Braided Pneumatic Actuators Research Articles

Adaptive back stepping fast terminal sliding mode control of robot manipulators actuated by pneumatic artificial muscles: continuum modelling, dynamic formulation and controller design

Pneumatic Artificial Muscles (PAMs) also called braided pneumatic actuators were invented by Mckibben to help the Polio patients. When the internal bladder is pressurized the actuator gets shorter which can produce a tensile force. PAMs are widely used in bio robotic as well as industrial, medical and rehabilitation robotic applications due to their salient advantages such as high power to weight ratio, flexibility and low cost. However, PAMs exhibit highly non-linear characteristics due to nonlinear mechanical properties of the inner tube and geometrically complex behavior of the outer shell. To use PAMs in engineering applications it is necessary to have an accurate relationship between produced axial force, contraction ratio and applied internal pressure. In this work, a continuum mechanics based model is extended to calculate actuation force of PAMs which is essential in calculation of the required internal pressure as the input signal for control of PAM-based systems. Moreover, dynamic model of a 2-link robot manipulator actuated by PAMs is presented and an adaptive back stepping fast terminal sliding mode controller is applied. Robustness of the utilized method against external disturbances and parameter uncertainties is also investigated. Comparing the model results with experimental data, it is observed the model well predicts mechanical behavior of PAMs. Furthermore, positions and tracking errors are compared with results of an adaptive sliding mode controller. Simulation results obviously demonstrate fast and accurate tracking performance of the applied controller. The developed model can be widely used in design of rehabilitation and also industrial robotic systems.

New Exoskeleton Arm Concept Design And Actuation For Haptic Interaction With Virtual Objects

Abstract In the work presented in this paper the conceptual design and actuation of one new exoskeleton of the upper limb is presented. The device is designed for application where both motion tracking and force feedback are required, such as human interaction with virtual environment or rehabilitation tasks. The choice is presented of mechanical structure kinematical equivalent to the structure of the human arm. An actuation system is selected based on braided pneumatic muscle actuators. Antagonistic drive system for each joint is shown, using pulley and cable transmissions. Force/displacement diagrams are presented of two antagonistic acting muscles. Kinematics and dynamic estimations are performed of the system exoskeleton and upper limb. Selected parameters ensure in the antagonistic scheme joint torque regulation and human arm range of motion.

Static Modeling for Commercial Braided Pneumatic Muscle Actuators

An enhanced model is proposed to describe static property of commercial braided pneumatic muscle actuators by including several important influencing factors. Elasticity of elastomer tube is considered and Ogden strain energy function is employed to describe its strain energy density. During pressurized process, small deformation of fiber occurs and is calculated using force balancing principle. Frictional forces within muscles are studied, which consist of friction within braid and that between bladder and braid. Isobaric experiments are performed and results verify the validity of the model.

Biologically inspired damage tolerance in braided pneumatic muscle actuators

As the operation of robotic systems moves away from solely manufacturing environments to arenas where they must operate alongside humans, so the essential characteristics of their design has transformed. A move from traditional robot designs to more inherently safe concepts is required. Studying biological systems to determine how they achieve safe interactions is one approach being used. This then seeks to mimic the ingredients that make this interaction safe in robotics systems. This is often achieved through softness both in terms of a soft fleshy external covering and through motor systems that introduce joint compliance for softer physical Human-Robot Interaction (pHRI). This has led to the development of new actuators with performance characteristics that at least on a macroscopic level try to emulate the function of organic muscle. One of the most promising among these is the pneumatic Muscle Actuator (pMA). However, as with organic muscle, these soft actuators are more susceptible to damage than many traditional actuators. Whilst organic muscle can regenerate and recover, artificial systems do not possess this ability. This article analyzes how organic muscle is able to operate even after extreme trauma and shows how functionally similar techniques can be used with pMAs.

Enhanced Modelling and Performance in Braided Pneumatic Muscle Actuators

Pneumatic technology has been successfully applied for over two millennia. Even today, pneumatic cylinder based technology forms the keystone of many manufacturing processes where there is a need for simple, high-speed, low-cost, reliable motion. But when the system requires accurate control of position, velocity or acceleration profiles, these actuators form a far from satisfactory solution. Braided pneumatic muscle actuators (pMAs) form an interesting development of the pneumatic principle offering even higher power/weight performance, operation in a wide range of environments and accurate control of position, motion and force. This technology provides an interesting and potentially very successful alternative actuation source for robots as well as other applications. However, there are difficulties with this approach due to the following.(i)Modeling errors. Models of the force response are still nonoptimal and for good results these models are highly complex, which makes accurate design difficult.(ii)Low bandwidth—the bandwidth of the actuator—link assemblies are often considered to be too low for practical success in many applications, particularly robotics.In this paper we address these limitations and show how the performance in each area can be enhanced with overall improvements in the response and utility of the braided pMAs.