Pneumatic Artificial Muscles (PAMs) Identification for Actuating a Wrist-Joint Rehabilitation Robot

Pneumatic Artificial Muscles (PAMs) are the most promising type of pneumatic-based actuators. Recently, they have been widely used in medical and rehabilitation robotic systems due to their flexibility, reliability, and high load-to-weight ratio. The aim of this work is to introduce an accurate mathematical model for describing the performance of the pneumatic artificial muscles under different applied pressures and loads by examining different previously proposed models. Being motivated by the muscles’ usage in a wearable robotic device for wrist rehabilitation where the required muscle force is not so large, it is interesting to consider the model that best expresses the muscle behavior over a lower range of the muscle force. An experimental system for measuring the muscle contraction at different applied pressures and loads is set up. Then, an algorithm for the parameters identification of the examined models based on the least squared error approach is developed using MATLAB Software

A Multistate Friction Model for the Compensation of the Asymmetric Hysteresis in the Mechanical Response of Pneumatic Artificial Muscles

These days, biomimetic and compliant actuators have been made available to the main applications of rehabilitation and assistive robotics. In this context, the interaction control of soft robots, mechatronic surgical instruments and robotic prostheses can be improved through the adoption of pneumatic artificial muscles (PAMs), a class of compliant actuators that exhibit some similarities with the structure and function of biological muscles. Together with the advantage of implementing adaptive compliance control laws, the nonlinear and hysteretic force/length characteristics of PAMs pose some challenges in the design and implementation of tracking control strategies. This paper presents a parsimonious and accurate model of the asymmetric hysteresis observed in the force response of PAMs. The model has been validated through the experimental identification of the mechanical response of a small-sized PAM where the asymmetric effects of hysteresis are more evident. Both the experimental results and a comparison with other dynamic friction models show that the proposed model could be useful to implement efficient compensation strategies for the tracking control of soft robots

Analysis of Nonlinear Behavior in Novel Pneumatic Artificial Muscles

Motivated by the excellent actuator characteristics of pneumatic artificial muscles (PAMs), two novel actuators based on this technology were developed for applications where traditional PAMs are not suitable. The first of these actuators is a miniature PAM that possesses the same operating principle as a full-scale contractile PAM, but with a diameter an order of magnitude smaller. The second actuator, a push-PAM, harnesses the operational characteristics of a contractile PAM, but changes the direction of motion and force with a simple conversion package. Testing on these actuators revealed each PAM's evolution of force with displacement for a range of operating pressures. To address the analysis of the nonlinear response of these PAMs, a nonlinear stress vs. strain model, a hysteresis model, and a pressure deadband were introduced into a previously developed force balance analysis. The refined nonlinear model was shown to reconstruct PAM response with higher accuracy than previously possible

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 and Testing of a Biomimetic Pneumatic Actuated Seahorse Tail Inspired Robot

The purpose of this study is to build and test a pneumatically actuated robot based on the biomimetic design of a seahorse tail. McKibben muscles, a form of pneumatic actuator, have been previously used to create highly flexible robots. It has also been discovered that the seahorse tail serves as a highly flexible and prehensile, yet armored appendage. Combining these topics, this research aims to create a robot with the mechanical flexibility of a pneumatic actuator and the protection of a seahorse tail. First, the performance of a miniature McKibben muscle design is examined. Then, the artificial muscles are implemented into a 3D-printed seahorse tail-inspired skeleton. The robot\u27s actuation was observed to determine its maximum bending capacities. The results of the experiments revealed that the miniature McKibben muscles performed comparably to larger sized McKibben muscles previously reported in literature. The pneumatically actuated robot achieved a maximum bend angle of ~22°. Further research is recommended to determine the behaviors of similar robots with additional plates or McKibben muscles spanning shorter plate sequences

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

Soft Actuators and Robotic Devices for Rehabilitation and Assistance

Soft actuators and robotic devices have been increasingly applied to the field of rehabilitation and assistance, where safe human and machine interaction is of particular importance. Compared with their widely used rigid counterparts, soft actuators and robotic devices can provide a range of significant advantages; these include safe interaction, a range of complex motions, ease of fabrication and resilience to a variety of environments. In recent decades, significant effort has been invested in the development of soft rehabilitation and assistive devices for improving a range of medical treatments and quality of life. This review provides an overview of the current state-of-the-art in soft actuators and robotic devices for rehabilitation and assistance, in particular systems that achieve actuation by pneumatic and hydraulic fluid-power, electrical motors, chemical reactions and soft active materials such as dielectric elastomers, shape memory alloys, magnetoactive elastomers, liquid crystal elastomers and piezoelectric materials. Current research on soft rehabilitation and assistive devices is in its infancy, and new device designs and control strategies for improved performance and safe human-machine interaction are identified as particularly untapped areas of research. Finally, insights into future research directions are outlined

An integrated intelligent nonlinear control method for a pneumatic artificial muscle

This paper proposes an advanced position-tracking control approach, referred to as an integrated intelligent nonlinear controller, for a pneumatic artificial muscle (PAM) system. Due to the existence of uncertain, unknown, and nonlinear terms in the system dynamics, it is difficult to derive an exact mathematical model with robust control performance. To overcome this problem, the main contributions of this paper are as follows. To actively represent the behavior of the PAM system using a grey-box model, neural networks are employed as equivalent internal dynamics of the system model and optimized online by a Lyapunov-based method. To realize the control objective by effectively compensating for the estimation error, an advanced robust controller is developed from the integration of the designed networks, and improvement of the sliding mode and backstepping techniques. The convergences of both the developed model and the closed-loop control system are guaranteed by Lyapunov functions. As a result, the overall control approach is capable of ensuring the system's performance with fast response, high accuracy, and robustness. Real-time experiments are carried out in a PAM system under different conditions to validate the effectiveness of the proposed method