Balancing of an inverted pendulum with a SCARA robot

Abstract

Summary form only given as follows. The balancing of an inverted pendulum with a robot is a good example for analyzing fast sensor guided movements and testing modern control strategies. This classical benchmark is difficult to achieve as it attempts to stabilize a system that is unstable in its open loop configuration. Additionally, there are sensing problems (measuring very small angles) and nonlinear effects in the actuators (friction and elasticity of the gears). The pendulum is projected to the xz- and yz-plane of the inertial coordinate system. These projections are treated independently from each other and are controlled individually by a state space controller in the x- and y-axis respectively. The nonlinearities of the robot are compensated by using inverse dynamics and inverse kinematics. A specially developed sensor system allows the contactless measurement of the angles. This system consists of a small magnet, placed at the bottom of the pendulum, and Hall effect sensors placed inside the end effector.