14 th Annual (International) Mechanical Engineering Conference – May 2006 Isfahan University of Technology, Isfahan, Iran 1 Modeling and Control of a 3 DOF Monoped Robot Amir Hossein Haji 1 , Mohammad Eghtesad 2 , Radmarz Hosseinie 3 Dept. of Mechanical Engineering, Shiraz University, Shiraz, Iran haji@shirazu.ac.ir , amir.hossein.haji@gmail.com Abstract Interests and motivations towards enhanced humanoid robots considering their applications have grown in recent years. In the present stuudy a 3–link monoped robot is studied. This robot can be used in several applications such as artificial legs and biped robots. We have simulated and controlled a model of the monoped robot by "the inverse dynamics" method and concluded that an adaptive scheme is required to set the proportional and derivative gains during different giat phases. Keywords: Walking Model – Gait – Inverse Dynamics Control. 1- Ph.D. Student 2- Ph.D., Assistant Prof. 3- Ph.D. Student 1. Introduction Study of human walking is a very familiar subject in Biomechanical Engineering. Many studies have been conducted to model the walking gait of human, also running, jumping or many other gaits. The purpose of almost all these studies has been finding the forces and moments that act in joints or on body parts, which can be used in designing artificial parts or joints. On the other hand, motions similar to human walking are needed in some robotic applications such as house keeping services, rescuing maneuvers in high risk situations for human beings, artificial legs improvement, etc. However in order to simulate the human walking using current robotics knowledge there are some difficulties which should be reviewed. In this paper, a 3–link model for a walking robot is considered. This model is controlled by the inverse dynamics method. The model is expected to simulate a typical human walking of a real foot. The experimental data are taken from reference [1]. These data are discrete and are collected in 69.9 frames per second resulting in a precision of at most 1/69.9=0.0143 sec. In section 2 the problems encountered when trying to reach a walking model and the model used in this study are presented while the control strategy is discussed in section 3. Finally the simulation results and conclusions are given in section 4. 2. Modeling of the Human Walking Modeling a mobile robot generally has more difficulties than a fixed robot. Several approaches have been investigated for mobility of the robot base. For instance, one can use the modified formulation of fixed robots for mobile robots which is however relatively complex. Another popular solution in walking studies is to assume the mobile robot as a fixed robot on a moving ground. In the case of low acceleration motions like slow walking we can suppose the hipbone as the base hinge. The next crucial point which should be regarded in walking simulation is the number of degrees of freedom (DOF) we would like to consider in the model. As a complex natural behavior, the human walking process has a large number of DOF. Walking is a rhythm and each of its movements is forecasted and certain, but is strongly controlled by