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Vehicle door closure systems often include self-balancing double pendulum mechanisms. For example, the counterweight in the outside handle assembly is used to reduce handle motion under inertia loadings occurring during crash events. The system is configured in such a way that the inertia forces developed during a crash are applying opposite moments to each of the pendulums (i.e., to the handle and the counterweight). Investigation of crash impact induced oscillatory response of such mechanisms is presented in this paper. A comprehensive dynamic model is developed that captures all essential characteristics of the double pendulum mechanism. An important aspect of the model is its discontinuous nature due to potential impacts between both pendulums and between one of the pendulums and the base part. Analytical conditions of self-balancing of the double pendulum system are formulated and used to provide an insight into the principles of self balancing.

The governments of many countries have established regulations that address the issue of vehicle door safety during crash events. Depending on the regulation or specification, analytical tools may be acceptable for verifying the crashworthiness of a latching system. In those instances where actual test crashes are required for verification, analytical methods can still be used to help predict the outcome of a crash test. Two relevant analytical approaches for multibody dynamics computation are discussed in the paper. One is related to monitoring the effects of constant 30G inertia loading in all directions (spherical analysis) and another addresses inertia pulse loading of specified G levels in certain directions. In some crash situations, the latch system compliance with the regulations may be insufficient to prevent door release. To secure the door in the latched position additional safety devices can be deployed in various locations of the door latch system.