scholarly journals DETERMINING THE STABILITY CONDITIONS OF THE TRACK-DRIVEN VEHICLE WHILE STAIR CLIMBING AND DESCENDING

2012 ◽  
Vol 15 (1) ◽  
pp. 36-42
Author(s):  
Khoi Duc Pham ◽  
Ha Thi Thu Thai
Keyword(s):  
Mass Velocity ◽  
Research Method ◽  
Stability Limit ◽  
Stair Climbing ◽  
Stability Conditions ◽  
Stable Operation ◽  
Constraint Equations ◽  
The Stability

This article presents the method of determining the stability limit of the vehicle (robots or electric wheelchairs) that use tracks (chain, belt) for climbing and descending stairs. Research method was conducted by modeling vehicle which is working under the influence of some elements such as geometric, mass, velocity, acceleration, friction...Afterthat, we identify some conditions which lead to tipping. Finally, the results of research are constraint equations in order to ensure stable operation of vehicle.

Axial Transonic Rotor and Stage Behavior Near the Stability Limit

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Anthony J. Gannon ◽  
Garth V. Hobson ◽  
William L. Davis
Keyword(s):  
High Speed ◽  
Low Frequency ◽  
Stability Limit ◽  
Stable Operation ◽  
Inlet Flow ◽  
Flow Angle ◽  
The Difference ◽  
The Stability ◽  
Lower Magnitude ◽  
Transonic Rotor

Transient casing pressure data from a transonic rotor and rotor-stator stage measured using high-speed pressure probes embedded in the casewall over the rotor tips are analyzed. Using long data sets sampled at a high frequency, low-frequency (less than once-per-revolution) nonaxisymmetric flow phenomena were detected while operating at steady-state conditions near stall. Both the rotor and stage cases are investigated, and the difference in behavior of a rotor with and without a stator blade row is investigated. Data for both cases over the speed range 70–100% of design and from choke to near the stability limit (stall or surge) are presented. The root mean square power of the low-frequency signal as well as its fraction of the total pressure signal is presented. It was thought that the behavior of these signals as stall was approached could lead to some method of detecting the proximity of stall. For the rotor-only configuration, the strength of these nonaxisymmetric phenomena increased as stall was approached for all speed-lines. However, for the stage configuration, more representative of an operational machine, these were of a lower magnitude and did not exhibit a clearly increasing trend as stall was approached. This would seem to indicate that the stator suppressed these signals somewhat. It is also shown that these nonaxisymmetric phenomena led to a significant variation of the mean relative inlet flow angle into the rotor blade. During stable operation near to stall at 100% speed for the rotor-only case, a 1.9 deg variation of this angle was measured. This compared with a 5.6 deg variation over the entire speed-line. Further, it was observed that while the rotor and stage cases had different stability limits, their peak relative inlet flow angles near stall were similar for both along most speed-lines.

Axial Transonic Rotor and Stage Behavior Near the Stability Limit

2010 ◽  
Author(s):  
Anthony J. Gannon ◽  
Garth V. Hobson ◽  
William L. Davis
Keyword(s):  
High Speed ◽  
Axisymmetric Flow ◽  
Low Frequency ◽  
Stability Limit ◽  
Stable Operation ◽  
Inlet Flow ◽  
Flow Angle ◽  
The Stability ◽  
Lower Magnitude ◽  
Transonic Rotor

Transient casing pressure data from a transonic rotor and rotor-stator stage measured using high-speed pressure probes embedded in the casewall over the rotor tips is analyzed. Using long data sets sampled at a high frequency, low-frequency (less than once-per-revolution) non-axisymmetric flow phenomena were detected while operating at steady-state conditions near stall. Both the rotor and stage cases are investigated and the difference in behavior of a rotor with and without a stator blade row is investigated. Data for both cases over the speed range 70–100% of design and from choke to near the stability limit (stall or surge) is presented. The root mean square power of the low-frequency signal as well as its fraction of the total pressure signal is presented. It was thought that the behavior of these signals as stall was approached could lead to some method of detecting the proximity of stall. For the rotor-only configuration the strength of these non-axisymmetric phenomena increased as stall was approached for all speed-lines. However for the stage configuration, more representative of an operational machine, these were of a lower magnitude and did not exhibit a clearly increasing trend as stall was approached. This would seem to indicate that the stator suppressed these signals somewhat. It is also shown that these non-axisymmetric phenomena led to a significant variation of the mean relative inlet flow angle into the rotor blade. During stable operation near to stall at 100% speed for the rotor-only case a 1.9° variation of this angle was measured. This compared with a 5.6° variation over the entire speed line. Further it was observed that while the rotor and stage cases had different stability limits their peak relative inlet flow angles near stall were similar for both along most speed-lines.

scholarly journals Features of solving the inverse dynamic method equations for the synthesis of stable walking robots controlled motion

