Linear Parameter Varying Identification of Dynamic Joint Stiffness during Time-Varying Voluntary Contractions

  title={Linear Parameter Varying Identification of Dynamic Joint Stiffness during Time-Varying Voluntary Contractions},
  author={Mahsa A. Golkar and Ehsan Sobhani-Tehrani and Robert E. Kearney},
  journal={Frontiers in Computational Neuroscience},
Dynamic joint stiffness is a dynamic, nonlinear relationship between the position of a joint and the torque acting about it, which can be used to describe the biomechanics of the joint and associated limb(s). This paper models and quantifies changes in ankle dynamic stiffness and its individual elements, intrinsic and reflex stiffness, in healthy human subjects during isometric, time-varying (TV) contractions of the ankle plantarflexor muscles. A subspace, linear parameter varying, parallel… 

Comparison of time-varying systemidentification methods to assess jointimpedance by Sven Kraaijevanger

Joint impedance describes the dynamic resistance of a joint in response to position perturbations. Joint impedance is known to vary nonlinearly during movement caused by varying joint angle and

Unbiased Estimation of Human Joint Intrinsic Mechanical Properties During Movement

Simulation results demonstrate that the new approach accurately tracks time-varying joint intrinsic mechanical properties during movement independently of the reflex torque magnitude, and will be a useful tool in the study of motor control, as it supports the unbiased estimation of joint intrinsic mechanics during movement in the presence of reflex torques.

Modeling Ankle Torque and Stiffness Induced by Functional Electrical Stimulation

The proposed model can modulate both joint torque and stiffness induced by FES in the isometric condition, which can be potentially extended to modulate the joint velocity and stiffness during FES-assisted walking.

Single-trial estimation of quasi-static EMG-to-joint-mechanical-impedance relationship over a range of joint torques.

Ankle intrinsic stiffness changes with postural sway.

Patterns of Muscle Activation and Modulation of Ankle Intrinsic Stiffness in Different Postural Operating Conditions.

It is demonstrated that ankle intrinsic stiffness varies widely, from 0.08 to 0.75 of critical stiffness, across postural operating condition; however, it is always smaller than the critical stiffness; therefore, other contributions are necessary to ensure stable standing.

Simplified Optimal Estimation of Time-Varying Electromyogram Standard Deviation (EMGσ): Evaluation on Two Datasets

From the constant-force tasks, it was found that noise correction via the root difference of squares (RDS) method consistently reduced EMG recording noise, and the first difference is an excellent whitening option over this range of contraction forces since no calibration or algorithm decisions are required.

Neurophysiological validation of simultaneous intrinsic and reflexive joint impedance estimates

A group-level neurophysiological validation of the parallel-cascade system identification technique using electromyography (EMG) measurements shows the validity of the use of the technique for the integrated assessment and training of people with joint hyper-resistance in clinical practice.

Simplified Optimal Estimation of Time-Varying Electromyogram Standard Deviation (EMGσ)

  • K. RajotteHe Wang E. Clancy
  • Engineering
    2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC)
  • 2020
Traditional and universal whitening provided the same EMG-torque benefit, each improving statistically over unwhitened processing by ~14% during dynamic contractions, which should be a particular benefit in real-time applications such as prosthesis control.

EMG-Force and EMG-Target Models During Force-Varying Bilateral Hand-Wrist Contraction in Able-Bodied and Limb-Absent Subjects

The no-feedback model output of EMG-force was not acceptable because of little performance variation between DoFs, and many subjects struggled to perform 2-DoF target tracking.



Linear parameter varying identification of ankle joint intrinsic stiffness during imposed walking movements

Experimental results demonstrate that the method accurately tracks the continuous-time variation of normal ankle intrinsic stiffness when the joint position changes during the IW movement.

Identification of time-varying stiffness dynamics of the human ankle joint during an imposed movement

It was found that stiffness actually increased during the later portion of the large imposed stretch, indicating the triceps surae muscles did not yield significantly, and that the post-stretch steady-state stiffness level was approximately 60% higher than prior to the stretch.

Time-varying stiffness of human elbow joint during cyclic voluntary movement

Overall, the moving arm was found to be very compliant, with a peak stiffness value less than the lowest value measured during posture, and a natural frequency of less than 3 Hz.

Identification of ankle joint stiffness during passive movements — A subspace linear parameter varying approach

The identification results demonstrated that (a) the dynamic response of the intrinsic pathway changes systematically with joint position; and (b) the static nonlinearity of the reflex pathway resembles a half-wave rectifier whose threshold decreases and gain increases as ankle is moved to dorsiflexed position.

Time-varying identification of ankle dynamic joint stiffness during movement with constant muscle activation

  • D. GuarínR. Kearney
  • Biology, Engineering
    2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
  • 2015
A novel, nonlinear, dynamic joint stiffness model is formulated and a new algorithm is presented to estimate its parameters, assuming that the variability in the model parameters is a function of the mean joint position.

Identification of time-varying dynamics of reflex EMG in the ankle plantarflexors during time-varying, isometric contractions

The LPV-Hammerstein method can be used to study stretch reflexes in subjects with neuromuscular disorders and demonstrated a systematic change in the reflex nonlinearity with the activation level.

Position dependence of ankle joint dynamics--I. Passive mechanics.

Position dependence of ankle joint dynamics--II. Active mechanics.

Ankle Joint Intrinsic Dynamics is More Complex than a Mass-Spring-Damper Model

It is found that intrinsic ankle mechanics is a third-order system and the second-order mass-spring-damper model, referred to as IBK, used by many researchers in the literature cannot adequately represent ankle dynamics at all frequencies in a number of important tasks.

Identification of intrinsic and reflex contributions to human ankle stiffness dynamics

It is concluded that reflex stiffness can be large enough to be important functionally, but that its effects will depend strongly upon the particular conditions.