Power-assisted System Research Articles

Parameter matchin and optimization for a hydraulic power-assistant system

A hydraulic power-assist system is a hydraulic regeneration system that can significantly improve fuel economy when installed on a conventional bus operating in urban traffic. This paper presents a methodology for matching a new hydraulic power-assist system (HPA) to a conventional bus. The HPA and the conventional bus were modeled using the AMESim environment. The HPA was optimized using a simulation-based orthogonal design method with two indexes, the fuel economy and the acceleration performance. According to the simulation results, the volume of the accumulator was the primary factor affecting fuel economy, and the gear ratio of the transfer case was the primary factor influencing the acceleration performance. As a result, tradeoffs between the two indexes are required for a practical operational scenario. Experimental results demonstrated that the optimal HPA installed on a conventional bus was able to satisfy the acceleration performance requirement of the vehicle and also reduced fuel consumption by 25 percent.

Strategy on Safety Function Implementation: Case Study Involving Risk Assessment and Functional Safety Analysis for a Power Assist System

Power assist systems are expected to bring many benefits in various fields, and some of them have already been introduced in the welfare and manufacturing industries. As power assist systems demand manual contact with a human operator, it is important to prevent hazards that originate from system faults. The objectives of this paper are to introduce a strategy on safety function implementation by means of a case study for a power assist system and to propose an approach for safety function design. This paper describes details of the strategy for Skill-Assist — the power assist system adopted as the experimental platform. First, the safety integrity level (SIL) required for Skill-Assist was determined, following which top-down and bottom-up risk assessments were conducted. A safety-related system (SRS) with a fail-safe fault detection device and dual-channel voting architecture was then constructed based on the risk assessment result. A functional safety analysis was performed for the SRS and we found that the SRS satisfied the required SIL. An experiment on the functionality of the SRS was performed and we verified the safety function for Skill-Assist set by the proposed strategy.

G1500-1-5 柔軟物搬送におけるノッチフィルタの操作支援効果に関する考察(ロボティクス・メカトロニクス部門一般講演(1):操作支援,社会変革を技術で廻す機械工学)

Recently, power assist systems (PASs) have been attracted special interest in industries. However, the operation methods of PASs for light and large scale structures (flexible structures) have not been fully addressed yet. The authors have studied on an assist control method for positioning and vibration reduction in such a problem. Concretely, the human operation input is frequency-shaped by using a notch filter in order to suppress the vibration of flexible structure. In this paper, we investigate how the notch filter generates assistance to human operation in the authors' method. Moreover, the characteristics of human operation when he/she operates the PAS with the authors' method are discussed.

柔軟物の自動搬送から手動位置決め作業までの操作支援法(機械力学,計測,自動制御)

In industrial production lines, there are many operations by not only autonomous machinery as industrial robots but also man-machine cooperative systems as power-assist systems. There are many flexible and large parts because of being lightened, which cause vibration during operation. In such a case, efficient mode switching from machine-oriented operation to human-oriented operation and vibration suppression are important issues. This paper presents an assist control method for task from automated conveyance to manual positioning of a flexible part. This method consists of the smooth mode switching compensator whose control input is continuous at the controll mode switching, and the input shaping compensator which is used to suppress the vibtation of the flexible part. The notch filter with a variable gain is used as the input shaping compensator, which eliminates the vibration frequency component of the flexible part from operating force signal. The effectiveness of the proposed method is verified from standpoints of maneuverability and operating feel. The former is based on the evaluation of the time responses and the success time of the task, and the latter is the subjective evaluation of the operators using questionnaires.

Development of a Compact Magnetorheological Fluid Clutch for Human-Friendly Actuator

There is a strong demand for a human–machine-coexistent machine, e.g., a power-assist system or a computer-aided rehabilitation system, in the context of the super-aging society. In such a human–machine-coexistent system, it is important to guarantee hardware-level safety by utilizing human-friendly actuators. In this study, we have developed a compact magnetorheological fluid clutch (CMRFC) for human-friendly actuators. In this paper, at first, the basic design of the CMRFC and developments of 5- and 40-Nm class devices are explained. Then we discuss experimental results on the basic characteristics of these devices. In the final part, a new magnetorheological fluid that includes nano-sized particles is discussed.

