake-like robot can realize effective path planning and environmental mapping in environments with obstacles. The proposed active SLAM algorithm improves the success rate of snake-like robot path planning, has better obstacle avoidance ability for obstacles, and reduces the number of collisions compared with the traditional A* and the sampling-based RRT* algorithms.

Investigating Load Arches and the Uplift Capacity of Rock Anchors: A Numerical Approach

Rock anchors, which can withstand substantial forces and are essential for securing the foundations of the built environment, can fail due to steel tensile failure, bond detachment, or rock mass fracturing through uplift. In this study, uplift failure of the rock mass surrounding rock anchors was simulated using both physical and numerical models. The physical models used a specially designed testing rig with predefined sizes and different joint layouts to simulate rock mass uplift failure. The numerical models were calibrated using the physical models and used to investigate scenarios involving increased complexity and greater depths. This paper presents the load distribution within rock masses with orthogonal joints when exposed to an anchor load. Extensive analysis of the numerical models revealed that symmetrical load arches were induced in rock masses that contained a joint set oriented parallel to the loading direction. However, joints that were obliquely oriented relative to the anchor axis induced asymmetrical load arching. The greatest displacement occurred in the direction parallel to the joint set with the smallest angle to the anchor loading axis. Large-scale models with zero or near-zero in situ horizontal stress revealed that the load capacity in a rock mass with continuous vertical joints was relatively low, especially when compared to rock masses with discontinuous vertical joints. It was observed that the uplift capacity of the rock mass around an anchor decreased if the load arches of adjacent anchors overlapped; consequently, a decrease in anchor spacing was found to correspond to a decrease in uplift capacity.

Research on kinematics modeling and path planning of a hyper-redundant continuum robot

It has always been the case that work in confined spaces has high difficulty and complexity, and robots are usually required to replace humans to perform the corresponding operations. For the maintenance work in the fuel tank of a certain type of aircraft, a continuum robot with 32 staggered orthogonal joints is designed in this paper. To solve the motion problem of this robot, this paper combines the end-following method with the Jacobi inverse kinematics method, and proposes an end-following-segmented Jacobi method, which improves the accuracy and efficiency of the inverse kinematics solution. A ray path-planning algorithm for continuum robots is proposed for the job requirements of this robot and the specific operating environment inside an airplane fuel tank, and it is compared with the rapidly-exploring random trees (RRT) algorithm and particle swarm optimization (PSO) algorithm. The experimental results show that the planning time of the ray path-planning algorithm is less compared with the RRT algorithm and the PSO algorithm, and the paths obtained are shorter. Finally, a path-following simulation is performed on a 32-joint continuum robot model to verify the followability of the ray path algorithm.

A zone of columnar joints beneath the roof of a granitic pluton: The Okueyama granite, southwestern Japan

AbstractIgneous rocks are fractured during cooling from magma to form cooling joints, which are typically columnar joints in volcanic rocks, while orthogonal joints are considered typical for plutonic rocks. We performed a 3D study of joint systems in a granitic batholith of the Okueyama granite in western Japan, which has its roof and its internal structures from the roof to 1000 m downward exposed. We used an unmanned aerial vehicle (UAV) to observe the joints in outcrops from various angles. Based on our study, we propose a schematic model for joint systems in a granitic pluton. A granitic pluton has zones of rock columns below the roof and next to the wall. The rock column zone below the roof is as thick as 300 m, and its higher portions form steep cliffs, probably because of increased resistance to weathering. The axes of the rock columns are nearly vertical below the roof and gently plunge next to the walls, with high intersection angles with the wall. The distribution of columnar joints near only the roof and walls suggests that the granite cooled more rapidly near the roof and walls than in the core of the pluton. When the granite was jointed by parallel joints during cooling, the rock slabs between the parallel joints near the roof and the walls are subdivided into columns with polygonal cross‐sections. This suggests that the granite was fractured by parallel joints at a temperature immediately below the solidus, after which the rock slabs were subdivided into rock columns during further cooling.

