scholarly journals Dynamic Stability of Open-Loop Hopping

2006 ◽  
Vol 129 (3) ◽  
pp. 275-284 ◽  
Author(s):  
Jorge G. Cham ◽  
Mark R. Cutkosky
Keyword(s):  
Sensory Feedback ◽  
Motor Pattern ◽  
Open Loop ◽  
Legged Robots ◽  
Open Loop System ◽  
System Parameters ◽  
Model Driven ◽  
The Stability ◽  
And Control ◽  
Hopping Model

Simulations and physical robots have shown that hopping and running are possible without sensory feedback. However, stable behavior is often limited to a certain range of the parameters of the open-loop system. Even the simplest of hopping systems can exhibit unstable behavior that results in unpredictable nonperiodic motion as system parameters are adjusted. This paper analyzes the stability of a simplified vertical hopping model driven by an open-loop, feedforward motor pattern. Periodic orbits of the resulting hybrid system are analyzed through a generalized formula for the system’s Poincare Map and Jacobian. The observed behavior is validated experimentally in a physical pneumatically actuated hopping machine. This approach leads to observations on the stability of this and similar systems, revealing inherent limitations of open-loop hopping and providing insights that can inform the design and control of dynamic legged robots capable of rapid and robust locomotion.

scholarly journals Dynamics and stability of running on rough terrains

2019 ◽  
Vol 6 (3) ◽  
pp. 181729 ◽  
Author(s):  
Nihav Dhawale ◽  
Shreyas Mandre ◽  
Madhusudhan Venkadesan
Keyword(s):  
Sensory Feedback ◽  
Dimensionless Parameter ◽  
Sagittal Plane ◽  
Sensory Information ◽  
Open Loop ◽  
Rough Terrain ◽  
Two Dimensional ◽  
Flat Surfaces ◽  
And Control ◽  
Flat Ground

Stability of running on rough terrain depends on the propagation of perturbations due to the ground. We consider stability within the sagittal plane and model the dynamics of running as a two-dimensional body with alternating aerial and stance phases. Stance is modelled as a passive, impulsive collision followed by an active, impulsive push-off that compensates for collisional losses. Such a runner has infinitely many strategies to maintain periodic gaits on flat ground. However, these strategies differ in how perturbations due to terrain unevenness are propagated. Instabilities manifest as tumbling (orientational instability) or failing to maintain a steady speed (translational instability). We find that open-loop strategies that avoid sensory feedback are sufficient to maintain stability on step-like terrains with piecewise flat surfaces that randomly vary in height. However, these open-loop runners lose orientational stability on rough terrains whose slope also varies randomly. The orientational instability is significantly mitigated by minimizing the tangential collision, which typically requires sensory information and anticipatory strategies such as leg retraction. By analysing the propagation of perturbations, we derive a single dimensionless parameter that governs stability. This parameter provides guidelines for the design and control of both biological and robotic runners.

Use of an Open-Loop System to Increase Physical Activity

2012 ◽  
Vol 24 (3) ◽  
pp. 384-398 ◽  
Author(s):  
James N. Roemmich ◽  
Christina L. Lobarinas ◽  
Jacob E. Barkley ◽  
Tressa M. White ◽  
Rocco Paluch ◽  
...  
Keyword(s):  
Physical Activity ◽  
Screen Time ◽  
Open Loop ◽  
Loop System ◽  
Tv Viewing ◽  
Open Loop System ◽  
Tv Watching ◽  
And Control ◽  
Children’S Physical Activity

This study evaluated the effectiveness of an open-loop system that reinforces physical activity with TV watching to increase children’s physical activity. Nonoverweight, sedentary boys and girls (8–12 y) were randomized to a group that received feedback of activity counts + reinforcement for physical activity by providing access to television (F+R, n = 20); or to feedback, no reinforcement (Feedback, n = 20) or no feedback, no reinforcement control (Control, n = 21) groups. Children wore an accelerometer with a count display for 4-months with a 1-year follow-up. F+R reduced TV by 68 min/day and TV time was lower than the Feedback (p < .005) and Control (p < .002) groups. TV time of F+R remained 31 min lower (p < .02) than baseline at 1-year. F+R had a 44% increase in physical activity, which was greater than the feedback (p < .04) and control (p < .01) groups. An open-loop system decreases TV viewing and increases physical activity of children for 4-months. TV of the F+R group remained lower at 12 months, suggesting a reduction in screen-time habits.

