Link Angles Research Articles

Impact of Vertical and Diagonal Shear Reinforcement on the Structural Integrity of a Deep Beam

This research investigates the shear strength behaviour of deep beams with different angles of inclinations of the transverse reinforcements with the longitudinal reinforcements. A mix ratio of 1:1½:3 of concrete was used in this investigation with a total number of three (3) deep beam models of 150×300×750 mm and the characteristic compressive strength of concrete used for the production of the beams was determined to be 14.5 N/mm2. The study concludes that the ultimate resisting load of the beam depends on the angle of inclination of the shear links and maximum with 90o inclination angle of the shear links which decreases with a decrease in the angle of inclination. Hence, all shear reinforcement must not be inclined at an angle other than 90o to the longitudinal reinforcement to avoid shear-compression failure along the shear diagonal.

Analysis of the third class mechanism using the modeling method in the Mathcad software environment

Purpose. To carry out a kinematic analysis of a flat twelve-link hinged mechanism with three leading links, the basis of which is a structural group of links of the third class of the fourth order with rotational kinematic pairs, which is used in technological equipment. Methodology. The kinematic study of a flat complex mechanism of the third class with three leading links was performed using the mathematical modeling method in the Mathcad software environment. Findings. Using the method of mathematical modeling, the mechanism was presented in the form of free vectors built on its links, for which, taking into account the presence of three leading links, three vector contours were selected, which made it possible to draw up a system of vector equations of their closedness with further solving by a numerical method in the Mathcad software environment. The functions of the rotation angles of the mechanism links, their angular velocities and accelerations were obtained in analytical and graphical form depending on the rotation angle of the first driving crank of the mechanism, the calculation of the angular velocities and accelerations of all the driven links of the mechanism was performed. Originality. A sequence was developed and a kinematic study of a complex planar mechanism of the third class with three leading links was done, the basis of which is a structural group of links of the third class of the fourth order. Schematic modeling of the mechanism with three leading links was performed, a visualization schedule of its kinematic scheme was built, and a valid version of its assembly was obtained from many possible ones, for which the values of kinematic parameters of all its links were determined. Practical value. An analysis of the effect of the kinematic parameters of the three leading links of the third-class mechanism on the movement of the working body of the technological equipment was carried out. From the analysis of the obtained research results for the cycle of the mechanism the reason was found for the incomplete technological stoppage of the link, which should provide the working body of the machine for the required period of time. Recommendations of the elimination were made to identify the deficiency and proposals for the need to improve the drive of this equipment.

Optimal design of a new redundant spherical parallel manipulator with an unlimited self-rotation capability

Abstract This paper deals with the optimization of a new redundant spherical parallel manipulator (New SPM). This manipulator consists of two spherical five-bar mechanisms connected by the end-effector, providing three degrees of freedom, and has an unlimited self-rotation capability. Three optimization procedures based on the genetic algorithm method were carried out to improve the dexterity of the New SPM. The first and the second optimizations were applied to a symmetric New SPM structure, while the third was applied to an asymmetric New SPM structure. In both cases, the optimization was performed using an objective function defined by the quadratic sum of link angles. In addition, certain criteria and constraints were implemented. The obtained results demonstrate significant improvements in the dexterity of the New SPM and its capability of an unlimited self-rotate in an extended workspace. A comparison of the self-rotation performances between the classical 3-RRR SPM (R for revolute joint) and the New SPM is also presented.

Novel adaptive fuzzy control for pendubot with actuator faults and uncertainties: Design and experiments

Pendubot has been widely applied as a benchmark platform for control research and education. In this paper, a novel adaptive fuzzy hierarchical sliding mode controller (AFHSMC) is proposed for the pendubot under actuator faults and uncertainties. The proposed controller is designed by combining hierarchical sliding mode control (HSMC), fuzzy logic control (FLC), and balancing composite motion optimization. The proposed controller preserves many advantages such as having a straightforward structure, simple implementation, chattering reduction, and high precision and robustness. The stability of the proposed controller is ensured by using the Lyapunov approach. To verify the control performance, various numerical simulations and experiments are conducted on a pendubot under conditions that involve actuator faults and uncertainties. Compared to the conventional HSMC and FHSMC controllers, the proposed AFHSMC improves by 0.43% and 0.38% for tracking precision of the first link's angle estimate, 3.26% and 0.08% for the second link's angle estimate when influenced by uncertainties, as well as 65.23% and 12.24% for the first link, 83.95% and 16.15% for the second link when influenced by faults.

