This paper proposes an effective design method of brake-force distribution focusing on braking motion and pitch angle using developing model and simulation model-based optimization. First, we make the model of pitch motion and braking motion. Next, we introduce a virtual link connecting with these motions. In this paper, the angle of the link is constant. So, the model integrating these motions is under developing. When we try to optimize the brake force distribution using the developing model,

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... the validity of the results is ensured by the model verification of the energy conservation law. We use simultaneous perturbation stochastic approximation (SPSA) because the number of calculating cost function is less than usual gradient method via finite difference approximation. We apply SPSA to simulation model-based optimization and discuss suitable constraints for SPSA based design. In addition, we discuss how to adjust the gradient of SPSA such that values of brake force distribution satisfy the design range in the update process. Consequently, the proposed design method achieves step-by-step optimization of specifications in vehicle.