Inverse Position Research Articles

Closed-Form Kinematics Solutions for Redundant Medical Robots with Joint Limits and Singularity Avoidance

Closed-form forward and inverse position, velocity and acceleration kinematics problems solutions are developed for a redundant medical robot family. Developed solutions allow one to choose a specific joint as a set one. Solutions work in constant time, suitable for real-time operation. Methods for joint limit and singularity avoidance are proposed. Simulation experiments are performed on simulated KUKA MED 14 r820 robot.

Design and Analysis of a New Non-Parasitic Parallel Mechanism for 2T1R Motion

Abstract Two-limb parallel mechanisms (PMs) can have several advantages, such as avoidance of mechanical collision, fairly simple architecture, easy assembly, and large workspace. The paper presents a novel two-limb three-degree-of-freedom (DOF) PM with two translations and one-rotation (2T1R) that are actuated by two sliders. The manipulator runs with decoupled position and orientation with forward position solution without parasitic motions. The main topological characteristics of the PM such as position and orientation characteristic (POC), DOF, and coupling degree are analyzed. Second, using the kinematic modeling method based on topological characteristics, the unified symbolic forward and inverse position solutions of the two configurations of the PM (I and II) are derived together with the workspace, rotational capacity, and singularity. Finally, a comparative analysis regarding the kinematics of two configurations (I and II) is carried out to find an optimal design configuration I of a PM for 2T1R motion.

Maternal behavior of dairy cows and suckling behavior of dairy calves in different cow-calf contact conditions

Cow-calf contact (CCC) has been suggested as an alternative to the common practice of early separation of dairy cow and calf. Increasing CCC poses challenges by reducing the machine milk yield and increasing separation stress. Part-time CCC may prove more feasible than full-time contact for farmers but may affect the maternal behavior of the cows. Gradually reducing the daily contact could gradually wean the calf off milk, preparing it for separation. This study aims to investigate 1) how cows' maternal behaviors toward their own calf are affected by part-time contact, and 2) whether calves' suckling behavior is reduced by reducing daily cow contact. Fifty-six dairy cows and their calves were assigned to either full-time (23 h/d) or part-time (10 h/d) cow-calf contact for 7 weeks (main rearing period). This was followed by 2 weeks of either reduced contact (50% in wk 8, then 25% of original contact time in wk 9) or unchanged contact. First, the maternal behavior of full and part-time cows was observed for 24 h in the third week of the main rearing period. Part-time cows spent less time nursing and grooming their own calf than full-time cows did. However, the amount of nursing in the inverse parallel position and the probability of a cow nursing a calf other than her own did not differ between the 2 treatments. Second, calf suckling behavior was observed for 24 h in both weeks of the reduced contact period. Averaged across both observations, total suckling time (i.e., time spent suckling any cow) was lower in part-time calves that experienced reduced contact compared with part-time calves with unchanged contact. In wk 9, time spent suckling only the dam was lower for full-time calves with reduced contact compared with part-time calves with unchanged contact. In conclusion, although we found a lower nursing and grooming time in part-time cows compared with full-time, we found no difference between treatments with regards to nursing in the inverse parallel position and nursing a calf other than the cow's own. The effect of gradually reducing cow-calf contact on calves' suckling time requires more research.

Ankle inversion proprioception measured during stair descent can identify chronic ankle instability

