Modelling of a novel in-pipe microrobot design with IPMC legs M Vahabi*, E Mehdizadeh, M Kabganian, and F Barazandeh Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran The manuscript was received on 13 March 2010 and was accepted after revision for publication on 23 June 2010. DOI: 10.1243/09596518JSCE1042 Abstract: The majority of research activities on microrobotics have been devoted to fabrication and design. The lack of work on modelling and simulation is significant. The majority of microrobots are in-pipe microrobots. This paper presents a new in-pipe microrobot taking advantage of ionic polymer–metal composite (IPMC) actuators. The design and modelling of the robot is presented in this paper. The mathematical model of the microrobot is obtained using the extended Hamilton principle (EHP). Four steps are taken for the robot in every movement cycle. The modelling process has to be carried out for each step separately. The non-linearity of IPMC and the type of motion gait increases the complexity of the model. The main aim is to design the parameters such that the speed of progress is increased. The modelling results show that the body mass does not affect the motion speed. They also reveal that by increasing the foot angle and reducing the spring stiffness, the speed of motion will increase as well. Keywords: ionic polymer–metal composites (IPMC), in-pipe robot, microrobot, robotics, design, modellling 1 INTRODUCTION In-pipe microrobots have different applications, from endoscopy and colonoscopy to nozzle inspection. Based on the field of application, different designs have been presented. Former research studies have mainly taken advantage of conventional actuators such as electrical motors, electropneumatic cylinders, and electromagnetic solenoids. Iwashina et al. [1] described an in-pipe microrobot in which a motor was rotating a screw to make the robot walk. Anthierens and Be ´temps [2] employed a pneumatic microactua- tor, in their robot, to inspect vapour generator pipes. The design by Thomann et al. [3] was for intestinal inspection using an electropneumatic actuator. Utiliz- ing an electromagnetic actuator, Guo et al. [4] pro- posed a microrobot capable of moving along a narrow passage. Li and He [5] presented a crawling micro- robot, also with an electromagnetic actuator. Recent developments in materials and polymers have opened up new perspectives on actuator design. One of the most promising actuator materials is ionic polymer–metal composite (IPMC). IPMC is a wet electro-active polymer (EAP), bending in an electric field [6, 7]. It consists of a thin polyelectrolyte membrane (Nafion or Flemion) with a noble metal (generally gold or platinum) chemically plated on both sides. Low driving voltage, fast response, low weight, large bending deformation, low noise, bio- compatibility, and miniaturization are some of the significant characteristics of IPMC. These properties allow IPMC to provide a wide spectrum of applica- tions, such as robotics, biomedics, the toy industry, space industries, and so on. The most attractive feature of IPMC is the ability to emulate the operation of biological muscles, owing to their high fracture toughness, large defor- mation, and inherent vibration damping. Lee et al. [8] developed a natural muscle-like linear actuator using IPMC; Yun and Kim [9] proposed a three- finger gripper in which each finger (IPMC actuator) can be actuated individually. Lee et al. [10] applied thick IPMC films to artificial fingers. *Corresponding author: Department of Mechanical Engineering, Amirkabir University of Technology, 424 Hafez Avenue, Tehran, Iran. email: meisam_vahhabi@yahoo.ca 1 JSCE1042 Proc. IMechE Vol. 224 Part I: J. Systems and Control Engineering