Three-dimensional motion of the pelvis during human walking

The knowledge of the pelvis kinematics plays an important role in the equilibrium control during walking. The previous research technique on the pelvis locomotion is impractical in some fields such as clinic practice. This paper illustrates a new method based on a treadmill and three precise displacement-sensors. 20 healthy young adults of both sexes are instructed to naturally walk on a treadmill at different speeds. A model is presented to calculate the medial-lateral and vertical displacements of the pelvis during any able-bodied walking. The presented data and curves indicate that the medial-lateral and vertical displacements of the pelvis are cyclical and roughly sinusoidal during normal walking. The frequency is equal to the gait frequency in medial-lateral direction, and twice as much as that in vertical direction. In addition, the research subject's height and walking velocity have an effect on the amplitude of displacement of the pelvis. The presented data define the normal movement behavior of the pelvis during walking. As a result, it produces a standard to compare normal gait with pathological gait. The presented model may be useful in the position control of a patient's trunk for rehabilitation robot and the clinical evaluation of rehabilitation effect. In the field of humanoid robot, it is a necessary parameter for the path planning.