Hybrid disturbance rejection control of dynamic bipedal robots

Falls are a major issue for bipeds. For elderly adults, falls can have a negative impact on their quality of life and lead to increased medical costs. Fortunately, interventional methods are effective at reducing falls assuming they are prescribed. For biped robots, falls prevent them from completing required tasks. Thus, it is important to understand what aspects of gait increase fall risk. Gait variability may be associated with increased fall risk; however, previous studies have not investigated the variation in the movement of the legs. The purpose of this study was to determine the effect of joint angle variability on falling to determine which component(s) of variability were statistically significant. In order to investigate joint angle variability, a physics-based simulation model that captured joint angle variability as a function of time through Fourier series was used. This allowed the magnitude, the frequency mean, and the frequency standard deviation of the variability to be altered. For the values tested, results indicated that the magnitude of the variability had the most significant impact on falling, and specifically that the stance knee flexion variability magnitude was the most significant factor. This suggests that increasing the joint variability magnitude may increase fall risk, particularly if the controller is not able to actively compensate. Altering the variability frequency had little to no effect on falling.

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“…Another source of falls is movement variability caused by noise within the system. Both humans [ 23 ] and robots [ 24 , 25 ] experience this.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the effect of sagittal plane joint angle variability on bipedal fall risk

Mitchell

Martin

2022

PLoS ONE

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“…Without a proper rejection, such uncertainties and disturbances would significantly affect the proper operation of the ventilator. The ADRC strategy has been successfully utilized in the control of walking robots [24]. The implementation in a low-cost, bag valve-based mechanical ventilator design is described in this paper.…”

Section: Mechanicalmentioning

confidence: 99%

“…In order to provide robustness to the control of continuous dynamics against unknown model uncertainties and external disturbances, an ADRC-based tracking is implemented in this work. ADRC-based tracking has been successfully utilized in the control of other dynamic systems including walking robots [24,30,31]. The ADRC-based tracking collects both endogenous disturbances (strap tension loss, manufacturing variability) and exogenous disturbances (external disturbances, breathing irregularity) into a lumped signal referred to as the total disturbance.…”

Section: Active Disturbance Rejection Controlmentioning

confidence: 99%

Mechatronic Design and Active Disturbance Rejection Control of a Bag Valve-Based Mechanical Ventilator

Arcos-Legarda

Tovar

2021

Journal of Medical Devices

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This paper presents the mechatronic (mechanical and control system) design of a portable mechanical ventilator to treat patients with a compromised respiratory function. The portable ventilator ensures adequate oxygenation and carbon dioxide clearance while avoiding ventilator-associated lung injury (VALI). Oxygen is delivered through the compression of a bag valve (Ambu bag) using a moving strap. Carbon dioxide is cleared through the control of a pinch valve actuated by a low-torque servo motor. The positive end expiratory pressure (PEEP) is controlled by an adjustable mechanical valve the system. An Arduino Mega microcontroller board is used in this prototype to control the respiratory variables. All mechanical components as well as sensors, actuators and control hardware are of common use in robotics and are very inexpensive. The total cost of the prototype build in this work is about $425 U.S. dollars. The design is meant to be replicated and utilized in emergency conditions that involve an overwhelming number of cases, such as COVID-19 treatment, in places with no access to commercial MV technologies. In order to account for variations in the prototype as built, the software developed for this portable MV applies an active disturbance rejection control strategy (ADRC). This control strategy is presented as a universal control structure for any mechanical ventilator able to supply air flow with controlled pressure and volume.

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“…Environment and model disturbances are common contributors to these systems’ tip-over instability (rotational and postural) Goswami and Kallem (2004) , which can lead to complete loss or severe damages to the system. Because of the inherent complexity of disturbance rejection, a handful of mainstream strategies have been successfully applied to solve such a vulnerability Gubina et al (1974) ; Pratt and Tedrake (2006) ; Kajita and Tani (1991) ; Hill and Fahimi (2015) ; Mandava and Vundavilli (2018) ; Song et al (2018) ; Arcos-Legarda et al (2019) . None of these strategies have been able to mitigate tip-over scenarios entirely.…”

Section: Introductionmentioning

confidence: 99%

Control of Thruster-Assisted, Bipedal Legged Locomotion of the Harpy Robot

2021

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Fast constraint satisfaction, frontal dynamics stabilization, and avoiding fallovers in dynamic, bipedal walkers can be pretty challenging. The challenges include underactuation, vulnerability to external perturbations, and high computational complexity that arise when accounting for the system full-dynamics and environmental interactions. In this work, we study the potential roles of thrusters in addressing some of these locomotion challenges in bipedal robotics. We will introduce a thruster-assisted bipedal robot called Harpy. We will capitalize on Harpy’s unique design to propose an optimization-free approach to satisfy gait feasibility conditions. In this thruster-assisted legged locomotion, the reference trajectories can be manipulated to fulfill constraints brought on by ground contact and those prescribed for states and inputs. Unintended changes to the trajectories, especially those optimized to produce periodic orbits, can adversely affect gait stability and hybrid invariance. We will show our approach can still guarantee stability and hybrid invariance of the gaits by employing the thrusters in Harpy. We will also show that the thrusters can be leveraged to robustify the gaits by dodging fallovers or jumping over large obstacles.

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Hybrid disturbance rejection control of dynamic bipedal robots

Cited by 12 publications

References 37 publications

Quantifying the effect of sagittal plane joint angle variability on bipedal fall risk

Quantifying the effect of sagittal plane joint angle variability on bipedal fall risk

Mechatronic Design and Active Disturbance Rejection Control of a Bag Valve-Based Mechanical Ventilator

Control of Thruster-Assisted, Bipedal Legged Locomotion of the Harpy Robot

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