BackgroundIndividuals with chronic ankle instability (CAI) may experience recurrent ankle sprains and symptoms during daily activities such as stair descent, where the associated proprioceptive deficit is largely unevaluated. ObjectivesTo evaluate the reliability and validity of an ankle inversion discrimination apparatus for stair descent, and examine whether proprioceptive scores from this apparatus are associated with patient-reported symptoms. DesignCross-sectional study. MethodSixty-six participants volunteered in this study. The ankle inversion discrimination apparatus was purpose-built to assess ankle proprioception across four positions of ankle inversion (10°, 12°, 14°, and 16°) during stair descent. The Area Under the Receiver Operating Curve (AUC) was employed as the ankle proprioceptive discrimination score. ResultsTest-retest reliability ICC (3,1) for the whole group was 0.825, with 0.747 for the non-CAI group (95%CI = 0.331–0.920) and 0.701 for CAI (95%CI = 0.242–0.904). The CAI group performed at a significantly lower level than non-CAI on the ankle inversion discrimination apparatus for stair descent assessment (0.769 ± 0.034 vs. 0.830 ± 0.035, F = 33.786, p < 0.001). CAIT scores were strongly and significantly correlated with scores from this apparatus (Spearman's rho = 0.730, p < 0.001). ConclusionsThe ankle inversion discrimination apparatus for stair descent is reliable and valid for assessing task-specific ankle proprioceptive impairments in CAI. The strong and significant relationship found between ankle proprioception during stair descent and the severity of CAI suggests that rehabilitation programs focusing on deficits in ankle inversion proprioception during stair descent may improve self-reported instability in CAI.

Design and analysis of a novel 3-DOF planar parallel manipulator with two kinematic chains

In this work, to enlarge the workspace, a novel 3-DOF planar parallel manipulator (PPM) with two identical RRR kinematic chains is proposed, and this manipulator has a significant advantage in orienting the moving platform (MP) across a wide range of angles. Resorting to the closed-loop vector approach, the inverse position equation and Jacobian matrix of the novel manipulator are established. Payload performance, dexterity performance, and singularity of the proposed manipulator are analyzed based on the Jacobian matrix. To investigate the distribution characteristics of the constant orientation workspace, orientation workspace, and reachable workspace of the proposed manipulator, a numerical discretization method is employed. Under the same working mode and structural parameters, constant orientation workspace and reachable workspace comparisons between the proposed manipulator and another two traditional PPMs are conducted. Focused on three kinds of performance indices, link lengths optimization of the proposed manipulator is carried out. A 4-DOF pick-and-place equipment is fabricated, and the rotational and translational capabilities are verified based on two examples.

Elastostatic stiffness modeling and performance evaluation of a 2RPU-UPU parallel mechanism with two operation modes

This article presents a parallel mechanism (PM) that is consists of a UPU and two RPU limbs (U, P, R denote universal joint, prismatic joint, and revolute joint, respectively). It can switch into two different configurations with three degrees of freedom (DOFs), in which one configuration outputs two rotations and one translation, and the other outputs two translations and one rotation. Four joints should be actuated to fully control the PM. Inverse position analysis is carried out. Taking the compliances of links into consideration, wrench analysis of the RU chain is conducted by using screw theory. Stiffness matrix and compliance matrix of the limb are derived through the strain energy method. The PM’s overall stiffness matrix is then obtained according to the deformation compatibility equations. The theoretical results are compared with simulation results obtained in ANSYS, which shows a maximum deviation less than 0.6%. Static stiffness performance evaluation is carried out using the virtual work stiffness index. Performance distributions of the PM in two operation modes under external loads are obtained. The proposed stiffness modeling and performance evaluation could be helpful for optimal design and application investigation of the PM.

Energy spectrum and applications of Eckart plus Hellmann potential in hyperspherical coordinates

We investigate the approximate bound-state solutions of the N-dimensional Schrödinger equation with a combination of Eckart and Hellmann potentials via the asymptotic iteration approach. By the use of the Greene-Aldrich approximation, which is valid for small values of the screening parameter, we establish the N-dimensional energy spectrum and the N-dimensional radial wave function in approximate analytic form. In hyperspherical coordinates, the normalized radial wave function is expressed in terms of hypergeometric and Jacobi polynomials. To double-check the energy spectrum in hyperspherical coordinates, we utilize polynomial solutions in view of the asymptotic iteration approach. The expressions for the expectation values of inverse position, square of inverse position, kinetic energy, and square of momentum are derived in hyperspherical coordinates by using the Hellmann-Feynmann theorem. We also present the analytically calculated energy eigenvalues for Eckart plus Hellmann potential. We deduce special forms of the relevant potential, such as Eckart, Hellmann, and Hulthén potentials.

