Terminal Angle Research Articles

Changes of cervical sagittal alignments during motions in patients with cervical kyphosis.

Changes of cervical sagittal alignment during motion in cervical kyphosis patients have never been published before. This study was to investigate the changes and provide a better reference for orthopedic treatment.Randomized double-blind repeat trial was carried out on 60 patients with cervical kyphosis. On standard position, hyper flexion, and hyper extension sagittal radiographs, the following measurements were made: the C2–7 vertebral body spatial alignment angle (∠A), C2–7 vertebral lower terminal lamina tilt angle (∠B), C2/3 to C6/7 segmental intervertebral space angle (∠C), the distance from the posterior edge of odontoid to C7 vertebral body (D value), and the difference of angle A, B, and C between cervical flexion and extension movement. Another 60 healthy volunteers were enrolled, of whom the cervical curve apex was determined using Borden's method to compare change and distribution characteristics to patients with cervical kyphosis and C value.In standard lateral position, ∠A was positive and increased from C2 to C7. In hyper extension position, ∠A decreased with reducing amplitude from C2 to C7 compared with the standard position, whereas in hyper flexion position, the average value of ∠A increased with decreasing amplitude from C2 to C7. ∠B followed similar change regularities as ∠A with a larger mean value. In cervical flexion and extension movement, ∠A change of upper vertebral body (∠D) was almost equal to ∠A change of lower vertebral body and ∠C change between the adjacent 2 vertebral bodies (∠E). The curve apex distribution was almost between C4 and C5 in cervical kyphosis patients. A significant difference was observed between cervical kyphosis patients and normal people in C value and D value.The correction of the cervical kyphosis can be carried out from the apex of the cervical spine that provides a solid theoretical foundation for the correction of the cervical kyphosis.

Multi-Target Motion Planning Amidst Obstacles for Autonomous Aerial and Ground Vehicles

The motion planning problem of a single autonomous vehicle having a minimum turn radius constraint, visiting an ordered sequence of targets in an environment with polygonal obstacles, is addressed. Two types of vehicles are considered: aerial/ground vehicle - described by the Dubins/Reeds-Shepp vehicle models, respectively. The problem is posed in the form of a search tree by using the obstacles’ vertices, vehicle’s initial configuration, and the set of target points as nodes. The tree’s arcs are represented by the Dubins/Reed-Shepp paths without terminal angle constraint (relaxed paths) connecting two adjacent nodes. These relaxed paths - connecting an initial configuration and a destination, are calculated using a feedback algorithm. Due to the computational complexity of the problem a genetic algorithm is proposed. Additionally, two deterministic search algorithms are presented. A quick heuristic greedy algorithm which uses the visibility graph distances for estimating the remaining vehicle path and an exhaustive algorithm which provides optimal solution trajectories. The performance of the algorithms is demonstrated and compared through sample runs and a Monte Carlo study. Results confirm that the heuristic algorithm provides relatively good solution for a small radius turn vehicle, while the genetic algorithm offers a good trade-off between computational load and performance.

Generalized optimal impact-angle-control guidance with terminal acceleration response constraint

To study the optimal impact-angle-control guidance problem with multiple terminal constraints, a generalized optimal impact-angle-control guidance law with terminal acceleration response constraint (GOIACGL-TARC) is proposed. In the deriving, a time-to-go − nth power weighted object function is adopted to derived the GOIACGL-TARC and a general expression of GOIACGL-TARC is presented. Based on the general expression of GOIACGL-TARC, three guidance laws, GOIACGL-TARC1/TACC0/TACC1 are proposed and the inheritance relationship between GOIACGL-TACC0/TACC1/TARC1 and the conventional optimal guidance law with impact angle constraint is demonstrated. Performance analysis of the proposed guidance laws shows that in the case of GOIACGL-TACC0, the terminal acceleration is not zero at n = 0 and only as n > 0, the terminal acceleration converges to zero; in the case of GOIACGL-TACC1 and GOIACGL-TARC1, GOIACGL-TARC1 can guarantee the acceleration response to reach the exactly zero value but GOIACGL-TACC1 cannot, which can only guarantee the acceleration command to reach the exactly zero value. It is pointed out that compared with the biased proportional navigation guidance law, GOIACGL-TARC1 has an outstanding guidance performance in acceleration response, miss distance, and terminal impact angle error.