2019 ◽  
Vol 18 (1) ◽  
pp. 85-122 ◽  
Author(s):  
Alexander Gorobtsov ◽  
Andrey Andreev ◽  
Alexey Markov ◽  
Andrey Skorikov ◽  
Pavel Tarasov
Keyword(s):  
Dynamic Method ◽  
Walking Robots ◽  
Stability Conditions ◽  
Synthesis Methods ◽  
Motion Synthesis ◽  
Inverse Dynamic ◽  
Unique Problem ◽  
Constraint Equations ◽  
Controlled Motion ◽  
The Stability

The problem of walking robots controlled motion synthesis by the inverse dynamic method is considered. The inverse dynamic method equations are represented by the methods of multibody system dynamics as free bodies motion equations and constraint equations. The variety of constraint equations group are introduced to specify the robot gait, to implement the robot stability conditions and to coordinate specified robot links movement. The key feature of the inverse dynamic method equations in this formulation is the presence of the second derivatives of the system coordinates in the constraint equations expressing the stability conditions that ensure the maintenance of the vertical position by the robot. The determined solution of such equations in general case is impossible due to the uncertainty of the initial conditions for the Lagrange multipliers. An approximate method for solving the inverse dynamic without taking into account the inertial components in the constraint equations that determine the stability of the robot is considered. Constraint equations that determine the coordinate movement of individual robot links and required for unique problem solving based on approximate equations are presented. The implementation of program motion synthesis methods in the control system of the humanoid robot AR-600 is presented. The comparison of theoretical and experimental parameters of controlled motion is performed. It has been established that with the achieved high accuracy of the robot links tracking drives control with an error of several percent, the indicators of the robot's absolute movements, in particular, the angles of roll, yaw and pitch, differ from the programmed by 30-40%. It’s shown that proposed method allows to synthesize robot control in quasistatic mode for different movement types such as moving forward, sideways, walking on stairs, inclinations etc.

The anaerobic treatment of a ligno-cellulosic substrate offering little natural pH buffering capacity

1998 ◽  
Vol 38 (4-5) ◽  
pp. 29-35 ◽  
Author(s):  
C. J. Banks ◽  
P. N. Humphreys
Keyword(s):  
Ph Control ◽  
Anaerobic Treatment ◽  
Buffering Capacity ◽  
Single Stage ◽  
Stable Operation ◽  
Reactor Performance ◽  
Two Stage ◽  
Ph Buffering ◽  
Stage System ◽  
The Stability

The stability and operational performance of single stage digestion with and without liquor recycle and two stage digestion were assessed using a mixture of paper and wood as the digestion substrate. Attempts to maintain stable digestion in both single stage reactors were unsuccessful due to the inherently low natural buffering capacity exhibited; this resulted in a rapid souring of the reactor due to unbuffered volatile fatty acid (VFA) accumulation. The use of lime to control pH was unsatisfactory due to interference with the carbonate/bicarbonate equilibrium resulting in wide oscillations in the control parameter. The two stage system overcame the pH stability problems allowing stable operation for a period of 200 days without any requirement for pH control; this was attributed to the rapid flushing of VFA from the first stage reactor into the second stage, where efficient conversion to methane was established. Reactor performance was judged to be satisfactory with the breakdown of 53% of influent volatile solids. It was concluded that the reactor configuration of the two stage system offers the potential for the treatment of cellulosic wastes with a sub-optimal carbon to nitrogen ratio for conventional digestion.

scholarly journals Stability Analysis of Different Regulation Modes of Hydropower Units

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1933
Author(s):  
Xinran Guo ◽  
Yuanchu Cheng ◽  
Jiada Wei ◽  
Yitian Luo
Keyword(s):  
Stable Operation ◽  
Rotor Speed ◽  
Frequency Range ◽  
Power Regulation ◽  
Normal Frequency ◽  
Dynamic Performances ◽  
Negative Damping ◽  
The Stability ◽  
Regulation Mode ◽  
Water Inertia

The dynamic characteristics of hydropower unit governing systems considerably influence the stability of hydropower units and the connected power system. The dynamic performances of hydropower units with power regulation mode (PRM) and opening regulation mode (ORM) are different. This paper establishes a detailed linear model of a hydropower unit based on the Phillips–Heffron model. The damping characteristic and stability of two regulation modes with different water inertia time constants TW were analyzed. ORM tended to provide negative damping, while PRM often provided positive damping in the major parts of the frequency range within the normal frequency oscillations when TW was large. Eigenvalue analysis illustrated that PRM has better stability than ORM. To validate the analysis, a simulation under two typical faults WAS conducted based on a nonlinear model of a hydropower unit. The simulation results illustrated that the responses of units with PRM are more stable in terms of important operating parameters, such as output power, rotor speed, and power angles. For hydropower units facing challenges in stable operation, PRM is recommended to obtain good dynamic stability.

scholarly journals Asymmetry underlies stability in power grids

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ferenc Molnar ◽  
Takashi Nishikawa ◽  
Adilson E. Motter
Keyword(s):  
Symmetry Breaking ◽  
Real World ◽  
Power Grids ◽  
Stable Operation ◽  
World Systems ◽  
Symmetric State ◽  
Network Systems ◽  
Additional Improvement ◽  
The Stability ◽  
General Method

