scholarly journals Event-Based, Intermittent, Discrete Adaptive Control for Speed Regulation of Artificial Legs

Actuators ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 264
Author(s):  
Salvador Echeveste ◽  
Ernesto Hernandez-Hinojosa ◽  
Pranav A. Bhounsule
Keyword(s):  
Legged Robots ◽  
Model Parameters ◽  
Velocity Control ◽  
Set Point ◽  
Turn On ◽  
Speed Regulation ◽  
Mass Uncertainty ◽  
Trajectory Following ◽  
Event Based ◽  
Discrete Controller

For artificial legs that are used in legged robots, exoskeletons, and prostheses, it suffices to achieve velocity regulation at a few key instants of swing rather than tight trajectory tracking. Here, we advertise an event-based, intermittent, discrete controller to enable set-point regulation for problems that are traditionally posed as trajectory following. We measure the system state at prior-chosen instants known as events (e.g., vertically downward position), and we turn on the controller intermittently based on the regulation errors at the set point. The controller is truly discrete, as these measurements and controls occur at the time scale of the system to be controlled. To enable set-point regulation in the presence of uncertainty, we use the errors to tune the model parameters. We demonstrate the method in the velocity control of an artificial leg, a simple pendulum, with up to 50% mass uncertainty. Starting with a 100% regulation error, we achieve velocity regulation of up to 10% in about five swings with only one measurement per swing.

Wideband modeling and transient analysis of sub-module in modular multilevel converter

2017 ◽  
Vol 36 (6) ◽  
pp. 1792-1805 ◽  
Author(s):  
Lei Qi ◽  
Zhiyuan Shen ◽  
Jianjian Gao ◽  
Guoliang Zhao ◽  
Xiang Cui ◽  
...  
Keyword(s):  
Dynamic Testing ◽  
Extraction Procedure ◽  
Model Parameters ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Content Type ◽  
Insulated Gate Bipolar Transistor ◽  
Module Design ◽  
Turn On ◽  
Module Test

Purpose This paper aims to establish the wideband model of a sub-module in a modular multilevel converter (MMC) and analyze the switch transients of the sub-module. Design/methodology/approach The paper builds an MMC sub-module test circuit and conducts dynamic tests both with and without the bypass thyristor. Then, it builds the wideband model of the MMC sub-module and extracts the model parameters. Finally, based on the wideband model, it simulates the switch transients and analyzes the oscillation mechanism. Findings The dynamic testing shows the bypass thyristor will add oscillations during switch transients, especially during the turn-on process. The thyristor acts like a small capacitor and reduces the total capacitor in the turn-on circuit loop, thus causing under-damped oscillations. Originality/value This paper found that the bypass thyristor will influence the MMC sub-module switch transients under certain circumstances. This paper proposes a partial inductance extraction procedure for the MMC sub-module and builds a wideband model of the sub-module. The wideband model is used to analyze and explain the switch transients, and can be further used for insulated gate bipolar transistor switch oscillation inhibition and sub-module design optimization.

Robustness Analysis of a Simple and Augmented Proportional Plus Derivative Controller in Trajectory Following Robots Using the Floquet Theory

2018 ◽  
Vol 13 (7) ◽  
Author(s):  
B. Sandeep Reddy ◽  
Ashitava Ghosal
Keyword(s):  
Numerical Simulation ◽  
Degrees Of Freedom ◽  
Floquet Theory ◽  
Robustness Analysis ◽  
Periodic Trajectory ◽  
Model Parameters ◽  
Asymptotically Stable ◽  
Pd Controller ◽  
Simulation Results ◽  
Trajectory Following

This paper deals with the issue of robustness in control of robots using the proportional plus derivative (PD) controller and the augmented PD controller. In the literature, a variety of PD and model-based controllers for multilink serial manipulator have been claimed to be asymptotically stable for trajectory tracking, in the sense of Lyapunov, as long as the controller gains are positive. In this paper, we first establish that for simple PD controllers, the criteria of positive controller gains are insufficient to establish asymptotic stability, and second that for the augmented PD controller the criteria of positive controller gains are valid only when there is no uncertainty in the model parameters. We show both these results for a simple planar two-degrees-of-freedom (2DOFs) robot with two rotary (R) joints, following a desired periodic trajectory, using the Floquet theory. We provide numerical simulation results which conclusively demonstrate the same.

Plans and The Structure of Target Acquisition Behavior

1981 ◽  
Vol 25 (1) ◽  
pp. 571-575
Author(s):  
R. A. Miller ◽  
R. J. Jagacinski ◽  
R. B. Nalavade ◽  
W. W. Johnson
Keyword(s):  
Closed Loop ◽  
Position Control ◽  
Open Loop ◽  
General Strategy ◽  
Velocity Control ◽  
Additional Time ◽  
First Order ◽  
Oscilloscope Screen ◽  
Activity Sequence ◽  
Event Based

Subjects manipulated a position control stick with one hand and a velocity control stick with the other hand in order to capture a moving target displayed on an oscilloscope screen. The two control sticks were additively coupled. In order to understand the coordination of the two control sticks, event-based first-order markov “activity sequence generators” were constructed for individual subjects. These discrete probabilistic structures are closely related to each subject's overall plan or general strategy for the capture task. Striking individual differences and strategic errors in performance were revealed. When combined with additional time-conditioned (open-loop) and error-conditioned (closed-loop) details, the activity sequence generators provide a basis for a hierarchic description of this perceptual-motor skill.

scholarly journals Effects of ionic strength on the regulation of Na/H exchange and K-Cl cotransport in dog red blood cells.

