Hi I'm designing an exoskeleton that would be fitted to a persons leg. I've been doing some calculations to solve for the minimum required torque to carry a persons leg at the hip joint. The equation I'm using is..

M

_{hip} = M

_{weight} + M

_{exo} + (I

_{leg} + I

_{exo})*alpha

where:

M

_{hip} = torque required at hip joint

M

_{weight} = resisting torque produced by the weight of the leg

M

_{exo} = resisting torque produced by the weight of the exoskeleton

I

_{leg} = moment of inertia of the leg

I

_{exo} = moment of inertia of the exoskeleton

alpha = angular acceleration at hip joint

I've been doing some rough calculations based on some anthropometric data and I'm getting values around 40-50Nm(I used 30 degrees as the maximum angle for the leg) for M

_{hip}.

My problem is this. Am I doing the mechanics correctly? is 40-50Nm a reasonable torque value? How/Where can i look for DC motors + gears that would accommodate this torque? Can i use relatively small motors then just gear it up to get my req torque?

Thanks to anyone who can help. I'm kinda new to this designing thing. But i'm really willing to learn.