S.H. Jalali‐Naini and S.H. Pourtakdoust
The purpose of this paper is to develop a novel solution for the predicted error and introduces a systematic method to develop optimal and explicit guidance strategies for…
Abstract
Purpose
The purpose of this paper is to develop a novel solution for the predicted error and introduces a systematic method to develop optimal and explicit guidance strategies for different missions.
Design/methodology/approach
The predicted error is derived from its basic definition through analytical dynamics. The relations are developed for two classes of systems. First, for systems in which the acceleration commands are truncated at a specified time. Second, for systems in which the corrective maneuvers are cut off at a specified time. The predicted error differential equation is obtained in a way that allows for derivation of several optimal and explicit guidance schemes.
Findings
The effect of tangential acceleration in conjunction with autopilot dynamics can be realized in guidance gain and the predicted error. The differential equation of velocity‐to‐be‐gained is obtained assuming the gravitational acceleration to be given as a vectorial function of time. The relations for different velocity profiles are obtained and discussed including the effective navigation ratio.
Research limitations/implications
The guidance/control system is modeled as a linear time‐varying dynamic and of arbitrary‐order. The gravitational acceleration is assumed as a given vectorial function of time.
Practical implications
The presented schemes are applicable to both midcourse and terminal guidance laws with/without velocity constraints.
Originality/value
Providing a new analytical solution of predicted errors with final position and velocity constraints and their differential equations considering the thrust/drag acceleration and autopilot dynamics in the presence of gravity.
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Hadi Nobahari, Aria Alasty and Seid H. Pourtakdoust
The purpose of this paper is to propose a supervisory command‐to‐line‐of‐sight guidance law with lead angle which keeps the missile flight within the tracking beam.
Abstract
Purpose
The purpose of this paper is to propose a supervisory command‐to‐line‐of‐sight guidance law with lead angle which keeps the missile flight within the tracking beam.
Design/methodology/approach
A nonlinear supervisory controller is designed and coupled with the main sliding mode controller in the form of an additional control signal. The supervisory control signal is activated when the beam angle constraint goes to be violated. Initially a supervisory controller is designed using nonlinear control theory. Subsequently the main tracking controller is designed using sliding mode approach which forces the missile to fly along the desired line‐of‐sight. The stability of the supervisory controller coupled with the main controller is proved in the Lyapunov sense.
Findings
There exists a major drawback with the lead angle method of guidance, which is a high probability of flying out of the beam. The proposed supervisory controller has successfully overcome this deficiency. Thus, a better performance has been achieved.
Practical implications
The proposed guidance scheme can be applied to tactical surface to air missiles. Additionally the idea of supervisory controller can be applied to any similar control problem where there are some constrains over the states of the system.
Originality/value
The idea of supervisory controller has not been applied to the problem of command‐to‐line‐of‐sight guidance law. This paper utilizes and extends the idea of supervisory controller design to cases when a special state is to be supervised while considering the effect of external disturbances.
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Mohd Badrul Salleh, Nurulasikin Mohd Suhadis and Renuganth Varatharajoo
This paper aims to investigate the attitude control pointing improvement for a small satellite with control moment gyroscopes (CMGs) using the active force control (AFC) method.
Abstract
Purpose
This paper aims to investigate the attitude control pointing improvement for a small satellite with control moment gyroscopes (CMGs) using the active force control (AFC) method.
Design/methodology/approach
The AFC method is developed with its governing equations and integrated into the conventional proportional-derivative (PD) controller of a closed-loop satellite attitude control system. Two numerical simulations of an identical attitude control mission namely the PD controller and the PD+AFC controller were carried out using the MATLAB®-SimulinkTM software and their attitude control performances were demonstrated accordingly.
Findings
Having the PD+AFC controller, the attitude maneuver can be completed within the desired slew rate, which is about 2.14 degree/s and the attitude pointing accuracies for the roll, pitch and yaw angles have improved significantly by more than 85% in comparison with the PD controller alone. Moreover, the implementation of the AFC into the conventional PD controller does not cause significant difference on the physical structure of the four single gimbal CMGs (4-SGCMGs).
Practical implications
To achieve a precise attitude pointing mission, the AFC method can be applied directly to the existing conventional PD attitude control system of a CMG-based satellite. In this case, the AFC is indeed the backbone for the satellite attitude performance improvement.
Originality/value
The present study demonstrates that the attitude pointing of a small satellite with CMGs is improved through the implementation of the AFC scheme into the PD controller.
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Giuseppina Autiero and Concetto Paolo Vinci
The purpose of this paper is to analyze the causal link between government regulation of religion and the choice of investing in human and physical capital.
Abstract
Purpose
The purpose of this paper is to analyze the causal link between government regulation of religion and the choice of investing in human and physical capital.