Kinematics and Workspace Analysis of 5-DOF Hybrid Redundantly Driven Mechanism

A novel 5-DOF (5-SPS)+5R2U hybrid redun-dantly driven mechanism (HRDM for short) is proposed, which can realize 3 translations and 2 rotations (3T2R) movements. (5-SPS)+5R2U parallel mechanism is composed of six driving limbs. Of which 5-SPS (S represents spherical pair, P represents prismatic pair) limbs are symmetrically distributed at the center point of static and moving platform have no restriction on the degrees of freedom of the mechanism. The middle limb (7R)U (R represents revolute pair, U represents Hooke joint) is connected to the static platform and the center point of the moving platform. It is jointly driven by constant velocity motor and servo motor, and plays a role of restraining the freedom of the whole mechanism. It is called hybrid redundantly driven limb (HRDL for short). Hybrid-driven mechanism and redundantly actuated mechanism can be integrated into one mechanism by HRDL, which can give full play to the advantages of both. The inverse position solution model of the mechanism is established, and the velocity Jacobian matrix and acceleration expression are derived to obtain the velocity and acceleration variation laws of the me-chanism. On this basis, the factors affecting the workspace are analyzed, and the workspace atlas under different orientation angles is obtained. The results provide theoretical model for the realization planning trajectory of (5-SPS)+5R2U HRDM.

Redundant Serial Manipulator Inverse Position Kinematics and Dynamics

AbstractA redundant serial manipulator inverse position kinematic mapping is employed to define a new manipulator operational space differentiable manifold and an associated system of well posed operational space differential equations of manipulator dynamics. A review of deficiencies in the conventional generalized inverse velocity approach to manipulator redundancy resolution and a numerical example show that the conventional approach is incompatible with kinematics of redundant serial manipulators. The inverse position kinematic mapping presented is shown to define a differentiable manifold that is parameterized by either input or operational space coordinates. Differentiation of the inverse position mapping yields an inverse velocity mapping that is a total differential, in contrast with generalized inverse velocity mappings, hence avoiding the deficiencies identified. A second differentiation yields an inverse acceleration mapping that is used, without ad-hoc derivation, to obtain well posed operational space ordinary differential equations of redundant manipulator dynamics that are equivalent to the equations of multibody dynamics.

Regional GPS orbit determination using code-based pseudorange measurement with residual correction model

Abstract The study introduces the concept of regional GPS orbit determination, whereby GPS satellite positions are determined using GPS measurements from locally or regional distributed stations. The importance and characteristics of regional GPS orbit are briefly discussed. The technique used to determine the regional GPS satellite position is coined Inverse Single Point Positioning (ISPP). Code-based pseudorange is used and improved using residual correction model. Two designs of station distribution are selected in this study, which only cover stations in Malaysia and stations situated 8000 km from a reference point in Malaysia. The root-mean-squared-error (RMSE) of ISPP when compared against final ephemeris were 660.65 m and 27.61 m, while the 3D RMSE of positioning were 1.612 m and 1.324 m for the first and second designs, respectively, lower than the accuracy of broadcast ephemeris. Three parameters are identified as factors affecting accuracy of ISPP, namely geometry of station distribution, nature of measurement used, and technique of orbit determination. Further research will be required to fully realize a functional regional GPS orbit.

Analysis of quantum systems subject to inverse trigonometry Scarf plus Coulomb potential in N-dimensions

We present approximate solutions of the N-dimensional Klein–Gordon equation in the presence of a superposition of inverse trigonometry Scarf potential and Coulomb potential through asymptotic iteration approach. With the purpose of dealing with the -state, we use Greene-Aldrich approximation which is valid for the small values of the screening parameter. The analytical expressions for the relativistic energy eigenvalues and the corresponding eigenfunctions are established in hyperspherical coordinates. The normalized hyper-radial wavefunction is expressed in terms of hypergeometric and Jacobi polynomials. We analyze the dependences of the relativistic energy levels on the dimensions. We also discuss the effect of the screening parameter on the relativistic energy spectrum. The expectation values of inverse position the square of inverse position kinetic energy and square of momentum in N-dimensional space are reported using the Hellmann-Feynmann theorem. Discussing the special cases of the relevant potential, we show the accuracy of our results.

