Intermittent control of unstable multivariate systems with uncertain system parameters

Loram, Ian D.; Cunningham, Ryan; Zenzeri, Jacopo; Gollee, H.

doi:10.1109/embc.2016.7590629

Cited by 4 publications

(5 citation statements)

References 13 publications

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“…To isolate the effect of the action generated at short latency, a medium-latency EMG response starting at 100 msec was also excluded. We confirm that inclusion of time delayed (0.1 sec), continuous optimal feedback control Loram et al 2015Loram et al , 2016 was investigated, and excluded from this illustration as the demonstration points were unaltered. ª 2017 The Authors.…”

Section: Control Actionsupporting

confidence: 55%

“…This analysis uses a previously published model, which represents the standing human as a three-segment model with a head and trunk segment (HAT), a thigh and a shank segment Loram et al 2015Loram et al , 2016. Mechanical segment properties (link mass, length, centre of mass location, radius of gyration) are taken from Winter (2009).…”

Section: Mechanical Systemmentioning

confidence: 99%

“…Mechanical segment properties (link mass, length, centre of mass location, radius of gyration) are taken from Winter (2009). To simplify exposition of effects we used passive springs of 100% gravitational stiffness, which by definition eliminates the gravitational effect on segment rotations from the vertical Loram et al 2015Loram et al , 2016. All simulations began with zero link angle from the vertical and zero velocity for all segments.…”

Section: Mechanical Systemmentioning

confidence: 99%

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The effect of fear of falling on vestibular feedback control of balance

et al. 2017

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Vestibular sensation contributes to cervical‐head stabilization and fall prevention. To what extent fear of falling influences the associated vestibular feedback processes is currently undetermined. We used galanic vestibular stimulation (GVS) to induce vestibular reflexes while participants stood at ground level and on a narrow walkway at 3.85 m height to induce fear of falling. Fear was confirmed by questionnaires and elevated skin conductance. Full‐body kinematics was measured to differentiate the whole‐body centre of mass response (CoM) into component parts (cervical, axial trunk, appendicular short latency, and medium latency). We studied the effect of fear of falling on each component to discern their underlying mechanisms. Statistical parametric mapping analysis provided sensitive discrimination of early GVS and height effects. Kinematic analysis revealed responses at 1 mA stimulation previously believed marginal through EMG and force plate analysis. The GVS response comprised a rapid, anode‐directed cervical‐head acceleration, a short‐latency cathode‐directed acceleration (cathodal buckling) of lower extremities and pelvis, an anode‐directed upper thorax acceleration, and subsequently a medium‐latency anode‐directed acceleration of all body parts. At height, head and upper thorax early acceleration were unaltered, however, short‐latency lower extremity acceleration was increased. The effect of height on balance was a decreased duration and increased rate of change in the CoM acceleration pattern. These results demonstrate that fear modifies vestibular control of balance, whereas cervical‐head stabilization is governed by different mechanisms unaffected by fear of falling. The mechanical pattern of cathodal buckling and its modulation by fear of falling both support the hypothesis that short‐latency responses contribute to regulate balance.

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Section: Control Actionsupporting

confidence: 55%

Section: Mechanical Systemmentioning

confidence: 99%

Section: Mechanical Systemmentioning

confidence: 99%

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The effect of fear of falling on vestibular feedback control of balance

et al. 2017

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“…Consider, for example, the analysis of posturographic patterns (Collins and De Luca, 1993; Morasso and Schieppati, 1999; Morasso and Sanguineti, 2002), EMG signals (Gatev et al, 1999; Loram and Lakie, 2002; Nomura et al, 2013), and the non-uniform character of sway path (Jacono et al, 2004). Several types of neural control have been proposed in recent years: time-delayed feedback with multiplicative noise (Cabrera and Milton, 2002), model predictive controllers with a sensory uncertainty (Mehta and Schaal, 2002; Gawthrop et al, 2011; Loram et al, 2011, 2016; Insperger and Milton, 2014), time-delayed proportional-derivative-acceleration feedback control (Insperger et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Stabilization of a Cart Inverted Pendulum: Improving the Intermittent Feedback Strategy to Match the Limits of Human Performance

Morasso

Nomura

Suzuki

et al. 2019

Front. Comput. Neurosci.