Observer-Based Guidance Law With Impact Angle Constraint

Accounting for the autopilot as second-order dynamics, an observer-based guidance law with terminal impact angle constraint is designed using the dynamic surface control method. Some first-order low-pass filters are introduced into the designing process to avoid the occurrence of high-order derivatives of the line of sight (LOS) angle in the expression of the guidance law such that the guidance law can be implemented in practical applications. The proposed guidance law is effective in compensating for the second-order autopilot lag. In simulation of intercepting targets with sinusoidal acceleration, the guidance law is compared with the biased proportional navigation guidance (BPNG) law in the presence of missile autopilot lag. Simulation results show that the proposed observer-based guidance law with terminal impact angle constraint is able to guide a missile with large autopilot lag to impact a target with a desired angle and achieve a small miss distance, even if the target escapes in a great and fast maneuver.

Terminal-Lead-Angle-Constrained Generalized Explicit Guidance

Besides enhancing the warhead effectiveness, the terminal lead angle constraint ensures that the target remains within the field of view of the radio proximity fuse, which is very critical for the success of a mission. This paper presents substantial enhancement of the generalized explicit guidance to include the terminal lead angle constraint in three dimension (3-D).. With the availability of the desired total lead angle in 3-D, it computes the necessary terminal flight path and heading angles so that it not only satisfies the lead angle constraint, but also leads to the minimum among all minimum control effort solutions for various possible terminal flight path and heading angle combinations. With no lead angle constraint, it also gracefully degenerates to the standard proportional navigation guidance.

Validating the measurement system using MSA: terminal angle inspection process for mounting in hoses with application in agricultural machines

This article aims to apply the MSA (Measure Analysis System) to evaluate the measurement system of the angle in metal terminals in agricultural hoses, analyzing the operator repeatability parameters, instrument reproducibility and tolerance to detect the quantitative abnormalities existence in the manufacturing process of these parts. The measurement applied methods, protractors angle and profile projector, were compared and it was observed that the profile projector is the best method applied for process validation, as its total variation attend the set parameters according to the recommendations of the American automakers AIAG, who determines that the total variation shall be smaller than 30% to be considered acceptable.

Analysis of Interrelationships among Voluntary and Prosthetic Leg Joint Parameters Using Cyclograms.

The walking mechanism of a prosthetic leg user is a tightly coordinated movement of several joints and limb segments. The interaction among the voluntary and mechanical joints and segments requires particular biomechanical insight. This study aims to analyze the inter-relationship between amputees' voluntary and mechanical coupled leg joints variables using cyclograms. From this analysis, the critical gait parameters in each gait phase were determined and analyzed if they contribute to a better powered prosthetic knee control design. To develop the cyclogram model, 20 healthy able-bodied subjects and 25 prosthesis and orthosis users (10 transtibial amputees, 5 transfemoral amputees, and 10 different pathological profiles of orthosis users) walked at their comfortable speed in a 3D motion analysis lab setting. The gait parameters (i.e., angle, moment and power for the ankle, knee and hip joints) were coupled to form 36 cyclograms relationship. The model was validated by quantifying the gait disparities of all the pathological walking by analyzing each cyclograms pairs using feed-forward neural network with backpropagation. Subsequently, the cyclogram pairs that contributed to the highest gait disparity of each gait phase were manipulated by replacing it with normal values and re-analyzed. The manipulated cyclograms relationship that showed highest improvement in terms of gait disparity calculation suggested that they are the most dominant parameters in powered-knee control. In case of transfemoral amputee walking, it was identified using this approach that at each gait sub-phase, the knee variables most responsible for closest to normal walking were: knee power during loading response and mid-stance, knee moment and knee angle during terminal stance phase, knee angle and knee power during pre-swing, knee angle at initial swing, and knee power at terminal swing. No variable was dominant during mid-swing phase implying natural pendulum effect of the lower limb between the initial and terminal swing phases. The outcome of this cyclogram adoption approach proposed an insight into the method of determining the causal effect of manipulating a particular joint's mechanical properties toward the joint behavior in an amputee's gait by determining the curve closeness, C, of the modified cyclogram curve to the normal conventional curve, to enable quantitative judgment of the effect of changing a particular parameter in the prosthetic leg gait.