Design of Materials and Mechanisms for Responsive Robots

2018 ◽  
Vol 1 (1) ◽  
pp. 359-384 ◽  
Author(s):  
Elliot W. Hawkes ◽  
Mark R. Cutkosky
Keyword(s):  
Genetic Algorithms ◽  
Energy Storage ◽  
Environmental Conditions ◽  
Degrees Of Freedom ◽  
Closed Loop ◽  
Open Loop ◽  
Challenging Problem ◽  
Manufacturing Applications ◽  
The Stability ◽  
And Control

As robots move beyond manufacturing applications to less predictable environments, they can increasingly benefit, as animals do, from integrating sensing and control with the passive properties provided by particular combinations and arrangements of materials and mechanisms. This realization is partly responsible for the recent proliferation of soft and bioinspired robots. Tuned materials and mechanisms can provide several kinds of benefits, including energy storage and recovery, increased physical robustness, and decreased response time to sudden events. In addition, they may offer passive open-loop behaviors and responses to external changes in loading or environmental conditions. Collectively, these properties can also increase the stability of a robot as it interacts with the environment and allow the closed-loop controller to reduce the apparent degrees of freedom subject to control. The design of appropriate materials and mechanisms remains a challenging problem; bioinspiration, genetic algorithms, and numerical shape and materials optimization are all applicable. New multimaterial fabrication processes are also steadily increasing the range and magnitude of passive properties available for intrinsically responsive robots.

scholarly journals Effect of fiber and solenoid variation parameters on the elements of a corrector PID for electromagnetic fiber squeezer based polarization controller

2020 ◽  
Vol 10 (3) ◽  
pp. 2441 ◽  
Author(s):  
Abdallah Zahidi ◽  
Amrane Said ◽  
Nawfel Azami ◽  
Naoual Nasser
Keyword(s):  
Detection System ◽  
Light Output ◽  
Single Mode ◽  
Single Mode Fiber ◽  
Open Loop ◽  
Polarization Controller ◽  
Heterodyne Detection ◽  
System Parameters ◽  
Stability Performance ◽  
The Stability

Controlling the polarization of the light output from single-mode fiber systems is very important for connecting it to polarization-dependent integrated optical circuits, while applications using a heterodyne detection system. Polarization controller using fiber squeezer is attractive for a low-loss, low-penalty coherent optical fiber trunk system. However, for polarization controllers using electromagnetic fiber squeezer, the stability problem due to the saturation of their magnetic circuit must be studied. In fact, in their conventional configuration, open-loop stability affects performance and limits applications. First at all, this effect has been analyzed and a feedback circuit with correctors has been proposed to improve stability performance. Then a simulation study is proposed to examine the influence of the system parameters on the corrector constants. The results of the simulation show that if the system parameters change the constants Kp, Ki and Kd of the PID corrector must be adjusted to keep an optimized dynamic response.

scholarly journals Nonlinear Model Predictive Controller and Feasible Path Planning for Autonomous Robots

2016 ◽  
Vol 6 (1) ◽  
pp. 178-186
Author(s):  
Vu Trieu Minh
Keyword(s):  
Predictive Control ◽  
Nonlinear Model ◽  
Autonomous Robots ◽  
Open Loop ◽  
Tracking Errors ◽  
Physical Constraints ◽  
Predictive Controller ◽  
Feasible Path ◽  
The Stability ◽  
And Control

AbstractThis paper develops the nonlinear model predictive control (NMPC) algorithm to control autonomous robots tracking feasible paths generated directly from the nonlinear dynamic equations.NMPC algorithm can secure the stability of this dynamic system by imposing additional conditions on the open loop NMPC regulator. The NMPC algorithm maintains a terminal constrained region to the origin and thus, guarantees the stability of the nonlinear system. Simulations show that the NMPC algorithm can minimize the path tracking errors and control the autonomous robots tracking exactly on the feasible paths subject to the system’s physical constraints.

A New Approach to Controlling Thermal Processes

1969 ◽  
Vol 2 (11) ◽  
pp. T181-T185 ◽  
Author(s):  
William K. Roots ◽  
Loren D. Meeker
Keyword(s):  
Transient Response ◽  
Closed Loop ◽  
Open Loop ◽  
Thermal Processes ◽  
New Approach ◽  
Plasma Torches ◽  
The Stability ◽  
Fluidised Beds ◽  
Response Determination ◽  
And Control

