Inertia Change Research Articles

The CH4 cycles on Pluto over seasonal and astronomical timescales

Pluto's surface is covered in numerous CH4 ice deposits, that vary in texture and brightness, as revealed by the New Horizons spacecraft as it flew by Pluto in July 2015. These observations suggest that CH4 on Pluto has a complex history, involving reservoirs of different composition, thickness and stability controlled by volatile processes occurring on different timescales. In order to interpret these observations, we use a Pluto volatile transport model able to simulate the cycles of N2 and CH4 ices over millions of years. By assuming fixed solid mixing ratios, we explore how changes in surface albedos, emissivities and thermal inertias impact volatile transport. This work is therefore a direct and natural continuation of the work by Bertrand et al. (2018), which only explored the N2 cycles. Results show that bright CH4 deposits can create cold traps for N2 ice outside Sputnik Planitia, leading to a strong coupling between the N2 and CH4 cycles. Depending on the assumed albedo for CH4 ice, the model predicts CH4 ice accumulation (1) at the same equatorial latitudes where the Bladed Terrain Deposits are observed, supporting the idea that these CH4-rich deposits are massive and perennial, or (2) at mid-latitudes (25°− 70°), forming a thick mantle which is consistent with New Horizons observations. In our simulations, both CH4 ice reservoirs are not in an equilibrium state and either one can dominate the other over long timescales, depending on the assumptions made for the CH4 albedo. This suggests that long-term volatile transport exists between the observed reservoirs. The model also reproduces the formation of N2 deposits at mid-latitudes and in the equatorial depressions surrounding the Bladed Terrain Deposits, as observed by New Horizons. At the poles, only seasonal CH4 and N2 deposits are obtained in Pluto's current orbital configuration. Finally, we show that Pluto's atmosphere always contained, over the last astronomical cycles, enough gaseous CH4 to absorb most of the incoming Lyman-α flux.

GA-ANFIS PID compensated model reference adaptive control for BLDC motor

Adaptive control is one of the widely used control strategies to design advanced control systems for better performance and accuracy. Model reference adaptive control (MRAC) is a direct adaptive strategy with some adjustable controller parameters and an adjusting mechanism to adjust them. In this work Model Reference Adaptive Control for BLDC motors has been designed with a PID controller tuned by GA-ANFIS. GA-Trained ANFIS framework for tuning the PID controller has been proposed. This is used along with the MRAC to deliver enhanced performance in the control of BLDC motor. The performance of the proposed approach is validated for motor control under conditions of change in speed, change in load, change in inertia and change in phase resistance.. The performance is validated against convention PID and self tuning PID controllers. The result demonstrates a superior performance of the proposed approach Normal 0 false false false EN-IN X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

Application of TKEO in the process of automatic balancing of the rotor

The article presents an example of application of the Teager-Kaiser Energy Operator in automatic rotor balancing. The Teagear Kaiser Energy Operator is a signal analysis method, which allows for some mechanical objects to estimate energy changes in Newtonian terms by means of a displacement signal. Rotors are a structural element that rotates around an axis. Traditional balancing of the rotors is based on the introduction of correction masses, the aim of which is to reduce vibrations and noise during machine operation. Traditional balancing of the rotors is also possible. It can be realized by a system of correction masses with variable distance from the axis of rotation. The change of the correction mass distance from the axis of rotation influences the change of inertia of the object and thus reduces the unbalance. Depending on the design of the device, the modernization may assume extension or replacement of individual elements. Improvement of the operation of the device requires selection of elements depending on the overall interference in the operation of the machine and the impact on the operation of the entire device. The presented original method of automatic unbalance control with the use of the Energy Operator with the selection of parameters has been performed on a real laboratory stand..

