scholarly journals Walking Strategies and Performance Evaluation for Human-Exoskeleton Systems under Admittance Control

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4346 ◽  
Author(s):  
Chiawei Liang ◽  
Tesheng Hsiao
Keyword(s):  
Performance Evaluation ◽  
Energy Consumption ◽  
Reaction Force ◽  
Sufficient Conditions ◽  
Estimation Algorithm ◽  
Walking Distance ◽  
Control Law ◽  
Admittance Control ◽  
Communication Module ◽  
And Performance

Lower-limb exoskeletons as walking assistive devices have been intensively investigated in recent decades. In these studies, intention detection and performance evaluation are important topics. In our previous studies, we proposed a disturbance observer (DOB)-based torque estimation algorithm and an admittance control law to shape the admittance of the human-exoskeleton system (HES) and comply with the user’s walking intention. These algorithms have been experimentally verified under the condition of no ground reaction force (GRF) in our previous studies. In this paper, we devised and integrated with the exoskeleton control system a sensing and communication module on each foot to measure and compensate for GRF. Rigorous theoretical analysis was performed and the sufficient conditions for the robust stability of the closed-loop system were derived. Then, we conducted level ground assistive walking repeatedly with different test subjects and exhaustive combinations of admittance parameters. In addition, we proposed two tractable and physically insightful performance indices called normalized energy consumption index (NECI) and walking distance in a fixed period of time to quantitatively evaluate the performance for different admittance parameters. We also compared the energy consumption for users walking with and without the exoskeleton. The results show that the proposed admittance control law reduces the energy consumption of the user during level ground walking.

scholarly journals Modeling of Duty-Cycled MAC Protocols for Heterogeneous WSN with Priorities

Electronics ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 467 ◽  
Author(s):  
Canek Portillo ◽  
Jorge Martinez-Bauset ◽  
Vicent Pla ◽  
Vicente Casares-Giner
Keyword(s):  
Performance Evaluation ◽  
Energy Consumption ◽  
Average Energy ◽  
Packet Delay ◽  
Evaluation Study ◽  
Duty Cycling ◽  
Quantitative Evidence ◽  
And Performance ◽  
Save Energy ◽  
Average Energy Consumption

Wireless Sensor Networks (WSN) have experienced an important revitalization, particularly with the arrival of Internet of Things applications. In a general sense, a WSN can be composed of different classes of nodes, having different characteristics or requirements (heterogeneity). Duty-cycling is a popular technique used in WSN, that allows nodes to sleep and wake up periodically in order to save energy. We believe that the modeling and performance evaluation of heterogeneous WSN with priorities operating in duty-cycling, being of capital importance for their correct design and successful deployment, have not been sufficiently explored. The present work presents a performance evaluation study of a WSN with these features. For a scenario with two classes of nodes composing the network, each with a different channel access priority, an approximate analytical model is developed with a pair of two-dimensional discrete-time Markov chains. Note that the same modeling approach can be used to analyze networks with a larger number of classes. Performance parameters such as average packet delay, throughput and average energy consumption are obtained. Analytical results are validated by simulation, showing accurate results. Furthermore, a new procedure to determine the energy consumption of nodes is proposed that significantly improves the accuracy of previous proposals. We provide quantitative evidence showing that the energy consumption accuracy improvement can be up to two orders of magnitude.

scholarly journals Lessons Learned on the Application of Vibration Absorbers for Enhanced Cannon Stabilization

2001 ◽  
Vol 8 (3-4) ◽  
pp. 131-139 ◽  
Author(s):  
Eric Kathe
Keyword(s):  
Performance Evaluation ◽  
Structural Modification ◽  
Digital Signal ◽  
Field Testing ◽  
Lessons Learned ◽  
External Control ◽  
Control Law ◽  
Vibration Absorbers ◽  
Ideal Behavior ◽  
And Performance

This paper will summarize the successful application of muzzle-end vibration absorbers to reduce cannon vibration. This technology constitutes a weapons stabilization approach that focuses on passive mechanical structural modification of the cannon, rather than relying upon an external control law to actively cancel vibrations. Challenges encountered during field testing, non-ideal behavior, and performance evaluation using digital signal processing will be highlighted.

