Georgios Andrikopoulos

A Survey on applications of Pneumatic Artificial Muscles

The aim of this article is to present a survey on applications of Pneumatic Artificial Muscles (PAMs). PAMs are highly non-linear pneumatic actuators where their elongation is proportional to the interval pressure. During the last decade, there has been a significant increase in the industrial and scientific utilization of PAMs due to their advantages such as high strength and small weight, while various types of PAMs with different technical characteristics have been appeared in the relative scientific literature. This article will summarize the key enabling applications in PAMs that are focusing in the following areas: a) Biorobotic, b) Medical, c) Industrial, and d) Aerospace applications.

Pseudoexfoliation syndrome and cardiovascular diseases

Pseudoexfoliation (PEX) syndrome is a well-recognized late-onset disease caused by a generalized fibrillopathy. It is linked to a broad spectrum of ocular complications including glaucoma and perioperative problems during cataract surgery. Apart from the long-known intraocular manifestations, PEX deposits have been found in a variety of extraocular locations and they appear to represent a systemic process associated with increased cardiovascular and cerebrovascular morbidity. However, as published results are inconsistent, the clinical significance of the extraocular PEX deposits remains controversial. Identification of PEX deposits in the heart and the vessel wall, epidemiologic studies, as well as, similarities in pathogenetic mechanisms have led to the hypothesis of a possible relation between fibrillar material and cardiovascular disease. Recent studies suggest that PEX syndrome is frequently linked to impaired heart and blood vessels function. Systemic and ocular blood flow changes, altered parasympathetic vascular control and baroreflex sensitivity, increased vascular resistance and decreased blood flow velocity, arterial endothelial dysfunction, high levels of plasma homocysteine and arterial hypertension have all been demonstrated in PEX subjects. Common features in the pathogenesis of both atherosclerosis and PEX, like oxidative stress and inflammation and a possible higher frequency of abdominal aorta aneurysm in PEX patients, could imply that these grey-white deposits and cardiovascular disorders are related or reflect different manifestations of the same process.

An experimental study on thermodynamic properties of Pneumatic Artificial Muscles

In the past fifty years, several attempts have been made to model the characteristics of Pneumatic Artificial Muscles (PAMs). PAM models based on their geometrical properties are the most commonly found ones in the scientific literature. In the process of deriving those models a lot of assumptions and simplifications are made due to the fact that PAM is a highly non-linear form of actuation. The purpose of this study is to propose additional considerations for future model improvements that will augment the overall model accuracy, and will best describe the relationship between force, displacement and non-linear thermal properties of PAM actuators through extensive observation and analysis of its thermodynamic characteristics during long-run operation experiments. In this article multiple experimental results will be presented that prove the relation between the thermodynamic properties of the PAMs, especially in iterative operations, and the accuracy on the muscles force-prolongation relationship.

A switched system modeling approach for a Pneumatic Muscle Actuator

The aim of this article is to present a switched system approach for the dynamic modeling of Pneumatic Muscle Actuators (PMAs). PMAs are highly non-linear pneumatic actuators where their elongation is proportional to the interval pressure. During the last two decades, various modeling approaches have been presented that describe the behavior of PMAs. While most mathematical models are characterized by simplicity and accuracy in describing the attributes of PMAs, they are limited to static performance analysis. Static models are proven to be insufficient for real time control applications, thus creating the need for the development of dynamic PMA models. A collection of experimental and simulation results are being presented that prove the efficiency of the proposed approach.

Novel Considerations on Static Force Modeling of Pneumatic Muscle Actuators

In this paper, a modified static force modeling approach, which is based on fundamental pneumatic muscle actuator (PMA) modeling techniques, is proposed. In addition, the thermal expansion effect is considered as the main cause of the gradual shift in the PMAs force-displacement relationship and the geometric properties, which are being affected by the thermal build-up occurring during the PMAs continuous operation, are incorporated into the static force models. The effects of thermal expansion are documented via experimental studies, and the acquired force-displacement data are utilized for the validation of the proposed modeling method in PMAs of different nominal dimensions and at different test pressures. Finally, an additional evaluation is performed via the comparison of accuracy between the proposed model and the existing geometric static modeling approaches.

On the design, modeling and control of a novel compact aerial manipulator

The aim of this article is to present a novel four-degree-of-freedom aerial manipulator allowing a multirotor Unmanned Aerial Vehicle (UAV) to physically interact with the environment. The proposed design, named CARMA (Compact AeRial MAnipulator), is characterized by low disturbances on the UAV flight dynamics, extended workspace (with regard to its retracted configuration) and fast dynamics (compared to the UAV dynamics). The dynamic model is formulated and a control structure consisting of an inverse kinematics algorithm and independent joint position controllers is presented. Furthermore, the design specifications of the prototype are analyzed in detail, while experimental evaluations are conducted for the extraction of the manipulators workspace and the evaluation of systems tracking capabilities over pick-and-place trajectories. Finally, it is shown that the selected joint position sensors, combined with the derived inverse dynamic algorithm allow to determine the wrenches exerted at the base, due to swift motions of the arm.

Motion control of a novel robotic wrist exoskeleton via pneumatic muscle actuators

In this article, the motion control problem of a robotic EXOskeletal WRIST (EXOWRIST) prototype is considered. This novel robotic appliances motion is achieved via pneumatic muscle actuators, a pneumatic form of actuation possessing crucial attributes for the development of an exoskeleton that is safe, reliable, portable and low-cost. The EXOWRISTs properties are presented in detail and compared to the recent wrist exoskeleton technology, while its two degrees-of-freedom movement capabilities (extension-flexion, ulnar-radial deviation) are experimentally evaluated on a healthy human volunteer via an advanced nonlinear PID-based control algorithm.

Non-linear control of Pneumatic Artificial Muscles

In this article, a non-linear PID structure is being synthesized, providing ameliorated compensation of the Pneumatic Artificial Muscles (PAM) non-linear hysteretic phenomena and advanced robustness. Experimental studies are being utilized to prove the overall efficiency of the non-linear control scheme regarding: a) set-point tracking performance for the position control of a single PAM and torsion angle control of an antagonistic PAM setup, as well as b) disturbance rejection in both single and antagonistic control scenarios.

Design, modelling and control of a Single Rotor UAV

In this article, a novel Vertical Take-Off and Landing (VTOL) Single Rotor Unmanned Aerial Vehicle (SR-UAV) will be presented. The SRUAVs design properties will be analysed in detail, with respect to technical novelties outlining the merits of such a conceptual approach. The systems model will be mathematically formulated, while a cascaded P-PI and PID-based control structure will be utilized in extensive simulation trials for the preliminary evaluation of the SR-UAVs attitude and translational performance.

Towards the development of a novel upper-body pneumatic humanoid: Design and implementation

In this article, the conceptual design of a 14 Degree-of-Freedom (DoF) upper-body pneumatic humanoid is presented. The movement capabilities of this novel robotic setup are achieved via Pneumatic Artificial Muscles (PAMs), a form of actuation possessing crucial attributes for the development of biologically-inspired robots. To evaluate the feasibility of the humanoids design properties, a 5-DoF robotic arm is developed and experimentally tested, while being studied from the scope of implementing a robotic structure capable of producing smooth and human-like motion responses, while maintaining the inherent compliance provided by the PAM technology.