To determine the maneuverability of three-link road trains type “B-triple” with steered axles of semi-trailers dollies

In recent years, the development of container transportation served as a powerful impetus for increasing the length of vehicles, especially road trains, which is due to a number of advantages regarding the transportation of large-sized freight in a container. Today, the whole range of containers is transported by two-link road trains consisting of a tractor vehicle and semi-trailer. The efficiency of such transportation can be increased by means of three-link road trains capable of transporting either three (two 20-foot and one 40- or 45-foot) or four 20-foot containers. This organization of transportation will lead to energy savings and a reduction in environmental pollution due to the reduction of vehicles. However, there is a problem with the maneuverability and stability of such vehicles. The paper developed a kinematic model of three-link road train type “B-triple” with steered axles (front or rear) of semi-trailer dolly with a dual drive control for these axles. Based on folding angles of road train links and drive control transmission ratios of the axles of semi-trailer dolly, the main indicators of road train maneuverability are determined – road train links trajectories displacement relative to the vehicle trajectory and road train overall traffic lane. It was established that when entering a turn with slight differences in folding angles of road train links, the steered axles of semi-trailer dolly turn in the direction opposite to the direction of a turn, thereby reducing the overall traffic lane. During circular motion, the overall traffic lane of road train with steered semi-trailers decreased by almost 2 m, but such road train does not meet the maneuverability requirements. The search for ways to improve the maneuverability of three-link road trains should be sought in the designs of three-link road trains.

Machine Learning-Based Multiagent Control for a Bunch of Flexible Robots

In this paper, two novel methodologies of employing machine learning (here, the type-2 fuzzy system) are presented to control a multiagent system in which the agents are flexible joint robots. In the previous methods, the static mode controller has been investigated, which has little flexibility and cannot measure all the states of the system, but in the method presented in this paper, we can eliminate these disadvantages. The control signal is consisting of feedback from the output and the estimated states of the system. In the first method, the control signal coefficients are calculated from the linear matrix inequality (LMI), followed by a type-2 fuzzy system that adds the compensation signal to the control signal. In the second method, the type-2 fuzzy system is directly used to estimate the control signal coefficients which do not employ LMI. Both methods have their disadvantages and benefits, so in general, one of these two methods cannot be considered superior. To prove the effectiveness of the two proposed methods, a topology with four robots has been considered. Both proposed methods have been evaluated for controlling the angle and speed of the robot link. Also, another simulation was made without using the fuzzy system to verify the importance of our methods. Simulation results indicate the proper efficiency of proposed methods, especially in presence of uncertainty in the system.

РАЗРАБОТКА МОДЕЛИ КИНЕМАТИКИ ПАЛЬЦЕВ ЧЕЛОВЕЧЕСКОЙ РУКИ, ПРИМЕНЯЕМЫХ В РОБОТИЗИРОВАННЫХ ПЕРЧАТКАХ

This paper considers the design of an anthropomorphic manipulator in the form of a human hand. The aim of the work is to describe the kinematics of a robotic hand, using the example of one finger. Based on the Denavit–Hartenberg algorithm, a kinematic model is developed for one finger of the robotic hand. The working area of the robotic finger is determined, taking into account the limitations on the rotation angles of the finger phalanges. These kinematic equations are used to solve the problem of the speeds of one fingertip. According to the results of modeling for given speeds of the fingertip, the dependencies of the rotation angles of the robotic hand links were obtained. Unlike the previously used models, the developed one makes it possible to take into account the presence of a geometric constraint between the proximal and distal finger phalanges, which is structurally made with an inextensible thread. The results of the work can be used in the design and manufacture of new robotic gloves.

Interference analysis between NGSO systems based on the beam coverage and link angle

The existing interference assessment methods usually consider the special scenario of earth station coincidence. However, in practice, earth stations such as gate stations are sparsely distributed and often do not coincide. Aiming at the problem of how to efficiently calculate the co-frequency interference between Non-Geostationary Satellite Orbit (NGSO) systems with high complexity and a large amount of data, the influencing factors of interference scenes between NGSO systems with non-earth station coincidence are analyzed. The time-varying expression of the bit error rate (BER) of the interference evaluation index to measure the system performance is derived. An interference analysis method based on the beam coverage and link angle is proposed. In this method, four interference time-varying parameters are reduced to two. One of them is associated with the distance between earth stations, which is used to rapidly evaluate the probability of harmful interference between NGSO systems. It provides a reference for the construction of the spacing of earth stations.

