Development of intelligent McKibben actuator

The aim of this study is to develop an intelligent McKibben actuator with an integrated soft displacement sensor inside, so that displacement of this actuator can be controlled without having any extra devices attached. In addition, the high compliance which is a positive feature of the McKibben actuator is still conserved. This paper consists of four main parts. First of all, different types of soft displacement sensors made out of rubber were composed, and tested for their functional characteristics. Secondly, the intelligent McKibben actuator was developed with the soft displacement sensor incorporated within. Then, experiments of the position servo control with a single intelligent McKibben actuator were carried out. At last a robot arm mechanism was designed with two intelligent McKibben actuators, and those experimental results showed a great potential for its future applications.</p

The design, kinematics and torque analysis of the self-bending soft contraction actuator

This article presents the development of a self-bending contraction actuator (SBCA) through analysis of its structure, kinematics, and torque formulas, and then explores its applications. The proposed actuator has been fabricated by two methods to prove the efficiency of the human body inspiration, which represents the covering of human bones by soft tissues to protect the bone and give the soft texture. The SBCA provides bending behaviour along with a high force to-weight ratio. As with the simple pneumatic muscle actuator (PMA), the SBCA is soft and easy to implement. Both the kinematics and the torque formula presented for the SBCA are scalable and can be used with different actuator sizes. The bending actuator has been tested under an air pressure up to 500 kPa, and the behaviour of its bending angle, parameters, dimensions, and the bending torques have been illustrated. On the other hand, the experiments showed the efficient performances of the actuator and validate the proposed kinematics. Therefore, the actuator can be used in many different applications, such as soft grippers and continuum arms

Development of a SMA-fishing-line-McKibben bending actuator

High power-to-weight ratio soft artificial muscles are of overarching importance to enable inherently safer solutions to human-robot interactions. Traditional air driven soft McKibben artificial muscles are linear actuators. It is impossible for them to realize bending motions through a single McKibben muscle. Over two McKibben muscles should normally be used to achieve bending or rotational motions, leading to heavier and larger systems. In addition, air driven McKibben muscles are highly nonlinear in nature, making them difficult to be controlled precisely. A SMA(shape memory alloy)–fishing–line–McKibben (SFLM) bending actuator has been developed. This novel artificial actuator, made of a SMA-fishing-line muscle and a McKibben muscle, was able to produce the maximum output force of 3.0 N and the maximum bending angle (the rotation of the end face) of 61°. This may promote the application of individual McKibben muscles or SMA-fishing-line muscles alone. An output force control method for SFLM is proposed, and based on MATLAB/Simulink software the experiment platform is set up, the effectiveness of control system is verified through output force experiments. A three-fingered SFLM gripper driven by three SFLMs has been designed for a case study, which the maximum carrying capacity is 650.4 ± 0.2 g

RESEARCH TOWARDS THE DESIGN OF A NOVEL SMART FLUID DAMPER USING A MCKIBBEN ACTUATOR

Vibration reducing performance of many mechanical systems, decreasing the quality of manufactured products, producing noise, generating fatigue in mechanical components, and producing an uncomfortable environment for human bodies. Vibration control is categorized as: active, passive, or semi-active, based on the power consumption of the control system and feedback or feed forward based on whether sensing is used to control vibration. Semi-active vibration control is the most attractive method; one method of semi-active vibration control could be designed by using smart fluid. Smart fluids are able to modify their effective viscosity in response to an external stimulus such as a magnetic field. This unique characteristic can be utilised to build semi-active dampers for a wide variety of vibration control systems. Previous work has studied the application of smart fluids in semi-active dampers, where the kinetic energy of a vibrating structure can be dissipated in a controllable fashion. A McKibben actuator is a device that consists of a rubber tube surrounded by braided fibre material. It has different advantages over a piston/cylinder actuator such as: a high power to weight ratio, low weight and less cost. Recently McKibben actuator has appeared in some semi-active vibration control devise. This report investigates the possibility of designing a Magnetorheological MR damper that seeks to reduce the friction in the device by integrating it with a McKibben actuator. In this thesis the concept of both smart fluid and McKibben actuator have been reviewed in depth, and methods of modelling and previous applications of devices made using these materials are also presented. The experimental part of the research includes: designing and modelling a McKibben actuator (using water) under static loads, and validating the model experimentally. The research ends by presenting conclusions and future work

