Dynamical Analysis in Leg of Humanoids

Project Leader: Kiwon Sohn

Goal: Robotic Biarticulate Muscle Leg Model Simulation

Features: 1. Analysis of Biarticulate Muscle leg in Humanoid robot.      2. Dynamics study using Dap3d 3. Run by Matlab

Abstract of This Project:

The human body which is a large degree of freedom system is actuated by muscle which many of

they are biarticulate, that, is, they act on more than one joint simultaneously. This is much different

from most of current robot system which require actuators to make a movement. Therefore, some

roboticist tried to construct of a neurorobotic robot systems in order to mimic human body and to study

the relationship between neuronal networks responsible for control of movement and the complex

musculo-skeletal system. Figure which we present below shows a robot systems of humans lower limb.

In this platform, actuators are used just for changing elastic parameter of muscle, not for actuating links. In real experiment, this robot leg system even can not stand by itself due to difficulty of controlling

biarticulate muscle and getting proper weight of each link and spring constant. In this study, I built

a same model with Figure above and try to stand by it self while balancing. And by changing spring constant of several muscles, I made a simple movement of leg while it balance.

Figure below shows drawing of Biarticulated human leg model which I constructed. As can be seen in

figure, It consist of four different links which consist of Hip, Upper leg, Lower leg and foot. And seven

different biarticulated muscles ( linear spring, that is, PTP force) are attached.

Four links are combined by revolute joints and one tip and COM of foot is attached to ground by Z-

constraint. Parameters which are used in this model are described in Table.

As can be seen in Figure of model, Gastrocnemius consist of two different linear spring, so I divided

Gastrocnemius into 1 and 2 like presented in Table3. All of these parameters are gotten by continous

experiment and this set of paramter make this human leg system stand up by itself while balancing.

Like actuator in robot system in Figure of robot platform, I changed spring constant of several spring and could see some interesting case which leg model try to slide its foot while balancing.