A Stochastic Regulator for Integrated Communication and Control Systems: Part I—Formulation of Control Law

1991 ◽  
Vol 113 (4) ◽  
pp. 604-611 ◽  
Author(s):  
Luen-Woei Liou ◽  
Asok Ray
Keyword(s):  
Performance Evaluation ◽  
Control Systems ◽  
Dynamic Performance ◽  
State Feedback Control ◽  
Control Law ◽  
Spatially Distributed ◽  
Integrated Communication ◽  
Finite Time Horizon ◽  
And Performance ◽  
And Control

Integrated Communication and Control Systems (ICCS), recently introduced and analyzed in a series of papers [1–7], are applicable to complex dynamical processes like advanced aircraft, spacecraft, automotive, and manufacturing processes. Time-division-multiplexed computer networks are employed in ICCS for exchange of information between spatially distributed plant components as well as for coordination of the diverse control and decision-making functions. Unfortunately, an ICCS network introduces randomly varying, distributed delays within the feedback loops in addition to the digital sampling and data processing delays. These network-induced delays degrade the system dynamic performance, and are a source of potential instability. This two-part paper presents the synthesis and performance evaluation of a stochastic optimal control law for ICCS. In this paper, which is the first of two parts, a state feedback control law for ICCS has been formulated by using the dynamic programming and optimality principle on a finite-time horizon. The control law is derived on the basis of a stochastic model of the plant which is augmented in state space to take into account the effects of randomly varying delays in the feedback loop. The second part [8] presents numerical analysis of the control law and its performance evaluation by simulation of the flight dynamic model of an advanced aircraft.

scholarly journals Design, development and performance evaluation of small-scale fodder chopping machine for farmers

2021 ◽  
Author(s):  
Jannatul Ferdows Nipa ◽  
Md. Hasan Tarek Mondal ◽  
Md Atikul Islam
Keyword(s):  
Performance Evaluation ◽  
Energy Consumption ◽  
Small Scale ◽  
Design Development ◽  
Machine Performance ◽  
Machine Productivity ◽  
And Performance ◽  
One Year ◽  
Break Even Point ◽  
The Cost

A straw chopper is a mechanical device used to uniformly chop fodder into small pieces to mix it together with other grass and then feed it to livestock. The objective of this research was to design and develop an animal fodder chopping machine to be utilised by dairy farmers within their purchase range. The drawing of these machine parts was undertaken in AutoCAD software and the construction was performed in a local workshop. After development of this machine, performance tests were carried out on a farm. The chopping machine tests were carried out with commonly grown fodder (namely: straw, grass, and maize) in Bangladesh. The performance evaluation of the developed machine was carried out in terms of the chopping efficiency, machine productivity, and energy consumption. The economic analysis of the straw chopping machine was assessed by indicating the cost effectiveness to the poor farmers. Analysis of the data in regard to chopping efficiency and machine productivity varied from 93 to 96% and from 192 to 600 kg×h<sup>–1</sup>, respectively. The energy consumption during the chopping process ranged between 0.0025 and 0.01 kWh for the different types of fodder. The break-even point of the fodder chopping machine was 3 793 kg of cut straw and the payback period was within one year depending on the use.

scholarly journals Interference-aware multipath routing for WSNs: overview and performance evaluation

2018 ◽  
Vol 16 (1/2) ◽  
pp. 59-80 ◽  
Author(s):  
Moufida Maimour
Keyword(s):  
Wireless Sensor Networks ◽  
Performance Evaluation ◽  
Energy Consumption ◽  
Sensor Networks ◽  
Performance Metrics ◽  
Multipath Routing ◽  
Wireless Sensor ◽  
Iterative Approach ◽  
Success Ratio ◽  
And Performance

Multipath routing holds a great potential to provide sufficient bandwidth to a plethora of applications in wireless sensor networks. In this paper, we consider the problem of interference that can significantly affect the expected performances. We focus on the performance evaluation of the iterative paths discovery approach as opposed to the traditional concurrent multipath routing. Five different variants of multipath protocols are simulated and evaluated using different performance metrics. We mainly show that the iterative approach allows better performances when used jointly with an interference-aware metric or when an interference-zone marking strategy is employed. This latter appears to exhibit the best performances in terms of success ratio, achieved throughput, control messages overhead as well as energy consumption.

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