This paper presents a method to drive a hard disk drive (HDD) spindle motor at high speed with large starting torque by utilizing a bipolar-starting and unipolar-running algorithm. It proposes a novel inverter circuit to switch from bipolar to unipolar drive, or vice versa. It also develops a digital signal processor (DSP)-based brushless dc (BLDC) motor controller not only to drive the BLDC motor with the bipolar or unipolar method, but also to switch from one method to the other at any speed. Torque-speed-current curves of a BLDC motor driven by bipolar or unipolar method are investigated experimentally, and the effectiveness of the proposed method is also verified by using the developed controller experimentally. This research shows that the proposed method starts the BLDC motor with large starting torque that can be obtained by a bipolar drive, and it runs the BLDC motor at high speed that can be driven by unipolar drive.

As the market penetration rate (MPR) of autonomous vehicles increases, it is expected that the safety of mixed traffic situations will change due to interactions between vehicles. A proactive safety analysis of mixed traffic situations is needed for future intelligent transportation systems; thus, it is necessary to determine the driving safety evaluation indicators that have a significant impact on identifying hazardous sections of actual roads by each MPR. The purpose of this study is to simulate autonomous vehicle behavior by analyzing real-world autonomous vehicle data and to derive a promising integrated driving safety evaluation index for mixed traffic. Autonomous vehicle driving data from an autonomous mobility testbed in Seoul were collected and analyzed to assess autonomous vehicle behavior in VISSIM. The simulation environment was established to match the real road environment. Decision tree (DT) analysis was adopted to derive the indicators influencing the classification of hazardous sections of real roads by MPR. The vehicle–vehicle interaction indicators used to evaluate driving safety were applied as the input variables of the DT, and the classification of real-world hazardous road sections was the output variable. An integrated evaluation index was developed using the promising evaluation indicators and information gains derived for each MPR. The most hazardous section and the factors affecting the driving safety of the section based on the integrated evaluation index for each MPR were then presented. The results of this study can be utilized to proactively identify hazardous road sections in the real world through simulations of mixed traffic conditions.

In this study, a novel methodology is proposed to evaluate automated driving safety in mixed traffic environments, including autonomous vehicles (AVs) and manually driven vehicles (MVs). An open-source AV dataset obtained from a real-world autonomous mobility testbed in Korea was used for methodology development and evaluations. The driving behavior was evaluated using well-known promising indicators, including the standard deviation of the vehicle speed, acceleration noise, standard deviation of the lane offset, time to collision (TTC), and deceleration to avoid a crash (DRAC). Min-max and max-min normalization was performed to unify the units of the evaluation indicators. The importance of each driving safety indicator was derived through the Analytical Hierarchy Process (AHP) performed by traffic experts, and the weights were estimated based on the average of the collected importance. The normalized indicators were integrated to obtain the automated driving risk score (ADRS), which is regarded as a measure of automated driving safety. The automated driving safety degraded considerably in road sections where right turns were made at intersections and that had a bus stop. Hazardous driving events of AVs were visualized, which is useful for monitoring mixed traffic safety and developing effective countermeasures for proactive road safety management.

The comprehensive evaluation of factors that increase the difficulty of autonomous driving in various complex traffic situations and diverse roadway geometries within living lab environments is of great interest, particularly in developing sustainable urban mobility systems. This study introduces a novel methodology for assessing autonomous driving vulnerabilities and identifying urban traffic segments susceptible to autonomous driving risks in mixed traffic situations where autonomous and manual vehicles coexist. A microscopic traffic simulation network that realistically represents conditions in a living lab demonstration area was used, and twelve safety indicators capturing longitudinal safety and vehicle interaction dynamics were employed to compute an integrated risk score (IRS). The promising weighting of each indicator was derived through decision tree method calibrated with real-world traffic accident data, allowing precise localization of vulnerability hotspots for autonomous driving. The analysis results indicate that an IRS-based hotspot was identified at an unsignalized intersection, with an IRS value of 0.845. In addition, analytical results were examined comprehensively from multiple perspectives to develop actionable improvement strategies that contribute to long-term sustainability, encompassing roadway and traffic facility enhancements, provision of infrastructure guidance information, autonomous vehicle route planning, and enforcement measures. Furthermore, this study categorized and analyzed the characteristics of high-risk road sections with similar geometric features to systematically derive effective traffic safety countermeasures. This research offers a systematic, practical framework for safety evaluation in autonomous driving living labs, delivering actionable guidelines to support infrastructure planning and validate sustainable autonomous mobility.