  We show a control algorithm to guide a robotic walking assistant along a
planned path. The control strategy exploits the electromechanical brakes
mounted on the back wheels of the walker. In order to reduce the hardware
requirements we adopt a Bang Bang approach relying of four actions (with
saturated value for the braking torques).When the platform is far away from the
path, we execute an approach phase in which the walker converges toward the
platform with a specified angle. When it comes in proximity of the platform,
the control strategy switches to a path tracking mode, which uses the four
control actions to converge toward the path with an angle which is a function
of the state. This way it is possible to control the vehicle in feedback,
secure a gentle convergence of the user to the planned path and her steady
progress towards the destination.
