Test Technologies Contributing to Electrification - 2. Driving Simulator Test Technologies for Establishing Unique Performances of Electric VehiclesFig. 3 Control system configurationTable 1: Pure delayTable 2 Transmission characteristics2.2 Motion cueing developmentFig. 4 Signal control The pure delay, time constant, and frequency characteristics of each step response are measured following the change in motion system control. The configuration of the DS control system is illustrated in Fig. 3. Signals are transmitted to the motion system within 1 ms using a real-time simulator. The characteristics are measured after the signals are sent from the PC in the real-time simulator until the acceleration is transmitted to the cockpit floor in the hexapod.The pure delay from the start of the motion system until it is transmitted to the cockpit floor is listed in Table 1. The largest pure delay is for the turntable, which is a delay of 22 ms more than that for the parallel rails. Each transmission characteristic at 0.3 Hz is listed in Table 2. The transmission characteristics of the hexapods are worse than those of the others because the dome is structurally supported by six cylinders, which makes the inertial load less advantageous. These results, which indicate that only roll and pitch are delayed when signals are input simultaneously, suggest that parameters to match the area to be evaluated on the motion system cueing side must be set.Significant discomfort can be caused by a small change in the DS when driving experience is prioritized. Motion cueing is developed using the measured results of the transmission characteristics of the system to improve the sensory motion experienced by people. Developments in two aspects̶the acceleration characteristics in the fine steering range and the roll motion of the upper structure̶ observed in the comments of evaluation drivers are discussed below.The response in the DS vehicle motion simulation may be better than when driving an actual vehicle because of the absence of vehicle stiffness or mechanical delay caused by backlash, which can lead to discomfort in some cases. In an actual vehicle, the steering angle is derived from the operating force of the steering wheel based on the action and reaction forces. However, in the DS, the steering angle is used for the simulation instead of the operating force. The response delay is expected to be small because the steering angle is forcibly generated regardless of the balance of forces. Although a solution can be provided by an analysis that simulates the relationship between the steering force and steering angle, it is difficult to calculate it in real time with the current technology. Thus, a pseudo-rising delay is added to motion cueing to improve sensory motion. An example of such a control is presented in Fig. 4. The rise is moderately delayed with respect to the input, and the output is constant when the change is constant. Given this approach, control is changed for each signal sent to each of the devices and complied with such that the timing of the acceleration felt by people is consistent.The center of rotation of the vehicle and that of the yaw are different in this system because the seat position of the driver is centered between the hexapod and yaw table in the DS (Fig. 5). Thus, the coordinates of the feeling of acceleration are transformed by the amount based on the difference between the positions of the center of rotation and center of gravity of the vehicle. DSs, which are referred to as racing simulators, often have a system where the seat of the driver is tilted or the center of rotation is set near the abdominal area. In this DS, the roll and pitch are controlled with the rotation center positioned near the abdomen of the driver. 40
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