System identification of a twin rotor multi-input multi-output system using adaptive filters with pseudo random binary input

This paper presents an investigation into the development of a parametric model of pitch movement of a twin rotor multi-input multi-output system (TRMS) using adaptive finite impulse response (FIR) models. The TRMS is a laboratory platform designed for control experiments. In certain aspects, its behaviour resembles that of a helicopter. It typifies a high-order nonlinear system with significant cross coupling between its two channels. The system is initially excited with PRBS signals of different bandwidths to ensure that all resonance modes are captured. The PRBS magnitude is selected so that it does not drive the system out of its linear operating range. Then, an adaptive FIR filter structure with LMS, NLMS, and genetic algorithm (GA) with LMS algorithms is investigated to identify the system and extract its parametric model. Effects of filter taps, step-size and system convergence are also studied. Performances of the employed techniques are assessed and presented in time and frequency domains

Particle swarm optimisation algorithms and their application to controller design for flexible structure systems

Particle swarm optimisation (PSO) is one of the relatively new optimisation techniques, which has become increasingly popular in tuning and designing controllers for different applications. A major problem is that simple PSO have a tendency to converge to local optima, mainly, due to lack of diversity in the particles as the algorithm proceeds and improper selection of other parameters. Maintaining diversity within a population is challenging for PSO, especially for dynamic problems. In order to increase diversity in the search space and to improve convergence, a new variant of PSO is proposed. The increased interest from industry and real-world applications has led to several modifications in the conventional algorithms so as to deal with multiple conflicting objectives and constraints. A modified multi-objective PSO (MOPSO) proposal is made which will allow the algorithm to deal with multi-objective optimisation problems. The main challenge, in designing a MOPSO algorithm, is to select local and global best for each particle so as to obtain a wide range of solutions that trade-off among the conflicting objectives. In the proposed algorithm, a new technique is introduced that combines external archive and non-dominated fronts of the current population in order to select the global best for each particle. The effectiveness of the proposed algorithm is assessed with two examples in controller design for vibration control of flexible structure systems and satisfactory results have been obtained

Hygrothermal performance of building envelopes in the tropics under operative conditions : condensation and mould growth risk appraisal

Poor indoor hygrothermal performance increases the risk of indoor moisture problems and deterioration due to mould growth, corrosion and damage to archival materials. Hence, proper control of indoor thermohygric intensity abates indoor moisture and its associated problems. This paper presents the results of envelopes hygrothermal performance assessments in a hot and humid climate building with varying operational profile between adjacent spaces. The case-studied building runs on 24hrs cooling mode in one part against natural and/or mechanical supply-exhaust fan means on the other. In-situ experiments were combined with hygrothermal analytical methods to assess the envelope thermal quality together with the operative conditions against condensation and mould growth risks. The results show that the building is overcooled leading to poor envelope hygrothermal performance with associated condensation and mould growth problems on non-airconditioned sides of the envelopes

Optimized fuzzy control for natural trajectory based FES-swinging motion

The use of electrical signals to restore the function of paralyzed muscles is called functional electrical stimulation (FES). FES is a promising ethod to restore mobility to individuals paralyzed due to spinal cord injury (SCI). A crucial issue of FES is the control of motor function by the artificial activation of paralyzed muscles due to the various characteristics of the underlying physiological/biomechanical system. Muscle response characteristics are nonlinear and time-varying. After developing a nonlinear model describing the dynamic behavior of the knee joint and muscles, a closed-loop approach of control strategy to track the reference trajectory is assessed in computer simulations. Then, the controller was validated through experimental work. In this approach only the quadriceps muscle is stimulated to perform the swinging motion by controlling the amount of stimulation pulsewidth. An approach of fuzzy trajectory tracking control of swinging motion optimized with genetic algorithm is presented. The results show the effectiveness of the approach in controlling FES-induced swinging motion in the simulation as well as in the practical environment

Socio-Demographic Characteristics Of Adults Screened For Hiv/Aids In A Rural Community In Benue State, Nigeria

