“…Future robotics is likely to require highly complex tasks: bipedal machines which walk/run/jump/crawl and more [134,135,136,119], quadruped robots which walk/run/gallop/trot/amble/bound/pace/half bound/transversally gallop/kick/jump on their rear legs, robots which grasp/dexterously manipulate/push/tap/juggle [137,138,9], robots which throw/catch [139,140], which climb/slide along poles, quadropters which juggle/catch/throw a ball [141,142], manipulation with mobile manipulator for timber harvesting tasks [143], etc. In all cases the contact points should be allowed to stick or/and to slip [144], which is unavoidable as it is shown on simple examples in [118].…”