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

Cooperative project by self-bending continuum arms

Designing a multi-robot system provides numerous advantages for many applications such as low cost, multi-tasking and more efficient group work. However, the rigidity of the robots used in industrial and medical applications increases the probability of injury. Therefore, lots of research is done to increase the safety factor for robot-human interaction. As a result, either separation between the human and robot is suggested, or the force shutdown to the robot system is applied. These solutions might be useful for industrial applications, but it is not for medical applications as a direct interaction between the human and the machine is required. To overcome the rigidity problem, a soft robot arm is presented in this paper. Studying the structure and performance of a contraction pneumatic muscle actuator (PMA) is illustrated, then useful strategies are used to implement a multi PMA continuum arm to increase the performance options for such types of the actuator. Moreover, twin arms are constructed to organise a collaborative project depending on the performance abilities of the proposed arms and end effectors

Design, fabrication and control of soft robots

Conventionally, engineers have employed rigid materials to fabricate precise, predictable robotic systems, which are easily modelled as rigid members connected at discrete joints. Natural systems, however, often match or exceed the performance of robotic systems with deformable bodies. Cephalopods, for example, achieve amazing feats of manipulation and locomotion without a skeleton; even vertebrates such as humans achieve dynamic gaits by storing elastic energy in their compliant bones and soft tissues. Inspired by nature, engineers have begun to explore the design and control of soft-bodied robots composed of compliant materials. This Review discusses recent developments in the emerging field of soft robotics.National Science Foundation (U.S.) (Grant IIS-1226883

Novel design and position control strategy of a soft robot arm

This article presents a novel design of a continuum arm, which has the ability to extend and bend efficiently. Numerous designs and experiments have been done to different dimensions on both types of McKibben pneumatic muscle actuators (PMA) in order to study their performances. The contraction and extension behaviour have been illustrated with single contractor actuators and single extensor actuators, respectively. The tensile force for the contractor actuator and the compressive force for the extensor PMA are thoroughly explained and compared. Furthermore, the bending behaviour has been explained for a single extensor PMA, multi extensor actuators and multi contractor actuators. A two-section continuum arm has been implemented from both types of actuators to achieve multiple operations. Then, a novel construction is proposed to achieve efficient bending behaviour of a single contraction PMA. This novel design of a bending-actuator has been used to modify the presented continuum arm. Two different position control strategies are presented, arising from the results of the modified soft robot arm experiment. A cascaded position control is applied to control the position of the end effector of the soft arm at no load by efficiently controlling the pressure of all the actuators in the continuum arm. A new algorithm is then proposed by distributing the x, y and z-axis to the actuators and applying an effective closed-loop position control to the proposed arm at different load conditions

Design, kinematics, and controlling a novel soft robot arm with parallel motion

This article presents a novel design for a double bend pneumatic muscle actuator (DB-PMA) inspired by snake lateral undulation. The presented actuator has the ability to bend in opposite directions from its two halves. This behavior results in horizontal and vertical movements of the actuator distal ends. The kinematics for the proposed actuator are illustrated and experiments conducted to validate its unique features. Furthermore, a continuum robot arm with the ability to move in parallel (horizontal displacement) is designed with a single DB-PMA and a two-finger soft gripper. The performance of the soft robot arm presented is explained, then another design of the horizontal motion continuum robot arm is proposed, using two self-bending contraction actuators (SBCA) in series to overcome the payload effects on the upper half of the soft arm

The design and mathematical model of a novel variable stiffness extensor-contractor pneumatic artificial muscle

This article presents the design of a novel Extensor-Contractor Pneumatic Artificial Muscle (ECPAM). This new actuator has numerous advantages over traditional pneumatic artificial muscles. These include the ability to both contract and extend relative to a nominal initial length, the ability to generate both contraction and extension forces and the ability to vary stiffness at any actuator length. A kinematic analysis of the ECPAM is presented in this article. A new output force mathematical model has been developed for the ECPAM based on its kinematic analysis and the theory of energy conservation. The correlation between experimental results and the new mathematical model has been investigated and show good correlation. Numerous stiffness experiments have been conducted to validate the variable stiffness ability of the actuator at a series of specific fixed lengths. This has proven that actuator stiffness can be adjusted independently of actuator length. Finally a stiffness-position controller has been developed to validate the effectiveness of the novel actuator

3D position mapping of continuum arm

Modelling a continuum arm is one of the major challenges in soft robotic researches. An accurate position model allows wider use of continuum robot arms in industrial and medical applications. Furthermore, accurate control can be achieved. This paper illustrates the 3D position of a constructed soft arm from 4 pneumatic muscle actuators (PMAs) in parallel, and models the movement of its free end in space. The performance of the contraction and extension PMAs and the behaviour of the contraction and extension arms are analysed, and a comparison between the two arms is explained. Finally, the mathematical models are presented and validated