Search results
1 – 10 of over 29000Alice Bennett and Darren Johnson
In light of the clinical importance of understanding co-morbidity within offender populations, the purpose of this paper is to examine the prevalence and comorbidities of clinical…
Abstract
Purpose
In light of the clinical importance of understanding co-morbidity within offender populations, the purpose of this paper is to examine the prevalence and comorbidities of clinical disorder (Axis I) and personality disorder (Axis II) within a sample of high risk, male offenders located in a high secure, prison-based personality disorder treatment service.
Design/methodology/approach
The study utilised clinical assessment data for both Axis I diagnoses (Structured Clinical Interview for DSM-IV) and Axis II diagnoses (International Personality Disorder Examination) of 115 personality disordered offenders who met the criteria for the treatment service between 2004 and 2015.
Findings
Co-morbidity between Axis I and Axis II diagnoses was high, with 81 per cent of the sample having co-morbid personality disorder and clinical disorder diagnosis. The most prevalent Axis I disorder was substance misuse, and Axis II was antisocial, borderline, and paranoid personality disorder. Following χ2 analysis, Cluster A personality disorder demonstrated co-morbidity with both mood disorder and schizophrenia/other psychotic disorder. Paranoid, schizoid, narcissistic, and avoidant personality disorder demonstrated a level of co-morbidity with Axis I disorders. There was no association found between the clinical disorders of substance use and anxiety with any personality disorder within this sample.
Practical implications
In part these results suggest that certain Axis II disorders may increase the risk of lifetime Axis I disorders.
Originality/value
The findings of no co-morbidity between the clinical disorders of substance use and anxiety with any personality disorder within sample are inconsistent to previous findings.
Details
Keywords
Jieyu Zhang, Yuanying Qiu, Xuechao Duan and Changqi Yang
Cylindrical components are common in industry assembly areas. It is necessary to obtain their precise positions and orientations for their assemblies. But some measurement…
Abstract
Purpose
Cylindrical components are common in industry assembly areas. It is necessary to obtain their precise positions and orientations for their assemblies. But some measurement approaches relying on measuring targets are not allowed, as they may not meet the efficiency requirement of on-line measurement or may cause surface damages to the components. Thus, this paper aims to provide a precise on-line non-target scanning method based on 3D vision.
Design/methodology/approach
First, a laser profile sensor is used to acquire point cloud of the side surface of the measured cylindrical component. Then a composite process is conducted to estimate the pose and position of the axis. Aiming at this purpose, two fitting approaches, i.e., axis fitting and generatrix fitting, are tried respectively to estimate the pose parameters from the point cloud.
Findings
The results of Monte Carlo simulations demonstrate that neither the axis fitting nor the generatrix fitting could solely obtain the needed accuracy and precisions roundly. Thus, a new synthesis method is presented. And the results of prototype experiments validate the excellent accuracy and precision of the synthesis method.
Originality/value
This proposed new synthesis method combines the advantages of both the above fitting methods and can be easily integrated into the assembly line to guide the automation assembly process of the cylindrical components precisely.
Details
Keywords
Wenmin Chu, Xiang Huang and Shuanggao Li
With the improvement of modern aircraft requirements for safety, long life and economy, higher quality aircraft assembly is needed. However, due to the manufacturing and assembly…
Abstract
Purpose
With the improvement of modern aircraft requirements for safety, long life and economy, higher quality aircraft assembly is needed. However, due to the manufacturing and assembly errors of the posture adjustment mechanism (PAM) used in the digital assembly of aircraft large component (ALC), the posture alignment accuracy of ALC is difficult to be guaranteed, and the posture adjustment stress is easy to be generated. Aiming at these problems, this paper aims to propose a calibration method of redundant actuated parallel mechanism (RAPM) for posture adjustment.
Design/methodology/approach
First, the kinematics model of the PAM is established, and the influence of the coupling relationship between the axes of the numerical control locators (NCL) is analyzed. Second, the calibration method based on force closed-loop feedback is used to calibrate each branch chain (BC) of the PAM, and the solution of kinematic parameters is optimized by Random Sample Consensus (RANSAC). Third, the uncertainty of kinematic calibration is analyzed by Monte Carlo method. Finally, a simulated posture adjustment system was built to calibrate the kinematics parameters of PAM, and the posture adjustment experiment was carried out according to the calibration results.
Findings
The experiment results show that the proposed calibration method can significantly improve the posture adjustment accuracy and greatly reduce the posture adjustment stress.
Originality/value
In this paper, a calibration method based on force feedback is proposed to avoid the deformation of NCL and bracket caused by redundant driving during the calibration process, and RANSAC method is used to reduce the influence of large random error on the calibration accuracy.