Workspace, Singularity, and Dexterity Analyses of a Six-Degrees-of-Freedom SDelta Robot With an Orthogonal Base Platform

Abstract The SDelta is a three-limb, six-degrees-of-freedom parallel kinematics machine, a pertinent candidate for high-speed operations by virtue of its simple architecture. The original design of the SDelta includes a planar base and moving platforms. Here, we propose a novel architecture for an improved SDelta, the orthogonal SDelta (OSD), with a cube-shaped orthogonal base platform. Inverse and forward position models are reported, along with singularity and dexterity analyses. Moreover, design parameters and mechanical constraints leading to a singularity-free workspace are provided. An evaluation of the system translational workspace and orientational capability, upon consideration of volume and dexterity, is included. The SDelta as well as a generic 6SPS mechanism (C, P, and S denote, respectively, the cylindrical, prismatic, and spherical kinematic pairs, the actuated pair is represented underlined, as P) are designed with the same parameters, then the performance of the SDelta, the OSD, and the 6SPS mechanisms are being compared. The results show that the orientational capability of the OSD is better than those of the 6SPS and the SDelta. Furthermore, the OSD has an average condition number of 2.9 over its translational workspace and 1.69 over a predefined effective regular workspace, which make the OSD a good candidate for operations that need both a high orientational capability and high dexterity.

Direct control of the endpoint of the manipulator under non-smooth uncertainty and reference trajectories

The problem of tracking the reference trajectory for the manipulator endpoint is considered under the following assumptions: the matrices of the mechanical system have uncertain parameters; external non-smooth disturbances act on the system; and only the vector of generalized coordinates of the manipulator is measured. This vector is uniquely recalculated into the vector of positions of the endpoint. A direct method for the synthesis of a tracking system is proposed, which does not require solving the inverse position problem. The manipulator model is represented in the canonical input-output form considering the vector of the endpoint. The input is a vector of generalized moments developed by the actuators. The complexity of regulation consists of the uncertainty of the input matrix. To stabilize tracking errors under these conditions, a method of linearization by dynamic feedback has been developed. For estimating mixed variables and disturbances, an observer of the minimum possible dynamic order is proposed. A cascade procedure for tuning S-shaped smooth and nonlinear (sigmoid) corrective actions of the observer is presented. This procedure provides an estimation of non-smooth disturbances in a given time with a given accuracy. To smooth primitive trajectories that define, as a first approximation, the desired movement of the endpoint in the workspace, tracking differentiators with sigmoid local feedbacks are used. To tune a tracking differentiator of arbitrary dimension, a decomposition procedure is developed. This procedure considers physical constraints on the velocity and higher derivatives of the manipulator endpoint. The variables of such a differentiator generate smoothed trajectories and their derivatives of any desired order. These trajectories become achievable for the robot. They are used in the tracking system of the control plant as new reference trajectories. The simulation results for a 3-link manipulator demonstrate the excellent performance of the proposed algorithms.