On the Role of External Walls in the Reduction of Energy Demand and the Mitigation of Human Thermal Discomfort

The structure and thermal properties of external walls affect both the thermal conditions inside the building and the energy demand. This applies to the energy requirement for heating as well as cooling. While the relationship between thermal insulation and heating is well-known, the effect of thermal insulation on overheating is not evident. One can find opinions that thick thermal insulation creates a “thermos effect” and significantly deteriorates the comfort conditions during the summer. In order to prove these statements, an office room with south-oriented glazing and a high thermal load from equipment was simulated by means of the Energy Plus program. The reference variant was a two-layer wall made from ceramic blocks and a 10 cm layer of thermal insulation. The duration of overheating in the investigated intensively used office space without window shading was approximately 26 to 29 days per year, depending on the expected comfort acceptance range, while in the case of the not insulated wall, it would be shorter by over 3 days. Increasing the thickness of the thermal insulation layer by up to 30 cm extended the overheating period by 4% to 9%. In relation to the whole simulation period, covering four summer months, this means approximately two extra days of discomfort. The effects of various passive methods of protecting buildings against overheating were also investigated. The use of night ventilation in this facility enables reducing the unfavorable conditions by as much as 31%, or up to 46% of the initial period of overheating. The change of the thermal inertia of a building by replacing the ceramic layer with heavy structural concrete allows a further reduction of the overheating duration by 8% to 9%. When the most effective ways of overheating protection are applied, such as night cooling, even a significant thickening of insulation no longer has any impact on its duration. The results shown above are obviously related to the adopted assumptions. However, on the basis of the conducted analyses, it is possible to reduce concerns relating to excessive insulating the building with respect to overheating. Having an optimal window area with nighttime cooling of buildings, window shading, and the inertial benefits associated with a massive construction are the most important and effective measures of protection against overheating. Efficient thermal insulation of the walls does not conflict with the thermal comfort conditions.

Relating braking indices of young pulsars to the dynamics of superfluid cores

Pulsars are stars that emit electromagnetic radiation in well-defined time intervals. The frequency of such pulses decays with time as is quantified by the braking index (n). In the canonical model n = 3 for all pulsars, but observational data show that n ≠ 3, indicating a limitation of the model. In this work we present a new approach to study the frequency decay of the rotation of a pulsar, based on an adaptation of the canonical one. We consider the pulsar a star that rotates in vacuum and has a strong magnetic field but, differently from the canonical model, we assume that its moment of inertia changes in time due to a uniform variation of a displacement parameter in time. We found that the braking index results smaller than the canonical value as a consequence of an increase in the star's displacement parameter, whose variation is small enough to allow plausible physical considerations that can be applied to a more complex model for pulsars in the future. In particular, this variation is of the order of neutron vortices' creep in rotating superfluids. When applied to pulsar data our model yielded values for the stars' braking indices close to the observational ones. The application of this approach to a more complex star model, where pulsars are assumed to have superfluid interiors, is the next step in probing it. We hypothesize that the slow expansion of the displacement parameter might mimic the motion of core superfluid neutron vortices in realistic models.

LPV gain-scheduled attitude control for satellite with time-varying inertia

The performance of an attitude control system is impacted by the inertia change, especially for small satellites. Although there are various control methods for satellites with inertia uncertainties, very few controllers are designed with consideration of time-varying inertia. In this paper, a linear parameter varying (LPV) model is established for a satellite with time-varying inertia. Moreover, because of their common occurrences, the actuator faults and saturation are considered during the controller design. A gain-scheduled controller is developed to guarantee the steady-state and transient performance of the system by limiting the steady-state variance and regional pole constraints. The simulations indicate that the proposed controller improves the stability performance by adjusting the gain with the inertia variations.

Quality disclosure and the timing of insurers’ adjustments: Evidence from medicare advantage

Mandatory quality disclosure often includes a period over which the quality of new entrants is unreported. This provides the opportunity for forward-looking firms to adjust product characteristics in advance of disclosure. Using comprehensive data on Medicare Advantage (MA) from 2007 to 2015, I exploit the design of the MA Star Rating program to examine the presence of forward-looking behavior among insurers. I find that high-quality insurers reduce prices leading up to quality disclosure, while low-quality insurers increase prices in advance of quality disclosure. These dynamics are consistent with firms anticipating a future change in consumer inertia and updating current-period prices accordingly.

