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

Editorial : pneumatic actuators

Special issue journal editorial

Footwear matters: influence of footwear and foot strike on load rates during running

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.This is a non-final version of an article published in final form in Medicine and Science in Sports 22 and Exercise, 2016 Jul 6.INTRODUCTION: Running with a forefoot strike (FFS) pattern has been suggested to reduce the risk of overuse running injuries, due to a reduced vertical loadrate compared with rearfoot strike (RFS) running. However, resultant loadrate has been reported to be similar between foot strikes when running in traditional shoes, leading to questions regarding the value of running with a FFS. The influence of minimal footwear on the resultant loadrate has not been considered. This study aimed to compare component and resultant instantaneous loadrate (ILR) between runners with different foot strike patterns in their habitual footwear conditions. METHODS: 29 injury-free participants (22 males, 7 females) ran at 3.13m.s along a 30m runway, with their habitual foot strike and footwear condition. Ground reaction force data were collected. Peak ILR values were compared between three conditions; those who habitually run with a RFS in standard shoes, with a FFS in standard shoes, and with a FFS in minimal shoes. RESULTS: Peak resultant, vertical, lateral and medial ILR were lower (P < 0.001) when running in minimal shoes with a FFS than in standard shoes with either foot strike. When running with a FFS, peak posterior ILR were lower (P < 0.001) in minimal than standard shoes. CONCLUSIONS: When running in a standard shoe, peak resultant and component instantaneous loadrates were similar between footstrike patterns. However, loadrates were lower when running in minimal shoes with a FFS, compared with running in standard shoes with either foot strike. Therefore, it appears that footwear alters the loadrates during running, even with similar foot strike patterns

Footwear matters: influence of footwear and foot strike on load rates during running

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.This is a non-final version of an article published in final form in Medicine and Science in Sports 22 and Exercise, 2016 Jul 6.INTRODUCTION: Running with a forefoot strike (FFS) pattern has been suggested to reduce the risk of overuse running injuries, due to a reduced vertical loadrate compared with rearfoot strike (RFS) running. However, resultant loadrate has been reported to be similar between foot strikes when running in traditional shoes, leading to questions regarding the value of running with a FFS. The influence of minimal footwear on the resultant loadrate has not been considered. This study aimed to compare component and resultant instantaneous loadrate (ILR) between runners with different foot strike patterns in their habitual footwear conditions. METHODS: 29 injury-free participants (22 males, 7 females) ran at 3.13m.s along a 30m runway, with their habitual foot strike and footwear condition. Ground reaction force data were collected. Peak ILR values were compared between three conditions; those who habitually run with a RFS in standard shoes, with a FFS in standard shoes, and with a FFS in minimal shoes. RESULTS: Peak resultant, vertical, lateral and medial ILR were lower (P < 0.001) when running in minimal shoes with a FFS than in standard shoes with either foot strike. When running with a FFS, peak posterior ILR were lower (P < 0.001) in minimal than standard shoes. CONCLUSIONS: When running in a standard shoe, peak resultant and component instantaneous loadrates were similar between footstrike patterns. However, loadrates were lower when running in minimal shoes with a FFS, compared with running in standard shoes with either foot strike. Therefore, it appears that footwear alters the loadrates during running, even with similar foot strike patterns

Practical Sparse Matrices in C++ with Hybrid Storage and Template-Based Expression Optimisation

Despite the importance of sparse matrices in numerous fields of science, software implementations remain difficult to use for non-expert users, generally requiring the understanding of underlying details of the chosen sparse matrix storage format. In addition, to achieve good performance, several formats may need to be used in one program, requiring explicit selection and conversion between the formats. This can be both tedious and error-prone, especially for non-expert users. Motivated by these issues, we present a user-friendly and open-source sparse matrix class for the C++ language, with a high-level application programming interface deliberately similar to the widely used MATLAB language. This facilitates prototyping directly in C++ and aids the conversion of research code into production environments. The class internally uses two main approaches to achieve efficient execution: (i) a hybrid storage framework, which automatically and seamlessly switches between three underlying storage formats (compressed sparse column, Red-Black tree, coordinate list) depending on which format is best suited and/or available for specific operations, and (ii) a template-based meta-programming framework to automatically detect and optimise execution of common expression patterns. Empirical evaluations on large sparse matrices with various densities of non-zero elements demonstrate the advantages of the hybrid storage framework and the expression optimisation mechanism.Comment: extended and revised version of an earlier conference paper arXiv:1805.0338

Variable stiffness robotic hand for stable grasp and flexible handling

Robotic grasping is a challenging area in the field of robotics. When interacting with an object, the dynamic properties of the object will play an important role where a gripper (as a system), which has been shown to be stable as per appropriate stability criteria, can become unstable when coupled to an object. However, including a sufficiently compliant element within the actuation system of the robotic hand can increase the stability of the grasp in the presence of uncertainties. This paper deals with an innovative robotic variable stiffness hand design, VSH1, for industrial applications. The main objective of this work is to realise an affordable, as well as durable, adaptable, and compliant gripper for industrial environments with a larger interval of stiffness variability than similar existing systems. The driving system for the proposed hand consists of two servo motors and one linear spring arranged in a relatively simple fashion. Having just a single spring in the actuation system helps us to achieve a very small hysteresis band and represents a means by which to rapidly control the stiffness. We prove, both mathematically and experimentally, that the proposed model is characterised by a broad range of stiffness. To control the grasp, a first-order sliding mode controller (SMC) is designed and presented. The experimental results provided will show how, despite the relatively simple implementation of our first prototype, the hand performs extremely well in terms of both stiffness variability and force controllability

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

A circular pneumatic muscle actuator (CPMA) inspired by human skeletal muscles

This paper illustrates the design, implementation and kinematics of a novel circular pneumatic muscle actuator (CPMA), inspired by the skeletal muscles of a human. The variation of the inner diameter of this actuator is a unique feature. Furthermore, CPMA produces a radial force towards its centre by increasing the diameter of the actuator itself in addition to the reduction in the inner diameter. These performances make the presented actuator suitable to use in numerous applications. The grasping by a soft gripper is chosen as an application to design an efficient soft gripper by using single and multiple CPMAs

Novel models for the extension pneumatic muscle actuator performances

This paper illustrates the design, implementation and modelling of the extensor pneumatic muscle actuator (PMA). The extensor soft actuator has a vital feature of ability to bend and extend, and that give it the flexibility to use in numerous applications. The extended behaviour of this actuator is modelled mathematically to be used to predict the length of a wide range of actuators at different air pressure amounts and make the position control of such type of actuator easier and precise. Moreover, the contraction force formula is modified to describe the pushing force for the extensor actuator. The bending behaviour of single muscle is explained and a 4-PMA continuum arm has been constructed to study its performance and model the bending angle