Continuum robots are inspired by biological trunks, snakes and tentacles. Unlike conventional robot manipulators, there are no rigid structures or joints. Advantageous is the ease of miniaturization combined with high dexterity, since limiting components such as bearings or gears can be omitted. Most currently used actuation elements in continuum robots require a large drive unit with electric motors or similar mechanisms. Contrarily, shape memory alloys (SMAs) can be integrated into the actual robot. The actuation is realized by applying current to the wires, which eliminates the need of an additional outside drive unit. In the presented study, SMA actuator wires are used in variously scaled continuum robots. Diameters vary from 1 to 60 mm and the lengths of the SMA driven tentacles range from 75 to 220 mm. The SMAs are arranged on an annulus in a defined distance to the neutral fiber, whereby the used cores vary from superelastic NiTi rods to complex structures and also function as restoring unit. After outlining the theoretical basics for the design of an SMA actuated continuum robot, the design process is demonstrated exemplarily using a guidewire for cardiac catheterizations. Results regarding dynamics and bending angle are shown for the presented guidewire.

A compliant hinge is proposed to replace conventional revolute joints for a shape memory alloy actuated arm-like mechanism. The arm-like mechanism is designed to replicate the articulation of the elbow joint, linking the humerus and radius, while being able to lift a dead load using a shape memory alloy wire as the biceps muscle. A parametric analysis on hinge geometry and Young’s modulus is performed to determine if a feasible geometric and material solution exists based on the application requirements. The results indicate optimum solutions are logarithmically correlated between modulus of elasticity and width-to-thickness ratio. Overlaying the results of the parametric study onto an Ashby chart indicates that large hinge widths are necessary. These results indicate more complex geometries are needed for arm-like manipulator applications.

Spiral Torsion Springs (STS) are generally manufactured employing medium/high-carbon steel alloys shaped as thin rods with rectangular cross section. Meanwhile, plastic materials (e.g. ABS or PLA), currently used in freeform manufacturing processes, may not be suited for several applications, owing to the low material yield strength and the rather poor fatigue life. Despite the above-mentioned limitations, the main advantages of a 3D printing process, as compared to more traditional manufacturing techniques, are the design flexibility and the possibility to directly integrate elastic components within a joint mechanism produced as a single (monolithic) part. In particular, provided that the external forces acting on the spring coils are maintained within a certain threshold and that the spring geometry is suitably optimized, a reliable 3D-printed STS alternative to traditional steel springs is actually feasible. Given these premises, the main purpose of the present paper is to propose a model-based optimization algorithm that allows to optimally size STS for user-specified torque-deflection characteristics. Optimal STS geometries are then realized in ABS via Fused Deposition Manufacturing, and subsequently tested with a purposely-designed experimental set-up. Furthermore, the behavior of each STS sample (in terms of stiffness and equivalent Von Mises stress) is evaluated by means of non-linear finite elements analysis, in order to check the correspondence with the expected behavior. Finally, numerical and experimental results are provided, which demonstrate the prediction capabilities of the proposed modeling/optimization techniques, and confirm that well-behaved STS can be conceived and produced. Envisaged applications concern the development of smart structures for robot design, such as multi-articulated compliant robotic chains that can be used as low-cost manipulators (i.e. arm) or as mini-manipulators (i.e. fingers). The proposed approach effectively simplifies the production and the assembly of the mechanism, also allowing for an easier integration of embedded sensory-actuation systems.

Deformation behavior of a capsule-type micro actuator using palladium as a hydrogen storage alloy was investigated. The capsule-type micro actuator using hydrogen storage alloys (HSA-CMA) drives by the volume change of the hydrogen storage alloy induced by the absorption and discharge of hydrogen gas. It was developed as a compact, lightweight and energy-saving actuator mounted on the super multi-link manipulator to capture space debris. In the present work, a palladium foil was used as the hydrogen storage alloy. It was confirmed that the actuator of 10 mm in diameter fabricated with palladium has deformed by the introduction and evacuation of hydrogen gas. The height change and deformation rate have increased with the cycle between hydrogen introduction and evacuation.

