International Journal of Computer Applications (0975 – 8887) Volume 73– No.5, July 2013 26 Effects of PID Controller Location in the System loop of Mobile Satellite Dish Network Aye Taiwo Ajiboye National Centre for Agricultural Mechanisation, Ilorin, Nigeria Tunji Samuel Ibiyemi Department of Electrical and Electronics Engineering, University of Ilorin, Ilorin, Nigeria Alaba John Falade Department of Electrical and Electronics Engineering, University of Ilorin, Ilorin, Nigeria ABSTRACT The effects of proportional-integral-derivative (PID) position controller location within the structure of network of mobile satellite dish spread all over Nigeria on system performance were investigated. The region of acceptable stability for the system was graphically determined in the integral gain, K i – derivative gain, K d plane for the determined value of proportional gain, K p . Values for K i and K d were determined within the stability region. The determined values of K p , K i and K d were slotted into the PID controller transfer function. The resulting controller was then connected to the system as series compensation and feedback compensation respectively. After putting together the composite system transfer function for uncompensated, series compensated and feedback compensated systems, they were then subjected to a step input forcing function, which yielded time domain performance indices for these systems using MATLAB as a simulation tool. The obtained time domain performance indices for the uncompensated system, series compensated system and feedback compensated system show that the series compensated system has superior performance followed by uncompensated system and the feedback compensated system has the worst performance indices. General Terms Control Systems Keywords feedback compensated system, Nigeria, PID controller, satellite dish network, series compensated system, stability region, uncompensated system. 1. INTRODUCTION Accurate position control is critical to every satellite dish system, either mobile or stationary. As a means of ensuring that the satellite dishes in the mobile/stationary satellite dish network remain pointed and locked to a desired geostationary satellite at all time appropriate robust position controllers are normally introduced into the system. The command and control in this work is based on Proportional-Integral-Derivative, PID, controller algorithm. However, the effectiveness of PID controller is largely determined by the amount of delay between the formulation of PID control law and its delivery to the actuator [1]. It was established that the performance of PID controller degrades with increase in time delay. This is because the formulated corrective action is based on the past output and not the current output being corrected [2]. The design of a robust and effective PID controller in a supervisory control configuration of network of mobile nodes with large and variable time delays within Nigeria was considered in [1]. In the work an effective control and delay management of a national area network of mobile vehicles carrying satellite dishes either in fixed position or moving at a maximum speed of 240 km/hr within Nigeria was considered. There was remarkable improvement in the compensated system performance when the performance indices for the compensated and uncompensated systems were compared, although the controller element was added to the control loop as series compensation. It has been established that the controller element can be added to control loop as series compensation or feedback compensation [3], [4], [5] but the effects of controller location within the structure of network of mobile satellite dish position control system has not been given serious attention. This paper presents our work on the investigation of effects of controller location within the structure of national area network of satellite dishes mounted on vehicles in either parking position or moving at a maximum speed of 240km/h within Nigeria on system performance. The central control office, CCO is assumed to be at Abuja, the data is via Nigcomsat-1R satellite and the mobile nodes are distributed within Nigeria. The two parameters needed to formulate the control law are the round trip delay, and the plant transfer function. Round trip time delay is the sum of delays from the plant to the satellite, the satellite to the CCO, CCO to the satellite, and the satellite back to the plant; or vice versa. Therefore, a model for predicting the end-to-end delays was developed; and the plant’s transfer function was empirically determined. The plant is the Outdoor Unit consisting of a dish, block up converter/low noise block converter, and a jack actuator. The transfer function is determined from the plant total mass, spring constant, and damping coefficient. The round trip delay model is based on calculating the round trip distance divided by the speed of light at 30 x 10 9 m/s. The three PID parameters required are the proportional gain value, K p , integral gain value, K i , and the derivative gain value, K d that guarantee system stability in spite the control action and time-delay. Firstly the acceptable value of K p was obtained using root locus method. Then for the determined value of K p , the region of acceptable stability for the system was graphically determined in the K i - K d plane. Values for K i and K d were determined within the region of stability. The determined values of K p , K i and K d were slotted into the PID controller transfer function. The resulting controller was then