THREE DEGREE OF FREEDOM LEG DESIGN FOR QUADRUPED ROBOTS AND FRACTIONAL ORDER PID (PIλDμ) BASED CONTROL

Abstract

Quadruped robots are legged mobile robots that increase their popularity in robotic and control areas due to their complex dynamic structure with high mobility in different terrain conditions compared to wheeled systems. In this study; A 3-DoF linear leg model and its control are provided in order to enable quickly and effectively simulate about on such subjects that walking planning, foot trajectory design and body stability control of robot. A realistic physical model with parameters such as the dimensions, masses, inertia of limbs and the stiffness and damping values of joints is designed on Matlab/SimMechanics and simulated on Simulink environments. By taking into account the angular position ranges of the joints required for the robot to perform a standard step trajectory during the walk, the linear state-space model of the system (torque input- angular position output) is obtained using the linearization tools over the physical model. The unit step responses of the physical model are compared with the obtained linear model responses under constant torque input and it is understood to give similar results with small error values. Using the linear model, the angular position control of the system is achieved with PIλDµ controllers designed by selecting various parameters of fraction orders as comparatively the classical PID. Simulation results are presented and investigated.