Basic steering control methods for the articulated body mobile robot

This paper investigates an optimal steering control method for the articulated body mobile robot KORYU-II (KR-II), considering energy consumption and trajectory tracking performance as the optimization criteria. The computer simulations of the basic control methods of KR-II´s θ axis (bending motion between the segments) and s axis (rotation motion of the wheels), lead to the conclusion that the best methods are: the “θ2 method” combined with the “θ4 method” for the θ axis, and the “s3 method” for the s axis. The “θ2 method” takes the moving average value of the foremost segment´s control angle θ₀ over a traveled distance L (intersegment length) as the next segment command θ₁ and then shifts θ ₁ to the following segments according to the moved distance. The “θ4 method” entails setting a small position control gain for the θ axis. The “s3 method” controls the forward velocity of the robot by equally distributed torque commands for all wheels. The experiments by the mechanical model KR-II demonstrated that the introduced control greatly reduces the energy consumption and produces very smooth locomotion; although the trajectory tracking performance is somewhat deteriorated