Design/methodology/approach
The paper uses an analytical model with a government setting the output quota to transfer to religious activities. This depends on the extent to which it is an ideological government that uses religion either for legitimacy aims or for the ideological control of population. Workers and entrepreneurs observe the quota and simultaneously choose the investment in human and physical capital, which may trigger, à la Acemoglu, social increasing returns.
Findings
Directing resources to religious activities may be detrimental to output performance. This may occur if an ideological government sets the optimal quota above the quotas preferred by private agents. This negatively affects the investment in physical and human capital and output performance.
Originality/value
Despite the importance of government regulation of religion in the literature, its effect on output performance has not been thoroughly analyzed yet. In this respect, the paper aims to further investigate the causal links between religion regulation related to government type and the investments in human and physical capital and the output level.
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Saurabh Agrawal, Rajesh K. Singh and Qasim Murtaza
The purpose of this paper is to explore the various disposition alternatives and to develop a framework for the optimal disposition decisions in reverse logistics.
Abstract
Purpose
The purpose of this paper is to explore the various disposition alternatives and to develop a framework for the optimal disposition decisions in reverse logistics.
Design/methodology/approach
In reverse logistics, once the products are collected and inspected, decision is to be taken regarding their disposition for reuse, re-manufacture or recycle or other possible alternatives. A combination of analytical hierarchy process (AHP) and fuzzy technique for order preference by similarity to ideal solution (TOPSIS) approach is proposed for the selection of best disposition alternative based on criteria economic benefits, environmental benefits, corporate social responsibility, stakeholder’s needs and reverse logistics resources.
Findings
A case of electronics firm was illustrated for the demonstration of the approach for the disposition of mobile phones. Returned mobile phones must be disposed for repairing or reuse in current business scenario, if possible. Otherwise, the firm may prefer to recycle them rather than dispose or remanufacture.
Research limitations/implications
The study is limited to mobile manufacturing firm. Also, these findings may vary depending on the sector and products. Further, empirical studies and case studies can be carried out to validate the findings.
Practical implications
The proposed framework provides useful tool to the practitioners and researchers in decision-making for disposition in reverse logistics.
Originality/value
Very few studies related to disposition decisions in reverse logistics were found in the previous research literature review. The study will add value to the very limited research on reverse logistics disposition. Also, the AHP-Fuzzy TOPSIS approach is first time being used for the disposition decisions in reverse logistics.
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Intangible resources are the most distinctive firms’ assets in competitive environments especially in service businesses. Insurance firms seeking more efficient performance than…
Abstract
Purpose
Intangible resources are the most distinctive firms’ assets in competitive environments especially in service businesses. Insurance firms seeking more efficient performance than competitors should improve their intellectual capital (IC) strategies in both aspects of IC creation and utilization. The purpose of this paper is to investigate and improves IC participation in insurance firms’ efficiency.
Design/methodology/approach
A two-phase framework: “explaining IC role in efficiency” and “measuring efficiencies of IC creation and application” is developed in order to find IC strategies increasing firms’ efficiency and though competitiveness. Efficiency is measured using data envelopment analysis and the generalized estimating equations is used as the regression method in order to explain efficiency with IC measures.
Findings
Empirical results in Iran insurance sector (during a seven-year period for 17 Iranian insurers) show some IC components influence firms’ efficiency and could be intervention points for performance improvement. Then the firms are categorized into four zones in terms of IC efficiency and strategies are recognized for each category.
Research limitations/implications
Although the research is initiated by the need to embed intangible resources in performance improvement in insurance sector, the research framework could be strongly applied in other knowledge-based industries.
Originality/value
This paper embeds an innovative link between classic efficiency and IC which aligns resource management with competitiveness strategies.
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Abdolreza Roshani and Farnaz Ghazi Nezami
This paper aims to study a generalized type of mixed-model assembly line with multi-manned workstations where multiple workers simultaneously perform different tasks on the same…
Abstract
Purpose
This paper aims to study a generalized type of mixed-model assembly line with multi-manned workstations where multiple workers simultaneously perform different tasks on the same product. This special kind of assembly line is usually utilized to assemble different models of large products, such as buses and trucks, on the same production line.
Design/methodology/approach
To solve the mixed-model multi-manned assembly line balancing problem optimally, a new mixed-integer-programming (MIP) model is presented. The proposed MIP model is nondeterministic polynomial-time (NP)-hard, and as a result, a simulated annealing (SA) algorithm is developed to find the optimal or near-optimal solution in a small amount of computation time.
Findings
The performance of the proposed algorithm is examined for several test problems in terms of solution quality and running time. The experimental results show that the proposed algorithm has a satisfactory performance from computational time efficiency and solution accuracy.
Originality/value
This research is the very first study that minimizes the number of workers and workstations simultaneously, with a higher priority set for the number of workers, in a mixed-model multi-manned assembly line setting using a novel MIP model and an SA algorithm.