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Stabilization of the CIP (Cart Inverted Pendulum) is an analogy to stick balancing on a finger and is an example of unstable tasks that humans face in everyday life. The difficulty of the task grows exponentially with the decrease of the length of the stick and a stick length of 32 cm is considered as a human limit even for well-trained subjects. Moreover, there is a cybernetic limit related to the delay of the multimodal sensory feedback (about 230 ms) that supports a feedback stabilization strategy. We previously demonstrated that an intermittent-feedback control paradigm, originally developed for modeling the stabilization of upright standing, can be applied with success also to the CIP system, but with values of the critical parameters far from the limiting ones (stick length 50 cm and feedback delay 100 ms). The intermittent control paradigm is based on the alternation of on-phases, driven by a proportional/derivative delayed feedback controller, and off-phases, where the feedback is switched off and the motion evolves according to the intrinsic dynamics of the CIP. In its standard formulation, the switching mechanism consists of a simple threshold operator: the feedback control is switched off if the current (delayed) state vector is closer to the stable than to the unstable manifold of the off-phase and is switched on in the opposite case. Although this simple formulation is effective for explaining upright standing as well as CIP balancing, it fails in the most challenging configuration of the CIP. In this work we propose a modification of the standard intermittent control policy that focuses on the explicit selection of switching times and is based on the phase reset of the estimated state vector at each switching time and on the simulation of an approximated internal model of CIP dynamics. We demonstrate, by simulating the modified intermittent control policy, that it can match the limits of human performance, while operating near the edge of instability.

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“…IC has been extended recently to include the multivariable case, with an emphasis on multi-link unstable models of human standing, 4,6,17 where it has been argued that the open-loop intervals and the impulse-like control signals in IC could benefit adaptive schemes in situations where model uncertainties are present or when the system parameters vary with time. This is based on the idea that the variability caused by the open-loop interval results in events and corresponding control actions that excite the system more often than a controller with less sensorimotor variability, facilitating system identification.…”

Section: Introductionmentioning

confidence: 99%

Event-driven adaptive intermittent control applied to a rotational pendulum

Martin

Gollee

Gawthrop

2023

Proceedings of the Institution of Mechanical Engineers, Part I:

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Intermittent control combines open-loop trajectories with feedback at discrete time instances determined by events. Among other applications, it has recently been used to model quiet standing in humans where the system was assumed to be time-invariant. This article expands this work to the time-variant case by introducing an adaptive intermittent controller that exploits the well-known self-tuning architecture of adaptive control with a Kalman filter to perform online state and parameter estimation. Simulation and experimental results using a rotational inverted pendulum show advantages of the intermittent controllers compared to continuous feedback control since the former can provide persistent excitation due to their internal triggering mechanism, even when no external reference changes or disturbances are applied. Moreover, the results show that the event thresholds of intermittent control can be used to adjust the degree of responsiveness of the adaptation in the system, becoming a tool to balance the trade-off between steady-state performance and flexibility against parametric changes, addressing the stability–plasticity dilemma of adaptation and learning in control.

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Intermittent control of unstable multivariate systems with uncertain system parameters

Abstract: Sensitivity of prediction error to model inaccuracy is potentially an asset facilitating adaptation and supporting the rationale for MIC to combine control with flexibility.

Cited by 4 publications

References 13 publications

The effect of fear of falling on vestibular feedback control of balance

The effect of fear of falling on vestibular feedback control of balance

Stabilization of a Cart Inverted Pendulum: Improving the Intermittent Feedback Strategy to Match the Limits of Human Performance

Event-driven adaptive intermittent control applied to a rotational pendulum

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