An apparatus which comprises a manipulandum that is configured as a
surgical instrument; a closed loop linkage system which includes a first
central member fixedly coupled to a first object coupling and a second
central member fixedly coupled to a second object coupling, wherein the
first and second object couplings are separately coupled to the
manipulandum to allow the manipulandum to be moveable in a plurality of
rotary degrees of freedom and an axial degree of freedom; a force
feedback system is coupled to the linkage system, wherein the force
feedback system selectively applies resistive forces to the manipulandum
based on the position of the manipulandum with respect to one or more
reference coordinates. In an embodiment, the force feedback system
includes an actuator to provide a force to the manipulandum in at least
one degree of freedom in response to signals received from a computer
system.