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Hiroshi Fujimoto

Publications and source records attributed to Hiroshi Fujimoto.

7 recordsLinked to original sources

Dodging the Moose: Experimental Insights in Real-Life Automated Collision Avoidance

The sudden appearance of a static obstacle on the road, i.e. the moose test, is a well-known emergency scenario in collision avoidance for automated driving. Model Predictive Control (MPC) has long been employed for planning and control of automated vehicles in the state of the art. However, real-time implementation of automated collision avoidance in emergency scenarios such as the moose test remains unaddressed due to the high computational demand of MPC for evasive action in such hazardous scenarios. This paper offers new insights into real-time collision avoidance via the experimental imple- mentation of MPC for motion planning after a sudden and unexpected appearance of a static obstacle. As the state-of-the-art nonlinear MPC shows limited capability to provide an acceptable solution in real-time, we propose a human-like feed-forward planner to assist when the MPC optimization problem is either infeasible or unable to find a suitable solution due to the poor quality of its initial guess. We introduce the concept of maximum steering maneuver to design the feed-forward planner and mimic a human-like reaction after detecting the static obstacle on the road. Real-life experiments are conducted across various speeds and level of emergency using FPEV2-Kanon electric vehicle. Moreover, we demonstrate the effectiveness of our planning strategy via comparison with the state-of- the-art MPC motion planner.

eess.SY

Model-based Development for Autonomous Driving Software Considering Parallelization

In recent years, autonomous vehicles have attracted attention as one of the solutions to various social problems. However, autonomous driving software requires real-time performance as it considers a variety of functions and complex environments. Therefore, this paper proposes a parallelization method for autonomous driving software using the Model-Based Development (MBD) process. The proposed method extends the existing Model-Based Parallelizer (MBP) method to facilitate the implementation of complex processing. As a result, execution time was reduced. The evaluation results demonstrate that the proposed method is suitable for the development of autonomous driving software, particularly in achieving real-time performance.

cs.SE

Parallelized Code Generation from Simulink Models for Event-driven and Timer-driven ROS 2 Nodes

In recent years, the complexity and scale of embedded systems, especially in the rapidly developing field of autonomous driving systems, have increased significantly. This has led to the adoption of software and hardware approaches such as Robot Operating System (ROS) 2 and multi-core processors. Traditional manual program parallelization faces challenges, including maintaining data integrity and avoiding concurrency issues such as deadlocks. While model-based development (MBD) automates this process, it encounters difficulties with the integration of modern frameworks such as ROS 2 in multi-input scenarios. This paper proposes an MBD framework to overcome these issues, categorizing ROS 2-compatible Simulink models into event-driven and timer-driven types for targeted parallelization. As a result, it extends the conventional parallelization by MBD and supports parallelized code generation for ROS 2-based models with multiple inputs. The evaluation results show that after applying parallelization with the proposed framework, all patterns show a reduction in execution time, confirming the effectiveness of parallelization.

cs.SE

Enhancing In-vehicle Multiple Object Tracking Systems with Embeddable Ising Machines

A cognitive function of tracking multiple objects, needed in autonomous mobile vehicles, comprises object detection and their temporal association. While great progress owing to machine learning has been recently seen for elaborating the similarity matrix between the objects that have been recognized and the objects detected in a current video frame, less for the assignment problem that finally determines the temporal association, which is a combinatorial optimization problem. Here we show an in-vehicle multiple object tracking system with a flexible assignment function for tracking through multiple long-term occlusion events. To solve the flexible assignment problem formulated as a nondeterministic polynomial time-hard problem, the system relies on an embeddable Ising machine based on a quantum-inspired algorithm called simulated bifurcation. Using a vehicle-mountable computing platform, we demonstrate a realtime system-wide throughput (23 frames per second on average) with the enhanced functionality.

cs.CV

Test Bench Study on Attitude Estimation in Ground Effect Region Based on Motor Current for In-Flight Inductive Power Transfer of Drones

To overcome the short flight duration of drones, research on in-flight inductive power transfer has been recognized as an essential solution. Thus, it is important to accurately estimate and control the attitude of the drones which operate close to the charging surface. To this end, this paper proposes an attitude estimation method based solely on the motor current for precision flight control in the ground effect region. The model for the estimation is derived based on the motor equation when it rotates at a constant rotational speed. The proposed method is verified on the simulations and experiments. It allows simultaneous estimation of altitude and pitch angle with the accuracy of 0.30$\hspace{0.5mm}$m and 0.04 rad, respectively. The minimum transmission efficiency of the in-flight power transfer system based on the proposed estimation is calculated as 95.3 %, which is sufficient for the efficient system.

cs.RO

Proposal on Model Based Current Overshoot Suppression of Receiver Side Coil in Drone Wireless Power Transfer System

This paper proposes a model-based control method in the wireless power transfer (WPT) system by operating a semi-bridgeless active rectifier (SBAR) to suppress the secondary coil current overshoot. By damping the current overshoot, it is possible to reduce the rectifier's rated current and decrease the rectifier's size, which is beneficial for the lightweight-oriented system such as drones. In the control method, an inverse of the plant model is used to calculate the reference input to the system. The current overshoot is reduced by operating the SBAR under the duty ratio calculated from the model. To confirm the performance of the proposed method, the simulation and the experiment using the WPT prototype are conducted. The experimental results show that the proposed method can suppress the secondary coil current overshoot. The results suggest it is possible to realize the lighter secondary system by applying the proposed method.

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Backlash Identification in Two-Mass Systems by Delayed Relay Feedback

Backlash, also known as mechanical play, is a piecewise differentiable nonlinearity which exists in several actuated systems, comprising, e.g., rack-and-pinion drives, shaft couplings, toothed gears, and other machine elements. Generally, the backlash is nested between the moving parts of a complex dynamic system, which handicaps its proper detection and identification. A classical example is the two-mass system which can approximate numerous mechanisms connected by a shaft (or link) with relatively high stiffness and backlash in series. Information about the presence and extent of the backlash is seldom exactly known and is rather conditional upon factors such as wear, fatigue and incipient failures in the components. This paper proposes a novel backlash identification method using one-side sensing of a two-mass system. The method is based on the delayed relay operator in feedback that allows stable and controllable limit cycles to be induced and operated within the (unknown) backlash gap. The system model, with structural transformations required for the one-side backlash measurements, is given, along with the analysis of the delayed relay in velocity feedback. Experimental evaluations are shown for a two-inertia motor bench that has coupling with backlash gap of about one degree.

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