1995 ◽  
Vol 105 (6) ◽  
pp. 677-699 ◽  
Author(s):  
J C Parker ◽  
P B Dunham ◽  
A P Minton
Keyword(s):  
Ionic Strength ◽  
Salt Concentration ◽  
Mechanistic Model ◽  
Regulatory Protein ◽  
Thermodynamic Activity ◽  
Common Mechanism ◽  
Model Parameters ◽  
Set Point ◽  
Weight Percentage ◽  
Empirical Expressions

Dog red cell membranes contain two distinct volume-sensitive transporters: swelling-activated K-Cl cotransport and shrinkage-activated Na/H exchange. Cells were prepared with intracellular salt concentration and weight percentage of cell water (%cw) varied independently by transient permeabilization of the cell membrane to cations. The dependence of transporter-mediated Na and K influxes upon %cw and upon extracellular salt concentration (c(ext)) was measured in cells so prepared. It was found that the critical value of %cw at which transporters are activated, called the set point, is similar for the two transporters, and that the set points for the two transporters decrease similarly with increasing extracellular salt concentration. These findings suggest a common mechanism of regulation of these two transporters. Cellular Na, K, and Cl concentrations were measured as functions of %cw and c(ext). Using these data together with data from the literature for other solute concentrations, empirical expressions were developed to describe the dependence of the intracellular concentrations of all significant small molecule electrolytes, and therefore the intracellular ionic strength, upon %cw and c(ext). A mechanistic model for the dependence of the set point of an individual transporter upon intracellular ionic strength is proposed. According to this model, the set point represents a critical extent of association between the transporter and a postulated soluble regulatory protein, called regulator. Model functions are presented for the calculation of the thermodynamic activity of regulator, and hence extent of regulator-transporter association, as a function of total intracellular protein concentration (or %cw) and ionic strength. The experimentally observed dependence of set point %cw on c(ext) are simulated using these functions and the empirical expressions described above, together with reasonable but not uniquely determined values of model parameters.

A Control Strategy for Continuously Adjusting Attack Angle in Wind Tunnel Experiments

2014 ◽  
Vol 945-949 ◽  
pp. 1632-1636
Author(s):  
Shuang Xi Zhang ◽  
Wen Gai ◽  
Wei Hua Chu ◽  
Nian Liu
Keyword(s):  
Wind Tunnel ◽  
Control Strategy ◽  
Hydraulic System ◽  
External Disturbance ◽  
Attack Angle ◽  
Model Parameters ◽  
Velocity Control ◽  
Wind Tunnel Experiments ◽  
Support Mechanism ◽  
Test Platform

In wind tunnel experiments, in order to adjust the attack angle continuously, the support mechanism movement should be steady and smooth. However, the electro-hydraulic servo system is a typical nonlinear, time-varying and uncertainty system, and the wind tunnel environment is very complicated. To address these problems, an on-line identification and generalized predictive control (GPC) strategy is proposed in this study. Firstly, the Labview and AMESim are integrated to build an electro-hydraulic system simulation model. Secondly, the controlled auto-regressive moving average (CARIMA) model of the electro-hydraulic system is developed. Thirdly, the influence on the system performance owing to the control parameters, model parameters, and external disturbance are widely discussed and deeply analyzed. At last, a test platform is constructed with the National Instruments (NI) embedded real time technology. The proposed control strategy is tested and verified on this test platform. The experimental results show that the angular velocity control precision reaches 0.01°/s. It implies that this control strategy has a good performance for nonlinear velocity control. Thus it satisfies the requirement of the continuously adjusting attack angle in wind tunnel experiments.

CHARACTERIZATION AND MODELING OF INTEGRATED DIODE IN 1.2kV 4H-SiC VERTICAL POWER MOSFET

2009 ◽  
Vol 19 (01) ◽  
pp. 167-172
Author(s):  
HARSH NAIK ◽  
YI WANG ◽  
T. PAUL CHOW
Keyword(s):  
Dynamic Characteristics ◽  
Model Parameters ◽  
Power Mosfet ◽  
Static And Dynamic Characteristics ◽  
Turn On ◽  
Spice Model ◽  
Junction Diode

We have characterized and modeled the integrated diode of a 1.2kV 4 H - SiC power MOSFET. We have measured its static and dynamic characteristics up to 200°C and extracted relevant SPICE model parameters. From the extracted turn-on voltage and ideality factors, we conclude that the integral diode is not a pin junction diode, but a unipolar diode.

scholarly journals Nonlinearities and asymmetries of the human cardiovagal baroreflex

