Journal of Intelligent & Fuzzy Systems 30 (2016) 1403–1410 DOI:10.3233/IFS-152053 IOS Press 1403 Optimization of hybrid robot control system using artificial hormones and fuzzy logic Mohammad Bagher Fakhrzad ∗ and Moheb Ali Rahdar Department of Industrial Engineering, University of Yazd, University Blvd. – Safayieh, yazd, Iran Abstract. This paper presents a method for hybridizing artificial hormones controller with type-2 fuzzy controller. Artificial hormones robot control system provides the ability to self-control, while the fuzzy controller is appropriate for nonlinear systems with time delay and dynamic systems. This paper presents three feasible scenarios of hybridizing two controllers. Controller performance indicators, such as settling time, overshoot, steady state error, and integrals known as feedback error performance indices (integral absolute error [IAE], integral squared error [ISE], integral time-weighted absolute error [ITAE], integral of time multiplied by the squared error [ITSE]), were studied and compared. The results of the hybrid controller for each of the scenarios show that it has better performance than any of the fuzzy and artificial hormone controllers alone. Energy consumption in the base and hybrid controllers was compared. The results show that the energy consumption for the hybrid controller is 20 to 30% less than the base controller. Keywords: Robot control system, hybrid controller, artificial hormone controller, fuzzy type-2 controller, performance indices 1. Introduction In recent years, some controllers have been designed based on artificial hormones, and were patterned after the living systems which accord them- selves with the environment. These controllers have resulted into the self-control attribute of robots in different environmental situations and even in times when a robot breaks. Fuzzy controllers which are based on fuzzy logic are the kind of controllers appropriate for nonlinear and delayed systems with unclearly known dynamic. Many researchers have used fuzzy systems in control field and have obtained satisfactory results. Considering the advantages of the mentioned controllers, the first idea to use the advan- tages of both controllers, is to combine them. The constraints of each of the controllers do not exist or are improved in the hybrid controller. ∗ Corresponding author. Mohammad Bagher Fakhrzad, Department of Industrial Engineering, University of Yazd, Uni- versity Blvd. – Safayieh, yazd, Iran. Tel./Fax: +98 35 31232405; E-mail: mfakhrzad@yazd.ac.ir. 2. Artificial homeostatic hormone system (AHHS) AHHS was first developed through SYMBRION and RERLICATOR projects [1]. In these projects, the main concentration is to build a number of small automated robots which can join each other automat- ically and make one or more symbiotic organisms. In a study conducted by [2], artificial evolutionary algorithm was used to self-control a robot control system. AHHS1 and AHHS2 are two of the devel- oped AHHS. AHHS1 was proposed and applied in both robot simulation [3] and real robots [2]. Fig- ure 1 shows an example of AHHS1 application on a simple robot with two wheels. As shown in Fig. 1, the interior space of the robot is devised into section by a vertical dotted line. The left section contains a sensor and motor, the right sec- tion contains right sensor and motor and the middle section does not contain any sensor or motor. The actuated sensors make the hormones secretion to dif- fuse toward the middle. If the sensors are the distance related sensors, then there are two sensors, S l (t ) for 1064-1246/16/$35.00 © 2016 – IOS Press and the authors. All rights reserved