AbstractBehavioral homogeneity is often critical for the functioning of network systems of interacting entities. In power grids, whose stable operation requires generator frequencies to be synchronized—and thus homogeneous—across the network, previous work suggests that the stability of synchronous states can be improved by making the generators homogeneous. Here, we show that a substantial additional improvement is possible by instead making the generators suitably heterogeneous. We develop a general method for attributing this counterintuitive effect to converse symmetry breaking, a recently established phenomenon in which the system must be asymmetric to maintain a stable symmetric state. These findings constitute the first demonstration of converse symmetry breaking in real-world systems, and our method promises to enable identification of this phenomenon in other networks whose functions rely on behavioral homogeneity.

scholarly journals Causality and stability conditions of a conformal charged fluid

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
Farid Taghinavaz
Keyword(s):  
Chemical Potential ◽  
Second Law Of Thermodynamics ◽  
Dense Medium ◽  
Wave Number ◽  
Second Law ◽  
Stability Conditions ◽  
Charged Fluid ◽  
Large Wave ◽  
The Stability ◽  
Large Wave Number

Abstract In this paper, I study the conditions imposed on a normal charged fluid so that the causality and stability criteria hold for this fluid. I adopt the newly developed General Frame (GF) notion in the relativistic hydrodynamics framework which states that hydrodynamic frames have to be fixed after applying the stability and causality conditions. To do this, I take a charged conformal matter in the flat and 3 + 1 dimension to analyze better these conditions. The causality condition is applied by looking to the asymptotic velocity of sound hydro modes at the large wave number limit and stability conditions are imposed by looking to the imaginary parts of hydro modes as well as the Routh-Hurwitz criteria. By fixing some of the transports, the suitable spaces for other ones are derived. I observe that in a dense medium having a finite U(1) charge with chemical potential μ0, negative values for transports appear and the second law of thermodynamics has not ruled out the existence of such values. Sign of scalar transports are not limited by any constraints and just a combination of vector transports is limited by the second law of thermodynamic. Also numerically it is proved that the most favorable region for transports $$ {\tilde{\upgamma}}_{1,2}, $$ γ ˜ 1 , 2 , coefficients of the dissipative terms of the current, is of negative values.

scholarly journals Iterative stability analysis for general polynomial control systems

2021 ◽  
Author(s):  
Bo Xiao ◽  
Hak-Keung Lam ◽  
Zhixiong Zhong
Keyword(s):  
Stability Analysis ◽  
Lyapunov Function ◽  
Control Systems ◽  
Polynomial System ◽  
Stability Conditions ◽  
General Polynomial ◽  
Main Challenge ◽  
Detailed Simulation ◽  
Feasible Solutions ◽  
The Stability

AbstractThe main challenge of the stability analysis for general polynomial control systems is that non-convex terms exist in the stability conditions, which hinders solving the stability conditions numerically. Most approaches in the literature impose constraints on the Lyapunov function candidates or the non-convex related terms to circumvent this problem. Motivated by this difficulty, in this paper, we confront the non-convex problem directly and present an iterative stability analysis to address the long-standing problem in general polynomial control systems. Different from the existing methods, no constraints are imposed on the polynomial Lyapunov function candidates. Therefore, the limitations on the Lyapunov function candidate and non-convex terms are eliminated from the proposed analysis, which makes the proposed method more general than the state-of-the-art. In the proposed approach, the stability for the general polynomial model is analyzed and the original non-convex stability conditions are developed. To solve the non-convex stability conditions through the sum-of-squares programming, the iterative stability analysis is presented. The feasible solutions are verified by the original non-convex stability conditions to guarantee the asymptotic stability of the general polynomial system. The detailed simulation example is provided to verify the effectiveness of the proposed approach. The simulation results show that the proposed approach is more capable to find feasible solutions for the general polynomial control systems when compared with the existing ones.

Optimization of the Robust Stability Limit for Multi-Cutter Turning Processes

2015 ◽  
Author(s):  
Marta J. Reith ◽  
Daniel Bachrathy ◽  
Gabor Stepan
Keyword(s):  
Robust Stability ◽  
Optimal Parameter ◽  
Stability Limit ◽  
Boundary Function ◽  
Lower Envelope ◽  
Computation Method ◽  
Parameter Region ◽  
Dynamical Parameters ◽  
The Stability ◽  
Machining Parameter

Multi-cutter turning systems bear huge potential in increasing cutting performance. In this study we show that the stable parameter region can be extended by the optimal tuning of system parameters. The optimal parameter regions can be identified by means of stability charts. Since the stability boundaries are highly sensitive to the dynamical parameters of the machine tool, the reliable exploitation of the so-called stability pockets is limited. Still, the lower envelope of the stability lobes is an appropriate upper boundary function for optimization purposes with an objective function taken for maximal material removal rates. This lower envelope is computed by the Robust Stability Computation method presented in the paper. It is shown in this study, that according to theoretical results obtained for optimally tuned cutters, the safe stable machining parameter region can significantly be extended, which has also been validated by machining tests.

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