The need for effective design of satellite attitude control (SAC) subsystem for a microsatellite is imperative in order to guarantee both the quality and reliability of the data acquisition. A proportional-integral-derivative (PID) controller was proposed in this study because of its numerous advantages. The performance of PID controller can be greatly improved by adopting an integral time absolute error (ITAE) robust controller design approach. Since the system to be controlled is of the 4 th order, it was approximated by its 2 nd order version and then used for the controller design. Both the reduced and higher-order pre-filter transfer functions were designed and tested, in order to improve the system performance. As revealed by the results, three out of the four designed systems satisfy the design specifications; and the PD-controlled system without pre-filter transfer function was recommended out of the three systems due to its structural simplicity, which eventually enhances its digital implementation.

Designs of electromagnetic (EM) coil have attracted a lot of attention in the research community due to its applications in several areas of human endeavours. However, the optimal selection of coil wire size and current in the design of Square Air-Core Multi-turn Multilayer Electromagnetic Coil (SAMMEC) with significant wire diameter for both safe and cost-effective products has not been given enough research attention. Therefore, the equation for the flux density produced by a rectangular loop of wire was adopted in the modelling of SAMMEC with significant wire diameter. A coil design chart was constructed based on the developed model and design specifications. Both the feasible and non-feasible design regions and the line of optimum magnetic flux density were identified on the constructed chart. The appropriate wire size and current for the coil were both determined from the design-chart. The diameter, length, resistance, copper loss, and weight of the selected wire for the generation of 0.06 T flux density were found to be 0.00326 m, 267.01 m, 0.5502 Ω, 263.87 W, and 19.86 kg respectively. The selected wire can produce an optimum flux density of 0.066 T with current of 24 Amp and associated copper loss of 316.92 W. Keywords—Air core, Electromagnetic coil, Magnetic flux density, Multilayer, Multi-turn

Design of proportional-integral-derivative (PID) controller with proportional, integral, and derivative gains given by ,  and  respectively, for time-delay systems is presented in this study. The centroid of the convex stability region (CCSR) method in the -  plane for fixed  is used. PID controller design for time-delay systems in the -  plane for a fixed  and -  plane for a fixed  have been extensively researched. Despite the amenability of CCSR method to design of PID controller in the -  plane for fixed , its application in this regard has not been given serious attention. The stability region in -  plane for fixed  was determined and the required controller gains in the region were determined using the CCSR method. Using the determined controller gains, the system closed loop unit step response for all the considered regions was plotted on same axes. Based on the obtained results, different combinations of controller gains can be implemented depending on the system time domain performance measures (TDPMs) requirements. However, selection of an appropriate controller gains combinations, requires compromise among any of the conflicting TDPMs.

The MQ-series gas sensors are attractive candidates in the area of gas concentration sensing due to their high sensitivity and low cost. Even though the sensor circuit sensitivity and sensor power dissipation level both depend on load resistance, the process of the load resistance selection has not been well researched, hence the need for this study. The derivation of model equations for determining the sensor circuit sensitivity and sensor power dissipation is presented. The derived equations were used to investigate a typical scenario of MQ-6 gas sensor under the influence of liquified petroleum gas (LPG). The variation of sensitivity with load resistance and that of power dissipation with sensor resistance were parametrically investigated. The load resistance that yields maximum sensor circuit sensitivity with the maximum sensor power dissipation less than the set threshold is the candidate resistance for the sensor circuit. The 20 kΩ load resistance recommended for MQ-6 in the datasheet was authenticated in this study, yielding the maximum possible sensor circuit sensitivity and tolerable sensor power dissipation of 0.195 mV/ppm and 3.125 × 10 −4 W, respectively.

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This paper presents the design and construction of a device for measuring compressive force of engineering and biomaterials. The device was calibrated and tested. The results obtained show that the device is adequate for measuring compressive force, ranging from 0-100kN in a situation where a percentage error of up to 0.4% is permissible.

Water is said to be magnetized when it flows across the magnetic field and magnetized water finds its application in many areas of life. Despite the numerous benefits of magnetized water, very little works have been reported on the development of magnet for water magnetizer application. In most of the reported works, the detailed theoretical analysis and design procedure required for the development of the magnet was not accounted for; hence the need for the present study. Electromagnetic means of producing flux density is considered in this study due to its advantage of flux density variation, which is not achievable with the use of its permanent magnet counterparts. The design equation of short electromagnet was derived from the existing equations of coil magnetic flux density and then used for the air core electromagnet design. The variation of the magnetic flux density with the distance between two electromagnets was empirically investigated. The performance of the developed electromagnet is satisfactory, as the flux density varies between 814.6 and 510G corresponding to the gap (0 - 4cm) between the coils (i.e., water pipe diameter). Keywords— Air core, Coils, Iron core, Magnetic flux density, Magnetized water

The design of a Proportional-Integral-Derivative (PID) controller with proportional, integral, and derivative, gain, k p , k i , and k d , respectively, for a time-delay system, is quite common, particularly in the k i - k d plane, for a fixed k p or in the k p - k i plane, for a fixed k d . These design methods have been widely reported in the literature, however, the process of investigating the effects of using any of these design planes on system performance has not been given serious attention hence the need for this study. The stability region in the k i - k d and k p - k i design plane for a fixed value of k p and k d respectively were determined. For every determined stability region, the optimum value of controller gains in the plane was determined using a genetic algorithm (GA) with the integral of time multiplied by absolute error (ITAE) used as the objective function. The optimum value of the fixed gains was graphically determined by plotting the minimum of ITAE (Min-ITAE) for each stability region against the fixed gains. The overall optimum controller gains are the fixed gain that gives minimum of Min-ITAE (Min (Min-ITAE)) and the gains that resulted in Min-ITAE that yielded the Min (Min-ITAE). Using the determined overall optimum controller gains, the system closed-loop step response was plotted for the two design planes and the time domain performance measures (TDPMs) were determined. Based on TDPMs obtained for examples 1, 2, and 3, the k i -k d design plane yielded a faster response while the k p - k i design plane yielded a response that closely tracks the input irrespective of the system type and order. The study will enable control system designers to select the design plane that will give the best system performance right from the start of controller design without involving trial and error once the system transfer function and design specifications are known.