Electrorheological Gel Linear Actuator for Human-Coexistence Robots

Robots manipulated by humans are being aggressively researched and developed. Such robots have requirements such as a large generative force, high-speed response, good controllability, high safety, low friction and backdriveability. We focused on backdriveability and created a prototype for a novel linear actuator with a new structure that includes an electrorheological (ER) gel, which is a recently designed functional material. The device is an all-purpose actuator that satisfies the demands for application in a human-coexistence welfare robot, such as power-assist systems. This paper presents the original plan for the linear actuator, shows the actuator as currently manufactured and presents the basic characteristics of the actuator as investigated experimentally. We obtained larger force from the linear actuator than the initial target. Additionally, the linear actuator shows possibilities of further improvement of the force–weight ratio by an increase of the ER gel structures. With regard to stabilizing the response of the linear actuator, spring elements contributed to its improvement. However, further stabilization remains as a future issue for practical use in human-coexistence robots.

Design and Development of Compact Magnetorheological Fluid Clutch (CMRFC) with Multi-layered Disks and Micro-sized Gaps

There is a strong demand for a human-machine-coexistent machine, e.g. a power-assist system or a computer-aided rehabilitation system, in the context of the super-aging society. In such a human-machine-coexistent system, it is important to guarantee hardware-level safety by utilizing human-friendly actuators. In this paper, we developed two types of compact MR fluid clutches (CMRFC) for human-friendly actuators, which performs about 5Nm torque by applying 1A current and have two different gap-size (50 mm and 100 mm). We tested their static torque. First, we used a conventional MR fluid as a working material of the CMRFCs. Then we used new MRF, which consist of nano-sized (104 nm) Fe particles. According to the experimental results, gap-size affects not only magnetic property but also easiness of filling of MRF (or particles).

103 腕のパワーアシストシステムのインピーダンス制御におけるシステムの安定性と目標値誤差の評価(OS1-1 人に優しい制御技術1,OS1 人に優しい制御技術)

103 腕のパワーアシストシステムのインピーダンス制御におけるシステムの安定性と目標値誤差の評価(OS1-1 人に優しい制御技術1,OS1 人に優しい制御技術)

1A2-G13 マルチポータルヒューマンインタフェース : 操作安定性を考慮した操作力ファジィ推定

1A2-G13 マルチポータルヒューマンインタフェース : 操作安定性を考慮した操作力ファジィ推定

Development of Industry Oriented Power-Assisted System and Comparison with Conventional Machine

So far, we have developed a power-assisted wire suspension system to reduce operators' burden. It has three advantages. First, the structure is simple, and the cost is lower than that of other rigid systems, because the mechanism is based on an overhead crane. Second, it is easy to effect sequence control using this system because the sequence control is based on the velocity control. Finally, this system is expected to supply efficient conveyance by any operator, because operators can move heavy objects directly with two hands. In this paper, we summarize the design and the feature of the power-assisted system, and compare the effectiveness of the proposed power-assisted system with the conventional operation using buttons through experiments involving the measurement of the precision of the positioning and the work time needed to assemble objects.

Weight-Perception-Based Model of Power Assist System for Lifting Objects

This paper deals with the design and control of a power assist system for lifting objects based on weight perception. We considered vertical lifting force (load force) as the desired dynamics for lifting objects with the power assist system. Load force consists of inertial force and gravitational force. We hypothesized that weight perception due to inertial force may differ from perceived weight due to gravitational force for lifting objects with a power assist system. Based on this hypothesis, we designed a 1-degree-of-freedom (DOF) (vertical up-down) power assist system and determined a psychophysical relationship between actual weights and power-assisted weights for lifted objects. We also determined the excess in the load forces that subjects applied when lifting objects with the system. The excessive load force causes problems such as sudden high acceleration of the lifted object, user safety and other concerns while lifting the object, loss of system maneuverability and stability, and possibly fatal accidents. We modified the power-assist control based on the psychophysical relationship and the load force characteristics. Modifying control reduced the excess in load forces and significantly enhanced maneuverability, naturalness, ease of use, stability, and safety. We proposed using the findings to design industrial power assist systems for transporting heavy objects in various industries such as assembly and manufacturing, mining, logistics and transport, construction, disaster management and rescue, and military operations.

Assist Control Method Based on Operating Property for Task from Automated Transfer to Manual Positioning of Flexible Parts

Industrial production lines combine both autonomous machinery such as industrial robots and operator-machine cooperative power-assist systems. There are a lot of flexible and large parts among assembly parts, because of the weight saving. In efficient switching among machine- and operator-oriented operation, vibration suppression is an important issue. This paper presents operator-based assist control for task from automated transfer to manual positioning of flexible parts. This involves a mode-switching compensator whose control input is continuous and an input-shaping compensator that suppresses flexible-parts vibration. The input-shaping compensator using a notch filter eliminates the vibration frequency component from the operating force signal. Filter gain is adjusted online based on operating properties. The effectiveness of our proposal is verified from (i) maneuverability based on time-response evaluation and task-achievement time, and (ii) operational feel subjectively evaluated based on questionnaires.

