  Recently, the lower limb exoskeletons which providemobility for paraplegic
patients to support their daily life havedrawn much attention. However, the
pilots are required to applyexcessive force through a pair of crutches to
maintain balanceduring walking. This paper proposes a novel gait
trajectorygeneration algorithm for exoskeleton locomotion on flat groundand
stair which aims to minimize the force applied by the pilotwithout increasing
the degree of freedom (DoF) of the system.First, the system is modelled as a
five-link mechanism dynam-ically for torque computing. Then, an optimization
approachis used to generate the trajectory minimizing the ankle torquewhich is
correlated to the supporting force. Finally, experimentis conducted to compare
the different gait generation algorithmsthrough measurement of ground reaction
force (GRF) appliedon the crutches
