  This chapter is dedicated to the so-called cuspidal robots, i.e. those robots
that can move from one inverse geometric solution to another without meeting a
singular confuguration. This feature was discovered quite recently and has then
been fascinating a lot of researchers. After a brief history of cuspidal
robots, the chapter provides the main features of cuspidal robots: explanation
of the non-singular change of posture, uniqueness domains, regions of feasible
paths, identification and classification of cuspidal robots. The chapter
focuses on 3-R orthogonal serial robots. The case of 6-dof robots and parallel
robots is discussed in the end of this chapter.