Anisotropic ionospheric scintillation in weak scattering regime

Transionospheric radio signals might undergo random modulations of their amplitude and phase caused by scattering on irregular structures in the ionosphere. These scintillation phenomena are highly anisotropic, depend on local geomagnetic field configuaration and on the relative position of the signal receiver and scattering irregularity. We derive analytical expressions of anisotropic amplitude and phase scintillation indices using the model of a thin random phase screen. These results extend the classical derivations of [C. Rino, Radio Sci. 14, 1135 (1979)] to a larger domain of applicability including very slant propagation links of the radio wave signals. The derived generalization is based on the assumption that the ionospheric scattering layer has a spherical symmetry as opposed to the original Rino’s assumption of a plan-parallel ionospheric layer. The derived scintillation indices have the simpler analytical form, determine the regions of enhanced scintillation by taking into account the finite curvature of the Earth and of the ionospheric shell, and are divergence-free for large zenith angles of propagation links. For the illustration we discuss the geometric enhancement of scintillation for communication links via a geostationary beacon satellite over the equator.

Time-varying disturbance-observer-based tracking control of uncertain flexible-joint manipulator

This paper presents a time-varying disturbance-observer- (TVDO-) based improved sliding-mode control (ISMC) method to achieve tracking control of uncertain flexible-joint manipulator (UFJM). Based on the UFJM dynamic model and its ideal dynamic model regardless of uncertainties, an error system in the form of an integral chain with disturbances is established. The tracking control objective of the UFJM is achieved by designing the TVDO-based ISMC law to guarantee the ultimate boundedness of link angle errors for the error system. Specifically, by employing the TVDO, the disturbances in the error system are estimated. By using the TVDO-based ISMC method, the uncertainties are overcome, and the chattering problem is reduced. The contradiction between high tracking accuracy and suitable torque without peaking phenomenon is alleviated. Finally, the stability analysis of the closed-loop control system is presented, and the validity of the proposed method is illustrated by simulation and experiment.

Force Analysis of Statically Balanced Serially Connected Manipulators Using Springs Based on Torque Compatibilities Associated With Accumulative Joint Angles

AbstractForce analysis with regard to serial connected manipulators is discussed thoroughly in the past. However, force analysis of statically balanced manipulator using springs has not been widely addressed because spring forces and motions do not share an immediate association. In this article, spring forces are represented as accumulative joint angles of links crossed by springs and attached angles/lengths of springs. Torque equilibrium equations regarding the preconnected joint of a typical link as contributed by gravity force and spring force can be inwardly formed link by link from the end link. Compatibility with the same accumulative joint angle can be formulated under static balance conditions. Hence, spring attachment parameters such as spring stiffness and attachment lengths are constrained by given link properties and spring attachment angles. Thus, spring forces can be determined by a chosen set of stiffness and attached lengths of springs, and the joint reaction force can then be determined. Example figures of 3-degrees-of-freedom (DOFs) manipulators show that joint reaction forces are reduced by 22.6%, 40.1%, and 75.7% at joints 1, 2, and 3, respectively, than those without springs. It is found that besides balancing gravity, the statically balanced manipulator is with lower joint reaction forces. Hence, the manipulator can be more lightweight by using compact joints and links with the same material. Furthermore, the static and dynamic performance of the manipulator can be improved by the effect of reduced joint reaction forces as well.

Accurate Phase Angle Measurement of Backscatter Signal under Noisy Environment

Backscatter communication is an emerging wireless access technology to realize ultra-low power terminals exploiting the modulated reflection of incident radio wave. This paper proposes a method to measure the phase angle of backscatter link using principal component analysis (PCA). The phase angle measurement of backscatter link at the receiver is essential to maximize the signal quality for subsequent demodulation and to measure the distance and the angle of arrival. The drawback of popular phase angle measurement with naive phase averaging and linear regression analysis is to produce erroneous phase angle, where the phase angle is close to $\pm\frac{\pi}{2}$ radian and the signal quality is poor. The advantage of the proposal is quantified with a computer simulation, a conducted experiment and radio propagation experiments.

