Force Control of Series Elastic Actuators-Driven Parallel Robot

Ryu

IEEE Trans. Ind. Electron.

et al. 2021

Self Cite

This article offers a new insight to the achievable stiffness limitation of the impedance control of series elastic actuators (SEAs) by suggesting a comparative analysis of energy ports and passivity control framework at the energy port to enhance the maximum achievable rendered stiffness of SEAs. To this end, it is explored that SEAs have two different port definitions to assess energy and passivity of the system-spring port and load port; and conservatisms for passivity evaluation of two ports are investigated and compared utilizing frequency characteristics. The results reveal that the load port passivity exhibits less conservatism, which allows to render larger achievable stiffness in impedance-controlled SEAs. Moreover, key parameters that determine the passivity characteristic of the SEA impedance control are discovered based on the load port passivity analysis. A novel passivity control framework that incorporates the time-domain passivity observer and the passivity controller is designed utilizing the load port energy monitoring, which offers a less conservative assessment of the systems passivity. Throughout this novel port passivity analysis and the passivity control, it can be achieved to render maximum rendered stiffness of the SEA impedance control much higher than the limitation that has been perceived as the maximum value.

“…The condition in (13) implies that the PC only intervenes when the measured energy is negative, namely, when the passivity is violated.…”

Section: A Po and Pcmentioning

confidence: 99%

Section: Design Of Pc Based On Load Damping Controlmentioning

confidence: 99%

See 1 more Smart Citation

Passivity Controller Based on Load-Side Damping Assignment for High Stiffness Controlled Series Elastic Actuators

Ryu

IEEE Trans. Ind. Electron.

et al. 2021

Self Cite

“…As a result, the torque control of SEAs has gained increasing interest in the past years, e.g., Wyeth [25] proposed a cascade control structure that controls the torque of the actuator by using an inner velocity loop. To control the interactive force between a parallel robot driven by three linear SEAs, Lee et al [26], for instance, proposed a torque control approach that is composed of a joint level force control with disturbance observer and a higher level spatial force control to compensate the interactive force.…”

Section: Related Workmentioning

confidence: 99%

Design, Modelling and Control of Novel Series-Elastic Actuators for Industrial Robots

Fernández

Bargsten

et al. 2020

Actuators

This paper describes data-driven modelling methods and their use for the control of a novel set of series-elastic actuators (SEAs). A set of elastic actuators was developed in order to fulfill the end-user needs for tailored industrial collaborative robot manipulators of different morphologies and payloads. Three different types of elastic actuation were investigated, namely, disc springs, coil springs and torsion bars. The developed algorithms were validated both on single actuators and on a 6-DOF robotic arm composed of such actuators.

“…The above-mentioned systems have freedom in 2 axes, roll and pitch axes orientation (plantar/dorsiflexion and inversion/eversion). However, it has been stated that roll, pitch, and z variables are effective in the balance change by mimicking basic real-life activities [52]. Despite the benefits of the platforms, there is no study conducted in the literature to investigate pressure distribution training and the ability to control APAs and CPAs, accordingly applied force and the reaction time of the patients, and regulate the control strategy of the platform based on such information.…”

Section: Introductionmentioning

confidence: 99%

A 3-DoF robotic platform for the rehabilitation and assessment of reaction time and balance skills of MS patients

Tugce

Hocaoğlu²

2023

PLoS ONE

The central nervous system (CNS) exploits anticipatory (APAs) and compensatory (CPAs) postural adjustments to maintain the balance. The postural adjustments comprising stability of the center of mass (CoM) and the pressure distribution of the body influence each other if there is a lack of performance in either of them. Any predictable or sudden perturbation may pave the way for the divergence of CoM from equilibrium and inhomogeneous pressure distribution of the body. Such a situation is often observed in the daily lives of Multiple Sclerosis (MS) patients due to their poor APAs and CPAs and induces their falls. The way of minimizing the risk of falls in neurological patients is by utilizing perturbation-based rehabilitation, as it is efficient in the recovery of the balance disorder. In light of the findings, we present the design, implementation, and experimental evaluation of a novel 3 DoF parallel manipulator to treat the balance disorder of MS. The robotic platform allows angular motion of the ankle based on its anthropomorphic freedom. Moreover, the end-effector endowed with upper and lower platforms is designed to evaluate both the pressure distribution of each foot and the CoM of the body, respectively. Data gathered from the platforms are utilized to both evaluate the performance of the patients and used in high-level control of the robotic platform to regulate the difficulty level of tasks. In this study, kinematic and dynamic analyses of the robot are derived and validated in the simulation environment. Low-level control of the first prototype is also successfully implemented through the PID controller. The capacity of each platform is evaluated with a set of experiments considering the assessment of pressure distribution and CoM of the foot-like objects on the end-effector. The experimental results indicate that such a system well-address the need for balance skill training and assessment through the APAs and CPAs.