Shape memory alloys (SMA) when subjected to deformation at low temperature can recover their original shape by heating above a temperature called Austenite transformation temperature. This original shape is sustained till the material is deformed again by an applied stress. This property makes the SMA a unique actuator, which doesn’t require any other components. Also, the material’s resistance changes with deformation. Thus the change in resistance can be used to sense the deformation, which eliminates the requirements of additional sensors. This can make the system more compact and reduce the cost. In our study, a binary Nickel-Titanium alloy is used as a rotary actuator. The actuation is controlled by adjusting the temperature through controlled joule heating by varying the electric current. The manipulator used in this research is a single degree-of-freedom, bias type actuator. SMA actuation in this system is under a varying stress, thereby creating a complex thermo-mechanical condition which affects the transformation temperatures, significantly. Also, the resistance change during heating and cooling paths exhibit hysteresis behavior. This paper investigates the use of artificial neural network (ANN) in establishing relationship between resistance and angular position of the manipulator. To model the hysteresis behavior of the SMA, in addition to resistance of the SMA, other electric properties like voltage etc are given as input to the ANN. The obtained ANN model is able to determine the angular position of the rotary manipulator with good accuracy.

In recent years many investigations have been performed on design and fabrication of micro mechanical manipulators. One of the practical usages of this manipulator is endoscopy. In an endoscopy system, a small manipulator with high maneuverability and flexibility is required to support the probe’s movement into a colon easier than classic manipulators. In this paper a basic flexible module is presented for use in such an application. The structure of presented module is simple and includes a compressive spring which could be bent to the sides. This tends to more simplicity in addition to proper flexibility. Connecting three wires of shape memory alloy (SMA) uniformly distributed in circumference of spring with an angle of 120 degrees, it is possible to provide an almost large displacement and orientation change between the end planes of module. By using three wires and stimulating them individually or together, different rotation regimes are provided. The flexible module deformation is modeled in this paper thoroughly. Deflection and orientation of spring as the basic structure of the module is studied under the loads. Also, Brinson model is used for modeling the shape memory alloy wire. Afterward, the spring model is coupled with SMA model to describe the dynamic behavior of module under a defined activation. The simulation is implemented in MATLAB-Simulink Though the developed simulation platform, the trajectory of module may be extracted and used for developing a modular manipulator. An experimental setup is prepared to verify the simulation results. Through the simulations, module performance in addition to proper geometrical parameters for the considered application is calculated through the simulations. It is shown that a proper relation between geometrical parameters of spring (like outer diameter, spring wire diameter and number of coils) in combination with a suitable SMA wire in diameter, affect the maximum deformation of SMA-actuated module.

Capsule-type micro actuator driven by the volume change of hydrogen storage alloys (HSA-CMA) was proposed to be applied as an actuator mounted on the joints of the super multilink manipulator to capture space debris. This actuator consists of a hollow sphere frame made of aluminum, a membrane of hydrogen storage alloys and a valve, and is compact and lightweight. The aim of this study was to evaluate the availability of HSA-CMA. Finite element analyses were performed to investigate the actuator displacement and the generating force as the static performance, and the obtained static performances were compared with that of other smart actuators. The analysis on the actuator displacement led to the design map of HSA-CMA. The comparison result suggests that HSA-CMA has the actuator displacement and the generating force as well or better than other smart actuators and that it is suitable for use in space.

Pneumatic artificial muscles (PAMs), or McKibben actuators, have received considerable attention for robotic manipulators and in aerospace applications due to their similarity to natural muscles. Like natural muscles, PAMs are a purely contractile actuator, so that, in order to produce bidirectional or rotational motion, they must be arranged in an agonist/antagonist pair, which inherently limits the deflection of the system due to the high parasitic stiffness of the antagonistic PAM. This study presents two methods for increasing the performance of an antagonistic PAM system by decreasing the passive parasitic moment, rather than increasing the active moment. The first involves selection of the kinematic mechanism geometry, and the second involves the introduction of bias into the system, both in terms of PAM contraction, and passive (antagonistic) PAM pressure. It was found with the proper selection of design parameters, including mechanism geometry, PAM geometry, and bias conditions, that an ideal actuator configuration can be found that maximizes deflection for a given arbitrary loading. When comparing a baseline design to an improved design for a simplified case, a nearly 50% increase in maximum deflection was predicted simply by optimizing mechanism geometry and bias contraction.