Optimization of Design Parameters Using SQP for an Agricultural Pipe Extraction Device

Removal of agricultural pipes used in crop support and greenhouse agriculture is manpower-intensive. However, most agricultural workers are elderly. Therefore, auxiliary devices should be used to allow pipe removal with as little force as possible. In this study, the design parameters of an extraction device were optimized within constraints to minimize the force required to remove agricultural pipes. The optimization parameters are the length of each link and the initial link angle of the device. The driving force, according to the design parameters, was calculated by applying the theory of kinematics. An optimal design plan was derived using an optimization algorithm to minimize the force driving the device within the desired constraint. As a result of the optimization, it was confirmed that the force required to remove the pipe was reduced by 87.1% compared with the initial design value and was designed to suit the user’s convenience.

Virtual holonomic constraints based super twisting sliding mode control for motion control of planar snake robot in the uncertain underwater environment

In this article, the snake robot having nine links with eight joints is considered for serpentine motion in the underwater environment. The movement of a snake robot occurs due to nonlinear drag forces and fluidic torque in underwater conditions. The uncertainties in drag forces and fluidic torque are considered to track the head angle and tangential velocity in this work. The virtual holonomic constraints are formulated to track all the joints by designing a controller for single joint. The parameters of gait pattern are obtained using the sliding surface. The sliding surface is formulated for head link angle and velocity tracking. Super twisting sliding mode control approach is proposed to deal with uncertainties, and results are compared with sliding mode control and adaptive sliding mode control. The robustness of controller is verified by inputting measurement noise. The significant improvement has been observed in chattering indicator and control effort by using the proposed super twisting sliding mode control. The investigation of this research article focuses on how to get almost chattering free operation in underwater uncertain environmental conditions with minimum control effort.

Relative Reshetikhin–Turaev Invariants, Hyperbolic Cone Metrics and Discrete Fourier Transforms I

We propose the Volume Conjecture for the relative Reshetikhin–Turaev invariants of a closed oriented 3-manifold with a colored framed link inside it whose asymptotic behavior is related to the volume and the Chern–Simons invariant of the hyperbolic cone metric on the manifold with singular locus the link and cone angles determined by the coloring. We prove the conjecture in the case that the ambient 3-manifold is obtained by doing an integral surgery along some components of a fundamental shadow link and the complement of the link in the ambient manifold is homeomorphic to the fundamental shadow link complement, for sufficiently small cone angles. Together with Costantino and Thurston’s result that all compact oriented 3-manifolds with toroidal or empty boundary can be obtained by doing an integral surgery along some components of a suitable fundamental shadow link, this provides a possible approach of solving Chen–Yang’s Volume Conjecture for the Reshetikhin–Turaev invariants of closed oriented hyperbolic 3-manifolds. We also introduce a family of topological operations (the change-of-pair operations) that connect all pairs of a closed oriented 3-manifold and a framed link inside it that have homeomorphic complements, which correspond to doing the partial discrete Fourier transforms to the corresponding relative Reshetikhin–Turaev invariants. As an application, we find a Poisson Summation Formula for the discrete Fourier transforms.

Design and dynamic analysis of jumping wheel-legged robot in complex terrain environment.

Wheel-legged robots have fast and stable motion characteristics on flat roads, but there are the problems of poor balance ability and low movement level in special terrains such as rough roads. In this paper, a new type of wheel-legged robot with parallel four-bar mechanism is proposed, and the linear quadratic regulator (LQR) controller and fuzzy proportion differentiation (PD) jumping controller are designed and developed to achieve stable motion so that the robot has the ability to jump over obstacles and adapt to rough terrain. The amount of energy released by the parallel four-bar linkage mechanism changes with the change of the link angle, and the height of the jump trajectory changes accordingly, which improves the robot's ability to overcome obstacles facing vertical obstacles. Simulations and real scene tests are performed in different terrain environments to verify obstacle crossing capabilities. The simulation results show that, in the pothole terrain, the maximum height error of the two hip joint motors is 2 mm for the obstacle surmounting method of the adaptive retractable wheel-legs; in the process of single leg obstacle surmounting, the maximum height error of the hip joint motors is only 6.6 mm. The comparison of simulation data and real scene experimental results shows that the robot has better robustness in moving under complex terrains.