Details
Keywords
Sajan Kapil, Prathamesh Joshi, Pravin Milind Kulkarni, Seema Negi, Ranjeet Kumar and K.P. Karunakaran
The support structures of sacrificial material are built in deposition-based additive manufacturing (AM), which are later removed either by breaking or dissolving. Such a…
Abstract
Purpose
The support structures of sacrificial material are built in deposition-based additive manufacturing (AM), which are later removed either by breaking or dissolving. Such a sacrificial material is not feasible in metal AM. The purpose of this study is to find a suitable method for eliminating the need of support mechanism. In this work, the authors use the tilting of the substrate to alleviate the need for the support mechanism altogether.
Design/methodology/approach
As in the traditional AM, the object is grown in horizontal layers. However, wherever undercuts are encountered, the substrate is tilted appropriately to capture the droplets. Such a tilt involves two rotary axes invariably. To conform to the slice geometry, these two tilts are accompanied by the three linear movements. Thus, the object with undercuts is grown in planar layers using five-axis deposition without any support structure. Each pair of the corresponding top and bottom contours of any slice defines a ruled surface. The axis of the deposition head will be aligned with the rules of this surface.
Findings
The need for the support mechanism was eliminated using five-axis deposition. This was experimentally demonstrated by building an aluminum impeller using a metal inert gas cladding head.
Research limitations/implications
In the proposed methodology, the objects with an abrupt change in the geometry are not possible to realize.
Originality/value
This manuscript proposed a novel method of eliminating the support mechanism through continuous five-axis deposition.
Details
Keywords
Enes Mahmut Göker, Ahmet Fevzi Bozkurt and Kadir Erkan
The purpose of this paper is to introduce a novel cross (+) type yoke with hybrid electromagnets and new reluctance modeling to precisely calculate attraction force is given.
Abstract
Purpose
The purpose of this paper is to introduce a novel cross (+) type yoke with hybrid electromagnets and new reluctance modeling to precisely calculate attraction force is given.
Design/methodology/approach
The comparison of attraction force and torque analyses between the proposed formulation and the existing formulation in the literature is comparatively presented. For the correctness of the force and torque values calculated in the model created, the system was created in ANSYS Maxwell and its accuracy was proved by making analyses. The maglev carrier system is inherently unstable from the point of view of control engineering. For that, it needs an active controller to eliminate this instability. For the levitation of the carrier system, it is necessary to design a controller in three axes (z, α and β). I-PD controller was designed for the air gap control of the carrier system in three axes and the controller parameters were determined by the canonical method.
Findings
While the new formulation proposed in the modeling of the carrier system has a maximum error of 1.03%, the existing formula in the literature has an error of 16.83% in the levitation distance point.
Originality/value
A novel cross-type hybrid carrier system has been proposed in the literature. With the double integral used in modeling the system, it takes a long time to solve symbolically, and it is difficult to simulate dynamic behavior in control validation. To solve this problem, attraction force and inclination torque values are easily characterized by new formulation and besides the simulations are conducted easily. The experimental setup was manufactured and assembled, and the carrier system was successfully levitated, and reference tracking was performed without overshoot.
Details
Keywords
Qiang Fang, Weidong Chen, Anan Zhao, Changxi Deng and Shaohua Fei
In aircraft wing–fuselage assembly, the distributed multi-point support layout of positioners causes fuselage to deform under gravity load, leading to assembly difficulty and…
Abstract
Purpose
In aircraft wing–fuselage assembly, the distributed multi-point support layout of positioners causes fuselage to deform under gravity load, leading to assembly difficulty and assembly stress. This paper aims to propose a hybrid force position control method to balance aerodynamic shape accuracy and deformation of assembly area, thereby correcting assembly deformation and reducing assembly stress.
Design/methodology/approach
Force and position control axes of positioners are selected based on screw theory and ellipsoid method. The position-control axes follow the posture trajectory to align the fuselage posture. To exert force on the fuselage and correct the deformations, the force-control axes follow the contact force derived by using orthogonal experiments and partial least squares regression (PLSR). Finite element simulation and one-dimension deformation correction experiment are conducted to verify the validity of this method.
Findings
Simulation results indicate that hybrid force position control method can correct assembly deformation and improve the wing–fuselage assembly quality significantly. Experiment on specimen verifies the effect of this method indirectly.
Originality/value
The proposed method gives a solution to solve the deformation problem during aircraft wing-fuselage assembly, thereby reducing assembly stress and improving assembly quality.
Details
Keywords
Xishuang Jing, Duanping Lv, Fubao Xie, Chengyang Zhang, Siyu Chen and Ben Mou
3D printing technology has the characteristics of fast forming and low cost and can manufacture parts with complex structures. At present, it has been widely used in various…
Abstract
Purpose
3D printing technology has the characteristics of fast forming and low cost and can manufacture parts with complex structures. At present, it has been widely used in various manufacturing fields. However, traditional 3-axis printing has limitations of the support structure and step effect due to its low degree of freedom. The purpose of this paper is to propose a robotic 3D printing system that can realize support-free printing of parts with complex structures.