2005 ◽  
Vol 288 (5) ◽  
pp. R1339-R1346 ◽  
Author(s):  
Brian E. Hunt ◽  
William B. Farquhar
Keyword(s):  
Blood Pressure ◽  
Systolic Blood Pressure ◽  
Predictive Value ◽  
Healthy Subjects ◽  
Model Parameters ◽  
Set Point ◽  
Response Range ◽  
Reflex Gain ◽  
Insight Into ◽  
Nonlinear Nature

To determine whether an approach such as the modified Oxford technique can consistently produce data that reveal the nonlinear nature of the cardiovagal baroreflex and to ascertain whether the model parameters provide unique insight into baroreflex function, we retrospectively examined 91 baroreflex trials (38 subjects, 27 men and 11 women, ages 22–72 yr). The modified Oxford technique (bolus sodium nitroprusside followed by bolus phenylephrine) was used to perturb blood pressure, and the resulting systolic blood pressure-R-R interval responses were plotted and modeled using a linear, a four-parameter symmetric, and a five-parameter asymmetric model. Several issues, such as the effect of data averaging, various approaches to gain estimation, and the predictive value of model parameters, were examined during reflex modeling. Sigmoid models accounted for a greater amount of the variance than did the linear model: linear r2 = 0.81 ± 0.01, four-parameter r2 = 0.90 ± 0.08, and five-parameter r2 = 0.90 ± 0.08 ( P < 0.05, linear vs. sigmoid models). Data averaging did not affect model fits. Although the four gain estimates (linear remodel, 1st derivative, peak, and set point) were statistically related, the set point gain was significantly lower than other estimates ( P < 0.05). Subgroup comparisons between young and older healthy subjects revealed differences in all indexes of cardiovagal baroreflex gain, as well as R-R interval operating range and curvature parameters. In conclusion, the modified Oxford technique consistently reveals the nonlinear nature of the human cardiovagal baroreflex. Moreover, of the parameters produced by the symmetric sigmoid model, only the response range provides unique information beyond that of reflex gain.

scholarly journals Integrating Non-Spiking Interneurons in Spiking Neural Networks

2020 ◽  
Author(s):  
Beck Strohmer ◽  
Rasmus Karnøe Stagsted ◽  
Poramate Manoonpong ◽  
Leon Bonde Larsen
Keyword(s):  
Neural Networks ◽  
Closed Loop ◽  
Spiking Neurons ◽  
Legged Robots ◽  
Spiking Neuron ◽  
Mixed Network ◽  
Spiking Neuron Model ◽  
Network Output ◽  
Mixed Networks ◽  
Event Based

AbstractResearchers working with neural networks have historically focused on either non-spiking neurons tractable for running on computers or more biologically plausible spiking neurons typically requiring special hardware. However, in nature homogeneous networks of neurons do not exist. Instead, spiking and non-spiking neurons cooperate, each bringing a different set of advantages. A well researched biological example of such a mixed network is the sensorimotor pathway, responsible for mapping sensory inputs to behavioral changes. This pathway is also well researched in robotics where it is applied to achieve closed-loop operation of legged robots by adapting amplitude, frequency, and phase of the motor output. In this paper we investigate how spiking and non-spiking neurons can be combined to create a sensorimotor neuron pathway capable of shaping network output based on analog input. We propose sub-threshold operation of an existing spiking neuron model to create a non-spiking neuron able to interpret analog information and communicate with spiking neurons. The validity of this methodology is confirmed through a simulation of a closed-loop amplitude regulating network. Additionally, we show that non-spiking neurons can effectively manipulate post-synaptic spiking neurons in an event-based architecture. The ability to work with mixed networks provides an opportunity for researchers to investigate new network architectures for adaptive controllers, potentially improving locomotion strategies of legged robots.

scholarly journals Rainfall-runoff simulations in the Lukovska River Basin with the HEC-HMS model

2019 ◽  
pp. 33-60
Author(s):  
Ranka Eric ◽  
Andrijana Todorovic ◽  
Jasna Plavsic ◽  
Vesna Djukic
Keyword(s):  
River Basin ◽  
Optimal Parameter ◽  
Hydrologic Model ◽  
Model Parameters ◽  
Rainfall Runoff ◽  
Flood Events ◽  
Runoff Generation ◽  
Hydrologic Models ◽  
Generation Mechanisms ◽  
Event Based

Hydrologic models are important for effective water resources management at a basin level. This paper describes an application of the HEC-HMS hydrologic model for simulations of flood hydrographs in the Lukovska River basin. Five flood events observed at the Mercez stream gauge were available for modelling purposes. These events are from two distinct periods and two seasons with different prevailing runoff generation mechanisms. Hence the events are assigned to either ?present? or ?past?, and ?spring? or ?summer? group. The optimal parameter sets of each group are obtained by averaging the optimal parameters for individual events within the group. To assess model transferability, its applicability for simulation of flood events which are not considered in the model calibration, a cross-validation is performed. The results indicate that model parameters vary across the events, and that parameter transfer generally leads to considerable errors in hydrograph peaks and volumes, with the exception of simulation of summer events with ?spring? parameters. Based on these results, recommendations for event-based modeling are given.

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