Sliding Mode Impedance Control of a Hydraulic Artificial Muscle

2018 ◽  
Author(s):  
Jonathon E. Slightam ◽  
Mark L. Nagurka ◽  
Eric J. Barth
Keyword(s):  
Sliding Mode ◽  
Impedance Control ◽  
Artificial Muscle ◽  
Lumped Parameter Model ◽  
Superior Performance ◽  
Specific Power ◽  
Artificial Muscles ◽  
Control Approach ◽  
Model Based ◽  
Improved Performance

Hydraulic artificial muscles offer unrivaled specific power and power density and are instrumental to the improved performance and success of soft robotics and lightweight mobile applications. This paper addresses the lack of model-based impedance control approaches for soft actuators such as hydraulic artificial muscles. Impedance control of actuators and robotic systems has been proven to be an effective approach for interacting with physical objects in the presence of uncertainty. A sliding mode impedance control approach based on Filippov’s principle of equivalent dynamics is introduced and applied to a hydraulic artificial muscle. A nonlinear lumped parameter model of the system is presented and a sliding mode impedance controller is derived. Experimental results show superior performance using model-based sliding mode impedance control versus a linear impedance control law in both tracking of position and stiffness when disturbances are introduced.

Design and Control of a Compact and Flexible Pneumatic Artificial Muscle Actuation System: Part Two—Robust Control

2011 ◽  
Author(s):  
Sai-Kit Wu ◽  
Garrett Waycaster ◽  
Tad Driver ◽  
Xiangrong Shen
Keyword(s):  
Robust Control ◽  
Nonlinear Model ◽  
Sliding Mode ◽  
Artificial Muscle ◽  
Control Approach ◽  
Actuation System ◽  
Highly Nonlinear ◽  
Pressure Dynamics ◽  
System Part ◽  
And Control

A robust control approach is presented in this part of the paper, which provides an effective servo control for the novel PAM actuation system presented in Part I. Control of PAM actuation systems is generally considered as a challenging topic, due primarily to the highly nonlinear nature of such system. With the introduction of new design features (variable-radius pulley and spring-return mechanism), the new PAM actuation system involves additional nonlinearities (e.g. the nonlinear relationship between the joint angle and the actuator length), which further increasing the control difficulty. To address this issue, a nonlinear model based approach is developed. The foundation of this approach is a dynamic model of the new actuation system, which covers the major nonlinear processes in the system, including the load dynamics, force generation from internal pressure, pressure dynamics, and mass flow regulation with servo valve. Based on this nonlinear model, a sliding mode control approach is developed, which provides a robust control of the joint motion in the presence of model uncertainties and disturbances. This control was implemented on an experimental setup, and the effectiveness of the controller demonstrated by sinusoidal tracking at different frequencies.

Contractile Pneumatic Artificial Muscle Configured to Generate Extension

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Benjamin K. S. Woods ◽  
Shane M. Boyer ◽  
Erica G. Hocking ◽  
Norman M. Wereley ◽  
Curt S. Kothera
Keyword(s):  
Compressive Loading ◽  
Compressive Force ◽  
Artificial Muscle ◽  
Specific Power ◽  
Artificial Muscles ◽  
Specific Work ◽  
Operational Characteristics ◽  
Pneumatic Artificial Muscles ◽  
High Specific Power ◽  
Internal Mechanism

Pneumatic artificial muscles (PAMs) are comprised of an elastomeric bladder surrounded by a braided mesh sleeve. When the bladder is inflated, the actuator may either contract or extend axially, with the direction of motion dependent on the orientation of the fibers in the braided sleeve. Contractile PAMs have excellent actuation characteristics, including high specific power, specific work, and power density. Unfortunately, extensile PAMs exhibit much reduced blocked force, and are prone to buckling under axial compressive loading. For applications in which extensile motion and compressive force are desired, the push-PAM actuator introduced here exploits the operational characteristics of a contractile PAM, but changes the direction of motion and force by employing a simple internal mechanism using no gears or pulleys. Quasi-static behavior of the push-PAM was compared to a contractile PAM for a range of operating pressures. Based on these data, the push-PAM actuator can achieve force and stroke comparable to a contractile PAM tested under the same conditions.

scholarly journals Safety-enhanced control strategy of a power soft robot driven by hydraulic artificial muscles

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Yunhao Feng ◽  
Tohru Ide ◽  
Hiroyuki Nabae ◽  
Gen Endo ◽  
Ryo Sakurai ◽  
...  
Keyword(s):  
Control Strategy ◽  
Impedance Control ◽  
Artificial Muscle ◽  
Dynamic Compliance ◽  
Artificial Muscles ◽  
Soft Robot ◽  
Compliant Structure ◽  
Safety Features ◽  
Muscle Actuators ◽  
Sudden Load