Joint Studies In The Western Part Of Ikom-Mamfe Basin, Lower Benue Trough, Nigeria

The Ikom-Mamfe basin, also called the Mamfe embayment, is a bifurcation of the Benue trough in southeastern Nigeria and southwestern Cameroun. The basin is about 130km long, 60km wide basin and is filled with about 4km thick sedimentary rocks. Deformational events led to gentle folding of rocks in the basin and emplacement of magmatic rocks. Systematic and detailed field studies were carried out in eight (8) locations within the study area, in which the orientations of 1437 joints and 102 veins were acquired. Two sets of orthogonal joints observed in the study exhibited symmetry with respect to the directions of the fold axes and were dominated by high-angle dips averaging about 80o. This implies a syntectonic origin of these structures also during their propagation, the maximum principal stress directions (σ1) were orientated in two different directions NW- SE and NNE-SSW for DI and D2 respectively. The relative strength of deformation during DI was greater than D2 and it was also unfolded that the ‘ac’ extension joints trending NW- SE and NNE-SSW hosted relatively thicker veins in both DI and D2. These joints served as better conduits for mineralizing fluids and also most suitable directions for future prospecting.

The formation of orthogonal joint systems and cuboidal blocks: New insights gained from flat-lying limestone beds in the region of Havre-Saint-Pierre (Quebec, Canada)

Vertical orthogonal joints are a common feature in shallow crustal rocks. There are several competing theories for their formation despite the ubiquity. We examined the exceptional exposures of orthogonal joints in flat-lying Ordovician limestone beds from the Havre-Saint-Pierre Region in Quebec, Canada (north shore of Saint-Lawrence River) to test conceptual models of joint formation in a natural setting. In the region, the spacing of cross-joints is consistently larger than the spacing of systematic joints by a factor of 1.5 approximately. The joint-spacing-to-bed-thickness ratios (s/t) are much larger in these beds (s/t = 4.3 for systematic joints, and 6.4 for cross-joints) than those in higher strained strata along the south shore of the Saint-Lawrence River (s/t = 1), highlighting the effect of tectonic strain in decreasing fracture spacing and block size. The high values of s/t indicate that cross-joint formation was unlikely caused by a switch from compression to tension once a critical s/t ratio for systematic joints was reached (as hypothesized in previous studies). We proposed a new model for the formation of orthogonal joint systems where the principal stress axes locally switch during the formation of systematic fractures. The presence of ladder-shaped orthogonal joints suggests a state of effective stress with σ1∗≫0 > σ2∗>σ3∗ and where σ2∗-σ3∗ is within the range of fracture strength variability at the time of fracture. This research provides a new mechanical model for the formation of orthogonal joint systems and cuboidal blocks.

Geländer Molecules with Orthogonal Joints: Synthesis of Macrocyclic Dimers.

Orthogonal joints, understood as connections with an angle of 90°, were introduced in the design of the "Geländer" model compounds 1 and 2. The banister, consisting of a conjugated carbazole dimer linked by either 1,3-butadiyne (2) or a single thiophene (1), wraps around an axis composed of a phthalimide dimer due to the dimensional mismatch of both subunits, which are interconnected by phenylene rungs. The "Geländer" structure was assembled from a monomer comprising the 1,4-diaminobenzene rung with one amino substituent as part of a 4-bromo phthalimide subunit forming the orthogonal junction to the axis, and the other as part of a masked 2-ethynyl carbazole as orthogonal joint to the banister. The macrocycle was obtained by two sequential homocoupling steps. A first dimerization by a reductive homocoupling assembled the axis, while an oxidative acetylene coupling served as ring-closing reaction. The formed butadiyne was further derivatized to a thiophene, rendering all carbons of the model compound sp2 hybridized. Both helical structures were fully characterized and chirally resolved. Assignment of the enantiomers was achieved by simulation of chiroptical properties and enantiopure synthesis.

Geländer Molecules with Orthogonal Joints: Synthesis of Macrocyclic Dimers

Geländer Molecules with Orthogonal Joints: Synthesis of Macrocyclic Dimers

Influence of brace-to-chord angle on the seismic behavior of circular hollow section X-joints under in-plane bending

This paper studied the influence of brace-to-chord angle (BCA) on the in-plane flexural behavior of circular hollow section (CHS) tubular X-joints. The study begins with three CHS tubular X-joint specimens (one orthogonal joint with BCA of 90°, two skew joints with BCA of 70° and 55° respectively) under cyclic in-plane bending moment (IPBM). The test results showed that specimens mainly failed in tearing of the chord wall near the brace/chord intersection after experienced large plastic development, and the crack propagation rate of the chord wall of the skew specimens under negative IPBM is obviously faster than that under positive IPBM, while the propagation rates of the orthogonal specimen under two IPBM is similar. The ductility, strength and energy dissipation of the X-joints are deeply affected by BCA. Decreasing BCA is beneficial to the ductility ratio under positive IPBM, but it is not conducive to the ductility ratio under negative IPBM; decreasing BCA can increasing the flexural strength; both the skew joint with large BCA and the orthogonal joint exhibit higher energy dissipation behavior than that of the skew joint with small BCA. These observations is further confirmed by a simple load transferring model proposed in this study. Finite element (FE) parametric analysis is then carried out to verify test and the load transferring mechanism analysis results. Moreover, FE and test results showed that the negative strength Miu− (under negative IPBM) and the positive strength Miu+ (under positive IPBM) of the orthogonal joints are close, but Miu− of the skew joints are larger than the counterpart of Miu+, and the ratio of Miu− /Miu+ is increased (from slightly more than 1.0 to above 1.2) as BCA decreased (from 70° to 35°).