Background: Benue state has been considered among the ‘hot zones’ for HIV/AIDS in Nigeria with a prevalence rate of 9.3 among adults aged 15 to 45 years. Yet, there is paucity of information on the socio-demographic factors associated with this level of prevalence. We hereby report the prevalence and socio-demographic factors associated with HIV among adults in Abwa-Mbagene, Benue state, Nigeria.Methods: Adults in Abwa-Mbagene community who accepted to participate between 9th and 24th of August 2007 were recruited. After counselling, screening was done using ‘Determine HIV’ kit.Results: 153 subjects (74 males and 79 females) were recruited. Their age ranges from 15 to 60 years (Mean: 26.2years). Fourty-two (27.5%) consisting of 12 (16.2%) males and 30 (38%) females were positive for HIV (male to female ratio, 2:5). The prevalence of HIV was higher among the divorcees (50%); those whose level of education was primary school (41.3%) and below and; farmers (60%). Majority (96%) knows AIDS exists, 85% are informed on mode and prevention of HIV transmission. Cases of AIDS deaths, unprotected casual sex, blood transfusion with unscreened blood and polygamy are common in the community. The single most important cultural factors in HIV transmission identified is indulgence in night parties, which increased the rate of unprotected casual sex.Conclusion: This community represents a high HIV/AIDS prevalence spot in Benue State, Nigeria. There is therefore the need for the establishment of HIV Counselling and Testing (HCT), Prevention of Mother-To-Child Transmission (PMTCT), save blood and antiretroviral treatment services in the community. Vocational centers to engage single women and improve their financial state will boost preventive strategies. Finally, partnership with community leaders towards discouraging night parties will reduce the prevalence of HIV in the community

Knowledge-Based Engineering in the design for manufacture of prefabricated façades: current gaps and future trends

The use of prefabricated façades provides a timely means to increase efficiency in the delivery of buildings, while maximising the expected environmental service performance. In order to achieve high performance and low cost, these products require manufacturability and supply chain knowledge to be integrated earlier than usual in the design process. Knowledge-Based Engineering (KBE) applications can potentially fulfil this need by providing a digital Product Model that informs designers about manufacturability aspects and expected performance. This paper explores the currently-available digital tools, as well as KBE and its applicability in façade design. It is first demonstrated that there is a fundamental gap in state-of-the-art digital tools: rather than integrating design principles and manufacturing constraints, existing and emerging tools continue to focus on single-disciplines with no consideration for the actual manufacturing stage. The applicability of KBE is then evaluated by reviewing the current use of this approach in the building and other industries, namely, aerospace and shipbuilding. It is found that, although KBE is rarely used in facade design, there are significant opportunities for it to be applied in this sector, due to the similarity in terms of design tasks and priorities with the two other industries reviewed in this paper.The authors would like to thank the Engineering and Physical Science Research Council (EPSRC) and Laing O’Rourke Plc for supporting the present research programme

Genetic algorithm optimization and control system design of flexible structures

This paper presents an investigation into the deployment of genetic algorithm (GA)-based controller design and optimization for vibration suppression in flexible structures. The potential of GA is explored in three case studies. In the first case study, the potential of GA is demonstrated in the development and optimization of a hybrid learning control scheme for vibration control of flexible manipulators. In the second case study, an active control mechanism for vibration suppression of flexible beam structures using GA optimization technique is proposed. The third case study presents the development of an effective adaptive command shaping control scheme for vibration control of a twin rotor system, where GA is employed to optimize the amplitudes and time locations of the impulses in the proposed control algorithm. The effectiveness of the proposed control schemes is verified in both an experimental and a simulation environment, and their performances are assessed in both the time and frequency domains

Active vibration control of a horizontal flexible plate structure using intelligent proportional–integral–derivative controller tuned by fuzzy logic and artificial bee colony algorithm

© The Author(s) 2019. This paper presents the development of an intelligent controller for vibration suppression of a horizontal flexible plate structure using hybrid Fuzzy–proportional–integral–derivative controller tuned by Ziegler–Nichols tuning rules and intelligent proportional–integral–derivative controller tuned by artificial bee colony algorithm. Active vibration control technique was implemented during the development of the controllers. The vibration data obtained through experimental rig was used to model the system using system identification technique based on auto-regressive with exogenous input model. Next, the developed model was used in the development of an active vibration control for vibration suppression of the horizontal flexible plate system using proportional–integral–derivative controller. Two types of controllers were proposed in this paper which are the hybrid Fuzzy–proportional–integral–derivative controller and intelligent proportional–integral–derivative controller tuned by artificial bee colony algorithm. The performances of the developed controllers were assessed and validated. Proportional–integral–derivative–artificial bee colony controller achieved the highest attenuation for first mode of vibration with 47.54 dB attenuation as compared to Fuzzy–proportional–integral–derivative controller with 32.04 dB attenuation. The experimental work was then conducted for the best controller to confirm the result achieved in the simulation work