Flutter to tumble transition of buoyant spheres triggered by rotational inertia changes

Heavy particles sink straight in water, while buoyant bubbles and spheres may zigzag or spiral as they rise. The precise conditions that trigger such path-instabilities are still not completely understood. For a buoyant rising sphere, two parameters are believed to govern the development of unsteady dynamics: the particle’s density relative to the fluid, and its Galileo number. Consequently, with these parameters specified, the opportunities for variation in particle dynamics appear limited. In contrast to this picture, here we demonstrate that vigorous path-oscillations can be triggered by modulating a spherical particle’s moment of inertia (MoI). For a buoyant sphere rising in a turbulent flow, MoI reduction triggers a tumble–flutter transition, while in quiescent liquid, it induces a modification of the sphere wake resulting in large-amplitude path-oscillations. The present finding opens the door for control of particle path- and wake-instabilities, with potential for enhanced mixing and heat transfer in particle-laden and dispersed multiphase environments.

Observing the variation of asteroid thermal inertia with heliocentric distance

Thermal inertia is a useful property to characterise a planetary surface since it can be used as a qualitative measure of the regolith grain size. It is expected to vary with heliocentric distance because of its dependence on temperature. However, no previous investigation has conclusively observed a change in thermal inertia for any given planetary body. We have addressed this by using NEOWISE data and the Advanced Thermophysical Model to study the thermophysical properties of the near-Earth asteroids (1036) Ganymed, (1580) Betulia, and (276049) 2002 CE26 as they moved around their highly eccentric orbits. We confirm that the thermal inertia values of Ganymed and 2002 CE26 do vary with heliocentric distance, although the degree of variation observed depends on the spectral emissivity assumed in the thermophysical modelling. We also confirm that the thermal inertia of Betulia did not change for three different observations obtained at the same heliocentric distance. Depending on the spectral emissivity, the variations for Ganymed and 2002 CE26 are potentially more extreme than that implied by theoretical models of heat transfer within asteroidal regoliths, which might be explained by asteroids having thermal properties that also vary with depth. Accounting for this variation reduces a previously observed trend of decreasing asteroid thermal inertia with increasing size, and suggests that the surfaces of small and large asteroids could be much more similar than previously thought. Furthermore, this variation can affect Yarkovsky orbital drift predictions by a few tens of per cent.

Adaptive experience mapping based predictive controller for under-damped type 1 systems

This paper improves upon experience mapping based predictive controller (EMPC) for an under-damped type 1 system which is a fairly new concept presented in literature. EMPC has been earlier demonstrated for an under-damped type 1 system. However, the earlier EMPC controller did not address changes in system parameters and hence the performance in terms of rise time and overshoots deteriorated with change in friction and inertia. This paper develops a theoretical basis for EMPC presented earlier. An adaptation technique is proposed for EMPC to control under-damped type 1 systems for variations in load friction and inertia. The present control action is decided based on the steady state error due to the previous control action. The general nth order type-1 under-damped system is simulated and the results of simulation for system variation and various demands are presented. EMPC is shown to perform robustly with adaptation. Adaptive EMPC controller is shown to outperform proportional derivative controller and a Model reference based adaptive controller. The system is also simulated and practically implemented with a PMDC motor based positioning system coupled to a load through a flexible shaft. The results of these simulations and experiments are presented and it is observed experimentally that adaptive EMPC performs well.

No-Tension Sensor Closed-Loop Control Method with Adaptive PI Parameters for Two-Motor Winding System

In a winding system, it is very important to control the tension precisely. Based on the process of rewinding and unwinding, a sensorless tension control method with PI parameters of adaptive speed controllers is proposed in this paper. According to the principle of torque balance, a tension observer is designed to replace the tension sensor, and the observed value instead of the measured value of tension is used as feedback. Then the measurement delay caused by tension sensor is reduced. For the time-variable inertia, Landau discrete-time recursive algorithm is used to estimate the inertias of the rewind and unwind motors. Moreover, the estimated inertias are used to adjust the PI parameters of the speed controllers. As the tension control system has the ability to adapt to the change of inertia, its dynamic performance is improved to some extent. In addition, the proposed sensorless tension control method is simple and easy to implement, which only uses the current and speed signals of the motors without any additional hardware needed. At last, the feasibility and effectiveness of the proposed method are verified by the experimental results.