Study on the Size and Occurrence Effects of Equivalent Elasticity Modulus of Orthogonal Random Jointed Rock Masses

Under the engineering background of a + 144-m mining platform on an open pit slope of Xinqiao Mining Corporation, the eigenvalue distribution function of joints was acquired based on the massive statistics of field joints. Next, an orthogonal random joint model was constructed using the Monte Carlo method based on the UDEC software platform. Subsequently, the representative elementary volume (REV) size and occurrence effects of the equivalent elasticity modulus of the orthogonal random jointed rock mass were explored through numerical experiments with lots of discrete elements. The results showed that the equivalent elasticity modulus of the orthogonal random jointed rock mass was of evident size effect, and the relationship between the mean equivalent elasticity modulus Eeq and the REV size of the rock mass followed the negative power function distribution. Before the model size reached the REV size, its Eeq was greatly discrete. Under different joint angles, both the standard deviation σf and coefficient of variation δ of the equivalent elasticity modulus of this model presented discrete distribution. As the model size reached the REV size, the mean equivalent elasticity modulus Eeq showed “two-high and one-low” morphological distribution. Eeq was small when the main joint angle was α∈[30°, 40°], but it was large when α = 0° or 90°. δ was taken as 10%, so the REV size of the corresponding Eeq was 10 m × 20 m. When the model size reaches the REV size, the occurrence effect of its equivalent elasticity modulus was no longer significant.

Characteristics and Dominant Factors for Natural Fractures in Deep Shale Gas Reservoirs: A Case Study of the Wufeng-Longmaxi Formations in Luzhou Block, Southern China

Abstract In southern Sichuan Basin, the main production layers are characterized by deeply buried, high stress difference, and complex structural conditions. The Luzhou area is far from large faults, and natural fractures are greatly important for shale gas storage and production. Multi-scale natural fractures control the migration, enrichment, and preservation conditions of shale gas, and facilitate the formation of complex fracture network under the action of hydraulic fracturing. In this study, based on the outcrops, drilling cores, geochemical tests, thin section, and other experiments, the development characteristics of the Wufeng-Longmaxi shale in the Luzhou block, Southern China, are statistically analyzed, and the controlling factors (e.g., tectonic factors, organic matter, mineral components, mechanical properties) are discussed in details. Fractures observed in the outcrops are mainly regional fractures with two groups of orthogonal joints. Similarly, fractures observed in the core are also mainly joints fractures perpendicular to the laminae with three typical features (high-density, high-angle, and unfilled). In detail, steeply dipping fractures (75-90°) account for 78.1% of all fractures, with 85.1% being unfilled, 78.1% having a longitudinal extension less than 4 cm, and 65.1% having a spacing less than 2 cm. In brief, there exist cross-scale similarity among outcrops, cores, and microscopic thin sections, which is critical to the shale gas preservation conditions. Based on this understanding, further research is conducted on the relationship between the fracture density and gas content, which shows that (i) when the fracture density is less than 122 number/m, TOC content and fracture density together positively dominate gas content; (ii) when fracture density exceeds 122 number/m, gas content appears negative with fracture density, and TOC content is not the critical factor anymore. The above study establishes quantitative limits for shale gas preservation in the study block. It may assist in providing references for determining the sweet spot area and further deep shale gas exploration and development in the southern Sichuan Basin.