Experimental Evaluation of A Cylinder Actuator Control Using McKibben Muscle

There has been an increased interest in applying pneumatic muscle actuator (PMA) in robotic systems because of its low weight and high compliant characteristics. On the other hand, pneumatic muscle actuator (PMA) is gaining attention in robotic applications because of its low weight and high compliant characteristics. It is known that the McKibben muscle is different from the fluidic cylinder actuator in that the cylinder was unstable in its position and in its velocity in an open-loop system unlike the McKibben that is stable in its position. The modeling and control of McKibben muscle as the actuator for the cylinder are crucial because it is known to have non-linear response, hysteresis and small stroke. In this project, a single acting cylinder model which would have uncontrolled extension to push direction by compressed air, is actuated and controlled using a PMA. The system is designed with two 1.3mm-diameter McKibben muscles attached to the cylinder. Open loop control was used and the result shows that the PMA is able to control the cylinder with good performance

The design and mathematical modelling of novel extensor bending pneumatic artificial muscles (EBPAMs) for soft exoskeletons

This article presents the development of a power augmentation and rehabilitation exoskeleton based on a novel actuator. The proposed soft actuators are extensor bending pneumatic artificial muscles. This type of soft actuator is derived from extending McKibben artificial muscles by reinforcing one side to prevent extension. This research has experimentally assessed the performance of this new actuator and an output force mathematical model for it has been developed. This new mathematical model based on the geometrical parameters of the extensor bending pneumatic artificial muscle determines the output force as a function of the input pressure. This model is examined experimentally for different actuator sizes. After promising initial experimental results, further model enhancements were made to improve the model of the proposed actuator. To demonstrate the new bending actuators a power augmentation and rehabilitation soft glove has been developed. This soft hand exoskeleton is able to fit any adult hand size without the need for any mechanical system changes or calibration. EMG signals from the human hand have been monitored to prove the performance of this new design of soft exoskeleton. This power augmentation and rehabilitation wearable robot has been shown to reduce the amount of muscles effort needed to perform a number of simple grasps

High Fidelity Dynamic Modeling and Nonlinear Control of Fluidic Artificial Muscles

A fluidic artificial muscle is a type of soft actuator. Soft actuators transmit power with elastic or hyper-elastic bladders that are deformed with a pressurized fluid. In a fluidic artificial muscle a rubber tube is encompassed by a helical fiber braid with caps on both ends. One of the end caps has an orifice, allowing the control of fluid flow in and out of the device. As the actuator is pressurized, the rubber tube expands radially and is constrained by the helical fiber braid. This constraint results in a contractile motion similar to that of biological muscles. Although artificial muscles have been extensively studied, physics-based models do not exist that predict theirmotion.This dissertation presents a new comprehensive lumped-parameter dynamic model for both pneumatic and hydraulic artificial muscles. It includes a tube stiffness model derived from the theory of large deformations, thin wall pressure vessel theory, and a classical artificial muscle force model. Furthermore, it incorporates models for the kinetic friction and braid deformation. The new comprehensive dynamic model is able to accurately predict the displacement of artificial muscles as a function of pressure. On average, the model can predict the quasi-static position of the artificial muscles within 5% error and the dynamic displacement within 10% error with respect to the maximum stroke. Results show the potential utility of the model in mechanical system design and control design. Applications include wearable robots, mobile robots, and systems requiring compact, powerful actuation.The new model was used to derive sliding mode position and impedance control laws. The accuracy of the controllers ranged from ± 6 µm to ± 50 µm, with respect to a 32 mm and 24 mm stroke artificial muscles, respectively. Tracking errors were reduced by 59% or more when using the high-fidelity model sliding mode controller compared to classical methods. The newmodel redefines the state-of-the-art in controller performance for fluidic artificial muscles