You can find a several papers dealing with this type of control problems. The robot is just an example of simulation to prove the effectiveness and the feasibility of the proposed controller. you can see the attachments files.
I'm working on Non-singular Fast Terminal Sliding Mode Controller (NFTSMC) based on Wavelet neural network for trajectory tracking of the robotic arm.
The basic idea consists of expressing the system as a sum of a well-known nominal term and uncertainty, then approximating the uncertainty with a wavelet neural network.
The confusion I'm facing is how to be sure that I have the good approximation?