Hi, my name is Francisco and I'm currently finishing my Master Thesis in Biomedical Engineering at Instituto Superior Técnico, Lisbon. For this project I developed a controller based in the Hartmut Geyer and Hugh Herr article "A Muscle-Reflex Model That Encodes Principles of Legged Mechanics Produces Human Walking Dynamics and Muscle Activities". The goal of this project is to develop a walking pattern based on reflexes that is going to be applied in some Robot.

Currently, I believe the controller is well design in Matlab/Simulink (with a plot representation of the walking pattern) and the next step is to optimize 20 parameters such as spring stiffness and force feedback gains, in order for the "stick man" to walk a long time and not just 2 steps as it happens currently.

My problem here is that i found that is really difficult to develop a cost-function to be used in the optimization problem, in order to achieve a stable walking pattern at 2D. I've tried using a minimization of the energy expend, such as minimizing the moments applied at each joint (ankle, knee and hip), but the model simply tries to push himself out of simulation in order to have this value minimized (the simulation stops when the knee goes into hyper-extension or the "stick man" falls. I have also tried to maximize the distance traveled by the hip, but the model tends to jump forward to maximize this value, and does not understand that if he put one foot in front of the order continuously, that will lead to a greater distance traveled.

Can somebody help me solve this cost-function problem?

Thank you in advance for your consideration.

Currently, I believe the controller is well design in Matlab/Simulink (with a plot representation of the walking pattern) and the next step is to optimize 20 parameters such as spring stiffness and force feedback gains, in order for the "stick man" to walk a long time and not just 2 steps as it happens currently.

My problem here is that i found that is really difficult to develop a cost-function to be used in the optimization problem, in order to achieve a stable walking pattern at 2D. I've tried using a minimization of the energy expend, such as minimizing the moments applied at each joint (ankle, knee and hip), but the model simply tries to push himself out of simulation in order to have this value minimized (the simulation stops when the knee goes into hyper-extension or the "stick man" falls. I have also tried to maximize the distance traveled by the hip, but the model tends to jump forward to maximize this value, and does not understand that if he put one foot in front of the order continuously, that will lead to a greater distance traveled.

Can somebody help me solve this cost-function problem?

Thank you in advance for your consideration.

## Comment