Dynamic analysis and control of traversing stairs with an actively stabilized wheelchair

Summary form only given as follows. A new type of wheelchair is proposed in the form of a two-wheeled coincident-axle mounted double inverted pendulum, capable of traversing irregular terrain, ramps, and staircases. The device is actively stabilized by torques applied between the components at the pivot joints, through a feedback control system. This paper discusses the modeling of the device, the design of the control system, and the feasibility of using the proposed configuration as a viable wheelchair. Equations of motion are derived from the Lagrangian of the energy equations formulated from the geometry of the device. The equations of motion are linearized around an operating point and state matrix equations are formed for the purpose of designing a controller. The control gains are found using a linear quadratic regulator. The behavior of the device with a controller is examined for motion on a flat surface, ramps, steps, and a four-step staircase. The feasibility of the device as a practical, buildable, safe new type of wheelchair is explored in the areas of clearances and interferences, accelerations on the passenger, torque and power requirements, disturbances caused by rider movement, shear and friction forces on the tires, robustness, and real-life implementation using realistic sensors with a reduced order observer as well as implementation of the linearized controller on the non-linear plant.