Mitsuhiro Kamezaki

Primitive static states for intelligent operated-work machines

Advanced operated-work machines, which have been designed for complicated tasks and which have complicated operating systems, requires intelligent systems that can provide the quantitative work analysis needed to determine effective work procedures and that can provide operational and cognitive support for operators. Construction work environments are extremely complicated, however, and this makes state identification, which is a key technology for an intelligent system, difficult. We therefore defined primitive static states (PSS) that are determined using on-off information for the lever inputs and manipulator loads for each part of the grapple and front and that are completely independent of the various environmental conditions and variation in operator skill level that can cause an incorrect work state identification. To confirm the usefulness of PSS, we performed experiments with a demolition task by using our virtual reality simulator. We confirmed that PSS could robustly and accurately identify the work states and that untrained skills could be easily inferred from the results of PSS-based work analysis. We also confirmed in skill-training experiments that advice information based on PSS-based skill analysis greatly improved operators work performance. We thus confirmed that PSS can adequately identify work states and are useful for work analysis and skill improvement.

Operator Support System Based on Primitive Static States in Intelligent Operated Work Machines

Intelligent functions that can autonomously identify the current work states and also provide informational or operational support to their operators are inevitably required for double-front construction machinery (DFCM), which has been developed for complicated tasks. In this study, which focuses on DFCM, we address the need for a new conceptual design of an operator support system. In particular, a state identification method strongly requires high reliability and robustness to address the complexity of the construction work environment and the variety of the operators skill level. We, therefore, define primitive static states (PSS) that are determined using on–off information for the lever inputs and manipulator loads for each part of the grapple and front. We develop an intelligent system that provides a reduction of operational gain to make precise work easier and an indication of an enlarged image of the end-effector from a different viewpoint to assist depth perception based on PSS identification, and evaluate it using our newly developed simulator. Our experimental results show that the operator support system improves the work performance, including decreasing the operational time for completing a task, reducing the mental workload on the operators and the number of error operations.

Development of a dual robotic arm system to evaluate intelligent system for advanced construction machinery

This paper reports a newly developed hydraulic dual robotic arm system to create and evaluate intelligent systems, which support complicated machine operations, for advanced construction machinery. This kind of machine system (test-bed) requires functions to quantify its dynamic characteristics and operational difficulty (influential factors). In particular, construction manipulator nonlinearly changes its dynamics depending on various internal and external factors. To quantify such influential factors, our proposed test-bed is equipped with standard hydromechanical system which includes two manipulators and grapples, and practical sensing system which detects control input, oil pressure, oil temperature, and cylinder stroke data. Using the developed test-bed, fundamental experiments were conducted to clarify hydromechanical system characteristics. Experimental results indicate that the test-bed quantifies its hysteresis, pressure loss, and time delay, and show that variable dynamics complicates intuitive and precise machine operations and external force measurement. This analysis confirms the developed machine system is useful to quantify influential factors for creating intelligent system.

Analysis of individual driving experience in autonomous and human-driven vehicles using a driving simulator

Intelligent vehicles capable of autonomous driving will be commercially available in near future. To formulate a beneficial relationship between driver and vehicle, it is important to analyze how the drivers would react to autonomous vehicles compared to human-driven (conventional) vehicles. In this study, we focused on analyzing individual driving experience in several road conditions for autonomous and conventional vehicles among experienced and novice drivers. We first developed a simplified driving simulator that can connect arbitrary interfaces, create virtual environments consisting of scenarios and events that drivers encounter in real-world driving, and implement fully autonomous driving. We then conducted experiments to clarify differences of driving experiences for autonomous driving between the two groups. The experimental results showed that experienced drivers opt for conventional driving mainly due to the flexibility and driving fun it offers, while novices tend to prefer autonomous driving due to its inherent easiness and safety. An in-depth analysis indicated that drivers preferred to use both the driving methods interchangeably depending on the road and traffic conditions.

Design of four-arm four-crawler disaster response robot OCTOPUS

We developed a four-arm four-crawler advanced disaster response robot called OCTOPUS. Disaster response robots are expected to be capable of both mobility, e.g., entering narrow spaces over very rough unstable ground, and workability, e.g., conducting complex debris-demolition work. However, conventional disaster response robots are specialized in either mobility or workability. Moreover, strategies to independently enhance the capability of crawlers for mobility and arms for workability will increase the robot size and weight. To balance environmental applicability with the mobility and workability, OCTOPUS is equipped with a mutual complementary strategy between its arms and crawlers. The four arms conduct complex tasks while ensuring stabilization when climbing steps. The four crawlers translate rough terrain while avoiding toppling over when conducting demolition work. OCTOPUS is hydraulic driven and teleoperated by two operators. To evaluate the performance of OCTOPUS, we conducted preliminary experiments involving climbing high steps and removing attached objects by using the four arms. The results showed that OCTOPUS completed the two tasks by adequately coordinating its four arms and four crawlers and improvement in operability needs.

