Have a look at A PAWL for Enhancing Strength and Endurance during Walking Using Interaction Force and Dynamical Information
document, it has most of the information You need.
This is not an easy project to take up, especially if You are new to robotics
I wanted to take up produce exoskeleton leg
as my undergrad project artifact, however, the deeper I researched it, the more difficult it looked.
It looks quite straightforward at first, but once You give it a bit more thought You understand that there is more in it than You could initially imagine.
Give a thought to sensor
related area of this project, how is the robot going to know when person wants to stop/start walking, change walking pace, step backwards, etc...
Think about battery
related area of this project, howare You going to power up 3 DC motors/servos that are high torque
or high speed (if You use harmonic drive system)
and require a lot of current
, what sort of battery are You going to use to provide many Ah
, where are You going to place the battery if it is bulky, etc...
These are just to things to think about, there definitely are more to take into consideration.
This is a cool, however very demanding project; spend lots of time on the drawing board, consider possible ifs
, research what other achieved so far, how they achieved it, find schematics, part lists, etc...