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The purpose of this paper is to describe a mechanical equilibrium model of a one‐end‐fixed type rubberless artificial muscle and the feasibility of this model for control of the rubberless artificial muscle. This mechanical equilibrium model expresses the relation between inner pressure, contraction force, and contraction displacement. The model validity and usability were confirmed experimentally.

Position control of a one‐end‐fixed type rubberless artificial muscle antagonistic drive system was conducted using this mechanical equilibrium model. This model contributes to adjustment of the antagonistic force.

The derived mechanical equilibrium model shows static characteristics of the rubberless artificial muscle well. Furthermore, it experimentally confirmed the possibility of realizing position control with force adjustment of the rubberless artificial muscle antagonistic derive system. The mechanical equilibrium model is useful to control the rubberless artificial muscle.

This paper reports the realization of advanced control of the rubberless artificial muscle using the derived mechanical equilibrium model.

This study aims to propose a novel lightweight tendon-driven musculoskeletal arm (LTDM-arm) robot with a flexible series–parallel mixed skeletal joint structure and modularized artificial muscle system (MAMS). The proposed LTDM-arm exhibits human-like flexibility, safety and operational accuracy. In addition, to improve the safety and stability of the LTDM-arm, a control method is proposed to solve local artificial muscle overload accidents.

The proposed LTDM-arm comprises seven degrees of freedom skeletons, 15 MAMSs and various sensor systems (joint sensing, muscle tension sensing, visual sensing, etc.). It retains the morphology of a human skeleton (humerus, ulna and radius) and a simplified muscle configuration. This study proposes an input saturation control with full-state constraints to reduce local artificial muscle overload accidents caused by redundant muscle tension calculations.

3D circular trajectory experiments were conducted to verify the stability of the control method and the flexibility of the LTDM-arm. The results showed that the average error of the muscle length was approximately 0.35 mm (0.38%), which indicates that the proposed control scheme can make the output follow the target trajectory while ensuring constraint satisfaction.

The human arm is capable of performing compliant operations rapidly, flexibly and robustly in unstructured environments. Existing musculoskeletal arm robots lack simulations of the full morphology of the human arm and are insufficient in dexterity. However, the flexibility and safety features of the proposed LTDM-arm were consistent with that of the human arm. Therefore, this study offers a new approach for investigating the advantages of the musculoskeletal system and the concepts of muscle control.

Humans throughout history have always sought to mimic the appearance, mobility, functionality, intelligent operation, and thinking processes of biological creatures. Advancements in artificial muscles, artificial intelligence, artificial vision and many other biomimetic related fields are leading to many benefits for humankind. One of the newest among these fields is the artificial muscle, which is the moniker for electroactive polymers. The potential of these materials is enormous and, as challenges are addressed and new effective materials are introduced, capabilities that were considered as science fiction are becoming engineering reality. This paper covers the current state‐of‐the‐art and challenges to make biomimetic robots use artificial muscles.

This paper aims to optimize the stiffness coefficient of the elastic element for a passive waist assistive exoskeleton (WAE). There is a tradeoff between stiffness coefficient of elastic element of the exoskeleton and work efficiency of the wearer, because elastic element affects original bending motion of the wearer and the force requirement of erector spinae is compensated by the other muscles. However, there is no accepted conclusion on how to determine the proper stiffness coefficient, especially with respected to the effort of groups of muscles, not only erector spinae.

In this study, a consumption indicator based on muscle fatigue of seven muscles is proposed and a Bayesian-based human-in-the-loop optimization approach is adopted to optimize the stiffness coefficient. Pneumatic artificial muscles are used to replace the mechanical elastic part to adjust the assistive force automatically. The proposed optimization method is verified by the way of load-lifting experiments with three different conditions: without exoskeleton, with fixed air pressure and with optimized air pressure. Six subjects participated in the experiment and each experiment is performed in different day.

Compared with No-Exo condition and static assistance condition, the parameter-optimized waist exoskeleton averagely reduces muscle fatigue of the six subjects by 45.30 ± 29.14% and 30.94 ± 30.29%, respectively. The experimental results indicate that the proposed method is effective to reduce muscle fatigue during stoop lifting task.

This paper provides a novel cost function construction method based on muscle fatigue and muscle synergy for passive WAE stiffness optimization.