경주지역 신라사찰 출토 매납토기의 용도와 특징

This study investigated the usages, characteristics, and chronological records by categorizing the earthenware buried in fixed or inverse positions as a unit-structured relic in the major temples of the Silla era, which are located in the capital area of Silla within Gyeongju, such as Hwangnyongsa Temple Site, Bunhwangsa Temple, Jeoninyongsa Temple Site, Cheongwansa Temple Site, and Changnimsa Temple Site. It was confirmed that most temples of the Silla era included a large gourd-shaped building assembly site (大壺群集建物址). The large gourd-shaped building assembly sites were typically located in the surroundings of the northeast areas, especially the northern part of the central temple site. This locational pattern also appeared at the temples in the Baekje area and the royal capital area of Japan during the same period, and certain norms must have been applied to the space layout of the building during the construction of temples. This study, in particular, identified that the usage of large kettle-shaped building assembly sites was a conventional warehouse or a storage facility, but it also raised a possibility of a brewing facility. The items suppressing the bad energies of the ground buried in the temples of the Silla era were typically connected to the stylobates or cornerstones of a specific building and were often positioned around a pagoda or special building sites, exhibiting in a certain direction. Such a burial activity was perceived as an intentional and ceremonial event, and was understood to be stemmed from traditional religious rituals or religious aspirations toward specific objects. There are some potteries that exhibit the characteristics of an item containing human bones among the buried potteries classified into the conventional items suppressing the bad energies of the ground in the surrounding temple sites away from the Buddist service area which is the center of a temple. In the future, the analysis on the natural scientific contents of the buried earthenware is further required in surveys of temples and real-life historical remains.

Retrospective evaluation of traction time for impacted dilacerated maxillary central incisors in mixed dentition

PurposesThis study aimed to contribute to understanding the factors affecting the time of traction treatment of impacted dilacerated maxillary central incisors. MethodsThis retrospective study included children aged 8 – 11 years with a history of trauma, who applied to the pediatric dentistry clinics of Marmara University, School of Dentistry, between December 2013 and December 2019, and were treated for unilateral impacted dilacerated maxillary upper central incisors. Children's age, sex, digital panoramic radiographs, cone-beam computed tomography, and intraoral photographs were retrieved from electronic dental health records. The effects of children's age, sex, the direction of impacted teeth, distance of the teeth to the top of the alveolar crest, and root dilaceration level on traction time were analyzed by Mann-Whitney U test and Spearman's rank correlation coefficient test. ResultsThe inverse position of the incisors significantly increased the traction time (P = 0.012). However, the traction time did not differ according to the sex of the children (P = 0.707) or the level of root dilaceration (P = 0.429). No correlation was observed between the traction time and the age of children (P = 0.644) or the distance of the incisors from the top of the alveolar crest (P = 0.397). ConclusionsIn cases of the forced eruption of for the impacted dilacerated maxillary central incisors, the direction of the teeth should be evaluated when deciding on the treatment plan, as it may affect the treatment time.

Three 2-DOF 1T1R and One 3-DOF 2T1R Full-Hinged Novel Parallel Mechanisms With Zero Coupling Degree and Motion Decoupling: Design and Analysis

AbstractThis paper presents the design and analysis of a family of full-hinged partially-decoupled novel parallel mechanisms (PMs) featuring one/two translation(s) and one rotation (1T1R/2T1R). First, three 2DOF 1T1R and one 3DOF 2T1R novel spatial PMs are proposed, according to topology design theory of PM based on position and orientation characteristic (POC) equations. The 3DOF 2T1R PM is illustrated to show its topological characteristics, such as POC set, degrees-of-freedom (DOF), and coupling degree (k), which show that the PM does not produce parasitic motion, with the coupling degree k being equal to zero. Second, the kinematic and dynamic performances of the 3DOF 2T1R PM are analyzed, including symbolic forward position solutions based on its topological characteristics, the workspace based on both the forward and inverse position solutions, respectively, the singular configurations based on the inverse position solutions, and the dynamic analysis built by means of the virtual work principle based on the single-open-chain units. Finally, the potential application of the proposed 3DOF 2T1R PM, namely, lifting and transferring lightweight workpieces between two perpendicular conveyor belts on the floor, is introduced.