AbstractPower soft robots—defined as novel robots driven by powerful soft actuators, achieving both powerfulness and softness—are potentially suitable for complex collaborative tasks, and an approach to actuating a power soft robot is the McKibben artificial muscle. This study aims to show the potential of hydraulic artificial muscles to be implemented in a power soft robot with high safety, including higher stability against sudden load separation or impact disturbance, and appropriate dynamic compliance. The stability of a manipulator arm driven by hydraulic muscle actuators is experimentally proven to be higher than that of pneumatic muscle actuators when the stored elastic energy is instantaneously released. Therefore, the hydraulic muscle actuator is a better candidate for actuating a power soft robot. By taking advantage of the incompressible liquid medium and the compliant structure of a hydraulic muscle, a second-order impedance control strategy with a braking method is proposed to improve dynamic compliance without sacrificing the safety features of hydraulic muscles. The results show that the manipulator can be easily shifted by a several-kilogram-level external force and react safely against sudden load change with low angular velocity by the proposed impedance control.

A Lyapunov Approach for SOSM Based Velocity Estimation and Its Application to Improve Bilateral Teleoperation Performance

2011 ◽  
Author(s):  
Vinay Chawda ◽  
Marcia K. O’Malley
Keyword(s):  
Sliding Mode ◽  
Velocity Estimation ◽  
Superior Performance ◽  
Bilateral Teleoperation ◽  
Integral Control ◽  
Loop Control ◽  
Control Approach ◽  
Estimation Scheme ◽  
Proportional Integral Control ◽  
Small Disturbances

In many mechatronic applications, velocity estimation is required for implementation of closed loop control. Proportional-Integral control based differentiation has been proposed to estimate velocity in bilateral teleoperation. We propose a Second Order Sliding Mode (SOSM) based velocity estimation scheme for this application, since the SOSM approach is robust to small disturbances near the origin. Simulation results demonstrate the superior performance of the SOSM based velocity estimation over the PI-control approach for bilateral teleoperation in viscous environments. Additionally, a novel Lyapunov function based approach to stability analysis of the SOSM based differentiator is presented.

Sliding Mode Hybrid Impedance Control of Robot Manipulators Interacting With Unknown Environments Using VSMRC Method

2012 ◽  
Author(s):  
Aghil Jafari ◽  
Reza Monfaredi ◽  
Mehdi Rezaei ◽  
Ali Talebi ◽  
Saeed Shiry Ghidary
Keyword(s):  
Control System ◽  
Hybrid Control ◽  
Sliding Mode ◽  
Robot Manipulator ◽  
Impedance Control ◽  
Variable Structure ◽  
Structure Model ◽  
Robust Controller ◽  
Control Approach ◽  
Chattering Effect

In the present paper, the objective of hybrid impedance control is specified and a robust hybrid impedance control approach is proposed. Based on the concept of hybrid control, the task space is decomposed into position and force controlled subspaces. Impedance control is used in the position controlled subspace. Desired inertia and damping are applied in the force controlled subspace to meliorate the dynamic behavior of robot manipulator. Robust controller using the variable structure model reaching control (VSMRC) is introduced that can realize the objective impedance in the sliding mode in finite time. In order to overcome the chattering effect due to sliding mode approach, fuzzy logic methodology is employed in the control system. In addition, the reaching transient response is undertaken with prescribed quality. Simulating the control system for a 6DOF PUMA560 robot confirms the validity and effectiveness of the proposed control system.

Model Based Analysis and Control Design of a Urea-SCR deNOx Aftertreatment System

2005 ◽  
Vol 128 (3) ◽  
pp. 737-741 ◽  
Author(s):  
Devesh Upadhyay ◽  
Michiel Van Nieuwstadt
Keyword(s):  
Sliding Mode ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Control Design ◽  
Observer Design ◽  
Lumped Parameter Model ◽  
Control Synthesis ◽  
Model Based ◽  
Ammonia Slip ◽  
Controllability And Observability

In this paper we tackle issues relevant to model based control design for a Urea based Selective Catalytic Reduction (SCR) process relevant to automotive applications. A three state, control oriented, lumped parameter model of the system is used to investigate essential controllability and observability properties of the Urea-SCR plant. Results from the controllability and observability analysis of both nonlinear and linearized models are shown to have realistic implications. Observer design for predicting gas phase ammonia slip is outlined and results presented. An altered definition of the catalyst efficiency is used in control design. It is shown that this altered definition lends itself readily to control synthesis in the Sliding Mode framework while satisfying the dual control objectives of maximizing NOx reduction and minimizing ammonia slip.

