The present invention provides compounds of the following structure, wherein R1, R2, R4, R4\u2032, R6, R7, and R15 are defined above:These compounds are useful in treating neurological disorders or complications due to stroke or head injury; benign or malignant neoplastic disease, carcinomas and adenocarcinomas; proliferative disorders; and inflammatory disorders. The controller is configured to maneuver the robot to turn in place and to redirect the robot in response to the bump sensor sensing contact with an obstacle. The moments of inertia of the useful mass and of the counter mass are in a defined ratio to one another and the pot, which can be mounted exchangeably, is designed so that the moment of inertia of the useful mass and, with that, the ratio of the moments of inertia remain essentially unchanged.