A Novel Variable Stiffness Compound Extensor-Pneumatic Artificial Muscle (CE-PAM): Design and Mathematical Model

Pneumatic artificial muscles (PAMs) have been exploited in robots utilized in various fields, including industry and medicine, due to their numerous advantages, such as their light weight; smooth, fast responses; and ability to generate significant force when fully extended. The actuator’s stiffness is important in these applications, and extensor PAMs (EPAMs) have a lower stiffness when compared to contractor PAMs (CPAMs). Because of this, this research presents the compound extensor PAM (CE-PAM), which is a novel actuator that has higher stiffness and can alter its stiffness at a fixed length or maintain a fixed stiffness at a variable length. This makes it useful in applications such as surgery robots and wearable robots. The CE-PAM is created by inserting the CPAM into the EPAM. Then, a mathematical model is developed to calculate the output force using several mathematical equations that relate the force, actuator size, and applied pressure to each other. The force is also calculated experimentally, and when comparing the mathematical with the experimental results, the error percentage appears greater than 20%. So the mathematical model is enhanced by calculating the wasted energy consumed by the actuator before the start of the bladder’s expansion, at which the force is zero because the pressure is consumed only for bladder expansion to touch the sleeve. The effect of the bladder’s thickness is calculated to further enhance the model by calculating the volume of air entering the muscle rather than the total muscle volume. To illustrate the effect of thickness on the actuator, experiments are conducted on CPAMs made of the same bladder material but with different thicknesses. A balloon is used in the manufacture of the bladder. Because it is a lightweight, thin material with a low thickness, it requires very low pressure to expand

Design, Implementation, and Kinematics of a Twisting Robot Continuum Arm Inspired by Human Forearm Movements

In this article, a soft robot arm that has the ability to twist in two directions is designed. This continuum arm is inspired by the twisting movements of the human upper limb. In this novel continuum arm, two contractor pneumatic muscle actuators (PMA) are used in parallel, and a self-bending contraction actuator (SBCA) is laid between them to establish the twisting movement. The proposed soft robot arm has additional features, such as the ability to contract and bend in multiple directions. The kinematics for the proposed arm is presented to describe the position of the distal end centre according to the dimensions and positions of the actuators and the bending angle of the SBCA in different pressurized conditions. Then, the rotation behaviour is controlled by a high precision controller system

Novel soft bending actuator based power augmentation hand exoskeleton controlled by human intention

This article presents the development of a soft material power augmentation wearable robot using novel bending soft artificial muscles. This soft exoskeleton was developed as a human hand power augmentation system for healthy or partially hand disabled individuals. The proposed prototype serves healthy manual workers by decreasing the muscular effort needed for grasping objects. Furthermore, it is a power augmentation wearable robot for partially hand disabled or post-stroke patients, supporting and augmenting the fingers’ grasping force with minimum muscular effort in most everyday activities. This wearable robot can fit any adult hand size without the need for any mechanical system changes or calibration. Novel bending soft actuators are developed to actuate this power augmentation device. The performance of these actuators has been experimentally assessed. A geometrical kinematic analysis and mathematical output force model have been developed for the novel actuators. The performance of this mathematical model has been proven experimentally with promising results. The control system of this exoskeleton is created by hybridization between cascaded position and force closed loop intelligent controllers. The cascaded position controller is designed for the bending actuators to follow the fingers in their bending movements. The force controller is developed to control the grasping force augmentation. The operation of the control system with the exoskeleton has been experimentally validated. EMG signals were monitored during the experiments to determine that the proposed exoskeleton system decreased the muscular efforts of the wearer

Soft Actuator Based on a Novel Variable Stiffness Compound Extensor Bending-Pneumatic Artificial Muscle (CEB-PAM): Design and Mathematical Model

Soft robots have gained prominence in various fields in recent years, particularly in medical applications such as rehabilitation, due to their numerous advantages. The primary building blocks of a soft robot are often pneumatic artificial muscles (PAM). The Extensor PAM (EPAM), including Extensor Bending PAM (EB-PAM), is characterized by its low stiffness, and because stiffness is important in many robotic applications, for example, in rehabilitation, the degree of disability varies from one person to another, such as spasticity, weakness, and contracture. Therefore, it was necessary to provide an actuator with variable stiffness whose stiffness can be controlled to provide the appropriate need for each person, this study presents a new design for the EB-PAM that combines the EB-PAM and contractor PAM (CPAM), It has higher stiffness than traditional EPAM, A stiffness of over 850 N/m was achieved, whereas EB-PAM only reached a stiffness of less than 450 N/m, it is also possible to change its stiffness at a specific bending angle. It is also possible to obtain fixed stiffness at different angles.  A mathematical model was developed to calculate the output force of the new muscle by calculating its size and the pressure applied to it and comparing the model with experimental results. The mathematical model was enhanced by calculating the wasted energy consumed by the actuator before the bladder begins to expand, and also by calculating the thickness of the bladder and the sleeve. To make the muscle lighter, cheaper, and work under low pressures, balloons were used in manufacturing, offering practical advantages for soft robotic applications