A nonlinear impact-angle guidance law

PurposeThe purpose of this paper is to propose a new nonlinear guidance law to satisfy terminal impact-angle constraints against a stationary target in every possible planar surface-to-surface engagement scenario. The proposed guidance scheme is developed based on the geometry of a circular arc trajectory. The proposed guidance scheme is developed based on the geometry of circular arc trajectory. This trajectory is calculated based on the terminal impact angle and target range. The efficacy of the proposed guidance scheme is demonstrated through numerical simulations. The proposed scheme is compared with existing guidance schemes and relevant analysis is provided.Design/methodology/approachThe paper develops a new nonlinear guidance law to satisfy terminal impact-angle constraints against a stationary target in every possible planar surface-to-surface engagement scenario. The proposed guidance scheme is developed based on the geometry of a circular arc trajectory. This guidance scheme is further extended to moving targets.FindingsThe proposed guidance intercepts a stationary target with a smooth lateral acceleration command, which is desirable for realistic implementation. The efficacy of the approach is demonstrated through numerical simulation. A comparative study with the existing algorithm is presented and it is shown that the proposed algorithm is better on many counts.Originality/valueThere are many approach exists in the literature for impact-angle guidance laws. The paper proposes a computationally efficient guidance law using geometric and kinematic properties. As the approach produces smooth command, it has a practical relevance. A comparative study shows superiority on some counts (miss distance, flight time, smoothness).

Fast and secure detection technique for loss of field occurrence in synchronous generators

Loss of field (LOF) phenomenon in synchronous generators may cause serious damages and voltage drop in the power system, which can result in a blackout. Conventional methods, which detect LOF on the basis of the measured impedance from terminal viewpoint, are slow and may exhibit mal-operation in the face of other phenomena, e.g. stable power swing (SPS). In this paper, a novel technique is proposed to detect LOF in synchronous generators on the basis of some electrical quantities variations including voltage of terminal (V), current (I), active power (P), reactive power (Q) and power angle (δ). To evaluate the performance of the proposed algorithm, some cases are simulated under various operation conditions. Obtained results show that this algorithm on the basis of V, Q and δ not only can be considered as a fast LOF detector in comparison with the conventional impedance-based schemes, but also it is a robust and secure technique in the face of SPS and other power system disturbances. The proposed algorithm is tested by using an experimental setup including the laboratory synchronous generators, too. The obtained results show that the proposed technique can exhibit suitable performance in the actual conditions.

Effect of seeker disturbance rejection rate on performance of optimal guidance laws with terminal impact angle constraint

In order to study the effect of seeker disturbance rejection rate on performance of optimal guidance law, based on guidance law with terminal impact angle(GLTIA) and extended guidance law with terminal impact angle(EGLIA), the regularization of strapdown seeker disturbance rejection rate on the stability of guidance system was studied. Using adjoint method the miss distance of GLTIA and EGLIA were analyzed. The results show that the stable domain of guidance system is larger when strapdown seeker parasitic loop is negative feedback than positive feedback, the stability will reduce when the value of disturbance rejection rate gets bigger. Though EGLIA has more excellent guidance performance than GLTIA, but the influence of a parasitic loop of seeker disturbance rejection rate will be more serious, the sufferable value of seeker disturbance rejection rate for EGLIA is about 2.5%, and the GLTIA is about 3.5%. In the practical application, if the guidance law would work with advanced performance, the value of seeker disturbance rejection rate should be much stricter to reduce the effect of parasitic loop.

