PWM controlled independent six wheel drive for an all-terrain robotic vehicle

This paper deals with the robust motor control strategy adopted in a six wheeled all-terrain vehicle with a maximized obstacle negotiating capability. A slow decay PWM based independent motion control scheme has been adopted for the smooth operation of the robotic vehicle over a variety of terrains. This scheme allows for the inductive motor recirculation losses to be minimized for improved efficiency and dissipates minimum energy in the H-bridge drive stage. Shoot through is avoided by proper control over the dead time and protecting the drive stage from heavy inductive transients. The motor inductive current has been kept continuous for smoother operation and effective torque. Further, an adaptive control scheme for sensing the current requirement and the dynamic load experienced by each motor is developed for an active feedback and subsequent corrections for individual wheels, when negotiating uneven loading. Timing requirements from the implemented scheme do not mandate a strict real time deadline or a signal processing approach from the on-board computer and hence can be ported into a compact system on an 8 bit microcontroller. The performance of the drive system has been characterized in free running as well as the full load specification for the vehicle with promising results.