NISSAN_TECHNICAL_REVIEW_89 (2023)

77/111

Technical Awards : 2021 JSAE Award The Outstanding Technical Paper Award - An Approach to Exploring Vehicle Motion to Enhance Ride Quality of PassengerTable.2 Variables and input functions of vehicle modelFig.2　 Two track and body motion vehicle model conforms to equation (2): Refer to author’s previous research(7)NISSAN TECHNICAL REVIEW No.88 (2022)3. Expansion to passenger ride quality evaluation3.1 Passenger body behavior modelingTable.3　Variables and parameters of passenger modelFig.3　 Passenger seating point confi guration: Passenger upper body (including head) is simplifi ed to a single inverted pendulum, then affected with vehicle motion.the vehicle dynamics and state variables. The coordinate system is based on the unsprung position. For the tire characteristics, the response characteristics using the relaxation length were added to the simplifi ed Magic Formula. Refer to the previous research of the authors(7) for details regarding the vehicle model using equation (2).Using the inverse vehicle dynamics analysis described thus is discussed. First, the passenger body model must be placed inside the vehicle body model. When doing so, passenger modeling is conducted using the form of equation (2), as in the case of the vehicle model.far, passenger ride quality enhancement Next, to deal with the ride quality in motion design, a value related to the passenger perception of the vehicle . For motion needs to be provided as a state variable example, the vestibular organ recognizes the translational acceleration and angular velocity. Because, as shown in equation (1), acceleration is not a state variable but is of the state variable, rather the differential acceleration cannot be incorporated into the stage cost function when creating the motion design policy. Thus, a method of converting acceleration into a state variable is required.The abovementioned considerations suggest that two issues need to be addressed to apply the inverse vehicle dynamics analysis to passenger ride quality. The resolution of these issues is discussed in the subsequent section.The passenger body motion model was created while observing the restriction of expressing the state variables, as shown in equation (2). If the inertia force of the passenger motion acts on the vehicle, it will not be possible to make expressions using the state variables of the vehicle and passenger. Therefore, only the passive motion due to the inertia force of the vehicle motion is considered, and a model for the motion of the upper body in the lateral direction (roll), without separating the head portion, is proposed.As the fi rst step, the inertia force of the vehicle motion, which is applied to the passenger, is expressed. The passenger seating point in the fi xed coordinate system of the vehicle body as well as the rigid upper body model that has a pivot at that point are presented at the left and center of Fig. 3; the variables and constants that are related to the passenger model described below are listed in Table 3. Owing to the vehicle motion, the three-axis translational acceleration shown in equation (3) is applied to this pivot (terms that have little effect are omitted):In the next step, the force acting on the center of gravity (CG) of the upper body is expressed. To this end, it is necessary to derive the acceleration at the CG of the upper body. Here, the acceleration is given by the second-order differentiation of the upper body CG position (pivot point + effect of upper body roll posture angle), which is expressed using the coordinate system based on the ground. The force acting in the lateral and vertical directions, as shown on the right side of Fig. 3, are approximated as the acceleration by multiplying the 72111