Hybrid Antagonistic System With Coiled Shape Memory Alloy and Twisted and Coiled Polymer Actuator for Lightweight Robotic Arm

Artificial muscles have been developed for various input power sources. Among them, thermally driven actuators can be easily actuated at a low voltage without an additional device using the Joule heating. Therefore, these actuators can be considered suitable for developing lightweight robots. Shape memory alloy or twisted and coiled actuators are typically used as both have the advantage of large specific power; however, their disadvantages include speed, hysteresis, and initial tension. In this letter, we developed a hybrid antagonistic system that alleviates the drawbacks of both actuators. Control methods for hysteresis are applied based on actuator models and controlling the cooling fan. The joint position control experiment was conducted, and the advantages of the two actuators could be utilized based on the results. Furthermore, a lightweight robot arm was developed using the hybrid system. By applying the hybrid system, the robotic arm could be fabricated with a light weight of about 1 kg and can move in 4 degrees of freedom. The robotic arm was possible to perform angle control of the elbow with the developed control algorithm. In addition, it was combined with a 3 degrees of freedom orthogonal joint to replace the role of the shoulder, and the robotic arm was able to demonstrate the motion of activities of daily living.

Application of Cable Climbing Robot Automation Control Technology in Bridge Cable Measuring System

According to the traditional bridge cable measurement system, the accuracy of the bridge cable measurement is low, and the measurement time is long. Based on the automatic control technology of the climbing robot, a new bridge cable measurement system is designed. We design system hardware through CIS drive circuit, main controller, and communication module; design system software on the basis of hardware design; obtain the motion control equation of orthogonal joint cable climbing robot through DH transformation; and apply this equation to the bridge cable measurement system. The bridge cable measurement model is constructed, and the bridge cable measurement system design is completed through the system hardware design and software design. The simulation results show that the designed system has higher accuracy in measuring bridge cables and shorter measuring time.

An obelisk‐shaped granitoid tower at Mt. Jizogadake in the Southern Alps of Japan: A 3‐D morphological study

AbstractWell‐developed tors and associated boulder fields are present in exposed granitoid pluton, but their geomorphological origins have not been fully addressed. Although the tor‐like features are commonly attributed to the orthogonal joint system along which weathering proceeds and the weathering materials are removed, the majority of previous studies lack three‐dimensional (3‐D) morphological observations. One of the well‐known granitoid rock towers in Japan, namely, the obelisk at Mt. Jizogadake in the Japanese Southern Alps, was investigated using unmanned air vehicles (UAVs). A 3‐D observation of the granitoid obelisk found that it is shaped by columnar joints with an undulation along a long axis and irregularly shaped cross‐sections. Because of these features and intersection angles between the rock columns and exposure surfaces, the obelisk exhibits a peculiar morphology appearing as a heap of rock blocks when observed from the ground. The columnar jointing might have occurred in a marginal zone of the granitoid pluton due to faster cooling rates. The 3‐D observations also confirmed the columnar joints formation was predated by high‐angle, planar joints. The columnar joints divide the rock mass between those planar joints. This may imply that the high‐angle joints would have formed probably during cooling under the presence of tectonic and thermal stresses.

The Formation of Orthogonal Joint Systems: New Observations from Limestone Beds in the Region of Havre-Saint-Pierre (Quebec, Canada)

The Formation of Orthogonal Joint Systems: New Observations from Limestone Beds in the Region of Havre-Saint-Pierre (Quebec, Canada)

3-Dimensional Modeling and Attitude Control of Multi-Joint Autonomous Underwater Vehicles

To achieve rapid and flexible vertical profile exploration of deep-sea hybrid structures, a multi-joint autonomous underwater vehicle (MJ-AUV) with orthogonal joints was designed. This paper focuses on the 3-dimensional (3D) modeling and attitude control of the designed vehicle. Considering the situation of gravity and buoyancy imbalance, a 3D model of the MJ-AUV was established according to Newton’s second law and torque balance principle. And then the numerical simulation was carried out to verify the credibility of the model. To solve the problems that the pitch and yaw attitude of the MJ-AUV are coupled and the disturbance is unknown, a linear quadratic regulator (LQR) decoupling control method based on a linear extended state observer (LESO) was proposed. The system was decoupled into pitch and yaw subsystems, treated the internal forces and external disturbances of each subsystem as total disturbances, and estimated the total disturbances with LESO. The control law was divided into two parts. The first part was the total disturbance compensator, while the second part was the linear state feedback controller. The simulation results show that the overshoot of the controlled system in the dynamic process is nearly 0 rad, reaching the design value very smoothly. Moreover, when the controlled system is in a stable state, the control precision is within 0.005%.