Vortex-dipole collapse induced by droplet inertia and phase change

Droplet-laden flows with phase change are common. This study brings to light a mechanism by which droplet inertial dynamics and local phase change, taking place at sub-Kolmogorov scales, affect vortex dynamics in the inertial range of turbulence. To do this we consider vortices placed in a supersaturated ambient initially at constant temperature, homogeneous vapour concentration and uniformly distributed droplets. The droplets also act as sites of phase change. This allows the time scales associated with particle inertia and phase change, which could be significantly different from each other and from the time scale of the flow, to become coupled, and for their combined dynamics to govern the flow. The thermodynamics of condensation and evaporation have a characteristic time scale $\unicode[STIX]{x1D70F}_{s}$. The water droplets are treated as Stokesian inertial particles with a characteristic time scale $\unicode[STIX]{x1D70F}_{p}$, whose behaviour we approximate using an $O(\unicode[STIX]{x1D70F}_{p})$ truncation of the Maxey–Riley equation for heavy particles. This inertia leads the water droplets to vacate the vicinity of vortices, leaving no nuclei for the vapour to condense. The condensation process is thus spatially inhomogeneous, and leaves vortices in the flow colder than their surroundings. The combination of buoyancy and vorticity generates a lift force on the vortices perpendicular to their velocity relative to the fluid around them. In the case of a vortex dipole, this lift force can propel the vortices towards each other and undergo collapse, a phenomenon studied by Ravichandran et al. (Phys. Rev. Fluids, vol. 2, 2017, 034702). We find, spanning the space of the two time scales, $\unicode[STIX]{x1D70F}_{p}$ and $\unicode[STIX]{x1D70F}_{s}$, the region in which lift-induced dipole collapse can occur, and show numerically that the product of the time scales is the determining parameter. Our findings agree with our results from scaling arguments. We also study the influence of varying the initial supersaturation, and find that the strength of the lift-induced mechanism has a power-law dependence on the phase-change time scale $\unicode[STIX]{x1D70F}_{s}$. We then study systems of many vortices and show that the same coupling between the two time scales alters the dynamics of such systems, by energising the smaller scales. We show that this effect is significantly more pronounced at higher Reynolds numbers. Finally, we discuss how this effect could be relevant in conditions typical of clouds.

3D Suspended Polymeric Microfluidics (SPMF3) with Flow Orthogonal to Bending (FOB) for Fluid Analysis through Kinematic Viscosity

Measuring of fluid properties such as dynamic viscosity and density has tremendous potential for various applications from physical to biological to chemical sensing. However, it is almost impossible to affect only one of these properties, as dynamic viscosity and density are coupled. Hence, this paper proposes kinematic viscosity as a comprehensive parameter which can be used to study the effect of fluid properties applicable to various fluids from Newtonian fluids, such as water, to non-Newtonian fluids, such as blood. This paper also proposes an ideal microplatform, namely polymeric suspended microfluidics (SPMF3), with flow plane orthogonal to the bending plane of the structure, along with tested results of various fluids covering a wide range of engineering applications. Kinematic viscosity, also called momentum diffusivity, considers changes in both fluid intermolecular forces and molecular inertia that define dynamic viscosity and fluid density, respectively. In this study a 3D suspended polymeric microfluidic system (SPMF3) was employed to detect changes in fluid parameters such as dynamic viscosity and density during fluid processes. Using this innovative design along with theoretical and experimental results, it is shown that, in fluids, the variations of fluid density and dynamic viscosity are not easily comprehensible due to their interconnectivity. Since any change in a fluid will affect both density and dynamic viscosity, measuring both of them is necessary to identify the fluid or process status. Finally, changes in fluid properties were analyzed using simulation and experiments. The experimental results with salt-DI water solution and milk with different fat concentrations as a colloidal fluid show that kinematic viscosity is a comprehensive parameter that can identify the fluids in a unique way using the proposed microplatform.