On the Control of a Dielectric Elastomer Artificial Muscle With Variable Impedance

2013 ◽  
Author(s):  
Gianluca Palli ◽  
Giovanni Berselli
Keyword(s):  
Artificial Muscle ◽  
Artificial Muscles ◽  
Control Law ◽  
Model Uncertainties ◽  
Control Approach ◽  
Task Requirements ◽  
Linear Viscoelastic ◽  
Compensation Technique ◽  
Novel Strategy ◽  
Actuation Systems

Artificial Muscles based on Dielectric Elastomers (DE) can potentially enable the realization of bio-inspired actuation systems whose intrinsic compliance and damping can be varied according to the task requirements. Nonetheless, the control of DE-based Variable Impedance Actuators (VIA) is not trivial owing to the non-linear viscoelastic response which characterizes the acrylic dielectrics commonly employed in practical devices. In this context, the purpose of the present paper is to outline a novel strategy for the control of DE-based VIA. Although the proposed methodology is applicable to generic DE morphologies, the considered system is composed of a couple of conically-shaped DE films in agonistic-antagonistic configuration. Following previously published results, the system dynamic model is firstly recalled. Then, a DE viscoelasticity compensation technique is outlined together with a control law able to shape the DE actuator impedance as desired. The operative limits of the system are explicitly considered and managed in the controller by increasing the operating DE actuator stiffness if required. In addition, the problem of model uncertainties compensation is also addressed. Finally, as a preliminary step towards the realization of a practical DE-based VIA, the proposed control approach is validated by means of simulations.

Bioinspired passive variable recruitment of fluidic artificial muscles

2018 ◽  
Vol 29 (15) ◽  
pp. 3067-3081 ◽  
Author(s):  
Edward M Chapman ◽  
Matthew Bryant
Keyword(s):  
Control Method ◽  
Applied Pressure ◽  
Artificial Muscle ◽  
High Threshold ◽  
Artificial Muscles ◽  
Control Approach ◽  
Muscle Tissues ◽  
Wide Range ◽  
Variable Recruitment ◽  
Analogous Behavior

This article presents a novel, passive approach to creating variable actuator recruitment in bundles of fluidic artificial muscles. The passive recruitment control approach is inspired by the functionality of mammalian muscle tissues, in which a single activation signal from the nervous system sequentially triggers contraction of progressively larger actuation elements until the required force is generated. Biologically, this behavior is encoded by differences in electrical resistance properties between smaller and larger muscle-fiber groups. The approach presented here produces analogous behavior using a uniform applied pressure to all fluidic artificial muscles while creating differential pressure responses and threshold pressures among the fluidic artificial muscles via tailored bladder elasticity parameters. A model for using elastic bladder stiffness to control an artificial muscle bundle with a single valve is explored and used to compare a bundle of fluidic artificial muscles with both low and high threshold pressure units to a single fluidic artificial muscle of equivalent displacement and force capability. The results of this analysis indicate the efficacy of using this control method; it is advantageous in cases where a wide range of displacements and forces are necessary and can increase efficiency when the system primarily operates in a low-force regime but requires occasional bursts of high-force capability.

A Pneumatic Artificial Muscle Actuated Above-Knee Prosthesis

2010 ◽  
Author(s):  
Garrett Waycaster ◽  
Sai-Kit Wu ◽  
Xiangrong Shen
Keyword(s):  
Sliding Mode ◽  
Mechanical Design ◽  
Knee Prosthesis ◽  
Artificial Muscle ◽  
Torque Control ◽  
Stair Climbing ◽  
Pneumatic Artificial Muscle ◽  
Control Approach ◽  
Energy Consuming ◽  
And Control

This paper describes the mechanical design and control approach for an above-knee (AK) prosthesis actuated by pneumatic artificial muscle. Pneumatic artificial muscle (PAM) affords great potential in prosthetics, since this type of actuator features a high power density, and similar characteristics to human muscles. However, there is no application of PAM in AK prosthetics in existing literature to the best knowledge of the authors. In this paper, a design of the prosthesis is presented, which provides sufficient actuation torque for the knee joint in energy consuming locomotive functions such as fast walking and stair climbing. The corresponding control approach is also presented, which combines an impedance-based locomotive controller with a lower-level sliding-mode torque control approach. Experiments on the proposed AK prosthesis have also been conducted to demonstrate the ability to mimic normal gait characteristics.

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