Effect of Load Inclination on the Bearing Capacity of Jointed Rock Foundations

In this paper, upper bound method of limit analysis is used to obtain the vertical and inclined bearing capacity of rock masses containing two orthogonal joint sets. The spacing of the joint sets is assumed to be large compared to the footing width. Different orientation angles are considered for the joints, and the Mohr–Coulomb failure criterion is employed for both the intact rock and the joint sets. Analytical expressions are derived for the bearing capacity of a strip footing resting on a jointed rock subjected to vertical loading. Then, the effect of load inclination on the bearing capacity is incorporated into the analytical equations by means of inclination coefficients. The findings are compared to the other solutions existing in the literature. The results of this study show that increasing the joint friction angle leads to decreasing the inclination coefficient. Moreover, increasing the joint orientation angle with respect to the horizontal direction results in decreasing the inclination coefficients. The obtained results are presented in tabular form that can be used easily for practical purposes.

Experimental study on orthogonal joints in cross-laminated timber with self-tapping screws installed with mixed angles

Cross-laminated timber (CLT) is increasingly being used in lateral load resisting systems of multi-storey buildings. Conventional in-plane CLT shear walls can be transformed into CLT core-wall structures with enhanced lateral strength and stiffness when the individual walls are connected orthogonally. In this paper, experimental studies are presented on orthogonal CLT joints with self-tapping screws (STS) installed with mixed angles, i.e. different installation angles between the STS axis and the plane of the CLT surface. A total of 59 orthogonal joint specimens were tested in 9 different configurations to derive the relevant joint performance parameters from monotonic and cyclic tests. The joint specimens used five-layer and seven-layer CLT panels connected by ∅8 mm or ∅12 mm STS. Different ratios of STS installed inclined and STS installed at 90° to the CLT surface were investigated to determine an optimum ratio of STS for enhanced joint performance. It was found that a ratio of one 90° STS for every two inclined STS ensured significant increase in ductility and displacement capacity of approximately three times when compared to specimens with only inclined STS. A minimum moderate ductility was achieved in all test series where the primary failure mode was STS withdrawal. It was found that 90° STS contributed to both strength and stiffness in joints that also contained inclined STS. The average experimental overstrength was 1.7 for most joint configurations. Existing analytical models were adequate in estimating strength but inadequate to estimate stiffness.

A new interpretation for formation of orthogonal joints in quartz sandstone

Abstract Two vertical and orthogonal systematic joint sets are generally arrayed in a grid pattern on the bedding surface, which are the significant features of flat-lying sandstone terrains. Although extensive researches are reported on this topic, many fundamental problems have still not been solved. Such mutually perpendicular opening-mode fractures are an obvious manifestation of effective tensile stresses in two orthogonal directions in the horizontal bedding plane. A good understanding of these orthogonal joint systems is a key to structural analysis, landscape interpretation, and guidance of resolving a number of very practical problems in engineering, mining and hydrologic projects. Based on an anatomic investigation on the orthogonal joints in the Potsdam sandstone of Cambrian age at Ausable Chasm (New York State, USA) and Beauharnois (Quebec, Canada), we proposed that the orthogonal joints may result from the auxetic effects of quartz-rich sandstone rather than local or regional rotation of the maximum tensile stress (σ3) direction by about 90°. The sandstone beds with negative Poisson's ratios are so fascinating that, when placed under vertical burial compression and layer-parallel extension in one direction (σ3), it becomes stretched in the transverse direction (σ2), producing two orthogonal sets of mutual abutting and intersecting joints (J1 and J2 normal to σ3 and σ2, respectively), and both are normal to the bedding surface. Joint set J1 is more closely-spaced than J2 by a factor of ∼3.3, which is correlated with an average Poisson's ratio of −0.3 for the Potsdam sandstone at the time of joint formation.

A two-step algorithm for joint EigenValue decomposition - Application to canonical polyadic decomposition of fluorescence spectra

In this paper, we propose a new Joint EigenValue Decomposition (JEVD) algorithm. JEVD problem belongs to the family of joint diagonalization problems. Hence, JEVD algorithms aim at estimating the common basis of eigenvectors of a matrix set. This problem occurs in many signal processing applications. It has notably allowed to develop efficient algorithms for the Canonical Polyadic Decomposition (CPD) of multiway arrays. The proposed JEVD algorithm is based on an original two-step approach. The first step consists in transforming the considered matrix set into a set of positive definite matrices. In this purpose, we introduce an ad hoc joint symmetrization algorithm. This first step allows us to transform the JEVD problem into a simpler orthogonal joint diagonalization problem. The second step is then performed using an efficient orthogonal joint diagonalization algorithm of the literature. Eventually, the performance of the proposed approach is deeply investigated in the CPD context of multidimensional fluorescence data. More particularly, we consider difficult scenarios such as the cases of an overestimated rank and highly correlated factors.