Roots and Wu (1967) established that meaningful models of common thermal processes (boilers without superheaters, furnaces, ovens, vats, kilns etc.) can be made from a cascade comprising an open-loop gain μ, a transit delay L, and a salient time constant T. They used this model to establish facile procedures for stability determination when such processes were closed-loop controlled. A new procedure is now presented that not only facilitates stability studies but also greatly simplifies transient response determination for all commands and disturbances likely to be encountered by such closed loop controlled processes. This new approach is based on a generalised parameter v that incorporates μ, L and T. Then by means of a new plane, the w plane, displays are presented that readily predict the stability criteria and the transient response for any practical combination of command and disturbance; as is shown by the examples contained in the Appendix. This has radically simplified the control amd instrumentation of the processes with which the authors are associated (induction furnaces, fluidised beds, plasma torches, zone refining, etc.) and the presentation is intended for industrial engineers concerned with the design and control of similar thermal processes.

scholarly journals Study of the stability of fuzzy controllers by an estimation of the attraction regions: A Vector Norm approach

2002 ◽  
Vol 8 (3) ◽  
pp. 221-231 ◽  
Author(s):  
J.-Y. Dieulot ◽  
A. El Kamel ◽  
P. Borne
Keyword(s):  
Fuzzy Controller ◽  
Domain Of Attraction ◽  
Constant Term ◽  
Open Loop ◽  
Region Of Attraction ◽  
Open Loop System ◽  
Controlled System ◽  
Disjoint Sets ◽  
The Stability ◽  
Vector Norms

A fuzzy controller with singleton defuzzification can be considered as the association of a regionwise constant term and of a regionwise non linear term, the latter being bounded by a linear controller. Based on the regionwise structure of fuzzy controller, the state space is partitioned into a series of disjoint sets. The fuzzy controller parameters are tuned in order to ensure that theith set is included into the domain of attraction of the preceding sets of the series. If the first set of the series is included into the region of attraction of the equilibrium point, the overall fuzzy controlled system is stable. The attractors are estimated with the help of the comparison principle, using Vector Norms, which ensures the robustness with respect to uncertainties and perturbations of the open loop system.

Modeling and Control of Forward Converter

2011 ◽  
Vol 130-134 ◽  
pp. 1986-1989
Author(s):  
Qiang He
Keyword(s):  
Power Supply ◽  
Average Method ◽  
Open Loop ◽  
Average Model ◽  
Function Model ◽  
Modeling And Control ◽  
Forward Converter ◽  
Loop Transfer Function ◽  
The Stability ◽  
And Control

The average model of the forward converter is build with the state-space average method. The open-loop transfer function model is deduced in detail according to the average model of the forward converter, the controller is designed based frequency domain by the type III compensation network. And the stability of the control system has been improved. The modeling and simulation of system was implemented based Matlab. The results of simulation confirm that the controller is capable of reduced steady state error and improve controller's reliability during power supply disturbance and load disturbance．

Modeling and Simulation of Boost Converter with Voltage Feedback Control

2014 ◽  
Vol 668-669 ◽  
pp. 482-485
Author(s):  
Qiang He
Keyword(s):  
Control System ◽  
Mathematic Model ◽  
Boost Converter ◽  
Open Loop ◽  
Open Loop System ◽  
Loop Transfer Function ◽  
Proper Design ◽  
Simulation Results ◽  
Voltage Feedback ◽  
And Control

In order to achieve a proper design and control, it is necessary to have an exact model of boost converter. In this paper, the mathematic model of boost converter is proposed by the state-space average method. In the next step, the open-loop transfer function model without compensation is deduced in detail according to the mathematic model of the boost converter, the controller is designed according to frequency domain. The phase margin and magnitude margin of the open-loop system of the boost converter with compensator have both been increased. After compensating, the control system becomes stable. Using Matlab 7.1, the simulation of the control system of boost converter was implemented. The simulation results of control system confirm that the controller can reduce steady state error and resist power supply disturbance.

Modelling of Dynamic and Control of Six-Rotor Autonomous Unmanned Aerial Vehicle

2013 ◽  
Vol 198 ◽  
pp. 220-225 ◽  
Author(s):  
Daniel Ołdziej ◽  
Zdzisław Gosiewski
Keyword(s):  
Equations Of Motion ◽  
Control Plant ◽  
Open Loop ◽  
Simulation Environment ◽  
Open Loop System ◽  
Plant Model ◽  
Modeling And Control ◽  
Lqr Controller ◽  
Aerial Vehicle ◽  
And Control

The paper describes matters of modeling and control of aerial vehicle in rotorcraft configuration. Equations of motion were derived and dynamic model of six-rotor was build. To find the best adjustment of model to real object the dynamics of the drives was joined to the control plant model. Trimming and linearization were performed. Open loop system and LQR controller were checked in simulation environment. Next the faults of the actuator/sensor elements were arranged and the minimal number of observed outputs and drives for LQR stabilization process were specified.

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