Cadaveric study of mode of termination of gonadal veins: Implications for procedures utilizing terminal ends of gonadal veins as entry portals

Context:The terminal ends of gonadal veins act as an entry portal in gonadal embolization procedures used for treating varicocele in males and pelvic congestion disease in females. Here, we studied the modes of termination of gonadal veins in adult cadavers.Materials and Methods:Thirty-five adult formalin-fixed cadavers (seventy sides) were studied over a period of 4 years. The modes of termination of gonadal veins were observed under the following study variables: (a) number, (b) locale of termination, and (c) termination angle.Results:Variations in study parameters were observed in eight sides of seven cadavers (seven unilateral and one bilateral). Double veins at termination were observed in six cadavers; anomalous termination was observed in three cadavers. Angle of termination differed from normal in 3 cadavers. In one of these cadavers, the left ovarian vein drained into the left suprarenal vein.Conclusion:Duplication of terminal ends, anomalous drainage site, and varied angles of termination call for caution to ensure the success of procedures, which use terminal ends of gonadal veins as entry portals.

Terminal Impact Angle Constraint Guidance With Dual Sliding Surfaces and Model-Free Target Acceleration Estimator

In this paper, a new guidance law based on the variable structure system theory and an associated model-free target acceleration estimator are proposed. The composite guidance-estimation law is designed to intercept constant-velocity and maneuvering targets by missiles at a desired terminal impact angle. Specifically, the scenario of intercepting the targets with speed-disadvantaged missiles, which has not been studied in detail in the literature available, is considered in this paper. A multiple solution problem for the terminal impact angle and a final line-of-sight angle is clarified in this paper. To solve this problem, the generalized variable structure theory is used and an additional sliding mode surface is introduced in the proposed guidance law, by which missiles can reach a wider range of the final impact angle. In addition, the nonsingular terminal sliding mode control method is applied so that the states of the guidance dynamic system are finite time convergent. In order to intercept maneuvering targets, a Kriging-based model-free finite impulse response filter is employed. Based on this filter, this paper puts forward some improvements, including a data preprocessing method and a parameter offline tuning method by the simulated annealing algorithm. In this way, a model-free target acceleration estimator with strong practicality in engineering is proposed. The stability condition of the proposed composite guidance-estimation law is obtained via the Lyapunov theorem. Finally, simulation results in different initial intercepting scenarios are presented to validate the advantage of the proposed guidance law and target acceleration estimator.

Examination of the reflection properties of sloping terminations to organ pipes.

The sound characteristics of both labial and lingual organ pipes are affected to a great extent by the reflection properties of the resonators. In this paper, the reflection properties of sloped pipe terminations are examined and the possible applications in organ building practice are investigated. Sloped shallots of reed organ pipes with different termination angles are of particular interest in this study. For the examination of the reflection properties two different approaches are applied. Sound pulse reflection measurements on model geometries provide experimental data in the time domain, while finite element simulations yield reflection coefficients in the frequency domain. These two remarkably different approaches are shown to provide consistent results for all examined geometries. Laboratory measurements performed on experimental labial pipes and "Trompete" (trumpet) shallots demonstrate some of the effects of sloped terminations on the sound of organ pipes and validate the applicability of the results obtained by the model measurements and simulations.

A Differential Game Based Guidance Law for an Accelerating Exoatmospheric Missile

AbstractA differential game‐based guidance law design is proposed for a class of accelerating exoatmospheric missiles. By analyzing the nonlinear dynamic equations, a class of motions that does not require maneuver effort is derived for the missile. Using this property, a two phase guidance scheme can be derived that permits a perfect interception. In Phase 1, the missile is put in collision course with the target, which means in Phase 2 the missile should intercept the target with a straight line flight course, at a specified terminal body angle. Differential game based guidance laws are derived respectively for the two phases to guarantee the implementation of the guidance scheme. Simulation results show that the methodology provides robust interception performance.