Adaptive composite control method of permanent magnet synchronous motor systems

With the development of digital signal processes, the relative differences of PMSM single loop in control periods between the speed loop and current loops are becoming smaller or even vanishing. Therefore, cascade control schemes seem to be unnecessary. In addition, considering the effects of disturbances and the variety of moments of inertia, this paper proposes a scheme using an adaptive non-cascade control method to design the controller, which merges speed loop and q-axis current loop into one single loop. First, an extended state observer (ESO) is employed to estimate the disturbances of the system. The estimated value is used in the feedforward compensation design to improve the capability of system anti-disturbance. Then, considering the performance degradation caused by inertia change, an adaptive control scheme is developed. By using inertia identification technology, the feedforward compensation gain can be tuned automatically according to the identification value. Several groups of simulations and experiments are carried out and the results demonstrate the effectiveness of the proposed scheme.

Executive team consensus-based perspective of organization evolution

PurposeExecutive leadership plays a crucial role in initiating, shaping and directing strategic reorientations. But it must somehow mediate between forces of inertia and fundamental changes. This paper aims to address the unresolved paradox: how do executives address these conflicting demands?Design/methodology/approachThis paper aims to interweave two streams of seminal research in organizational evolution and organizational culture to develop a typology of strategic reorientations. The four types of strategic reorientations are illustrated with the help of published cases and biographies of CEOs, mostly of high visibility international companies such as Heineken, Burger King and Starbucks.FindingsCombinations of high and low levels of executive team consensus on its external adaptation tasks and on its internal integration tasks provoke four different types of strategic reorientations: chaotic, negotiated, muted and promising.Research limitations/implicationsUntil appropriate methods of empirical research can be found to test this framework, one has to rely on some anecdotal support as preliminary and cursory evidence. This study can inform a wide body of research which incorrectly suggested that consensus among executives during strategic reorientation has a unidirectional, positive impact on organizational performance. Directions to explore how top executives may develop ambidextrous leadership are suggested.Practical implicationsSeeking high growth, executive teams must have a good mix of managerial and entrepreneurial cognitions. Therefore, executives having dissimilar skills and backgrounds should be inducted in the team periodically, instead of hiring hurriedly at the eleventh hour. Otherwise, the new executives may contribute too high or too low levels of consensus of each type needed for optimal strategic reorientation.Social implicationsThe paper has not attempted this aspect.Originality/valueThis paper contributes a novel framework that combines two streams of seminal research, which, each by itself, would not sufficiently address the unresolved executive paradox.

Analysis of balance beam deformation in the inertial mass measurement experiment

This paper provides an analysis of mechanical balance beam deformation in the inertial mass measurement experiment since 2012. The relation between the applied test masses and three types of mechanical elastic deformation of the balance beam, i.e. the changes of rotational inertia, beam length and mass center, are discussed. It is found that changes in the rotational inertia and beam length are high order small quantities of the test mass, and a mechanically optimized balance beam which has good mechanical strength and a light structure is adopted to decrease the influence of the two types of deformation. The mass center change, being proportional to the test mass, has the most impact and can be compensated by a novel mass center compensation approach. Simulations and experiments confirm the effectiveness of the new balance beam and the mass center compensation method. It is emphasized that the analysis of the beam deformation in this paper can also be applied in other experiments where mechanical deformation of the balance beam needs to be considered.

The Co-Evolution of Institutional Logics and Boundary Spanning in Sustainability Transitions: the Case of Urban Stormwater Management in Melbourne, Australia

Institutions and actors both play a critical role in sustainability transitions, yet they have never been investigated together. This study combines both dimensions, systematically applying an institutional logics and boundary spanning lens to examine the interplay between structure and agency over the course of a particular system innovation: the case of urban stormwater management in Melbourne, Australia. Looking through this dual lens reveals the socio-institutional patterns and mechanisms that determine inertia and practice change in the urban stormwater management system. We found that structure and agency co-evolve; when their relationship changes, the dynamics between boundary spanning and institutional logics change too – as do the corresponding niche and regime developments. Our findings suggest that even radical innovations can be successfully institutionalized when using certain forms of boundary spanning at specific phases of a system innovation.

