I. INTRODUCTION
Healthcare robots can help people to do some homework,
and reduce the workload of caregivers, in some healthcare
system, it is useful to improve the life quality of the old and
the disabled. To make nursing service robot be widely used
in practical, it is a very necessary job to achieve natural
communication between human and robots. Unlike in
industrial robots field, only expert operators can
communicate and operate industrial robots, the operators are
ordinary people in service robots field, such as the old, the
disabled and autistic patients, etc[1],and many of them have
some cognitive impairment or a certain weakening ability.
So it is valuable to study the interaction mechanism between
human and robots