The analysis model was simplified using ANSYS LS-DYNA. The original CAD and analysis models (see Fig.2 and Fig.3) are shown below.

Fig. 2 - Simplified analysis models created in
ANSYS LS-DYNA

Fig. 3 - Assembled primary parts and linkage system

A wiper generally has three speed levels and it uses a variable motor to maintain the specific speed even if there are substances (e.g. water, snow, dust, etc.) on the windshield. This condition was modelled using PIDCTL in ANSYS LS-DYNA. Traditionally, wiper performance was evaluated with the naked eye based on the condition of the windshield after the use of the wiper. Occasionally, a film of water or water collection patterns may appear (see Fig.4.). Empirically, the major determinants of wiper performance are the achievement of the appropriate angle between the tip of the blade and the windshield, and the pressure distribution of the blade on the windshield, but it is difficult to obtain quantitative data using experimental analysis. Fixed element method (FEM) simulation represents a simple solution for quantitative data analysis in this case. The flow chart of the project is illustrated below (Fig.5).

Fig. 4 - Wiper performance based on windshield condition

Fig. 5 - Analysis flow chart

Wiper blade pressure can be calculated from the positional contact pressure between the tip of the blade and the windshield. However, no method exists in analysis software to make quantitative calculations of pressure for an acute angle at this position. To solve this problem, a separate post-processing code was developed using the following concept (see Fig.6.):

• Step1: For each longitudinal section of the blade, designate the top node, which moves with the blade, as the observation point.
• Step2: At every timestep, the program finds the three nodes of the windshield closest to the blade observation point and uses them to construct a plane equation.
• Step3: The acute angle is determined using the angle between the normal of the plane equation and the straight line formed by the two points (B1-B2) on the central node of the blade.

Fig. 6 - Concept for the calculation of blade pressure at an acute angle

Fig. 7a - Section A: Wiper blade section with yoke / Section B: Wiper blade section without yoke

Fig. 7b - Acute angles calculated from wiping angle (Section A)

Fig. 7c - Acute angles calculated from wiping angle (Section B)

The above steps 1-3 have to be repeated for all sections of the blade over time, a process that was fully automated in the program that was developed.
To verify the success of the program calculations, direct measurements were taken of two of the wiper blade sections (with and without the yoke – see Fig.7) and the results were compared to the program’s; the same results was obtained. The developed program enables the calculation of the pressure distribution and the acute angle based on the wiping angle. The results generated by the developed program for the distribution of the contact pressure and the acute angle by location are shown below (Fig.8).

Wiper performance is optimal when the blade satisfies both the pressure and the acute angle conditions. Therefore, the final performance quality can be calculated by combining the output results (See Fig.9).

Fig. 8a - Normal force (left: opening direction; right: closing direction)

Fig. 8b - Acute angle force (left: opening direction; right: closing direction)

Fig. 9 - Grade of wiper performance quality (left: opening direction right: closing direction

Fig. 11a - User interface of the pre-processing program developed

Fig. 11b - User interface of the post-processing program developed