Trajectory Planning for a Stair-Climbing Mobility System Using Laser Distance Sensors

This paper describes trajectory planning for a stair-climbing mobility system (SCMS). The planning is based on the results obtained from an estimation of the dimensions of the stairs. The strategy used to estimate the stairs' dimensions considers scanning the surface of the stairs using two laser distance sensors, which are attached to the chassis of the system. This strategy can be also used to calculate the distance from the system to the staircase. The strategy contemplates a process with which to align the system with the staircase before scanning. The results of the scanning are geometrically interpreted to estimate the dimension of the staircase. The estimation results are then used to generate the trajectory planning for the SCMS before confronting the staircase. This approach has the advantage of being able to generate smooth and accurate reference trajectories. The locomotion and the verticality of the system chassis are controlled with a nested control-loop scheme. Experimental results are depicted to demonstrate the effectiveness of the trajectory planning presented and to exhibit the capacity of the SCMS to climb up and down staircases on its own.