Optimal pulsed guidance law with terminal impact angle constraint

An optimal pulsed guidance law with a time-varying weighted quadratic cost function that enables imposing a predetermined intercept angle is presented. Due to the characteristic of impulse force, admissible variance of control is redefined. The optimal pulsed guidance law is deduced via extended maximum principle. The optimal pulsed guidance law is eventually transformed to solve the two-point boundary value problem. To decide a shooting point, an efficient algorithm is proposed by combining particle swarm optimization and Kriging surrogate model method. The optimal pulsed guidance law is implemented in several representative engagements. From simulation results, it can be seen that the proposed guidance law can achieve small miss distance with terminal impact angle constraint under different conditions. Moreover, the performance of the proposed guidance law is satisfactory with the comparison of sliding-mode pulsed guidance law.

Finite time convergence cooperative guidance law based on graph theory

A new cooperative guidance law with impact time and impact angle constraints is presented for multiple flight vehicles to against the stationary target. The proposed guidance law has two projection components: the one that along the line-of-sight (LOS) ensures that all flight vehicles reach the target simultaneously with impact time constraints, another one that normal the LOS guarantees the convergence of the LOS angular rate with terminal impact angle constraints. Using the second Lyapunov stability method, we prove that the time-to-go of all flight vehicles reach at agreement in finite time if the connecting time of the communication topology is larger than the required convergent time. Nonlinear simulations demonstrate the effectiveness of the proposed law.

Fuzzy sliding mode control guidance law with terminal impact angle and acceleration constraints

In this paper, a novel fuzzy sliding mode control (FSMC) guidance law with terminal constraints of miss distance, impact angle and acceleration is presented for a constant speed missile against the stationary or slowly moving target. The proposed guidance law combines the sliding mode control algorithm with a fuzzy logic control scheme for the lag-free system and the first-order lag system. Through using Lyapunov stability theory, we prove the sliding surface converges to zero in finite time. Furthermore, considering the uncertain information and system disturbances, the guidance gains are on-line optimized by fuzzy logic technique. Numerical simulations are performed to demonstrate the performance of the FSMC guidance law and the results illustrate the validity and effectiveness of the proposed guidance law.

Sliding mode-based continuous guidance law with terminal angle constraint

ABSTRACTIn this paper, sliding mode control and disturbance observer are used to design a new continuous composite guidance law with terminal angle constraint. The robustness and finite-time convergence of the proposed guidance law is established using the Lyapunov stability theory. For performance improvement, a nonlinear disturbance observer, which can be viewed as a ‘patch’ for the original guidance law, is designed to estimate the target manoeuvre. Theoretical analysis and simulation results demonstrate the effectiveness of the proposed method.

Wettability of zirconium-coated alumina by molten aluminum

Abstract The wetting behavior and interfacial phenomena of alumina, Zr-coated alumina, and bulk Zr with liquid aluminum at 700 °C was investigated by the sessile drop technique. Zirconium film deposited on alumina improved the wettability with aluminum and promoted the formation of the precursor film. With the increase of zirconium film thickness from 160 nm to 670 nm, the terminal contact angle decreases gradually and spreading rate increased and the precursor film became wider and thicker. Marangoni flow resulting from the surface tension gradient due to the interfacial interaction is a major factor resulting in the formation of the precursor film.

Three-Dimensional Impact Angle Guidance Laws Based on Model Predictive Control and Sliding Mode Disturbance Observer

This paper presents a suboptimal three-dimensional guidance law to intercept unknown maneuvering targets with terminal angle constraint using multivariable control design. The presented guidance law is essentially a composite control method, which is constructed through a combination of standard continuous model predictive control (MPC) and adaptive multivariable sliding mode disturbance observer (SMDO). More specifically, the MPC method is utilized to obtain optimal line-of-sight (LOS) angle tracking performance for nonmaneuvering targets, while the SMDO technique is used to estimate and compensate for the unknown target maneuver online. By virtue of the adaptive nature, the proposed guidance law does not require any information on the bounds of target maneuver and its gradient except for their existence. The stability of the closed-loop guidance system is also analyzed by using Lyapunov function method. Simulation results clearly confirm the effectiveness of the proposed formulation against a maneuvering target.