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 development of structured methods for proportional-integral (PI) controller design for systems with time delay are proposed in this article. Several PI controller design methods for time-delay systems have been reported. However, combining two or more methods to form new ones have not been given serious attention. The system stability region in the controller parameters space was determined by plotting the stability boundaries. In this study, the controller gains were first obtained using genetic algorithm (GA), weighted geometric center (WGC), and centroid of convex stability region (CCSR). Thereafter, these gains were combined by finding the centroids of lines joining any of the two gain locations, and triangle whose vertices are the location of the three gains in the convex stability region, thus yielding four additional methods, M1, M2, M3, and M4. Compared to a particular existing method, some of the proposed methods yield faster response speed at the expense of reference input tracking, while the reverse is the case for others. Any of the proposed methods (M1, M2, M3, and M4) can be selected depending on the system performance specifications.

Tool development and prime mover selection for optimum tillage operation require both the knowledge of soil and tillage tool interaction dynamics which is a function of some system parameters. The actual value of these parameters can only be determined either from field or soil bin experiment via appropriate instrumentation systems. Several published works have been reported on development of soil bin instrumentation system. However, development of a system that can measure and log all the required parameters simultaneously in real time remains an active area of research. The distance moved and the forces acting on the tool were sensed using potentiometer and load cells, respectively. The sensed parameters and the calculated tool linear velocity were processed in parallel using microcontroller with optimised code to ensure real-time and simultaneous logging. The developed system was used for measuring and logging the distance moved by the tool, its velocity as well as the x-, y-, and z- components of force acting on the tool. The values of the distance, velocity and force were determined any time from the start of tillage operation are available on the chats of distance/velocity/force against time obtained from this work. 10 seconds from the start of tillage operation, the distance moved by the tool, tool velocity, , , and  are 2.56 m, 0.27 m/s, 147.00 N, 5.00 N, and 15.00 N, respectively.

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.

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

To achieve optimal dryer performance, the process parameters required for both the optimization and control of the drying process must be made available via the instrumentation system. A few works have been reported on the development of instrumentation systems for handling drying system parameters. Out of which, some are deficient in the number of drying process parameters that can be handled, while others are unreliable and inaccurate. Therefore, there is the need to develop a microcontroller-based instrumentation system that can monitor, measure, control, display and store the main drying process parameters and sample weight with a high degree of reliability and accuracy. In this study, the sensors were selected based on system specifications and interfaced with the microcontroller. The codes for controlling, logging and displaying of drying parameters were developed and installed on the microcontroller. When tested at steady-state conditions, the system yielded satisfactory results with maximum control and detection errors being 2.0% and 1.8% for the temperature and sample weight, respectively. The developed system can be used for efficient computation of both the dry and wet basis sample moisture content values and also detect the set sample weight. Keywords— Dryer, Drying parameters, Instrumentation system, Moisture content, Sensor.