Integral Sliding Mode Control with Anti-windup Compensation and its Application to a Power Assist System

In this paper we deal with compensation for controller windup due to actuator saturation in the integral sliding mode control. It is shown that the actuator saturation in the integral sliding mode control causes windup problem similar to the so-called integrator windup, which often takes place in linear control systems with integral action. A simple modification for the switching function is presented in order to reduce the discontinuous component of the control input during saturation. This can be seen as a variable switching function. Furthermore, the proposed anti-windup compensation is applied to a power-assisted manipulator with a single degree of freedom. Simulation and experimental results show the effectiveness of the proposed method.

Improving Maneuverability of Power-Assisted Valve for Fire Engines Based on Prediction of Valve Opening Times

In this paper, we report the development of a power-assisted valve for fire engines. In Japan, the number of firefighters is decreasing year by year; therefore, it is important to reduce the amount of labor involved in firefighting. Although the development of an automatic system is possible in strictly technical terms, firefighting regulations in Japan require that the valve be operated by hand. In this study, we aim to develop a power-assisted system that can be controlled in accordance with the intent of the operator. First, we confirm a relationship between the impedance parameters and valve opening time. From this relationship, we propose a method for predicting the valve opening time based on the initial value of the operation torque. Evaluating this method, we found that the average operation torque and average tracking error are improved by a factor of two. Second, we reduce prediction error by using a real-time prediction method. While a prediction method based on initial torque can adjust parameters only once, the proposed real-time prediction method can update parameters continuously. As a result, the evaluation score of the method improved from 0.46 to 0.29, and average prediction error was improved from 172 ms to 105 ms.

Development of an Upper Limb Power Assist System Using Pneumatic Actuators for Farming Lift-up Motion

A power assist system has lately attracted considerable attention to lifting-up an object without low back pain. We have been developing power assist systems with pneumatic actuators for the elbow and shoulder to farming support of lifting-up a bag of rice weighing 30kg. This paper describes the mechanism and control method of this power assist system. The pneumatic rotary actuator supports shoulder motion, and the air cylinder supports elbow motion. In this control method, the surface electromyogram(EMG) signals are used as input information of the controller. The joint support torques of human are calculated based on the antigravity term of necessary joint torques, which are estimated on the dynamics of a human approximated link model. The experimental results show the effectiveness of the proposed mechanism and control method of the power assist system.

A32 筋音図を用いた装着型下肢運動支援システム(生体・センシング)

A32 筋音図を用いた装着型下肢運動支援システム(生体・センシング)

1P1-C21 パラレル機構を有する力覚および変位検出インターフェイスを用いたパワーアシストシステムの開発

1P1-C21 パラレル機構を有する力覚および変位検出インターフェイスを用いたパワーアシストシステムの開発

Development of power assisted wire suspension system and its application to mould setting

In this paper, a power assisted wire suspension system which supports the setting of a mould is presented. The purpose of this system is to eliminate a worker's burden and to assist the skill for unskilled workers. This system measures the swing angle of the rope and the fluctuation of the mould's weight caused by operator's force, and it moves the AC servomotors of both the horizontal and vertical axes work in accordance with the detected swing angle and the force respectively. The effectiveness of this power assisted system is confirmed by experiments for setting of the mould.

1A1-D08 位置ベースインピーダンス制御を用いたモード切り換え制御手法(人間機械協調)

In automobile production lines, there are many operations by not only autonomous machinery as industrial robots but also man-machine cooperative systems as power-assist systems. In this case, efficient mode switching from machine-oriented operation to human-oriented operation is important. This paper presents a new mode switching control method from the automatic mode to the manual mode on the basis of position based impedance control. This method proposes the smooth mode switching compensator whose control input is continuous at the switching time. The effectiveness of the proposed method is verified experimentally.

2P2-F03 差動歯車を用いた上肢作業補助機の開発とパワーアシストユニットシステムへの展開(医療・福祉ロボティクス・メカトロニクス)

2P2-F03 差動歯車を用いた上肢作業補助機の開発とパワーアシストユニットシステムへの展開(医療・福祉ロボティクス・メカトロニクス)