Exoskeleton – part 5 of 6

KINEMATIC AND DYNAMIC ANALYSIS OF THE WALKING CYCLE

Continuing with the design project of an exoskeleton, we will start with the kinematic and dynamic analysis of the walking cycle.

Before taking an in-depth analysis, it is necessary to make a model, assemble the leg and the exoskeleton, and assign a mass to each component. Afterwards, the connectors between the parts and the model restrictions of the model should be established. The only imposed restriction is to fix the chain joint but allow for rotation. Between the rest of the bodies, revolution joints are defined and, finally, fixed joints are placed between the parts of the exoskeleton and the leg. It is also necessary to define an action pair in each of the revolution joints—this pair will be provided by the control.

Kinematic analysis:

To model the kinematics of the exoskeleton, the methodology proposed by Denavit-Hartenberg for kinematic chains is used. This method is routinely employed in manipulator robots.

The kinematic analysis allows us to ascertain the position and angle of each of the joints.

Dynamic Analysis:

Performing an appropriate dynamic analysis in this type of device is of vital importance. For example, oversizing the motor would add a mass to the system that would generate inertia and could make the functioning of the mechanism unstable.
 
The design is made for a specific type of person, considering their body mass, their foot length, and ankle-knee and knee-hip measurements. It is also necessary to take into account the mass of each part of the leg. Although it is not possible to make this measurement, there are studies that determine percentages based on the total weight of the body.