Design/methodology/approach
A robotic 3D printing system consisting of a 6-degrees of freedom robotic manipulator with a material extrusion system is proposed for multi-axis additive manufacturing applications. And the authors propose an approximation method for the extrusion value E based on the accumulated arc length of the already printed points, which is used to realize the synchronous movement between multiple systems. Compared with the traditional 3-axis printing system, the proposed robotic 3D printing system can provide greater flexibility when printing complex structures and even realize curved layer printing.
Findings
Two printing experiments show that compared with traditional 3D printing, a multi-axis 3D printing system saves 47% and 79% of materials, respectively, and the mechanical properties of curved layer printing using a multi-axis 3D printing system are also better than that of 3-axis printing.
Originality/value
This paper shows a simple and effective method to realize the synchronous movement between multiple systems so as to develop a robotic 3D printing system that can realize support-free printing and verifies the feasibility of the system through experiments.
Details
Keywords
Fayong Guo, Hao Cai, Marco Ceccarelli, Tao Li and Butang Yao
Robot kinematic modeling needs to be based on clear physical concepts. The widely used Denavit–Hartenberg (D–H) convention requires the coordinate system to be established on an…
Abstract
Purpose
Robot kinematic modeling needs to be based on clear physical concepts. The widely used Denavit–Hartenberg (D–H) convention requires the coordinate system to be established on an extension of the axis. This leads to non-trivial problems which this study seeks to address by developing an improved convention.
Design/methodology/approach
First, the problems associated with the traditional D–H convention are systematically analyzed. Then, pursuant of solving these problems, an enhanced Denavit–Hartenberg (ED–H) convention is proposed, and a procedure is delineated for establishing the coordinate frame and obtaining the associated parameters. The transformation equations are derived based on a homogeneous matrix. The characteristics of traditional D–H and ED–H with regard to kinematics and dynamics are comprehensively compared. Finally, an application of dynamics for lead-through programming and collision protection is undertaken to validate the proposed ED–H method. Simulations and experiments are carried out using the Tiansui-One cooperative robot platform with the aim of exploring the merits of the proposed convention.
Findings
The proposed convention is compatible with traditional methods and can solve the problems inherent in these methods. The main characteristic of ED–H is that the coordinate system is fixed on the joint, which is a general modeling method.
Originality/value
An enhanced D–H convention is proposed to establish a unified, intuitive and accurate link model that exhibits stronger adaptability than traditional D–H and can be used effectively in kinematic and dynamic modeling of mechanical arms.
Details
Keywords
Tao Zhang, Yuntao Song, Huapeng Wu and Qi Wang
Every geometric model corresponding to a unique feature whose errors of parameters uncorrelated, so the linearization technique can be successfully applied. The solution of a…
Abstract
Purpose
Every geometric model corresponding to a unique feature whose errors of parameters uncorrelated, so the linearization technique can be successfully applied. The solution of a linear least square problem can be applied straightforwardly. This method has advantages especially in calibrate the redundant robot because it’s relatively small. The parameters of kinematics are unique and determined by this algorithm.
Design/methodology/approach
In this paper, a geometric identification method has been studied to estimate the parameters in the Denavit–Hartenberg (DH) model of the robot. Through studying the robot’s geometric features, specific trajectories are designed for calibrating the DH parameters. On the basis of these geometric features, several fitting methods have been deduced so that the important geometric parameters of robots, such as the actual rotation centers and rotate axes, can be found.
Findings
By measuring the corresponding motion trajectory at the end-effector, the trajectory feature can be identified by using curve fitting methods, and the trajectory feature will reflect back to the actual value of the DH parameters.
Originality/value
This method is especially suitable for rigid serial-link robots especially for redundant robots because of its specific calibration trajectory and geometric features. Besides, this method uses geometric features to calibrate the robot which is relatively small especially for the redundant robot comparing to the numerical algorithm.
Details
Keywords
The purpose of the present work is to develop a unified mathematical theory of the steady and disturbed motion of a helicopter with particular emphasis on the dynamical aspects of…
Abstract
The purpose of the present work is to develop a unified mathematical theory of the steady and disturbed motion of a helicopter with particular emphasis on the dynamical aspects of the problem. The helicopter is assumed to undergo arbitrary small disturbances in velocity and angular velocity from a steady rectilinear flight condition, and the rotor forces are calculated as generalized functions of the initial and disturbed velocities. A high degree of accuracy is maintained both in the retention, where necessary, of products of small quantities and in the retention of high powers of µ in the solution of the trim equations. The steady motion of the helicopter is discussed at length as a preliminary to a study of its dynamic stability. Part I deals with the general features underlying helicopter motion. The importance is emphasized of a three‐dimensional approach to the problem, and it is shown that a complete description of steady rectilinear motion demands the use of fifteen equations in eighteen parameters, the solution of which presents no real difficulty. A start is made on the analysis of rotor blade motion, and the geometrical aspects are discussed by means of a system of rotating vectors.