KARAKTERISTIK PEMANEN DAYA LISTRIK BERBASIS GETARAN STRUKTUR

Mechanical vibration is a potential source of micro-electrical energy harvesting mechanisms for micro electrical power supply for IoT system networks, wireless and sensors where the power requirements are relatively lower and available independently. In this study, the characteristics of the cylinder vibration response as a trigger for energy harvesting from flow-induced vibrations at various air velocities were investigated experimentally in a wind tunnel test section. Harvesting of micro power from cylinder’s motion by using galfenol (Fe-Ga) material was also investigated simultaneously. The maximum cylinder’s vibration response was obtained by using the plain cylinder model. Cylinder taper variation reduce the maximum vibration response. The position of the major (D) and minor (d) (or inverse position) diameters also affects the vibration response. However, tapering the cylinder reduces the onset vibration with respect to the flow velocity. The frequency of the vortex (Strouhal, St) ranges from 0.25 to 0.12. The minor diameter of the tapered cylinder has the effect on decreasing the vibration response and tends to be stationary. Minor diameter reduction reduces the potential for vibration to the structure. The maximum power generated by the test model is about 8.5 mW with the power RMS value of 2.3 mW and power coefficient about 4%.

Design and kinematic performance analysis of a ship shell plate spraying manipulator

In order to solve the problems of low efficiency and pollution of the existing artificial ship outer plate spraying, a parallel spraying manipulator for ship outer plate is presented and analyzed. The structure analysis of the 3-DOF (degree of freedom) spraying manipulator is carried out using screw theory, and the mechanism diagram and virtual prototype are given. The position of the spraying manipulator is studied, and the expressions of the inverse position solution and the forward position solution are obtained. The Jacobian matrix is developed velocity analysis, and three singular configurations of the spraying manipulator are analyzed. The rotation ability of the gun of the spraying manipulator is described and the reachable workspace is drawn. Results show that the proposed manipulator can accomplish more flexible output trajectories than traditional spraying operations, which has higher spraying efficiency and can save more labor.

Inversion position testing in concussed athletes

Context No prior study has examined inversion position testing in individuals who have experienced sports related concussions. Objective To investigate whether the inversion position testing (IPT) would un-mask symptoms in asymptomatic concussed collegiate athletes during the return to play progression assessment. Design Case-Control Study. Setting Athletic Training Room. Participants One hundred and thirty-nine collegiate student athletes were randomly recruited from 12 different sports belonging to National Collegiate Athletic Association Division I Conference. Main outcome measure(s) A baseline concussion symptom questionnaire was administered. Of the 139, 122 participants without any of the suspicious symptoms related to concussions were examined using the Concussion Symptom Inventory (CSI) in connection with IPT. Also, the 18 concussed athletes underwent the IPT when any symptom subsided. Results Eighteen of the 122 (16.2%) non-concussed athletes showed some post-IPT symptoms, while 5 of 12 (41.7%) concussed athletes showed some post-IPT symptoms in the baseline test. For the latter, neither the interaction ( P = 0.08) nor difference in the total CSI score was observed either from pre- to post-IPT ( P = 0.14) or between the baseline and post-concussion ( P = 0.96). Conclusion This study demonstrated that symptoms could be exacerbated by the IPT in concussed athletes even when their original symptoms had subsided prior to the testing. The IPT exacerbated post-concussive symptoms may depend on a number of days required for post-concussive symptoms to subside. The innovative instrument of IPT may prove effective in clarifying the degree to which post-concussive symptoms have subsided. Key words Concussion, College athletes, Inversion position, Symptoms.

The Good, the Bad, and the Ugly

Abstract In recent years, a number of philosophers have suggested that the aesthetic value sometimes depends on moral value. In this paper, I motivate and defend the inverse position: the view that aesthetic value sometimes partially grounds moral value. I appeal to Grand Budapest Hotel and The Lovely Bones to show that maudlin treatments of morally serious subject matter are sometimes disrespectful, in part because they are maudlin; I appeal to Madame Bovary to show that lyrical treatments of morally serious subject matter are compassionate, in part because they are lyrical. I go on to clarify that aesthetic value and descriptive facts about the subject matter of an artwork jointly ground its moral value, and I conclude by considering and rejecting a number of potential objections to the aestheticist thesis.