Linear Regression Modelling of Actual and Designed Angles of a Four Bar Linkage using MATLAB

The study, linear regression modeling of actual and designed angles of a four bar linkage through MATLAB approach was successfully carried out. The researchers considered actual and designed angles data gotten through Simulink modeling and simulation in the MATLAB command window. The linear regression modeling was achieved using designed angles of +30, +30, -23 and 0 degrees with the corresponding actual position angles of -92.4196, -223.375, 0, +101.66 degrees. The correlation coefficient of -0.7022 and p-value coefficient of 0.2978 from data analysis indicated that there is negative and significant relationship between actual angle and designed positions angles; however, the linear graph showed some region of positive relationship. MATLAB analysis also computed the linear regression model between actual and designed positions angles. The root mean squared error was observed to be 121 with standard error of 65. 234. The P-value 0.2978 and degrees of freedom 2 of the linear regression model generated are consistent with the P-value and degrees of freedom of ANOVA model, that proves correctness of the model. The researchers made the following recommendations: To avoid failure of machines and mechanisms and to minimize operational noise, actual position angles of links must be computed before linkage configuration is carried out, this research can also be done in future using other advanced software for generalization.

"Linear Regression Modelling of Actual and Designed Angles of a Four Bar Linkage using MATLAB"

The study, linear regression modeling of actual and designed angles of a four bar linkage through MATLAB approach was successfully carried out. The researchers considered actual and designed angles data gotten through Simulink modeling and simulation in the MATLAB command window. The linear regression modeling was achieved using designed angles of +30, +30, -23 and 0 degrees with the corresponding actual position angles of -92.4196, -223.375, 0, +101.66 degrees. The correlation coefficient of -0.7022 and p-value coefficient of 0.2978 from data analysis indicated that there is negative and significant relationship between actual angle and designed positions angles; however, the linear graph showed some region of positive relationship. MATLAB analysis also computed the linear regression model between actual and designed positions angles. The root mean squared error was observed to be 121 with standard error of 65. 234. The P-value 0.2978 and degrees of freedom 2 of the linear regression model generated are consistent with the P-value and degrees of freedom of ANOVA model, that proves correctness of the model. The researchers made the following recommendations: To avoid failure of machines and mechanisms and to minimize operational noise, actual position angles of links must be computed before linkage configuration is carried out, this research can also be done in future using other advanced software for generalization.

Variable Dimensional Scaling Method: A Novel Method for Path Planning and Inverse Kinematics

Traditional methods for solving the inverse kinematics of a hyper-redundant manipulator (HRM) can only plan the path of the end-effector with a complicated solving process, where obstacle avoidance is also not considered. To solve the above problems, a novel method for solving inverse kinematics of HRM is proposed in this paper: the variable dimension scaling method (VDSM), which can solve complex inverse kinematics while avoiding obstacles. Through this method, the path of the end-effector is scaled under a certain proportion and is adjusted depending on the position of the obstacle, which has good universality. The number of link angles changed is as small as possible in the process of achieving the end-effector moving along the desired path. With the redundancy of HRM, obstacle avoidance can be implemented in any environment by the proposed method. Through simulation and experiments in different environments, the above advantages of VDSM are verified.

Effect of Eu3+ on the Structural, Magnetic and Mössbauer Spectroscopy Studies of Copper Ferrite

Here, theoretical and practical methods were used to study the impact of Eu3+ substitution on copper ferrites. The spinel cubic structure of the synthesised samples is crystalline, and XRD analysis revealed the presence of a trace amount of the impurity Fe2O3 phase. The range of the estimated crystallite sizes is between 18 and 27 nm. FTIR spectra of the ferrites exhibited the presence of functional groups of spinel ferrites. The temperature-dependent Mössbauer spectra of CuFe2-xEuxO4 (x = 0, 0.01, 0.02, 0.03) (CEF) were collected at 300 K, 200 K, 100 K, and 14 K. Room temperature spectra consist of asymmetrically broadened sextets and quadruple split lines. The intensity of quadrupole split lines decreases along with the reduction in temperature. The observed changes in the structure of the Mössbauer spectra are typical of nanosized particles. The presence of paramagnetic lines at temperatures lower than the Curie temperature, asymmetric lines with sharp external fronts, and significantly diffused internal fronts is a sign of superparamagnetic relaxation. The partial substitution of Fe3+ ions by Eu3+ ions causes the redistribution of A and B cations, which leads to the alteration in angle and bond length of magnetic superexchange links. DFT calculations support the preference for octahedral Eu-doping in combination with the CuFe2O4 matrix, which results in local structural disorders that affect both the material's magnetic and electrical characteristics. The size, shape, interaction with the matrix, and crystallite characteristics all affect the material's magnetic properties. A weak ferromagnetic characteristic is indicated by the magnetic properties, and the magnetization values increase as Eu increases as a result of changes in crystallite size. As a result, our findings imply that synthesised samples are appropriate for applications involving hyperthermia.