“TNOs are Cool”: A survey of the trans-Neptunian region

Time series observations of the dwarf planet Haumea and the Plutinos 2003VS2 and 2003AZ84 with Herschel/PACS are presented in this work. Thermal emission of these trans-Neptunian objects were acquired as part of the TNOs are Cool Herschel Space Observatory key programme. We search for the thermal light curves at 100 and 160um of Haumea and 2003AZ84, and at 70 and 160um for 2003VS2 by means of photometric analysis of the PACS data. The goal of this work is to use these thermal light curves to obtain physical and thermophysical properties of these icy Solar System bodies. Haumea's thermal light curve is clearly detected at 100 and 160um. The effect of the reported dark spot is apparent at 100um. Different thermophysical models were applied to these light curves, varying the thermophysical properties of the surface within and outside the spot. Although no model gives a perfect fit to the thermal observations, results imply an extremely low thermal inertia (< 0.5 MKS) and a high phase integral (> 0.73) for Haumea's surface. We note that the dark spot region appears to be only weakly different from the rest of the object, with modest changes in thermal inertia and/or phase integral. The thermal light curve of 2003VS2 is not firmly detected at 70 and at 160um but a thermal inertia of 2+/-0.5 MKS can be derived from these data. The thermal light curve of 2003AZ84 is not firmly detected at 100um. We apply a thermophysical model to the mean thermal fluxes and to all the Herschel/PACS and Spitzer/MIPS thermal data of 2003AZ84, obtaining a close to pole-on orientation as the most likely for this TNO. For the three TNOs, the thermal inertias derived from light curve analyses or from the thermophysical analysis of the mean thermal fluxes confirm the generally small or very small surface thermal inertias of the TNO population, which is consistent with a statistical mean value of 2.5+/-0.5 MKS.

Anharmonicity of Coupled Torsions: The Extended Two-Dimensional Torsion Method and Its Use To Assess More Approximate Methods.

In this work we present the extended two-dimensional torsion (E2DT) method and use it to analyze the performance of several methods that incorporate torsional anharmonicity more approximately for calculating rotational-vibrational partition functions. Twenty molecules having two hindered rotors were studied for temperatures between 100 and 2500 K. These molecules present several kinds of situations; they include molecules with nearly separable rotors, molecules in which the reduced moments of inertia change substantially with the internal rotation, and molecules presenting compound rotation. Partition functions obtained by the rigid-rotor harmonic oscillator approximation, a method involving global separability of torsions and the multistructural methods without explicit potential coupling [MS-T(U)] and with explicit potential coupling [MS-T(C)] of torsions, are compared to those obtained with a quantized version - called the extended two-dimensional torsion (E2DT) method - of the extended hindered rotor approximation of Vansteenkiste et al. ( Vansteenkiste et al. J. Chem. Phys. 2006 , 124 , 044314 ). In the E2DT method, quantum effects due to the torsional modes were incorporated by the two-dimensional nonseparable method, which is a method that is based on the solution of the torsional Schrödinger equation and that includes full coupling in both the kinetic and potential energy. By comparing other methods to the E2DT method and to experimental thermochemical data, this study concludes that the harmonic approximation yields very poor results at high temperatures; the global separation of torsions from the rest of the degrees of freedom is not justified even when an accurate method to treat the torsions is employed; it is confirmed that methods based on less complete potential energy coupling of torsions, such as MS-T(U), are not accurate when dealing with rotors with different barrier heights, and more complete inclusion of torsional coupling to the method in MS-T(C) improves substantially the results in such a way that it could be used in cases where the E2DT method is unaffordable.

Simulation of variable impedance as an intervention for upper extremity motor exploration.

Current methods in robot-assisted therapy are limited in providing predictions of the effectiveness of interventions. Our approach focuses on how robotic interaction can impact the distribution of movements expressed in the arm. Using data from a previous study with stroke survivors (n=10), we performed simulations to examine how changes in hand endpoint impedance would alter exploratory motion. We present methods for designing a custom training intervention, by relating the desired change in acceleration covariance in planar motion with a corresponding change in inertia matrix. We first characterized motor exploration in terms of overall covariance in acceleration, and secondly as covariance that varies with position in the workspace. Using a forward dynamics simulation of the hand endpoint impedance, we found that the variable change in endpoint inertia resulted in better recovery of acceleration covariance compared to the fixed change in inertia method. These results could significantly impact rehabilitation firstly in terms of design principles for altering coordination patterns through direct assistance. Furthermore, our work might serve to improve therapy by facilitating access to repeated practice of independent joint motion.