Simulation Results

Motion Genesis™ creates 32 sets of equations of motion for the 32 degrees of freedom human body model. As mentioned earlier, Motion Genesis™ can generate sets of equations of motion in MATLAB™ or C++ format. The generated code actually integrates Motion Genesis™ equations forward in time using a fourth-order Runge Kutta integration scheme. This process creates data files including kinematics data of the body such as displacement, velocity and acceleration which can be plotted employing a simple script to view the results. For the present human body model, the simulation time is approximately 5 seconds for the chosen time step size of 0.01 seconds. Each simulation took 10 minutes to run in Motion Genesis™ and the generated MATLAB™ code took another 15 minutes to compile. In the following two sections, two sets of output are presented: Joint angular velocities which correspond to Gyroscope outputs and segment accelerations which correspond to the accelerometer outputs. These two quantities are important in the epileptic seizure analysis and are specially used in the following chapter for optimization purposes.

2.4.2.1

Joint Angular Velocities

In this section, some of the important joint angular responses during epileptic seizure input are presented. These joints are selected from the upper-body since in practice, myoclonic seizure movements have been found to be dominant in the arms than any other part of the body. The list of joints that is considered here includes elbow, wrist and shoulder.

To study of the reaction of the muscular system to the seizure input, the angular velocity response of the human body model is considered to be of interest. The simulated angular velocity output can form an understanding of the human body mechanism and system identification in terms of magnitude, frequency and response. The acquired data can become useful prior to performing the experiments with this class of sensors and can be helpful in predicting the output plots that can be achieved from the gyroscope sensors. Figure 2-15 to 2-17 display simulated responses to a moment applied on the shoulder joint in the z-direction. As expected, the angular velocity responses in the x and y

directions are relatively small and the responses consist of cross-coupling effects as well as some numerical noise. However, it can be seen from the Figure 2-17 that the response in the z-direction shows a sudden, abrupt impulsive response with exponentially decaying trend of the wrist joint angular velocity which initially in the opposite direction of the applied moment (i.e. in the positive direction of the z axis) but then gets to the same direction as the applied moment. The response can be explained by considering the fact that the moment is applied on the shoulder joint and the movement of the arm and forearm causes the motion of hand which is initially in the opposite direction of the moment applied on the shoulder but eventually as the moment generated motion overcomes the action of springs and dampers, it rotates in the same direction as moment. Based on these plots of the angular velocity components in the three directions tend to go to zero in steady state condition.

Figure ‎2-16: Wrist angular velocity in the y-direction

It should be also noted that the moment applied in the z-direction creates two significantly small angular velocity components in the x and y directions. These two components are due to the highly nonlinear and complex nature of the human body model and hence can be neglected compared with the z component of the angular velocity. Considering that the components of angular velocity in the x and y directions are negligible, only the z-direction angular velocity plots are presented for the shoulder and elbow joints.

As shown in Figure 2-18 and Figure 2-19, an applied moment to the shoulder joint results in a sudden, abrupt impulsive response of the elbow and shoulder joints which is initially is in to the same direction as the applied moment with a zero steady state response.

Figure ‎2-19: Shoulder angular velocity in the z-direction

2.4.2.2

Segment Accelerations

In the same manner as previous section, joint acceleration responses during epileptic seizure input are presented. These joints are selected from the upper-body since as established earlier myoclonic seizure movements are dominant in the arms than any other part of the body. The list of joints that is considered here includes elbow, wrist and shoulder.

To study of the reaction of the muscular system to the seizure input, the acceleration response of the human body model is of interest. The simulated acceleration output can form an understanding of the human body mechanism and system identification in terms of magnitude, frequency and response.

Figure ‎2-20: Hand acceleration in the x-direction

Figure ‎2-22: Hand acceleration in the z-direction

As shown in Figure 2-20 to 2-22, an applied moment to the shoulder joint results in a sudden, abrupt impulsive response with an exponentially decaying response of the hand in the x-direction. The plots also display the expected behavior where all of the three acceleration components in steady-state approach the equilibrium configuration. It may be also noted that the moment applied in the z-direction creates two significantly small acceleration components in the y and z directions. These two components are due to the highly nonlinear and complex nature of the human body model and can be neglected. Considering that the components of acceleration in the y and z directions are negligible, only the x-direction acceleration plots are presented for the forearm and arm segments.

Figure ‎2-23: Forearm acceleration in the x-direction