For a better understanding of the arm stiffness a simulation of the elbow joint should be developed. The model stated on the right side was written in Matlab. The basis for the muscle contraction is the muscle model developed for Hill. This model contains three elements: one active element (CE) and two passive elements (SE, PE).The active element is described as an attenuator. The passive elements are described as plumes.
The model has the following input parameters: the force of every muscle and the duration of the force. The output parameter is the angle between the upper arm and the forearm. The torque which is caused by the several muscles can be seen as well. The muscles which are included in the model can be seen in the following figure.
To enhance this model a lot of understanding regarding the dynamics of the elbow joint will be needed. So we will have to learn a lot about the muscle contraction, the short/long latency stretch reflex and the multi joint muscles.