Pneumatic artificial muscles (PAMs) are lightweight, flexible actuators capable of higher specific work than comparably-sized hydraulic actuators at the same pressure and electric motors. PAMs are composed of an elastomeric bladder surrounded by a helically braided sleeve. Lightweight, compliant actuators are particularly desirable in portable, heavy-lift robotic systems intended for interaction with humans, such as those envisioned for patient assistance in hospitals and battlefield casualty extraction. However, smooth and precise control remains difficult because of nonlinearities in the dynamic response. The objective of this paper is to develop a control algorithm that satisfies accuracy and smooth motion requirements for a two degree-of-freedom manipulator actuated by pneumatic artificial muscles and intended for interaction with humans, such as lifting a human. This control strategy must be capable of responding to large, abrupt variations in payload weight over a high range of motion. In previous work, the authors detailed the design and construction of a proof-of-concept PAM-based manipulator. The present work investigates the feasibility of combining output feedback using proportional-integral-derivative control or fuzzy logic control with model-based feedforward compensation to achieve improved closed-loop performance. The model upon which the controller is based incorporates the internal airflow dynamics, the geometric parameters of the pneumatic actuators, and the arm dynamics. Simulations were performed in order to validate the control algorithm, guide controller design, and predict optimal gains. Using real-time interface software and hardware, the controller was implemented and experimentally tested on the manipulator. Performance was evaluated for several trajectories, and different payload weights. The effect of varying the feedforward gain was also analyzed. Model refinement further improved performance.

Recent advances in actuator technology suggest that the implementation of reliable, high power-to-weight ratio pneumatic actuation systems is now possible for robotic platforms. Current robotic manipulator arms for casualty extraction and patient placement use hydraulic actuation, whereas related robotic prosthetic devices use large, heavy actuator motors. We have developed an alternative solution to robotic manipulation that employs pneumatic artificial muscles (PAMs) to generate desired joint torque and range of motion. The goal of this study is to determine the size and configuration of a robotic manipulator for battlefield casualty extraction. Following characterization and comparison of different-sized PAM actuators, a prototype of a PAM robotic manipulator arm was constructed. A quasi-static model for the PAM actuators is applied to system modeling. This model includes the Gaylord force from pressure effects on the braid, as well as a nonlinear Mooney-Rivlin term that considers the elastic energy of the bladder. Experiments are performed to measure joint torque over the manipulator range of motion. The model developed here is experimentally validated.

Mechanisms with dexterous manipulation capabilities are needed for many applications at the meso scale (1–5 mm diameter with micro scale features). Scaling down larger designs has proven to be impossible in many cases, and the manipulation forces produced by most existing meso scale designs are notably insufficient for intended applications. A review of articulating mechanisms and manipulator technologies developed within the last decade is presented, and the potential for these technologies to be implemented at the meso scale is explored. The utility of these systems is analyzed in terms of two main performance metrics: maximum range of motion and force application. Determining the miniaturization potential and performance capabilities of these mechanisms has highlighted necessary improvements for current systems and provided insight on which system types are most likely to be effective on the meso scale.

This paper presents forced-controlled nanomanipulation utilizing nano-robotic manipulator and nanomechanical cantilever. A three degree of freedom (3 DOF) nanomanipulator with revolute revolute prismatic (RRP) actuator structure, named here MM3A ® , can be utilized for a variety of nanomanipulation tasks. Previous publications of the authors present the mathematical modeling and robust control of manipulator’s tip using fused visual servoing and force sensor feedbacks. Due to lack of position and velocity feedbacks in MM3A ® nanomanipulator, a fused vision/force feedback robust controller has been recently designed by the authors. Previous publications of the authors present the optimal utilization of the visual servoing and force sensor feedbacks for use in the nanomanipulation tasks. More specifically, the visual servoing and force feedback structures are investigated through extensive simulations in order to reveal issues in practical implementation. In modeling the force sensing module of the designed fused feedback controller, previous publications of the authors present a closed-form distributed-parameters based modeling framework for piezoresistive Nanomechanical Cantilever (NMC)-based force sensors used in a variety of cantilever-based nanomanipulation actions. Current modeling practices call for a simple lumped-parameters framework rather than modeling the piezoresistive NMC itself. Due to the widespread applications of such NMCs in nanoscale force sensing or non-contact atomic force microscopy with nano-Newton to pico-Newton force measurement requirements, precise modeling of the piezoresistive microcantilevers is essential. Instead of the previously used lumped-parameters modeling, a distributed-parameters modeling framework is proposed and developed in previous publications of the authors to arrive at the most complete model of the piezoresistive NMC including tip-mass, tip-force and base movement considerations. Here, experimental results are presented to demonstrate the accuracy of the proposed distributed-parameters model when compared with the previously reported lumped-parameters modeling approach. It is shown that by utilizing the distributed-parameters model rather than lumped-parameters approach and by predicting the exact motion of each point on the NMC, the precision of the piezoresistive NMC’s model is significantly enhanced. Such novel modeling framework could pave the pathway towards nanomechanical cantilever-based manipulation and positioning as detailed in the second part.