A framework of state identification for operational support based on task-phase and attentional-condition identification

This paper proposes a state identification framework to support the complicated dual-arm operations in construction work. The operational support in construction machinery filed requires the compatibility with different types of support and the commonality among various operator skill levels. The proposed framework is therefore organized into two functions: real-time task phase identification and time-series attentional condition identification. The task phase is defined by utilizing the joint load applied according to the environment constraint condition. The attentional condition is defined as one of the internal work-state condition classified by the necessity level of operational support, and is dependent on the vectorial or time-series date selected by the identified task phase. Experiments are conducted using the hydraulic dual arm system to perform transporting and removing tasks. Results show that the number of error contacts, internal force applied, and mental workload is decreased without time-consumption increase. The result confirmed that the proposed framework greatly contribute to improving each operators work performance.

Relative accuracy enhancement system based on internal error range estimation for external force measurement in construction manipulator

This paper proposes a practical framework for measuring the external force applied to a construction manipulator (front load vector) by using a hydraulic sensor. Such a force measurement system requires high accuracy and robustness considering the uncertainty in the construction machinery field, but it inevitably includes measurement errors owing to difficult-to-reduce modeling errors. Our framework thus adopts a relative accuracy improvement strategy without correcting the models for the practicality. It comprises (i) quantifying the internal error range (IER) by using the sum of the maximal measurement errors of static and dynamic friction forces, which change in postural and kinematic conditions, (ii) calculating the error force vector by using IER to select cylinders (sensors) that have less error, and (iii) outputting the front load vector using the cylinders whose error force vector is minimum. Experiments were conducted using an instrumented hydraulic arm. The results indicate that our framework can enhance the relative accuracy of external force measurement independently of various postural and kinematic conditions.

Development of an operation skill-training simulator for double-front work machine

This paper reports a newly developed simulator for operation skill training in Double-Front Construction Machinery (DFCM) that allows novices to virtually experience tough operations repeatedly using DFCM under various conditions, including dangerous congestion. First, we selected several situations targeted where the DFCM needs to be used to provide a high level of operation skills: sorted dismantling for recycling and reusing resources, rescue and recovery work in disaster areas, and building construction. In addition, we developed an operation skill-training simulator that enables novice operators to repeatedly train with the high level of operation skills needed to easily and safely handle the DFCM in even more complicated works. This simulator system has two joysticks (set in front of a monitor) to dependently control the two fronts of the animated DFCM on the monitor. Several modes involving basic construction tasks are provided and the effects of improvement in operability achieved by the training simulator can be verified. Evaluation experiments indicated that repeated training using the simulator successfully decreased the operation time to complete a task and enhanced positioning accuracy in cooperative transportation with the two fronts. The results confirm the effectiveness of the developed simulator.

A Concept for a robot arm with adjustable series clutch actuators and passive gravity compensation for enhanced safety

Passive compliance is useful for robotic arms to ensure their safety. Often springs are used, but they are problematic because they reduce the achievable accelerations and can lead to underdamped oscillations. Torque limiters enhance the safety, but usually the torque limit cannot be adjusted to a desired torque. Electronically adjustable torque limiters, also known as series clutch actuators, have several benefits, especially for robotic arms, but they also have severe limitations. This paper suggests incorporating series clutch actuators into a gravity compensated arm. Consequently, gravity should not limit the isotropically achievable force anymore and in the case of power outage the arm keeps its position. The benefits and limitations of a series clutch actuator in a gravity compensated arm are discussed, and a prototype of such an arm is presented. Commercially available magnetic friction clutches are used. Preliminary experiments demonstrate that the safety can be increased.

Development of a backdrivable magnetorheological hydraulic piston for passive and active linear actuation

A new design of a magnetorheological piston prototype intended for passive or active force control in robotic applications for human robot interaction is introduced. It is based in a novel toroidal array of valves, contained within the piston head, which are used to control the output force of the actuator in order to achieve a high degree of reliability, size efficiency, and safety, by exploiting the material properties of magnetorheological fluids and permalloy metals. This paper describes the main points in the development of the magnetorheological piston prototype, the mathematical modelling of the magnetic circuit, and the results of the experiments conducted using a universal testing machine to evaluate the passive performance of the prototype. Results show the feasibility and performance of the new toroidal magnetic circuit of the magnetorheological hydraulic piston prototype. Improvements in order to be able to test the active performance of the design together with a pump setup are proposed.