Describes the McKibben muscle and its major properties. Outlines the analogy between this artificial muscle and the skeletal muscle. Describes the actuator composed of two McKibben muscles set into antagonism based on the model of the biceps‐triceps system, and explains its natural compliance in analogy with our joint litheness. Reports some control experiments developed on a two d.o.f. robot actuated by McKibben muscles which emphasize the ability of these robot‐arms to move in contact with their environment as well as moving loads of high ratio to the robot’s own weight. Also outlines control difficulties and accuracy limitations and discusses applications.

The purpose of this paper is to apply virtual agonist–antagonist mechanisms (VAAMs) to robot joint control allowing for muscle-like functions and variably compliant joint motions. Biological muscles of animals have a surprising variety of functions, i.e. struts, springs and brakes.

Each joint is driven by a pair of VAAMs (i.e. passive components). The muscle-like functions as well as the variable joint compliance are simply achieved by tuning the damping coefficient of the VAAM.

With the VAAM, variably compliant joint motions can be produced without mechanically bulky and complex mechanisms or complex force/toque sensing at each joint. Moreover, through tuning the damping coefficient of the VAAM, the functions of the VAAM are comparable to biological muscles.

The model (i.e. VAAM) provides a way forward to emulate muscle-like functions that are comparable to those found in physiological experiments of biological muscles. Based on these muscle-like functions, the robotic joints can easily achieve variable compliance that does not require complex physical components or torque sensing systems, thereby capable of implementing the model on small-legged robots driven by, for example, standard servo motors. Thus, the VAAM minimizes hardware and reduces system complexity. From this point of view, the model opens up another way of simulating muscle behaviors on artificial machines.

The VAAM can be applied to produce variable compliant motions of a high degree-of-freedom robot. Only relying on force sensing at the end effector, this application is easily achieved by changing coefficients of the VAAM. Therefore, the VAAM can reduce economic cost on mechanical and sensing components of the robot, compared to traditional methods (e.g. artificial muscles).

The purpose of this study is to confirm that the body weight load reduction system which is developed by us is effective to reduce the knee joint force of the walking user. This system is driven by pneumatic artificial muscle, functions as a mobile walking assist system.

The developed body weight load reduction system driven by rubber-less artificial muscle (RLAM) was tested experimentally. Simple force feedback control is applied to the RLAM. The system moves as synchronized with vertical movement of the walking user. The knee joint force during walking experiments conducted using this system is estimated by measurement of floor reaction force and position data of lower limb joints.

The knee joint force during walking is reduced when using this system. This system contributes to smooth change of knee joint force when the lower limb contacts the floor.

This lightweight body weight load reduction system is particularly effective for realizing easy-to-use mobile walking assist system.

A lightweight body weight load reduction system using pneumatic artificial muscle is a novel proposal. Additionally, these new evaluation results demonstrate its effectiveness for reducing knee joint force during walking.

The purpose of this paper is to inform the readers of the design process and practical implications of a new gripping device created by the authors.

We have developed a novel gripping device based on the biomechanics of the feeding apparatus of the marine mollusk, Aplysia californica. The gripping device uses modified McKibben artificial muscles arranged in rings and placed in parallel. The rings contract sequentially to produce peristalsis, which moves a grasping mechanism back and forth through the rings.

The central grasper is capable of conforming to soft and irregular material.

This device could have novel applications both for removal of tissue in medical applications and for removing material from clogged plumbing lines.

This paper demonstrates the utility of using biological inspiration for developing novel robotic devices and suggests new ways of handling slippery, irregular, and fragile material.

The purpose of this paper is to describe a range of artificial muscle and soft gripping technologies for robotic applications.

Following a short introduction, this paper first discusses the role of air muscles and other pneumatic actuation technologies. It then considers electroactive polymer and shape‐memory alloys and finally discusses the prospects for various classes of electrohydrodynamic fluids.

This paper shows that a technologically diverse range of novel actuation techniques exist, or are under development, which can act as artificial muscles and soft grippers. They are based on pneumatics, shape changing materials and electrohydrodynamic fluids and have prospects to impart robots with improved or unique capabilities.

The paper provides an insight into developments in artificial muscle and soft gripping technologies. These are expected to play a vital role in future robot generations.