Trajectory planning and following for mobile robots with current and voltage constraints

Abstract

Interest in wheeled mobile robots (WMRs) is growing rapidly due to much broad range of their potential applications - industrial automation, undersea/planet exploration, nuclear/explosives handling, warehousing, security, agricultural machinery, military, education, mobility for the disabled, and personal robots, etc. Most researches considering dynamic model of WMRs confined to dynamic constraints of input torques only or just limitations of velocities/accelerations. And control inputs are velocities or accelerations with or without bounds where, for the low level control of motors, velocity-servo modules or torque-servo modules are used to generate desired control inputs. However, WMR systems have motor armature current constraint as well as battery voltage constraint in practice. Also, since final control inputs are voltages (PWM duty ratios) generated by those servo modules, there may exist bad cases where those modules cannot track the desired velocity/acceleration commands due to current and voltage constraints. Hence, efficient control algorithm for WMR systems considering those constraints is essentially required. Based on above statements, we will study TP and TF for WMRs to move fast considering dynamics with current and voltage constraints. Obstacles are not considered explicitly. Instead, we consider the bound of path-deviation, which limits deviations from the given configuration, and hence obstacles can be avoided. For TF, an off-line minimum-time velocity control algorithm (TF-MV) is developed considering all constraints of each step. However, the TF-MV algorithm is complex and slow for real-time TF for WMR system. For this reason, we will propose an on-line near minimum-time TF algorithm (TF-NV) based on maximally scaling in the first control step solved from inverse model, which is simple but yields good performance close to minimum-time control with regard to the number of steps. The comparison of performances will be discussed with various ...